JP2010230745A - Lens alignment device and method for controlling the lens alignment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens alignment device capable of achieving shortening of lens alignment time, simplification of constitution and simplification of setting operation of a chart. <P>SOLUTION: The lens alignment device 1 which aligns a lens 2 by adjusting a lens for adjustment 3 includes: a light source 4; the chart 5 which is arranged between the lens 2 and the light source 4 and in which a predetermined pattern for obtaining MTF of the lens 2 is formed; three or more first sensors 6 which are arranged at positions different from each other in a direction orthogonal to an optical axis L of the lens 2 and detect contrast for obtaining MTF in an M direction that is the MTF of the lens 2 in a meridional direction; three or more second sensors which are arranged at positions different from each other in the direction orthogonal to the optical axis L of the lens 2 and detect contrast for obtaining MTF in an S direction that is the MTF of the lens in a sagital direction; and an optical axis driving mechanism 8 which changes a distance between the lens 2 and the chart 5 in the optical axis direction of the lens 2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a lens alignment device for aligning a plurality of lenses and a method for controlling the lens alignment device.

  2. Description of the Related Art Conventionally, there has been known a lens alignment device that adjusts an adjustment lens and aligns a plurality of lenses including the adjustment lens (see, for example, Patent Document 1). In the lens alignment device described in Patent Document 1, a first pattern for evaluating the contrast value of the lens in the sagittal direction and a second pattern for evaluating the contrast value of the lens in the meridional direction are formed. A chart, a rotation mechanism that rotates the chart around the optical axis of the lens, an image sensor that captures an image of the chart formed by the lens, and first and second patterns output from the image sensor And calculating means for calculating a contrast value in the sagittal direction and a contrast value in the meridional direction of the lens based on the obtained signals and obtaining a difference between the two contrast values.

  In the lens aligning device described in Patent Document 1, the calculation means calculates the difference between the contrast value in the sagittal direction and the contrast value in the meridional direction according to the rotation angle of the chart while rotating the chart at a predetermined angular pitch by the rotation mechanism. And the adjustment direction of the adjustment lens is determined based on the rotation angle of the chart in which this difference is maximum. In this lens alignment device, the adjustment amount of the adjustment lens is determined based on the difference in contrast value.

  In the lens alignment device described in Patent Document 1, the first pattern and the second pattern formed on the chart are arranged such that a portion that transmits light and a portion that does not transmit light are arranged at a predetermined pitch. The calculation means calculates a sagittal direction contrast value and a meridional direction contrast value at a spatial frequency in accordance with the arrangement pitch of a portion that transmits light and a portion that does not transmit light.

Japanese Patent No. 4112165

  However, in the lens alignment device described in Patent Document 1, the difference between the contrast value in the sagittal direction and the contrast value in the meridional direction according to the rotation angle of the chart is calculated while rotating the chart at a predetermined angular pitch. Based on this difference, the adjustment direction and adjustment amount of the adjustment lens are determined. Therefore, it takes time to determine the adjustment direction and adjustment amount of the lens for adjustment, and as a result, it takes time to align the lens.

  Further, in the lens aligning device described in Patent Document 1, the contrast value in the sagittal direction and the contrast in the meridional direction at a spatial frequency according to the arrangement pitch between the light transmitting portion and the light non-transmitting portion formed on the chart. Only the value can be obtained. Therefore, in this lens aligning device, it is necessary to prepare a plurality of charts having different patterns in accordance with the characteristics required for the lens to be aligned, and the configuration of the device becomes complicated. Further, in this lens aligning device, it is necessary to set charts with different patterns in accordance with the characteristics required for the lens to be aligned, and the chart setting operation becomes complicated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a lens alignment apparatus that can shorten the alignment time of a lens and that can simplify the configuration and the setting operation of a chart. Another object of the present invention is to provide a method for controlling a lens alignment apparatus that can shorten the alignment time of the lens.

  In order to solve the above-described problem, the present invention provides a light source that emits light toward a lens in a lens alignment device that adjusts an adjustment lens among a plurality of lenses and performs lens alignment. Arranged between the lens and the light source, the chart on which a predetermined pattern for obtaining the MTF of the lens is formed, and three or more different positions in the direction orthogonal to the optical axis of the lens, and in the meridional direction The first sensor for detecting the contrast for obtaining the M direction MTF, which is the MTF of the lens, and the S direction, which is the MTF of the lens in the sagittal direction, are arranged at three or more different positions in the direction orthogonal to the optical axis of the lens. The distance between the second sensor for detecting the contrast for obtaining the MTF and the lens in the optical axis direction of the lens and the chart Or, characterized in that it comprises an optical axis direction drive mechanism for changing the distance between the first sensor and the second sensor and the lens.

  The lens alignment device of the present invention includes a chart on which a predetermined pattern for determining the MTF of the lens is formed, a first sensor for detecting contrast for determining the M direction MTF, and an S direction MTF. A second sensor for detecting contrast, and an optical axis direction driving mechanism for changing a distance between the lens and the chart in the optical axis direction of the lens, or a distance between the first sensor and the second sensor and the lens. The first sensor and the second sensor are arranged at three or more different positions in the direction orthogonal to the optical axis of the lens.

  Therefore, in the present invention, when the lens aligning device includes a control unit that controls the lens aligning device, the control unit is configured such that the distance between the lens and the chart in the optical axis direction by the optical axis direction driving mechanism, Alternatively, the M direction MTF is calculated based on the contrast detected by each of the first sensors while changing the distances between the first sensor and the second sensor and the lens, and is detected by each of the second sensors. The S direction MTF is calculated based on the contrast to be calculated, the M direction defocus characteristic that is the defocus characteristic of the lens at a specific spatial frequency is calculated based on each of the M direction MTFs, and based on each of the S direction MTFs. The S direction defocus characteristic that is the defocus characteristic of the lens at a specific spatial frequency is calculated, The inclination of the meridional image plane relative to the optical axis or a plane orthogonal to the optical axis is calculated based on each of the characteristics, and the sagittal image plane relative to the optical axis or the plane orthogonal to the optical axis is calculated based on each of the S-direction defocus characteristics. The inclination can be calculated, and the adjustment amount of the adjustment lens can be calculated based on the inclination of the meridional image plane and the inclination of the sagittal image plane.

  Therefore, in the present invention, it is not necessary to calculate the adjustment amount of the adjustment lens while rotating the chart at a predetermined angular pitch, and the lens alignment time is compared with the lens alignment apparatus described in Patent Document 1. Can be shortened. In the present invention, since a predetermined pattern for obtaining the MTF of the lens is formed on the chart, the M direction defocus value and the S direction defocus value at various spatial frequencies are calculated using the common chart. It becomes possible to do. Therefore, it is not necessary to prepare a chart having a different pattern or to set a chart having a different pattern according to the characteristics required for the lens to be aligned. As a result, according to the present invention, it is possible to simplify the configuration of the lens aligning device and simplify the chart setting operation.

  In the present invention, for example, the first sensor is arranged at four positions with a pitch of about 90 ° around the optical axis, and the second sensor is arranged at four places with a pitch of about 90 ° around the optical axis. The first sensor and the second sensor are arranged on substantially the same plane orthogonal to the optical axis so as to be shifted by approximately 45 ° about the optical axis. With this configuration, the lens moving mechanism that moves the adjustment lens when aligning the lens is configured to move the adjustment lens in two directions orthogonal to the optical axis direction and orthogonal to each other, for example. If this is the case, the amount of movement of the adjustment lens can be calculated relatively easily.

  In the present invention, the chart includes three or more first light transmission portions for obtaining the M direction MTF and three or more second light transmission portions for obtaining the S direction MTF. The predetermined pattern is preferably a first edge pattern formed by the edge of the first light transmission portion and a second edge pattern formed by the edge of the second light transmission portion. . With this configuration, the focus of the image of the chart pattern formed on the first sensor or the second sensor is blurred compared to the case where the predetermined pattern formed on the chart is a slit or the like. However, the contrast can be appropriately detected by the first sensor or the second sensor.

  In order to solve the above-described problem, the control method of the lens aligning device of the present invention is orthogonal to the chart on which a predetermined pattern for obtaining the MTF of a plurality of lenses is formed and the optical axis of the lens. A first sensor for detecting a contrast for obtaining an M-direction MTF, which is an MTF of the lens in the meridional direction, and three or more different in the direction orthogonal to the optical axis of the lens. And a second sensor for detecting a contrast for obtaining the S direction MTF, which is the MTF of the lens in the sagittal direction, and adjusting the adjustment lens of the lenses to adjust the lens. A method for controlling a core device, the distance between the lens and the chart in the optical axis direction of the lens, or the first sensor and While changing the distance between the second sensor and the lens, the M-direction MTF is calculated based on the contrast detected by each of the first sensors, and S based on the contrast detected by each of the second sensors. An MTF calculation step for calculating the direction MTF and an M direction defocus characteristic that is a defocus characteristic of the lens at a specific spatial frequency based on each of the M direction MTF calculated in the MTF calculation step, and an MTF calculation step A defocus characteristic calculation step for calculating an S direction defocus characteristic that is a defocus characteristic of a lens at a specific spatial frequency based on each of the S direction MTFs calculated in step M, and an M direction calculated in the defocus characteristic calculation step Optical axis or light based on each of defocus characteristics And the inclination of the sagittal image plane with respect to the optical axis or the plane orthogonal to the optical axis based on each of the S-direction defocus characteristics calculated in the defocus characteristic calculation step. An image plane inclination calculating step to calculate, and a lens adjustment amount calculating step for calculating an adjustment amount of the adjustment lens based on the meridional image plane inclination and the sagittal image plane inclination calculated in the image plane inclination calculating step. It is characterized by that.

  In the control method of the lens alignment device of the present invention, the M direction MTF and the S direction MTF are calculated in the MTF calculation step, the M direction defocus characteristic and the S direction defocus characteristic are calculated in the defocus characteristic calculation step, and the image plane The inclination calculation step calculates the inclination of the meridional image plane and the sagittal image plane relative to the optical axis of the lens or a plane perpendicular to the optical axis, and the lens adjustment amount calculation step calculates the inclination of the meridional image plane and the sagittal image plane. Based on this, the adjustment amount of the adjustment lens is calculated. Therefore, in the present invention, it is not necessary to calculate the adjustment amount of the adjustment lens while rotating the chart at a predetermined angular pitch, and the lens alignment time can be shortened.

  In the present invention, in the image plane inclination calculation step, for example, the inclination of the meridional image plane is calculated based on the deviation of the respective peak values of the M direction defocus characteristic, and the deviation of the respective peak values of the S direction defocus characteristic is calculated. Based on this, the inclination of the sagittal image plane is calculated.

  In the present invention, the control method of the lens aligning apparatus includes a lens adjustment step for moving the adjustment lens based on the adjustment amount of the adjustment lens calculated in the lens adjustment amount calculation step. For example, the lens adjustment amount calculation step Then, the adjustment amount of the adjustment lens in the direction orthogonal to the optical axis is calculated, and in the lens adjustment step, the adjustment lens is moved in the direction orthogonal to the optical axis.

  In this case, the first sensor is arranged at four positions with a pitch of about 90 ° around the optical axis, and the second sensor is arranged at four places with a pitch of about 90 ° around the optical axis. The first sensor and the second sensor are preferably disposed on substantially the same plane orthogonal to the optical axis so as to be shifted by approximately 45 ° about the optical axis. With this configuration, it is possible to relatively easily calculate the movement amount of the adjustment lens in the lens adjustment amount calculation step.

  In the present invention, the control method of the lens aligning apparatus includes a lens adjustment step for moving the adjustment lens based on the adjustment amount of the adjustment lens calculated in the lens adjustment amount calculation step. In the lens adjustment amount calculation step, Calculate the adjustment amount of the adjustment lens so that the absolute value of the inclination of the meridional image plane relative to the optical axis and the absolute value of the inclination of the sagittal image plane relative to the optical axis are approximately equal. In the lens adjustment step, the meridional image relative to the optical axis is calculated. It is preferable to move the adjustment lens so that the absolute value of the tilt of the surface and the absolute value of the tilt of the sagittal image surface with respect to the optical axis are substantially equal. With such a configuration, in the lens adjustment step, it is possible to appropriately align the lens in consideration of the balance between the inclination of the meridional image plane and the inclination of the sagittal image plane with respect to the optical axis.

  As described above, in the lens alignment device of the present invention, the lens alignment time can be shortened, and the configuration can be simplified and the chart setting operation can be simplified. In addition, according to the control method of the lens alignment device of the present invention, it is possible to shorten the lens alignment time.

It is the schematic which shows schematic structure of the lens aligning apparatus concerning embodiment of this invention. It is a figure for demonstrating the arrangement | positioning relationship of the 1st sensor shown in FIG. 1, and a 2nd sensor from an optical axis direction. It is a figure which shows the chart shown in FIG. 1 from an optical axis direction. It is an enlarged view of the E section of FIG. 3 is a flowchart for explaining an example of a control method of the lens alignment apparatus shown in FIG. 1. It is a conceptual diagram for demonstrating the calculation method of MTF in the MTF calculation step shown in FIG. FIG. 6 is a conceptual diagram for explaining an MTF calculation method in an MTF calculation step and a defocus characteristic calculation method in a defocus characteristic calculation step shown in FIG. 5. FIG. 6 is a conceptual diagram for explaining a method of calculating the inclination of the meridional image plane and the inclination of the sagittal image plane in the image plane inclination calculation step shown in FIG. 5. It is a conceptual diagram for demonstrating the calculation method of the lens adjustment amount in the lens adjustment amount calculation step shown in FIG. It is a figure for demonstrating the arrangement | positioning relationship of the 1st sensor concerning 2nd Embodiment of this invention, a 2nd sensor, and a 3rd sensor from an optical axis direction. It is a figure which shows the chart concerning other embodiment of this invention from an optical axis direction.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Configuration of lens alignment device)
FIG. 1 is a schematic diagram showing a schematic configuration of a lens alignment device 1 according to an embodiment of the present invention. FIG. 2 is a diagram for explaining the positional relationship between the first sensor 6 and the second sensor 7 shown in FIG. 1 from the optical axis direction. FIG. 3 is a diagram showing the chart 5 shown in FIG. 1 from the optical axis direction. FIG. 4 is an enlarged view of a portion E in FIG.

  As shown in FIG. 1, the lens alignment device 1 of the present embodiment is a device for adjusting the lens 3 for adjustment among the multiple lenses (lens group) 2 and aligning the lens 2. is there. As shown in FIGS. 1 and 2, the lens aligning device 1 includes a light source 4 that emits light toward the lens 2, a chart 5 on which a predetermined pattern for obtaining the MTF of the lens 2 is formed, A first sensor 6 (hereinafter referred to as “first sensor 6”) that detects contrast for obtaining the M direction MTF, which is the MTF of the lens 2 in the meridional direction, and S, which is the MTF of the lens 2 in the sagittal direction. And a second sensor 7 (hereinafter referred to as “second sensor 7”) that detects contrast for obtaining the direction MTF. The lens alignment device 1 also moves the chart driving mechanism 8 that drives the chart 5 in the direction of the optical axis L (optical axis direction) of the lens 2 and the adjustment lens 3 when aligning the lens 2. A lens moving mechanism 9 and a control unit 10 that performs various controls of the lens alignment device 1 are provided. In the following description, two directions orthogonal to the optical axis L and orthogonal to each other are defined as an X direction and a Y direction.

  The lens 2 is composed of, for example, one adjustment lens 3 and three fixed lenses 12 to 14. The fixed lenses 12 to 14 are fixed to a lens barrel (lens holding member) 15. The lens barrel 15 is fixed to a barrel fixing member (not shown) constituting the lens alignment device 1. The adjustment lens 3 is fixed to the lens holding member 16. The lens holding member 16 is attached to the lens moving mechanism 9. The number of adjustment lenses 3 included in the lens 2 may be two or more. In this embodiment, the adjustment lens 3 is disposed on the right side of the fixed lenses 12 to 14 in FIG. 1, but the adjustment lens 3 may be disposed on the left side of the fixed lenses 12 to 14 in FIG. 1. good.

  The first sensor 6 and the second sensor 7 are one-dimensional image sensors (line sensors). For example, the first sensor 6 and the second sensor 7 are linear CCD sensors constituted by a plurality of CCDs and the like arranged in a straight line, and the shape when viewed from the optical axis direction is an elongated rectangular shape. Is formed. As shown in FIG. 2, the lens alignment device 1 of the present embodiment includes four first sensors 6 and four second sensors 7, and the four first sensors 6 and the second sensors 7. Is arranged on the opposite side of the light source 4 and the chart 5 with respect to the lens 2. The first sensor 6 and the second sensor 7 may be a two-dimensional image sensor (area sensor). However, since the line sensor has a higher frame rate than the area sensor and can be scanned at high speed, the first sensor 6 and the second sensor 7 are preferably line sensors.

  The first sensor 6 is arranged so that its longitudinal direction (CCD arrangement direction) and the meridional direction of the lens 2 substantially coincide. In this embodiment, two of the four first sensors 6 are arranged such that the longitudinal direction and the X direction are substantially parallel, and the remaining two first sensors 6 are The longitudinal direction and the Y direction are arranged substantially parallel to each other. That is, the first sensors 6 are arranged at four locations with a pitch of about 90 ° with the optical axis L as the center.

  The second sensor 7 is arranged so that its longitudinal direction (CCD arrangement direction) and the sagittal direction of the lens 2 substantially coincide. In the present embodiment, the four second sensors 7 are arranged such that the longitudinal direction thereof is inclined by approximately 45 ° with respect to the X direction and the Y direction. Specifically, the second sensor 7 is arranged at four positions with a substantially 90 ° pitch centered on the optical axis L, and the first sensor 6 and the second sensor 7 are centered on the optical axis L. It is shifted by approximately 45 °. The first sensor 6 and the second sensor 7 are disposed on substantially the same plane orthogonal to the optical axis L.

  The chart 5 is disposed between the lens 2 and the light source 4 in the optical axis direction. Further, between the light source 4 and the chart 5 in the optical axis direction, a light pipe 18 and a diffusion plate 19 are arranged in this order from the light source 4 toward the chart 5.

  As shown in FIG. 3, the chart 5 is formed in a disk shape having a circular shape when viewed from the optical axis direction. This chart 5 includes four first light transmission parts 5a (hereinafter referred to as “first light transmission parts 5a”) for obtaining the M-direction MTF and four pieces for obtaining the S-direction MTF. The second light transmission part 5b (hereinafter referred to as "second light transmission part 5b") is formed. The chart 5 of this embodiment is made of, for example, quartz glass, and is a mask that prevents light from being transmitted to the surface of the chart 5 (the hatched portion in FIG. 3) excluding the first light transmitting portion 5a and the second light transmitting portion 5b. As a result, the first light transmission part 5a and the second light transmission part 5b are formed.

  As shown in FIG. 4, the edge of the first light transmitting portion 5a is concentric with the large-diameter arc portion 5c formed in an arc shape centered on the optical axis L and the large-diameter arc 5c centered on the optical axis L. Are formed between the large-diameter arc portion 5c and the small-diameter arc portion 5d along the radial direction of the chart 5. It is comprised from the two radial direction linear parts 5e.

  The four first light transmission parts 5a are arranged at a substantially 90 ° pitch with the optical axis L as the center. Specifically, as shown in FIG. 3, a line connecting the centers in the circumferential direction of the two first light transmission parts 5 a arranged symmetrically with respect to the optical axis L is parallel to the X direction or the Y direction. Thus, the four first light transmission parts 5a are arranged. That is, the four first light transmission parts 5a are formed so as to correspond to the arrangement positions of the first sensors 6 arranged in four places. Therefore, the light emitted from the light source 4 and having passed through the first light transmission part 5 a is transmitted through the lens 2 and enters the first sensor 6. Specifically, the light emitted from the light source 4 and having passed through the radially inner portion of the first light transmitting portion 5 a passes through the lens 2 and enters the first sensor 6.

  Therefore, in the first sensor 6 of this embodiment, the contrast is detected with the position corresponding to the small-diameter arc portion 5d as a boundary. That is, in this embodiment, the first edge pattern for obtaining the M direction MTF is formed by the small-diameter arc portion 5d of the first light transmission portion 5a.

  As shown in FIG. 4, the edge of the second light transmitting portion 5b is concentric with the large-diameter arc portion 5f formed in an arc shape centered on the optical axis L and the large-diameter arc portion 5f centered on the optical axis L. Between the large-diameter arc portion 5f and the small-diameter arc portion 5g along the radial direction of the chart 5 and the small-diameter arc portion 5g formed in an arc shape having a smaller radius than the large-diameter arc portion 5f. It comprises two radial direction straight parts 5h formed. The radius of the large-diameter arc portion 5f is larger than the radius of the large-diameter arc portion 5c, and the radius of the small-diameter arc portion 5g is smaller than the radius of the small-diameter arc portion 5d.

  The four second light transmission parts 5b are arranged at a pitch of approximately 90 ° with the optical axis L as the center. Specifically, the four second light transmission portions 5b are arranged so that the radial straight portion 5h on the clockwise side of the second light transmission portion 5b is inclined by approximately 45 ° with respect to the X direction and the Y direction. Yes. That is, the four second light transmission parts 5b are formed so as to correspond to the arrangement positions of the second sensors 7 arranged in four places. Therefore, the light emitted from the light source 4 and having passed through the second light transmission part 5 b is transmitted through the lens 2 and enters the second sensor 7. Specifically, the light emitted from the light source 4 and passing through the clockwise side portion of the second light transmission part 5 b passes through the lens 2 and enters the second sensor 7.

  Therefore, in the second sensor 7 of the present embodiment, contrast is detected with the position corresponding to the radial straight line portion 5h on the clockwise side as a boundary. That is, in the present embodiment, the second edge pattern for obtaining the S direction MTF is formed by the radial linear portion 5h on the clockwise side of the second light transmission portion 5b.

  The chart drive mechanism 8 includes a drive source such as a motor for moving the chart 5 in the optical axis direction and a feed mechanism such as a ball screw. The chart drive mechanism 8 of this embodiment is an optical axis direction drive mechanism that changes the distance between the lens 2 and the chart 5 in the optical axis direction.

  The lens moving mechanism 9 includes a driving source such as a motor for moving the lens holding member 16 in the X direction and the Y direction, and a feeding mechanism such as a ball screw. That is, in the lens alignment device 1 of this embodiment, the lens 2 is aligned by moving the adjustment lens 3 in the X direction and the Y direction by the lens moving mechanism 9.

  A first sensor 6 and a second sensor 7 are connected to the control unit 10. The control unit 10 is also connected with a chart driving mechanism 8 and a lens moving mechanism 9. As will be described below, the control unit 10 calculates the M direction MTF and the S direction MTF, as well as the M direction defocus characteristic and the S direction, which are defocus (through focus) characteristics at a specific spatial frequency in the M direction MTF. An S-direction defocus characteristic that is a defocus characteristic at a specific spatial frequency of the MTF is calculated. Further, the control unit 10 calculates the inclination of the meridional image plane with respect to the optical axis L or a plane orthogonal to the optical axis L based on the M direction defocus characteristic, and also calculates the optical axis L or the light based on the S direction defocus characteristic. The inclination of the sagittal image plane with respect to the plane orthogonal to the axis L is calculated. Further, the control unit 10 calculates the adjustment amount of the adjustment lens 3 based on the inclination of the meridional image plane and the inclination of the sagittal image plane.

  In the lens alignment device 1 of the present embodiment, the MTF is obtained using the back projection method. That is, in the lens aligning device 1, the chart 5 is arranged on the imaging surface of the imaging device in the camera or the like in which the adjusted lens 2 is mounted, and the first in the subject surface in the camera or the like in which the adjusted lens 2 is mounted. A sensor 6 and a second sensor 7 are arranged. Therefore, in the lens alignment device 1, the arrangement space of the first sensor 6 and the second sensor 7 can be increased, and a versatile sensor can be used as the first sensor 6 and the second sensor 7. become. In the lens alignment device 1, it is possible to use sensors having relatively low resolution as the first sensor 6 and the second sensor 7.

(Control method of lens alignment device)
FIG. 5 is a flowchart for explaining an example of a control method of the lens alignment apparatus 1 shown in FIG. FIG. 6 is a conceptual diagram for explaining the MTF calculation method in the MTF calculation step S1 shown in FIG. FIG. 7 is a conceptual diagram for explaining the MTF calculation method in the MTF calculation step S1 and the defocus characteristic calculation method in the defocus characteristic calculation step S3 shown in FIG. FIG. 8 is a conceptual diagram for explaining a method of calculating the inclination of the meridional image plane and the inclination of the sagittal image plane in the image plane inclination calculation step S4 shown in FIG. FIG. 9 is a conceptual diagram for explaining a lens adjustment amount calculation method in the lens adjustment amount calculation step S6 shown in FIG.

  In the lens alignment device 1 configured as described above, for example, control is performed according to the flow shown in FIG. That is, first, after predetermined initial settings such as attaching the lens holding member 16 to which the adjustment lens 3 is fixed to the lens moving mechanism 9 are performed, the control unit 10 uses the chart driving mechanism 8 to light the chart 5. While scanning in the axial direction and changing the distance between the lens 2 and the chart 5 in the optical axis direction, four M-direction MTFs are calculated based on the contrast detected by each of the four first sensors 6. Four S-direction MTFs are calculated based on the contrast detected by each of the four second sensors 7 (step S1). Specifically, for example, the control unit 10 scans the chart 5 in the optical axis direction at a pitch of several μm, and at each scanning position, the M direction at each of the four sensor positions disposed at the four positions. The MTF and the S direction MTF at each of the arrangement positions of the second sensors 7 arranged at four locations are calculated.

  The calculation of the M direction MTF and the S direction MTF is performed until scanning of a predetermined distance in the chart 5 is completed. That is, the control unit 10 calculates the M direction MTF and the S direction MTF until it is determined in step S2 that the scanning of the chart 5 has been completed.

  In step S <b> 1, for example, a signal having a waveform as shown in FIG. 6A is input to the control unit 10 from the first sensor 6 or the second sensor 7. That is, the position corresponding to the small-diameter arc portion 5d of the first light transmitting portion 5a of the chart 5 or the position corresponding to the radial straight portion 5h on the clockwise side of the second light transmitting portion 5b of the chart 5 is used as a boundary. A signal having a waveform as shown in FIG. 6A in which the brightness is switched is input from the first sensor 6 or the second sensor 7 to the control unit 10. The control unit 10 differentiates the signals input from the first sensor 6 and the second sensor 7 (see FIG. 6B), and then performs frequency analysis by FFT (Fast Fourier Transform) to obtain FIG. MTF (M direction MTF and S direction MTF) as shown in FIG.

  In step S1, as described above, the M direction MTF and the S direction MTF are calculated at each scanning position while the chart 5 is scanned in the optical axis direction at a pitch of several μm. That is, as shown in FIG. 7, the MTF at each chart position is calculated while changing the position (chart position) of the chart 5 in the optical axis direction.

  Thereafter, the control unit 10 calculates an M-direction defocus characteristic that is a defocus characteristic of the lens 2 at a specific spatial frequency f based on each of the M-direction MTFs calculated in step S1, and is calculated in step S1. Based on each of the S direction MTFs, an S direction defocus characteristic that is a defocus characteristic of the lens 2 at a specific spatial frequency f is calculated (step S3). That is, as shown in FIG. 7, the control unit 10 calculates defocus characteristics (M-direction defocus characteristics and S-direction defocus characteristics) indicating the relationship between the chart position and contrast at a specific spatial frequency f.

  Specifically, the control unit 10 calculates four M-direction defocus characteristics at a specific spatial frequency f based on each of the four M-direction MTFs calculated at each chart position in step S1. At the same time, four S-direction defocus characteristics are calculated based on the four S-direction MTFs calculated at the respective chart positions in step S1. That is, the M-direction defocus characteristics at the respective positions of the first sensors 6 arranged at four locations and the S-direction defocus characteristics at the respective positions of the second sensors 7 arranged at four locations are calculated. .

  The specific spatial frequency f can be arbitrarily set by the control unit 10 based on the specifications of the lens 2. For example, when a high resolution is required for the lens 2, a relatively high spatial frequency f is set, and when a high resolution is not required for the lens 2, a relatively low spatial frequency f is set.

  Thereafter, the control unit 10 calculates the inclination of the meridional image plane (M image plane) with respect to the optical axis L or a plane orthogonal to the optical axis L based on each of the four M-direction defocus characteristics calculated in step S3. At the same time, the inclination of the sagittal image plane (S image plane) with respect to the optical axis L or a plane orthogonal to the optical axis L is calculated based on each of the four S-direction defocus characteristics calculated in step S3 (step S4). ).

  That is, the control unit 10 calculates the inclination of the M image plane from the M-direction defocus characteristics at the positions of the first sensors 6 arranged at the four locations, and arranges the second sensors 7 arranged at the four locations. The inclination of the S image plane is calculated from the S direction defocus characteristics at each position. Specifically, as shown in FIG. 8, the control unit 10 determines the inclination of the M image plane and the S image plane based on the deviation ΔZ of the peak position of each defocus characteristic (that is, the most focused position). Is calculated. That is, the control unit 10 calculates the inclination of the M image plane based on the peak position shift ΔZ of the four M-direction defocus characteristics, and based on the peak position shift ΔZ of the four S-direction defocus characteristics. The inclination of the S image plane is calculated.

  Thereafter, the control unit 10 determines whether or not the inclination of the M image plane and the inclination of the S image plane calculated in step S4 satisfy a predetermined standard (step S5). For example, the control unit 10 determines whether or not the inclination of the M image plane and the inclination of the S image plane are equal to or less than a predetermined standard value, or the difference between the inclination of the M image plane and the inclination of the S image plane is a predetermined standard. It is determined whether or not it is less than or equal to the value.

  When the inclination of the M image plane and the inclination of the S image plane calculated in step S4 satisfy a predetermined standard, the MTF at a predetermined chart position (standard position) is calculated, and the calculated MTF is predetermined. It is determined whether or not the standard is satisfied (step S8). Specifically, at a predetermined chart position, the M direction MTF at each of the four sensor positions disposed at four positions and the second sensor 7 disposed at each of the four positions are disposed. The S direction MTF is calculated, and it is determined whether or not these MTFs satisfy a predetermined standard. When the MTF satisfies a predetermined standard, the adjustment lens 3 is fixed to the lens barrel 15 by adhesion or the like, and the lens holding member 16 is removed from the lens moving mechanism 9 to align the lens 2. Ends. If the MTF does not satisfy a predetermined standard, the lens 2 is determined to be defective. Therefore, for example, the adjustment lens 3 is not fixed to the lens barrel 15, the lens holding member 16 is removed from the lens moving mechanism 9, and the alignment of the lens 2 is completed.

  On the other hand, when the inclination of the M image plane calculated in step S4 and the inclination of the S image plane do not satisfy a predetermined standard, the control unit 10 determines the inclination of the M image plane calculated in step S4 and the S image plane. Based on the inclination of the image plane, the adjustment amount of the adjustment lens 3 is calculated (step S6). Specifically, the control unit 10 calculates the adjustment amount of the adjustment lens 3 in the X direction and the Y direction so that the inclination of the M image plane and the inclination of the S image plane satisfy predetermined standards.

  In step S6, for example, as shown in FIG. 9A, the control unit 10 adjusts the adjustment lens 3 so that the inclination θ1 of the M image plane and the inclination θ2 of the S image plane substantially coincide with each other. Is calculated. Alternatively, as shown in FIG. 9B, the control unit 10 calculates the adjustment amount of the adjustment lens 3 so that the inclination θ1 of the M image plane and the inclination θ2 of the S image plane become small with a good balance. That is, as shown in FIG. 9C, the control unit 10 adjusts the adjustment amount R1 of the adjustment lens 3 in which the inclination θ1 of the adjusted M image plane and the inclination θ2 of the S image plane substantially coincide, or M An adjustment amount R2 of the adjustment lens 3 is calculated in which the inclination θ1 of the image plane and the inclination θ2 of the S image plane are reduced in a balanced manner. That is, for example, the control unit 10 calculates the adjustment amount of the adjustment lens 3 such that the absolute value of the inclination θ1 of the M image plane and the absolute value of the inclination θ2 of the S image plane are substantially equal.

  Thereafter, the control unit 10 drives the lens moving mechanism 9 based on the adjustment amount of the adjustment lens 3 calculated in step S6 to move the adjustment lens 3 in the X direction and / or the Y direction (step). S7). In step S7, for example, the inclination θ1 of the M image plane and the inclination θ2 of the S image plane substantially coincide with each other, or the inclination θ1 of the M image plane and the inclination θ2 of the S image plane become small in a balanced manner. Then, the adjustment lens 3 is moved in the X direction and / or the Y direction. That is, in step S7, for example, the adjustment lens 3 is moved so that the absolute value of the inclination θ1 of the M image plane and the absolute value of the inclination θ2 of the S image plane are substantially equal.

  After that, returning to step S1, the control unit 10 again calculates the M direction MTF and the S direction MTF, the M direction defocus characteristic, and the S direction defocus characteristic, and the inclination of the M image plane and the S image plane. To determine whether the calculated inclination of the M image plane and the calculated inclination of the S image plane satisfy a predetermined standard.

  Note that step S1 in this embodiment is an MTF calculation step for calculating the M direction MTF and the S direction MTF, and step S3 is a defocus characteristic calculation step for calculating the M direction defocus characteristic and the S direction defocus characteristic. It is. Step S4 is an image plane inclination calculation step for calculating the inclination of the meridional image plane and the inclination of the sagittal image plane, and step S6 is a lens adjustment amount calculation step for calculating the adjustment amount of the adjustment lens 3. Step S7 is a lens adjustment step for moving the adjustment lens 3 based on the adjustment amount of the adjustment lens 3.

(Main effects of this form)
As described above, in this embodiment, the lens alignment device 1 includes the chart 5, the four first sensors 6, the four second sensors 7, and the chart driving mechanism 8, and in step S1, the M direction. MTF and S direction MTF are calculated, M direction defocus characteristic and S direction defocus characteristic are calculated in step S3, M image plane inclination and S image plane inclination are calculated in step S4, and M image is calculated in step S6. The adjustment amount of the adjustment lens 3 is calculated based on the inclination of the surface and the inclination of the S image plane. Therefore, in the present embodiment, it is not necessary to calculate the adjustment amount of the adjustment lens 3 while rotating the chart 5 at a predetermined angular pitch. Compared with the lens alignment device described in Patent Document 1, the lens 2 is The alignment time can be shortened.

  In this embodiment, a predetermined pattern for obtaining the MTF of the lens 2 is formed on the chart 5. Therefore, the M direction defocus value and the S direction defocus value at various spatial frequencies can be calculated using the common chart 5. Therefore, it is not necessary to prepare a chart 5 having a different pattern or to set a chart 5 having a different pattern according to the characteristics required for the lens 2 to be aligned. As a result, in this embodiment, the configuration of the lens alignment device 1 can be simplified, and the setting operation of the chart 5 can be simplified.

  In particular, in this embodiment, a first edge pattern for obtaining the M direction MTF is formed by the small-diameter arc portion 5d of the first light transmission portion 5a of the chart 5, and the clockwise direction side of the second light transmission portion 5b of the chart 5 A second edge pattern for obtaining the S direction MTF is formed by the radial linear portion 5h. Therefore, for example, the pattern of the chart 5 formed on the first sensor 6 or the second sensor 7 is compared with the case where the M direction MTF or the S direction MTF is obtained using the slits or the like formed on the chart 5. Even if the focus of the image is blurred, the first sensor 6 and the second sensor 7 can appropriately detect the contrast.

  In this embodiment, two of the four first sensors 6 are arranged such that the longitudinal direction and the X direction are substantially parallel, and the remaining two first sensors 6 are The longitudinal direction and the Y direction are arranged substantially parallel to each other. Further, the four second sensors 7 are arranged such that the longitudinal direction thereof is inclined by approximately 45 ° with respect to the X direction and the Y direction. The lens moving mechanism 9 is configured to move the adjustment lens 3 in the X direction and the Y direction. For this reason, in this embodiment, the movement amount of the adjustment lens 3 can be calculated relatively easily based on the detection results of the four first sensors 6 and the four second sensors 7.

  In the present embodiment, for example, in step S6, the control unit 10 calculates the adjustment amount of the adjustment lens 3 such that the absolute value of the inclination θ1 of the M image plane and the absolute value of the inclination θ2 of the S image plane are substantially equal. In step S7, the adjustment lens 3 is moved so that the absolute value of the inclination θ1 of the M image plane is substantially equal to the absolute value of the inclination θ2 of the S image plane. In this case, it is possible to appropriately align the lens 2 in consideration of the balance between the inclination of the M image plane and the inclination of the S image plane.

  As shown in FIG. 9A, when the adjustment lens 3 is adjusted such that the inclination θ1 of the M image plane and the inclination θ2 of the S image plane substantially coincide, Is mounted on the camera or the like so that the inclination θ1 of the M image plane and the inclination θ2 of the S image plane substantially coincide with the inclination of the imaging surface of the imaging element. Further, as shown in FIG. 9B, when the adjustment lens 3 is adjusted so that the inclination θ1 of the M image plane and the inclination θ2 of the S image plane are reduced in a balanced manner, the lens after the alignment is performed. In a camera or the like on which 2 is mounted, for example, an imaging element is mounted on the camera or the like so that the imaging surface is orthogonal to the optical axis L.

(Other embodiments)
In the embodiment described above, the lens alignment device 1 includes the four first sensors 6 and the four second sensors 7, but the first sensor 6 and the second sensor 7 included in the lens alignment device 1. The number of may be three or more. That is, the lens alignment device 1 only needs to include three or more first sensors 6 and second sensors 7 so that the inclination of the M image plane and the inclination of the S image plane can be calculated.

  In the embodiment described above, the four first sensors 6 are arranged at a substantially 90 ° pitch with the optical axis L as the center, and the second sensors 7 are arranged at a substantially 90 ° pitch with the optical axis L as the center. Therefore, the lens alignment device 1 is not configured to be able to calculate the defocus characteristic of the lens 2 on the optical axis L. In addition to this, for example, the lens alignment device 1 may be configured to be able to calculate the defocus characteristic of the lens 2 on the optical axis L. That is, as shown in FIGS. 10 and 11, the third sensor (third sensor) 26 is arranged on the optical axis L, and the second sensor 26 is located near the center of the chart 5 so as to correspond to the third sensor 26. Three light transmission parts (third light transmission parts) 5k may be formed. In this case, the third sensor 26 is, for example, a line sensor, and is arranged so that the longitudinal direction thereof is substantially parallel to the X direction. Further, the third light transmission portion 5k is formed in a substantially rectangular shape having one side (edge) passing through the optical axis L and having four sides substantially parallel to the X direction or the Y direction.

  In this case, the inclination of the M image plane and the inclination of the S image plane are the positions where the defocus characteristics on the optical axis L calculated based on the contrast detected by the third sensor 26 are the best. It is preferable to adjust the adjustment lens 3 so as to substantially match. In this way, in a camera or the like on which the adjusted lens 2 is mounted, the focus adjustment is performed so that the focus on the optical axis L is the best, thereby minimizing variations in the M image plane and the S image plane. be able to.

  In the embodiment described above, the chart 5 is moved in the optical axis direction in order to calculate the defocus characteristic of the lens 2, but the lens 2 is moved in the optical axis direction in order to calculate the defocus characteristic of the lens 2. Alternatively, the first sensor 6 and the second sensor 7 may be moved in the optical axis direction. In addition, when calculating | requiring MTF using a back projection method, if the 1st sensor 6 and the 2nd sensor 7 are moved to an optical axis direction, since the movement amount of the 1st sensor 6 and the 2nd sensor 7 will become large, It is preferable to move the lens 2 or the chart 5 in the optical axis direction.

  In the embodiment described above, the lens moving mechanism 9 is configured to move the adjustment lens 3 in the X direction and the Y direction. However, the lens moving mechanism 9 moves the adjustment lens 3 in the Z direction. The adjustment lens 3 may be inclined with respect to the optical axis L.

DESCRIPTION OF SYMBOLS 1 Lens alignment apparatus 2 Lens 3 Lens for adjustment 4 Light source 5 Chart 5a 1st light transmission part (1st light transmission part)
5b Second light transmission part (second light transmission part)
5d small-diameter arc (first edge pattern)
5h Radial straight part (second edge pattern)
6 First sensor (first sensor)
7 Second sensor (second sensor)
8 Chart drive mechanism (optical axis direction drive mechanism)
DESCRIPTION OF SYMBOLS 10 Control part L Optical axis S1 MTF calculation step S3 Defocus characteristic calculation step S4 Image surface inclination calculation step S6 Lens adjustment amount calculation step S7 Lens adjustment step

Claims (9)

In a lens alignment apparatus that adjusts an adjustment lens among a plurality of lenses to align the lens,
A light source that emits light toward the lens;
A chart that is disposed between the lens and the light source, and on which a predetermined pattern for obtaining an MTF (Modulation Transfer Function) of the lens is formed;
A first sensor for detecting a contrast for obtaining an M direction MTF, which is an MTF of the lens in the meridional direction, arranged at three or more different positions in a direction orthogonal to the optical axis of the lens;
A second sensor that is disposed at three or more different positions in a direction orthogonal to the optical axis of the lens and detects a contrast for obtaining an S direction MTF that is an MTF of the lens in a sagittal direction;
An optical axis direction drive mechanism that changes the distance between the lens and the chart in the optical axis direction of the lens, or the distance between the first sensor and the second sensor, and the lens. Lens alignment device to do. A control unit for controlling the lens alignment device;
The controller changes the distance between the lens and the chart in the optical axis direction or the distance between the first sensor, the second sensor, and the lens by the optical axis direction driving mechanism. The M direction MTF is calculated based on the contrast detected by each of the first sensors, and the S direction MTF is calculated based on the contrast detected by each of the second sensors. An M-direction defocus characteristic that is a defocus characteristic of the lens at a specific spatial frequency is calculated based on each of the MTFs, and a defocus characteristic of the lens at the specific spatial frequency is calculated based on each of the S-direction MTFs. S direction defocus characteristic is calculated and each of the M direction defocus characteristics is calculated. And calculating the inclination of the meridional image plane with respect to the optical axis or a plane orthogonal to the optical axis and the sagittal image plane with respect to the optical axis or the plane orthogonal to the optical axis based on each of the S-direction defocus characteristics. 2. The lens alignment device according to claim 1, wherein an adjustment amount of the adjustment lens is calculated based on an inclination of the meridional image plane and an inclination of the sagittal image plane. The first sensors are arranged at four positions with a pitch of about 90 ° around the optical axis,
The second sensors are arranged at four positions with a pitch of about 90 ° around the optical axis,
The first sensor and the second sensor are arranged on substantially the same plane orthogonal to the optical axis so as to be shifted by approximately 45 ° about the optical axis. The lens aligning device according to 1 or 2. The chart includes three or more first light transmission portions for obtaining the M direction MTF and three or more second light transmission portions for obtaining the S direction MTF,
The predetermined pattern is a first edge pattern formed by an edge of the first light transmission portion and a second edge pattern formed by an edge of the second light transmission portion. The lens aligning device according to claim 1, wherein A chart on which a predetermined pattern for obtaining the MTF of a plurality of lenses is formed, and M, which is the MTF of the lens in the meridional direction, are arranged at three or more different positions in the direction orthogonal to the optical axis of the lens. A first sensor for detecting the contrast for obtaining the direction MTF and three or more different positions in the direction orthogonal to the optical axis of the lens, and for obtaining the S direction MTF which is the MTF of the lens in the sagittal direction A second sensor for detecting the contrast of the lens, and a method for controlling a lens alignment device that adjusts an adjustment lens of the lenses and aligns the lens,
It is detected by each of the first sensors while changing the distance between the lens and the chart in the optical axis direction of the lens, or the distance between the first sensor, the second sensor, and the lens. An MTF calculating step of calculating the M direction MTF based on the contrast of the second sensor and calculating the S direction MTF based on the contrast detected by each of the second sensors;
Based on each of the M direction MTFs calculated in the MTF calculation step, an M direction defocus characteristic that is a defocus characteristic of the lens at a specific spatial frequency is calculated, and the S calculated in the MTF calculation step is calculated. A defocus characteristic calculating step of calculating an S direction defocus characteristic which is a defocus characteristic of the lens at the specific spatial frequency based on each of the directions MTF;
An inclination of the meridional image plane with respect to the optical axis or a plane orthogonal to the optical axis is calculated based on each of the M-direction defocus characteristics calculated in the defocus characteristic calculation step, and in the defocus characteristic calculation step An image plane inclination calculating step for calculating an inclination of a sagittal image plane with respect to the optical axis or a plane orthogonal to the optical axis based on each of the calculated S-direction defocus characteristics;
A lens adjustment amount calculating step of calculating an adjustment amount of the adjustment lens based on the inclination of the meridional image plane calculated in the image plane inclination calculating step and the inclination of the sagittal image plane. Control method of lens alignment device.   In the image plane inclination calculation step, the inclination of the meridional image plane is calculated based on the deviation of the respective peak values of the M direction defocus characteristic, and based on the deviation of the respective peak values of the S direction defocus characteristic. 6. The method of controlling a lens aligning device according to claim 5, wherein an inclination of the sagittal image plane is calculated. A lens adjustment step of moving the adjustment lens based on the adjustment amount of the adjustment lens calculated in the lens adjustment amount calculation step;
In the lens adjustment amount calculation step, an adjustment amount of the adjustment lens in a direction orthogonal to the optical axis is calculated,
The method for controlling a lens alignment device according to claim 5 or 6, wherein, in the lens adjustment step, the adjustment lens is moved in a direction orthogonal to the optical axis. The first sensors are arranged at four positions with a pitch of about 90 ° around the optical axis,
The second sensors are arranged at four positions with a pitch of about 90 ° around the optical axis,
The first sensor and the second sensor are arranged on substantially the same plane orthogonal to the optical axis so as to be shifted by approximately 45 ° about the optical axis. 8. A method for controlling a lens aligning device according to item 7. A lens adjustment step of moving the adjustment lens based on the adjustment amount of the adjustment lens calculated in the lens adjustment amount calculation step;
In the lens adjustment amount calculating step, an adjustment amount of the adjustment lens is set such that an absolute value of the inclination of the meridional image plane with respect to the optical axis is substantially equal to an absolute value of the inclination of the sagittal image plane with respect to the optical axis. Calculate
In the lens adjustment step, the adjustment lens is moved so that the absolute value of the inclination of the meridional image plane with respect to the optical axis is substantially equal to the absolute value of the inclination of the sagittal image plane with respect to the optical axis. A method for controlling a lens alignment device according to claim 5.

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