JPH04239279A - Electronic steel camera - Google Patents

Abstract

PURPOSE:To obtain an economical system at a low cost, without necessitating a backup battery by using an EEPROM for a memory card without affecting the speed of a consecutive photographing due to the speed of the writing in a memory card even at the time of the consecutive photographing. CONSTITUTION:A picture signal indicating a picture picked up by a CCD 10, is transmitted through an amplifier 14, and an A/D conversion circuit 16 to a signal processing circuit 18. The picture signal is operated for an interpolating processing or the like by the signal processing circuit 18, operated for a compressing processing by a compression-encoding circuit 20, and stored in a buffer 22. Until then, the processing is operated in a real time. A memory card controller 26 reads out data from the buffer 22, and stores the data in a memory card 24 using the EEPROM at an appropriate writing speed of the memory card 24.

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 As is well known, in an electronic still camera, image signals captured by a solid-state imaging device are recorded on a recording medium such as a memory card. In this case, since the image signal has a large amount of data, the captured image signal is compressed by, for example, orthogonal transform encoding, and then recorded on a recording medium.

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

0004

[Problem to be solved by the invention] However, SRA
Since M is a volatile semiconductor memory, it requires a backup battery, and it is also expensive when storing large amounts of data such as image data, making the price of the memory card high. There was a problem.

Therefore, in recent years, EEP, which is a nonvolatile semiconductor memory that is inexpensive and does not require a backup battery, has been developed.
The use of ROM (electrically erasable/rewritable read-only memory) in memory cards is being considered.

However, EEPROM has a slower writing speed than static RAM, and when used in an electronic still camera, there is a problem that the continuous shooting speed is limited. The present invention eliminates the drawbacks of the prior art and provides an electronic still camera that takes advantage of the advantages of EEPROM by using an EEPROM in the memory card, and that can keep up with the continuous shooting speed in this case. The purpose is to

[0007]

[Means for Solving the Problems] An electronic still camera according to the present invention is an electronic still camera that continuously photographs an object scene and stores image data representing this object scene in a memory card. EEP as a memory card
An image recording means using a ROM, an imaging means for continuously photographing the scene, a signal processing means for performing color adjustment and gradation correction on the image signal sent from the imaging means, and a signal processing means for processing the image signal by the signal processing means. an image data compression means for compressing and encoding image data; and a buffer storage means for storing a series of multiple frames of image data outputted from the compression means at high speed and sending out the stored data to an image recording medium at a slow writing speed. and storage control means for storing the image data sent out from the buffer storage means in an image recording medium as image data in units of frames.

Further, this camera drives the image data compression means, the buffer storage means, and the storage control means in conjunction with the depression of a shutter button for driving the image pickup means, and stores the image data in the buffer storage. The apparatus is characterized in that it includes a system control means for turning off the image data when all the image data have been sent out from the means.

Furthermore, the buffer storage means outputs a write address to the buffer storage means in synchronization with the read speed of the dual port memory having different write and read speeds at its input and output, and the image data compression means. write address generation means, read address generation means for outputting a read address to buffer storage means in synchronization with the writing speed of the image recording medium, and data output from the image data compression means are valid and are not transmitted to the image recording medium. When writing is possible, the control means causes the write address generation means and the read address generation means to start their operations, and the addresses output by the write address generation means and the read address generation means respectively are input, and the addresses match. The apparatus is characterized in that it includes a detecting means for stopping the reading.

0010

[Operation] According to the electronic still camera according to 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 a buffer. stored in the means. The buffer storage means stores image data for the number of frames of the continuous shooting. The image data stored in this buffer storage means is read out in response to the writing speed of the image storage medium, and is sequentially stored at predetermined addresses of the image storage medium.

[0011]

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

[0012] The electronic still camera in this embodiment is as follows:
As shown in FIG. 1, an optical imaging system including a photographing lens 12, an aperture 13, and a solid-state imaging device 10 images a field. The solid-state image sensor 10 is configured of, for example, a CCD (charge coupled device). This CCD captures one frame of image through a series of operations of accumulating, transferring, and discharging charge on its imaging surface, and in the case of continuous shooting, this process is repeated to capture several frames per second. I can do it. The image signals are, for example, red (R), green (G) and blue (
B) is output in the form of a color component signal. This color component signal is output in a raster scanning format similar to a TV signal.

The image signal captured by this CCD is
The signal is sent to a signal processing block 18 via an amplifier 14 and an A/D conversion circuit 16. The amplifier 14 is the imaging body 10
This is a circuit that amplifies each image signal sent out from the camera to an appropriate level. The A/D conversion circuit 16 is the amplifier 14
This circuit converts the amplified image signal into digital data. The digital data converted by this A/D conversion circuit 16 is quantized into, for example, 8 bits for each color component signal RGB. The signal processing circuit 18 subjects the image data converted to digital data to pre-processing such as white balance adjustment and gradation correction, and luminance and color difference processing to convert color component signal data into a luminance signal and a color difference signal. This 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 20 is a circuit that compresses and encodes image data. Specifically, one frame of image data is orthogonally transformed encoded in units of blocks of multiple pixels. This orthogonal transformation is, for example, a two-dimensional discrete cosine transformation (DCT)
applies. As a result, each block is converted into data in the frequency domain, and the data is sequentially arranged in the horizontal and vertical directions of the screen starting from the lowest frequency. The encoding is 2
The image data subjected to the dimensional orthogonal transformation is normalized after the transformation coefficients are truncated. Coefficient truncation involves comparing orthogonally transformed transform coefficients with a predetermined threshold value, and truncating a portion that is less than or equal to the threshold value. Normalization is
The truncated transform coefficients are divided by a predetermined quantization step value to perform quantization (compression) using normalization coefficients.

In this embodiment, the image signal compressed and encoded in this manner is temporarily stored in the buffer memory 22. The data temporarily stored in the buffer memory 22 is
Memory card 2 via memory card controller 26
Recorded in 4. The memory card 24 is composed of an EEPROM (electrically erasable/rewritable read-only memory) which is a non-volatile semiconductor memory.

The buffer memory 22 is composed of a dual port memory 30 whose data input/output speed is asynchronous. This dual port memory 30 converts high-speed data input by continuous shooting into low-speed data and outputs the converted data. The storage capacity is for multiple frames of images taken continuously with this camera.
For example, data for 5 to 10 frames is temporarily stored in compressed data format. The capacity of the buffer is smaller than that of the memory card 24, which stores several tens of frames.

The memory card controller 26 transfers data output from the buffer memory 22 to the memory card 24.
This circuit controls writing to the frame address of .

The compression circuit 20, buffer memory 22, and memory card controller 26 are connected to the system controller 2.
Controlled by 7. This system controller 27 is
When the shutter switch 28 is pressed, it turns on, and in this camera, the buffer memory 22, which consumes the most power,
Power is supplied to the compression circuit 20 and memory card controller 26 to activate these circuits. When there is no more image data in the buffer memory 22, the power supply is turned off, thereby making the camera energy-saving.

FIG. 2 is a block diagram of the buffer memory 22. In this figure, dual port memory 30 is connected to bus B
Accumulating the output data of the compression circuit 20 input from 1,
This is a storage circuit that outputs data to the memory card controller 26 from the bus B2 at the data write speed of the memory card 24. Input/output control of this memory 30 is controlled by the following blocks via a selector 32.

The controller 34 includes the compression encoding circuit 20
When the data output from the memory card 24 is valid, the signal DI-VALID is "1" (logical level), and when the memory card controller 26 cannot write data to the memory card 24, the signal C-BUSY is "1". do. Signal DI-VALID is “1” and signal C-BUS
When Y is "0", a signal DO-VALID indicating that the data output from the buffer memory 22 is valid.
Output “1” to the memory card controller 26,
It is also a circuit that outputs an enable signal to the write address generation block 36 and the read address generation block 38.

The write address generation block 36 has a clock W for outputting data from the compression encoding circuit 20.
C is input, and in synchronization with this, a write address is outputted to the dual port memory 30 via the selector 32. Data sent via the bus B1 is written into the memory 30 at a designated address in synchronization with the clock WC. The read address generation block 38 is a circuit that outputs a read address to the dual port memory 30 via the selector 32 in synchronization with the clock RC generated when the memory card controller 26 writes data to the memory card 24. In the memory 30, data at a designated address is read out via the bus B2 in synchronization with the clock RC.

The match detection block 40 is supplied with the respective output addresses from the write address generation block 36 and the read address generation block 38, and when the two match, outputs the address sent from the read address generation block 38. This is an address detection circuit that stops the data and prevents empty reading of unwritten addresses.

Next, an explanation will be given of the operation of the electronic still camera of this embodiment in the above configuration when taking pictures, especially continuous pictures. First, when the continuous shooting switch (not shown) is turned on and the shutter switch 28 is pressed, the CC
D10 sequentially photoelectrically converts and outputs an image of a field imaged through a lens 12 on its imaging plane.

This image signal is sent from the amplifier 14 to the A/D
The signal passes through the conversion 16, is converted into digital data, and is sent to the signal processing circuit 18. The image signal is processed by this signal processing circuit 1
At step 8, interpolation processing and color difference signal processing are performed for each frame, and each predetermined block in that frame is sent to the compression encoding circuit 20.

In the compression encoding circuit 20, the image data of each frame is compressed by orthogonal transform encoding. This compressed image data is written to the buffer memory 22 at real-time speed.

m is stored in this buffer memory 22 by continuous shooting.
Once the frame image data is stored, the stored data is read out from the memory card 24 at a slow writing speed via the memory card controller 26. The memory card controller 26 writes the output data to each frame-allocated address of the memory card 24. In this case, the system controller 27 turns on when the shutter switch 28 is pressed, supplies power to the buffer memory 22, compression circuit 20, and memory card controller 26, which consume the most power in this camera, and When all the image data stored in 22 is read out, the power supply is turned off.

According to the electronic still camera of this embodiment, when continuous shooting is performed, the image signals obtained by the imaging body 10 are sequentially subjected to signal processing and compression encoding processing in real time. The images are temporarily stored in the buffer memory 22 that can store multiple frames, and can be sent from the buffer memory 22 to the memory card 24 at low speed, so even if the memory card 24 is an EEPROM, Storage processing can be performed satisfactorily at this writing speed. Therefore, a memory card using an EEPROM that is inexpensive and does not require a backup battery can be used in an 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, an inexpensive memory with a relatively small capacity can be used as the buffer memory 22. Also, during continuous shooting, the system controller 27
Since each part is turned on only from the time when the shutter button 28 is pressed until all the data in the buffer memory 22 is read out, power consumption can be kept to a minimum.

[0028]

As explained above, according to the present invention, compressed image data is written to the buffer storage means at high speed and temporarily stored, and from this buffer storage means to the final image storage means at low speed. Since writing is performed, it is possible to keep up with the continuous shooting speed even if a slow EEPROM memory card is used. In addition, power is supplied only until the processing means surrounding the buffer storage means is linked with the shutter button and data stored in the buffer storage means is read, making it possible to use an energy-saving electronic still camera economically. It can be configured as follows.

[Brief explanation of the drawing]

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 the internal configuration of the 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)

[Claims] 1. An electronic still camera that continuously photographs a scene and stores image data representing the scene on a memory card, the camera comprising an image recording means using an EEPROM as the memory card. , an imaging means for continuously photographing a scene, a signal processing means for performing signal processing on image data sent from the imaging means, and an image for compressing and encoding the image signal processed by the signal processing means. a data compression encoding means; a buffer storage means for storing a series of image signals of a plurality of frames outputted from the compression encoding means at high speed and sending the stored data to the image recording means at a slow writing speed; 1. An electronic still camera comprising: storage control means for storing image data sent from the storage means in the image recording medium as frame-by-frame image data. 2. The electronic still camera according to claim 1, wherein the image data compression means, the buffer storage means, and the storage control means are controlled by pressing a shutter button for driving the imaging means. 1. An electronic still camera comprising: a system control means that is driven in conjunction with the motion of the electronic still camera and turns off the image data when all the image data is sent out from the buffer storage means. 3. The electronic still camera according to claim 1, wherein the buffer storage means includes a dual port memory whose input and output have different write and read speeds, and a dual port memory that is synchronized with the read speed of the image data compression means. write address generation means for outputting a write address to the buffer storage means; read address generation means for outputting a read address to the buffer storage means in synchronization with the writing speed of the image recording medium; and image data compression means. control means for causing the write address generation means and the read address generation means to start operations when the data to be output is valid and can be written to the image recording medium; and the write address generation means and the read address. Input the address output by each generation means,
1. An electronic still camera comprising: detection means for stopping readout when addresses match.