JP3766835B2 - Lens system adjusting device and lens system adjusting method using the same - Google Patents

Description

The present invention relates to a lens system adjustment device and lens system adjustment how using the same for optical axis adjustment of the lens system comprising a plurality of lenses.

  In recent years, due to the miniaturization of lens elements due to higher functionality of compact digital cameras and mobile phone cameras and the increased use of aspherical surfaces, the required accuracy of camera lenses for the above digital cameras and mobile phone cameras has become stricter year by year. In addition to improving the processing accuracy of a single lens, it is essential to adjust the optical axis of a lens system composed of a plurality of lenses. At the same time as adjusting the optical axis of the lens system, the imaging performance of the adjusted lens system is measured using MTF (spatial frequency characteristics), which is generally used as an index representing the resolving power of the optical lens. It is necessary to check the result of the adjustment and determine whether or not it is acceptable.

  As a conventional MTF measuring apparatus, there is one as disclosed in Japanese Patent Application Laid-Open No. 61-84541 (Patent Document 1). Further, as a conventional optical axis adjusting device, there is one as disclosed in JP-A-6-265766 (Patent Document 2).

  Here, the MTF apparatus measurement will be described with reference to FIGS. The MTF is a quantity that comprehensively represents the performance of an imaging system such as a lens. This is the ratio of the amplitude of the image by the lens to the amplitude on the object side when a spatial sine wave is input to the lens. expressed. The actual measurement in the MTF is performed by detecting a light intensity distribution such as a point image, a line image, and an edge image with a lens to be examined and performing a Fourier transform process. In FIG. 13, for example, a slit 2 is placed on the optical axis and outside the optical axis of the lens 1 to be tested at a position corresponding to the film surface of the camera, and the slit 2 is irradiated with a light source 3 to correspond to the object plane. A slit image is formed on the screen. Then, the slit image is picked up by an image pickup device 4 such as a CCD (charge coupled device) and scanned in a direction perpendicular to the longitudinal direction of the slit image to obtain an intensity distribution as shown in FIG. Then, noise is removed by the signal processing circuit 5 and Fourier transform is performed by the FFT operation circuit 6 to obtain the MTF value for each angle of view as shown in FIG. 15, and the result is displayed on the display unit 7. .

  Next, a conventional lens system optical axis adjusting device will be described with reference to FIG. The conventional lens system optical axis adjusting apparatus shown in FIG. 16 fixes the first lens system 11 by arranging the first lens system 11 and the second lens system 12 so that their optical axes are in the vertical direction. After that, the second lens system 12 is finely moved so that the optical axis of the first lens system 11 coincides with the optical axis of the second lens system 12.

  The lens system optical axis adjusting device includes an irradiating unit 13 that irradiates the first lens system 11 and the second lens system 12 with a central ray and three or more annular rays parallel to the central ray, and an illuminance generating unit. 14, fine alignment correction amount generation means 15, and second lens fine movement means 16. The illuminance generation means 14 receives the central ray and the annular ray that have passed through the first lens system 11 and the second lens system 12, and corresponds to images formed by the central ray and the annular ray, respectively. To generate a signal. At the same time, the illuminance of each image is obtained based on the signal. Further, the fine alignment correction amount generation means 15 obtains the barycentric coordinates of the zonal ray image and the center coordinates of the central ray image from the illuminance distribution of each image obtained by the illuminance generation means 14, and the difference between the two coordinates. The fine alignment correction amount is obtained according to the on-axis coma amount obtained from (1). The second lens fine movement means 16 finely moves the second lens system 12 based on the fine alignment correction amount obtained by the fine alignment correction amount generation means 15.

  In the above configuration, when the optical axes of the first lens system 11 and the second lens system 12 do not coincide with each other, the parallel central light beam and three or more annular light beams are the first lens system 11 and By passing through the second lens system 12, a shift occurs between the center position through which the central light beam passes and the center of gravity position of the annular light beam. Therefore, the illuminance of each image formed by the central ray and the annular ray on the light receiving surface of the light receiving element 17 in the illuminance generation means 14 is obtained, and obtained from the illuminance distribution of each image by the fine alignment correction amount generation means 15. The difference between the center position and the center of gravity position is quantitatively measured by calculating the difference between the center coordinates of the center ray and the center of gravity coordinates of the annular light beam as the amount of on-axis frame. Then, the second lens system 12 is repeatedly finely moved by the second lens fine movement unit 16 based on the fine alignment correction amount obtained by the fine alignment correction amount generation unit 15 according to the on-axis coma amount. The optical axis of the system 11 and the optical axis of the second lens system 12 are automatically matched.

  However, the conventional MTF measuring apparatus described in Patent Document 1 has the following problems. That is, by arranging the light source 3, the slit 2, and the image sensor 4 for each of a plurality of angles of view, it is possible to calculate MTF values corresponding to the angles of view at a time. However, in that case, there is a problem that the number of components increases. Furthermore, there is a limit to the actual arrangement of the light source 3 and the slit 2, and there is also a problem that MTF evaluation for a large number of angles of view cannot be easily performed.

  Further, the conventional lens system optical axis adjusting device described in Patent Document 2 has the following problems. That is, in the lens system optical axis adjusting device, when the optical axis of the lens system is adjusted, it is confirmed whether or not the optical axes of the first lens system 11 and the second lens system 12 are correctly aligned. There is no art. Therefore, in the case of the conventional lens system optical axis adjustment device, after the optical axis adjustment of the lens system (optical axis adjustment step), the test lens is further replaced with the MTF measurement device to measure the MTF value. Therefore, it is necessary to confirm an adjustment defect in the optical axis adjustment process (inspection process), and simplification of the optical axis adjustment process and the inspection process is desired.

In the conventional lens system optical axis adjustment device, the optical axis of the lens system can be adjusted, but the adjustment is performed using the light receiving element 17 for adjustment. Therefore, for example, in the lens system adjustment of a camera lens in which an image pickup element such as a digital camera and a lens system are integrated, after performing the optical axis adjustment of the lens system, an image pickup element that is actually used It is necessary to adjust the position with the lens system, and simplification is also desired in this respect. Even if an image pickup device that is actually fixed as a module is disposed on the image plane 18 and the lens system is adjusted using the image pickup device later, a plurality of parallel lights can be adjusted at the same incident angle. Therefore, the focused spot is narrowed down to approximately one point on the image plane 18. Therefore, as it is, the optical axis of the lens system cannot be adjusted using the image pickup device arranged on the image plane 18, and there is a problem that another lens for guiding light to the image pickup device for the module is required. is there.
JP 61-84541 A JP-A-6-265766

Accordingly, an object of the present invention is to continuously perform optical axis adjustment of the lens system and MTF measurement, and to accurately adjust the optical axis of the lens by the light beam corresponding to each angle of view. system and to provide a lens system adjustment device and lens system adjustment how using the same and a position adjustment of the optical axis adjustment and the image pickup element of the lens system can be carried out continuously in a camera lens or the like are integral There is.

In order to solve the above problems, the lens system adjusting device of the present invention is:
A laser emitting section for generating parallel light rays serving as a reference axis;
A to-be-adjusted object including a lens system composed of a plurality of lenses and an image sensor;
It is disposed between the laser light emitting unit and the object to be adjusted, and deflects a part of the parallel light beam from the laser light emitting unit so that the angle with the reference axis is an angle corresponding to the angle of view of the lens system. A plurality of diffractive elements that generate a certain parallel beam bundle and enter the lens system, and pass a part of the parallel beam from the laser light emitting unit located at the center portion to obtain a reference beam bundle as the reference axis A substrate formed with an opening to be generated and incident on the lens system;
A moving unit for moving at least one of the lens system and the image sensor;
Based on the output of the image sensor, movement of the lens system or image sensor for positioning the image of the reference beam and the image of the deflected beam at a predetermined position on the light receiving surface of the image sensor And a calculation control processing unit that controls the operation of the moving unit based on the calculated moving amount.

  According to the above configuration, the operation of the moving unit is controlled by the arithmetic control processing unit, and the lens system is arranged so that the image of the reference beam bundle is positioned at the center position on the light receiving surface of the image sensor, for example. By moving, it is possible to adjust the eccentricity or tilt of the plurality of lenses constituting the lens system. Further, for example, by moving the lens system so that the image of the light beam deflected by the diffraction elements arranged in a point object with respect to the center of the substrate is point-symmetric with respect to the center of the light receiving surface, The optical axis of the lens system can be adjusted with high accuracy by light rays corresponding to a plurality of angles of view.

Moreover, in the lens system adjusting apparatus of one embodiment,
An optical branching element disposed between the substrate and the object to be adjusted on the reference axis;
An aperture disposed between the optical branching element and the object to be adjusted on the reference axis;
The light is emitted from the light source unit, passes through the opening of the substrate, the light branching element, and the aperture, is reflected by the reference surface of the imaging element, passes through the aperture again, and is orthogonal to the reference axis by the light branching element. A light detector for detecting the light reflected in the direction in which the light is reflected.

  According to this embodiment, the operation control unit controls the operation of the moving unit so that, for example, the light detected by the photodetector is positioned at the center of the light receiving surface of the photodetector. By moving the image sensor, prior to the optical axis adjustment of the lens system, the angle and position between the reference axis and the reference surface of the object to be adjusted can be adjusted to be optimal.

Moreover, in the lens system adjusting apparatus of one embodiment,
The diameter of the parallel light beam that is deflected by the diffraction element of the substrate and is incident on the lens system, and the diameter of the reference light beam that is incident on the lens system through the opening of the substrate are the lens It is set larger than the diameter of the entrance pupil of the system.

  According to this embodiment, it is possible to relax the adjustment accuracy when the entrance pupil center of the lens system is matched with the reference axis.

Moreover, in the lens system adjusting apparatus of one embodiment,
The moving unit is configured to move the lens system and the image sensor,
A first holding unit that fixes and holds a first lens element that forms part of the lens system with respect to the reference axis;
A second holding unit for holding a second lens element constituting the remainder of the lens system;
The moving unit that moves the lens system is configured, and a lens element moving mechanism that moves at least one of the first holding unit and the second holding unit is provided.

  According to this embodiment, the first lens element and the second lens element constituting the lens system can be individually moved by the lens element moving mechanism under the control of the arithmetic control processing unit. Therefore, the decentering or tilt of the lens system can be precisely adjusted by dividing it into the first and second lens elements.

Moreover, in the lens system adjusting apparatus of one embodiment,
The substrate is provided with a chart for MTF measurement,
Illuminating means for uniformly illuminating the chart from the laser light source unit side,
The arithmetic control processing unit is configured to calculate the MTF value of the lens system based on the output of the imaging device relating to the chart.

  According to this embodiment, after the adjustment of the eccentricity or tilt of the lens system and the optical axis adjustment of the lens system are completed, the MTF that is an index of the resolving power of the lens system can be measured. Therefore, when the difference between the obtained MTF value and the design value (target value) is large, the optical axis of the lens system can be adjusted again, thereby reducing the incidence of defective products. Can do.

Moreover, in the lens system adjusting apparatus of one embodiment,
Based on the output of the image sensor, the peak value of the light intensity of the spot formed by collimating the parallel light beam emitted from the laser light source unit on the light receiving surface of the image sensor by the lens system is determined. A light amount adjusting means for adjusting the light amount of the laser light source unit according to the peak value is provided.

  According to this embodiment, since the light amount of the laser light source unit is adjusted according to the peak value of the light intensity on the light receiving surface of the image sensor, even if it is a condensing spot where the energy density becomes high The light quantity can be adjusted so that smear does not occur in the image sensor during the optical axis adjustment.

The present invention is also a lens system adjustment method using the lens system adjustment device,
A step of controlling the operation of the moving unit by the arithmetic control processing unit to move the image sensor so that the image of the reference beam passing through the opening of the substrate is positioned at the center of the light receiving surface of the image sensor. When,
Holding the first lens element fixed with respect to the reference axis by the first holding unit, and holding the second lens element by the second holding unit;
The operation of the lens element moving mechanism is controlled by the arithmetic control processing unit, and the light collection spot by the first lens element and the second lens element of the reference beam bundle that has passed through the opening of the substrate is received by the image sensor. Moving at least one of the first holding unit and the second holding unit so as to be located at the center of the surface;
The operation of the lens element moving mechanism is controlled by the arithmetic control processing unit, and the condensed spot by the first lens element and the second lens element of the light bundle deflected through the diffraction element of the substrate is Moving at least one of the first holding unit and the second holding unit so as to be arranged at a predetermined position on the light receiving surface of the imaging element;
And a step of fixing the lens system and the image sensor with respect to the reference axis.

  According to the above configuration, the operation of the moving unit is controlled by the arithmetic control processing unit, and the image sensor is moved so that the image of the reference beam bundle is positioned at the center of the light receiving surface of the image sensor. The relative position between the reference axis and the reference surface of the object to be adjusted can be adjusted to be optimum. Further, the operation of the lens element moving mechanism is controlled by the arithmetic control processing unit so that the condensing spot of the reference beam bundle by the first lens element and the second lens element is at the center of the light receiving surface of the image sensor. Since at least one of the first holding unit and the second holding unit is moved so as to be positioned, the eccentricity or tilt of the plurality of lens elements constituting the lens system can be adjusted by a simple method. Further, the operation of the lens element moving mechanism is controlled by the arithmetic control processing unit, so that the condensed spot of the deflected beam bundle by the first lens element and the second lens element is on the light receiving surface of the image sensor. Since at least one of the first holding unit and the second holding unit is moved so as to be arranged at a predetermined position, the optical axis of the lens system is accurately adjusted by light rays corresponding to a plurality of angles of view. be able to.

The present invention is also a lens system adjustment method using the lens system adjustment device,
A step of controlling the operation of the moving unit by the arithmetic control processing unit to move the image sensor so that the image of the reference beam passing through the opening of the substrate is positioned at the center of the light receiving surface of the image sensor. When,
Holding the first lens element fixed with respect to the reference axis by the first holding unit, and holding the second lens element by the second holding unit;
The operation of the lens element moving mechanism is controlled by the arithmetic control processing unit, and the light collection spot by the first lens element and the second lens element of the reference beam bundle that has passed through the opening of the substrate is received by the image sensor. Moving at least one of the first holding unit and the second holding unit so as to be located at the center of the surface;
The operation of the lens element moving mechanism is controlled by the arithmetic control processing unit, and the condensed spot by the first lens element and the second lens element of the light bundle deflected through the diffraction element of the substrate is Moving at least one of the first holding unit and the second holding unit so as to be arranged at a predetermined position on the light receiving surface of the imaging element;
The operation of the lens element moving mechanism is controlled by the arithmetic control processing unit, and an image of light from the illuminating means that has passed through the MTF measurement chart of the substrate is formed on the light receiving surface of the imaging element. And moving the first holding unit and the second holding unit,
A step of calculating an MTF value by the arithmetic control processing unit based on an output of the imaging element related to the image of the chart;
A step of fixing the lens system and the imaging device with respect to the reference axis when the difference between the calculated MTF value of the lens system and the target MTF value is within a predetermined range. It is characterized by.

  According to the above configuration, the operation of the moving unit is controlled by the arithmetic control processing unit, and the image sensor is moved so that the image of the reference beam bundle is positioned at the center of the light receiving surface of the image sensor. The relative position between the reference axis and the reference surface of the object to be adjusted can be adjusted to be optimum. Further, the operation of the lens element moving mechanism is controlled by the arithmetic control processing unit so that the condensing spot of the reference beam bundle by the first lens element and the second lens element is at the center of the light receiving surface of the image sensor. Since at least one of the first holding unit and the second holding unit is moved so as to be positioned, the eccentricity or tilt of the plurality of lens elements constituting the lens system can be adjusted by a simple method. Further, the operation of the lens element moving mechanism is controlled by the arithmetic control processing unit, so that the condensed spot of the deflected beam bundle by the first lens element and the second lens element is on the light receiving surface of the image sensor. Since at least one of the first holding unit and the second holding unit is moved so as to be arranged at a predetermined position, the optical axis of the lens system is accurately adjusted by light rays corresponding to a plurality of angles of view. be able to.

In addition, the MTF value of the lens system is calculated by the arithmetic control processing unit, and when the difference between the calculated MTF value and the target MTF value is within a predetermined range, the lens system and the image sensor are Since the lens system is fixed with respect to the reference axis, the MTF, which is an index of resolving power of the lens system, can be continuously measured after the adjustment of the eccentricity or tilt of the lens system and the optical axis adjustment of the lens system are completed. Therefore, the optical axis / position adjustment process of the lens system and the image sensor, the optical axis adjustment process of the lens system, and the inspection process of the lens system can be integrated. Furthermore, when the difference between the obtained MTF value and the design value (target value) is large, the optical axis of the lens system can be adjusted again, thereby reducing the incidence of defective products. Ru Nodea that can.

  As can be seen from the above, according to the present invention, the operation of the moving unit is controlled by the arithmetic control processing unit so that the image of the reference beam bundle is positioned at a predetermined position on the light receiving surface of the image sensor. Therefore, for example, by positioning the image of the reference beam at the center position on the light receiving surface, the eccentricity or tilt of the plurality of lenses constituting the lens system can be adjusted.

  Further, the operation of the moving unit is controlled by the arithmetic control processing unit, and the lens system is arranged so that the image of the light beam deflected by the diffraction element of the substrate is positioned at a predetermined position on the light receiving surface of the imaging element. For example, by arranging the image of the light bundle deflected by the diffraction element arranged in a point object with respect to the center of the substrate so as to be point-symmetric with respect to the center of the light receiving surface, The optical axis of the lens system can be adjusted with high accuracy by the light beam corresponding to the angle of view.

  According to one embodiment, after the adjustment of the eccentricity or tilt of the lens system and the adjustment of the optical axis of the lens system are finished, the calculation control processing unit continuously provides an index of the resolving power of the lens system. Since the MTF is measured, the optical axis / position adjustment process of the lens system and the image sensor, the optical axis adjustment process of the lens system, and the inspection process of the lens system can be integrated. Furthermore, when the value of the difference between the obtained MTF value and the design value (target value) is large, the optical axis of the lens system can be adjusted again, and the incidence of defective products can be reduced. .

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 is a schematic configuration diagram of the lens system adjusting apparatus according to the present embodiment.

  This lens system adjusting device is roughly configured by a light source 21, a lens system 22, a substrate 24, an image sensor 25, a holding unit 26, a first moving mechanism 27, and an arithmetic control processing unit 28. The light source 21 has a laser element and generates parallel light rays serving as a reference axis A. The lens system 22 includes a plurality of lenses and is an adjustment target. The substrate 24 is disposed between the light source 21 and the lens system 22, and also has a plurality of diffraction elements 23 that allow the parallel light obtained by deflecting some of the parallel rays generated by the light source 21 to enter the lens system 22. Is provided. The holding unit 26 is disposed after the lens system 22 on the reference axis A, and holds the image sensor 25 that is a CCD or the like that receives light from the light source 21. The imaging element 25 is integrated with the lens system 22 after adjustment to constitute a camera lens such as a digital camera. The first moving mechanism 27 moves the image sensor 25 together with the holding unit 26. The arithmetic control processing unit 28 calculates an optical evaluation value of the lens system 22 based on the output of the image sensor 25. Further, a control amount for controlling the movement of the image sensor 25 is calculated, and a control signal based on the control amount is generated and output to the first moving mechanism 27.

  FIG. 2 is a plan view of the substrate 24. As shown in FIG. 2, the diffractive element 23 is formed on the substrate 24 so as to be point-symmetric at a position corresponding to the angle of view of the lens system 22, for example, in a ring shape. Further, an opening 29 is formed in the central portion of the diffraction element 23 arranged in a circle to allow the light from the light source 21 to pass therethrough and generate a parallel light beam serving as a reference axis A (hereinafter referred to as a reference light beam). . The diffractive elements 23 are arranged so that the angle of the diffracted light with the reference axis A is an angle corresponding to the angle of view of the lens system 22. Further, the arrangement is taken into consideration so that unnecessary diffracted light does not enter the lens system 22.

  Note that the size of the aperture 29 for generating the reference light beam serving as the reference axis A and the size of the diffraction element 23 arranged corresponding to the angle of view of the lens system 22 are incident on the entrance pupil of the lens system 22. The diameter of each parallel light is set to be larger than the entrance pupil of the lens system 22. As a result, it is possible to relax the adjustment accuracy when the center of the entrance pupil of the lens system 22 and the reference axis of the lens system adjusting device are matched.

  Further, a slit 30 for MTF measurement is provided at a position corresponding to the angle of view for inspecting the MTF on the substrate 24. The slit 30 may have any shape as long as it can generally measure the MTF value, such as a point image, a line image, and an edge image. In the case of the present embodiment, since it is premised on the measurement of the MTF value in the tangential direction and in the radial direction, a cross line composed of two straight lines parallel to both the directions is used. The tangential direction and radial direction are as shown in FIG.

  The MTF measurement slit 30 is illuminated from the light source 21 side that generates parallel rays by, for example, an illumination device (not shown) such as a white LED (light emitting diode) or a halogen lamp. In that case, the said illuminating device is set so that the intensity | strength of the light which permeate | transmits each slit 30 may become uniform. Further, the region of the substrate 24 excluding the diffraction element 23, the opening 29 and the slit 30 is subjected to a masking process so that the parallel light from the light source 21 is not transmitted so that unnecessary light does not enter the lens system 22. It is configured.

  Further, as shown in FIG. 3, in order to make a right angle between the reference axis A and the reference plane of the lens system 22, the light branch element 31 and the aperture 32 arranged on the reference axis A and the light source 21 irradiate the light. And a photodetector 33 for detecting the reference surface of the lens system 22 and the reflected light reflected by the light branching element 31. Further, as shown in FIG. 1, a first holding unit 34 that holds a part of lens elements (hereinafter referred to as first lens elements) 39 constituting the lens system 22 fixedly with respect to a reference axis A, A second holding unit 35 that holds the remaining lens elements (hereinafter referred to as second lens elements) 40 of the lens system 22 and a second moving mechanism 36 that moves the second holding unit 35 are provided. The arithmetic control processing unit 28 calculates a control amount for controlling the movement of the second holding unit 35, generates a control signal based on the control amount, and outputs the control signal to the second moving mechanism 36. Yes.

  Further, depending on the design of the lens system 22, a mechanical shutter (hereinafter referred to as a mechanical shutter) 37 is disposed, or a filter 38 such as an IR (infrared) cut filter or a low-pass filter is disposed on the image sensor 25. There is a need to.

  3 to 6 show an optical axis adjustment procedure by the lens system adjustment apparatus. 7 to 9 show a condensing spot and a cross-shaped slit image formed on the image sensor 25. FIG. 10 to 12 show an MTF calculation method by this lens system adjusting apparatus. Hereinafter, the optical axis adjustment method and the MTF measurement method using this lens system adjustment apparatus will be described in detail with reference to FIGS.

  3 to 6 show a position adjustment procedure between the lens system 22 and the image sensor 25 using the lens system adjustment device, and an optical axis adjustment procedure of the lens system 22.

  In FIG. 3, first, adjustment is performed so that the reference axis A and the image sensor 25 are orthogonal to each other and the reference axis A and the center of the image sensor 25 are matched.

  Specifically, a part of the reference light beam (hereinafter referred to as the light beam 21) emitted from the light source 21 and passed through a half mirror as the light branching element 31 and the opening 29 disposed at the center of the substrate 24 on which the diffraction element 23 is formed. A center axis ray) passes through the aperture 32 and reaches the image sensor 25, is reflected by a cover glass (not shown) of the image sensor 25, passes through the aperture 32 again, and is reflected by the half mirror 31 with the reference axis A The tilt angle θ with respect to the Y axis of the image sensor 25 and the tilt angle with respect to the X axis are detected by the first moving mechanism 27 so as to be reflected in a direction orthogonal to the optical axis and detected by the image sensor as the optical axis adjusting photodetector 33 Adjust φ. In this case, although not shown in the figure, the output from the image sensor 33 is input to the arithmetic control processing unit 28, and the arithmetic control processing unit 28 outputs the central axis ray from the center of the image sensor 33. The amount of deviation in the Z-axis direction and the amount of deviation in the Y-axis direction are obtained, and the tilt angle θ with respect to the Y-axis is calculated based on the amount of deviation in the Z-axis direction, while the amount of deviation in the Y-axis direction is calculated. Based on this, the tilt angle φ with respect to the X axis is calculated. Then, a control signal based on the calculated tilt angles θ and φ is generated and output to the first moving mechanism 27.

  Next, based on the signal from the image sensor 25, the arithmetic control processing unit 28 obtains the amount of deviation of the central axis ray as the reference axis A from the center of the image sensor 25 in the XY axis direction. A movement amount in the XY-axis direction is calculated based on the deviation amount. Further, a control signal based on the calculated movement amount is generated and output to the first movement mechanism 27. Then, the image sensor 25 is moved in the X and Y directions by the first moving mechanism 27, and the position of the image sensor 25 is adjusted so that the reference axis A and the center of the light receiving surface of the image sensor 25 coincide. In this way, the angle and position between the reference plane of the lens system 22 (the surface of the image sensor 25) and the reference axis (reference axis A) of the lens system adjusting device are adjusted in advance. When a parallel plate composed of a filter 38 such as an IR cut filter or a low-pass filter is attached to the surface of the image pickup device 25, the angle of the image pickup device 25 or the like is reflected using the reflected light from the surface of the parallel plate. The position may be adjusted.

  Next, as shown in FIG. 4, the first lens element 39 constituting the lens system 22 is fixed by the first holding unit 34 while maintaining the state of the image sensor 25 after adjustment. Then, the first moving mechanism 27 shifts the imaging element 25 in the + Z direction or the −Z direction so that the central axis light beam that has passed through the opening 29 and the aperture 32 of the substrate 24 is condensed on the imaging element 25. . In this case, the calculation control processing unit 28 calculates the illuminance of the image of the central axis ray based on the signal from the image sensor 25, and calculates the above while moving the image sensor 25 in the + Z direction or the -Z direction by a predetermined length. Find the position where the illuminance is maximum. Alternatively, a position where the spot diameter of the image of the central axis ray is minimized may be found.

  When the fixed first lens element 39 has lens eccentricity or tilt, the central axis light beam incident on the first lens element 39 is condensed at a position slightly shifted from the center of the image sensor 25. Will be. In that case, from the viewpoint of imaging performance, it is important that the central axis light beam is incident on the image sensor 25 at a right angle. Therefore, the image sensor is configured so that the image blur is symmetric using the first moving mechanism 27. The tilt angles θ and φ of 25 are adjusted, and further, the adjustment in the XY directions is performed so that the light reaching the image sensor 25 is positioned at the center of the image sensor 25. At that time, the reduction of the light collection with respect to the image sensor 25 is corrected by shifting in the ± Z direction as needed. In this case, the arithmetic control processing unit 28 first calculates an illuminance distribution based on the center of the image of the central axis ray on the image sensor 25 and the illuminance at the center, and makes the calculated illuminance distribution uniform. Therefore, the tilt angles θ and φ of the image sensor 25 are calculated, and a control signal based on the calculated tilt angles θ and φ is output to the first moving mechanism 27. Next, a control signal for positioning the center of the image of the central axis ray at the center of the image sensor 25 is generated and output to the first moving mechanism 27.

  Next, as shown in FIG. 5, the aperture 32 is removed, and the remaining second lens element 40 constituting the lens system 22 is fixed by the second holding unit 35, and imaged by the first moving mechanism 27 as needed. While adjusting the position of the image sensor 25 in the Z direction so that a focused spot is imaged on the element 25, the second holding unit 35 is shifted in the XYZ directions by the second moving mechanism 36 and the tilt angle is adjusted. To do. In this case, the image on the image sensor 25 changes as shown in FIGS. 7 and 8 show a case where the first lens element 39 of the lens system 22 and the second lens element 40 to be adjusted are relatively decentered or tilted. However, FIG. 7 is before adjustment of the second lens element 40, and FIG. 8 is under adjustment of the second lens element 40.

  In FIG. 7, the positions of the condensing spot 42 of the reference light beam that has passed through the opening 29 of the substrate 24 and the center 41 of the image sensor 25 are shifted. However, by performing the XYZ adjustment and the tilt angle adjustment of the second lens element 40, the condensing spot 42 of the reference light beam coincides with the center 41 of the image sensor 25 as shown in FIG. In this case, the arithmetic control processing unit 28 positions the condensing spot 42 of the reference light beam at the center of the image sensor 25 according to the amount of deviation between the condensing spot 42 on the image sensor 25 and the center 41 of the image sensor 25. Control signal is generated and output to the second moving mechanism 36.

  Further, light rays corresponding to the respective field angles deflected through the respective diffraction elements 23 in the substrate 24 are incident on the lens system 22 to form a group of focused spots 43 on the image sensor 25. The group of the condensing spots 43 is arranged so as to be symmetric with respect to the condensing spot 42 of the central ray as shown in FIG. 9 by performing XYZ adjustment and tilt angle adjustment of the second lens element 40. Is done. In that case, the arithmetic control processing unit 28 calculates the center of gravity of the group of the condensing spots 43 based on the illuminance distribution of the condensing spot 43 on the image sensor 25, and positions the calculated center of gravity in the condensing spot 42. The control signal is generated and output to the second moving mechanism 36.

  Therefore, when the second lens element 40 is adjusted as shown in FIG. 9, the first lens element 39 and the second lens element 40 of the lens system 22 composed of a plurality of lenses are substantially free from decentration and tilt. Will be adjusted so that. Furthermore, the image sensor 25 is also adjusted to an optimal position with respect to the lens system 22.

  7 to 9, all the focused spots 42 and 43 are simply indicated by circles. However, in actuality, since the optical aberration due to lens tilt, decentration, etc. occurs, the focused spots 42 and 43 do not become round.

  Further, since the temporary adjustment is being performed at the stage shown in FIG. 9, the second lens system 40 and the image sensor 25 in the lens system 22 are not fixed until the next MTF inspection process is completed.

  Next, a method for measuring the MTF value will be described. The measurement of the MTF value is performed using a cross-shaped slit 30 formed on the substrate 24 on which the diffraction element 23 is formed and illuminated uniformly from the light source side.

  First, the lens system 22 after the optical axes of the first and second lens elements 39 and 40 and the image sensor 25 are adjusted as described above is used for the illuminance of the image of the slit 30 on the light receiving surface of the image sensor 25. The lens system 22 is focused on the surface of the substrate 24 so that the cross-shaped slit 30 is imaged on the image sensor 25. In this state, as shown in FIG. 9, an image 44 of the cross-shaped slit 30 is formed on the light receiving surface of the image sensor 25. After that, as shown in FIG. 10, the arithmetic control processing unit 28 obtains the intensity distribution in the radial direction and the tangential direction at the dotted line portion in the image 44 of the cross-shaped slit 30, and FIG. 11 (a) and FIG. An intensity distribution as shown in 12 (a) is obtained. Then, by performing Fourier transform on this intensity distribution, the MTF value is simply measured as shown in FIGS. 11 (b) and 12 (b).

  At this stage, if there is no problem with the MTF value (that is, if the difference between the calculated MTF value and the target MTF value is within the allowable range), as shown in FIG. The lens elements 39 and 40 of the lens system 22 and the image sensor 25 are fixed with an adhesive 45 or the like. Further, if there is a problem with the MTF value, the second holding unit 35 is controlled by the second moving mechanism 36 based on the difference between the target MTF value and the calculated MTF value, and the lens system 22 again. The optical axis adjustment is performed as described above.

  The first and second lens elements 39 and 40 and the image sensor 25 are fixed by, for example, supplying an ultraviolet curable adhesive as an adhesive 45 from an adhesive supply unit (not shown), and an ultraviolet irradiation unit. This is performed by irradiating with ultraviolet rays (not shown). Reference numeral 46 denotes an ND filter disposed between the light source 21 and the substrate 24.

  Thus, the optical axis / position adjustment process of the lens system 22 composed of a plurality of lenses and the imaging device 25, the optical axis adjustment process of the lens system 22, and the inspection process of the lens system 22 using the MTF, It can be performed continuously by the same lens system adjusting device. Moreover, the occurrence of defective products can be reduced by performing the optical axis adjustment step again based on the result of the inspection step.

  Further, the movement of the image sensor 25 and the second holding unit 35 by the first moving mechanism 27 and the second moving mechanism 36 at that time is generated by the arithmetic control processing unit 28 based on the outputs from the image sensors 25 and 33. By the control signal. Therefore, the optical axis / position adjustment of the lens system 22 and the image sensor 25, the optical axis adjustment of the lens system 22, and the inspection of the lens system 22 can be performed automatically and continuously.

  As described above, in the present embodiment, after the adjustment, the first movement that moves the image sensor 25 via the holding unit 26 to the image sensor 25 that forms a camera lens such as a digital camera integrally with the lens system 22. A mechanism 27 is provided. As shown in FIG. 3, the first light beam 21, the aperture 29, the light branching element 31, the aperture 32, and the photodetector 33 are used so that the center axis light beam and the center of the photodetector 33 coincide with each other. The moving mechanism 27 adjusts the angle and position of the image sensor 25. Accordingly, the angle and position between the reference plane of the lens system 22 (the surface of the image sensor 25) and the reference axis (reference axis A) of the adjusting device can be adjusted in advance.

  In addition, the first lens element 39 of the lens system 22 composed of a plurality of lenses is fixed by the first holding unit 34, and the blurring of the image is symmetric with respect to the center of the image sensor 25, so The image sensor 25 is moved by the first moving mechanism 27 so that the light is condensed at the center of the image sensor 25. Therefore, the optical axis adjustment and the position adjustment between the lens system 22 and the image pickup device 25 that constitute a camera lens such as a digital camera after the adjustment can be automatically performed continuously.

  In addition, a substrate 24 on which a diffraction element 23 is formed so as to be point symmetric at positions corresponding to the respective angles of view of the lens system 22 is disposed between the light source 21 and the first lens element 39. Then, the second lens element 40 constituting the lens system 22 is fixed by the second holding unit 35, and the condensing spot 42 of the reference beam coincides with the center 41 of the image sensor 25, so that each diffraction element 23 of the substrate 24. The second holding unit 35 is moved by the second moving mechanism 36 so that the group of the condensed spots 43 of the light beams deflected corresponding to each angle of view is symmetric with respect to the center 41 of the image sensor 25. I am doing so. Therefore, the optical axis of the lens system 22 can be adjusted with high accuracy using light beams corresponding to a plurality of angles of view.

  Further, the lens system 22 with the adjusted optical axis is focused on the surface of the substrate 24, and a cross-shaped slit 30 is imaged on the image sensor 25. Then, the MTF value is measured by obtaining the intensity distribution in the radial direction and the tangential direction in the image 44 of the cross-shaped slit 30 by the arithmetic control processing unit 28, and Fourier transforming this intensity distribution. Yes. Therefore, following the adjustment of the optical axis of the lens system 22, the MTF value that is an index of the resolving power of the lens system 22 can be automatically and easily measured. Further, when the measurement result of the MTF value is bad, the optical axis of the lens system 22 can be adjusted again based on the measurement result of the MTF value. Therefore, the occurrence rate of defective products can be reduced.

  In the above embodiment, the parallel light from the light source 21 is condensed and formed on the image sensor 25 by the lens system 22 based on the output signal from the image sensor 25 in the arithmetic control processor 28. The peak value of the light intensity of the focused spots 42 and 43 is obtained, and the function as the light amount adjusting means for adjusting the light amount of the light source according to the peak value can be provided. By doing so, it is possible to control the amount of light so that smear does not occur in the image sensor 25 even when the optical axis is adjusted, even if the light spot has a high energy density.

  In the above-described embodiment, the MTF measurement slit 30 is provided on the substrate 24 separately from the diffraction element 23 as the MTF measurement pattern. However, the MTF measurement pattern can also be formed on the diffraction element 23. In such a case, it is not necessary to provide a slit or chart for MTF measurement separately from the diffraction element 23, and the configuration of the substrate 24 is simplified. Further, the MTF can be measured using the diffraction element 23, and the optical adjustment during the MTF measurement can be eliminated, and the MTF measurement can be performed efficiently following the adjustment of the optical axis of the lens system 22.

  Further, in the above-described embodiment, as the image sensor used for various adjustments, the image sensor 25 that is integrated with the lens system 22 after the adjustment and constitutes a camera lens such as a digital camera is used. However, an image sensor dedicated for adjustment may be used. However, in that case, after the optical axis adjustment of the lens system 22 and the measurement of the MTF value are completed, it is necessary to adjust the position of the imaging system and the lens system 22 constituting the camera lens.

  In the above embodiment, the lens system 22 is composed of two lens elements, ie, the first lens element 39 and the second lens element 40. However, the lens system 22 may be composed of three or more lens elements. Similarly, the optical axis of the lens system can be adjusted. Even in that case, the lens element closest to the image sensor 25 may be held by the second holding unit 35 to adjust the position and angle.

  In the above embodiment, the light source 21, the substrate 24, the holding unit 26, the first moving mechanism 27, the calculation control processing unit 28, the first holding unit 34, the second holding unit 35, and the second moving mechanism 36 are used. A lens system adjustment apparatus that is configured roughly and performs optical adjustment on the lens system 22 and the image sensor 25 has been described. However, the lens system adjustment device is an apparatus for manufacturing the image pickup device because it performs optical adjustment on the lens system 22 and the image pickup element 25 that together form an image pickup device such as a digital camera. Can also be considered.

It is a schematic block diagram in the lens system adjustment apparatus of this invention. It is a top view of the board | substrate in FIG. It is a figure which shows a mode at the time of making a right angle with the reference plane of a lens system, and a reference axis by the lens system adjustment apparatus shown in FIG. It is a figure which shows a mode at the time of performing the optical axis and position adjustment of a lens system and an image pick-up element by the lens system adjustment apparatus shown in FIG. It is a figure which shows the mode at the time of performing the optical axis adjustment of a lens system with the lens system adjustment apparatus shown in FIG. It is a figure which shows the state which fixed the lens system and image pick-up element after an optical axis adjustment with the adhesive agent etc. It is a figure which shows the image on an image pick-up element before adjustment of a 2nd lens element. It is a figure which shows the image on an image pick-up element during adjustment of a 2nd lens element. It is a figure which shows the image on an image pick-up element in the completion of adjustment of a 2nd lens element. It is a figure which shows the direction at the time of calculating | requiring the intensity distribution of the image of the slit in FIG. It is a figure which shows intensity distribution and MTF to the radial direction in FIG. It is a figure which shows intensity distribution and MTF to a tangential direction in FIG. It is a schematic block diagram of the conventional MTF measuring apparatus. It is a figure which shows intensity distribution obtained by the MTF measuring apparatus shown in FIG. It is a figure which shows the MTF value based on the intensity distribution shown in FIG. It is a schematic block diagram of the conventional optical axis adjustment apparatus.

Explanation of symbols

21 ... light source,
22 ... Lens system
23 ... Diffraction element,
24 ... substrate,
25. Image sensor,
26 ... holding part,
27. First moving mechanism,
28. Arithmetic control processing unit,
29 ... Opening,
30 ... Slit,
31 ... Optical branching element (half mirror),
32 ... Aperture,
33 ... photodetector (imaging device),
34. First holding unit,
35 ... second holding unit,
36 ... second moving mechanism,
39: First lens element,
40 ... second lens element,
41 ... the center of the image sensor 25,
42 ... Condensing spot of reference beam (central beam),
43... The condensed spot of the light beam deflected by the diffraction element 23
44 ... image of the slit 30,
45. Adhesive.

Claims (8)

A laser emitting section for generating parallel light rays serving as a reference axis;
A to-be-adjusted object including a lens system composed of a plurality of lenses and an image sensor;
It is disposed between the laser light emitting unit and the object to be adjusted, and deflects a part of the parallel light beam from the laser light emitting unit so that the angle with the reference axis is an angle corresponding to the angle of view of the lens system. A plurality of diffractive elements that generate a certain parallel beam bundle and enter the lens system, and pass a part of the parallel beam from the laser light emitting unit located at the center portion to obtain a reference beam bundle as the reference axis A substrate formed with an opening to be generated and incident on the lens system;
A moving unit for moving at least one of the lens system and the image sensor;
Based on the output of the image sensor, movement of the lens system or image sensor for positioning the image of the reference beam and the image of the deflected beam at a predetermined position on the light receiving surface of the image sensor A lens system adjusting apparatus comprising: an arithmetic control processing unit that calculates an amount and controls an operation of the moving unit based on the calculated moving amount. The lens system adjusting device according to claim 1,
An optical branching element disposed between the substrate and the object to be adjusted on the reference axis;
An aperture disposed between the optical branching element and the object to be adjusted on the reference axis;
The light is emitted from the light source unit, passes through the opening of the substrate, the light branching element, and the aperture, is reflected by the reference surface of the imaging element, passes through the aperture again, and is orthogonal to the reference axis by the light branching element. A lens system adjusting apparatus comprising a photodetector that detects light reflected in a direction to be reflected. The lens system adjusting device according to claim 1,
The diameter of the parallel light beam that is deflected by the diffraction element of the substrate and is incident on the lens system, and the diameter of the reference light beam that is incident on the lens system through the opening of the substrate are the lens A lens system adjusting apparatus, wherein the lens system adjusting apparatus is set to be larger than a diameter of an entrance pupil of the system. The lens system adjusting device according to claim 1,
The moving unit is configured to move the lens system and the image sensor,
A first holding unit that fixes and holds a first lens element that forms part of the lens system with respect to the reference axis;
A second holding unit for holding a second lens element constituting the remainder of the lens system;
A lens system adjusting apparatus comprising: a lens element moving mechanism configured to move the lens system and move at least one of the first holding unit and the second holding unit. The lens system adjusting device according to claim 4,
The substrate is provided with a chart for MTF measurement,
Illuminating means for uniformly illuminating the chart from the laser light source unit side,
The lens system adjusting apparatus, wherein the arithmetic control processing unit calculates an MTF value of the lens system based on an output of the imaging device relating to the chart. The lens system adjusting device according to claim 1,
Based on the output of the image sensor, the peak value of the light intensity of the spot formed by collimating the parallel light beam emitted from the laser light source unit on the light receiving surface of the image sensor by the lens system is determined. A lens system adjusting apparatus comprising a light amount adjusting means for adjusting a light amount of the laser light source unit according to a peak value. A lens system adjustment method using the lens system adjustment device according to claim 4,
A step of controlling the operation of the moving unit by the arithmetic control processing unit to move the image sensor so that the image of the reference beam passing through the opening of the substrate is positioned at the center of the light receiving surface of the image sensor. When,
Holding the first lens element fixed with respect to the reference axis by the first holding unit, and holding the second lens element by the second holding unit;
The operation of the lens element moving mechanism is controlled by the arithmetic control processing unit, and the light collection spot by the first lens element and the second lens element of the reference beam bundle that has passed through the opening of the substrate is received by the image sensor. Moving at least one of the first holding unit and the second holding unit so as to be located at the center of the surface;
The operation of the lens element moving mechanism is controlled by the arithmetic control processing unit, and the condensed spot by the first lens element and the second lens element of the light bundle deflected through the diffraction element of the substrate is Moving at least one of the first holding unit and the second holding unit so as to be arranged at a predetermined position on the light receiving surface of the imaging element;
Fixing the lens system and the image sensor with respect to the reference axis. A lens system adjustment method using the lens system adjustment device according to claim 5,
A step of controlling the operation of the moving unit by the arithmetic control processing unit to move the image sensor so that the image of the reference beam passing through the opening of the substrate is positioned at the center of the light receiving surface of the image sensor. When,
Holding the first lens element fixed with respect to the reference axis by the first holding unit, and holding the second lens element by the second holding unit;
The operation of the lens element moving mechanism is controlled by the arithmetic control processing unit, and the light collection spot by the first lens element and the second lens element of the reference beam bundle that has passed through the opening of the substrate is received by the image sensor. Moving at least one of the first holding unit and the second holding unit so as to be located at the center of the surface;
The operation of the lens element moving mechanism is controlled by the arithmetic control processing unit, and the condensed spot by the first lens element and the second lens element of the light bundle deflected through the diffraction element of the substrate is Moving at least one of the first holding unit and the second holding unit so as to be arranged at a predetermined position on the light receiving surface of the imaging element;
The operation of the lens element moving mechanism is controlled by the arithmetic control processing unit, and an image of light from the illuminating means that has passed through the MTF measurement chart of the substrate is formed on the light receiving surface of the imaging element. And moving the first holding unit and the second holding unit,
A step of calculating an MTF value by the arithmetic control processing unit based on an output of the imaging element related to the image of the chart;
A step of fixing the lens system and the imaging device with respect to the reference axis when the difference between the calculated MTF value of the lens system and the target MTF value is within a predetermined range. The lens system adjustment method characterized by this.

Images