JPH03252282A - Electronic still camera - Google Patents

Abstract

PURPOSE:To attain consecutive shot for a picture with many frames by applying band compression to picture information and writing a picture data in a 2nd memory in which data are able to be written at a comparatively high speed. CONSTITUTION:An optical system 1 is subject to drive control by an optical system drive section 2 and the image of an object light passing through an optical system 1 is formed on a solid-state image pickup element 3. Picture information by one pattern to be picked up is stored tentatively in a buffer memory 6. The digital data subject to band compression by a compression circuit 7 and the buffer memory 6 is stored in a consecutive shot memory 8 having a memory capacity corresponding to desired consecutive shot numbers at a fast write speed such as an SRAM. Series of picture information in the consecutive shot mode stored in the consecutive shot memory 8 is transferred to a low speed write memory 9 at a speed in matching at a write speed of the memory 9 such as an E<2>PROM.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electronic still camera, and more particularly, to an electronic still camera that photographs and records still images using a solid-state image sensor such as a CCD.

[Prior Art] In addition to electronic still cameras that form a subject image on a solid-state image sensor and record this image information as an analog signal on a floppy disk attached to the camera,
There is a method in which image information is written as a digital signal into a buffer memory built into the camera, temporarily held there, and then recorded again on a removable external recording medium attached to the camera.

External recording media for this latter so-called digital still camera include SRAM, bubble memory, and E2F.
There are ROM, etc., but bubble memory excluding SRAM, E2
FROM and the like do not require a backup power source and have the advantage of being small and large in capacity, but they generally have the disadvantage of slow writing speed.

In this case, even if the digital still camera uses a buffer memory built into the camera that can be accessed at high speed, the writing speed of the external recording medium is slow, so the shooting speed of the digital still camera is limited by the external recording speed. It will depend on the writing speed of the medium. In other words, for example, if the time it takes to record one screen worth of image information from the buffer memory to the external recording medium is 3 seconds, the next image will be taken unless you wait at least 3 seconds plus the writing time to the buffer memory. It becomes impossible to do so.

However, if it takes a long time from one photograph to the next, it has the disadvantage that continuous photographing of objects within a short period of time is not possible.

Therefore, in the digital still camera described in Japanese Patent Application Laid-Open No. 63-64485, image information from a solid-state image sensor on which an optical image of a subject is formed is stored in a buffer memory. In a digital still camera that records the image information on an external recording medium, the buffer memory includes a plurality of dynamic R
It is characterized in that AMs are arranged in parallel, and a write memory selection circuit is provided at the front stage of the dynamic RAM, and a read memory selection circuit is provided at the rear stage of the dynamic RAM.

As a result, one screen imaged on the solid-state image sensor is assigned to one of the multiple dynamic RAMs, so multiple screens can be stored in the dynamic RAM even if the writing speed of the external recording medium is slow. This allows continuous shooting.

In addition, the electronic still camera described in Japanese Patent Application Laid-open No. 62-269581 includes an image sensor that photoelectrically converts an image for one screen, and data compression of the image information of the screen bones obtained from this image sensor to create a digital image. It is equipped with a high-efficiency image encoder for obtaining a signal, and a memory back for storing a digital image signal data-compressed by the high-efficiency image encoder, and the memory back is constituted by a writable and erasable digital semiconductor memory, Moreover, it is configured to be detachable from the camera body. That is, after compressing the image signal output from the imaging device using a high-efficiency image encoder,
Since it is recorded as a digital signal in a small memory bag such as a memory card equipped with a semiconductor memory that can be driven at high speed, it is possible to correspond to continuous shooting of a subject within a short period of time.

In addition to this, an electronic still camera designed to improve the shooting speed is disclosed in Japanese Patent Laid-Open No. 10784/1984.

It is disclosed in JP-A-64-81583, JP-A-1-149575, etc.

[Problems to be Solved by the Invention] By the way, it is not possible to arrange a plurality of dynamic RAMs with fast writing speeds in parallel on the input side of bubble memories, E2FROMs, etc., which have large storage capacities but slow writing speeds. ,
The above-mentioned Japanese Patent Application Laid-Open No. 63-1999 discloses a structure in which a write memory selection circuit is arranged in the front stage of this dynamic RAM, and a read memory selection circuit is arranged in the rear stage to correspond to the continuous shooting mode.
The digital still camera described in No. 64485 requires an amount of dynamic RAM corresponding to the number of continuous shots, which increases the cost.

In addition, the above-mentioned Japanese Patent Application Laid-Open No. 62-26958 compresses the information amount of an image signal using a high-efficiency image encoder and then records it in a semiconductor memory such as SRAM that can be driven at high speed.
In the electronic still camera described in No. 1, no matter how much information is compressed, a semiconductor memory that can be driven at high speed and has a memory capacity corresponding to the number of continuous images is required as an external memory, which still increases the cost. .

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems and to enable the shooting of a large number of frames in continuous shooting mode while using a memory means that requires writing image information at a relatively low speed. To provide electronic still cameras.

[Means and operations for solving the problems] The electronic still camera of the present invention sequentially stores sequential image data obtained by an imager in the memory means described in Section 1, which requires writing at a relatively low speed. The electronic still camera has a compression means for compressing sequential image data from the imager, and a data transmission path from the output side of the compression means to the input side of the first memory means. a second memory means inserted therein and configured to perform a write operation at a relatively high speed and a data read operation at a speed compatible with the write operation speed of the first memory means;
It is characterized by comprising the following.

[Example] The present invention will be specifically described below with reference to the drawings. 1st
FIG. 1 is a block diagram of an electronic still camera showing an embodiment of the present invention. In the figure, an optical system 1 is drive-controlled by an optical system drive section 2 so that subject light transmitted through the optical system 1 is imaged on the imaging surface of a solid-state image sensor 3. The video signal photoelectrically converted by the image sensor 3 is
The signal is sampled and held by an S/H (sample and hold) circuit 4, and converted into a digital signal by an A/D converter 5.
The image information is temporarily stored in a buffer memory 6 that temporarily stores image information for one screen to be photographed. Note that the solid-state imaging device 3. The S/H circuit 4° A/D converter 5 is controlled by an imaging system driving section 10 that controls the driving timing of this imaging system.

Regarding the encoding technology for encoding the digital data of the video signal for one screen of still images developed on the memory area of the buffer memory 6 in the compression circuit 7 to compress the band and reduce the amount of transmitted information, for example, ADCT
tive Discrete Costne T r
There are various methods, including "Trends in Still Image Coding Technology," written by Hiroshi Ochi and published at the 18th Image Engineering Conference in 1987, so their explanation will be omitted here.

The digital data band-compressed by the buffer memory 6 and compression circuit 7 is stored in a continuous shooting memory 8, such as SRAM, which has a fast writing speed and has a memory capacity corresponding to the desired number of snapshots. Ru. In this case, if the compression means composed of the buffer memory 6 and the compression circuit 7 performs band compression using the ADCT method, the amount of transmitted information can be compressed to 1/10 to 1/20. The memory capacity of the memory 8 can be made small. On the other hand, if the memory capacity of the continuous shooting memory 8 is set to be the same as the memory capacity of the buffer memory 6, continuous shooting recording of 10 to 20 screens becomes possible in the continuous shooting mode.

The digital data read from the memory 8 is, for example, E
Data is recorded in a low-speed write memory 9, which is an external recording memory element with a slow write speed, such as a 2PROM, at a speed suitable for the write operation speed of the memory 9. The operations of the buffer memory 6 to low-speed write memory 9 are controlled by a memory control section 11 that controls the operations of these memories.

The memory control section 11 sends and receives signals to and from the system control section 12, which controls the sequence control of the entire system, and issues instructions to permit or disallow photographing operations. The system control unit 12 also controls the drive control of the optical system drive unit 2 and the imaging system drive unit 10, and also exchanges signals with an operation display unit 13 that monitors and displays various operations and operating states of the camera. It is designed to give and receive.

The continuous shooting operation in this embodiment configured in this way is
The process will be explained below using the flowchart shown in the figure. When power is supplied to the camera system and this flow starts, the system control unit 12 (see Figure 1) determines whether the continuous shooting mode and continuous shooting speed setting unit 14 is in continuous shooting mode or in single shooting mode. Go see what's going on (Step Sl).

If it is the single-shot mode, the process advances to step S2 and waits until the trigger switch is turned on. When the trigger switch is turned on, normal single-shot shooting is performed (step S3), and the main flow of camera operation (Fig. (not shown).

Returning to step S1, if the system control unit 12 determines that the continuous shooting mode and continuous shooting speed setting unit 14 is set to continuous shooting mode, the process proceeds to step S4, where the quick shooting memory 8 (see FIG. 1) It is determined whether the number of frames remaining is equal to or greater than a predetermined value.

In this case, when the compression rate is constant and the memory usage per screen is constant, the number of remaining frames can be determined from the remaining memory capacity, but
If the compression rate is varied depending on the screen, the amount of memory used will change depending on the screen being photographed, so the number of remaining frames will change. Therefore, when the compression ratio is made variable depending on the screen, the number of remaining shots that can be taken is estimated from the average data amount per screen and the remaining memory capacity.

If the number of remaining frames in the snapshot memory 8 does not reach the predetermined value,
Proceeding to step S5, a warning/display is performed on the operation display section 13, and the mode returns to single-shot mode (step S6). On the other hand, if the number of remaining frames in the continuous shooting memory 8 is equal to or greater than the predetermined value in step S4, the process advances to step S7 and waits until the trigger switch is turned on. When the trigger switch is turned on, the process advances to step S8, and the first frame of continuous shooting begins.

That is, the system control section 12 shown in FIG. 1 drives and controls the optical system drive section 2 to form a subject image on the imaging surface of the solid-state image sensor 3. Furthermore, the system control unit 12 drives the imaging system drive unit 10, sends image information for one screen to the A/D converter 5 via the S/H circuit 4, and converts the digital signal output from the converter 5 into is written into the buffer memory 6. Then, the memory control section 11 notifies the system control section 12 that one screen's worth of image information has been stored in the buffer memory 6. The digital data band-compressed by the buffer memory 6 and the compression circuit 7 is stored in the continuous shooting memory 8.

When the shooting of the first screen in continuous shooting is completed in this way, the process advances to step S9, and the process waits for the set quick shooting timing. The continuous shooting timing waiting time is
It is determined by the continuous shooting mode, the continuous shooting speed set by the continuous shooting speed setting section 14, and the time required for compression per screen. When the set continuous shooting timing wait is performed, step S9
The process advances to ' and checks for empty space in the buffer memory 6.

That is, when one screen worth of digital data is stored in the buffer memory 6 during snapshot shooting, and image information band-compressed by the compression means consisting of the memory 6 and the compression circuit 7 is stored in the continuous shooting memory 8, the above-mentioned The memory area of the buffer memory 6 becomes vacant and can accommodate the next continuous shooting. However, the time required for this band compression is approximately 1.00 m5 per screen tooth when an encoding technique such as the above-mentioned ADCT is used. In other words, the speed of snapshots is limited by the compression time in the compression means. Therefore,
During this 100rnS period, unless the next frame is prohibited in continuous shooting mode, the image information of the first frame will overlap with the image information of the next frame in the memory area of the buffer memory 6. Become. Therefore, from the memory control unit 11 to the system control unit 1
2, information is transmitted as to whether or not the buffer memory 6 is free. In this case, the time required for band compression in the compression means is stored in the system control section 2, and the continuous shooting timing is set using this and the continuous shooting mode and continuous shooting speed setting section 14. In other words, the process is executing the process of "waiting for the continuous shooting timing set in step S9."

Proceed to step S10 to check whether there is a remaining number of frames, and perform the above steps S8 to SIO until there are no remaining frames.
Execute continuous shooting mode. If there are no more frames left, the shooting is stopped (step 511) and the process returns to the main flow.

When a series of quick shots are completed in this way, the series of image information in the continuous shooting mode stored in the continuous shooting memory 8 is
For example, the data is transferred to the electronic still camera at a speed suitable for the writing speed of the low-speed writing memory 9, such as E2FROM, which is connected to the electronic still camera through a connector connection or the like.

Note that the low-speed write memory 9 is the first memory means in the claim, and the continuous shooting memory 8 is the second memory means,
Each corresponds to the other.

By the way, in the above embodiment, E is used as a low-speed write memory.
Although the description has been made using the example of a 2FROM, the present invention is of course applicable to recording media with slow writing speeds, such as magnetic disks, magnetic tapes, magnetic cards, magneto-optical disks, etc., without being limited thereto. Furthermore, in the above-described embodiment, the buffer memory 6 and the quick-shot memory 8 are configured as separate memories, but the buffer memory 6 and the continuous-shot memory 8 are configured as one large-capacity memory, and the memory controller 11 It goes without saying that the present invention can also be applied to cases where control is performed using

[Effects of the Invention] As described above, according to the present invention, after the image information is band-compressed, the image information is written once into the second memory means, which has a small memory capacity but can be written at a relatively high speed. Therefore, even in an electronic still camera having a first memory means that requires writing image information at a relatively low speed, continuous shooting of a large number of frames is possible. In addition, while it is possible to set the desired continuous shooting speed according to the movement of the subject, the setting range is limited so that it does not exceed a value that is compatible with the data compression speed, so the screen will be distorted when the next data is imported during the compression operation. This has the remarkable effect of making it possible to always take continuous shots of a good screen.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an electronic still camera showing an embodiment of the present invention, and FIG. 2 is a flowchart of continuous shooting operations in the embodiment.

Claims (2)

[Claims] (1) An electronic still camera configured to sequentially store sequential image data obtained by the imager in the first memory means, which requires an operation of writing at a relatively low speed, wherein the sequential image data obtained by the imager is sequentially stored in the first memory means. a compression means for compressing data; and a compression means inserted in a data transmission path from the output side of the compression means to the input side of the first memory means, and capable of performing a writing operation at a relatively high speed and the first memory means. an electronic still camera comprising: second memory means configured to perform a data read operation at a speed compatible with the write operation speed of the electronic still camera. (2) An electronic still camera configured to sequentially store image data obtained by an imager in the applied memory means via an image data compression means, wherein the image data is sequentially stored in the memory means. 1. An electronic still camera comprising continuous shooting speed setting means that allows the repetition frequency of the storage operation to be variably set within a range that does not exceed a value compatible with the data compression speed of the compression means.