JP2003219259A - Method for correcting piece out-of-focus in digital camera and digital camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily reduce piece out-of-focus even in a digital camera having piece out-of-focus. <P>SOLUTION: This digital camera sets an area narrower than the entire pixel area (a) from which an image can be obtained by a CMOS image sensor as an effective pixel area with coordinate values (x, y), etc., and records an image within the set effective pixel area b on a memory card. Whether piece out-of- focus c exists in any area in the entire pixel area (a) of the CMOS image sensor is detected. If there is a piece out-of-focus c, an effective pixel area b is set so as to avoid the piece out-of-focus, and coordinate values (x, y), etc., showing the position of the effective pixel area b are written to a nonvolatile memory as a setting value. <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 a method for correcting one-sided blurring in a digital camera and a digital camera, and more particularly to improving one-sided blurring caused by optical characteristics of a taking lens, mounting accuracy of the taking lens, and the like.

[0002]

2. Description of the Related Art A blurred image does not blur the entire periphery of the subject, but a fixed part of the image blurs.
The problem is that it is very unsightly.

In order to prevent this one-sided blur, it is necessary to reduce variations in the optical characteristics of the peripheral portion of the taking lens, and to make the taking lens mounting accuracy with respect to the camera body and the imaging element mounting accuracy with high accuracy. There is.

[0004]

However, the above-mentioned one-sided blur can be inspected only after the camera is assembled, and if there is one-sided blur, the one-sided blur should be assembled to correct or reduce the one-side blur. It was complicated because it was necessary to redo the work.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for correcting one-sided blur in a digital camera and a digital camera capable of easily reducing one-sided blur after the camera is assembled. To do.

[0006]

In order to achieve the above object, the invention according to claim 1 sets a region narrower than the whole pixel region in the image pickup device in which an image can be taken in as an effective pixel region by region setting information. Then, in the digital camera which records the image in the set effective pixel area on the recording medium, the chart of which the degree of blurring can be detected is photographed using all the pixel areas of the image sensor, and the chart is photographed. A step of detecting one-sided blurring based on a chart image of at least four corner areas of the entire pixel area, and moving the effective pixel area of the image sensor within the all-pixel area to reduce the detected one-sided blur And a step of setting the area setting information.

That is, as the adjustment work before the shipment of the camera,
A chart such as vertical stripes is photographed, and one-sided blur is detected based on a chart image of at least four corner regions of the entire pixel region of the image sensor. This one-sided blur may be detected based on the magnitude of the high frequency component of each chart image in the four corner regions, or may be detected by the operator visually observing each chart image in the four corner regions. Then, when there is a one-sided blur, the effective pixel area is set so as to avoid a portion with a one-sided blur in the entire pixel area of the image sensor. That is, the area setting information such as the coordinate value of the image sensor and the address indicating the cut-out range of the effective pixel area in the entire pixel area is set. The image of the effective pixel area may be cut out by the area setting information after capturing the image of the entire pixel area from the image sensor, or only the image of the effective pixel area may be directly output by the image sensor by the area setting information. It may be read.

According to a second aspect of the present invention, an area narrower than the entire pixel area where an image can be captured in the image sensor is set as the effective pixel area by the area setting information, and the image in the set effective pixel area is set. In a digital camera for recording on a recording medium, a detection unit for detecting partial blur based on an image acquired from at least four corner areas of the entire pixel area of the image sensor, and an effective pixel area of the image sensor for all pixels Area setting means for automatically setting the area setting information for reducing the detected one-sided blur by moving within the area.

For example, the camera is set to the one-sided blur correction operation mode, a desired subject suitable for detecting one-sided blurring is photographed, and one side is obtained based on an image obtained from at least four corner areas of the entire pixel area of the image sensor. Detect blur. This one-sided blur detection is automatically performed based on the magnitude of the high-frequency component of each image acquired from the four corner regions (the blurred image has less high-frequency component). Then, when there is one-sided blur, the effective pixel area is automatically set so as to avoid the one-sided blur portion of the entire pixel area of the image sensor. As a result, at the time of shooting in the normal shooting mode, an image without blurring or reduced blurring in the effective pixel area set as described above is recorded.

According to a third aspect of the present invention, a digital camera for measuring the brightness of an object and determining an aperture value and a shutter speed based on the measured brightness of the object and a predetermined program diagram to photograph the object. In the above, a detection means for detecting focus states at a plurality of locations around the subject, and a determination means for determining whether or not the degree of one-sided blur is larger than a predetermined value based on the detected focus states at the plurality of locations. And a means for changing the aperture value at the time of shooting to an aperture value on the open side of the aperture value determined on the basis of the program diagram when the degree of one-sided blur is larger than a predetermined value by the determination means. It is characterized by having.

That is, if the degree of one-sided blur becomes larger than a predetermined value, the image becomes unsightly. Therefore, the aperture value is changed to the open side rather than the aperture value determined in advance by the program diagram (depth of focus). To make it narrower). This allows
Distance of the main subject for which focus adjustment is performed (subject distance)
The peripheral part of the main subject at a different distance from is blurred to make the one-sided blur unnoticeable.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a method for correcting one-sided blur in a digital camera and a digital camera according to the present invention will be described below in detail with reference to the accompanying drawings.

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

The digital camera 10 records a photographed still image or moving image in a memory card 54, and the operation of the entire camera is centrally controlled by a central processing unit (CPU) 40.

The digital camera 10 is provided with an operation section 38 including a shutter button and a mode dial for setting a photographing mode, a reproduction mode and the like.
A signal corresponding to the operation of is input to the CPU 40.

The image light showing the subject is taken by the taking lens 12,
An image is formed on the light receiving surface of the CMOS image sensor 16 via the diaphragm 14. The taking lens 12 is driven by a motor driver 36 controlled by the CPU 40, and focus control and the like are performed. The diaphragm 14 is composed of five diaphragm blades and is driven by a motor driver 34 controlled by the CPU 40. For example, the diaphragm value F2.8 to
The aperture is controlled in 5 steps up to F11 in steps of 1 A _V.

Further, the CPU 40 uses the motor driver 3
4, the aperture 14 is controlled, and the image sensor control unit 32 is used to control the charge accumulation time (shutter speed) in the CMOS image sensor 16 and a readout area described later.

The signal charge accumulated in the CMOS image sensor 16 is read out as a voltage signal corresponding to the signal charge based on a read signal applied from the image sensor control section 32. The voltage signal read from the CMOS image sensor 16 is applied to the analog signal processing unit 18, where the R, G, and B signals for each pixel are sampled and held, amplified, and then sent to the A / D converter 20. Added. The A / D converter 20 sequentially inputs R, G, B
The signals are converted into digital R, G, B signals and output to the image input controller 22.

The digital signal processing section 24 performs offset processing, gain control processing including white balance correction and sensitivity correction, gamma correction processing, YC processing, etc. on a digital image signal input via the image input controller 22. The predetermined signal processing is performed.

The image data processed by the digital signal processor 24 is input to the VRAM 50. The VRAM 50 includes an A area and a B area each of which stores image data representing an image for one frame. In the VRAM 50, image data representing an image for one frame is rewritten in the A area and the B area alternately. Area A and B of VRAM 50
The written image data is read from an area other than the area in which the image data has been rewritten. The image data read from the VRAM 50 is encoded in the video encoder 28,
The image is output to the liquid crystal monitor 30 provided on the rear surface of the camera, whereby the subject image is displayed on the display screen of the liquid crystal monitor 30.

The first shutter button of the operation unit 38
When the step is pressed (half-pressed), the AE operation and the AF operation are started. That is, the image data output from the A / D converter 20 is input to the AF detection unit 42 and the AE detection unit 44, and the AF detection unit 42 outputs a value (evaluation value) obtained by integrating the high frequency components of the image to the CPU 40. To do. AE detector 44
Then, the R, G, and B image data are integrated, and the integrated value is output to the CPU 40.

The CPU 40 moves the taking lens 12 through the motor driver 36 to the lens position where the evaluation value is maximized based on the evaluation value input from the AF detection unit 42, and inputs it from the AE detection unit 44. The brightness (shooting Ev value) of the subject is calculated from the integrated value, and the shooting E
The aperture value of the aperture 14 and the electronic shutter (shutter speed) of the CMOS image sensor 16 are determined based on the v value according to a predetermined program diagram (see FIG. 8), and the motor driver 34 is determined based on the determined aperture value. The aperture 14 is controlled via the C sensor and the C sensor is controlled via the image sensor control unit 32 based on the determined shutter speed.
The charge storage time in the MOS image sensor 16 is controlled.

When the AE operation and the AF operation are completed and the shutter button is depressed in the second stage (full depression), the image data for one frame output from the A / D converter 20 in response to the depression. From the image input controller 22 to the memory (SDRA
M) Input to 48 and temporarily stored.

The image data is read from the memory 48, and predetermined signal processing including generation processing (YC processing) of luminance data and color difference data is performed in the digital signal processing section 24. YC processed image data (YC data)
Are read from the digital signal processing unit 24 and stored again in the memory 48. Subsequently, the YC data is output to the compression / expansion processing unit 26, and JPEG (joint photgraphic expert
A predetermined compression process such as s group) is executed. The compressed YC data is output to the memory 48 again and stored therein, then read by the media controller 52 and recorded in the memory card 54.

Next, a method of correcting the one-sided blur in the digital camera 10 having the above-described structure will be described.

At the adjustment stage before shipment of the digital camera 10, the chart 60 whose degree of blur can be detected by the digital camera 10 is photographed as shown in FIG.
This chart 60 has, for example, a fine vertical stripe pattern,
2 can be moved in the left-right direction along the rail 62, and the digital camera 10 can also be moved in the left-right direction along the rail 62 in FIG.

Then, the digital camera 10 and the chart 6
The chart 60 is photographed by the digital camera 10 while changing the relative distance to 0. The digital camera 10 is shown in FIG.
As shown in, the evaluation values obtained by integrating the high frequency components contained in the image signals of the chart images of the four corner areas A, B, C, D of the CMOS image sensor 16 are collected for each shooting distance. , Area A depending on the size of the evaluation value,
The degree of blurring of B, C, and D is detected. And there is one
When one area has a certain value or more lower than the other areas and the evaluation value is lower, it is determined that the area is partially blurred.

The detection of one-sided blur is not limited to the above case, the evaluation value of the central area of the CMOS image sensor 16 is calculated, and the evaluation value of the central area and the four corner areas A, B ,.
You may make it detect the one-sided blur location by comparing with each evaluation value of C and D. Alternatively, the image of the chart 60 may be printed out or output to a monitor, and the operator may visually check the output result to detect the one-sided blur.

Next, a method of correcting the one-sided blur when the one-sided blur is detected as described above will be described.

Now, as shown in FIG. 4, when there is a one-sided blur c in the lower right area of the entire pixel area a of the CMOS image sensor 16, the effective pixel of the CMOS image sensor 16 should be avoided so as to avoid this one-sided blur c. Area b is set. The effective pixel area b has a predetermined pixel size that can be set by appropriately moving it in the entire pixel area a, and the image in the effective pixel area b is recorded in the memory card during normal shooting.

The effective pixel area b is set, for example, by the coordinate value (x, x, in the upper left all pixel area a of the effective pixel area b).
y) and area setting information such as an address are input. This area setting information is used for the digital camera 10
Non-volatile memory (EEPROM) 46 (see FIG. 1)
Is recorded as a set value in.

When normal photographing is performed by the digital camera 10 in which the area setting information is recorded in the EEPROM 46 as described above, the CPU 40 causes the EEPROM 46 to read.
The area setting information is read from the image sensor control unit 3
Only the image signal of the effective pixel area b corresponding to the area setting information is fetched from the CMOS image sensor 16 via 2.

In this embodiment, the CMOS image sensor 16 is used as the image pickup element, but the CCD
An image sensor can also be used. In this case, the image signals of all the pixel areas of the CCD image sensor are once taken into the memory 48, and then the image data of the effective pixel area b is cut out according to the area setting information recorded in the EEPROM 46 and the signal processing is performed.

Next, another method for detecting one-sided blurring in the digital camera 10 will be described.

For example, the digital camera 10 is set to the operation mode for correcting the one-sided blur, and the subject is photographed in a state where the digital camera is upright as shown in FIG. 5 (normal photographing). Shoot the same subject with the camera turned upside down (upside down shooting).

When there is a one-sided blur, areas A, B, C, D at the four corners of the entire pixel area at the time of normal photographing shown in FIG.
5 and the evaluation values of the four corner regions D, C, B, and A of all pixel regions at the time of upside-down shooting shown in FIG.

For example, when the evaluation values shown in FIG. 6 are obtained, the evaluation value of the area A at the time of normal photographing and the evaluation value of the area D at the time of upside down photographing (FIG. 6A), and the normal evaluation value are obtained. The evaluation value of the region D at the time of photographing and the evaluation value of the region A at the time of photographing upside down (see FIG. 6).
Since (B)) is almost the same, it can be seen that the areas A and D have no blur.

On the other hand, the evaluation value of the area B at the time of normal photographing is upside down and the evaluation value of the area C at the time of photographing (FIG. 6C), and the evaluation value of the area C at the time of normal photographing is upside down. Area B at the time of shooting
There is a difference in the evaluation values (FIG. 6 (D)) and the evaluation value of the region C is small, which indicates that the region C has one-sided blur.

When the position of the one-sided blur is automatically detected as described above, the digital camera 10 automatically sets the effective pixel area so as to avoid the one-sided blur.

When detecting the one-sided blur as described above, the chart 60 shown in FIG. 2 may be used as the subject.

Further, as shown in FIG. 7, a semi-transparent lens cap 70 having vertical stripes is attached to the taking lens of the digital camera 10, and the lens cap 70 is photographed and the four corner areas A and B of all pixel areas are taken. , C, D may be calculated to detect the position of the one-sided blur. The lens cap 70 has two claws 70A, and the photographing lens is provided with a claw stopper 10A that engages with the claw 70A.
0 is mounted on the taking lens in a fixed direction.

In the above example, the case where the one-sided blur is automatically detected and the effective pixel area is set has been described. However, the user confirms the one-sided blur position while observing the image displayed on the liquid crystal monitor 30, and determines the effective pixel area. The area may be set by graphic or numerical input.

Next, another correction method for one-sided blur in a digital camera will be described.

First, when the shutter button of the operation unit 38 is half pressed, the AE operation and the AF operation are started. AF
In operation, the focus value of the taking lens 12 is adjusted using the evaluation value of the central area (focus area) of the CMOS image sensor 16, but at the same time, the peripheral area (for example, the four corner area areas A and B shown in FIG. 3) is adjusted. , C, D) are also collected to detect the degree of one-sided blur.

When the degree of one-sided blur is larger than a certain value, the shutter button is fully pressed and the aperture 14 is pressed.
To open and shoot. That is, when there is no one-sided blur, the aperture value and the shutter speed are determined based on the brightness (shooting Ev value) of the subject calculated by the AE detection unit 44 according to the solid program diagram of FIG. If there is one-sided blur, the aperture value and shutter speed are determined according to the program diagram of the broken line in FIG. Further, when the photographing is performed with the aperture set to the open side, the user is notified on the screen of the liquid crystal monitor 30.

As described above, by changing the aperture value to the open side (narrowing the depth of focus) from the aperture value determined in advance by the program diagram, the entire peripheral portion is blurred and one-sided blurring occurs. To make it inconspicuous.

When the "portrait mode" is selected as the photographing mode, the "portrait mode" originally uses the program diagram for setting the aperture to the open side. It is also possible not to change the aperture.

[0048]

As described above, according to the present invention, one-sided blur can be easily reduced after the digital camera is assembled. As a result, variations in optical characteristics of the taking lens and requirements for mounting the taking lens on the camera body are alleviated, and the defective rate can be suppressed on the production line in the factory.

[Brief description of drawings]

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

FIG. 2 is a diagram used to explain a one-sided blur correction method in a digital camera.

FIG. 3 is a diagram showing a state of all pixel regions of a CMOS image sensor that captures a chart.

FIG. 4 is a diagram used for explaining setting of an effective pixel area of a CMOS image sensor that avoids a one-sided blur area;

FIG. 5 is a diagram used to explain a one-sided blur detection method in a digital camera.

FIG. 6 is a diagram used to explain a one-sided blur detection method in a digital camera.

FIG. 7 is a diagram used to explain a one-sided blur detection method in a digital camera.

FIG. 8 is a program diagram for exposure control.

[Explanation of symbols]

10 ... Digital camera, 12 ... Shooting lens, 14 ... Aperture, 24 ... Digital signal processing unit, 30 ... Liquid crystal monitor, 3
2 ... Image sensor control unit, 38 ... Operation unit, 40 ... CP
U, 42 ... AF detection unit, 44 ... AE detection unit, 46 ... EE
PROM, 48 ... Memory, 54 ... Memory card, 60 ...
Chart, 70 ... Lens cap, a ... Whole pixel area, b
... Effective pixel area, c ... One-sided blur

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 5/91 G02B 7/11 N 5C061 17/00 D // H04N 101: 00 G03B 3/00 AF term (Reference) 2H002 CC21 CC31 FB33 GA70 HA23 2H011 BA31 BB04 DA00 2H051 BA45 DA07 DA39 DB01 5C022 AA13 AB21 AB45 AC01 AC42 AC54 AC78 5C053 FA08 FA14 FA27 HA40 JA30 KA30 LA02 5C061 BB03

Claims (3)

[Claims] 1. A digital system in which an area narrower than the entire pixel area capable of capturing an image in an image sensor is set as effective pixel area by area setting information, and an image in the set effective pixel area is recorded on a recording medium. In the camera, a step of photographing a chart in which the degree of blurring can be detected using all pixel areas of the image sensor, and one-sided blurring based on a chart image of at least four corner areas of the photographed whole pixel area A step of detecting, and a step of moving the effective pixel area of the image sensor within the entire pixel area to set the area setting information for reducing the detected partial blur, One-sided blur correction method for cameras. 2. A digital system in which an area narrower than the whole pixel area capable of capturing an image in an image sensor is set as effective pixel area by area setting information, and an image in the set effective pixel area is recorded on a recording medium. In the camera, a detection unit that detects a one-sided blur based on an image acquired from at least four corner regions of the entire pixel region of the image sensor, and an effective pixel region of the image sensor is moved within the entire pixel region. An area setting unit that automatically sets the area setting information for reducing the detected one-sided blur. 3. A digital camera for photographing a subject by measuring the brightness of the subject and determining an aperture value and a shutter speed based on the measured brightness of the subject and a predetermined program diagram. A detection means for detecting the in-focus state of a plurality of locations, a determination means for determining whether or not the degree of one-sided blur is greater than a predetermined value based on the detected in-focus states of the plurality of locations, and the determination means When the degree of one-sided blur is greater than a predetermined value, a means for changing the aperture value at the time of shooting to an aperture value on the open side of the aperture value determined based on the program diagram, is provided. Characteristic digital camera.