JP2000214368A - Method and device for adjusting optical axis of lens system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically adjust the optical axis of a lens system. SOLUTION: The linear pattern in two directions of a chart 24 is image- formed on the image pickup surface of a sensor 5 through a lens system F including a lens F1 being a lens to be adjusted, a coma flare amount caused by eccentricity of the lens F1 is calculated from the distribution of the illuminance of two pairs of linear chart images, and eccentricity correction amount is obtained, so that XY fine adjustment stage 12 is driven to finely adjust the lens F1. Then, a stage for coarse adjustment where the lens F1 is moved stepwise so as to set a fine adjustment range from the data string of maximum luminance is provided before the fine adjustment stage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens system optical axis adjusting method and a lens system optical axis adjusting device used when assembling optical elements such as a camera lens and an 8 mm video camera lens.

[0002]

2. Description of the Related Art In recent years, demands for downsizing optical elements such as camera lenses and 8-mm video lenses have been increasing, and aspherical lenses have been frequently used. In such a lens system, the amount of eccentricity allowed for one lens is within several microns, and such optical performance cannot be guaranteed only by the processing accuracy of parts (lens barrel, lens). Optical axis adjustment is required when assembling the lens system.

For example, when mounting four single-crystal lenses on a lens frame or the like, it is necessary to match the optical axes of the single-crystal lenses. In particular, in the case of an APS camera lens, the optical axis of each lens is decentered. It is required to be coaxially matched within the range of a few microns.

FIG. 19 shows a conventional optical axis adjustment of a lens system.
1 shows a device, in which the light source 100
Projection lens 101 and resolution chart 102 installed below
The chart image is collimated by the lens system L to be adjusted.
Image on CCD camera 104 via meter lens 103
Is done. The lens system L is under assembly and the single crystal lens L _Two 
~ L_Four Is already fixed to the ball frame T, and the topmost single crystal
Lens L₁ Only the state is not fixed.

When the chart image passes through the lens system L,
Crystal lens L_Two ~ L_Four And single crystal lens L ₁ The optical axes of
If there is, the chart image on the camera monitor is resolved and observed.
It is. If the chart image is observed without resolution,
Single crystal lens L so that the chart image is resolved.₁ In the XY directions
Fine adjustment, and when the adjustment is completed, single crystal lens L₁ The ball frame
Fix to T with adhesive.

[0006]

However, according to the above-mentioned conventional example, since the operator adjusts the fine movement of the lens while visually observing the chart image, skill is required to determine the resolution. , Lack mass production. In addition, the adjustment results also differ from individual to individual, and it is difficult to make a visual judgment of 5 μm or less, and a mistake in judgment occurs due to fatigue or the like, resulting in poor reliability.

The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and detects the eccentric state of a lens system with high speed and high accuracy, and automatically adjusts the optical axis of the lens system. Accordingly, it is an object of the present invention to provide a high-performance lens system optical axis adjustment method and a lens system optical axis adjustment device that can directly fix the adjusted lens.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, a lens system optical axis adjusting apparatus according to the present invention comprises a fine adjustment unit for finely moving an adjusted lens system two-dimensionally perpendicularly to the optical axis of the optical system. Driving stage means, a chart having a linear pattern in two directions perpendicular to the optical axis, and projecting the linear pattern in the two directions of the chart to a sensor via the lens system to be adjusted to form two sets of linear chart images. A projection optical system to be obtained, an illuminance distribution of the two sets of linear chart images respectively detected in the two directions, a calculating means for calculating a coma flare amount centered on the strongest illuminance point from each illuminance distribution, and Control means for controlling the fine drive stage means based on the obtained eccentricity correction amount, and moving the lens system to be adjusted to form the two sets of linear chart images at each of a plurality of positions. It characterized by having a storage means for storing a large illuminance value.

The method of adjusting the optical axis of a lens system according to the present invention comprises the steps of: holding a lens system to be adjusted in the optical path of the optical system; arranging a chart having a two-way linear pattern in the optical path; Projecting the linear pattern in the two directions to the sensor through the steps of: detecting the illuminance distribution of the two sets of projected linear chart images in the two directions, and calculating the amount of coma flare centered on the point of strongest illuminance And a step of finely adjusting the adjusted lens system based on the eccentricity correction amount obtained from the calculated coma flare amount, and moving the adjusted lens system to move each linear chart image at each of a plurality of positions. A step of detecting the maximum illuminance value and performing a coarse adjustment for determining a reference position based on the obtained data string.

[0010]

When the optical axis of the lens system to be adjusted and the optical axis of the fixed lens system, which is the optical system fixed to the lens barrel, are in an eccentric state, two sets of linear charts projected to the sensor of the projection optical system. Since the illuminance distribution of at least one of the images is uneven right and left around the point of strongest illuminance, this unevenness is quantified as the amount of coma flare, and the amount of eccentricity correction is determined based on this to fine-tune the lens system to be adjusted .

That is, the ratio of the approximate gradient of the illuminance distribution on both sides of the point of strongest illuminance is calculated as the amount of coma flare. The relationship between the amount of eccentricity of the lens system and the amount of coma flare is measured in advance to prepare reference data. Then, the coma flare amount of the lens system to be adjusted is compared with reference data to obtain a correction eccentricity amount, and the fine drive stage means is driven to finely move the lens system to be adjusted.

Since this is a simple calculation for analyzing two sets of linear chart images, the eccentricity correction amount is calculated at high speed and with high accuracy.
The optical axis of the lens system can be automatically adjusted. This greatly contributes to higher precision of an optical system such as a camera lens and a reduction in assembly cost.

Before performing fine adjustment using the amount of coma flare, the lens system to be adjusted is moved to a plurality of positions, and the maximum illuminance value at each position is stored in the storage means. By providing a coarse adjustment process for determining the reference position of the eccentric O, the time required for the entire adjustment work can be reduced, and the accuracy of the fine adjustment based on the coma flare amount can be greatly improved.

[0014]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a lens system optical axis adjusting apparatus according to an embodiment, which comprises a mount 1 for supporting a lens barrel K of a lens system F composed of lenses F _{1 to} F _4, and a mount 1 above the mount 1. It has a chart projection unit 2 and a UV irradiation unit 3 arranged. The chart projection unit 2 includes a light source 21
And a projection lens 22 and a chart 24 disposed thereunder.
The chart 24 can be moved in the optical axis direction of the illumination light generated from the light source 21 by driving the focus axis 25 by a motor (not shown), and the chart image can be focused as necessary. adjust.

The chart image projected by the chart projection unit 2 passes through a lens system F composed of lenses F _{1 to} F ₄ and a collimator lens 4 constituting a projection optical system together with a projection lens 22 to form an image on an imaging surface of a sensor 5. Is done.

Here, the lenses F _{2 to} F ₄ are fixed lens systems which are optical systems which have already been adjusted in optical axis and are fixed to the lens barrel K, and the lens system to be adjusted in which the lens F ₁ is adjusted in optical axis. This is not limited to one lens, and may be configured by a plurality of lenses. The lens F ₁ is pressed down on the lens barrel K by the finger 11,
And, so as to be movable by the XY fine movement stage 12 is finely driven stage means perpendicular XY direction to the optical axis (Z-axis) (two directions) (fine adjust), the edge of the lens F ₁ with an oblique angle It is grasped. Note that the barrel K is a gantry 1
Fixedly held.

A collimator lens 4 is provided below the lens system F.
Is provided, and a chart image is formed on the imaging surface of the sensor 5 provided further below. As the sensor 5, a sensor capable of photoelectric conversion such as a CCD camera or a line sensor camera is used.
The camera control unit 51 has a power supply, a clock, and the like for the sensor 5 and supplies a signal of a chart image converted in time series to the image processing device 6. The image processing device 6 has a calculation unit that calculates the amount of coma flare and the contrast value from the chart image converted into the time-series signal, as described later.

The UV irradiation unit 3, after the end of the optical axis adjustment, and at the same time chart projection unit 2 from the optical axis is retracted, moved right above the lens F _1, by applying an adhesive to the outer peripheral portion Irradiate UV light. Thus the adhesive is cured to fix the lens F ₁ to the barrel K.

The XY fine movement stage 12 drives the motors for the X fine movement axis and the Y fine movement axis in accordance with instructions from the control device 13 which is a control means to finely move the finger 11 in the XY directions. The control device 13 moves the XY fine movement stage 12 so as to eliminate the eccentric amount which is the cause of the coma flare amount calculated by the calculating means in the image processing device 6 as described later.

By repeating this process, the optical axis of the lens F ₁ is made to coincide with the optical axes of the lenses F _{2 to} F ₄ , and then the UV irradiation unit 3 is moved directly above the lens system F as described above. , application of the adhesive, performs adhesively fixed lens F ₁ by UV radiation.

However, if the amount of eccentricity of the lens F ₁ is, for example, 1
If it exceeds 00 microns, the sharpness of the chart image of the image processing device 6 becomes insufficient as described later, and a large error occurs in the calculated value of the coma flare amount. Therefore, XY
The fine movement stage 12 is step-moved at a predetermined pitch,
The illuminance distribution of the chart image is obtained for each position of each step movement, the maximum luminance, which is the maximum illuminance value, is detected and stored in a storage circuit, which is storage means in the control device 13, and based on the obtained data sequence. For example, a coarse adjustment described later is performed up to an eccentric amount of 100 microns or less.

FIG. 2 is a plan view showing a chart 24 of the apparatus of FIG. These are chart patterns P _x , P _x which are linear patterns in two directions projected brightly on the sensor 5.
_It has _y and the remaining part is a part that does not transmit light. Each of the chart patterns P _x and P _y includes a long first straight line portion for obtaining a coma flare amount and a plurality of short second straight line portions for obtaining a contrast value. The size of each chart pattern P _x , _Py depends on the optical performance of the lens system to be adjusted.
The width corresponding to the book length, that is, the short side is about 10 μm each, the long side is about 50 μm, and especially the long part is 1 μm.
It is about 50 microns.

The various parts of the apparatus are adjusted in advance so that the XY direction of the chart 24, the XY movement direction of the XY fine movement stage 12, and the XY direction of the sensor 5 substantially match.

FIG. 3 shows chart images P ₁ and P ₂ which are two sets of linear chart images formed on the sensor 5. These are taken into the image processing device 6 via the camera control unit 51, and the measurement points S ₁ , S ₃ of the chart image P ₁ are stored therein.
When the illuminance distribution in the Y direction at is calculated, FIG.
And the graph shown in FIG. Similarly, when the illuminance distribution in the X direction at the measurement points S ₂ and S ₄ of the chart image P ₂ is calculated, the graphs shown in FIG. 4B and FIG. 5B are obtained. The image flare amount and the contrast value described below are calculated from the illuminance distribution by the image processing device 6.
It is performed by the arithmetic means in the above.

From the illuminance distribution at the measurement point S _1, the amount of coma flare due to the optical axis shift (eccentricity) in the Y direction is calculated, and from the illuminance distribution at the measurement point S ₂ , the amount of coma flare due to the optical axis shift (eccentricity) in the X direction is calculated. Is calculated.

[0027] FIG. 6 is for explaining a method of calculating coma flare amount principle, to calculate the coma flare amount in the Y direction by the following procedure from the illuminance distribution at the measurement point S ₁ of FIG. First, a maximum luminance point A, which is the strongest illuminance point, is searched from the illuminance distribution. Next, a preset method,
For example, the maximum illuminance value × 0.9 is obtained, and this is set as the value of the slice level large. Next, for example, a maximum illuminance value × 0.2 is obtained, and this is set as a slice level small value.

Next, two large and small slice levels are shown.
Two straight lines B₁ , B_Two Intersection C between the illuminance distribution₁ , C_Two ,
C_Three , C_Four Find out. Lighting for convenience from the point of maximum brightness A
Divide the degree distribution into left and right sides,₁ , C_Two Tie
Straight line D₁ Is determined. Similarly, the right intersection C_Three , C_Four To
Straight line D connecting_Two Is determined. Next, the straight line D₁ And straight line D _Two 
And the slice level straight line B_Two The angle between₁ , Θ
_Two As a straight line D₁ , D_Two Gradient ratio (tanθ)₁ / T
anθ_Two ) And calculate this value Q_y Is the coma flare in the Y direction.
Take the numerical value of the quantity.

By performing the same processing as described above using the measurement point S ₂ , a numerical value representing the amount of coma flare Q _x in the X direction can be obtained.

The lens F of the lens system F₁ ~ F_Four The optical axis of
Coma flare amount Q_y , Q _x Is 1.0
You.

FIGS. 7A and 7B illustrate the relationship between the amount of eccentricity of the lens and the illuminance distribution. FIG. 30
Each illuminance distribution at the time of microns is shown. (A) of FIG.
Θ ₁ <θ ₂ , θ ₁ = θ ₂ in (b), θ in (c)
_1> theta _2, and the numerical value represents the coma flare amount Q = (ta
nθ ₁ / tan θ ₂ ) is Q <1.
0 and (b), Q = 1.0, and (c), Q> 1.0. If the relationship between the amount of eccentricity and the numerical value Q representing the amount of coma flare is examined and plotted in advance, the graph shown in FIG. 8 is obtained. The direction of optical axis adjustment is determined depending on whether the numerical value Q representing the amount of coma flare is larger or smaller than 1.0, and how close the value is to 1.0 is determined. Drive. By repeating this operation and judging the completion of the optical axis adjustment, the optical axis adjustment can be automatically performed.

After the optical axis adjustment is completed, the application of the adhesive by the UV irradiation unit 3 and the
Although a curing process is performed by V light, the lens F ₁
If the lens itself is defective with poor lens performance,
It is not preferable to fix the lens barrel K as it is. Therefore, the second measurement point S of each chart image P ₁ , P _2
3, in FIG. 5 obtained from S ₄ (a), it calculates a contrast value W by using the illuminance distribution shown in (b), thereby to evaluate the lens performance. That is, when the contrast value W is equal to or smaller than the predetermined level, the lens F ₁ is determined to be defective insufficient resolution, with an error signal is a lens defect signal to the display means (not shown), the lens F ₁
The process is completed without bonding and fixing.

In this way, by preventing the assembly of defective lenses, the quality control of the final product such as a camera can be made more efficient, and the productivity can be improved.

The contrast value W is calculated as follows.

As shown in FIG. 9, the maximum illuminance value a and the minimum illuminance value b of the illuminance distribution are obtained, and the contrast value W = 100.
X (ab) / (a + b) (percent) is calculated.

FIG. 11 shows measurement points S ₁ to S _{1 of the} chart image used for measuring the coma flare amount Q and the contrast value W.
It is a diagram showing how to set a S _4. FIG. 11A is a chart image formed on the sensor 5, and measurement points S ₂ and S are obtained from the illuminance distribution in the Y direction of FIG. 11B obtained by the image processing device 6 as follows. Determine ₄ . First take the sum of the X-direction of the illumination values of the chart image P _2, calculates the distribution of the Y-direction. The result is obtained as an illuminance distribution in the Y direction as shown in FIG.

Next, the slice level is set to a predetermined slice level.
Point y₀ Search for. y₀If you find it,
Chart image P determined_Two Distance h₁ , H_Two More measurement
Point y₁ = Y₀ + H₁ , Y_Two = Y₀ + H_Two Calculate
Then, the measurement point S_Two , S _Four To ask for each
it can. Measurement point S in X direction₁ , S_Three The same procedure
Can be obtained by

As described above, by setting each measurement point for each chart and always using the same portion of the chart as the measurement point, variations in the optical chart performance (sharpness of the edge, transmittance) due to the chart portion occurring at the time of chart production. It is possible to avoid degradation of measurement reproducibility due to factors such as the above.

Next, a rough adjustment process performed before the optical axis adjustment based on the coma flare amount will be described.

As described above, the eccentricity of the lens F ₁ is 10
At about 0 μm, the height of the peak of the chart image decreases as shown in FIGS. 12A and 12C, and the error of the tangent left / right ratio representing the amount of coma flare increases, and a correct value is detected. can not, therefore the optical axis adjustment of the lens F ₁ becomes difficult, when the eccentric further increased, the chart image itself is not detected.

FIG. 13 is a diagram showing the relationship between the range of coarse adjustment and the range of fine adjustment. In this case, the range within the circle having a diameter of 600 microns is provided as an adjustment margin, but the adjustment direction can be detected with high accuracy from the chart image by the sensor in a range of about ± 50 microns. Therefore, first, the lens F ₁ at 100 micron pitch as coarse moving step, to store the maximum luminance in the memory circuit by examining the presence or absence of the sensor output at each position, based defines the range of fine adjustment within 100 microns It is necessary to set the position.

FIGS. 14 and 15 are flowcharts showing the optical axis adjustment process according to one embodiment. First, in step 1, parameters used for calculation are initialized.
The mechanism is set to the initial position, and the lens system F,
Was set, the lens F ₁ is gripped against the barrel K downward in the finger 11 is positioned substantially at the center of the white adjusting lens F ₁ by moving the XY fine movement stage 12.

In step 2, the XY fine movement stage 12 is moved to position 1 in FIG. 13, and when the loop is repeated, position 2, position 3, position 4
... Position 24 and positioning are repeated. In step 001, the chart image is taken into the image processing device 6, and the maximum luminance in the image is stored in the storage circuit in pairs with the position number.

If it is determined in step 002 that the processing is completed up to the position 24 or the maximum luminance is larger than a predetermined value, the loop is terminated and
Proceed to 3. If not, return to step 2.

In step 003, the maximum luminance area is calculated.

That is, measuring up to position 24,
If the maximum luminance is detected at one position, that position is set as a fine adjustment range in the next step.

If there is a position where the maximum luminance is larger than the predetermined value before scanning to the position 24, the adjustment range can be determined from the measured value at that position. The range is fine adjustment in steps.

Further, for example, when the position of the eccentricity O is located at the position (a) in FIG. 13, when the position 24 is measured, the positions having the same maximum luminance are 14,1.
5, 22, and 21. In such a case, data strings having a large amount of sampling data, such as positions 13 to 18 and positions 2 to 23, are adopted in the X and Y directions, and these data strings are obtained by performing curve approximation with a polynomial. The part where the luminance on the approximate curve is maximum is X
Direction, the center of the fine adjustment range in the Y direction, that is, the reference position.

FIG. 16 illustrates the case where the reference position in the X direction is detected.
A graph A shown by a solid line plots the data sequence of the maximum luminance at the positions 15, 10, 10, and 2, and a curve B shown by a broken line as a polynomial approximation curve approximated by a sixth-order polynomial approximation. It is. The position indicating the maximum luminance of the curve B, that is, the approximate center between the positions 21 and 15 is detected as the center of the fine adjustment range, that is, the reference position in the X direction.

FIG. 17 shows a case where the reference position in the Y direction is detected when the position of the eccentricity O is (a). Similar to the X direction, a sixth-order approximate curve B is obtained from the graph A of the data string, and the center of the fine adjustment range is obtained.

When there is a point of eccentricity O at the location (b) in FIG. 13, as shown in FIG. 18, the data sequence in the X direction is position 23, position 21, position 15, position 10, position 4, Position 2. From this graph A data string obtaining 2-6-order polynomial trendline when Graph B ₁ .about.B ₄ is obtained. As can be seen from this figure, a correct reference position cannot be obtained unless a fourth-order or higher polynomial approximation is used. Therefore, it is desirable to use a fourth-order or higher, preferably a sixth-order polynomial approximation. X-axis in step 3 When thus determined reference position, to position the lens F ₁ by moving the Y-axis to the reference position.

In step 4, the value (tan θ ₁ / t) representing the amount of coma flare is obtained by the above-described procedure using the chart image.
an θ ₂ ) is calculated in the image processing device 6. The obtained value as Q _y.

[0053] In step 5, coma flare amount Q _y to compare whether within the tolerance. Since this allowable value is a value unique to the device, it is measured in advance. That is, after the optical axis is manually adjusted using a monitor or the like, the XY fine movement stage 12 is finely moved by a fixed amount in the X direction or the Y direction, and a value representing the amount of coma flare (tan θ ₁ / tan)
θ ₂ ) is detected, and the obtained value and the amount of stage movement are plotted to obtain a graph shown in FIG. The allowable value is determined from this graph. For example, if the width of the allowable value is ± 5 microns, the allowable value is approximately 0.80 <Q _y <1.30, and if the width of the allowable value is ± 2 microns, 0.9 <Q _y <1.1. It is decided.

In step 5, if Q _y is not within the allowable value, an eccentricity correction amount can be obtained from Q _y . That is,
Since Q _y = tan θ ₁ / tan θ ₂ , the eccentricity correction amount in the Y direction is k times (1−Q _y ).

K is a constant peculiar to the apparatus and can be determined from the graph of FIG. 8 measured in advance. That is, the slope when the graph of FIG. 8 is regarded as a straight line can be used as k. In step 6, k of (1-Q _y )
The Y axis of the XY fine movement stage 12 is finely moved by a factor of twice, and the process returns to step 4.

[0056] proceeds to step 7 if Q _y is within the allowable value in step 5, Step 8, using the chart image in step 9 to adjust the eccentricity of the X-direction in the same manner as described above.

When the adjustment is completed and the process proceeds to step 10, Y
The measurement of the coma flare amount in the direction is performed for confirmation. Usually, the adjustment in the X direction and the adjustment in the Y direction do not interfere with each other due to the nature of the lens, but the coma flare amount in the Y direction is measured for confirmation. Lens F ₁ of a manufacturing error, unless coma flare amount caused by the Y-direction, such as built-in error within the allowable value, perform readjustment returns to Step 4. If the amount of the coma flare in the Y direction is within the allowable value in step 11, the X, Y
The direction contrast value W is measured. That is, the contrast value W is calculated from the last chart image input to the image processing device 6 in step 10 by the above-described method. After the contrast value W is calculated, it is checked in step 131 whether a predetermined process standard (for example, both X and Y have a contrast value of 70% or more) is satisfied. Display and exit. If the process standard is satisfied, the chart projection unit 2 is evacuated from the optical axis in step 12, and
In the UV irradiation unit 3 moves on the optical axis, application of the adhesive, the lens F ₁ performs irradiation of UV light is adhesively fixed.

In the flowchart, three repetition loops are represented as infinite loops.
The use of a software counter for limiting the number of loops which is usually performed is not particularly described, but it goes without saying that it is used.

According to the present embodiment, the amount of coma flare in the X and Y directions is detected from the illuminance distribution of each of the two sets of linear chart images, and the eccentricity of the lens (lens system) is automatically eliminated and fixed by bonding. Can be performed. To detect the amount of coma flare, two slice levels are provided for the illuminance distribution of the chart image, the intersection is obtained by comparing the magnitudes of the discrete data, two straight lines on the left and right are provided centering on the maximum luminance point, and the tangent ratio is calculated. It has a remarkable advantage that the amount of coma flare can be quantitatively measured in a short time and the measurement error is small.

In addition, by evaluating the lens performance by obtaining the contrast value of the chart image after the optical axis adjustment is completed, it is possible to prevent the assembly of a lens having poor performance due to lack of resolution due to causes other than eccentricity. .

As shown in FIG. 10, when the chart resolution used for calculating the coma flare amount and the contrast value can be shared as shown in FIG. The amount of coma flare may be detected using the chart pattern used in the above.

The apparatus shown in FIG.
Is used to make the apparatus compact and to set the chart position at the focal length position of the lens system F. If this condition can be ignored, the collimator lens 4 may be omitted.

Further, depending on the characteristics of the lens system, the intersection may be obtained by using a polynomial approximation such as a spline approximation to calculate the coma flare amount.

These may be selected optimally according to the nature of the coma flare of the lens system, the calculation time, the production tact, and the required accuracy.

When the maximum luminance is detected in the coarse adjustment step of setting the reference position in the X direction and the Y direction, if an industrial camera is used, the chart image normally obtained is information of 512 pixels × 512 pixels. However, the chart image is determined by the magnification of the optical system. In the present embodiment, the lateral magnification is about 10, the width of the chart is 10 microns × 10 = 100 microns, and the camera sensor pitch is about 15 microns. Then, it is projected to a width of about 7 pixels. The longitudinal direction of the chart is projected on more pixels.

Therefore, when obtaining the maximum luminance in an image,
It is not necessary to compare all 515 × 512 pixels, 256 × 256 pixels every other pixel, or 1 every 2 pixels.
The maximum illuminance value may be obtained from 28 × 128 pixels. By doing so, the calculation time can be reduced to 1/4 and 1/16.

If there is no problem even at every other pixel, it is not necessary to take in one frame of the image at the stage of inputting the image to the image processing device 6, and if only one field signal is taken in, every other pixel in the vertical synchronization direction. Signals can be captured. By doing so, the image capturing time due to the camera scanning time can be reduced from 30 milliseconds per frame to 15 milliseconds per field.

Note that a line sensor camera may be used instead of the area sensor.

Before detecting and fine-tuning the amount of coma flare from the illuminance distribution of each of two sets of orthogonal chart images,
By performing coarse adjustment in advance using the maximum illuminance value, that is, maximum luminance within a large adjustment margin, and using a polynomial approximation of the fourth order or more, a lens system having a large eccentricity adjustment range that cannot be detected only by measuring the amount of coma flare is used. The optical axis eccentricity adjustment can be performed accurately and efficiently in a short time.

Accordingly, it is possible to use a lens having a high sensitivity to coma flare against eccentricity, for example, a double-sided aspherical lens, without increasing the precision of processing a single lens, thereby realizing a more compact and high-performance lens system. .

By comparing the maximum luminance every other pixel or every constant pitch such as every two pixels,
The processing time can be greatly reduced, and the optical axis eccentricity adjustment with high working efficiency and good productivity can be performed. Further, by taking in the field signal, the measurement time can be shortened and the working efficiency can be further improved.

[0072]

Since the present invention is configured as described above, it has the following effects.

The eccentric state of the lens system (lens) is detected with high speed and high accuracy, the optical axis of the lens system is automatically adjusted, and the adjusted lens can be adhered and fixed as it is. Use of such a lens system optical axis adjustment device can greatly contribute to improving the assembly accuracy of optical elements such as camera lenses and reducing assembly costs.

In addition, the lens performance is checked after the completion of the optical axis adjustment to prevent a lens having a poor performance from being erroneously assembled, thereby improving the quality control of the optical product and improving the productivity. it can.

Prior to the fine adjustment step based on the amount of coma flare, the lens system to be adjusted is step-moved to detect the maximum luminance at each position, and the coarse adjustment for defining the fine adjustment range from the obtained data is performed. Fine adjustment by the amount of coma flare can be realized even with a lens having a large size. This makes it possible to adjust the optical axes of various lenses efficiently and with high accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a lens system optical axis adjusting device according to an embodiment.

FIG. 2 is a plan view showing only a chart of the apparatus of FIG. 1;

FIG. 3 is a diagram showing a chart image formed on a sensor.

FIG. 4 is a graph showing an illuminance distribution at measurement points S ₁ and S ₂ of the chart image of FIG. 3.

FIG. 5 is a graph showing illuminance distributions at measurement points S ₃ and S ₄ .

FIG. 6 is a diagram illustrating a method of calculating a coma flare amount from an illuminance distribution of a chart image.

FIG. 7 is a graph showing the relationship between the amount of eccentricity and the illuminance distribution.

FIG. 8 is a graph showing reference data obtained by examining the relationship between the amount of eccentricity and the amount of coma flare.

FIG. 9 is a diagram illustrating a method of calculating a contrast value.

FIG. 10 is a diagram illustrating a method of calculating a coma flare amount using a chart image for detecting a contrast value.

FIG. 11 is a diagram illustrating a method for setting a measurement point.

FIG. 12 is a diagram illustrating the relationship between the amount of eccentricity of the lens and the waveform of the illuminance distribution.

FIG. 13 is a diagram illustrating a coarse adjustment position.

FIG. 14 is a flowchart showing a part of a process of optical axis adjustment.

FIG. 15 is a flowchart showing the rest of the optical axis adjustment process.

FIG. 16 is a diagram showing a data string in the X direction and an approximate curve at a position (a) in FIG. 13;

17 is a diagram showing a data sequence in the Y direction and an approximate curve at a position (a) in FIG.

18 is a diagram showing a data string and an approximate curve in the X direction at the position (b) in FIG.

FIG. 19 is a schematic view showing a conventional example.

[Explanation of symbols]

 Reference Signs List 1 base 2 chart projection unit 3 UV irradiation unit 4 collimator lens 5 sensor 6 image processing device 11 finger 12 XY fine movement stage 13 control device 21 light source 24 chart 25 focus axis 51 camera control unit

Claims (6)

[Claims] 1. A fine drive stage means for finely moving a lens system to be adjusted two-dimensionally perpendicular to an optical axis of an optical system, a chart having a linear pattern in two directions perpendicular to the optical axis, and the chart And a projection optical system for projecting the linear pattern in the two directions to the sensor through the lens system to be adjusted to obtain two sets of linear chart images, and detecting the illuminance distribution of the two sets of linear chart images in the two directions, respectively. Calculating means for calculating a coma flare amount centered on the point of strongest illuminance from each illuminance distribution; control means for controlling the fine drive stage means based on an eccentricity correction amount obtained from the coma flare amount; A lens system optical axis adjustment device having a storage unit for moving an adjustment lens system and storing a maximum illuminance value of the two sets of linear chart images at each of a plurality of positions. 2. A step of holding a lens system to be adjusted in an optical path of an optical system, and arranging a chart having a linear pattern in two directions on the optical path, and forming the linear pattern in the two directions via the lens system to be adjusted. Projecting onto a sensor, detecting the illuminance distributions of the two sets of projected linear chart images in the two directions, and calculating the amount of coma flare centered on the point of strongest illuminance, and obtaining from the calculated amount of coma flare. A step of finely adjusting the adjusted lens system based on the eccentricity correction amount, detecting the maximum illuminance value of each linear chart image at each of a plurality of positions by moving the adjusted lens system, A method of adjusting the optical axis of the lens system, wherein a step of performing a coarse adjustment for determining a reference position based on the obtained data string is added. 3. A method for adjusting the optical axis of a lens system according to claim 2, wherein a coarse adjustment for determining a reference position is performed by approximating a curve of the obtained data string. 4. A lens system optical axis adjusting method according to claim 3, wherein a coarse adjustment for determining a reference position is performed by approximating the obtained data sequence with a polynomial approximation curve of fourth order or higher. 5. The method according to claim 2, wherein a maximum illuminance value is detected using pixels at each constant pitch. 6. The optical axis of a lens system according to claim 2, wherein a coarse adjustment is performed using a field signal of the image, and a coma flare amount is calculated using a frame signal of the image. Adjustment method.