JP2012165206A - Setting method of effective pixel region of solid state image sensor and manufacturing method of imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a setting method of an effective pixel region of a solid state image sensor capable of eliminating variation in the quantity of light on the periphery of the effective pixel region, by matching the center of the effective pixel region of the solid state image sensor and the optical axis of an objective optical system by simple measurement.SOLUTION: Evaluation values of imaging results of white light are measured for four regions located to include a pixel belonging to the central region of a solid state image sensor which imaged the white light, and regions located radially from the center where the white light is imaged and not imaged. Deviation amount of the center of the solid state image sensor from the region where the white light is imaged is then calculated from the calculated evaluation value, and an effective pixel region is set around the position, corrected by the calculated deviation amount from the center of the solid state image sensor, as a center.

Description

  The present invention relates to a method for setting an effective pixel area of a solid-state image sensor, and more particularly to a method for setting an effective pixel area of a solid-state image sensor that optimizes the balance of the amount of light around the area.

  In the manufacture of digital still cameras, digital video cameras, etc., it is necessary to match the center of the effective pixel area of a solid-state image sensor such as a CCD or CMOS with the optical axis of the objective optical system to eliminate variations in the amount of light around the effective pixel area. It is essential. If there is a deviation between the center of the effective pixel area of the solid-state image sensor and the optical axis of the objective optical system, and the amount of light around the effective pixel area varies, the brightness of the captured image is unbalanced. This is because it becomes a thing.

  Conventionally, in the manufacturing process of an imaging device, the relationship between the installation position of a solid-state imaging device and the installation position of a lens unit such as an objective optical system is previously set in the solid-state imaging device while adjusting using a measuring instrument or the like. Assembling was performed so that the center of the effective pixel area coincided with the optical axis of the objective optical system. However, assembling while performing measurement and adjustment for each imaging device to be manufactured is inefficient and takes time, and further increases costs.

  Therefore, the above-described measurement is performed on some samples in advance, and the position of the center of the effective pixel area that can be trusted to some extent for the same model as the sample is identified from the measurement results, and manufactured. In the process, after assembling a lens unit such as an objective imaging system and a solid-state imaging device, a method of setting an effective pixel region based on the specified center position has been adopted.

  However, if the position of the center of the effective pixel area identified from the sample is applied to all solids as in the above method, the effective pixel area will be subtracted from the subtle shift in the installation position of the objective optical system and solid-state image sensor that occurs for each solid. The center of the optical axis and the optical axis shift, and a solid with varying amounts of light around the effective pixel region appears. Therefore, even after the assembly of the objective optical system and the solid-state image sensor is completed, there is a problem of setting an appropriate effective pixel region for each solid.

  The present invention has been made in view of such a problem. Even after the lens unit and the solid-state image sensor are assembled, the center of the effective pixel region of the solid-state image sensor and the optical axis of the objective optical system can be obtained by simple measurement. It is an object of the present invention to provide a method for setting an effective pixel area of a solid-state imaging device that can match the above and eliminate variations in the amount of light around the effective pixel area.

  In order to achieve the above object, according to the present invention, the solid-state imaging device (301) captures white light, and the evaluation of the white light imaging result is performed for the pixels belonging to the central region of the solid-state imaging device (301). A step of calculating a value, and a region (302) where the white light is imaged and a region (303) where the white light is imaged and are located radially from the center of the solid-state image sensor (301) The evaluation value of the imaging result of the white light is measured for the first measurement region (501), the second measurement region (502), the third measurement region (503), and the fourth measurement region (504) that are positioned. A difference between the sum of the evaluation values of the first and second measurement regions and the sum of the third and fourth evaluation values of the first difference and the first and third measurement regions. The difference between the sum of the evaluation values and the sum of the second and fourth measurement areas A step of calculating a second difference, and dividing the first difference and the second difference by an evaluation value for a pixel belonging to the central region, and the center of the solid-state imaging device (301) and the white color Calculating a shift amount from a region where light is imaged, and setting an effective pixel region centered on a position corrected by the calculated shift amount from the center of the solid-state imaging device. Provided is a method for setting an effective pixel region of a solid-state imaging device.

  To achieve the above object, the present invention provides a step of installing an objective optical system, a step of installing a solid-state imaging device (301), a step of imaging a white light by the solid-state imaging device (301), and the solid-state imaging For the pixel belonging to the central region of the element (301), a step of calculating an evaluation value of the imaging result of the white light, and the white light are connected to each other radially from the center of the solid-state imaging element (301). A first measurement region (501), a second measurement region (502), a third measurement region (503) positioned so as to include an imaged region (302) and a non-imaged region (303), And a step of measuring the evaluation value of the imaging result of the white light for the fourth measurement region (504), the sum of the evaluation values of the first and second measurement regions, and the third and fourth evaluation values The difference of the sum of the first difference, and the first And calculating a second difference between a sum of evaluation values of the third measurement region and a sum of the second and fourth measurement regions, and calculating the first difference and the second difference Dividing the evaluation value for the pixel belonging to the central region to calculate the amount of deviation between the center of the solid-state imaging device (301) and the region where the white light is imaged, and the center of the solid-state imaging device And a step of setting an effective pixel area centered on a position corrected by the calculated shift amount.

  The solid-state imaging device (301) described above may be a CMOS sensor, and the evaluation value may be based on an OB value of a Gb signal.

  According to the present invention, even after the lens unit and the solid-state image sensor are assembled, the center of the effective pixel area of the solid-state image sensor and the optical axis of the objective optical system are matched with each other by simple measurement. It is possible to set an effective pixel area with no variation in the amount of light.

6 is a flowchart for explaining a procedure of a method for setting an effective pixel area of the solid-state imaging device according to the embodiment of the present invention. It is a figure for demonstrating irradiation of the white light which concerns on embodiment of this invention. It is a figure for demonstrating the state which white light imaged on the solid-state image sensor. It is a figure for demonstrating the measurement of the center measurement area | region of a solid-state image sensor. It is a figure for demonstrating the measurement area | region of predetermined four places of a solid-state image sensor. It is a figure for demonstrating the measurement of the measurement area | region of four predetermined places of a solid-state image sensor. It is a figure for demonstrating the setting of an effective pixel area | region.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

FIG. 1 is a flowchart for explaining the procedure of a method for setting an effective pixel area of a solid-state imaging device according to an embodiment of the present invention.
First, white light is irradiated to the imaging device in which the assembly of the objective optical system and the solid-state imaging device is completed (step S101). For example, as shown in FIG. 2, the white light is placed so that the irradiation surface of the light panel 203 that emits white light and the optical axis 202 of the objective optical system of the imaging apparatus 201 are perpendicular to each other. Then, uniform white light is emitted from the light panel 203 toward the imaging device 201.

  When white light is irradiated in step S101, the white light is photographed and imaged on a solid-state image sensor (step S102). The white light that has passed through the various optical systems and the diaphragm forms an image on the solid-state imaging device 301 as shown in FIG. That is, an effective light amount region 302 (region shown in white in FIG. 3) in which white light forms an image in the form of a so-called vignetting circle and a light-shielding region 303 in which white light does not form an image (shown by hatching in FIG. 3). Region) appears on the solid-state image sensor 301.

  With respect to the white light imaged on the solid-state image sensor in step S102, an evaluation value per pixel in a predetermined region in the center of the solid-state image sensor is measured (step S103). FIG. 4 is a diagram for explaining the measurement of the evaluation value. A predetermined area 402 centered on the center 401 of the solid-state imaging element 301 is predetermined as a measurement target area. Hereinafter, the predetermined area 402 is referred to as a central measurement area 402. The size of the central measurement region 402 is determined to be, for example, a total of 256 pixels of 16 pixels on the vertical side and 16 pixels on the horizontal side. Then, an evaluation value is measured for the central measurement region 402 composed of 256 pixels. For example, when the solid-state imaging device is a CMOS (Complementary Metal Oxide Semiconductor) sensor, the evaluation value is OB (Gr signal OB (of R signal, Gr signal, Gb signal, and B signal) detected from the central measurement region 401. The evaluation value is calculated from the value of (Optical Black).

  Then, the evaluation value of the entire central measurement region 402 is divided by the total number of pixels included in the region, and is calculated as an evaluation value per pixel. Here, the reason why the measurement and the evaluation value are calculated for the predetermined region first is that when the measurement and the evaluation value are calculated for each pixel, it is not possible to take into account variations for each pixel to be measured. By calculating the average value of the evaluation values for each pixel from the evaluation values of the predetermined area, it is possible to perform the evaluation excluding the variation.

  When the central measurement area of the solid-state image sensor is measured in step S103, next, evaluation values of four predetermined measurement areas on the solid-state image sensor are measured (step S104). FIG. 5 is a conceptual diagram for explaining the four measurement regions. The sizes of the four measurement areas 501, 502, 503, and 504 are assumed to be equal to the central measurement area used in step S103. Each measurement region is positioned so as to spread radially around the center 401 of the solid-state imaging device, and in advance such that each measurement region includes both the effective light amount region 302 and the light shielding region 303. It has been established.

  FIG. 6 is a diagram for explaining measurement of evaluation values in four measurement regions. As described above, the optical axis, that is, the center 601 of the effective light amount region and the center 401 of the solid-state image sensor do not exactly coincide with each other due to a slight shift that occurs when the objective optical system and the solid-state image sensor are assembled. In addition, the ratio of the area of the effective light amount region and the light shielding region included in each of the measurement regions 501, 502, 503, and 504 is different depending on each region.

  Therefore, first, for each of the four measurement regions, the evaluation value is measured by the same method as that for measuring the evaluation value of the central measurement region in step S103. That is, for example, when the solid-state imaging device is a CMOS sensor, an evaluation value is calculated from an OB (Optical Black) value of the Gr signal among R, Gr, Gb, and B signals detected from each region. .

  When the evaluation values of the four measurement regions are calculated in step S104, a horizontal shift between the center of the effective light amount region and the center of the solid-state imaging device is detected from the evaluation value of each region (step S105). Specifically, the detection of the deviation is performed as follows.

  When the evaluation value of the measurement region 501 is AD1, the evaluation value of the measurement region 502 is AD2, the evaluation value of the measurement region is AD3, and the evaluation value of the measurement region 504 is AD4, the following equations (1) and (2) From these, horizontal evaluation values ADH1 and ADH2 are calculated.

ADH1 = AD1 + AD2 (1)

ADH2 = AD3 + AD4 (2)

  Then, the difference between the evaluation values in the horizontal direction is calculated from the difference between ADH1 and ADH2. When this difference is calculated, it is assumed that a horizontal shift between the center of the solid-state imaging device and the optical axis has been detected.

  If a horizontal shift between the center of the solid-state imaging device and the optical axis is detected in step S105 (YES in step S105), the horizontal position of the center of the effective pixel region is specified from the horizontal shift (step S105). S106). Specifically, the difference between the horizontal evaluation values calculated in step S105 is divided by the evaluation value per pixel of the central measurement area calculated in step S103, and the amount of horizontal deviation is calculated by the number of pixels. To do. Then, the position shifted by the calculated shift amount from the center of the solid-state image sensor is specified as the horizontal position of the center of the effective pixel area.

  If the horizontal position of the center of the effective pixel area is specified in step S106, or if no horizontal shift is detected between the center of the solid-state imaging device and the optical axis in step S105 (NO in step S105), A vertical deviation between the center of the effective light amount region and the center of the solid-state imaging device is detected from the evaluation value of each region (step S107). Specifically, the detection of the deviation is performed as follows.

  The evaluation values ADV1 and ADV2 in the vertical direction are calculated from the following formulas (3) and (4) using the evaluation values of each measurement region as in step S105.

ADV1 = AD1 + AD3 (3)

ADV2 = AD2 + AD4 (4)

  Then, the difference between the evaluation values in the vertical direction is calculated from the difference between ADV1 and ADV2. When this difference is calculated, it is assumed that a horizontal shift between the center of the solid-state imaging device and the optical axis has been detected.

  If a vertical shift between the center of the solid-state imaging device and the optical axis is detected in step S107 (YES in step S107), the vertical position of the center of the effective pixel region is specified from the vertical shift (step S107). S108). Specifically, the vertical evaluation value difference calculated in step S107 is divided by the evaluation value per pixel of the central measurement area calculated in step S103, and the amount of vertical shift is calculated by the number of pixels. To do. Then, the position shifted by the calculated shift amount from the center of the solid-state image sensor is specified as the vertical position of the center of the effective pixel area.

  When the vertical position of the center of the effective pixel area is specified in step S108, or when no horizontal shift is detected between the center of the solid-state imaging device and the optical axis in step S107 (NO in step S107), An effective pixel area is set (step S109). FIG. 7 is a diagram for explaining the effective pixel region setting process.

  The horizontal position and the vertical position of the center of the effective pixel area specified through the above steps coincide with the center 601 of the effective light quantity area. An area having a predetermined size as the center of the effective pixel area is set as the effective pixel area 701 of the imaging apparatus.

  By setting the effective pixel area of the solid-state image sensor as described above, the center of the effective pixel area of the solid-state image sensor and the light of the objective optical system can be easily measured even after the lens unit and the solid-state image sensor are assembled. An imaging device whose axis matches can be manufactured.

  In the above-described embodiment, the center of the effective pixel area is specified in the order of the horizontal position and the vertical position. However, the specification of the horizontal position and the vertical position may be performed simultaneously even if it is performed in the order of the vertical position and the horizontal position. Needless to say, the object of the present invention can be achieved.

DESCRIPTION OF SYMBOLS 301 Solid-state image sensor 302 Effective light quantity area | region 303 Light-shielding area 401 Center of solid-state image sensor 601 Center of effective light quantity area | region

Claims (4)

A step in which the solid-state imaging device captures white light;
Calculating an evaluation value of the imaging result of the white light for a pixel belonging to a central region of the solid-state imaging device;
A first measurement region, a second measurement region, and a third, which are located radially from the center of the solid-state image sensor and are located so as to include a region where the white light is imaged and a region where the white light is not imaged Measuring the evaluation value of the imaging result of the white light for the measurement region and the fourth measurement region;
The difference between the sum of the evaluation values of the first and second measurement regions and the sum of the third and fourth evaluation values is the first difference, and the sum of the evaluation values of the first and third measurement regions. Calculating a difference between the sum of the second and fourth measurement areas and a second difference;
Divide the first difference and the second difference by the evaluation value for the pixel belonging to the central area, and calculate the amount of deviation between the center of the solid-state imaging device and the area where the white light is imaged. And a process of
And a step of setting an effective pixel area centered on a position corrected by the calculated amount of deviation from the center of the solid-state image sensor. Installing the objective optical system;
Installing a solid-state image sensor;
The solid-state image sensor imaging white light;
Calculating an evaluation value of the imaging result of the white light for a pixel belonging to a central region of the solid-state imaging device;
A first measurement region, a second measurement region, and a third, which are located radially from the center of the solid-state image sensor and are located so as to include a region where the white light is imaged and a region where the white light is not imaged Measuring the evaluation value of the imaging result of the white light for the measurement region and the fourth measurement region;
The difference between the sum of the evaluation values of the first and second measurement regions and the sum of the third and fourth evaluation values is the first difference, and the sum of the evaluation values of the first and third measurement regions. Calculating a difference between the sum of the second and fourth measurement areas and a second difference;
Divide the first difference and the second difference by the evaluation value for the pixel belonging to the central area, and calculate the amount of deviation between the center of the solid-state imaging device and the area where the white light is imaged. And a process of
And a step of setting an effective pixel region centered on a position corrected by the calculated amount of deviation from the center of the solid-state image sensor. The solid-state imaging device is a CMOS sensor;
The method according to claim 1, wherein the evaluation value is based on an OB value of a Gb signal. The solid-state imaging device is a CMOS sensor;
The method of manufacturing an imaging apparatus according to claim 2, wherein the evaluation value is based on an OB value of a Gb signal.

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