JP2980702B2 - Electronic still camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic still camera using a memory card as an image recording medium for storing image data.

[0002]

2. Description of the Related Art In an electronic still camera, an image signal picked up by a solid-state image pickup device is recorded on a recording medium such as a memory card, as is well known. In such a case, since the image signal has a large data amount, a taken image signal is, for example, subjected to orthogonal transform coding and compression, and then recorded on a recording medium.

Conventionally, a static RAM (SRAM) capable of performing high-speed reading and writing has been used for a memory card of such an electronic still camera.

[0004]

However, since the SRAM is a volatile semiconductor memory, a backup battery is required, and it is expensive to store a large amount of data such as image data. As a result, there is a problem that the price of the memory card becomes high.

Therefore, in recent years, an EEPROM, which is a nonvolatile semiconductor memory that is inexpensive and does not require a backup battery, has been developed.
(Electrically erasable / rewritable read-only memory) is being considered for use in memory cards.

However, the EEPROM has a static RA
The writing speed is slower than that of M, and when used in an electronic still camera, there is a problem that the continuous shooting speed is limited. The present invention provides an electronic still camera that overcomes such disadvantages of the prior art, makes use of the advantage of using an EEPROM for a memory card, and can follow the continuous shooting speed in this case. The purpose is to:

[0007]

SUMMARY OF THE INVENTION An electronic still camera according to the present invention is an electronic still camera for continuously photographing a scene and storing image data representing the scene in a memory card. EEPROM as memory card
, An image pickup means for continuously photographing an object scene, a signal processing means for performing color adjustment and gradation correction on an image signal sent from the image pickup means, and a signal processing means for processing the image signal. Image data compression means for compressing and encoding the image data; buffer storage means for storing a series of plural frames of image data output from the compression means at a high speed and sending the stored data to the image recording medium at a low writing speed; ,
Storage control means for storing the image data sent from the buffer storage means in the image recording medium as image data in units of one frame.

In this camera, the image data compression means, the buffer storage means, and the storage control means are driven in conjunction with the pressing of a shutter button for driving the image pickup means, so that the image data is stored in the buffer storage means. A system control means for turning off the image data when all of the image data is transmitted from the means is provided.

Further, the buffer storage means outputs a write address to the buffer storage means in synchronism with the read speed of the image data compression means, and a dual port memory having different write and read speeds at its input and output. Write address generating means, read address generating means for outputting a read address to the buffer storage means in synchronization with the writing speed of the image recording medium, data output from the image data compressing means being valid, and Control means for causing the write address generation means and the read address generation means to start operation when writing is possible, and the addresses respectively output by the write address generation means and the read address generation means, so that the addresses match. And detecting means for stopping reading. .

[0010]

According to the electronic still camera of the present invention, when continuous shooting is performed by the imaging means, the image signal is processed at high speed by the signal processing means and the image data compression means, and is stored in the buffer memory. Stored in the means. The buffer storage unit stores image data for the number of frames of the continuous shooting. The image data stored in the buffer storage is read out in response to the writing speed of the image storage medium, and is sequentially stored at a predetermined address of the image storage medium.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an electronic still camera according to the present invention will be described in detail with reference to the accompanying drawings.

The electronic still camera in this embodiment is
As shown in FIG. 1, an object field is imaged by an optical imaging system including an imaging lens 12, an aperture 13, and a solid-state imaging device 10. The solid-state imaging device 10 is configured by, for example, a CCD (charge coupled device). This CCD captures an image of one frame by a series of operations of charge accumulation, transfer, and discharge on the imaging surface, and repeatedly shoots several images per second for continuous shooting. Can be. The image signal is output in the form of, for example, red (R), green (G), and blue (B) color component signals. This color component signal is output in the same raster scanning format as the TV signal.

An image signal picked up by the CCD is sent to a signal processing block 18 via an amplifier 14 and an A / D conversion circuit 16.
Sent to The amplifier 14 is a circuit that amplifies an image signal sent from the imaging body 10 to an appropriate level. A /
The D conversion circuit 16 is a circuit that converts the image signal amplified by the amplifier 14 into digital data. The digital data converted by the A / D conversion circuit 16 is a color component signal RG
B is quantized to, for example, 8 bits. The signal processing circuit 18 performs pre-processing such as white balance adjustment and gradation correction on the image data converted to digital data, and luminance / color difference processing for converting the color component signal data into a luminance signal and a color difference signal. It is a circuit that performs signal processing.

The image data processed by the signal processing circuit 18 is sent to a compression encoding circuit 20. This compression encoding circuit
Reference numeral 20 denotes a circuit for compressing and encoding image data. More specifically, image data for one frame is subjected to orthogonal transform coding in units of blocks of a plurality of pixels. For this orthogonal transform, for example, a two-dimensional discrete cosine transform (DCT) is applied. As a result, the data is converted into data in the frequency domain for each block, and the data is sequentially arranged in the horizontal and vertical directions of the screen from the lower frequency. In the encoding, the image data that has been subjected to the two-dimensional orthogonal transform is subjected to coefficient truncation with respect to the transform coefficient, and then normalized. The coefficient truncation is to compare the orthogonally transformed transform coefficients with a predetermined threshold value and to cut off a portion below the threshold value. The normalization is to divide (transform) the truncated transform coefficient by a predetermined quantization step value and perform quantization (compression) using the normalized coefficient.

In this embodiment, the image signal thus compressed and encoded is temporarily stored in the buffer memory 22. The data temporarily stored in the buffer memory 22 is recorded on the memory card 24 via the memory card controller 26. The memory card 24 is configured by an EEPROM (electrically erasable / rewritable read-only memory) which is a nonvolatile semiconductor memory.

The buffer memory 22 comprises a dual port memory 30 whose data input / output speed is asynchronous. The dual port memory 30 converts high-speed data input by continuous shooting to low-speed data and outputs the converted data. The storage capacity temporarily stores a plurality of frames of video, for example, data of 5 to 10 frames when continuously shot by the camera in the form of compressed data. The capacity of the buffer is smaller than that of the memory card 24 storing several tens of frames.

The memory card controller 26 is a circuit for controlling the writing of data output from the buffer memory 22 to the frame address of the memory card 24.

The compression circuit 20, the buffer memory 22, and the memory card controller 26 are controlled by a system controller 27. This system controller 27 is turned on when the shutter switch 28 is pressed, and in this camera,
Power is supplied to the buffer memory 22, the compression circuit 20, and the memory card controller 26 which consume the most power to activate these circuits. When there is no more image data in the buffer memory 22, the power supply is turned off, so that the camera can be made energy saving.

FIG. 2 is a configuration diagram of the buffer memory 22.
In this figure, a dual port memory 30 accumulates output data of a compression circuit 20 input from a bus B1,
This is a storage circuit that outputs to the memory card controller 26 at the data writing speed of the memory card 24. The input / output control of the memory 30 is controlled by the following blocks via the selector 32.

When the data output from the compression encoding circuit 20 is valid, the controller 34 inputs a signal DI-VALID of "1" (logical level) and the memory card controller 26 starts writing data to the memory card 24. If not, input the signal C-BUSY of "1". The signal DI-VALID is "1" and the signal C-
When BUSY is "0", a signal DO-VALID "1" indicating that the data output from the buffer memory 22 is valid is output to the memory card controller 26, and the write address generation block 36 and the read address generation block
A circuit for outputting an enable signal to 38.

A clock WC for outputting data from the compression encoding circuit 20 is input to the write address generation block 36, and a write address is selected in synchronization with the clock WC.
Is a circuit for outputting to the dual port memory 30 via the. In the memory 30, data transmitted via the bus B1 is written to a specified address in synchronization with the clock WC.
The read address generation block 38 selects a read address in synchronization with a clock RC generated when the memory card controller 26 writes data to the memory card 24.
This is a circuit for outputting to the dual port memory 30 via 32. In the memory 30, data at the designated address is read out via the bus B2 in synchronization with the clock RC.

The match detection block 40 outputs the address sent from the read address generation block 38 when the respective output addresses are supplied from the write address generation block 36 and the read address generation block 38 and they match. And an address detection circuit for preventing an unwritten address from being read idle.

Next, the operation of the electronic still camera according to the present embodiment in the above-described configuration, in particular, in the case of performing continuous shooting, will be described. First, when a continuous shooting switch (not shown) is turned on and the shutter switch 28 is pressed, the CCD 10
Sequentially photoelectrically converts the image of the object field formed on the image forming plane via the lens 12, and outputs the image.

This image signal is supplied from an amplifier 14 to an A / D converter 16.
, And is converted to digital data and sent to the signal processing circuit 18. The image signal is subjected to interpolation processing and color difference signal processing for each frame by the signal processing circuit 18, and is sent to the compression encoding circuit 20 for each predetermined block in the frame.

In the compression encoding circuit 20, the image data of each frame is subjected to an orthogonal transformation encoding to be subjected to a compression process. The compressed image data is written to the buffer memory 22 at a real-time speed.

When m frames of image data are stored in the buffer memory 22 by continuous shooting, the stored data is read out at a low writing speed of the memory card 24 via the memory card controller 26. The memory card controller 26 writes the output data to the frame allocation addresses of the memory card 24, respectively. In this case, the system controller 27 is turned on when the shutter switch 28 is pressed, and in this camera, the buffer memory 22, the compression circuit 20, and the memory card controller which consume the most power are used.
When power is supplied to the buffer 26 and all the image data stored in the buffer memory 22 is read, the power supply is turned off.

According to the electronic still camera of the present embodiment, when continuous shooting is performed, the image signal obtained by the image pickup body 10 is sequentially subjected to signal processing and compression encoding processing in real time. Is temporarily stored in a buffer memory 22 capable of storing a plurality of frames, and can be sent from the buffer memory 22 to a memory card 24 at a low speed. The storage processing can be sufficiently performed at the writing speed. Therefore, a memory card using an inexpensive EEPROM that does not require a backup battery or the like can be used for the electronic still camera without affecting the continuous shooting speed of the electronic still camera. In this case, since the compressed image data is temporarily stored in the buffer memory 22, a relatively small-capacity inexpensive memory can be used as the buffer memory 22. Further, at the time of continuous shooting, since each part is turned on only during the time from when the shutter button 28 is pressed by the system controller 27 to when all data in the buffer memory 22 is read,
Power consumption can be minimized.

[0028]

As described above, according to the present invention, the compressed image data is written into the buffer storage means at a high speed and temporarily stored, and the buffer image is transferred from the buffer storage means to the final image storage means at a low speed. Since writing is performed, it is possible to follow the continuous shooting speed even if a slow-speed EEPROM memory card is used. Also, since power is supplied only until the processing means around the buffer storage means is linked with the shutter button and the data stored in the buffer storage means is read out, an energy-saving electronic still camera can be economically manufactured. Can be configured.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an electronic still camera according to the present invention.

FIG. 2 is a block diagram showing an internal configuration of a buffer memory in FIG. 1;

[Explanation of symbols]

 10 CCD 18 Signal processing circuit 20 Compression circuit 22 Buffer 24 Memory card 27 System controller 28 Shutter switch

Claims (3)

(57) [Claims] 1. An electronic still camera for continuously photographing an object scene and storing image data representing the object scene in a memory card, the camera comprising: an image recording unit using an EEPROM as the memory card; Imaging means for continuously photographing an object scene; signal processing means for performing signal processing of image data transmitted from the imaging means; and an image for compression-encoding an image signal processed by the signal processing means. Data compression encoding means, storing a series of image signals of a plurality of frames output at high speed from the compression encoding means, and sending out stored data at a writing speed corresponding to the writing speed of the image recording means,
The completion of transmission of the storage data is determined by address writing and reading.
An electronic still comprising: buffer storage means for detecting a match of a dress ; and storage control means for storing image data sent from the buffer storage means in the image recording medium as image data of one frame unit. camera. 2. The electronic still camera according to claim 1, wherein the camera is configured to control the image data compression unit, the buffer storage unit, and the storage control unit by pressing a shutter button for driving the imaging unit. Drive in conjunction with the movement,
The come from the buffer memory means and the image data is sent all the electronic still camera, which comprises a system control means for turning off their drive. 3. The electronic still camera according to claim 1, wherein said buffer storage means synchronizes with a dual port memory having different writing and reading speeds at its input and output, and a reading speed of said image data compression means. A write address generating means for outputting a write address to the buffer storage means, a read address generation means for outputting a read address to the buffer storage means in synchronization with a writing speed of the image recording medium; Control means for causing the write address generation means and read address generation means to start operation when output data is valid and writing to the image recording medium is possible; write address generation means and read address Enter the addresses that the generators output, and if the addresses match An electronic still camera comprising: a detection unit that stops reading.