JP2003307661A - Lens eccentricity adjusting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens eccentricity adjusting method capable of adjusting the eccentricity of a lens very accurately. <P>SOLUTION: The focusing position of the center part of the lens is obtained by segmenting the center part and the four corners of an eccentricity confirming chart in procedure T1 to procedure T4. The correction coefficient of a luminance value is calculated in procedure T7, and the lens is moved so that respective resolution evaluated values on a low band side and respective resolution evaluated values on a high band side may be within a specified range with the focusing position as reference based on the correction coefficient in procedure T9 and procedure T11. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens eccentricity adjusting method for adjusting the eccentricity of a lens forming a camera for forming an image of a subject on a solid-state image pickup device.

[0002]

2. Description of the Related Art Conventionally, in a manufacturing process of a camera including a solid-state image pickup device such as a CCD image pickup device and a lens for forming an image of a subject on the solid-state image pickup device, a lens mounted on the camera is Work to adjust the eccentricity is performed. To adjust the eccentricity of the lens, display the image corresponding to the resolution chart on the monitor while continuously shooting the predetermined resolution chart by the jig camera with the lens to be adjusted attached, and center the image. The lens is manually adjusted in the optical axis direction or in a plane intersecting the optical axis direction while visually confirming that the number of resolutions at the parts and the four corners is within a predetermined range.

[0003]

However, in the above-mentioned conventional lens decentering adjustment method, the number of resolutions is predetermined while visually confirming the number of resolutions at the central portion and the four corners of the image corresponding to the resolution chart. Since the lens is manually adjusted to be within the range of
There is a problem that it is difficult to adjust the eccentricity of the lens with high accuracy because the person who adjusts the eccentricity of the lens varies.

In view of the above circumstances, it is an object of the present invention to provide a lens eccentricity adjusting method capable of adjusting the eccentricity of a lens with high accuracy.

[0005]

The lens eccentricity adjusting method of the present invention for achieving the above object constitutes a camera provided with a solid-state image sensor and a lens for forming an image of a subject on the solid-state image sensor. In the lens decentering adjustment method for adjusting the decentering of the lens, a first pattern having a first spatial frequency and a second pattern having a second spatial frequency higher than the first spatial frequency are provided. A pair of eccentricity confirmation charts arranged in the center and four corners within the angle of view are prepared, and while the eccentricity confirmation chart is imaged on the solid-state imaging device through the lens, the center of the eccentricity confirmation chart The first step of obtaining the resolution evaluation value obtained from the pair and moving the lens in the optical axis direction so that the resolution evaluation value becomes maximum and the pair of the central portion and the four corners of the eccentricity confirmation chart A second step of moving the lens in a plane intersecting the optical axis of the lens such that each of the first resolution evaluation values obtained from each of the first patterns formed is within a predetermined first range; The lens is flat so that each second resolution evaluation value obtained from each second pattern forming each of the center portion and the four corner pairs of the eccentricity confirmation chart falls within a predetermined second range. And a third step of moving within.

The lens eccentricity adjusting method of the present invention obtains the in-focus position of the lens center by executing the first step, and the eccentricity confirmation is performed in the second and third steps with reference to this in-focus position. Each first resolution evaluation value (resolution evaluation value on the low frequency side) of each of the center part of the chart and the four corners,
Since each second resolution evaluation value (resolution evaluation value on the high frequency side) is adjusted to be substantially the same, the eccentricity of the lens can be uniformly adjusted based on the numerical value. Therefore, the eccentricity of the lens can be adjusted with high accuracy as compared with the conventional method of adjusting the eccentricity of the lens while visually confirming the number of resolutions.

Here, in preparing the eccentricity confirmation chart, an eccentricity confirmation patch in which a patch having a predetermined reference density is arranged near each pair is prepared.
Prior to the execution of the second step and the third step, a fourth step of measuring the brightness of each patch in the vicinity of each of the pairs is executed, and the second step and the third step include the fourth step. It is preferable to obtain each of the first resolution evaluation value and each of the second resolution evaluation values corrected based on the brightness of the patch in the vicinity of each pair measured in the step.

With this arrangement, in obtaining the first resolution evaluation value and the second resolution evaluation value in the second step and the third step, the drop of the peripheral light amount of the lens and the illumination in the eccentricity confirmation chart are obtained. The influence of unevenness can be reduced.

[0009]

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

FIG. 1 is a diagram showing an eccentricity confirmation chart in a lens eccentricity adjustment method according to an embodiment of the present invention and a lens eccentricity adjustment device to which a lens constituting a camera is attached.

FIG. 1 shows an eccentricity confirmation chart 10 and a lens eccentricity adjusting device 30 to which a lens 20 constituting a camera is attached. Lens eccentricity adjusting device 30
A CCD image pickup device 31, an image processing unit 32 having a monitor, and an adjustment mechanism unit 33 are provided in the. In the lens eccentricity adjustment method of the present embodiment, the eccentricity of the lens 20 is adjusted by using the eccentricity confirmation chart 10.
Then, adjust as follows.

First, the eccentricity confirmation chart 10 will be described with reference to FIG.

FIG. 2 is a diagram showing the structure of the eccentricity confirmation chart shown in FIG.

In the eccentricity confirmation chart 10 shown in FIG. 2, the first pattern having a relatively low resolution (corresponding to the first pattern having the first spatial frequency according to the present invention) and the lens 2 are shown.
Modulation transfer function (MTF: Modulation T
A pair with a second pattern having a relatively high resolution (corresponding to a second pattern having a second spatial frequency higher than the first spatial frequency according to the present invention) close to the limit of transfer function is the bias. They are arranged at the four corners and the center within the angle of view of the lead confirmation chart 10. Specifically, the first pattern 11_1 and the second pattern 12_1 have the first pattern 11_1 and the second pattern 12_1 on the upper right portion; the upper left portion; the central portion; the lower right portion; and the lower left portion of the eccentricity confirmation chart 10, respectively.
_2, a second pair of second patterns 12_2; a first pattern 11_3, a third pair of second patterns 12_3; a first pattern 11_4, a fourth pattern of second patterns 12_4
Pair; first pattern 11_5, second pattern 12_
A fifth pair of five is arranged.

Further, the eccentricity confirmation chart 10 includes
On the upper part of the first, second, third, fourth and fifth pairs, patches 13_1, 13_2, 13_3, 13_ of solid gray color are formed.
4, 13_5 (corresponding to a patch having a predetermined reference density according to the present invention) are arranged. Note that the patch 13_1 and the first pair, the patch 13_2 and the second pair, the patch 13_3 and the third pair, and the patch 13_4 and the fourth pair.
The pair and the patch 13_5 and the fifth pair correspond to the eccentricity confirmation patch in which the patch having the predetermined reference density according to the present invention is arranged. In the present embodiment, using the eccentricity confirmation chart 10 as described above, the lens 2 is subjected to the following steps.
Adjust the eccentricity of 0.

FIG. 3 is a diagram showing the procedure of the lens decentering adjustment method of this embodiment.

First, the eccentricity confirmation chart 10 described above is prepared, and the eccentricity confirmation chart 10 is passed through the lens 20 to C
While forming an image on the CD image pickup device 31, the image processing unit 32
Image data is obtained with and image processing is performed according to the following procedure.

First, in step T1, the central portion and four corners of the eccentricity confirmation chart 10 are cut out.

Next, in step T2, the cut-out image data of each portion is vertically divided into three parts.

Further, proceeding to step T3, the image data divided into three are designated as data A, data B and data C. Here, the data A is a solid gray portion (patch 13_1, 1
3_2, 13_3, 13_4, 13_5), and the data B has a relatively low resolution (first pattern 11_).
1, 11_2, 11_3, 11_4, 11_5), and data C has a relatively high resolution (second patterns 12_1, 12_2, 12_3, 12_4, 12_5).
Part).

Next, the process proceeds to step T4. In this procedure T4, the brightness level in the data A of each image is calculated, and the average value thereof is obtained (corresponding to the fourth step in the present invention). Let these values be a1 to a5. Here, a1 is a value displayed on the monitor of the image processing unit 32 in the upper right part of the screen (hereinafter, simply referred to as screen) corresponding to the eccentricity confirmation chart 10, a2 is a value in the upper left part of the screen, and a3 is a screen. The central value, a4 is the lower right value of the screen, and a5 is the lower left value of the screen (see FIG. 2).

In step T4, the lens 20 is moved in the optical axis direction by the adjusting mechanism section 33 (first in the present invention).
The image processing unit 32 searches for the peak of the resolution evaluation value obtained from the pair 11_3 and 12_3 in the central portion of the eccentricity confirmation chart 10. The position at this peak is the in-focus position of the center of the lens 20 (the subsequent movement of the lens 20 is based on this in-focus position).

Further, in step T5, a new result is obtained by passing the data B of each image through a low-pass filter, and the results are integrated. The respective integrated values are set to b1 to b5 (the integrated values are normalized by the data size). Here, b1 is the value in the upper right part of the screen, b2 is the value in the upper left part of the screen, b
3 is the value at the center of the screen, b4 is the value at the lower right of the screen, and b5 is the value at the lower left of the screen (see FIG. 2).

Further, in step T6, a new result is obtained by passing the data C of each image through a high-pass filter, and the results are integrated. The respective integrated values are set to c1 to c5 (the integrated values are normalized by the data size). Here, c1 is the value in the upper right part of the screen, c2 is the value in the upper left part of the screen, c
3 is the value at the center of the screen, c4 is the value at the lower right of the screen, and c5 is the value at the lower left of the screen (see FIG. 2).

In step T7, the correction coefficient of the brightness value is calculated using the above-mentioned values a1 to a5 in order to remove the influence of the shading of the lens 20 and the lighting (unevenness of illumination). The correction coefficient of the brightness value is calculated by the following formula.

Α1 = a1 / a3 α2 = a2 / a3 α3 = 1 α4 = a4 / a3 α5 = a5 / a3 The correction coefficient for these luminance values is obtained by normalizing the resolution evaluation value with reference to the central brightness. It is used as a coefficient to do.

In step T8, the resolution evaluation value on the low frequency side is calculated. Here, a low pass filter (LPF: Low P)
The value of the image data passed through the ass filter) is integrated, and the value averaged by the number of pixels is multiplied by the reciprocal of α calculated in step T7 to calculate the evaluation value of the resolution on the low frequency side. Let these values be β1 to β5, respectively.

Β1 = b1 / α1 β2 = b2 / α2 β3 = b3 β4 = b4 / α4 β5 = b5 / α5 Next, in step T9, the calculated resolution evaluation value on the low frequency side is within a predetermined range (the present invention). Within the predetermined first range referred to in
The lens 20 is moved by the adjusting mechanism 33 in the plane intersecting the optical axis of the lens 20 (corresponding to the second step in the present invention). In this way, the eccentricity of the lens 20 is roughly adjusted.

Further, in step T10, the resolution evaluation value on the high frequency side is calculated. Here, a high-pass filter (HP
F: High Pass Filter), the values of the image data are integrated, and the value averaged by the number of pixels is added to the procedure T.
The evaluation value of the resolution on the high frequency side is calculated by multiplying the reciprocal of α calculated in 7. Let these values be γ1 to γ5, respectively.

Γ1 = c1 / α1 γ2 = c2 / α2 γ3 = c3 γ4 = c4 / α4 γ5 = c5 / α5 Finally, in step T11, the calculated resolution evaluation value on the high frequency side is within a predetermined range (the present invention). The lens 20 is moved within the plane intersecting the optical axis of the lens 20 by the adjusting mechanism portion 33 so as to be within the predetermined second range (in FIG. 3) (corresponding to the third step in the present invention). In this way, the lens 2
Adjust the eccentricity of 0. Lens 20 with eccentricity adjusted
Is fixed to the lens frame with an adhesive.

As described above, in the lens decentering adjustment method of this embodiment, the in-focus confirmation chart 10 is used to find the in-focus position of the center of the lens 20 (procedure T4), and the in-focus position is used as a reference for lowering the in-focus position. The eccentricity of the lens 20 is objective because the lens 20 is moved so that each resolution evaluation value on the high frequency side and each resolution evaluation value on the high frequency side are within a predetermined range (procedures T9 and T11). It will be adjusted uniformly based on the numerical values. Therefore, compared with the conventional method of adjusting the eccentricity of the lens while visually confirming the number of resolutions, the eccentricity of the lens can be automatically adjusted with high accuracy. Further, since the correction coefficient of the brightness value is calculated (procedure T7) and the resolution evaluation value on the low frequency side and the resolution evaluation value on the high frequency side are calculated based on this correction coefficient, the peripheral light amount of the lens 20 is calculated. It is possible to suppress the influence of unevenness in illumination and uneven illumination on the eccentricity confirmation chart.

In this embodiment, the movement of the lens 20 is automatically moved by moving the adjustment mechanism 33.
Although the example of adjusting the eccentricity of 0 has been described, the lens 20 may be manually moved.

[0033]

As described above, according to the present invention,
The eccentricity of the lens can be adjusted with high accuracy.

[Brief description of drawings]

FIG. 1 is a diagram showing an eccentricity confirmation chart in a lens eccentricity adjustment method according to an embodiment of the present invention and a lens eccentricity adjustment device to which a lens constituting a camera is attached.

FIG. 2 is a diagram showing a configuration of an eccentricity confirmation chart shown in FIG.

FIG. 3 is a diagram showing a procedure of a lens decentering adjustment method of the present embodiment.

[Explanation of symbols]

10 Eccentricity confirmation chart 11_1, 11_2, 11_3, 11_4, 11_5
First patterns 12_1, 12_2, 12_3, 12_4, 12_5
Second patterns 13_1, 13_2, 13_3, 13_4, 13_5
Patch 20 Lens 30 Lens eccentricity adjusting device 31 CCD image sensor 32 Image processing unit 33 Adjustment mechanism unit

Claims (2)

[Claims] 1. A lens eccentricity adjusting method for adjusting the eccentricity of the lens, which constitutes a camera including a solid-state imaging device and a lens for forming an image of a subject on the solid-state imaging device. An eccentricity confirmation chart in which a pair of a first pattern having a spatial frequency and a second pattern having a second spatial frequency higher than the first spatial frequency is arranged at the center and four corners within the angle of view. While preparing the eccentricity confirmation chart through the lens to form an image on the solid-state image sensor, a resolution evaluation value obtained from a pair of central portions of the eccentricity confirmation chart is obtained to maximize the resolution evaluation value. The first resolution evaluation value obtained from the first step of moving the lens in the optical axis direction and the first resolution evaluation values obtained from the first patterns forming each of the center portion and the four corner pairs of the eccentricity confirmation chart are predetermined. A second step of moving the lens in a plane intersecting the optical axis of the lens so as to be within a first range of, and each second pattern forming a pair of the central portion and four corners of the eccentricity confirmation chart. And a second step of moving the lens within the plane so that each of the second resolution evaluation values obtained from the above is within a predetermined second range. . 2. When preparing the eccentricity confirmation chart, an eccentricity confirmation patch in which a patch having a predetermined reference density is arranged near each of the pairs is prepared, and the second step and the third step are performed. Prior to the execution of the fourth step of measuring the brightness of each patch in the vicinity of each of the pairs, the second step and the third step include the fourth step.
The first resolution evaluation value and the second resolution evaluation value, respectively, which are corrected based on the brightness of the patch near each pair measured in the step, are obtained. 1. The lens eccentricity adjustment method described in 1.