Digital Camera Patent Abstract
A CCD digital camera system has a digital camera and a detachable
display device. The digital camera includes an imaging device for
receiving an image of an object to be photographed, the imaging
device outputting a digital signal corresponding to the received
image. The digital camera also includes a data memory for storing
a portion of the digital signal and a controller for controlling
a transfer of a first portion of the digital signal from the imaging
device to the memory. The display device has an image memory for
storing image data and a display for displaying an image corresponding
to the image data stored in the image memory. The controller monitors
one of its inputs for a predetermined signal, the predetermined
signal indicating whether the display device is attached to the
digital camera. If a presence of the predetermined signal is detected,
the controller transfers all of the digital signal to the image
memory. Digital Camera Patent Claims
What is claimed is:
1. A CCD digital camera system including a digital camera and a
detachable display device, said digital camera comprising:
an imaging device for receiving an image of an object to be photographed,
said imaging device outputting a digital signal corresponding to
said received image;
a data memory for storing a portion of said digital signal; and
a controller for controlling a transfer of a first portion of said
digital signal from said imaging device to said data memory, said
display device comprising:
an image memory for storing image data; and
a display for displaying an image corresponding to said image data
stored in said image memory,
said controller monitoring an input from said display device for
a predetermined signal indicating that said display device is attached
to said digital camera, said controller transferring all of said
digital signal to said image memory if a presence of said predetermined
signal is detected; and
said digital camera further comprising a compression unit for compressing
said digital signal, said compression unit receiving said digital
signal from said image memory if said controller detects said predetermined
signal.
2. The CCD digital camera system according to claim 1, said compression
unit receiving said digital signal from said data memory if said
controller of said digital camera fails to detect said predetermined
signal.
3. The CCD digital camera system according to claim 1, wherein
said compression unit receives said digital signal from said data
memory if said controller of said digital camera fails to detect
said predetermined signal.
4. The CCD digital camera system according to claim 1,
said digital signal being also supplied to said display device
to display said image.
5. The CCD digital camera system according to claim 1, said digital
camera further comprising a storage device, said compression unit
outputting a compressed signal having a predetermined compression
ratio, said compressed signal being stored in said storage device.
6. The CCD digital camera system according to claim 5, said digital
camera further comprising an expansion unit, said compressed signal
stored in said storage device being read out of said storage device
and expanded at an expansion ratio determined in accordance with
said compression ratio when a reproducing mode is selected.
7. The CCD digital camera system according to claim 1, said imaging
device comprising:
a data processing unit; and
a CCD, said CCD comprising:
a matrix of photoelectric detectors, each of said photoelectric
detectors outputting an electrical signal corresponding to light
from said received image;
a plurality of column shift registers, each of said plurality of
column shift registers having a plurality of column registers, each
of said plurality of column registers being connected to a corresponding
one of said photoelectric detectors aligned in a single column of
said matrix, each of said plurality of column registers storing
a charge corresponding to said electrical signal output by said
photoelectric detectors; and
a row shift register having a plurality of row registers, each
of said row registers being connected to an output of a corresponding
one of said column shift registers,
said controller controlling said plurality of column shift registers
to shift said charge to said corresponding row registers, and
said controller controlling said row shift register to transfer
said charge to said data processing unit, said data processing unit
outputting said digital signal to said image memory if said predetermined
signal is detected.
8. The CCD digital camera system according to claim 7, said controller
controlling said row shift register to transfer said charge to said
data processing unit, said data processing unit outputting said
digital signal to said data memory if said predetermined signal
is not detected.
9. The CCD digital camera system according to claim 8, said controller
controlling said column shift registers and said row shift register
to transfer a predetermined number of charges from said column registers
to said data processing unit, said predetermined number of charges
corresponding to a first portion of said digital signal stored in
said memory.
10. The CCD digital camera system according to claim 9,
said digital camera further comprising a compression unit for compressing
said digital signal, said compression unit outputting a compressed
signal, and
said first portion of said digital signal being transferred to
said compression unit in a plurality of data blocks, each of said
plurality of data blocks corresponding to a second portion of said
digital signal, said second portion of said digital signal being
a portion of said first portion of said digital signal.
11. The CCD digital camera system according to claim 10,
said controller outputting vertical drive pulses for shifting said
charge stored in said column shift registers to an adjacent register.
12. The CCD digital camera system according to claim 11,
said digital camera further comprising a storage device for storing
said compressed signal, said controller inhibiting an output of
said vertical drive pulses until all of said first portion of said
digital signal has been stored in said storage device.
13. A method of storing an image of an object photographed using
a CCD digital camera system, the CCD digital camera system comprising
a digital camera and a detachable display device, the method comprising:
converting an optical image of an object to be photographed into
a digital signal;
detecting a presence of a predetermined signal, the predetermined
signal being present if the display device is attached to the digital
camera;
storing the digital signal in an image memory contained within
the display device if a presence of the predetermined signal is
detected;
storing the digital signal in a data memory contained within the
digital camera if the presence of the predetermined signal is not
detected;
compressing said image signal stored in said image memory if said
presence of said predetermined signal is detected; and
outputting said compressed image signal to a storage device.
14. The method of storing an image according to claim 13, further
comprising the steps of:
compressing the image signal stored in the data memory if the presence
of the predetermined signal is not detected; and
outputting the compressed image signal to a storage device.
15. A CCD digital camera system including a digital camera and
a detachable display device, said display device comprising:
an image memory for storing image data; and
a display for displaying an image corresponding to said image data
stored in said image memory, said digital camera comprising:
an imaging device for receiving an image of an object to be photographed,
said imaging device outputting a digital signal corresponding to
said received image; and
a controller,
said controller monitoring an input for a predetermined signal
indicating that said display device is attached to said digital
camera, said controller storing said digital signal in said image
memory of said display device when a presence of said predetermined
signal is detected;
said digital camera comprising a signal processing unit,
said predetermined signal stored in said memory being read out
of said memory and processed by said signal processing unit when
said controller detects said presence of said predetermined signal.
16. The CCD camera system according to claim 15, said digital camera
further comprising a storage device, said signal processing unit
compressing said predetermined signal, said compressed predetermined
signal being stored in said storage device.
Digital Camera Patent Description
BACKGROUND OF THE INVENTION
The present invention relates to a camera system, having a camera
that can record an image of an object to be photographed using a
CCD (Charge Coupled Device) and a display device for displaying
the photographed image.
Recently, digital cameras which electronically store data related
to a photographed image have become popular. The digital camera
converts an optical image to electronic image data and digitally
records the image data on a recording medium, such as an IC card.
When the image is reproduced, the recorded digital data is retrieved
from the storage medium and displayed on a display device or printed
out as a hard copy image.
Generally, a CCD receives the optical image and outputs an electrical
signal corresponding to the optical image. The electrical signal
is A/D converted, and then stored on a recording medium, such as
a floppy disk or an IC memory card. The CCD is constructed such
that photoelectric elements, such as photodiodes which convert the
intensity of light into an electric charge, are arranged in a matrix.
The electric charge generated in each element is transferred in
vertical and horizontal directions. Thus, the image data for one
picture frame, which is obtained by exposing the CCD to an object
image, is outputted as a series of data and transferred by horizontal
and vertical CCD shift registers HCCD and VCCD, respectively, and
recorded onto the recording medium.
In this type of camera, since the size of the image data outputted
by the CCD is large, if the image data is recorded as is, the recording
medium can store only a small number of pictures. Therefore, the
image data obtained by the CCD is compressed before it is recorded.
When reproducing the image, the compressed data is read out and
expanded.
If the camera uses the above described system, since the compression
takes a certain period of time, the data outputted by the CCD should
first be stored unmodified, in a data storage memory (a field memory
or a frame memory). Then, the stored data is compressed. With this
construction, a large capacity data storage memory is required,
since a large amount of data must be compressed. However, a large
capacity memory is physically large, resulting in the overall size
of the camera being large. Further, a large capacity memory is expensive,
thereby increasing the cost of manufacturing the camera.
Further, in this type of camera, it is desirable that the camera
display the picture immediately after photographing the object.
In order to display the photographed image, the image data is stored
in an image memory, and then, the stored image data is used to drive
a display device. However, in this system, the image memory is used
only for storing the image data that is used for driving the display
device. Therefore, in order to store data on a recording medium,
as well as display data on a display device, the camera must be
provided with a data storage memory and an image memory. However,
both memories are large capacity memories and are therefore physically
large and expensive, thereby increasing the size of the camera and
its manufacturing cost.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide
an improved CCD digital camera system having a digital camera and
a detachable display device, in which when the display device is
attached thereto, utilizes the image memory of the display device
to store image data that will be processed for storage on a recording
medium.
Another object of the present invention is to be able to determine
whether the display device is attached thereto, and to store the
image data in either an image memory of the display device or an
internal memory of the digital camera, depending on the determination
made.
According to one aspect of the present invention, there is provided
a CCD digital camera system which includes a digital camera and
a detachable display device. The digital camera includes:
an imaging device for receiving an image of an object to be photographed,
the imaging device outputting a digital signal corresponding to
the received image;
a data memory for storing a portion of the digital signal; and
a controller for controlling a transfer of a first portion of the
digital signal from the imaging device to the memory. The display
device includes:
an image memory for storing image data; and
a display for displaying an image corresponding to the image data
stored in the image memory.
The controller monitors an input thereto for a predetermined signal.
The predetermined signal indicates whether the display device is
attached to the digital camera. If a presence of the predetermined
signal is detected, the controller transfers all of the digital
signal to the image memory.
According to another aspect of the present invention, there is
provided a method of storing an image of an object photographed
using a CCD digital camera system, which includes a digital camera
and a detachable display device. The method includes the steps of:
converting an optical image of an object to be photographed, into
a digital signal;
detecting a presence of a predetermined signal, the predetermined
signal being present if the display device is attached to the digital
camera; and
storing the digital signal in an image memory contained within
the display device, if a presence of the predetermined signal is
detected.
According to a further aspect of the present invention, there is
provided a CCD digital camera system which includes a digital camera
and a detachable display device. The display device includes:
an image memory for storing image data; and
a display for displaying an image corresponding to the image data
stored in the image memory. The digital camera includes:
an imaging device for receiving an image of an object to be photographed,
the imaging device outputting a digital signal corresponding to
the received image; and
a controller.
The controller monitors an input thereto for a predetermined signal.
The predetermined signal indicates whether the display device is
attached to the digital camera. If a presence of the predetermined
signal is detected, the controller stores the digital signal in
the image memory of the display device.
DESCRIPTION OF THE ACCOMPANYING DRAWINGS
FIG. 1 is a block diagram of a CCD digital camera system which
embodies the present invention;
FIG. 2 shows a schematic of the construction of the CCD shown in
FIG. 1;
FIG. 3 is a timing diagram showing timing signals related to an
operation of the CCD shown in FIG. 1;
FIG. 4 shows a schematic map of a memory used in the CCD digital
camera shown in FIG. 1;
FIGS. 5A and 5B show a flowchart of an operation of the CCD digital
camera system shown in FIG. 1; and
FIG. 6 shows a diagram illustrating an allowance/inhibition of
a transmission of a vertical drive signal of the CCD shown in FIG.
1.
DESCRIPTION OF THE EMBODIMENTS
FIG. 1 is a block diagram of a CCD digital camera system embodying
the present invention.
The camera system includes a CCD digital camera 100 and a display
device 200 which is detachably coupled to the CCD digital camera
100.
The CCD digital camera 100 has a CCD 1 which has 380,000 photodiodes
arranged in a matrix. An image of an object to be photographed is
formed on a light receiving surface of the CCD 1 by an optical system
2. The CCD 1 then outputs image data corresponding to the image
of the object. First, reset noise included in the image data is
decreased or eliminated, and then, the image data is converted into
digital image data in a CDS-A/D (correlation double sampling-analog/digital)
converter 3. The digital image data is then transmitted to a DSP
(digital signal processor) 4. In the DSP 4, the digital image data
is formatted as a predetermined data signal. A memory gate circuit
5 allows the formatted data signal to be transmitted to a memory
6 at a predetermined timing. The size of the memory 6 is relatively
small with respect to the entire data to be recorded. Further, the
size of memory 6 is determined so that it can store the minimum
amount of data that is required by a compression circuit 7. This
minimum amount of data is then transmitted to the compression circuit
7 and compressed. The compressed data is then recorded onto a memory
card 10, which is connected to a connector 9, through an interface
8.
The camera 100 has a drive signal generator 11 for outputting a
drive signal to be used for transferring the image data generated
by the CCD 1. A gate circuit 12 controls the timing of the drive
signal. The drive signal is inputted to a CCD driver 13. The CCD
driver 13 drives the CCD 1, in accordance with the drive signal,
to output image data sequentially to the CDS-A/D circuit 3.
The operation is controlled by a microprocessor 14. States of a
mode selection switch 15, a recording switch 16 and a play (reproducing)
switch 17, are inputted to the microprocessor 14. The compression
ratio of the image data is selected using the mode selection switch
15. When the recording switch 16 is depressed, the CCD 1 outputs
the image data, which is then processed and recorded on the recording
medium, as described above.
If the play switch 17 is depressed, the photographed image is displayed
on a display device 200.
The display device 200 has an image memory 21 which stores image
data corresponding to the image to be displayed. The stored image
data is converted into analog image data using a D/A converter 22,
and then transmitted to an encoder 23, and a display driver 24.
The display driver 24 drives a display element 25, the display driver
being controlled by a microprocessor 26. In this embodiment, an
LCD (liquid crystal display), or a TFT (thin film transistor) is
used as the display element 25.
When the display device 200 is coupled to the camera 100, a connector
18 of the camera 100 and a connector 27 of the display device 200
are connected, allowing data to be transferred from microprocessor
14 of the camera 100 to the microprocessor 26 of the display device.
This permits the exchange of control signals and image data between
the camera 100 and the display device 200. Further, when the connectors
18 and 27 are connected, the image memory 21 is connected to the
compression/expansion unit 7 of the camera 100. In this embodiment,
as shown in FIG. 1, data can be transferred from the output of the
memory gate circuit 5, to the image memory 21, and then transferred
from the image memory 21 to the compression/expansion circuit 7.
The image memory 21 is a frame memory which can store image data
corresponding to one frame of the image to be displayed.
FIG. 2 shows a schematic construction of the CCD 1. As described
above, there are 380,000 photodiodes PD arranged in a matrix. In
the matrix shown in FIG. 2, vertical transfer shift registers VCCD
extend in a column direction as shown in FIG. 2. Further, on one
side of the vertical transfer CCD shift registers VCCD, a horizontal
transfer shift register HCCD extends in a row direction.
The output of the photodiode PD (i.e., the electric charge generated
by the photodiodes PD), is transmitted to the VCCD in accordance
with a charge transfer signal TG (FIG. 3). Then, in accordance with
a vertical drive signal .phi.V (.phi.V1-.phi.V4) (FIG. 3), a charge
in the shift registers VCCD is transmitted to the shift register
HCCD. The image data transferred to the shift register HCCD is transferred
in the horizontal direction in accordance with a horizontal drive
signal .phi.H (.phi.H1, .phi.H2) (FIG. 3), and outputted through
an amplifier.
FIG. 3 is a timing chart showing the timing of the drive signals.
When the charge transfer signal TG is HIGH, electric charge (image
data) is transferred from the photodiodes PD (CCD pixels) to the
shift registers VCCD. Then, one line of image data is transferred
to the horizontal shift register HCCD, by applying the vertical
drive signal .phi.V to the shift registers VCCD. Then, transfer
of the charge in the shift register HCCD is performed in accordance
with the horizontal drive signal .phi.H. The drive signals are generated
such that one line of image data is outputted synchronously with
the vertical drive signal .phi.V.
FIG. 4 shows a schematic map of the memory 6. As described above,
the memory 6 contains only a part of the image data outputted by
the CCD 1. The capacity of the memory 6 is determined in accordance
with the amount of image data (which is related to the number of
the CCD pixels), which are compressed by the compression circuit
7, at one time. In this embodiment, the compression is performed
for units of 8.times.8 pixels. The capacity of the memory 6 is determined
as follows:
Memory capacity=N0.times.Ncmp
where,
N0 is the number of pixels in one horizontal line of the CCD1,
Ncmp is the number of horizontal lines of the CCD 1 that are be
compressed at one time.
Since the number of horizontal lines of pixels of the CCD 1 is
about 500, and only 8 lines are compressed at a time, the size of
the memory 6 is about 1/62 the size of the memory that would be
required if all the data outputted by the CCD 1 was stored synchronously.
The compression circuit 7 compresses the image data in blocks of
8.times.8 pixels, thereby reducing the size of the data to be stored.
The image data is first stored in the memory 6, and then read out
as an 8.times.8 pixel matrix. The size of the compressed data is
determined in accordance with the mode compression rate selected
by the mode selection switch 15. In this embodiment, the size of
the compressed data can be 1/4, 1/8 or 1/16 the original size of
the data.
When the compressed data is expanded, the microprocessor 14 detects
the compression ratio of the data and determines the expansion ratio
in accordance with the compression ratio so that the expanded data
is expanded to its original size.
The drive signal generating section 11 generates the vertical drive
signal .phi.V and the horizontal drive signal .phi.H. The gate circuit
12 periodically inhibits a predetermined number of the vertical
drive signals .phi.V from passing therethrough in accordance with
an instruction outputted from the microprocessor 14. The number
of vertical drive signals .phi.V which are inhibited, depends on
the compression ratio selected with the mode selection switch 15.
The drive signal generation section 15 also generates a timing
signal which is synchronized with the vertical drive signal .phi.V
and the horizontal drive signal .phi.H. The timing signal is transmitted
to the display device 200 so that the display device 200 and the
camera 100 process the signals synchronously.
FIGS. 5A and 5B show a flowchart illustrating the operation of
the CCD camera system.
When the recording switch 16 is depressed, the microprocessor 14
detects whether the display device 200 is connected to the camera
100, in step S1. In this embodiment, this detection is executed
as described below.
One of the data pins of the microprocessor 26 is always grounded.
Therefore, when microprocessor 26 and microprocessor 14 are connected
through a data bus, one of the bus lines, which is connected to
the grounded pin of the microprocessor 26, will be grounded. Thus,
by monitoring for the grounded state of this bus line, the microprocessor
14 can determine whether it is connected to the microprocessor 26,
and further, determine whether the display device 200 is connected
to the camera 100. However, a mechanical sensor which detects the
mechanical connection of the display device 200 with the camera
100 can also be used.
If the display device 200 is not connected to the camera 100 (S1:NO),
the camera executes a normal recording operation (step S2) as described
below with reference to FIG. 5B.
When the recording switch 16 is operated, the CCD 1 outputs image
data corresponding to the image formed, by the optical system 2,
on the surface of the CCD 1. The image data is transferred to the
VCCD synchronously with the charge transfer signal TG generated
by the drive signal generating section 11. In accordance with the
horizontal and vertical drive signals .phi.H and .phi.V, the image
data is transmitted from the CDS-A/D converter 3 to the DSP 4. The
digital data is then gated through memory gate circuit 5 and temporarily
stored in the memory 6. In step S3, the data stored in the memory
6 is subsequently read out in a predetermined block (as described
above), and sent to the compression/expansion circuit 7, where it
is compressed. In step S4, the compressed data is recorded on the
memory card 10, through interface 8. This process is repeated until
it is determined in step S5 that all the data has been recorded
on the memory card 10.
In FIG. 5A, if the microprocessor 14 detects the connection of
the display device 200 (S1:YES) when the recording switch 16 is
activated, the image data is recorded using the image memory 21
of the display device 200.
The microprocessor 14 communicates with the microprocessor 26,
with the microprocessor 26 setting a write mode (a mode that controls
the image memory 21 so that it stores data) in step S6. Simultaneously,
the gate circuit 12 allows every vertical driving signal .phi.V
to pass through. Thus, the image data output by the CCD 1 is transferred
to the image memory 21 through the memory gate circuit 5, in step
S7, without being stored in the memory 6. Since the image memory
21 can store data output by all the pixels of the CCD 1, the image
data outputted by the CCD 1 is transmitted continuously to the image
memory 21 until all the image data is stored in the image memory
21, as shown in step S8. Further, this direct method of storing
the image data can be done in a relatively short period of time.
After all the image data is transmitted to the image memory 21,
the microprocessor 14 controls the compression/expansion circuit
7 to operate in a compression mode, in step S9.
In accordance with the communication between the microprocessors
14 and 26, the image data stored in the image memory 21 is transmitted
to the compression/expansion circuit 7 in predetermined data blocks.
The image data compressed by the compression/expansion circuit 7
is recorded to the memory card 10, in step S10. This process is
repeated, in step S11, until all the image data stored in the image
memory 21 is compressed and recorded to the memory card 10.
While the image data stored in the image memory 21 is being recorded
to the memory card 10, the image data is displayed on the display
element 25, as described before. Thus, the photographed image can
be immediately displayed after the photographing operation is finished.
The image data that has been recorded to the memory card 10 can
be retrieved and displayed on the display device 200, as described
below.
When the play button 17 is activated, the microprocessor 14 detects
the compression ratio of the recorded image data. Then, the image
data to be displayed is transmitted to the compression/expansion
circuit 7 in predetermined data blocks. The image data is expanded
at an expansion ratio which is determined in accordance with the
compression ratio detected by the microprocessor 14, and then, the
expanded image data is stored in the image memory 21, which has
been set, by the microprocessor 26, to operate in the write mode.
By repeating the above process, all the image data recorded to the
memory card 10 is retrieved, and written in the image memory 21.
When all the image data has been stored in the image memory 21,
the microprocessor 14 controls the image memory 21 to operate in
a read mode, whereby the stored image data is read from the image
memory 21, and displayed on the display element 25, as described
above.
As described above, the determination is made, in step S1, whether
an external display device is connected to the camera. If there
is no external display device connected, then the memory 6 in the
camera 100 is used, and the data must be gated from the CCD 1 to
the memory 6, before the data can be compressed and recorded.
The compression and recording operations take a relatively long
period of time. More specifically, the recording operation (i.e.,
recording data to the memory card 10) takes 100-500 nsec per byte
of data. During this recording period, the succeeding compression
operation cannot be executed. In other words, the memory 6 is occupied
by the image data being processed. If subsequent data is outputted
by the CCD 1, the data cannot be stored in the memory 6. Thus, for
a predetermined period, the microprocessor 14 inhibits the vertical
drive signal .phi.V from passing through the gate circuit 12 so
that the signal is not transmitted to the CCD driver 13. Thus, during
this period, the transfer of the image data in the shift registers
VCCD does not occur.
When all the data stored in the memory 6 is compressed and recorded,
the gate circuit 12 gates the vertical drive signal .phi.V to the
CCD driver 13. The subsequent data is transferred in the vertical
direction in the shift registers VCCD, and in the horizontal direction
in the shift register HCCD in accordance with the horizontal drive
signal .phi.H. The data is then transmitted to the memory 6, and
subsequently compressed and recorded (shown in step S4 of FIG. 5B),
as described above.
The above process is repeated until all the image data has been
compressed and recorded (shown in step S5 of FIG. 5B).
In this embodiment, MOS shift registers VCCD are used, and therefore,
the shift registers VCCD are capable of holding the accumulated
charge (the image data) while the above operation is being performed.
FIG. 6 illustrates an allowance/inhibition of transmission of the
vertical drive signal .phi.V in the gate circuit 12. As shown in
FIG. 6, the charge transfer signal TG is output after the recording
switch 16 is depressed, resulting in the CCD 1 accumulating charge
corresponding to the object image. As described above, the charge
accumulated on each photodiode PD is transferred to its respective
shift registers VCCD when the charge transfer signal TG is generated.
Depending on the compression ratio selected, the microprocessor
14 controls the gate circuit 12 to regulate the number of vertical
drive signals .phi.V sent to the CCD driver 13.
If the compression ratio is 1/4, the microprocessor 14 regulates
the gate circuit 12 to allow eight vertical drive signals .phi.V
to be inputted to the CCD driver 13 so that eight lines of image
data is outputted from the CCD 1. The image data is stored in memory
6. The gate section 12 then inhibits the next six vertical drive
signals .phi.V from being inputted to the CCD driver 13. The six
vertical drive signals .phi.V are made invalid. Then, the final
horizontal drive pulse .phi.H is output, which transfers the last
row of data stored in the shift registers to the CDS A/D. This occurs
before the first vertical drive signal is made invalid. Thereafter,
no more data is transferred to the horizontal shift register HCCD
(and therefore, out of the CCD 1) during the period that the vertical
drive signals are made invalid. This allows the compression and
recording of the image data, stored in memory 6, to be carried out
during this period.
Further, as shown in FIG. 6, if the compression ratio is 1/8, then
three vertical drive signals .phi.V are inhibited from being sent
to the CCD driver 13. If the compression ratio is 1/16, then two
vertical drive signals .phi.V are inhibited from being sent to the
CCD driver 13. The number of invalid vertical drive signals is calculated
as follows:
First, a gate period tg during which the gate circuit 12 inhibits
the vertical drive signals .phi.V from being sent to the CCD driver
13 is calculated by the equation
where m is a coefficient intrinsic to a construction of the system;
P is the number of pixels on one horizontal line of the CCD;
tc is a time required to record one byte of data;
L is the number of rows of a matrix of pixels to be compressed
at one time; and
n is the compression ratio.
Then, a number of invalid vertical drive signals N, which is the
quotient of tg/th rounded up to the next highest integer value is
determined, where th is a horizontal scanning period (64 sec for
an NTSC signal) of the CCD 1. For example, a CCD having 380,000
elements will be illustrated below.
P=768
L=8 (compression is executed for each 8.times.8 matrix)
m=1.5 (m=2 if the color difference signals are synchronized in
phase when the Y signal and a color difference line sequential signal
are compressed).
from the above, the gate period tg is
If tc=140 nsec, gate periods tg4, tg8 and tg16 corresponding to
the compression ratios of 1/4, 1/8 and 1/16, respectively, are calculated
as follows.
If n=1/4,
therefore N=6
If n=1/8,
therefore N=3
If n=1/16,
therefore N=2
When the display device 200 is connected to the camera 100, the
CCD output is uninterrupted, since there is sufficient memory to
store all the data output by the CCD 1, before the data is compressed
and recorded.
As described above, according to the present invention, the camera
100 can compress and record the image data without using an external
device or memory. However, if the display device 200 is connected
to the camera 100, the image memory, which is relatively large,
can be used to store the image data before the image data is compressed
and recorded. In other words, if an external device having a relatively
large memory for storing data to be displayed, is connected to the
camera 100, the camera 100 can use the larger extra memory during
the recording process. If the larger extra memory is used for recording,
the image data obtained by the CCD can be quickly transferred to
the memory and recorded, thereby improving the speed of the camera
system. Further, no image information is lost as a result of compressing
the data. Thus the image quality is maintained.
Since the system according to the present invention requires an
external device as well as the camera, the price of the system increases.
However, in the system according to the present invention, the image
memory is used not only for storing the data to be displayed, but
also for storing the data to be recorded.
Since the camera of the system according to the present invention
does not have an image memory which stores a frame of an image,
but is still capable of compressing and recording the image data
without this type of image memory, the manufacturing cost as well
as the size of the camera can be decreased. Further, the display
device of the system according to the present invention has an image
memory, which can be used not only for displaying the image, but
also for recording the image. Therefore, the functionality of the
entire system is improved, since the image can be displayed as it
is photographed, and the time required to store the data on the
storage medium can be reduced. |