JP3143159B2 - Image recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus,
In particular, the present invention relates to an image recording apparatus that performs highly efficient compression processing while maintaining the image quality of a subject image.

[0002]

2. Description of the Related Art For example, in an IC card camera,
The optical image is converted into an electric signal and a digital signal and recorded in an IC card memory. At the time of reproduction, an image signal read from the IC card memory is reproduced to obtain an optical image. In such an IC card camera, a large amount of data has to be recorded in order to record a large number of subject image data in one IC card memory, and the IC card memory is expensive. Highly efficient image data compression processing is performed. Normally, data is compressed by performing an orthogonal transformation process such as a discrete cosine transformation, and the obtained transformation coefficient is recorded in an IC card memory.

[0003] The amount of data after compression is greatly affected by high frequency components of the original image. If the high frequency component is large, the data amount after compression is large, and if the high frequency component is small, the data amount after compression is small. Since the actual subject image (original image) cannot be assumed in advance, the amount of data after compression varies depending on the subject image when actually recording. Therefore, the number of images (number of frames) that can be recorded in one IC card memory
However, when one frame is erased or the like is not known in advance, there is a problem in terms of usability, for example, it may not be possible to newly record all of one unit of image data in the erased portion.

Therefore, the compression processing is performed by changing a quantization table (hereinafter, referred to as a Q table) indicating a degree of compression and a mode until the data amount after compression of the image of each frame becomes equal to or less than a predetermined value. Is repeated, and recording is performed. However, in the method of recording by repeatedly performing compression processing while changing the Q table, the number of times of repeated compression processing required until the data amount after compression becomes equal to or less than a predetermined value is not determined, and it takes time to record, and However, there is a problem that the image quality is greatly reduced due to the reduction in the data amount of the data. In addition, the fact that it takes time until the recording is completed causes a problem that high-speed continuous shooting of camera shooting becomes impossible.

In order to solve these problems, the present inventor has determined a Q table that determines a compression mode based on contrast information of an image, and performs compression and recording processing according to the obtained Q table, thereby achieving high-speed compression and recording. We have proposed an image recording device that can be used.

[0006]

As described above, the conventional image recording apparatus performs a compression process on each image while changing the Q table until the data amount after compression reaches a predetermined value or less. The compression process is performed according to a Q table determined based on the contrast information of the image. However, increasing the compression ratio is beneficial in terms of storage capacity, but inevitably causes a decrease in image quality.

In order to solve this problem, for example, the contrast information and the distance information of the object are obtained by an automatic focus detection device of a separate focus detection system which is arranged separately from the taking lens as disclosed in Japanese Patent Laid-Open No. 2-105686. In some cases, the activity of an image is detected, the activity of the image is calculated based on the detection, the fineness of the image is determined, and the normalized count for image compression is obtained from a look-up table. By the way, contrast data representing a value corresponding to the sharpness of an image is
It is known that a completely different value is taken depending on the degree of focusing of the taking lens. Therefore, the image to be captured and stored in the recording medium and the image for obtaining the contrast information of the subject are defined as a region in which the two subjects are viewed and the degree of focus of both images. If they do not match, correct contrast information of the image to be stored on the recording medium cannot be obtained. Therefore, when contrast is to be obtained by an optical system different from the taking lens as disclosed in Japanese Patent Laid-Open No. 2-105686, the same optical system as the taking lens and an imaging device used only for focusing control are combined, or There is no way to obtain contrast information using either a combination of a very short focus lens of the formula and an imaging device,
In the former case, a two-lens type expensive imaging optical system is required, and in the latter case, in order to obtain image information with a sufficient resolution, a high-pixel image sensor must be used. In any case, the detected image cannot avoid the difference in the parallax and the field of view from the subject to be photographed. There was an inconvenience to get. As described above, conventionally, it has not been considered to distinguish a subject as a subject that desires high image quality according to a photographer's intention and obtain a target image to be photographed at a more appropriate compression ratio. Accordingly, an object of the present invention is to provide an image recording apparatus capable of obtaining contrast information most corresponding to an image immediately before recording, and recording image data with high efficiency while minimizing deterioration in image quality with a minimum amount of data. It is in.

[0008]

In order to solve the above-mentioned problems, an image recording apparatus according to the present invention comprises an image pickup device for photoelectrically converting a subject image to generate an image signal for recording, and an output signal of the image pickup device. Contrast signal forming means for obtaining a contrast signal representing the sharpness of an image on the basis of: a lens driving means for starting operation by a trigger signal and controlling focusing of a lens by a contrast value of the contrast signal forming means; Area setting means for setting a subject portion for obtaining a contrast value for image processing, compression processing means for orthogonally transforming and compressing an image signal based on a subject image, and the contrast value upon completion of focusing by the lens driving means Compression degree setting means for setting a quantization table representing the degree of compression for the compression processing using It applied to 択的 constituted by comprising: a signal compression means for performs a compression process of the image signal is output as a recording image signal.

[0009]

According to the present invention, a lens for forming a subject image on an image sensor for generating an image signal for recording includes at least a subject portion of the image signal obtained when focusing on the image sensor is completed. Is used to form a contrast signal, and a quantization table for compression is adaptively set based on the sharpness of the contrast value.

[0010]

Next, the present invention will be described with reference to the drawings. According to the present invention, an image to be recorded is divided into a plurality of areas, an area including a subject portion in which image quality degradation is particularly desired to be selected is selected, and a Q table is determined based on contrast information of the selected area. The image is compressed and recorded according to the obtained Q table.
For example, in an IC card camera, an area to which the user wants to take a picture belongs is determined and selected based on contrast data or the like among a plurality of areas, or the user manually selects the area and obtains the contrast information of the selected area. The entire image is subjected to compression processing and recorded based on it.

The subject area can be determined, for example, as follows. That is, the priority area selection of the auto focus (AF) of the camera includes a case where the user selects the area at the time of shooting and a case where the apparatus itself estimates the luminance information (contrast information) obtained for each area. For example, when the center and the lower part of the subject are dark and the upper part is bright, it is recognized that the subject is backlit, and it can be determined that there is a subject (a person or the like) at the center.

Thus, when the subject area is recognized,
By reading the contrast value of the area, the degree of the high frequency component with respect to the image of the area including the subject can be determined. Therefore, when there are many high-frequency components, the image quality decreases when the compression ratio is increased. Conversely, when the high-frequency components are small, the image quality is relatively small even when the compression ratio is increased, so that the storage capacity is small. It is effective in saving money. Therefore, if the user wants to capture a subject as a subject with a large number of high-frequency components, the overall compression ratio is reduced to suppress a decrease in image quality. If the subject area has a small number of high-frequency components, the overall compression ratio is increased and compressed. Process and record.

FIG. 1 is a flowchart showing an operation procedure of an embodiment relating to the application of an image recording apparatus according to the present invention to an IC card camera. In the shooting standby state,
The operation waits until the trigger 1 (TRG1) button is pressed "ON" (step S1). When the button is turned "ON", the imager AF operation is started (step S2) and the AF is started.
Contrast value for each area is detected (step S
3). Thereafter, it is determined whether or not the focus is OK (step S4). If not, the AF motor is operated (step S5), and the process returns to step S3. Step S4
If the focus is OK, an appropriate Q table is selected based on the contrast value of the AF selection area (step S6), and the selected Q table is transferred to the compression circuit (step S7). Further, it waits until the trigger 2 (TRG2) button is turned “ON” (step S8),
At the time when it becomes N ", the recording operation to the memory is performed (step S9).

For example, as shown in FIG. 2 (A), one screen for photographing is divided into 9 areas, and the contrast value of each divided area is stored in a RAM built into the CPU of the IC card camera body as shown in FIG. 2 (B). AFD, AFD,..., AFD are stored. Here, if the AF selection area is an area, the AFD of the RAM is read, the value of the Q table is obtained based on the read contrast value, and the value is transferred to the compression circuit to perform a compression process. Here, when obtaining the Q table, if the AF selection area is
The value of the Q table can be obtained by using D as it is, giving priority to AFD, and referring to the contrast values of other areas and using the weighting value. Q table is
It is prepared in advance for each of a plurality of contrast values.

Next, a case where the present invention is applied to an image as shown in FIGS. 3A and 3B will be described as an example. When the entire high-frequency component is extracted from the image (A) alone, the background tree and the mountain have many very fine parts, and thus the high-frequency component increases. However, in this case, the user wants to photograph the central person, and since the human portion has relatively few high-frequency components, if the central part is selected as the AF area selection, Q is determined based on the contrast value of the central part.
By determining the table, recording with a relatively high compression ratio can be performed. When simply extracting the entire high-frequency component from the image (B), the number of high-frequency components is reduced because the number of peaks is small. In this case, since the user wants to photograph the left mountain, a detailed expression is required.
Here, if the mountain area on the middle left is selected as the AF area selection, Q is determined based on the contrast value of the middle left.
By determining the table, recording is performed with a relatively low compression ratio, and detailed expressions are not lost. The area division of one image may be a rectangular area division as shown in FIG. 10C or a concentric rectangular area division as shown in FIG.

FIG. 4 is a block diagram of the entire camera when the present invention is applied to an IC card camera. In FIG. 4, a subject image formed on a CCD 2 via a lens 1 is converted into an electric signal, and then converted into an electric signal.
A predetermined process such as correction is performed, and the A / D converter (AD
C) It is converted into a digital signal in 4. Signal generator (SS
G) The circuit 17 is a circuit for generating signals for controlling the CCD 2, the imaging process circuit 3, and the A / D converter 4. The video signal from the imaging process circuit 3 is
The information is supplied to the control circuit 18 and contrast information is obtained. The obtained contrast information is transmitted to the system control circuit 12.
Supplied to Further, based on the contrast information, the lens drive circuit 19 performs AF control to focus the lens 1. The selector 5 sets a path for recording digital image data from the A / D converter 4 in the RAM 6 during recording. The block data read from the RAM 6 (data on each divided block when one screen is divided into a plurality of blocks) is supplied to the compression / decompression unit 8 via the selector 7. Compression / expansion unit 8
DCT / IDCT circuit 81 is a discrete cosine transform / inverse discrete cosine transform circuit, and performs an orthogonal transform process on block data. The transform coefficients obtained by the orthogonal transform are quantized by a quantization / dequantization circuit 82 and then encoded by an encoding / decoding circuit 83.

Processing such as encoding in the compression / decompression unit 8 is controlled by an encoding control circuit 13 based on an instruction from a system control circuit 12. That is, based on the contrast information supplied from the lens / AF control circuit 18, the system control circuit 12 selects and sets an appropriate Q table, and performs compression / compression via the encoding control circuit 13.
The compression processing in the expansion unit 8 is controlled. here,
The selection of the Q table is performed by operating an area selection key provided on the operation unit 14 to select a subject area from the area displayed on the monitor or the viewfinder, or to select contrast information from the lens AF control circuit 18. This is performed by selecting the subject area based on the above-described method. . The image data compressed and encoded by the compression / decompression unit 8 is supplied to the card interface (I / F) 10 via the selector 9.
It is recorded on the IC card 11. System control circuit 12
Are RAM 6, selectors 7, 9 and compression / expansion unit 8
And controls the operation of the card I / F 10, and performs various controls of the entire camera in response to a signal from the operation unit 14.

FIG. 5 shows contrast information detection and A
The block diagram of the configuration of the F control system is shown. The video signal from the imaging process circuit 3 is supplied to an output terminal connected to the A / D converter 4 and the lens / AF
Bandpass filter (BPF) circuit 18 of control circuit 18
1 is supplied. The BPF circuit 181 extracts a predetermined band signal of the video signal, converts the luminance information into a digital signal by the A / D converter 182, and converts the luminance information into a digital signal.
Is output to The arithmetic processing circuit 183 obtains contrast information from the digital signal, and obtains the system control circuit 12
And to a motor drive circuit 192 constituting the lens drive circuit 19. The motor drive circuit 192 drives the motor 191 to move the lens 1 to perform AF control based on the contrast information.

FIG. 6 shows the relationship between the image and the contrast. In the figure, hatched portions indicate dark portions. The change in the luminance signal of the image (A1) with little change is as shown in (A2). When this luminance signal is passed through a band-pass filter, it becomes a signal as shown in (A3). This is double-wave rectified to obtain a signal (A4) and then integrated to obtain a DC level signal as shown in (A5). For an image with little change, such as the image (A1), the level difference from the reference level (dotted level) is small. On the other hand, the luminance change for an image having a large change like (B1) is as shown in (B2), and the signal of (B3) is obtained by passing through a band-pass filter. After performing the both-wave rectification to obtain the signal (B4), the signal is integrated to obtain the signal (B5). The difference from the reference level at this time is large.

As described above, an image having a small level of the final contrast value is an image with little change, and the data amount after compression is small. An image having a large contrast value level is an image having a large change, and the data amount after compression becomes large. Therefore, when the contrast level is large, the data amount can be reduced by using the value of the Q table having a high compression ratio. In this embodiment,
The contrast value is determined based on the level of the integrated value, but may be determined based on the pulse height or the number of pulses of the luminance signal. In addition, the present invention is not limited to the IC card camera, but can be applied to other recording apparatuses that perform image compression processing.

[0021]

As described above, in the image recording apparatus according to the present invention, the lens for forming the subject image on the image sensor for generating the image signal for recording is obtained when the focusing on the image sensor is completed. Since a contrast signal is formed by using at least a subject portion of the obtained image signal, and a quantization table for compression is adaptively set based on the sharpness of the contrast value, a more actual Compression according to the photographer's intention can be performed according to the image information at the time of recording, and high quality image quality can be maintained as a whole.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an operation processing procedure showing an embodiment of an image recording apparatus according to the present invention.

FIG. 2 shows a divided area of an image according to the embodiment of the present invention;
FIG. 7 is a diagram illustrating a storage mode of a contrast value of each divided area.

FIG. 3 is an operation explanatory diagram of two image examples to which the present invention is applied;

FIG. 4 is an overall configuration block diagram of an IC card camera to which the present invention is applied.

FIG. 5 is a configuration block diagram of a contrast information extraction and AF control unit according to the embodiment of the present invention.

FIG. 6 is a diagram illustrating a change in contrast information for an image having a small change and an image having a large change.

[Explanation of symbols]

1 lens 2 CC
D 3 imaging process circuit 4 A /
D converter 5, 7, 9 selector switch 6 RA
M 8 compression / decompression unit 10 card interface circuit 11 IC card memory 12 system control circuit 13 encoding control circuit 14 operation unit 15 reproduction process circuit 16 D /
A converter 17 Signal generation circuit 18 Lens / AF control circuit 19 Lens drive circuit

Claims (1)

(57) [Claims] (1)Image signals for recording by subjecting the subject image to photoelectric conversion
An image sensor that generates a signal; Represents the sharpness of the image based on the output signal of the image sensor
Contrast signal forming means for obtaining a contrast signal; Operation is started by a trigger signal and the above contrast signal
Focus control of the lens by the contrast value of the forming means
Lens driving means; Subject for obtaining the contrast value for the focus control
Area setting means for setting a section, Compression for orthogonally transforming and compressing image signals from the subject image
Processing means; The contra when the focusing by the lens driving means is completed.
A quantity representing the degree of compression for the above compression process using the strike value
Compression degree setting means for setting a child table; By selectively applying the above quantization table, the
For performing compression processing and outputting it as a recorded image signal
Signal compression means; Equipped with An image recording apparatus, comprising: