JP3115912B2 - 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 compresses and records image data with high efficiency while minimizing deterioration of image quality with a minimum data amount.

[0002]

2. Description of the Related Art When digital image data is recorded in a memory, the amount of recorded image data is enormous, so that not only does the storage of the memory and transfer of the image data impose a burden on hardware, The transfer time becomes longer. Therefore, compression processing is usually performed on image data, and the compressed image data is recorded and transferred to a memory. For example, such an image compression technique has recently been adopted in an IC card camera for recording an optical image of a subject in an IC card memory instead of a silver halide film. IC
In a card camera, after an optical image is converted into an electric signal or a digital signal, orthogonal transformation processing such as discrete cosine transformation or the like is performed to perform data compression, and the obtained conversion coefficient is recorded in an IC card memory. In data compression in a conventional image recording device such as an IC card camera, a predetermined compression process is performed on the entire image to be recorded, and the amount of compressed data is reduced to a certain value or less.

[0003]

As described above, the conventional image recording apparatus performs a predetermined compression process on the entire image to be recorded. The image quality deteriorates as the compression ratio for compressing the image data increases. On the other hand, the recording object (for example,
The fineness of the subject image) varies widely, and when the original image (subject image) contains fine information, increasing the compression ratio causes a significant deterioration in image quality, which may make it unusable for practical use. On the other hand, when the original image contains only coarse information (that is, in the case of a picture having a relatively flat change), the original image information can be reproduced to a satisfactory degree even at a low compression ratio. However, the conventional image recording apparatus performs a predetermined orthogonal transformation process regardless of the fineness or coarseness of the original image, and repeats the process until the data amount after compression becomes equal to or less than a certain value. By the way, if the whole original contains only detailed information,
There are few cases in which only coarse information is included, and in general, fine information and coarse information are often mixed in one original image. In such a case, if a fixed compression process is performed as in a conventional image recording apparatus, if the optimal compression process for fine information is performed on coarse information, the coarse information is useful from the viewpoint of image quality. Compression processing is performed. Conversely, if the optimal compression processing for coarse information is performed on fine information, there is a problem that the image quality is greatly deteriorated. To solve this problem, for example,
As disclosed in Japanese Patent Application Laid-Open No. 2-105686, contrast information and distance information of a subject are detected by an automatic focus detection device of a separate focus detection system arranged separately from a photographing lens, and image activity is calculated based on the information. , The fineness of the image is determined, and a normalization coefficient for image compression is obtained from a look-up table. On the other hand, it is known that contrast data representing a value corresponding to the sharpness of an image takes a completely different value depending on the degree of focusing of a photographing lens. In other words, a focus detection method called a so-called contrast method is such that a focus operation is performed by photoelectrically detecting that the contrast value becomes maximum during focusing. On the other hand, a conventional Japanese Patent Laid-Open No. 2-105
When a contrast value is obtained by a method having an optical system separate from the photographing lens as in 686, the same optical system and photographing device as the photographing lens are combined, or a very short focus lens of pan focus type and a photographing device are used. There is no way to get contrast information using one of the combinations,
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 field of view from the subject to be photographed, and in a photographing situation where the parallax becomes large such as macro photography, accurate contrast information is obtained. Was inconvenient to obtain.

Accordingly, an object of the present invention is to provide an image recording apparatus capable of obtaining contrast information that best corresponds to an image immediately before recording, and recording image data with a minimum amount of data and minimizing deterioration in image quality and with high efficiency. It is to provide a device.

[0005]

In order to solve the above-mentioned problems, an image recording apparatus according to the present invention photoelectrically converts a subject image formed on an image pickup device via a lens, and based on this photoelectric conversion signal. Contrast signal forming means for obtaining a contrast signal representing the sharpness of an image, 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, and an image signal based on a subject image. Compression processing means for performing orthogonal transformation and compression processing, and compression degree setting means for setting a quantization table representing a compression degree for the compression processing using the contrast value at the time of completion of focusing control by the lens driving means When the contrast value indicates a state of relatively high sharpness, the contrast value of a relatively low compression ratio is Signal compression means for selectively applying a relatively high compression rate quantization table when indicating a state of low target sharpness, performing image signal compression processing and outputting as a recorded image signal. Are provided.

[0006]

According to the present invention, as described above, one image is divided into a plurality of sections (areas), contrast information indicating the sharpness of the image for each divided area is obtained, and based on the obtained contrast information. By setting a quantization table having an appropriate compression ratio in the divided area, an optimal compression process is performed for each divided area of one screen, thereby enabling reproduction of high quality images with a minimum amount of data.

[0007]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing an operation processing procedure in an embodiment of an image recording apparatus according to the present invention, and shows an application example to an IC card camera. In this embodiment, when recording a digital image signal obtained from an imaging system, one screen is divided into a plurality of areas, and the sharpness of an image obtained for each area by an imager AF (autofocus) operation is determined. By setting a quantization table (hereinafter, referred to as a Q table) indicating a degree of compression and a mode when performing compression processing for each divided area on the basis of the represented contrast data as an optimal table and performing compression processing, Deterioration of the overall image quality is minimized while minimizing the overall data amount. Also, in the imager AF process, since the contrast value representing the fineness of the original image is calculated for each AF area, the compression ratio of each area is set based on the calculated value, and the compression is performed individually to improve the image quality. Efficient compression is possible while suppressing the decrease.

Referring to FIG. 2, one screen of a subject is divided into nine areas as shown in FIG. 2A, and when the AF operation is completed, as shown in FIG. On the memory, contrast values AFD to AFD for each area are recorded. The CPU, based on the contrast values AFD to AFD, sets an optimum Q table (QT) for each contrast value for each area.
ABLE) to Q table are selected and transferred to the compression processing circuit. FIG. 3A shows an example of the arrangement of the divided areas to the Q tables set for the respective divided areas. The division mode of each division area in (A) is shown in (B), but the division of the area can be determined as in (C), and the division state is arbitrary.

The operation of the present embodiment will be described with reference to FIG. 1. First, in the photographing standby state, the system waits until the trigger 1 (TRG1) button is pressed "ON" (step S1). When "ON", the imager AF operation is started (step S2), and a contrast value for each AF area is detected (step S3). Thereafter, it is determined whether or not the focus is OK (step S4).
If it is not K, the AF motor is operated (step S
5), the process returns to step S3. If the focus is OK in step S4, an appropriate Q table is calculated based on the contrast value of the AF selection area (step S4).
6), the number n of the divided area is set to "1" (step S7). Next, a Q table for the AFn (n = 1) area is calculated (step S8), and the obtained Q table is set in the compression circuit (step S9). Then, it is determined whether or not n matches the total number N of the divided areas. Is determined. Here, if they do not match, in order to set an appropriate Q table for the next area, n = n + 1 (step S11), and the process returns to step S8. In step S10, n = N
Is determined, it is determined that the setting of the appropriate Q table has been completed for all the divided areas in one screen,
It is determined whether or not the next trigger 2 (TRG2) is "ON" (step S12). The determination in step S12 is “ON” in a state where the trigger 2 is waiting
Then, compression and recording operations are performed (step S13).

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.

The 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 for each divided area supplied from the lens / AF control circuit 18, the system control circuit 12
Selects and sets an appropriate Q table for the divided area as described above, and controls the compression processing in the compression / decompression unit 8 via the encoding control circuit 13. The image data compression-encoded by the compression / decompression unit 8 is supplied to the card interface (I / F) 10 via the selector 9 and recorded on the IC card 11. The system control circuit 12 includes a RAM 6, a selector 7,
9. The operation of the compression / expansion unit 8 and the card I / F 10 is controlled, and various controls of the entire camera are performed 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 outputs the digital signal to the arithmetic processing circuit 183.
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 controls the lens 1 by driving the motor 191 to perform AF control based on the contrast information.
The AF operation is performed.

In the above-described embodiment, an example has been described in which one screen is divided into a plurality of areas in an arbitrary manner. However, in normal compression, compression processing is performed on 8 × 8 blocks of pixels. Since compression is performed, the compression processing can be facilitated if the AF divided area is also configured in integer multiples of 8 × 8 blocks. Since the processing at the boundary between the areas becomes complicated unless the unit is set to an integral multiple, the boundary is set to the compression processing in accordance with the pixel block to facilitate the processing. Also, as shown in FIG. 6, the compression can be performed by compressing each block of 8 × 8 pixels in the horizontal direction. The present invention is not limited to a digital camera such as the above-described IC card camera. When compressing and recording the video signal of the original image, the original image may be divided into a plurality of areas, and a contrast value may be obtained for each divided area. Of course, it can be applied to other various image recording apparatuses.

[0014]

As described above, in the image recording apparatus according to the present invention, the contrast signal is obtained from the image signal obtained when the lens for forming the subject image on the image sensor is completed (attained). Is formed, and a quantization table for compression is adaptively set based on the sharpness of the contrast value, so that compression in accordance with image information at the time of actual recording becomes possible, and a high-quality image as a whole is obtained. Image quality can be maintained.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an operation processing procedure of an embodiment of an image recording apparatus according to the present invention, showing an example of application to an IC card camera.

FIG. 2 is a diagram showing a relationship between divided area contrast information and a corresponding Q table in an embodiment of the image recording apparatus according to the present invention.

FIG. 3 is a diagram showing a relationship between a divided area and a Q table and a division mode in the embodiment of the image recording apparatus according to the present invention.

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 showing another division mode in the embodiment of the image recording apparatus according to the present invention.

[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

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 5/76-5/956 H04N ^7/ 24-7/68 H04N 1/41-1/419

Claims (1)

(57) [Claims] (1)Object imaged on image sensor via lens
The body is photoelectrically converted, and the image is converted based on the photoelectric conversion signal.
Contrast signal to obtain contrast signal indicating sharpness
Signal forming means; Operation is started by a trigger signal, and the contrast signal
Focus control of the lens by the contrast value of the signal forming means
Lens driving means; The pressure at which the image signal of the subject image is orthogonally transformed and compressed.
Compression processing means; When the focusing control by the lens driving means is completed,
The degree of compression for the above compression processing is expressed using the trust value.
Compression degree setting means for setting a quantization table to pass; Indicates that the contrast value is relatively sharp.
In some cases, the contrast value of a relatively low compression ratio
When it indicates a state of relatively low sharpness
Selectively apply a high compression ratio quantization table to
Perform signal compression and output as recorded image signal
Signal compression means for  An image recording apparatus comprising: