JPH11220690A - Electronic still camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make constant picture quality in each mode regardless of the kind of picture quality. SOLUTION: Picture data fetched from an inputting part are temporarily fetched in a frame memory 1, and compressed by a compressing/expanding part 2, and the compressed data are fetched in compression memories 3a-3n whose compression conditions are different. When the compression is ended, the compressed data are successively transmitted from each compression memory to the compressing/extending part 2, and data extended by the compressing/ extending part 2 are transmitted to a comparison arithmetic part 7. On the other hand, non-compressed picture data are transmitted through a buffer memory 6 to the comparison arithmetic part 7, and a picture quality evaluation value is calculated. When all the arithmetic operation is ended, an optimal compression condition is automatically judged by a control part (not shown in a figure). Afterwards, an instruction to select the compressed data is transmitted to a multiplexer 4, and the multiplexer 4 selects the instructed compressed data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic still camera, and more particularly, to a digital electronic still camera.
For example, the present invention can be applied to an image input device using an image sensor.

[0002]

2. Description of the Related Art FIG. 4 is a diagram for explaining an example of a general digital electronic still camera. As shown in FIG. The analog signal is processed, converted into a digital image signal by the A / D converter 14, and various signal processing is performed in the digital signal processing unit 15 thereafter, and the image data is stored in the memory 16. The monitor 17 displays an image obtained from an input unit such as a liquid crystal, and an image stored in the memory 16 is captured by a release button 18. Since the image data taken into the memory 16 as it is has a large data amount as it is, it is generally stored as compressed data. Further, since the memory 16 has a finite capacity, the user can select a mode such as high image quality, standard image quality, or low image quality according to the number of images to be taken.

[0003]

However, in the conventional mode selection, since the compression ratio in each mode is determined, there is a problem that the image quality differs depending on the type of image.

The present invention has been made in view of the above situation, and has an object to make the image quality in each mode constant regardless of the image quality type.

[0005]

According to a first aspect of the present invention, there is provided an optical lens for forming an image of reflected light from a subject, and an image pickup device for converting a subject image formed by the optical lens into an analog image signal. Digital electronic still comprising an imaging means, an analog signal processing means for processing an analog image signal, an analog / digital conversion means for converting an analog image signal into a digital image signal, and a digital signal processing means for processing a digital image signal In the camera, image quality is evaluated using uncompressed image data and image data obtained by expanding a plurality of compressed data, and the image data is stored as compressed data that can obtain a predetermined image quality without displaying an image. The image quality is evaluated using the compressed image data and image data obtained by expanding a plurality of compressed data, and a predetermined image is displayed without displaying the image. So as to save it as compressed data is obtained, any kind of image, in which to be able to obtain a constant image quality.

A second aspect of the present invention is characterized in that, in the first aspect of the present invention, compression and decompression are continuously performed in order to evaluate image quality, thereby eliminating a compression memory and reducing the capacity of the compression memory. By doing so, the size and cost can be further reduced.

According to a third aspect of the present invention, in the first aspect of the present invention, the image quality can be freely set by the user, and the image quality desired by the user can be freely obtained. .

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing a main part of an electronic still camera according to an embodiment of the present invention. First, image data taken in from an input unit (not shown) is temporarily stored in one frame. Stored in the memory 1. Next, the data in the one-frame memory 1 is compressed by the compression / decompression unit 2, and the compressed data is taken into the compression memories 3a to 3n. Here, a plurality of compression memories 3a to 3n are memories for taking in compressed data having different compression conditions. That is, for example, if compressed data having a relatively low compression rate is taken into the compression memory 3a, the compression memory 3b takes in the compressed data compressed under the compression condition having a higher compression rate than the compression data taken into the compression memory 3a. The compression memory 3c takes in compressed data having a higher compression rate than the compression memory 3b. Hereinafter, the data is similarly taken up to the compression memory 3n.

When the compression is completed, the compressed data is sequentially sent from each compression memory to the compression / decompression unit 2. The data expanded by the compression / expansion unit 2 is sent to the comparison operation unit 7. on the other hand,
The original uncompressed image data is sent from the one-frame memory 1 to the comparison operation unit 7 via the buffer memory 6. Here, an image quality evaluation value is calculated from the two data.
The calculated result is stored in the temporary evaluation value memory 9.
When all the operations are completed, the operation results are sent from the evaluation value memory 9 to a control unit (not shown), and the control unit automatically determines an optimal compression condition. Thereafter, a command for selecting compressed data is sent to the multiplexer 4, and the multiplexer 4 selects the instructed compressed data. The selected compressed data is taken into the memory 5.
Data can be sent from the one-frame memory 1 to the monitor 10 as needed, and can be displayed.

For the calculation of the image quality evaluation value, for example, equation (1)
There is an evaluation method called PSNR shown in FIG.

[0011]

(Equation 1)

Equation (1) shows an example of 8-bit black and white data, where N indicates the total number of pixels in one frame.
[I] is the original uncompressed image data (original pixel),
Dec [i] represents image data (processed image) expanded after compression.

In the above evaluation method, although there are individual differences, 30 to
It is said that if the numerical value is larger than 35 dB, the difference between the image quality of the uncompressed image and the image quality of the compressed image does not matter to human eyes. In other words, a compression method close to 30 to 35 dB is the optimum compression condition. Therefore, in the present invention, data compressed under the compression condition closest to such a condition is selected.

FIG. 2 is a block diagram of a main part for explaining another embodiment of the present invention. In the embodiment shown in FIG. 2, one compression memory 3 is used. In this way, the capacity of the compression memory can be reduced, so that the size and cost can be reduced. Image data captured from an input unit (not shown) is temporarily captured in the one-frame memory 1. Then, 1
The data in the frame memory 1 is compressed by the compression / decompression unit 2, and the compressed data is taken into the compression memory 3. When the compression is completed, the compressed data is sent from the compression memory 3 to the compression / decompression unit 2. The data expanded by the compression / expansion unit 2 is sent to the comparison operation unit 7. On the other hand, the original uncompressed image data is sent from the one-frame memory 1 to the comparison operation unit 7 via the buffer memory 6. Here, an image quality evaluation value is calculated from the two data. The calculated result is stored in the temporary evaluation memory 9.

After the operation is completed, the data in the one-frame memory 1 is compressed by the compression / decompression unit 2 at a different compression rate from the first time, and the compressed data is taken into the compression memory 3 and compressed again. The data is sent to the compression / decompression unit 2. On the other hand, the original uncompressed image data is sent from the one-frame memory 1 to the comparison operation unit 7 via the buffer memory 6. Here, an image quality evaluation value is calculated from the two data. Hereinafter, the same operation is performed a plurality of times. When all the calculations are completed, the calculation results are sent from the evaluation memory to a control unit (not shown), and the control unit automatically determines the optimum compression condition. Thereafter, the image data is compressed again under the selected compression condition, and the compressed data is stored in the memory 5. Data can be sent from the one-frame memory 1 to the monitor 10 as needed, and can be displayed.

FIG. 3 is a block diagram of a main part for explaining still another embodiment of the present invention. In this embodiment, the configuration is such that no compression memory is provided. Therefore, miniaturization and cost reduction can be achieved. Image data captured from an input unit (not shown) is temporarily captured in the one-frame memory 1. Next, the data in the one-frame memory 1 is sent to the compression unit 2a, compressed, and immediately sent to the expansion unit 2b for expansion. The decompressed data is sent to the comparison operation unit 7. Meanwhile, 1
The original uncompressed image data is simultaneously sent from the frame memory 1 to the comparison operation unit 7 via the buffer memory 6. Here, an image quality evaluation value is calculated from the two data. The calculated result is stored in the temporary evaluation value memory 9.

When the operation is completed, the data in the one-frame memory 1 is sent to the compression unit 2a, and then compressed at a different compression rate from the first time, and immediately sent to the expansion unit 2b for expansion. The decompressed data is sent to the comparison operation unit 7. On the other hand, the original uncompressed image data is simultaneously sent from the one-frame memory 1 to the comparison operation unit 7 via the buffer memory 6. Here, an image quality evaluation value is calculated from the two data. Hereinafter, the same operation is performed a plurality of times. When all the calculations are completed, the calculation results are sent from the evaluation value memory to a control unit (not shown), and the control unit automatically determines an optimal compression condition. After that, the image data is compressed again under the selected compression condition,
The compressed data is stored in the memory 5. Data can be sent from the one-frame memory 1 to the monitor 10 as needed, and can be displayed.

In the above description, the optimum compression condition is automatically determined, but the present invention allows the user to freely set the image quality according to the purpose of use.
For example, a user who only views a captured image on a liquid crystal monitor attached to a camera would like to increase the number of images stored on the liquid crystal by increasing the compression ratio and increasing the number of images to be stored. In that case, referring to FIG.
The compression ratio of the compressed data to be taken into the compression memory 3a is set in advance so as to be higher than the standard.

In the embodiment described above, the PSNR is used as a method for evaluating the image quality. However, it goes without saying that another method may be used. Further, as described above, by using the present invention, it is possible to save compressed data that can obtain a predetermined image quality without displaying an image.

[0020]

According to the first aspect of the present invention, there is provided an optical lens which forms an image of reflected light from a subject, and an image pickup means having an image pickup device which converts a subject image formed by the optical lens into an analog image signal. A digital electronic still camera including an analog signal processing unit for processing an analog image signal, an analog / digital conversion unit for converting an analog image signal into a digital image signal, and a digital signal processing unit for processing a digital image signal. The image quality is evaluated using the compressed image data and the image data obtained by expanding the plurality of compressed data, and the compressed image data is stored as compressed data that can obtain a predetermined image quality without displaying the image. Therefore, the uncompressed image data and the plurality of compressed data are expanded. The image quality is evaluated using the obtained image data, and the image data is stored as compressed data that can obtain a predetermined image quality without displaying the image. It can be, any type of image, it is possible to obtain a constant image quality.

According to a second aspect of the present invention, in the first aspect of the invention, compression and decompression are continuously performed to evaluate image quality.
Since the compression memory can be eliminated and the capacity of the compression memory can be reduced, the size and cost can be further reduced.

According to a third aspect of the present invention, in the first aspect of the present invention, since the image quality can be freely set by the user, the image quality desired by the user can be obtained freely.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a main part of an electronic still camera according to an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a main part of another embodiment of the electronic still camera according to the present invention.

FIG. 3 is a schematic diagram illustrating a main part of a still further embodiment of the electronic still camera according to the present invention.

FIG. 4 is a schematic diagram of a main part for explaining an example of a general electronic still camera.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 1 frame memory, 2 ... compression / expansion part, 2a ... compression part, 2b ... expansion circuit, 3, 3a-3n ... compression memory, 4
... Mux, 5 ... Memory, 6 ... Buffer memory,
7: comparison operation unit, 9: evaluation memory, 10: monitor, 1
DESCRIPTION OF SYMBOLS 1 ... Lens, 12 ... Image sensor, 13 ... Analog part, 14
... A / D converter, 15 ... Digital signal processing unit, 16 ... Memory, 17 ... Monitor, 18 ... Release button.

Claims (3)

[Claims] 1. An image pickup device comprising: an optical lens for forming an image of reflected light from a subject; an image pickup device for converting a subject image formed by the optical lens into an analog image signal; and processing the analog image signal. In a digital electronic still camera including an analog signal processing unit, an analog / digital conversion unit for converting an analog image signal into a digital image signal, and a digital signal processing unit for processing a digital image signal, uncompressed image data and a plurality of compressed An electronic still camera characterized in that image quality is evaluated using image data obtained by expanding data, and the image data is stored as compressed data capable of obtaining a predetermined image quality without displaying an image. 2. The electronic still camera according to claim 1, wherein compression and decompression are continuously performed to evaluate image quality. 3. The electronic still camera according to claim 1, wherein a user can freely set image quality.