Digital Camera Patent Abstract
A digital camera includes a camera main body, an image sensing unit
which is detachably connected to the camera main body and electrically
connectable to the camera main body via a cable in a state that
the image sensing unit is detached from the camera main body. The
image sensing unit includes a taking lens, an image pick-up element
for picking up an object image focused by the taking lens, and an
A/D converter which converts an analog image signal outputted from
the image pick-up element into a digital image signal. The camera
main body includes an image processor for subjecting a prescribed
image processing to the digital image signal outputted from the
A/D converter. Digital Camera Patent Claims
What is claimed is:
1. A digital camera, comprising: a camera main body; and an image
sensing unit which is detachably connected to said camera main body
and electrically connectable to said camera main body via a cable
in a state that said image sensing unit is detached from said camera
main body, wherein said image sensing unit includes: a taking lens;
an image pick-up element for picking up an object image focused
by said taking lens; and an A/D converter which converts an analog
image signal outputted from said image pick-up element into a digital
image signal, and wherein said camera main body includes: a latch
circuit for restoring a waveform of the digital image signal sent
from said A/D converter; and an image processor for subjecting a
prescribed image processing to the restored digital image signal.
2. The digital camera according to claim 1, further comprising
a detector for detecting a type of said cable connected to said
camera main body.
3. The digital camera according to claim 2, wherein a timing for
latching the digital image signal by said latching circuit is changed
depending on a detected result of said detector.
4. The digital camera according to claim 3, wherein the type of
said cable includes information on a length of said cable.
5. The digital camera according to claim 1, further comprising
a judge processing portion for judging a connection status of said
camera main body and said image sensing unit.
6. The digital camera according to claim 5, wherein a timing for
latching the digital signal by said latching circuit is changed
depending on a result of said judge processing portion.
7. The digital camera according to claim 1, further comprising
a cable for connecting said image sensing unit and said camera main
body.
8. The digital camera according to claim 7, wherein said cable
is provided with a terminal for representing a type of said cable
at a connecting portion to be connected to said camera main body.
9. The digital camera according to claim 8, wherein said camera
main body includes a judging processing portion for judging a connecting
status of a connecting portion of said camera main body.
10. A camera main body for use in a digital camera system including
said camera main body and an image sensing unit which is detachably
connected to said camera main body and electrically connectable
to said camera main body via a cable in a state that said image
sensing unit is detached from said camera main body, said camera
main body, comprising: a connecting portion to which an image signal
digitalized at said image sensing unit and outputted therefrom is
inputted; a latch circuit for latching the digital image signal
supplied through said connecting portion, the latch circuit restoring
a waveform of the digital image signal; a signal processor for subjecting
a prescribed image processing to the digitalized image signal from
said latch circuit; and a controller which detects which of said
image sensing unit and said cable is connected to said connecting
portion and changes a latch timing of said latch circuit depending
on a result detected by said controller.
11. The camera main body according to claim 10, wherein said controller
detects which type of cable from a plurality of cables is connected
to said connecting portion.
12. The camera main body according to claim 11, wherein the type
of cable includes information on a length of said cable.
13. A method for processing a signal in a digital camera system
including a camera main body and an image sensing unit which is
detachably connected to the camera main body and electrically connectable
to the camera main body via a cable in a state that the image sensing
unit is detached from the camera main body, the method including
the steps of: judging whether the image sensing unit is connected
to the camera main body or the cable is connected to the camera
main body; changing a latch timing of a latch circuit depending
on a judgement, the latch circuit latching a digital image signal
which is outputted from the image sensing unit and inputted to the
camera main body and restoring a waveform of the digital image signal
outputted from the image sensing unit.
14. The method according to claim 13, wherein it is judged which
type of cable from a plurality of cables is connected to said camera
main body.
15. The method according to claim 14, wherein the type of cable
includes information on a length of said cable.
Digital Camera Patent Description
The present invention claims a priority based on Japanese Patent
Application No. H10-214486, the content of which is incorporated
hereinto by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a digital camera, a camera main body
in a digital camera system and a method for processing a signal.
2. Description of the Related Art
There is a conventional digital camera which comprises an image
sensing unit including a taking lens and an image pick-up element
which converts an object image focused by the taking lens into an
image signal and a camera main body including an image processing
portion by which the image signal is subjected to a prescribed image
processing.
As the aforementioned image pick-up element, a CCD (charged coupled
device) as a photoelectric conversion element is generally used.
When the optical image of the object is focused onto the surface
of the CCD by the taking lens, the object image is photoelectrically
converted into an analog image signal by the CCD. The generated
analog image signal is converted into a digital image signal, and
then the digital image signal is subjected to a predetermined image
processing. Thus, image data can be obtained.
In a conventional digital camera of this kind, it is known that
the image sensing unit including the taking lens, the image pick-up
element and an analog circuit for the image pick-up element, is
detachably connected to the camera main body and that the image
sensing unit can be electrically connected to the camera main body
by way of a cable in a case that the image sensing unit is detached
from the camera main body. For example, the Japanese Patent Laid-open
Publication No. H10-79874 discloses that the image sensing unit
is detachably connected to the camera main body and that the phase
delay of the image signal occurred in a case where the image sensing
unit is connected to the camera main body via the cable is corrected.
In the aforementioned conventional digital camera, the A/D converter
which converts the analog image signal generated by the CCD into
the digital image signal is provided in the camera main body and
the analog image signal outputted from the image sensing unit is
transmitted to the camera main body as it is via the cable so as
to be subjected to the A/D conversion at the camera main body. As
a result, the image signal may be influenced by noise when the image
signal is transmitted to the camera main body. Thus, the practical
length of the cable will be limited to about 1 meter.
In the meantime, in order to transmit the analog signal through
a cable of long length, it may be considered to raise the gain when
amplifying the analog image signal in the image sensing unit. However,
in this case, there will be the drawback that noise will be increased
at the image sensing unit side and the power consumption rate of
the batteries as a power source will be increased.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide
a digital camera for practical use which can obtain an appropriate
image signal without being influenced by noise even in a case where
an image sensing unit is connected to a camera main body via a cable
and is low in energy consumption rate.
Another object of the present invention is to provide a camera
main body suitable for use in a digital camera system in which an
image sensing unit and the camera main body are connected via a
cable.
Still another object of the present invention is to provide a method
for processing a signal which is applicable to the aforementioned
digital camera system.
According to one aspect of the present invention, a digital camera
includes a camera main body, an image sensing unit which is detachably
connected to the camera main body and electrically connectable to
the camera main body via a cable in a state that the image sensing
unit is detached from the camera main body. The image sensing unit
includes a taking lens, an image pick-up element for picking up
an object image focused by the taking lens, and an A/D converter
which converts an analog image signal outputted from the image pick-up
element into a digital image signal. The camera main body includes
an image processing apparatus for subjecting the digital image signal
outputted from the A/D converter to a prescribed image processing.
With this digital camera, since the image sensing unit including
the taking lens and the image pick-up element is detachably connected
to the camera main body and they are connectable with each other
via the cable in a detached state, a photographing can be performed
at any desired angles. In addition, since the A/D converter is provided
in the image sensing unit, the converted digital image signal is
transmitted to the camera main body. However, since the digital
signal is not easily affected by noise, an appropriate image signal
can be obtained at the camera main body side even if the image sensing
unit is connected to the camera main body via the cable.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features, and advantages of the present
invention will be apparent from the following detailed description
of the preferred embodiments with reference to the attached drawings,
wherein:
FIG. 1 is a front view of the digital camera according to an embodiment
of the present invention;
FIG. 2 is a top view of the image sensing unit of the digital camera
shown in FIG. 1;
FIG. 3 is a rear view of the digital camera shown in FIG. 1;
FIG. 4 is a perspective view of the camera main body with the connecting
plate shown in FIG. 1;
FIG. 5 is a perspective view of the connecting structure of the
image sensing unit to which the connecting plate is connected;
FIG. 6 is a cross-sectional view of the locking mechanism of the
image sensing unit for locking the connecting plate;
FIG. 7 is a perspective view of the connecting cable for connecting
the image sensing unit and the camera main body;
FIGS. 8A to 8C are explanatory views showing variations for connecting
the image sensing unit and the camera main body;
FIG. 9 is a bottom view of the digital camera shown in FIG. 1;
FIG. 10 is a block diagram showing the control system of the digital
camera shown in FIG. 1;
FIG. 11 illustrates the data-storage structure of the memory card;
FIG. 12 illustrates the connecting state of the cable;
FIG. 13A to 13D illustrates the connecting state of the judging
terminal for judging the connecting state of the image sensing unit
and the camera main body; and
FIG. 14 is a timing chart of the timing control when the image
sensing unit is connected to the camera main body via the cable.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The digital camera according to this embodiment will be explained
with reference to FIGS. 1 to 3.
As shown in FIG. 1, the digital camera 1 comprises a box-shaped
camera main body 2 and a rectangular image sensing unit 3. The image
sensing unit 3 is detachably connected to the right side of the
camera main body 2 in the front view shown in FIG. 1 such that the
image sensing unit 3 is rotatable within a plane parallel to the
right side of the camera main body 2.
As shown in FIG. 2, the image sensing unit 3 has an elongated image
sensing unit main body 3A having approximately the same length as
the height of the camera main body 2 and approximately the same
depth as the depth of the camera main body 2. A connecting portion
3B for connecting the image sensing unit main body 3A to the camera
main body 2 is protruded outwardly from one side of the image sensing
unit main body 3A. Since the image sen sing unit main body 3A has
an elongated rectangular parallelepiped shape and is able to be
positioned along the side of the camera main body 2 when not in
use, it is possible to employ a zoom lense 301 having a long length
along the optical-axis direction without increasing the depth of
the digital camera 1.
A connecting mechanism of the connecting portion 3B for connecting
the image sensing unit 3 to the camera main body 2 will be explained
later.
As shown in FIG. 2, a macrozoom lens 301 is provided in the image
sensing unit main body 3A. An image pick-up circuit 302 including
a CCD colour area sensor 303 is located at an appropriate position
behind the macrozoom lens 301. A light adjusting circuit 304 having
a light adjusting sensor 305 for receiving flash light reflected
from the object is provided at an appropriate position in the image
sensing unit 3. As shown in FIG. 3, the image sensing unit 3 is
provided with a lock-releasing lever 307 for detaching the image
sensing unit 3 from the camera main body 2.
As shown in FIGS. 1 to 3, the camera main body 2 has a display
10 or an LCD (Liquid Crystal Display), a slot 17 for receiving a
memory card 8, and a connection terminal 13 for connecting the digital
camera 1 to a personal computer. The image signal taken by the image
sensing unit 3 is subjected to a prescribed image processing in
the camera main body 2. The processed image is displayed on the
LCD display 10, recorded in the memory card 8 and/or transferred
to the personal computer.
Next, a connecting mechanism of a connecting portion 3B for connecting
the image sensing unit 3 to the camera main body 2 will be explained.
As shown in FIG. 4, a connection plate 23 for detachably connecting
the image sensing unit 3 is provided at the right side of the camera
main body 2 when seen from the front such that the connection plate
23 is rotatable within a plane parallel to the right side of the
camera main body 2. In accordance with the rotation of the connection
plate 23, the image sensing unit 3 connected to the connecting plate
23 can be rotated by .+-.90 degrees from the rotation standard position
A. The reference numeral 500 shown in FIG. 5 denotes a rotation
support portion.
As shown in FIG. 5, a rectangular dented portion 309 is formed
on the connecting surface 308 of the connecting portion 3B. A total
of four engaging ledges 310a, 310b, 310c, 310d are formed at appropriate
portions of the inner periphery of the dented portion 309. Thus,
the image sensing unit 3 can be connected to the camera main body
2 by fitting the connecting plate 23 into the dented portion 309
so as to be engaged therewith.
The connection plate 23 is provided with a connecting terminal
portion 234 at its connecting surface as shown in FIG. 4. Within
the dented portion 309, as shown in FIG. 5, a connecting terminal
portion 334 with a plurality of connecting terminals is provided
so as to face the connecting terminal portion 234 of the connecting
plate 23. Thus, when the image sensing unit 3 is connected to the
camera main body 2 by way of the connecting plate 23, the image
sensing unit 3 and the camera main body 2 are electrically connected
via the aforementioned connecting terminal portions 234, 334.
The connecting plate 23 has rectangular cut-out portions 231a,
231b at appropriate portions of the long sides of the connecting
plate 23. On one surface having no connecting terminal portion 234
(hereinafter referred to as `rear surface`), cut-out portions are
formed at the longitudinal edge portions and the portions adjacent
to the cut-out portions 231a, 231b to form engaging portions 232a,
232b, 232c, 232d for engaging the corresponding engaging ledges
310a, 310b, 310c 310d. On the other surface having the connecting
terminal portion 234 (hereinafter referred to as `front surface`),
a groove is formed at an appropriate portion of the long side of
the connecting plate 23 having the cut-out portion 231a to form
an engaging portion 233 with which a key member 311 is engaged.
The connecting portion 3B of the image sensing unit 3 can be connected
to the connecting plate 23 of the camera main body 2 by the following
steps. First, the connecting surface 308 of the connecting portion
3B is disposed so as to be parallel to the connecting plate 23 in
a state that the engaging ledges 310c, 310d of the dented portion
309 oppose the corresponding cut-out portions 231a, 231b of the
connecting plate 23. The connecting portion 3B is then pressed against
the connecting plate 23. In this state, the engaging ledges 310c,
310d is fitted into the cut-out portions 231a, 231b of the connecting
plate 23, and the key member 311 is pressed by the front surface
of the connecting plate 23 to move to an unlock position against
the resilient force of the spring 312. Thus, the connecting portion
3B is pressed against the connecting plate 23 until the connecting
surface 308 coincides with the rear surface of the connecting plate
23. Thereafter, the connecting portion 3B is slid toward the rear
end thereof, i.e., in the direction of an arrow B shown in FIG.
5. As a result, the engaging ledges 310a, 310b, 310c, 310d of the
connecting portion 3B are engaged with the engaging portions 232a,
232b, 232c, 232d. Thus, the connecting portion 3B is fixed to the
connecting plate 23 in an undetachable manner. At the same time,
the key member 311 is moved to a lock position by the resilient
force of the spring 312 to be engaged with the engaging portion
233. Thus, the image sensing unit 3 can be locked to the connecting
plate 23.
The image sensing unit 3 can be detached from the connecting plate
23 by the following steps. First, the unlock lever 307 is moved
in the direction of coming apart from the connecting surface 308,
i.e., in the direction of an arrow C shown in FIG. 6 to the unlock
position shown by the broken line to unlock the engagement of the
key member 311 and the engaging portion 233. In this state, the
connecting portion 3B can be slid in the reverse, direction of an
arrow B shown in FIG. 5 along the connecting plate 23. Thereafter,
the connecting portion 3B is moved in the direction of coming off
the connecting plate 23. Thus, the image sensing unit 3 can be detached
from the connecting plate 23.
The above explanation is directed to the structure in which the
image sensing unit 3 is directly connected to the camera main body
3 by fitting the connecting plate 23 into the dented portion 309
of the connecting portion 3B of the image sensing unit 3 to connect
the connecting terminal portions 234, 334, as shown in FIG. 8A.
In this embodiment, the image sensing unit 3 can be connected to
the camera main body 2 by way of an exclusive cable 32.
FIG. 7 illustrates an appearance of the cable 32. The cable 32
has a cable portion 1321 having a length of 1 meter. At one end
of the cable portion 1321, a connecting plate 1322 having the same
structure as that of the connecting plate 32 for connecting the
image sensing unit 3 is provided. Provided at the other end of the
cable portion 1321 is a connecting portion 1323 having the same
configuration as that of the connecting portion 3B of the image
sensing unit 3. When connecting the image sensing unit 3 and the
camera main body 2, as shown in FIGS. 8A and 8B, the connecting
plate 1322 is fitted into the dented portion 309 of the connecting
portion 3B of the image sensing unit 3, and the connecting plate
23 of the camera main body 2 is fitted into the dented portion 1309
of the connecting portion 1323 attached to the other end of the
cable 32.
The connecting plate 1322 of the cable 32 is provided with a connecting
terminal portion 1234 having a plurality of connecting terminals
to be connected to the connecting terminal portion 334 provided
within the dented portion 309 of the connecting portion 3B of the
image sensing unit 3. Thus, when the image sensing unit 3 is connected
to the camera main body 2 via the cable 32, the image sensing unit
3 and the camera main body 2 is electrically connected via the connecting
terminal portions 234, 1334, 1234, 334.
In this embodiment, two types of cables are provided, one of them
being a cable 32 having a length of 1 meter, as shown in FIG. 8B,
the other being a cable 32' having a length of 5 meters as shown
in FIG. 8C. The image sensing unit 3 can be connected to the camera
main body 2 by way of the cable 32' having a length of 5 meters,
in the same matter as in the case where the cable 32 having a length
of 1 meter is used. In detail, as shown in FIGS. 8A and 8C, the
connecting plate 1322' of the cable 32' is fitted into the dented
portion 309 of the connecting portion 3B of the image sensing unit
3, and the connecting plate 23 of the camera main body 2 is fitted
into the dented portion 1309' of the connecting portion 1323' attached
to the other end of the cable 32'. In this connected state, the
image sensing unit 3 and the camera main body 2 are electrically
connected via the connecting terminal portions 234, 1334', 1234',
334.
As will be explained later, the level of the two contact points
f1, f2 provided to the connecting terminal portion 234 of the camera
main body 2 is designed such that the level is different in accordance
with the connecting state of the camera main body 2 and the image
sensing unit 3. Therefore, it is possible to detect if they are
connected directly or connected via a cable. Furthermore, it is
also possible to detect the length of the cable in a case where
they are connected via a cable.
Now referring to FIG. 1, a grip 4 is formed in the left-hand side
of the front face of the camera main body 2, and a built-in flash
lamp 5 is provided in the right-hand upper side at an appropriate
position. Frame forwarding and rewinding switches 6 and 7 are provided
near the centre of the top face of the camera main body 2 as shown
in FIG. 3. The forwarding switch 6 feeds the frame in the direction
that the frame number increases in the photographed order, and is
referred to as an UP key 6. The rewinding switch 7 feeds the frame
in the direction that the frame number decreases, and is referred
to as a DOWN key 7. A delete key D for deleting the images recorded
in the memory card 8 is provided on the left side of the DOWN key
7, and a shutter release button 9 is provided on the right side
of the UP key 6 in the rear view.
As shown in FIG. 3, an LCD 10 is provided in the middle of the
left-hand side of the rear face of the camera main body 2. The LCD
10 functions as a view finder during photographing, and as a display
during the reproduction of the recorded image.
Provided at the lower side of the LCD 10 is a compression rate
setting slide switch 12 for switching the compression rate K of
the image data to be recorded in the memory card 8. A power switch
PS, a flash lamp (which may be abbreviated as "FL") mode
setting switch 11, or the like, are provided on the upper side of
the LCD 10. The connection terminal 13 for externally connecting
a personal computer is provided on the side face of the camera main
body 2.
The flash lamp of the digital camera 1 has an "automatic flash
mode", a "forcible flash mode", and a "flash
prohibition mode". In the "automatic flash mode",
the built-in flash lamp 5 is automatically flashed according to
the luminance of the object. In the "forcible flash mode",
the built-in flash lamp 5 is forcibly flashed:regardless of the
luminance of the object. In the "flash prohibition mode",
light emission of the built-in flash lamp 5 is prohibited. Every
time the user presses the FL mode setting key 11 positioned above
the LCD 10 on the rear face of the camera main body 2, the flash
mode is switched among three modes in a cyclic order.
The digital camera 1 has a 1/8 compression rate and a 1/20 compression
rate, and the user can select the preferred compression rate K.
For example, if the compression rate setting switch 12 is shifted
to the right, the compression rate K is set to 1/8, and if it is
shifted to the left, the compression rate K is set to 1/20.
Although, in this embodiment, the compression rate K is set two
modes, it may be set to three or more values.
A photographing/reproduction mode setting switch 14 for selecting
the "photographing mode" or the "reproduction mode"
is provided at the top right of the rear face of the camera main
body 2. Digital pictures are taken in the photographing mode. In
the reproduction mode, the digital images recorded in the memory
card 8 are reproduced and displayed on the LCD 10. The photographing/reproduction
mode setting switch 14 is also a bicontact slide switch. For example,
if the switch 14 is shifted to the right, the reproduction mode
is selected, and if shifted to the left, the photographing mode
is selected.
A battery cavity 18 and a slot 17 for receiving the memory card
8 are positioned on the bottom face of the camera main body 2. The
battery cavity 18 and the slot 17 are covered with a clam-shell
type cover 15. The digital camera 1 according to the embodiment
has a power supply source E consisting of four AA batteries connected
in series.
FIG. 10 is a block diagram of the control system of the image sensing
unit 3.
FIG. 10 illustrates the state that the image sensing unit 3 and
the camera main body 2 are connected directly, i.e., without using
the cable 32 or the cable 32'.
The CCD 303 in the image sensing unit 3 photoelectrically converts
the optical image of the object focused by the macrozoom lens 301
into image signals of three colour components R (red), G (green)
and B (blue), and outputs the image signals to the signal processor
313. This image signal consists of sequence of pixel signals received
by the respective pixels. A timing generator 331 generates various
timing pulses for controlling and driving the CCD 303.
Since the diaphragm of the image sensing unit 3 is fixed, the exposure
of the image sensing unit 3 is controlled by adjusting the quantity
of exposure of the CCD 303, that is, the charge accumulation time
of the CCD 303, which corresponds to the shutter speed. If the luminance
of the object is too low to select to an appropriate shutter speed,
the level of the image signal outputted from the CCD 303 is adjusted
in order to compensate for the insufficient exposure. In other words,
at a low luminance, the exposure is controlled by adjusting both
the shutter speed and the gain. The level of the image signal is
adjusted by controlling the gain of the AGC circuit in the signal
processor 313.
The CCD driving circuit 314 generates a driving control signal
for the CCD 303 based on the signal supplied from the timing generator
331. The signals generated by the timing generator 314 includes
timing signals for the A/D converter 321, and clock signals (horizontal
transfer signals, vertical transfer signals, etc.) for controlling
the reading timing of the light-receiving signals from the respective
pixels.
The signal processor 313 applies a prescribed analogue signal processing
to the analog image signal outputted from the CCD 303. The signal
processor 313 has a CDS (correlation double sampling) circuit for
reducing the noise of the image signal and an AGC (automatic gain
control) circuit for adjusting the level of the image signal by
controlling the gain of this AGC circuit.
The light-quantity adjusting circuit 304 sets the light emission
of the built-in flash lamp 5 to a predetermined level determined
by the general controller 211 when the flash lamp is used during
the photographing. During the flash photographing, the flash light
reflected from the object is received by the light-adjusting sensor
305 upon starting exposure. When the quantity of light received
by the sensor 305 reaches a predetermined level, the light-quantity
adjusting circuit 304 supplies a flash stop signal to the flash
control circuit 214 via the general controller 211. In response
to the flash stop signal, the flash control circuit 214 stops the
light emission of the built-in flash lamp 5, whereby the light emission
amount of the built-in flash lamp 5 can be regulated to the prescribed
level.
One of the features of the present embodiment is that the A/D converter
321 is provided in the image sensing unit 3.
The A/D converter 321 converts each pixel signal (i.e., analog
signal) of the image signal sequence into a 10-bit digital signal
based on the A/D conversion clock supplied from the timing generator
331.
An EEPROM 341 stores, for example, an effective pixel number of
the CCD or information on the structural type of the image sensing
unit 3 such as a filter structure. The image sensing unit 3 can
be exchanged with another image sensing unit having another optical
element or CCD. When the image sensing unit is exchanged, the camera
main body 2 is controlled in accordance with the information on
the image sensing unit 3 obtained from the EEPROM 341.
The aforementioned image sensing unit 3 and the camera main body
2 which will be described later are electrically connected with
each other by way of a group of four connecting terminals 334a,
334b, 334c, 334d provided at the connecting terminal portion 334
and a group of four connecting terminals 234a, 234b, 234c, 234d
provided at the connecting terminal portion 234.
Next, inner structure of the camera main body 2 will be explained.
When the camera main body 2 is connected directly or via the cable
32 to the image sensing unit 3, the 10-bit digital image signal
outputted from the A/D converter 321 in the image sensing unit 3
is latched by the latch circuit 205 provided in the camera main
body 2.
A reference clock generating circuit 203 and a delay clock generating
circuit 204 are also provided in the camera main body 2. The reference
clock generating circuit 203 generates a clock CLK1 for the timing
generator 331. The delay clock generating circuit 204 supplies a
clock CLK2 for the latch circuit 205 based on the reference clock.
These circuits 203, 204 are controlled by the general controller
211.
A black level correction circuit 206 corrects the black level of
the digitalized pixel signal (hereinafter referred to as pixel data)
converted by the A/D converter 321 to the reference black level.
A white balance circuit (hereinafter referred to as WB circuit)
207 converts the level of the pixel data of each colour,component
of R, G or B, so that the white balance can be adjusted after .gamma.
(gamma) correction. The WB circuit 207 converts the level of the
pixel data of each colour component R, G, B using a level conversion
table inputted from the general controller 211.
The conversion, coefficient (or the slope of the characteristic
line): for each colour component in the level conversion table is
set each photographed image by the general controller 211.
The gamma correction circuit 208 corrects for the gamma characteristic
of the pixel data. The gamma correction circuit 208 has, for example,
six gamma correction tables with different gamma characteristics,
and uses the most appropriate gamma correction table according to
the photographed scene or the photographic conditions.
An image memory 209 stores the pixel data outputted from the gamma
correction circuit 208. The memory capacity of the image memory
209 corresponds to one frame data. Accordingly, if the CCD 303 has
an n.times.m pixel matrix, the image memory 209 has a memory capacity
of n.times.m pixel data, and each pixel data is stored in the corresponding
pixel position in the memory.
A VRAM 210 is a buffer memory for storing the image data to be
reproduced and displayed on the LCD 10. The memory capacity of the
VRAM 210 corresponds to the number of pixels of the LCD 10.
In the photographing preparation mode, each pixel data of the image
taken by the image sensing unit 3 every 1/30 seconds is subjected
to the prescribed signal processing by the sequence from the A/D
converter 321 to the gamma correction circuit 208, and stored in
the image memory 209. This pixel data is simultaneously transferred
to the VRAM 210 via the general controller 211, and displayed on
the LCD 10. The user can see the photographed object on the LCD
10. In the reproduction mode, the image read but from the memory
card 8 is subjected to the prescribed signal!processing by the general
controller 211, which is then transferred to the VRAM 210, and displayed
on the LCD 10.
A card I/F 212 is an interface for writing the image data into
the memory card 8 or reading the image data from the memory card
8. A communication I/F 213 is an interface based on, for example,
the USB standard, or an interface for externally connecting the
personal computer 19.
A flash control circuit 214 controls light emission of the built-in
flash lamp 5. In particular, the flash control circuit 214 controls
the quantity of flash light, flash timing, and so on, based on the
control signal supplied from the general controller 211. The flash
control circuit 214 also brings the light emission to zero based
on the flash stop signal inputted from the light-quantity adjusting
circuit 304.
An RTC (Real Time Clock) 219 is a time circuit for keeping the
track of the date and time of each photograph, which is driven by
a separate power source (not shown).
An operation unit 250 has switches including the UP key 6, the
DOWN key 7, the shutter release button 9, the FL mode setting key
11, the compression rate setting key 12, and the photographing/reproduction
mode setting switch 14.
The general controller 211 comprises a micro computer, and it organically
controls the driving timing of each element in the image sensing
unit 3 and the camera main body 2 so as to generally control the
photographing operation of the digital camera 1.
If in the photographing mode the shutter button 9 is pressed to
start photographing, the general controller 211 creates a thumb
nail image created from the image taken in the image memory 209
after the start of the photographing operation, and the compressed
image created by a JPEG method at the compression rate K when the
compression mode is selected by manipulating the compression rate
setting slide switch 12. A tag information (such as the frame number,
exposure value, shutter speed, compression rate K, photographing
date and time, flash ON/OFF data, scene information, image type,
judged result of the image, etc) stored in the memory card 8, the
compressed image and the thumb nail image are stored in the memory
card 8.
As shown in FIG. 11, the memory card 8 can store forty frames of
images taken by the digital camera 1 at a 1/20 compression rate.
Each of the frames 81-85 has tag information, high-resolution image
data (640.times.480 pixels) compressed by a JPEG method, and thumb
nail image data (80.times.60 pixels). Each frame may be treated
as an image file of EXIF type.
<Timing Control in a case of a cable connection>
The connection of the cable 32, 32' and the timing control in a
case where the image sensing unit 3 and the camera main body 2 are
connected via the cable 32 will now be explained with reference
to FIGS. 12 to 14. Although FIG. 12 is directed to the case where
the cable 32 having a length of 1 meter is used, the same explanation
can be applied to the case where the cable 32' having a length of
5 meters, except for the connection of the terminals f1, f2. Therefore,
the following explanation of each terminal of the cable will be
mainly directed to the cable 32 having a length of 1 meter. In FIG.
12, each terminal of the connecting terminal portions 1234, 1334
of the connecting plate 1322 and the connecting portion 1323 connected
to the ends of the cable 32 are allotted by the same reference numerals
of the terminals of the camera main body 2 and the image sensing
unit 3 to which each terminal is connected.
The connecting terminal portion 1234 of the connecting plate 1322
for connecting the image sensing unit 3 is provided with a power
terminal Vcc, terminals 334a to which 10-bit digital image signals
outputted from the A/D converter 321 are inputted, a ground terminal
GND and terminals 334b-334d for receiving and transmitting various
signals. On the other hand, provided to the connecting portion 1323
for connecting the camera main body 2 are terminals 234a corresponding
to the aforementioned terminals 334a, a ground terminal GND corresponding
to the aforementioned ground terminal GND, terminals 234b-234d corresponding
to the aforementioned terminals 334b-334d. Each terminal of the
connecting plate 1322 is connected to each terminal of the connecting
portion 1323 by a plurality of electric wires constituting the cable
portion 1321.
In the connecting plate 1322, the terminals 334a for receiving
signals supplied from the A/D converter 321 are connected to resistors
R1-R10 for protecting from static electricity, a buffer amplifier
33 for lowering the level of the image signal and the wave distortion
and resistors R11-R20 for protecting from static electricity in
series. Connected to the other ends of the resistors R11-R20 are
terminals 234a of the connecting portion 1323. By interposing the
resistors R1-R20 and the buffer amplifier 33 as mentioned above,
even in a case where the image sensing unit 3 is connected to the
camera main body 2 via the cable 32, the camera main body 2 can
surely obtain image data while preventing the deterioration of photographed
image.
The connecting terminal portion 234 of the connecting plate 23
connected to the camera main body 2 has two connecting terminals
f1, f2. On the other hand, the connecting portion 1323 of the cable
32 has terminals f1, f2 to be connected to the aforementioned terminals
f1, f2 of the connecting terminal portion 234. Furthermore, the
image sensing unit 3 has also corresponding terminals f1, f2. These
terminals f1, f2 are set so as to be connected to the camera main
body 2, the cable 32, 32' and the image sensing unit 3 as will be
mentioned below. Thus, it is possible to judge the connecting status
of the camera main body 2 and the image sensing unit 3.
As shown in FIG. 13A, the voltage of the connecting terminals f1,
f2 of the camera main body 2 are pulled up to that of the power
source Vcc. Therefore, in a case where nothing is connected to the
connecting terminals f1, f2, the level of each connecting terminal
f1, f2 is kept to H (high level), i.e., f1=H and f2=H.
As shown in FIG. 13B, the terminals f1, f2 of the image sensing
unit 3 are kept to the ground level. Thus, in a case where the image
sensing unit 3 is connected to the camera main body 2, the level
of each terminal f1, f2 of the camera main body 2 becomes to L (low
level), i.e, f1=L and f2=L.
In the cable 32 having a length of 1 meter, as shown in FIG. 13C,
the terminal f2 is connected to GND and the terminal f1 is opened.
Thus, in a case where the image sensing unit 3 is connected to the
camera main body 2, the terminals f1, f2 of the camera main body
2 becomes H and L, respectively, i.e, f1=H and f2=L.
In the cable 32:' having a length of 5 meters, as shown in FIG.
13D, as shown in FIG. 13D, the terminal f1 is connected to GND and
the terminal f2 is opened. Thus, in a case where the image sensing
unit 3 is connected to the camera main body 2 via the cable 32'
having a length of 5 meters, the terminals f1, f2 become L and H,
respectively, i.e., f1=L, f2=H.
As mentioned above, since the combination of the level of the two
terminals f1, f2 of the camera main body 2 is changed in accordance
with the connecting status of the image sensing unit 3 and the camera
main body 2, it is possible to judge the connecting status by the
general controller 211.
The timing of the latch in the camera main body 2 depending on
the lengths of the cables 32, 32' will be explained with referring
to FIG. 14.
(1) In a case where the image sensing unit 3 is directly connected
to the camera main body 2 (FIG. 14A)
The general controller 211 instructs the delay clock generating
circuit 204 to output a clock with no delay. Thus, the latch circuit
205 is driven by the delay clock CLK2 with delay time 0 relative
to the reference clock CLK1. The A/D converted image signal is inputted
into the latch circuit 205, and latched at the timing of the upward-arrow
shown in FIG. 14A.
(2) In a case where the image sensing unit 3 is connected to the
camera main body 2 via the cable having a length of 1 meter (FIG.
14B)
The A/D converted image signal is inputted into the latch circuit
205. Although the buffer amplifier 33 is mounted in the cable 32,
the delayed and distorted image signal is inputted into the latch
circuit 205. Thus, in a case where the general controller 211 detects
that the cable 32 having a length of 1 meter is used, the general
controller 211 instructs the delay clock generating circuit 204
to output a delay clock CLK2' with a phase delayed by time t1. Since
the image signal inputted into the latch circuit 205 is latched
at CLK2', the latch circuit 205 outputs an image signal from which
influence of the wave distortion by the cable 32 is completely deleted.
(3) In a case where the image sensing unit 3 is connected to the
camera main body 2 via the cable having a length of 5 meters (FIG.
14C)
The A/D converted image signal is inputted into the latch circuit
205. Although the buffer amplifier 33 is mounted in the cable 32,
the image signal, which is a little bit delayed and distorted as
compared to the case where the image sensing unit 3 is connected
to the' camera main body 2 via the cable having a length of 1 meter,
is inputted into the latch circuit 205. Thus, in a case where the
general controller 211 detects that the cable 32' having, a length
of 5 meters is used, the general controller 211 instructs the delay
clock generating circuit 204 to output a delay clock CLK2"
with a phase delayed by time t2 (t2>t1). Since the image signal
inputted into the latch circuit 205 is latched at CLK2", the
latch circuit 205 outputs an image signal from which influence of
the wave distortion by the cable 32' is completely deleted.
As mentioned above, by providing the latch circuit 205 for latching
the digital image signal supplied from the A/D converter mounted
in the image sensing unit 3 via the cable 32, 32' in the camera
main body 2 and delaying the latching timing of the image signal
in accordance with the length of the cable, the same output signal
as that obtained when the image sensing unit 3 is directly connected
to the camera main body 2 can be obtained, which enables an appropriate
image processing at the image processing portion.
In the above mentioned embodiment, although the delay time t1,
t2 is set by adjusting the firmware of the general controller 211,
a hardware such as timer means may be employed. Further, although
two kinds of cables are used in the above mentioned embodiment,
it is possible to use more than two kinds of cables with an increased
number of the recognizing terminals.
According to the above mentioned embodiment, since the A/D converter,
which converts the analog image signal supplied from the image pick-up
element into the digital image signal, is provided at the image
sensing unit which is detachably attached to the camera main body,
the image signal to be transmitted to the camera main body from
the image sensing unit becomes digital signal. Therefore, even if
the image sensing unit is connected to the camera main body via
a cable, the influence of noise can be decreased as compared to
the case where the analog image signal is transmitted. Thus, an
appropriate digital image signal can be inputted into the image
processing portion. Furthermore, it is not required to raise the
gain of the image signal at the image sensing unit side and the
power consumption rate can be decreased, which enhances the utility
of the digital camera.
Since the camera main body is equipped with the latch circuit for
latching and outputting the digital image signal from the A/D converter
into the image processing portion, the signal wave distortion or
signal delay caused by the connection of the cable can be deleted
by setting the latch timing by the latch means.
Since detector for detecting the length of the cable is provided
and the timing for latching the image signal is changed depending
on a detected result of said detector, an appropriate correction
of the distortion of the wave distortions or the like can be performed
even if the length of the cable changes. Accordingly, it is possible
to use various kinds of cables with different length.
Since the timing for latching is changed to be delayed in accordance
with the length of the cable, even if a cable having a long length
is used, the distortion of the signal wave can be avoided.
Since the judging processing portion for judging whether the image
sensing unit is directly connected to the camera main body or the
image sensing unit is connected to the camera main body via the
cable and the timing for latching the image signal is changed depending
on the result of the judging means, an appropriate image signal
can be outputted to the image processing portion, either when the
image sensing unit is directly connected to the camera main body
or the image sensing unit is connected to the camera main body via
the cable.
The terms and descriptions in this specification are used only
for explanatory purposes and the present invention is not limited
to these terms and descriptions. It should be appreciated that there
are many modifications and substitutions without departing from
the spirit and the scope of the present invention which is defined
by the appended claims. |