JPH031681A - image recording device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image recording device that records still images on a recording medium.

[Prior Art] An example of an image recording device is, for example, a digital still camera. Such still cameras generally use a memory element with a relatively slow writing speed as an external recording medium, and in order to increase the continuous shooting speed, multiple frame memories are installed in the camera body, and one A configuration has been proposed in which a captured image is written in another frame memory while an image stored in one frame memory is written to an external recording medium (for example, Patent Application Publication No. 64485 of 1988).

[Problem to be solved by the invention] However, in the above conventional example, in order to increase the speed of snapshots, for example, it is necessary to increase the number of frame memories in the camera body, which leads to an increase in circuit size and cost information. Furthermore, as the amount of memory increases, power consumption also increases.

Therefore, an object of the present invention is to provide an image recording device that eliminates such drawbacks.

[Means for Solving the Problems] An image recording device according to the present invention is an image recording device that records image information on a relatively low-speed recording medium, and includes a memory that temporarily stores image signals on a screen-by-screen basis, and a continuous It is equipped with a specification means for specifying a recording speed and a compression means that can freely select a signal compression rate, and the compression means compresses the read signal of the memory at a compression rate corresponding to the continuous recording speed specified by the specification means. and supplies the compressed signal to the recording medium.

[Operation] By compressing with the compression means described above, even if the continuous recording speed is increased, the supply speed to a relatively low-speed recording medium can be kept low in accordance with the compression ratio. That is, there is no need for a dedicated memory for continuous recording.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a block diagram of an embodiment of the present invention. In FIG. 1, 10 is a photographic lens, 12 is a diaphragm, and 14 is a shutter, which constitute a photographic optical system. 16
18 is an amplifier; 20 is an A/D converter that digitizes an analog signal; 22 is a timing control circuit;
Reference numeral 4 denotes an oscillation circuit that generates a reference signal for the timing control circuit 22. 26 is a frame memory for temporarily storing photographed image signals; 28 is a memory control circuit for controlling the frame memory 26; 30 is a write address generation circuit for generating a write address signal for the frame memory 26; 32 is for generating a read address. read address generation circuit, 3
6 outputs either the write address generation circuit 30 or the read address generation circuit 32 to the frame memory 26.
A switch 38 applied to the address terminal of is a buffer that switches between writing and reading.

40 is a system control circuit that controls the entire illustrated device;
2 is a compressor with a compression ratio al (1/2 in this embodiment); 44
is a compressor with a compression ratio a2 (1/4 in this example), 46
is a compressor with a compression ratio of a3 (1/6 in this example), 48
is a non-compressor (ie, a compressor with zero compression ratio). 50 is a compressor 42°44.46 and a non-compressor 4
A switch 52 is a memory pack control circuit that controls data writing to the external memory pack 54 using the address, data, and write signals selected by the switch 50. .

The external memory pack 54 may be, for example, a battery-backed SRAM, a large-scale FF1D RAM whose writing speed is slowed to reduce power consumption, or an EEPROM which does not require battery backup but has a slow writing speed.
It consists of solid-state memory elements such as. Write speed for each memory pack is 200ns with battery-backed SRAM
ec/byte, low power consumption DR with battery backup
2 psec/byte in AM.

EEFROM is 31 psec/byte. Also, the pixel size of the frame memory 26 is 512x48.
All the signals of one screen when the pixel is set to 0 are stored in external memory.
The time required to write to the pack 54 is 49m5ec for battery-backed SRAM and 490m5ec for low-power DRAM with battery backup.
M is 7.61 sec.

56 is a shutter switch linked to shutter button operation, 58.60 is a continuous shooting mode selection switch, 62 is a switch interface circuit, and 64 is a switch 5.
The snapshot mode selection signal according to 8.60 is transmitted to the compressors 42 and 4.
4.46 and selection signals C3I and C52 of the non-compressor 48
, C33, C34. 66 is a compressor 42°44.46 and a non-compressor 4
This is a switch that selects the address and read signal of No. 8 and applies it to the read address generation circuit 32.

Next, the operation shown in FIG. 1 will be explained. When the shutter button is pressed, the system control circuit 40 controls the diaphragm 12 so that the optimum amount of light is incident on the image sensor 16, and the shutter 14 is operated for the shutter time set by a shutter speed setting device (not shown). open. The image sensor 16 converts an optical image produced by a photographing optical system into an electrical signal. This electrical signal is sequentially read out in synchronization with the timing signal from the timing control circuit 22, amplified by the amplifier 18, and converted into, for example, an 8-bit digital signal by the A/D converter 20. The timing control circuit 22 appropriately divides the clock from the oscillator 24 and outputs it to the image sensor 16 and the A/D converter 2.
0 and a timing signal for each operation of the memory control circuit 28.

System control circuit 40 simultaneously closes shutter 14 by driving signal EN low, activating buffer 38 and directing the output of A/D converter 20 to frame memory 26 . The switch 36 is connected to the output side of the write address generation circuit 30 by the signal ■, and the frame
The memory 26 writes data from the buffer 38 to the address specified by the write address signal of the write address generation circuit 30 in synchronization with the write signal W of the memory control circuit 28 . When a series of readings from the image sensor 16 is completed,
Memory control circuit 28 sends a capture completion signal to system control circuit 40, informing it that the image has been captured in frame memory 26. Note that when one screen has been captured into the frame memory 26, the write address generation circuit 3
0 stops activity and reduces power consumption.

Next, the system control circuit 40 passes the continuous shooting mode selection switches 58 and 6 through the switch interface circuit 62.
The state of 0 is read and the switch 50°66 is controlled by control signals 5EL1 and 5EL2 as shown in Table 1.

The continuous shooting speed can be selected using switches 58 and 60 as shown in Table 1.

Explain the stop-motion mode. At this time, switch 58.
60 are both on. In the time-lapse mode, the shutter 14 opens and closes each time the shutter button is pressed, and the image signal from the image sensor 16 is temporarily stored in the frame memory 26 in the above-described procedure. As shown in Table 1, the non-compressor 4
8 is selected, the switch 50.66 is connected to the non-compressor 48 by the control signals 5ELI and 5EL2, and the stored image signal of the frame memory 26 is read out according to the read address signal of the read address generation circuit 32. , is written to external memory pack 54 via decompressor 48 and memory pack control circuit 52.

If, for example, Daisha 1iDRAM is used as the external memory pack 54, a memory pack with a capacity of about 2 Mbyte has been prototyped using current technology, and if it is not compressed, this memory pack can store an image of 520 x 480 pixels. Can store 8 images.

Table 1 Explains the case of quick photography. When switch 58 is off and switch 60 is off, 4 frames per second; when switch 58 is on and switch 60 is off, 8 frames per second; switch 58
When the switch 60 is off and the switch 60 is on, the rate is 12 frames/second. The allowable time for storing one image in the external memory pack is 250 m5ec, which is approximately twice the write speed of the external memory pack 54 made of DRAM, which is 490 m5ec. Therefore, in this case, the compressor 42 reduces the amount of recorded information by half and shortens the writing time to the external memory pack 54 for each pixel.

Similarly, in the case of 8 frames/second, the compressor 44
In the case of 12 frames/sec, the amount of written information is compressed to 1/6 by the compressor 46.

During quick shooting, it is sufficient to keep one of the compressors 42, 44, 46 active, so from the perspective of reducing power consumption, the power to the unused compressors 42, 44, 46 and non-compressor 48 is cut off. It is preferable to keep it.

For example, the compressors 42, 46, and 48 are as follows. That is, the compressor 42
The compressor 44 performs subsampling and 174 compression using the DPCMffi child table 4 bits, and the compressor 46 compresses the representative value of every 3 pixels by 1/2 using the DPCMffi child table 4 bits. /6 compression.

In the above embodiment, different compression processes are performed by selectively using a non-compressor and a plurality of compressors, but the compression rate is passed through a high-speed digital signal processing circuit that can be externally controlled, and is controlled by an external control signal. , its image compression rate (
Including uncompressed. ) may be switched. Further, although the external memory pack has been described using a solid-state memory element as an example, it goes without saying that other recording media such as a magnetic bubble memory, a magnetic disk, an optical disk, etc. may also be used. Furthermore, as a compression method, D
Although the case of PCM has been described, other methods such as vector quantization, block coding, and discrete cosine transformation may also be used.

Further, although the description has been given using an electronic still camera as an example, the present invention is not limited to this, and it goes without saying that it can be applied to other recording devices.

[Effects of the Invention] As can be easily understood from the above explanation, according to the present invention, continuous images can be recorded on a relatively low-speed image recording medium without increasing the memory capacity. Ta.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention. 10: Photographic lens 12: Aperture 14: Shutter 16:
Solid-state image sensor 18: Amplifier 22: Timing control circuit 26: Frame memory 28: Memory control circuit
30: Write address generation circuit 32: Successive address generation circuit 38: Buffer 40 System control circuit
42, 44° 46: Compressor 48: Non-compressor 52: Memory pack control circuit 54: External memory pack 5
6: Shutter switch 58, 60: Continuous shooting mode selection switch 64: BCD binary decoder

Claims (1)

[Claims] An image recording device that records image information on a relatively low-speed recording medium, comprising a memory that temporarily stores image signals on a screen-by-screen basis, a designation means for designating a continuous recording speed, and a compression means that can freely select a signal compression rate. An image recording device, characterized in that the compression means compresses the readout signal of the memory at a compression rate according to the continuous recording speed designated by the designation means, and supplies the compressed signal to the recording medium. .