JP2003167185A - Image processing method for electronic still camera and the electronic still camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing method for an electronic still camera and the electronic still camera capable of obtaining an image of high resolution even in the case of photographing while automatically setting a photographic lens at an over-focal distance when a range finding operation is disabled due to insufficient contrast. <P>SOLUTION: As for the image processing method for the electronic still camera equipped with an automatic focusing mechanism for automatically focusing the photographic lens by finding a range based on the picked up image signal of an object image, the contrast of the object image is detected at the range finding time, consequently, in the case the range finding operation is disabled due to the insufficient contrast, the photographic lens is set at the over-focal distance, and also, the image processing is applied on the picked up image signal so as to attain the improved resolution. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method and an electronic still camera for an electronic still camera equipped with an automatic focusing mechanism for automatically adjusting the focus of a taking lens by measuring a distance to a subject.

[0002]

2. Description of the Related Art An autofocus mechanism for automatically adjusting the focus of a photographing lens by performing distance measurement based on an image signal obtained by photographing the subject image is provided. In an electronic still camera that obtains image data by performing image processing on an image signal generated by imaging with, in general, a photographing lens is moved from a near point to a far point or from a far point to a near point, Based on the image signal obtained at each position of the movement process,
An evaluation signal for evaluating the degree of contrast such as high-frequency components is created, and based on the evaluation signal, a so-called hill-climbing method is used to detect a position where the value has a peak and combine the detected values. Focus is determined by determining the focus position and automatically moving the taking lens to that position.

In such an automatic focusing mechanism, the contrast of the subject image is lowered at dark low brightness, and therefore the above evaluation signal cannot be obtained satisfactorily, resulting in the state as shown in FIG. There are cases where detection becomes extremely difficult and distance measurement becomes impossible. In such a case, in the conventional electronic still camera, the taking lens is automatically set to the hyperfocal length so that the subject is roughly in focus.

[0004]

If the photographing lens is set to the hyperfocal length when the distance cannot be measured, the image can be generally focused, but the obtained image has a low resolution and the image is unfocused as a whole. It will be an image that will be displayed.

Therefore, the present invention is an electronic still camera capable of obtaining an image with a high resolution even when the photographing lens is automatically set to the hyperfocal length when photographing is not possible due to insufficient contrast. An object of the present invention is to provide an image processing method and an electronic still camera.

[0006]

According to a first aspect of the present invention for solving the above-mentioned problems, an automatic focus is provided for automatically adjusting the focus of a taking lens by performing distance measurement based on an image signal of a subject image. In an image processing method of an electronic still camera equipped with a mechanism, the contrast of an object image is detected during distance measurement, and as a result, when the distance measurement becomes impossible due to insufficient contrast, the photographing lens is set to a hyperfocal length. An image processing method for an electronic still camera is characterized in that image processing for improving resolution is added to a captured image signal.

The invention according to claim 2 is the image processing method for an electronic still camera according to claim 1, characterized in that the image processing for improving the resolution is edge enhancement processing.

Further, the invention according to claim 3 for solving the above-mentioned problems is provided with an automatic focusing mechanism for automatically adjusting the focus of the taking lens by performing distance measurement based on an image signal of a subject image. In an electronic still camera, a contrast detection unit that detects the contrast of a subject image during distance measurement, a determination unit that determines whether distance measurement is possible based on the detection result of the contrast detection unit, and a distance measurement that can be performed by the determination unit If it is determined that the taking lens is set to the in-focus position, and if it is determined that distance measurement is impossible, the taking lens is set to the hyperfocal distance, and the taking lens is set by the setting means. First image processing means for performing image processing on the image signal taken when the focal position is set, and an image taken when the taking lens is set to the hyperfocal length. And a second image processing means for performing image processing on the image signal, the image processing means wherein the second,
The electronic still camera is characterized in that it performs image processing that improves the resolution as compared with the first image processing means.

The invention according to claim 4 is the electronic still camera according to claim 3, characterized in that the image processing for improving the resolution is edge enhancement processing.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the internal structure of an electronic still camera according to the present invention. A subject image taken in through the taking lens 1 is formed on an image pickup surface of an image pickup device 3 such as a CCD through a diaphragm & shutter 2.
The subject image formed on the image sensor 3 is processed by the image processing CPU 4
After being converted into a digital signal by, predetermined image processing is performed.

The monitor 5 is provided on the back side of the camera body or the like, and displays an image before shooting (through image: an image reaching the image sensor 3 through the shooting lens 1).

As is well known, the release switch 6 is SW1.
And a switch of two stages of SW2, the camera control CPU when the push operation (SW1) is first performed in the half-pressed state.
7 outputs a predetermined drive signal to the motor driver 8,
The photographic lens 1 is moved by driving the lens motor 8a.

The image processing CPU 4 has an autofocus mechanism, and the SW1 activates the autofocus mechanism. That is, when SW1 is turned on, the camera control CPU
Reference numeral 7 moves the taking lens 1 from the near point to the far point or from the far point to the near point, and captures the image signal of the subject image from the image sensor 3 at each position in the moving process.

The image processing CPU 4 has a contrast detecting means 41, a judging means 42, a first image processing means 43 and a second image processing means 44 as shown in FIG.

The contrast detecting means 41 is the SW1.
The determination means 4 creates an evaluation signal for evaluating the degree of contrast such as a high-frequency component based on each of the image signals captured when the automatic focusing mechanism is activated by the ON operation of.
Output to 2.

The judging means 42 is the contrast detecting means 4
The evaluation signal from 1 is compared with a preset constant value, and it is determined whether the evaluation signal exceeds this constant value and sufficient contrast is obtained. As a result, when a sufficient contrast is obtained, a normal distance measuring operation, that is, a so-called hill-climbing method is used to search for a position where the value shows a peak, the focus position is detected, and the focus position information is obtained. Output to the camera control CPU 7. Also, FIG.
As shown in (b), when sufficient contrast is not obtained and the value does not exceed a certain value, it is determined that distance measurement is impossible, and information to that effect is output to the camera control CPU 7.

The camera control CPU 7 drives the motor driver 8 based on the focus position information, drives the lens motor 8a, and moves the taking lens to the focus position to perform focus. When the distance cannot be measured due to insufficient contrast, the motor driver 8 is driven and the lens motor 8a is driven to set the taking lens to the hyperfocal length.

The camera control CPU 7 drives the iris motor 8b to adjust the iris and adjust the exposure appropriately.

On the other hand, when the release switch 6 is subsequently pressed (SW2), the shutter 2 is actuated to perform the main exposure, the image of the object is picked up by the image pickup device 3, and the image signal taken from the image pickup device 3 is taken. Image processing CP
It is output to U4. During such shooting, the camera control CP
The flash 9 is used as necessary under the control of U7.

The image processing CPU 4, as shown in FIG.
First processing for performing different processing according to the result of the judging means 42
The image processing means 43 and the second image processing means 44 are included.

The first image processing means 43 is operated when the contrast detecting means 41 and the judging means 42 detect the in-focus position of the taking lens 1, and the normal image processing such as gradation correction and color correction is performed. , Edge enhancement, etc.

The second image processing means 44 is operated when the contrast detection means 41 and the determination means 42 determine that distance measurement is impossible due to insufficient contrast, and the photographing lens 1 is set to the hyperfocal length. Image processing is performed to improve the resolution as compared to normal image processing.

In the present invention, the image processing for improving the resolution is the image processing for improving the resolution of the apparent image so that the unsatisfactory focus is not felt. Examples include enhancement processing and contrast adjustment. Among them, the edge emphasis processing is preferable because the effect is easy to understand and the effect of improving the resolution is high.

It should be noted that the image processing for improving the sense of resolution performed here is a stronger processing than the normal image processing. Therefore, for example, in the case of edge enhancement processing, stronger processing is performed as compared with the edge enhancement processing that is performed as a normal series of image processing.

The image data of the photographed image generated by the image processing by the main exposure is output and recorded in the memory card 10 which is detachably attached to the camera body.

Reference numeral 11 is a power supply unit for supplying power to the image processing CPU 4 and the camera control CPU 7.

Next, the image processing method of the electronic still camera will be described with reference to the flowchart of FIG. 2 showing the processing operation.

First, when the release switch 6 is half-depressed and the SW1 is turned on (S1), the aperture is adjusted and the exposure is adjusted (S2).

When the SW1 is turned on, the automatic focusing mechanism is activated, the contrast detecting means 41 creates an evaluation signal from the image signal output from the image pickup device 3, and the judging means 42 makes a judgment for focus adjustment. (S
3).

When it is determined that the evaluation signal exceeds a preset constant value and a sufficient contrast is obtained, as shown in FIG. 4A (OK in S3).
In this case), the distance is measured and the in-focus position is detected, and then the camera control CPU 7 outputs a predetermined drive signal to the motor driver 8 to drive the lens motor 8a to move the taking lens 1 to the in-focus position. To (S4). As a result, a properly focused subject image is formed on the image sensor 3 through the taking lens 1.

Subsequently, when the release switch 6 is pressed and SW2 is turned on (S5), the main exposure is performed and the image signal output from the image pickup device 3 is changed to the image processing CP.
It is taken in by U4 (S6). In the image processing CPU 4, the captured image signal is subjected to usual predetermined image processing, compression processing and the like by the first image processing means 43 to obtain image data of a captured image (S7). Next, this image data is recorded in the memory card 10 (S8), and a series of photographing operations is completed.

On the other hand, the evaluation signal does not exceed the preset constant value as shown in FIG. 4 (b) due to the reason that the photographing condition is low brightness, etc., and the contrast becomes insufficient and the distance measurement is impossible. If it is determined to be (NO in S3), the camera control CPU 7 outputs a predetermined drive signal to the motor driver 8 and drives the lens motor 8a to set the taking lens 1 at the hyperfocal length ( S9). At this time, an image of the subject that is unfocused as a whole is formed on the image sensor 3 such that the image has passed through the taking lens 1 and is generally in focus.

After that, when the release switch 6 is subsequently pressed and the SW2 is turned on (S10), the main exposure is performed and the image signal output from the image pickup device 3 is taken into the image processing CPU 4 (S11).

Next, the image processing CPU 4 performs image processing on the captured image signal. The image signal at this time is the image signal when the taking lens 1 is set to the hyperfocal length due to the inability to measure the distance. Therefore, the second image processing unit 44 adds image processing that improves the resolution as compared with the image processing performed by the first image processing unit 43. The image signal whose resolution is improved by such image processing is further subjected to ordinary predetermined image processing, compression processing and the like to be image data of a photographed image (S12). Next, this image data is recorded in the memory card 10 (S8), and a series of photographing operations is completed.

As described above, according to the present invention, when distance measurement is impossible due to the automatic focusing mechanism, the photographing lens 1 is set to the hyperfocal length to perform photographing, and normal image processing ( The second image processing means 44, which is different from the processing by the first image processing means 43, is used to add the image processing for improving the resolution, so that the image obtained by the second image processing means 44 is the same as that obtained by the photographing lens 1. Even though it is a photographed image set to the focal length, it becomes a good image in which the lack of focus is eliminated.

[0037]

According to the present invention, even when the photographing lens is automatically set to the hyperfocal length and photographing is performed when distance measurement cannot be performed due to insufficient contrast, an electronic image with high resolution can be obtained. An image processing method for a still camera and an electronic still camera can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing the internal configuration of an electronic still camera.

FIG. 2 is a block diagram illustrating a configuration of an image processing CPU.

FIG. 3 is a flowchart showing a shooting operation.

4A and 4B are graphs showing contrast characteristics, respectively.

[Explanation of symbols]

1: Shooting lens 2: Aperture & shutter 3: Image sensor 4: Image processing CPU 41: Contrast detection means 42: Judgment means 43: First image processing means 44: Second image processing means 5: Monitor 6: Release switch 7: Camera control CPU 8: Motor driver 8a: Motor for lens 8b: Motor for diaphragm 9: Flash 10: Memory card 11: Power supply

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 5/232 G02B 7/11 D // H04N 101: 00 G03B 3/00 A

Claims (4)

[Claims] 1. An image processing method for an electronic still camera equipped with an autofocus mechanism for automatically adjusting the focus of a photographing lens by performing distance measurement based on an image signal obtained by capturing an image of an object. When the contrast of the image is detected, and as a result, it becomes impossible to measure the distance due to the lack of the contrast, the image pickup lens is set to the hyperfocal distance, and image processing for improving the resolution of the captured image signal is performed. An image processing method for an electronic still camera, characterized by being added. 2. The image processing method for an electronic still camera according to claim 1, wherein the image processing for improving the resolution is edge enhancement processing. 3. An electronic still camera equipped with an autofocus mechanism for automatically adjusting the focus of a photographing lens by performing distance measurement based on an image signal of a subject image, the contrast of the subject image being measured during distance measurement. Contrast detection means for detecting, judgment means for judging whether distance measurement is possible based on the detection result of the contrast detection means, and the photographing lens for focusing position when it is judged that distance measurement is possible by the judgment means. And setting means for setting the taking lens to a hyperfocal distance when it is determined that distance measurement is impossible, and an image signal imaged when the taking lens is set to the in-focus position by the setting means. First image processing for
Image processing means, and second image processing means for performing image processing on the image signal captured when the taking lens is set to the hyperfocal length, and the second image processing means An electronic still camera, characterized in that it performs image processing that improves the resolution as compared with the first image processing means. 4. The electronic still camera according to claim 3, wherein the image processing for improving the resolution is edge enhancement processing.