Digital Camera Patent Abstract
Disclosed is a digital micromirror device (DMD) based projector
in which the position of a stylus with respect to a projected image
can be determined automatically. In one embodiment, the stylus includes
a detector capable of detecting illumination from a single pixel
and the plurality of pixels in the DMD array are sequentially energized
until a pixel reflects light to the stylus detector. Since the location
of that pixel is known, the position of the stylus adjacent that
pixel on the image is also known. In another embodiment, light is
emitted from the stylus and the DMD array is sequenced in order
to reflect light from the array to a photodetector. Again, when
a pixel is sequenced so as to reflect light to the detector, the
position of the stylus with respect to the image is related to the
image of the pixel with respect to the pixel's location in the array.
A further embodiment utilizes a general illumination source of the
screen with infrared radiation and a reflective stylus which reflects
the infrared radiation back to the DMD array. As before, sequencing
of the DMD array and detection of the pixel associated with the
reflected IR radiation provides an indication of the stylus location.
In a further embodiment, a DMD array is utilized to sequentially
address all of the pixels of a subject image thereby providing an
output of each sequenced pixel to a data storage device forming
a digital camera. Digital Camera Patent Claims
What is claimed is:
1. An apparatus for sensing position of a stylus relative to a
projected image where a digital micromirror device (DMD) array is
used for projecting said image upon a surface, said DMD array including
a plurality of controllable pixel mirrors, said image created by
directing light from a first light source onto said DMD array which
controllably reflects said directed light through an optical system
onto said surface, said image comprised of a plurality of sequentially
projected frame images where there is a finite time duration between
successive projected frame images, said apparatus comprising:
a second light source and a means for illuminating said surface
with light from said second light source;
said stylus including a reflector for reflecting said second light
source light from said surface back towards said surface;
energizing means for scanning by selectively energizing said plurality
of controllable pixel mirrors during said finite duration between
successive projected frame images;
a detecting means for detecting the presence of said reflected
second source light on said surface when reflected by at least one
of said controllable pixel mirrors; and
address means, responsive to said detecting means and said energizing
means, for providing a stylus position output when said detecting
means detects said reflected second source light from said surface
during said finite duration.
2. An apparatus for sensing position of a stylus in accordance
with claim 1, wherein at least a portion of light from said second
light source includes infrared radiation and said detecting means
is responsive to said infrared radiation.
3. An apparatus for sensing position of a stylus in accordance
with claim 1, wherein said energizing means comprises a DMD driver
for energizing said plurality of controllable pixel mirrors in a
predetermined pattern.
4. An apparatus for sensing position of a stylus in accordance
with claim 3, wherein said predetermined pattern is a sequential
raster scan.
5. An apparatus for sensing position of a stylus in accordance
with claim 3, wherein said predetermined pattern includes at least
one binary scan of a size less than the entire DMD array.
6. An apparatus for sensing position of a stylus in accordance
with claim 3, wherein said address means provides a stylus position
output to said DMD driver and said predetermined pattern begins
with an area inclusive of a previous stylus position.
7. An apparatus for sensing position of a stylus in accordance
with claim 1, further including a means for preventing light from
said first light source from reaching said DMD array during at least
a portion of said finite time duration.
8. An apparatus for sensing position of a stylus in accordance
with claim 7, wherein said energizing means controllably energizes
each of said pixel mirrors to an "ON" position in which
light from said first light source is directed towards said surface
and an "OFF" position in which light from said surface
is directed to said detecting means.
9. An apparatus for sensing position of a stylus in accordance
with claim 8, wherein said energizing means selectively energizes
said pixel mirrors by selectively moving said pixel mirrors to said
"OFF" position while moving non selectively energized
pixel mirrors to said "ON" position in an "ON-to-OFF"
scanning mode.
10. An apparatus for sensing position of a stylus in accordance
with claim 1, wherein said surface, upon which said image is projected,
is comprised of a front projection screen.
11. An apparatus for sensing position of a stylus in accordance
with claim 1, wherein said surface, upon which said image is projected,
is comprised of a rear projection screen.
12. An apparatus for sensing position of a stylus in accordance
with claim 1, wherein said projector includes a rotating color wheel
through which light from said first light source is projected.
13. An apparatus for sensing position of a stylus relative to a
projected image where a digital micromirror device (DMD) array is
used for projecting said image upon a surface, said DMD array including
a plurality of controllable pixel mirrors, said image created by
directing light from a first light source onto said DMD array which
controllably reflects said directed light through an optical system
onto said surface, said image comprised of a plurality of sequentially
projected frame images where there is a finite time duration between
successive projected frame images, said apparatus comprising:
a second light source for illuminating said surface with second
source light from said second light source;
said stylus including a reflector for reflecting said second source
light from said surface back towards said surface;
a DMD driver for scanning by selectively energizing said plurality
of controllable pixel mirrors during said finite duration between
successive projected frame images;
a detector for detecting the presence of said reflected second
source light on said surface when reflected by at least one of said
controllable pixel mirrors; and
X-Y position calculator, responsive to said detector and said DMD
driver, for providing a stylus position output when said detector
detects said reflected second source light from said surface during
said finite duration.
14. An apparatus for sensing position of a stylus in accordance
with claim 13, wherein at least a portion of light from said second
light source includes infrared radiation and said detector is responsive
to said infrared radiation.
15. An apparatus for sensing position of a stylus in accordance
with claim 13, wherein said DMD driver energizes said plurality
of controllable pixel mirrors in a predetermined pattern.
16. An apparatus for sensing position of a stylus in accordance
with claim 15, wherein said predetermined pattern is a sequential
raster scan.
17. An apparatus for sensing position of a stylus in accordance
with claim 15, wherein said predetermined pattern includes at least
one binary scan of a size less than the entire DMD array.
18. An apparatus for sensing position of a styflus in accordance
with claim 15, wherein said X-Y position calculator provides a stylus
position output to said DMD driver and said predetermined pattern
begins with an area inclusive of a previous stylus position.
19. An apparatus for sensing position of a stylus in accordance
with claim 13, further including an opaque segment for preventing
light from said first light source from reaching said DMD array
during at least a portion of said finite time duration.
20. An apparatus for sensing position of a stylus in accordance
with claim 19, wherein said DMD driver controllably energizes each
of said pixel mirrors to an "ON" position in which light
from said first light source is directed towards said surface and
an "OFF" position in which light from said surface is
directed to said detector.
21. An apparatus for sensing position of a stylus in accordance
with claim 20, wherein said DMD driver selectively energizes said
pixel mirrors by selectively moving said pixel mirrors to said "OFF"
position while moving non selectively energized pixel mirrors to
said "ON" position in an "ON-to-OFF" scanning
mode.
22. An apparatus for sensing position of a stylus in accordance
with claim 13, wherein said surface, upon which said image is projected,
is comprised of a front projection screen.
23. An apparatus for sensing position of a styflus in accordance
with claim 13, wherein said surface, upon which said image is projected,
is comprised of a rear projection screen.
24. An apparatus for sensing position of a stylus in accordance
with claim 13, wherein said projector includes a rotating color
wheel through which light from said first light source is projected.
Digital Camera Patent Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to stylus position sensing
and specifically relates to stylus position sensing in conjunction
with an image projected by a Digital Micromirror Device (DMD). The
present invention further relates to the use of a DMD to form a
digital camera.
2. Discussion of Prior Art
Over the last several years, Texas Instruments, Inc. has been testing
and developing a Digital Micromirror Device (DMD) which can be used
effectively in a projection arrangement to control projected light
with minimal losses. U.S. Pat. No. 4,680,579, issued Jul. 14, 1987
to Ott, entitled "Optical System for Projection Display Using
Spatial Light Modulator Device," U.S. Pat. No. 5,142,405, issued
Aug. 25, 1992 to Hornbeck, entitled "Bistable DMD Addressing
Circuit and Method" and U.S. Pat. No. 5,192,946, issued Mar.
9, 1993 to Thompson et al., entitled "Digitized Color Video
Display System" disclose the basic DMD concept, as well as
its application to projector systems, the disclosures of which are
herein incorporated by reference.
To simplify the discussion somewhat, Applicant encloses FIGS. 1-3
directed to a general overview of DMD operation when used with a
projector system. FIG. 1 illustrates the basic DMD pixel mirror
operation and it is noted that this operation would be the same
with respect to each of the multiplicity of pixel mirrors in a typical
DMD device. While DMDs have been created which have resolutions
of 2048.times.1152 pixels, only a single pixel mirror will be discussed
with respect to the prior art. Each pixel is in fact a miniature
mirror which can be electronically directed to an "ON"
and "OFF" position. Typically, the mirror is oriented
so that it moves through an angle of 2.theta..
With respect to the horizontal in FIG. 1, the DMD pixel mirror
10 can move from the "ON" position having an angle +.theta.
to an "OFF" position having an angle of -.theta.. Quite
clearly, it can be seen that with respect to the perpendicular with
respect to the screen, perpendiculars with respect to the micromirror
also move between +.theta. and -.theta. when in the "ON"
and "OFF" positions, respectively. The dotted line position
of the DMD mirror is its unpowered, undeflected position. This "relaxed"
position takes no part in the actual operation of the device. When
the DMD chip is powered, each pixel mirror is driven and latched
into either an "ON" or "OFF" position. In these
positions, as shown, the mirror is deflected and held against hard
stops 14, 16 for very precise angular control. While the deflection
angle can vary depending upon the needs and the particular device,
the angle .theta. is typically 10.degree. and thus, the mirror can
tilt + or -10.degree. about its " relaxed" position.
One characteristic of digital micromirrors is their ability to
move from an "ON" to an "OFF" position with
extreme rapidity. Typical mirror transit times from the "ON"
to the "OFF" position is on the order of 10 microseconds.
This permits the individual pixel to be turned on and off so as
to provide a variable duty cycle (the ratio of "ON" time
to total time) which provides a grey scale capability for projected
images.
FIGS. 2 and 3 illustrate the application of an array 30 of micromirrors
in a typical DMD projector with the pixel in the "ON"
and "OFF" position. FIG. 2 illustrates the DMD 10 being
held against the "ON" stop 14 in the conventional manner.
Light from an illuminator 18 is projected through a color wheel
20 towards the DMD. The light can be from any light source including
incandescent, halogen and other light sources, although a xenon
arc lamp is a particularly bright source of light providing a bright
projected image.
In a color projector embodiment, the light passes through a rotating
color wheel 20 which includes three primary color segments and can
optionally include a fourth area which permits passage of only infrared
light. While the color wheel 20 rotates at a high enough speed so
that the flickering of projected light is not perceived by the human
eye, the amount of light actually reflected from the DMD through
the projection lens 22 onto the screen 12 is controllable by modulating
the duty cycle of each DMD pixel mirror. If extremely bright light
is required for the particular color (the color is determined by
the rotational position of the color wheel), the DMD has a high
duty cycle, i.e., it is "ON" a great percentage of its
time. If very little of the particular color is needed, the duty
cycle is low and the DMD is "ON" only a small portion
of the time for that pixel.
It can be seen that the light projected towards the DMD is projected
at an angle 2.theta. with respect to a perpendicular to the screen
12. With the DMD in the "ON" position (where "ON"
is +.theta.), light reflected from the DMD will pass directly through
the projection lens 22 and strike the screen 12, and, in conjunction
with light reflected from other DMD pixels, forms a projected image.
FIG. 3 illustrates the same DMD pixel in the DMD projector except
that the pixel is in the "OFF" position and is held against
stop 16. It will be recalled that with respect to light being reflected
from a mirror, the angle of incidence is equal to the angle of reflection.
This can be seen in FIG. 2 where the incidence angle is .theta.
and thus the exit angle is .theta. (with respect to the pixel mirror).
When the pixel mirror rotates to the "OFF" position as
shown in FIG. 3, it can be seen that the angle of light from the
illuminator 18 is equal to 3.theta. and therefore, the exit angle
is also 3.theta. (both with respect to the DMD pixel mirrors perpendicular).
A light trap 24 is provided which absorbs light from the illuminator.
Accordingly, by modulating the duty cycle and the amount of time
spent in the "ON" and "OFF" positions, the time-wise
intensity of light projected through lens 22 and onto screen 12
can be modulated by each pixel mirror in the DMD projector.
By controlling the individual pixel mirrors in synchronization
with the rotational position of the color wheel, the red, blue and
green light from each rotation of the color wheel can be controlled
so that it is projected at the same spot on the screen (the spot
determined by which pixel is reflecting the light through lens 22).
The ability to control not only grey scale or average intensity,
but also to project the light through three primary colors permits
the mixing of the primary color light to form different and various
shades of color. By suitably driving all of the pixel mirrors in
a DMD projector individually, each of the pixels projected upon
the screen can be separately controlled as to color and intensity.
Accordingly, any visual image can be created on the screen.
The image to be projected can be a computer generated image, a
video in any one of the PAL, NTSC, SECAM or any other image format.
Thus, the DMD projector can serve to project full color images on
a remote screen in a manner similar to that of existing liquid crystal
display (LCD) projectors. However, where an LCD selectively absorbs
portions of the light transmitted therethrough, the display is heated
by the projector light requiring extensive cooling systems and cooling
schemes. Such cooling schemes are disclosed in detail in U.S. Pat.
No. 4,763,993, issued Aug. 16, 1988, entitled "Liquid Crystal
Display For Projection Systems" by Vogeley et al. and assigned
to the assignee of the present invention.
Even in its most transparent state, however, an LCD absorbs a significat
portion of light to be projected therethrough and thus the overall
brightness of the projected image suffers. Because the DMD projector
has generally greater than 90% of the light incident upon the DMD
device reflected therefrom, its images are significantly brighter
than a corresponding LCD projector given the same brightness illumination
source.
As discussed in U.S. Pat. No. 5,235,363, entitled "Method
and Apparatus for Interacting With a Computer Generated Projected
Image," issued Aug. 10, 1993 to Vogeley et al. and assigned
to the assignee of the present application, it is desirable to be
able to interact with a computer generated projected image especially
during presentations based upon the computer generated image. Disclosed
in the '363 patent (and also in the continuation-in-part of the
same title filed May 28, 1993 with Ser. No. 08/069,001 for which
the Issue Fee was paid on Mar. 20, 1995), various methods for determining
the position of a stylus or a stylus directed beam of light with
respect to the projected image are disclosed.
In each of the embodiments discussed in the '363 patent, a portion
of light reflected from the screen was diverted to, in a preferred
embodiment, a position sensing diode which determined the X and
Y positions of the point of light on the screen and thus the position
of the stylus relative to the image. While a similar device could
be utilized with a DMD projector, it is desirable to avoid the need
for a separate position sensing diode and the electronic circuitry
related thereto if at all possible.
SUMMARY OF THE INVENTION
Accordingly, in view of the above, it is an object of the present
invention to provide a method and apparatus for determining the
position of a stylus with respect to an image projected by a DMD
projector.
It is a still further object of the present invention to provide
a digital camera using the DMD array as an image scanning device.
The above and other objects are achieved in accordance with the
present invention by scanning, either sequentially or in binary
form, individual pixel mirrors in a DMD and utilizing the stylus
to indicate or sense the pixel which is activated closest to the
stylus position. The sequential or binary energization of pixel
mirrors occurs during a time duration between sequential frame images
and thus is not perceived by the human eye.
In a first embodiment, the stylus may include a photo detector.
The color wheel includes a segment for passing only infrared radiation.
This IR radiation is sequentially projected by the DMD pixel mirrors
to the screen. The timing of the receipt of radiation at the stylus
and the timing of the DMD pixels which have been energized, will
indicate which of the pixels (in the sequential scan) or which blocks
of pixels (in the binary scan) are responsible for the IR, thereby
providing the pixel location of the stylus.
In a second embodiment, the stylus merely projects a beam of light
during a blanking phase between two frames of the projected image,
each of the pixels is sequentially or binarily energized (either
"ON" to "OFF" or "OFF" to "ON").
A light sensitive detector (preferably a phototransistor) is provided
at a focal point of the projection optics such that, when light
emitted from the stylus is reflected back through the DMD pixel
located closest to the light, the detector provides an output signal
indicative of the light. Because the timing of when the light is
perceived by the detector and when each pixel is energized (either
in sequential or binary form) is known, the precise location of
the light can be determined with a high degree of resolution.
A further embodiment provides a general illumination of the screen
with IR energy from a general source. Sequential scanning of the
DMD pixel mirrors in either sequential or binary form results in
IR light being reflected, by means of a reflector located in the
stylus, back through the projection optics to a IR detector in the
device. Again, the location of the pixel or block of pixels which
results in the detection of IR energy provides an indication of
the location of the mirror in the stylus relative to the projected
image.
A further embodiment utilizes the scanning ability of the DMD array
to scan an image into a digital storage device. The image is focused
on the DMD array which is sequentially scanned. As each pixel mirror
is energized, the light from that mirror is sensed by a detector
and the output passed to a digital storage location. After a complete
scan, the complete digital image would be present in the storage
medium. For color images, scanning through a color wheel, with one
scan for each color, will provide a digital color image.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view illustrating known basic DMD pixel operation;
FIG. 2 is a side view illustrating a known DMD projector operation
with the pixel in an "ON" condition;
FIG. 3 is a side view illustrating a known DMD projector operation
with the pixel in an "OFF" condition;
FIG. 4 is a perspective view of a DMD projector and a detector
stylus embodiment;
FIG. 5 is a block diagram of the electronic circuitry for providing
stylus position output for the stylus detector embodiment;
FIGS. 6(a) through 6(c) illustrate a sequential DMD pixel mirror
scan;
FIGS. 7(a) through 7(c) illustrate a binary DMD pixel mirror scan;
FIG. 8 is a perspective view of a DMD projector operating in conjunction
with an emitter stylus;
FIG. 9 is a circuit block diagram of the operation of the emitter
stylus embodiment;
FIG. 10 is a side view of one embodiment of an emitting stylus
operating in the "OFF-to-ON" position scanning mode;
FIG. 11 is a side view of one embodiment of an emitting stylus
operating in the "ON-to-OFF" scanning mode;
FIG. 12 is a side view illustrating the operation of the reflective
stylus embodiment of the present invention;
FIG. 13 is a perspective view of the operation of the reflector
stylus embodiment;
FIG. 14 is a side view illustrating a simplified known DMD projector;
FIG. 15 is a side view of a digital camera utilizing a DMD device
in accordance with another embodiment of the present invention;
FIG. 16 is a perspective view of the digital cameral embodiment
of the present invention; and
FIGS. 17(a) and 17(b) are block diagrams of generic and specific
embodiments of the digital camera according to the present invention.
DETAILED DISCUSSION OF PREFERRED EMBODIMENTS
The following detailed description refers to four distinct embodiments
of Applicant's invention where, among the various embodiments, the
same structures are labelled in the same fashion so as to provide
continuity of understanding among the several views.
Detector Stylus Embodiment
FIG. 4 illustrates in a perspective view the component arrangement
for a color DMD projector with a stylus having a detector which
is responsive to infrared radiation. Illumination source 18 provides
radiation which is focused by lens 26 upon rotating color wheel
20. In addition to red, green and blue segments, color wheel 20
has a segment 21 which provides an infrared radiation pass filter
permitting only infrared radiation to pass through the color wheel
and onto the lens 28. The DMD array 30 comprises a plurality of
individual DMD pixel mirrors as previously discussed.
The DMD array 30 is positioned such that visible light or infrared
radiation from lens 28 is reflected through lens 22 onto screen
12 when the pixel mirrors are in their "energized state"
(this may be the "ON" or "OFF" position, depending
on the orientation). The "energized state" is defined
as the position in which the micromirrors reflect the light through
the projection lens and onto screen 12. DMD driver 32 provides the
appropriate signals to modulate the energization and de-energization
of each of the pixel mirrors contained in the DMD array 30, thereby
causing the desired image to be projected onto screen 12.
The detector stylus 34 includes an aperture 36 for admission of
IR infrared energy, a photodetector 38 for detecting the presence
of IR energy entering through aperture 36 and a photodetector output
line which in one embodiment is a cable 40 and in another embodiment
is a "wireless" relay system such as an IR or RF link.
Accordingly, whenever IR energy is sensed by the photodetector,
an output is provided on the cable 40. Accordingly, while the apparatus
shown in FIG. 4 will project color images on screen 12 (which may
be a front projection or a rear projection screen as desired), the
stylus is responsive to infrared radiation being perceived at a
point toward which the stylus is directed.
The image which is projected on screen 12 is generally comprised
of a series of frames which are separated by a finite time duration.
During each frame, of course, the individual DMD pixel mirrors 10
are modulated at their appropriate duty cycle with red, green and
blue light projected thereon so as to provide the appropriate mix
of colors and intensities at the corresponding pixel location on
screen 12 to "paint" the desired color at that spot. The
total of all of the DMD pixel mirrors is to paint an image on the
screen. Each screen or frame image is separated from a following
frame image by a finite time duration and it is during this duration
that stylus positioning information is determined.
There are numerous different sequencing schemes which could be
applied to the individual DMD pixel mirrors 10 in the DMD array
30 which would work, although two preferred embodiments are disclosed
in this application. Attention is directed to FIGS. 6(a)-6(c) which,
in a simplified form, illustrate the operation of the sequential
scan. At the beginning of the time duration between images, and
during the time period in which infrared radiation is directed towards
the DMD array 30, each of the pixels is sequentially energized,
i.e., moved to the "energized" position (either "ON"
or "OFF") so that IR radiation is reflected through projection
lens 22 and onto screen 12.
In FIG. 6(a), the stylus 34 is shown to be looking at a spot which
is identified as pixel C-3. The pixel scan begins with pixel mirror
A-1 and this pixel is energized and thereby reflects infrared radiation
to the location of pixel A-1 on screen 12. Since the stylus is not
"looking" at pixel A-1, no output is provided from the
stylus. The pixel energization sequence continues in any desired
fashion (here shown in a linear progression across each row and
then moving down to the next row in sequence). Only when pixel location
C-3 is reached does the stylus provide an output since it "sees"
the IR illumination at this pixel. Because the time of each pixels
energization in the pixel sequence, whether linear or random or
some other sequence, is known and the precise time that the stylus
"sees" IR radiation is known, the result is the pixel
location of the stylus position is known. As long as the pixel scanning
sequence is completed during the duration between projected frames,
a highly accurate, high speed update of stylus position can be obtained
in this fashion.
One drawback of the sequencing method shown in FIGS. 6(a)-6(c)
is that the scan must go through each and every pixel requiring
substantial scanning and a relatively long duration. An improved
scan which requires less time is shown in FIGS. 7(a)-7(c). Here,
a "binary" scan energizes a whole series of pixel mirrors
at a time. In FIG. 7(a), pixel locations 4-6 in columns A-D are
all energized at once. If the stylus detects no infrared radiation,
no further scanning of these pixels is necessary (because the stylus
position is not within this block) and the number of pixels to be
scanned in the future has been reduced by 50%.
Since with the single step it has been determined that the stylus
position is located within columns 1-3 of rows A-D, half of the
remaining area is energized. The energization of rows A and B, columns
1-3, is shown in FIG. 7(b). Again, because stylus does not "see"
any IR radiation, the area in which the stylus position is located
has been narrowed down to either row C or D and columns 1-3. At
this point, a sequential scan in row C, beginning with column 1,
will find the stylus position at C-3 after three energizations.
Thus, in order to find the stylus position at FIG. 7(c), two binary
operations (one shown in FIG. 7(a) and one shown in FIG. 7(b)),
and three sequential operation (the third of which is shown in FIG.
7(c)), are necessary to determine the position. Accordingly, only
time necessary for a total of five energizations will locate the
C-3 pixel utilizing the binary method shown in FIG. 7. It is noted
that the sequential method in FIG. 6 will require time for 15 separate
energizations (row A, columns 1-6, row B, columns 1-6 and row C,
columns 1-3). Accordingly, it can be seen that with a binary search
sequence, the stylus position can be determined with fewer pixel
energizations.
FIG. 5 is a block diagram of a circuit for providing an X-Y stylus
position output with the embodiment disclosed in FIG. 4 except that
a wireless IR link has been used. During the finite time duration
between successive projected frame images, DMD driver 32 applies
any desired search sequence (in a preferred embodiment, a binary
search sequence) to the DMD array 30. At the same time, it applies
the search sequence information to X-Y position block 42. Position
block 42 may be any one of a number of structures in which position
addresses are sequentially energized by the DMD driver. When stylus
34 senses IR radiation, it provides the photodetector output to
the IR transmitter 41 to the IR receiver 43. The IR receiver 43
provides the X-Y position block 42 with the indication that the
stylus has received the radiation from the screen. The X-Y stylus
position output which indicates the location of the specific DMD
pixel mirror which is being energized at that time by the DMD driver
32.
Where the energization sequence is a binary sequence as discussed
in conjunction with FIG. 7, a position output would not be provided
until the individual pixel sequencing has identified a single pixel
which controls the radiation perceived by the stylus. Furthermore,
in a preferred embodiment, position feedback 44 (as indicated in
phantom line in FIG. 5) may be used to direct the DMD driver to
search first in the area adjacent the last known stylus position.
For example, where, in FIG. 7(c) the stylus position was found to
be within the quadrant of rows C and D, columns 1-3, the first energization
sequence might start with that quadrant, thereby further expediting
the search sequence.
Of course, the detector stylus embodiment could detect any frequency
of radiation and, thus, IR radiation is not necessarily required.
In fact, as long as the radiation were not high contrast with the
background of the screen or its duration during scan so brief as
to cause not perceptible flicker, any color could be utilized. Further,
the radiation could be pulse code modulated by the individual pixel
mirror with the detector 38 and any associated amplification circuity
inclusive of a filter responsive to the specific pulse code modulation
so as to raise the signal-to-noise ratio. Indeed, different types
of pulse code modulation or different frequencies or combinations
of the two could be utilized such that the system is responsive
to multiple stylus locations or functions, e.g., erase, draw red,
draw green, etc.
Emitter Stylus Embodiment
FIG. 8 illustrates a further embodiment of the present invention
in which the stylus is not required to provide any signal back to
the X-Y position block. FIG. 8 illustrates a similar system as that
shown in FIG. 4 with the DMD driver and projection optics almost
identical. It is noted that while the color wheel 20 does not need
to include an IR segment, it does include an opaque segment 54.
Stylus 46 is equipped with a light source which, in a preferred
embodiment, could be a light emitting diode or a small hand-held
laser. Again, while the device is shown with a back projection system,
it is equally applicable to front projector systems.
The stylus 46 includes the light emitting diode and aperture 36
through which light passes. The DMD array 30 is located in such
a position that light from lens 28 directed at the pixel mirrors
in the DMD array 30 is reflected when an individual pixel mirror
is energized so as to pass through projection lens 22, creating
the desired image on screen 12. As will later be seen (in the discussion
relating to FIG. 11), light coming from the screen (from the light
emitting stylus) passes through the projection lens 22 is reflected
from the appropriate pixel mirror in the DMD array 30 towards lens
50 and from there to photodetector 52. Light from illumination source
18 is interrupted when opaque segment 54 on color wheel 20 is encountered.
In the embodiment shown in FIG. 8, the light which normally illuminates
screen 12, especially when a DMD device is in the energized position,
is interrupted by opaque segment 54. However, it can be seen that
any light on the screen (caused by the light emitting stylus) would
be fed back through projection lens 22, reflected off of the energized
pixels in the DMD array and directed back towards the lens 28 and
color wheel 20. However, de-energized pixels would reflect the light
in a different direction and in this instance, towards lens 50 and
photodetector 52. Accordingly, a sequential or binary or other search
system in the embodiment shown in FIG. 8 would maintain pixels in
the "ON" position except for each pixel or block of pixels
which are being scanned and they would be turned to the "OFF"
position for the scan. Therefore, using the search sequence in FIGS.
6 and 7, the dark squares would indicate pixels which have been
turned "OFF."
The illustration of this embodiment in which scanned pixels are
turned from "ON" to "OFF" is shown in FIG. 11
where the light from illumination source 18 during energization
would pass through color wheel 20, be reflected from the "ON"
pixels and be projected through lens 22 onto screen 12. However,
the pixel mirror 10 is shown in the "OFF" position where
light from the screen 12 created by the light emitting stylus 46
passes through the projection lens 22 and is reflected at a further
angle through the lens 50 to the photodetector 52. The use of opaque
segment 54 prevents light from the illumination source 18 from illuminating
the screen 12 during the period in which the search for the light
emitting stylus pixel location is being conducted so as to improve
contrast. The opaque segment 54 may not be necessary if the stylus
light is of a particular frequency or wavelength (as in a laser)
or is pulse code modulated and the output of photodetector 52 is
filtered in accordance with the pulse code modulation (the pulse
code modulation significantly increases the signal-to-noise ratio
and may eliminate the need for the opaque segment 54).
FIG. 9 illustrates in block diagram form the operation of the light
emitting stylus embodiment. As discussed previously with either
an energized or de-energized pixel mirror (depending upon whether
it is the "ON-to-OFF or "OFF-to-ON" position scanning
mode) is deflected from the DMD array to the photodetector 52 which,
upon receiving the light from the stylus, provides an output to
the X-Y position block 42. Similarly, the DMD driver provides an
indication of the energized (or deenergized) pixels on the DMD array
30 to the X-Y position block 42 such that when an energized (or
deenergized) pixel results in an output from photodetector 52, that
pixel location is provided as the X/Y stylus position output. Again,
either a sequential, binary or other search game can be utilized
and where desirable, a last position feedback loop 44 to the DMD
driver can initiate the search in the immediate location of the
last stylus position.
As discussed above, it was seen in FIG. 11 that detection was possible
by scanning the pixel mirrors in the "OFF" position. However,
it may be desirable to scan pixels in the "ON" position
and a slight modification of the device will be necessary. Because
in the "energized" position, by definition, illuminating
light is directed through the projection lens to the screen 12,
light from that same position on screen 12 will be directed back
through the projection optics towards the illumination source. Because
the light emitted from the stylus is substantially less than the
light from the illumination source, it is not only necessary to
block the light from the illumination source as with the opaque
segment 54, but also to reflect the stylus light to a suitable photodetector.
This is accomplished by the location of a suitable reflector 56
on the DMD mirror array side of the color wheel which may be conveniently
located over the opaque segment 54.
Reflector 56 would serve to reflect any light from the light emitting
stylus and reflected from the "ON" position (energized)
of the DMD pixel mirror 10 back along the optical axis towards the
illumination source 18. However, the reflector 56 on the color wheel
will reflect this light from the stylus to detector 52. Quite obviously,
with the DMD pixel mirror 10 in the "OFF" position, light
from the emitting stylus is not reflected back towards the color
wheel and therefore would not impinge upon detector 52. Accordingly,
in the scanning sequence to determine the stylus position, pixel
mirrors would normally be in the "OFF" position and would
either be sequentially "energized" or energized in binary
or some other energizing sequence so as to provide the previously
discussed scan.
Therefore, as shown in FIGS. 10 and 11, the DMD projector with
a light emitting stylus could be utilized in either an "ON-to-OFF"
or "OFF-to-ON" position scanning mode.
Reflector Stylus Embodiment
FIGS. 12 and 13 are directed towards a further and perhaps more
general low-cost stylus embodiment in which a mirror 56 is located
in the reflector stylus 58. The mirror 56 is located close to aperture
36 so that radiation into the aperture is reflected back towards
the screen 12. An IR illumination source 60 illuminates the area
of the screen with general infrared radiation as shown in FIG. 13.
The device operates in a manner similar to the FIG. 11 embodiment
in that when DMD mirror 10 is "deenergized" to the "OFF"
position, except that general IR illumination of the screen takes
place. IR light directed towards the screen is reflected by a mirror
56 in reflector stylus 58 back through projection lens 22. It is
reflected from the "OFF" position DMD mirror, through
lens 50 and is detected by detector 52.
Thus, the scan of DMD pixel mirrors is accomplished by energizing
all other mirrors and turning to the "OFF" position, those
mirrors which are being sequenced. Because screen 12 does not generally
reflect the IR illumination, no infrared radiation will be received
by the detector 52 until the pixel closest to the reflective stylus
is de-energized to the "OFF" position at which point the
detector will register the receipt of IR radiation. Again, since
it would be desirable to block light from the illumination source
18 during the period of pixel sequencing, opaque segment 54 on color
wheel 20 would be utilized. Also, to improve signal-to-noise ratio,
the general IR illumination of the screen could be pulse code modulated
or of a particular frequency or a combination of the two which results
in a higher signal-to-noise ratio at detector 52.
In view of the above, three specific embodiments of stylus position
locating systems are disclosed which would allow an operator to
communicate with a computer which is disclosed in U.S. Pat. No.
5,235,363, entitled "Method and Apparatus for Interacting With
a Computer Generated Projected Image," issued Aug. 10, 1993
to Vogeley et al. However, the present inventors have also found
that many of the structures utilized in the stylus detection systems
can also be used in conjunction with the DMD array as a digital
camera. Although the systems described herein utilize a color wheel,
one of ordinary skill in this art will appreciate that the inventions
could easily be incorporated into multiple channel systems, e.g.
a three channel display system. In such an application, during a
suitable interval between display frames, at least one of the three
channels (or a fourth independent channel dedicated to stylus position
sensing only) would be used to provide position sensing using any
of the embodiments previously described.
Digital Camera Embodiment
A brief review of the conventional requirements for a DMD array
projector can be had by reference to FIG. 14. It can be seen that
color wheel 20 breaks up the generally white light from illumination
source 18 and through appropriate lenses (not shown) applies the
light evenly to each of the multitude of DMD pixel mirrors 10 which
comprises the DMD array. Depending upon the desired intensity and
color of the light, the individual array is modulated and the resultant
light transmitted through projection lens 22 and is visible on screen
12. The light from the multitude of pixel mirrors forms the image
on screen 12 (which can be a front or rear projection screen). The
pixel mirrors are modulated between their "ON" and "OFF"
positions so that light or no light is transmitted back through
the projection lens 22.
Applicants have discovered that similar structures can be used
to create in effect a digital camera and the basic embodiment is
shown in FIG. 15. Light from the camera subject 62 is transmitted
through camera lens 64 until it reaches the DMD pixel mirrors of
the DMD array. Normally the mirrors are in the "OFF" position
where light is reflected to the light absorber 66 which may be a
flat black surface or other light absorbent material. Pixel by pixel,
the mirrors are briefly turned on and then off again so that the
light passes through color wheel 20 to detector 52 (the desirable
camera optics have been omitted for clarity of illustration). A
complete scan of each DMD pixel mirror in the DMD array for each
red, green and blue segment on the color wheel will provide complete
digital information as to the color and intensity at each pixel,
thereby clearly characterizing the image or camera subject 62.
FIG. 16 is a perspective view, perhaps more clearly illustrating
the light path from camera subject 62 through the camera lens which
is then directed on the DMD array 30. DMD driver 32 sequentially,
in a predetermined order, energizes each of the pixel mirrors contained
in the DMD array 30. Because only one pixel mirror is energized
at a time, only the light from that single pixel is transmitted
through lens 28 and through the red segment of the color wheel and
is focused by lens 50 on detector 52. Thus, detector 52 will provide
an output equal to the intensity of the red light component of light
reflected from that individual pixel mirror. As the color wheel
20 rotates, while light is focused through the red segment, each
of the pixel mirrors is sequenced such that the detector 52 provides
an output corresponding to the red light component of the entire
camera subject 62.
Similarly, the detector provides an output for the blue and green
components as the color wheel rotates to those particular segments.
In one rotation of the color wheel (which may be rotating at up
to a thousand revolutions per second), the output from detector
52 characterizes all information to digitally reproduce the camera
subject 62.
FIG. 17(a) shows a general digital camera block diagram with DMD
array 30 which is sequenced in a predetermined scan, as previously
discussed, by the DMD driver 32. The sequencing information is provided
to image storage and processing block 68 to enable the light readings
taken by photosensor 52 to be placed in the address appropriate
for the pixel which has been energized by the driver. Although a
black and white embodiment is shown, a color wheel position sensor
70 is shown in dotted line (or other synchronization device to ensure
that sequencing information is synchronized with the colors which
are being deflected onto the photosensor) which could be utilized
if a color image is to be stored. This position sensing or synchronization
ensures that each of the primary colors enables the DMD driver to
sequence the DMD array and that each of the illumination detected
for each of the color wheel colors is recorded by photosensor 52
is stored in the appropriate color for that pixel in the image storage
and processing block 68.
Whenever display of the image is desired, the pixel addresses are
interrogated and the output of each of the three colors in each
pixel can be provided to an image display 72. FIG. 17(b) shows a
preferred embodiment of a black and white digital camera in which
the DMD driver provides an output not only to DMD array 30 but also
to random access memory (RAM) 74. The output of light reflected
from the individual pixel mirrors is received by photosensor 52
and the output provided to analog to digital converter 76. The digital
output from converter 76 is applied to the RAM 74 at the particular
storage locations identified by the DMD driver 32. In this way,
a complete black and white image can be stored in RAM 74 and is
capable of being read out by merely interrogating each pixel location
for the light level of the image at that location. With the addition
of the color wheel position sensor 70 discussed in conjunction with
FIG. 17(a) (or other suitable synchronization) and suitable outputs
to the DMD driver 32 and to RAM 74, a color image can be stored,
although this would require approximately three times the storage
capacity in the random access memory.
Although for recording color images a color wheel has been shown,
one could also utilize three separate detectors using red, green
and blue filters or a combination of red, green and blue sensitive
photodiodes for recording color data simultaneously and providing
these three channels of color data to the image recording system.
Because of the similarity between the digital camera shown in FIG.
16 and the color projector equipped with a light emitting stylus
in FIG. 8, both the camera and projector with stylus devices could
be included in a single device. Operating as a projector, the stylus
function would be invaluable for an operator to interrelate with
a computer (in much the same fashion as a mouse is used with a conventional
personal computer) generating the projected image.
As a camera, the illumination light could be turned off or temporarily
blocked, allowing the machine to record any remaining image or different
images projected on the screen. While two separate color wheels
could be used, one for the stylus projection combination and the
other for the digital camera embodiment, an improved device would
locate a single color wheel in a location so that it can serve either
the projector or camera function. Furthermore, the digital camera
is not limited to simple storage and retrieval. It is suitable as
a sensor for various additional functions such as position sensing,
spatial measurement, temperature profilometry (measurement of temperature
profiles), etc.
While many modifications of the above devices will be obvious to
those or ordinary skill in the art in conjunction with this disclosure,
it is noted that the particulars of the DMD array are not critical.
The DMD "ON" and "OFF" mirror angles need not
be fixed at 10.degree. and do not even need to be the same angle.
The screen might be inclined with respect to the DMD chip and/or
mirrors as in normal projector operations producing keystoning and
requiring some keystoning correction. The chip and the projection
lens geometry could be made adjustable for keystone correction.
The various light paths could be bent or deflected by the use of
prisms, mirrors, etc. for optimum packaging purposes. As noted earlier,
either front or rear projection modes are possible and each of the
styluses could be used in either mode.
The stylus emitting radiation could be visible infrared laser whether
modulated or unmodulated and whether pulse code modulated or not.
The wireless link to the stylus having a detector built in could
be either infrared radiation or radio frequency as desired.
While the invention has been described in connection with what
is presently considered to be the most practical and preferred embodiment,
it is to be understood that the invention is not to be limited to
the disclosed embodiment, but on the contrary, is intended to cover
various modifications and equivalent arrangements included within
the spirit and scope of the appended claims. Accordingly, the presently
disclosed inventions are not limited by the present disclosure and
are limited only by the claims attached hereto.
|