JP3064948B2 - An electronic camera that can change the compression ratio of image information - 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 camera for recording an image as digital data, wherein the compression ratio of image information is variable.

[0002]

2. Description of the Related Art In this type of electronic camera, field / frame recording is set, and when the number of remaining tracks is smaller than the required number of tracks in a selected recording mode,
It is known to display a record disabled (for example, Japanese Utility Model Publication No. 5-43568). Further, there has been proposed an electronic still camera in which an IC memory card is used as a recording medium for recording image information, and the image information is compressed and recorded on the memory card. As a method of compressing image information, a discrete cosine transform (DCT) is adopted,
The orthogonal transform is performed on the input video signal, and compression is performed by reducing the number of bits allocated to each frequency component obtained as a result of the orthogonal transform.

[0003]

In the above-described electronic camera, when an image is compressed at a certain compression rate using the above-described compression method, the amount of data after compression differs depending on the type of image. (Variable length compression). Therefore, when the recordable capacity is determined like a memory card, the photographer cannot accurately grasp the remaining recordable number. Further, when a desired compression ratio can be selected from a plurality of compression ratios, it becomes more difficult to grasp the number of remaining shots. Furthermore, in the case where continuous shooting and single shooting are switched and selected, if continuous shooting is selected, the remaining capacity of the recording medium quickly runs out depending on the compression ratio setting. easy. In view of the above problems, the present invention can display the remaining number of recordable images to the photographer based on the set compression ratio and the usage status of a recording medium (for example, a memory card). It is an object of the present invention to provide an electronic camera which can prevent the remaining capacity of a recording medium from being quickly exhausted in such a case.

[0004]

To achieve the above object, the present invention provides an image pickup device for converting an optical image formed by an optical system into an electric signal, and a frequency characteristic of an output signal from the image pickup device. In an electronic camera including a compression processing circuit that performs compression in accordance with the compression processing, and a recording unit that records a compressed image signal on a recording medium, the compression rate of the signal in the circuit is changed by the arbitrary processing to the compression processing circuit. Compression ratio setting means for providing a signal to be set; selection means for selecting continuous shooting or single shooting; detection means for detecting the use state of the recording medium; and compression when the single shooting is selected by the selection means. According to the compression rate set by the rate setting means and the use state of the recording medium detected by the detection means,
When the continuous shooting is selected by the selection unit, the remaining recording is performed in accordance with a predetermined high compression ratio determined regardless of the setting by the compression ratio setting unit and the use state of the recording medium detected by the detection unit. An electronic camera including a display unit for displaying a possible number of images and capable of changing a compression ratio of image information. With this configuration, the remaining number of recordable images can be displayed to the photographer based on the set compression ratio and the usage state of the recording medium. In addition, switching between continuous shooting and single shooting can be selected. When continuous shooting is selected, the remaining number of recorded images is displayed at a predetermined high compression ratio regardless of the set compression ratio.
Note that, in the following embodiment, the process of detecting the use status of the recording medium corresponds to # 2 in the flowchart of FIG. 2, and the process of displaying the remaining recordable number is # 6 in the flowchart of FIG. # 7, # 19, # 20, # 21 in FIG.
Is equivalent to

[0005]

FIG. 1 is a block diagram of an electronic still camera according to an embodiment of the present invention. The imaging device 1 including a CCD sensor or the like converts an optical image formed through a lens L of an optical system into an electric signal. The analog circuit unit 2 including a CDS, an amplifier, and the like includes a reset noise elimination (CDS) of an output from the image pickup device 1 and an amplification (amplifier) so as to match a dynamic range of an input of an A / D converter 3 in the next stage. Has functions. The A / D converter 3
A signal output from the analog circuit section 2 and adjusted to match the dynamic range of the converter 3 is clamped and converted into digital data of about 8 to 10 bits. The video signal processing circuit 4 performs a matrix process after white balance and γ correction of the output of the imaging electric signal of the imaging device 1 converted into a digital signal by the A / D converter 3, and normalizes the output, for example, a luminance signal and a color difference signal. Create a digital video signal.

The compression processing section 5 compresses the output signal of the video signal processing circuit 4 at a compression rate set in advance from the outside and outputs it. The compression ratio can be changed by an external setting. Image compression is performed using, for example, orthogonal exchange (ADCT, Hadamard transform, etc.). That is, the input digital video signal is divided into blocks of, for example, 8 × 8, orthogonal transform is performed on each block, and coefficients are assigned to each frequency component obtained as a result of the orthogonal transform. Perform compression by reducing the number of bits. Also, the compression ratio can be changed by changing the way of reducing the number of allocated bits. Memory card 6 is E ²
It is composed of a nonvolatile memory such as a PROM or an SRAM and a backup battery, and stores video signal management / search information and video data. Access speed is 250nS about in the SRAM, the E ² PROM S
It's even slower than RAM.

The memory card interface unit 7 is roughly divided into a memory card 6, a CPU 8, and a memory card 6.
And a video signal processing circuit 4 and a compression processing unit 5. The former CPU interface is
A function required to record the video signal management / search information created by the CPU 8 at a designated location on the memory card 6, a function for the CPU 8 to read the information from the designated location on the memory card 6, and a state of attachment / detachment of the memory card 6. And a function of reading information about the card itself such as the type and capacity of the card 6 and a function of setting an address of the memory card 6 for writing video data. In the latter video signal processing / compression processing interface, when the compressed video signal compressed by the compression processing unit 5 is recorded on the memory card 6, the access time of the memory card 6 is slower than the slew rate of the video signal processing system. For this purpose, it has a buffer memory necessary for changing the writing speed, and a function of sequentially recording video data in the buffer memory to the memory card 6 from a video data write address set by the CPU 8.

The CPU 8 detects the state of each switch and controls the sequence of the camera. The CPU 8 creates video signal management / search information to be added when recording video data on the memory card 6. A task of allocating an area for writing video data based on the signal management data is performed. The timing generator 9 generates a timing signal for driving the image sensor 1 and a timing signal for performing A / D conversion. The LCD 10 displays the number of remaining shots, the compression mode, the shooting mode (single shooting or continuous shooting), etc., in order to convey camera information to the photographer. Release switch 1
1 indicates that the photometry / ranging switch S1 is turned on by half-press,
When fully pressed, the photographing switch S2 is turned on.

The continuous shooting / single shooting switch 12 is turned on.
To enter the continuous shooting mode, and to OFF to enter the single shooting mode. The compression ratio setting switch 13 has the setting value of this switch (non-compression, 1/2, 1/4, 1/8, 1
/ 16 compression). For example, when the discrete cosine transform (DCT) is adopted as the compression method, the compression processing unit 5 according to the value of this switch.
Changes the number of bits allocated to the high frequency component to change the compression ratio.

Next, the shooting operation in each mode of single shooting / continuous shooting according to the present embodiment will be described with reference to the flowcharts of FIGS. When the release switch 11 is half-pressed while the main power supply is ON (S1 ON) (YES in step # 1), the CPU 8 sends the image together with information such as the type and capacity of the card from the memory card 6 through the memory card interface unit 7. Read data management information (#
2). The management information of the video data has a format as shown in FIG. 5, for example. FIG. 3 shows the format of management information for one video. Based on this information, the CPU 8 creates memory map information of the empty space,
Calculate the free memory capacity. Next, the CPU 8 reads information of each setting switch (# 3), performs light metering to determine exposure information, and performs an autofocus operation for focusing (# 4). It is checked from the read switch information whether the camera is in the continuous shooting mode (# 5). If it is not the continuous shooting mode (NO in # 5), the compression ratio setting switch 1
3 is set in the compression processing unit 5 and the number of remaining shots is calculated from this value and the aforementioned free memory capacity.
Displayed on the counter of the number of remaining shots of 10 (# 6, #
7). At the same time, until the release switch 11 is depressed (S2 ON) (YES in # 8), the operation returns to # 3 and the operation from reading the information of each setting switch is repeated. If the value of 13 is changed, the set value to the compression processing unit 5 is changed, the number of remaining shots is calculated again, and the above display is changed.

When the release switch 11 is depressed (S2 ON), the power of the imaging system is started (# 9), and exposure control is performed using the electronic shutter function of the imaging device (CCD) 1 (# 10, #). 11). In addition, CPU at the time of exposure
Numeral 8 sets an address of the memory card 8 for recording the captured video data in the memory card interface unit 7 (# 12). After the exposure is completed, the data is read from the image sensor 1 and processed by the video signal processing circuit 4 (# 12). 13) For example, the data is sent to the compression processing unit 5 in the form of Y, RY, BY. The compression processing unit 5 performs, for example, compression using discrete cosine transform on each video data in advance.
The compression is performed at the compression rate set by the PU 8 to create compressed video data (# 14). This compressed video data is recorded on the memory card 6 through the memory card interface unit 7 (# 15). That is, the memory card interface unit 7 records the compressed video data from the address set by the CPU 8 and obtains the recording end address. After recording the video data, the CPU 8 records the recording start address and the final address together with the search information such as the date on the memory card 6 as the video management information (# 16, # 1).
7). After the end of all the recording operations, 1 is subtracted from the number of remaining shots and the value is displayed on the counter of the LCD 10 (# 18).

The above is the operation in the single shooting mode. Next, the operation in the continuous shooting mode will be described. When S1 is ON, if the continuous shooting mode is set (YES in # 5), the highest compression ratio (1/16 in the case of the embodiment of FIG. 1) is automatically selected regardless of the setting of the compression ratio setting switch 13. (# 19), LCD
10 displays the number of remaining shots and the compression ratio at that compression ratio (# 20, # 21). At this time, when the compression ratio setting switch 13 is operated, the compression ratio given by the operation is used, and a display suitable for the compression ratio is performed. S2
After the power is turned on (YES in # 22), the imaging operation, the reading of the imaging signal, the processing, the compression, and the writing operation to the memory card 6 are repeated (# 23), and 1 is subtracted from the remaining number of images to be displayed on the LCD 10. (# 24), continuous shooting is performed until the number of remaining shots becomes 0 or S2 is turned off (# 2).
5).

As described above, orthogonal transformation is used as a compression method, and image deterioration at a high compression ratio is reduced by changing a coefficient assignment bit for each frequency component as a variable compression ratio method. be able to. Further, by using predictive coding and subsampling as a compression method and changing the compression ratio by changing the number of bits of the difference and the sample rate of the subsampling, the circuit configuration can be relatively simplified. As a method of changing the compression ratio, there is a method of changing to a system having a different compression ratio. Also,
In order to select a high compression rate, for example, when there are three types of compression modes, a relatively high compression mode may be selected. Will be changed to

[0014]

As described above, according to the present invention, in an electronic camera capable of changing the compression ratio of image information to be recorded, the remaining amount is determined according to the set compression ratio and the detected use state of the recording medium. Since the recordable number is displayed, the photographer can accurately grasp the remaining recordable number. Further, continuous shooting and single shooting can be selected, and when continuous shooting is selected, the remaining number of recorded images is displayed using a predetermined high compression ratio or the like regardless of the set compression ratio. Therefore, it is possible to prevent the remaining capacity from becoming zero immediately.

[Brief description of the drawings]

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

FIG. 2 is a flowchart showing an operation of the camera.

FIG. 3 is a flowchart showing the operation of the camera.

FIG. 4 is a flowchart showing the operation of the camera.

FIG. 5 is a diagram showing a format of video data management information for one video in a memory card.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image sensor 4 Video signal processing part 5 Compression processing part (compression processing circuit) 6 Memory card (recording medium) 7 Memory card interface part (recording means) 8 CPU (detection means) 10 LCD (display means) 13 Compression rate setting switch (Compression rate setting means)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 5/222-5/257 H04N 5/76-5/956

Claims (1)

(57) [Claims] An image pickup device for converting an optical image formed by an optical system into an electric signal, a compression processing circuit for performing compression according to a frequency characteristic of an output signal from the image pickup device, and a compressed image signal the in electronic camera and a recording means for recording on a recording medium, by any operation, the compression ratio setting means to said compression circuit providing a signal for setting the compression rate of the signal in the circuit, continuous shooting and single Selecting means for selecting a photograph, detecting means for detecting the use condition of the recording medium, and detecting the compression rate set by the compression rate setting means and the detecting means when the single photographing is selected by the selecting means. According to the usage status of the selected recording medium.
The compression ratio setting when continuous shooting is selected by means
Predetermined high compression ratio determined regardless of setting by means
And the use condition of the recording medium detected by the detecting means.
An electronic camera capable of changing a compression ratio of image information, the display further comprising a display means for displaying a remaining recordable number in response to the request .