JPH08159919A - Center positioning method for chart - Google Patents

Abstract

PURPOSE: To obtain a center positioning method in which an automatic adjustment can be performed by making the central position of a chart and the central position of a light-receiving part for an imaging device agree with each other precisely and by one movement and measuring the deviation amount of the center of the light-receiving part for the imaging device from the central position of the chart. CONSTITUTION: A chart 13 for center positioning is photographed by a CCD camera 11 which is connected to a personal computer 14. The chart 13 for center positioning is attached to slide tables 15, 16 so as to be movable by stepping motors 17, 18. The driving amount of the stepping motors 17, 18 is output to stepping-motor drivers 19, 20 by the personal computer 14 so as to be decided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chart center positioning device, and more particularly to a device for efficiently aligning the chart center with the center of a light receiving portion of an imaging device in consideration of optical distortion peculiar to the optical system of the imaging device. Is.

[0002]

2. Description of the Related Art Conventionally, as a method for obtaining a distortion correction function of a condenser lens of an image pickup device, for example, Japanese Patent Laid-Open No. 63-22941.
There is an invention described in Japanese Patent Publication No. 9. In the above invention, as shown in FIG. 12, the F-θ lens or the F-t lens of the image pickup apparatus 101 is used.
The laser oscillator 1 is attached to the condenser lens 102 such as an an-lens.
Scanning is performed by moving the mirrors 106 and 107 driven by the X scanner 104 and the Y scanner 105 with the laser light from 03, and the imaging device 101 is irradiated with the laser light via the condenser lens 102. This imaging device 10
The ideal scanning position on the light receiving element of No. 1 and the actual shift amount are detected, and the distortion correction function is obtained by the arithmetic processing unit 108 from this shift amount.

Using the above method, the laser oscillator 10
3, the XY scanners 104, 105 are switched to the chart 109, and the chart 109 is imaged on the light receiving portion of the image pickup device 101 via the condenser lens 102. This chart 1
Since the center position can be discriminated in 09, the amount of deviation between the center of the light receiving unit of the image pickup apparatus 101 and the center of the chart 109 is detected, and the center position of the chart 109 and the center of the light receiving unit of the image pickup apparatus 101 are detected using the distortion correction function obtained previously. An accurate shift amount from the position is calculated by the arithmetic processing unit 108, and based on the calculation result, the chart 109 or the image pickup apparatus 101 is moved by the drive unit 111 via the drive unit controller 110 to perform centering. It is possible.

As another method, as shown in FIG. 13, the center positioning chart 123 is formed on the light receiving portion of the image pickup device 121 via the optical system 122, and the image is displayed on the monitor 126, so that the operator can While manually observing the center positioning chart 123 via the monitor 126, a two-dimensionally movable chart moving device 125 is manually moved to match the center of the chart 123 with the center of the light receiving portion of the image pickup device 121. is there.

[0005]

However, each of the above prior arts has the following drawbacks. That is, in the invention described in Japanese Patent Laid-Open No. 63-229419, in order to obtain the distortion correction function of the inherent optical distortion, light is once projected onto the imaging lens at a predetermined scanning pitch to perform ideal scanning. It is necessary to find the amount of deviation between the position and the actual scanning position. After obtaining the distortion correction function, the chart center position and the accurate center position of the image sensing device light receiving unit are made to coincide with each other.

Further, in the other method in the above-mentioned prior art, since the operator visually performs center positioning, the accuracy cannot be stabilized, and it is difficult to automate this operation.

It is an object of the present invention to set a distortion correction function for correcting the optical distortion of a lens in advance, thereby improving the correction accuracy and shortening the working time by automating the adjustment. It is in the provision of methods.

[0008]

FIG. 1 is a flowchart showing the concept of the present invention, which will be described with reference to FIG. Claim 1
The center position setting method for the charts described above includes an image pickup device installed so as to capture an image of the center position setting chart, a means for detecting a deviation amount between the center position setting chart and the center of the image pickup device, and an image pickup device combination. A means for calculating the error due to the distortion from the distortion correction function of the image lens, a means for calculating the difference between the deviation amount of the center position chart and the center position of the image pickup apparatus and the error due to the distortion from the distortion correction function, and the difference value. Is a chart for centering or a driving device capable of moving the imaging device two-dimensionally in a plane perpendicular to the optical axis of the imaging device.

[0009]

According to the operation of claim 1, as shown in FIG. 1, the chart for centering having a positioning mark at the center is photographed by the image pickup device (first step), and the chart and the center of the light receiving part of the image pickup device are formed. The amount of deviation from the center of the
Steps). Then, the error due to the distortion of the imaging device imaging lens is calculated by the distortion correction function (third step). Further, the difference between the deviation amount and the error due to the distortion is calculated (fourth step), and the result can be two-dimensionally moved in a plane perpendicular to the optical axis of the image pickup device or the image pickup device for centering. It moves by various driving devices (5th
By performing the steps, the center of the light receiving portion of the image pickup device and the center of the chart can be matched.

The distortion correction function of the third step of claim 1 will be described below. The distortion correction function is represented by the following equations (1) and (2).

[0011]

[Equation 1]

[0012]

[Equation 2]

The proof of the above equations (1) and (2) is shown below. When K = 1, the equation of Equation 1 is h = f · sin θ
Indicates the type. When K = ∞, the formula (1) is transformed (sin is expanded) to obtain the formula (3).

[0014]

(Equation 3)

Here, 0 except for the second term on the right side of K = ∞.
Therefore, h = f · θ. Therefore, the equation (1) can represent an intermediate optical distortion characteristic between the fsin θ type and the fθ type, and the constant K at this time is determined by the equation (4).

[0016]

[Equation 4]

Similarly, the relationship between the image height h and the half-incidence angle θ can be expressed by equation 2 for an imaging lens having an optical distortion characteristic intermediate between those of the ftan θ type and the fθ type. In this case, the value of K is Equation 5.

[0018]

(Equation 5)

Here, which of the equations (1) and (2) should be used depends on whether the imaging lens of the image pickup device has an optical distortion characteristic intermediate between fsin θ type and fθ type or ftan θ.
The discriminant is determined by the following equation, although it is determined by having an optical distortion characteristic intermediate between that of the mold and that of the fθ type. (Hmax /
When f-θmax) <0, the distortion correction function obtained by the formula of Formula 1 is used, and when (hmax / f-θmax)> 0, Formula 2 is used.
The distortion correction function obtained by the equation is used (where θmax is the maximum half field angle and hmax is the image height at that time). By using the distortion correction function obtained by these equations, the center of the chart and the center position of the light receiving unit of the imaging device can be positioned.

According to such an apparatus, it is not necessary to scan the light receiving section of the image pickup device with light to detect the data at each point, and the distortion correction function of the image pickup optical system can be easily obtained. Furthermore, if this function is stored in the memory, it is easy to detect the amount of deviation between the chart center position and the center position of the image sensing device light receiving unit when centering is performed using lenses with the same characteristics. Center alignment is possible.

[0021]

Embodiment 1 Hereinafter, this embodiment will be described in detail with reference to the drawings. FIG. 2 is a schematic configuration diagram showing an image pickup device resolving power measuring device provided with a chart center position determining device, FIG. 3 is a chart diagram for center position determining used in this device, and FIG. 4 is a center position of the second step of claim 1. It is explanatory drawing which shows the method of the Example which detects the shift amount of the output chart and the center part of an imaging device.

In the measuring instrument of this embodiment, a CCD camera 11 having a mechanically positioned and fixed imaging lens 12 is used to photograph the center positioning chart 13.
At this time, the image of the chart 13 is taken into the personal computer 14. The center position chart 13 is attached to two slide tables 15 and 16 which are movable in the x direction and the y direction. The slide tables 15 and 16 can be moved by stepping motors 17 and 18, respectively. There is. The drive amount of the stepping motors 17 and 18 is the pulse of the movement amount of the chart 13 by the personal computer 14.
x and y direction stepping motor drivers 1
It is output to 9 and 20 and determined.

Further, the center position determination chart 13 includes
As shown in FIG. 3, the horizontal line 26 and the horizontal line 26
There is a line 27 that is perpendicular to, and these two straight lines intersect at the center of the chart. Further, the two straight lines are missing at the center of the chart 13, and the missing parts are provided with a drawing 21 for measuring the resolution according to JIS B-7174.

The operation of this embodiment will be described below. CCD
Chart 1 for centering imaged by the camera 11
The video signal of No. 3 is taken into the personal computer 14. The personal computer 14 stores the brightness value at each chart position in the memory of the person 14. In addition, as shown in FIG. 4, the CCD camera 1 uses the data stored in the memory.
Windows 2 on the top and bottom and on the left and right on the light receiving element of No. 1
2, 23, 24, and 25 are set, and it is determined which of the four locations each has a line. Of which, the upper and lower parts 2
The coordinates of the vertical line 27 in each of the windows 22 and 23 are found and the formula of a straight line passing through the two points is found. Similarly, a straight line expression is obtained from the coordinates where the horizontal line 26 exists in the windows 24 and 25 at the two right and left portions.

The coordinates of the intersections of the two straight lines can be obtained from the above two equations, and the coordinates of the obtained intersections are the coordinates of the center of the chart 13, and the amount of deviation from the center of the light receiving element of the CCD camera 11 is obtained. be able to. However, the image forming lens 1 of the CCD camera 11 is included in the deviation amount calculated here.
The error due to the optical distortion of No. 2 is included, and when the slide tables 15 and 16 are moved as they are, the center position of the chart 13 and the center position of the light receiving portion of the CCD camera 11 are displaced by the error portion of the optical distortion. Therefore, an accurate movement amount is calculated from the shift amount on the light receiving surface of the CCD camera 11 by the following distortion correction function.

For example, assuming that the distance between the image forming lens 12 and the chart 13 is 20 mm and the image forming lens 12 having an optical specification of a maximum half field angle π / 2 and a focal length of 0.5 mm is used, this image If the height is 1.0 mm, the discriminant = (1 / 0.5−π / 2)> 0, and therefore the formula 2 is used. Here, substituting hmax = 1, f = 0.5, and θmax = π / 2 into the formula 5 to obtain the constant K results in K = 1 and K = 1.94762.
Therefore, the distortion correction function of Equation 6 is calculated in this imaging lens.

[0027]

(Equation 6)

Further, in the present embodiment, the amount of deviation between the center of the centering chart and the light receiving portion of the image pickup device is dx = 0.1 mm and dy = 0 in the x and y directions on the light receiving portion of the CCD camera 11, respectively. When it is 0.2 mm, an accurate amount of movement in the x direction is first calculated. dx = 0.1 mm,
From dy = 0.2 mm, the shift amount between the center of the chart and the center of the light receiving unit on the light receiving unit of the camera 11 dz = 0.223606
It becomes 79. Therefore, 0.2236067 is added to h in the equation (6).
By substituting 9, the half incident angle θ can be obtained. Therefore, θ = 0.439593365 (rad).

Further, since the distance between the chart and the imaging device imaging lens at this time is 20 mm, the deviation amount Δz between the chart center and the imaging device optical axis center is Δz / 20 = tan.
From 0.43953365, Δz = 9.4024188
It becomes 63 mm. Here, when the x component of Δz is Δx and the y component of Δz is Δy, the following two expressions are established. Δz ² = Δx ² + Δy ² Δy = 2Δx (where Δx> 0, Δy> 0, Δz> 0)

Therefore, from the above two equations, Δx = 4.205694531 mm and Δy = 8.411389062 mm. By moving this shift amount with the slide tables 15 and 16, it is possible to match the centers of the slide tables.

Further, when measuring the resolving power which is the lens performance, there is a method of expressing the contrast value using a resolving power measuring chart (hereinafter referred to as a chart) 21. The brightness values of the white part and the black part in the chart 21 are required as parameters necessary for obtaining the contrast value. Therefore, it is possible to determine the brightness value of the white portion and the black portion of the chart 21 from the one scanning line video signal on the chart 21 by the video signal when the chart 21 is photographed, and to measure the contrast value. become.

Therefore, since the chart 21 is at the same position every time the contrast value is measured, it is possible to determine the brightness values of the white and black portions of the chart 21 from the same scanning line video signal. . The series of operations are processed by the personal computer 14, and the slide tables 15 and 16 can also be automated by outputting the movement amount in pulses from the personal computer 14.

According to this embodiment, the resolving power is measured after the center position of the chart is measured. Therefore, the scanning line to be measured always hits on the resolving power measuring chart, so that the measurement can be performed without causing a measurement error. It was

[0034]

[Embodiment 2] Hereinafter, this embodiment will be described in detail with reference to the drawings. FIG. 5 is a schematic configuration diagram showing an angle-of-view measuring device equipped with a chart center positioning device, FIG. 6 is a chart diagram used in this example, FIG. 7 is a flowchart showing an angle-of-view measuring method in this example, and FIG. 9A and 9B are explanatory views of the view angle measuring method in this embodiment.

In the measuring instrument of this embodiment, the center positioning chart 33 is attached to slide tables 35 and 36 which are movable in the x and y directions in the figure. And
The slide tables 35 and 36 are movable by stepping motors 37 and 38, respectively, and the stepping motor drivers 39 and 40 rotate the stepping motors 37 and 38, respectively. Further, in this embodiment, a slide table 42 in the z direction is installed so that the distance between the CCD camera 31 which is an image pickup device and the chart 33 can be adjusted, and the slide tables 35 and 3 in the x and y directions are installed.
Similar to 6, the mechanism is movable by the stepping motor 43 and operated by the stepping motor driver 44. Then, the output image of the CCD camera 31 is taken into the personal computer 34 and subjected to predetermined processing.

Further, as shown in FIG. 6, the center positioning chart 33 has a circular graphic 41 drawn at the center. The size of the figure 41 is imaged on the entire light receiving portion of the CCD camera 31 through the imaging lens 32 when the center position determination chart 33 is brought sufficiently close to the CCD camera 31 by the z-direction slide table 42. It is about the size.

As described above, in the present embodiment, the z-direction slide table 42 capable of adjusting the distance between the CCD camera 31 and the centering chart 33 and the centering chart 33 are added to the construction of the first embodiment. A circular figure 41 for measuring the angle of view is added.

The operation of this embodiment will be described below. As described in the first embodiment, the center position of the light receiving element of the CDD camera 31 and the center position of the center position setting chart 33 are matched by the image output signal of the center position setting chart 33 captured by the CCD camera 31. Let

Further, a flow chart for measuring the angle of view of the CCD camera 31 is shown in FIG. 7, and the angle of view measuring method will be described. First, by shortening the distance between the CCD camera 31 and the center position chart 33,
The circular figure 41 on the chart 33 is imaged on the entire light receiving portion of the CCD camera 31. From this position, C
The chart 33 is moved by the z-direction slide table 42 by a certain distance in the direction in which the distance between the CD camera 31 and the center position setting chart 33 is increased. At this position, the video signal of the CCD camera 31 is again taken in by the personal computer 34, and as shown in FIG.
It is determined whether or not there are round-shaped figures 41 on the chart at the four corners 42, 43, 44, and 45.

When these operations are repeated, as shown in FIG. 9, the four corners 4 of the light receiving portion 46 of the CCD camera 31 are shown.
2, 43, 44, and 45 have positions where the round figure 41 on the chart is missing. The distance between the light receiving portion of the CCD camera 31 and the center position setting chart 33 at this time is calculated from the movement amount of the z-direction slide table 42. Based on this result and the size of the circular figure on the chart, it is possible to measure the angle of view of the imaging lens 32 of the CCD camera 31, which is the measurement target.

This embodiment is a method for measuring an accurate angle of view when the angle of view of the condenser lens is different when compared with the design value, and of course, the angle of view of the distortion correction function is used. The design value will be used for the parameter. With the method of this embodiment, the angle of view of the lens to be inspected can be automatically measured with a reliable and simple measurement configuration. Further, it goes without saying that in the configuration of the present embodiment, the centering chart is replaced with that of the first embodiment to provide a resolving power measuring device having a variable measurement distance.

[0042]

Third Embodiment The present embodiment will be described in detail below with reference to the drawings. FIG. 10 is a schematic configuration diagram showing an image tilt measuring device equipped with a chart center positioning device, and FIG. 11 is a chart diagram used in this embodiment. By the way, the "image tilt measuring device" referred to in the text is a measurement that measures whether or not the image sensor is mounted horizontally with respect to the housing that supports the image sensor, and how much the image sensor is displaced when it is not horizontal. Says the vessel.

In the measuring instrument of this embodiment, the center positioning chart 53 is attached to slide tables 55 and 56 which are movable in the x and y directions in the figure.
The slide tables 55 and 56 are movable by AC servomotors 57 and 58, respectively. Also,
The CCD camera 51 of the image pickup device has a mechanical positioning mechanism for photographing the central portion of the chart.
It is fixed to.

Further, the output video signal of the CCD camera 51 is connected to an image processing device 67 capable of calculating the barycentric coordinates of the pattern. The image processing device 67 is connected to the personal computer 54 for processing data. The personal computer 54 is connected to AC servo motor drivers 59 and 60, respectively, for controlling the AC servo motors 57 and 58. As shown in FIG. 11, the details of the center position setting chart 53 in this embodiment include a circular figure 61 at the center position, and four square figures 6 at the top, bottom, left and right.
2, 63, 64 and 65 are drawn.

The operation of this embodiment will be described below. CCD
Chart for centering 5 taken by the camera 51
The image of No. 3 is captured by the image processing device 67. The pattern matching function of the image processing device 67 searches for the position of the circular figure 61 at the center of the centering chart 53. Further, the barycentric coordinates of the round figure 61 are obtained, and the result is transferred to the personal computer 54 of the arithmetic processing unit.

Then, the amount of deviation between the accurate center position of the center positioning chart 53 and the center position of the light receiving portion of the CCD camera 51 is calculated by the personal computer 54 using the distortion correction function. The calculated deviation amount is the AC servo motor 57, 58.
The number of pulses corresponding to the amount of deviation is converted from the personal computer 54 and output to the AC servomotors 57 and 58. Thus, the center position of the center position chart 53 and the CCD
The center position of the light receiving element portion of the camera 51 matches.

Further, in the present embodiment, in order to measure the image tilt, the barycentric coordinates of each of the square figures 62, 63, 64, 65 installed on the upper, lower, left and right sides of the center positioning chart 53 are used to determine the image center 67. Ask by. The data of these four barycentric coordinates are transferred to the personal computer 54, and the amount of image tilt can be obtained by calculating the amount of deviation either vertically or horizontally.

According to this embodiment, it is possible to easily and surely measure the image tilt.

[0049]

According to the first aspect of the present invention, when the light from the chart is received by the image pickup device light receiving portion through the image forming lens having a distortion, and when the shift amount of the chart is judged, the center position setting chart is used. The chart center position and the center position of the image sensing device light receiving unit are accurately matched by one movement by obtaining the difference between the deviation amount of the center portion of the image sensing device and the error due to the distortion obtained by the distortion correction function. It becomes possible. Further, the video signal is fed back to measure the amount of deviation between the center of the light receiving section of the image pickup device and the center position of the chart, thereby enabling automatic adjustment.

[Brief description of drawings]

FIG. 1 is a flowchart showing the concept of the present invention.

FIG. 2 is a schematic configuration diagram showing a first embodiment.

FIG. 3 is a chart showing Example 1.

FIG. 4 is an explanatory view showing the first embodiment.

FIG. 5 is a schematic configuration diagram showing a second embodiment.

FIG. 6 is a chart showing Example 2.

FIG. 7 is a flowchart showing a second embodiment.

FIG. 8 is an explanatory diagram showing a second embodiment.

FIG. 9 is an explanatory diagram showing a second embodiment.

FIG. 10 is a schematic configuration diagram showing a third embodiment.

FIG. 11 is a chart showing Example 3;

FIG. 12 is a schematic configuration diagram showing a conventional example.

FIG. 13 is a schematic configuration diagram showing a conventional example.

[Explanation of symbols]

 11 CCD camera 12 Imaging lens 13 Chart for centering position 14 Personal computer 15,16 Slide table 17,18 Stepping motor 19,20 Stepping motor driver

Claims (1)

[Claims] 1. A method for centering a center of a chart for aligning the center of a chart with the center of a light receiving portion of an image pickup device, comprising: a first step of photographing a centering chart having a positioning mark at the center by an image pickup device; A second step of detecting the amount of deviation between the centering chart and the center of the image pickup device based on the video signal output in step, and h = f · Ksin (θ / k) or h =
f · Ktan (θ / k) <however, h: image height, f: focal length, θ: half incident angle, K: constant> A third step of calculating an error, and a fourth step of performing a difference between the error due to the distortion calculated in the third step and the deviation amount.
And a fifth step of moving the difference value obtained in the fourth step by the driving device capable of moving the chart or the image pickup device two-dimensionally in a plane perpendicular to the optical axis of the image pickup device. How to find the center position of the characteristic chart.