JP2005024910A - Combination lens adjusting method and its device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a combination lens adjusting method and device that can precisely adjust the position even for a lens of a small NA. <P>SOLUTION: Four light beams obtained by diffracting and branching the coherent parallel light are condensed by using a reference lens 20 and the lens 23 under adjustment and diffracted to interfere each other to obtain each interference pattern. Two aberrations are detected with enough sensitivity for the decentering and tilting of the lens 23 from the four interference patterns. The first and the second aberrations are detected at the position where the lens 23 is displaced for the prescribed amount. The relation of the change of the aberration to the displacement of the lens 23 is obtained on the basis of the detected result of the aberration. By calculating the position where the amount of aberrations becomes equal for each of the first and the second light, and the position where the amount of aberrations becomes equal for each of the third and the fourth light becomes equal, the position of the lens 23 is adjusted on the basis of the amount of decentering and tilting calculated from the amount of displacements of the two calculated aberrations. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an adjustment method and an apparatus for assembling a combined lens used as an optical system of a digital still camera, for example.
[0002]
[Prior art]
Conventionally, an optical system that accurately irradiates a target position with light emitted from a light source is required, and such an optical system is not set to change the shape of a single lens, It is known that a so-called “assembled lens” in which a plurality of lenses are combined and handled as a single lens is easier to achieve. However, the combined lens cannot obtain desired characteristics unless the relative positional relationship of the plurality of lenses is adjusted accurately.
[0003]
2. Description of the Related Art Conventionally, as a group lens adjusting device used for lens position adjustment when assembling the above-described group lens, one having a configuration as shown in FIG. 14 is known (for example, see Patent Document 1). FIG. 1 illustrates a combined lens adjusting device used when assembling a combined lens that is an optical lens for reading and writing information on an optical disk type information recording medium. Light emitted from the light source 1 is converted into parallel light by the collimator lens 2 and then sequentially transmitted through the two adjusted lenses 4 and 7 fixed to the lens barrel 3, thereby collecting on the transmission type diffraction grating 8. To be lighted. The light that has passed through the diffraction grating 8 is incident on the collimating lens 9 while spreading, then passes through the collimating lens 9 to become parallel light, and is further condensed by the condensing lens 10, and the pupil of the condensing lens 10. The surface is received by the image receiving element (imaging element) 11.
[0004]
In the group lens adjusting device, the light is diffracted by the transmissive diffraction grating 8, so that the light transmitted through the diffraction grating 8 is zero-order diffracted light L as shown in FIG. ₀ ± 1st order diffracted light + L ₁ , -L ₁ , ± 2nd order diffracted light (not shown),... At this time, the light incident on the diffraction grating 8 while being narrowed by an angle (incidence diaphragm angle of light with respect to the diffraction grating 8) φ generates ± 0th order diffracted light having a spread of an emission angle (diffraction angle) θ. ± 1st order diffracted light + L ₁ , -L ₂ As is well known, the emission angle θ is given by the following equation (1) from the diffraction grating pitch p and the wavelength λ.
[0005]
p = λ / sin (θ) (1)
Accordingly, if the emission angle θ is appropriately selected, as shown in FIG. 15, ± first-order diffracted light + L ₁ , -L ₂ The outlines of the zero-order diffracted light L ₀ And + 1st order diffracted light + L ₁ Or 0th-order diffracted light L ₀ And -1st order diffracted light -L ₂ Overlap each other. These overlapped lights form interference fringes on the pupil plane of the condenser lens 10 in FIG. 14, and the interference fringes are imaged on the image receiving element 11. The processing device 12 shown in FIG. 14 detects the aberration of the light incident on the pupil plane of the condenser lens 10 based on the interference fringes received by the image receiving element 11.
[0006]
The interference fringes received by the image receiving element 11 appear in various patterns depending on the aberrations contained in the lenses to be adjusted 4 and 7, but the adjusting device for the lens assembly described above can obtain interference fringes when the aberration is zero. It is intended to adjust the relative position of the adjusted lenses 4 and 7 so as to be adjusted. Examples of the positional deviation of the lenses 4 and 7 to be adjusted include a deviation in the optical axis direction, a deviation in a specific direction orthogonal to the optical axis, and a deviation in a direction orthogonal to both the optical axis and the specific direction. The generated aberration differs depending on the type of positional deviation of the adjusted lenses 4 and 7. Which aberration is caused by which positional deviation depends on the design of the lenses 4 and 7 to be adjusted. In other words, it is possible to detect each aberration from the interference fringes and correct the corresponding positional deviation.
[0007]
In order to detect each aberration from the interference fringes with high accuracy, a generally known fringe scanning method can be suitably used. Specifically, as shown in FIG. 14, for example, by using a fine movement stage 13 which is a piezo-type moving mechanism using a piezo element, the diffraction grating 8 includes a component orthogonal to or perpendicular to the grating direction. When moved in the direction, each light intensity in the interference region changes in a sinusoidal shape. Considering a state where there is no aberration and there is no pattern in the interference region, the light intensity changes uniformly at all points in the interference region. In other words, there is no phase difference in each light intensity change between one point and another point. Conversely, if there is a phase difference at any two points in the interference region, this means that there is any aberration in the adjusted lenses 4 and 7.
[0008]
If the phase difference is ignored and only the light intensity is focused, if there is unevenness in the intensity of the light incident on the adjusted lenses 4 and 7, the aberration is not affected by the adjusted lenses 4 and 7. May be mistakenly recognized as being present. On the other hand, in the case of the fringe scanning method, aberration detection with high accuracy can be performed based on the phase difference without being affected by unevenness of the light intensity.
[0009]
Therefore, the processing device 12 moves the diffraction grating 8 via the fine movement stage 13, obtains the phase of the light intensity at a plurality of points on a certain reference line set in the interference region, and based on the phase difference between them. Find the corresponding aberration. Each aberration detected in this way by the processing device 12 is sent to the control device 14, and the control device 14 drives and controls the movement adjusting means 17 based on each aberration, so that it is transmitted via the lens holder 18. The position of the lens 7 to be adjusted held by the lens is adjusted.
[0010]
[Patent Document 1]
JP 2002-202450 A
[0011]
[Problems to be solved by the invention]
However, the conventional group lens adjustment method can be suitably used for position adjustment of a lens having a relatively large NA, for example, an objective lens for picking up an optical disk, but a lens having a small NA, for example, a digital still camera. When this is applied to the position adjustment of the assembled lens constituting the optical system, there is a problem that high-accuracy position adjustment cannot be performed because the amount of fluctuation of a specific aberration, for example, astigmatism, with respect to the decentering of the lens is small. .
[0012]
In addition, optical disc pickups use on-axis light to read and write to a recording medium such as a disc, whereas digital still cameras use off-axis light. It is not possible to guarantee the characteristics with respect to light having a high angle of view outside. Furthermore, in the conventional group lens adjustment method, since the value obtained by combining the decenter and tilt of the lens to be adjusted is detected as an aberration, the tilt and decenter cannot be separated.
[0013]
Accordingly, the present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a group lens adjustment method and a group lens adjustment device that can highly accurately adjust the position of a lens having a small NA. To do.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, a group lens adjustment method according to a first aspect of the present invention is a group lens adjustment method for adjusting the position of a lens to be adjusted using the optical axis of a reference lens as a reference optical axis, and a coherent parallelism. First light and second light having a predetermined angle of inclination in the + and − directions with respect to the reference optical axis on the first plane including the reference optical axis, and the first plane On the second plane including the reference optical axis, and a total of four lights including third and third lights each having an inclination of a predetermined angle in the + direction and the − direction with respect to the reference optical axis. A step of branching and condensing the four lights by the reference lens and the lens to be adjusted, a step of diffracting and interfering the collected four lights, respectively, and interference of the four lights, respectively. Interference fringes are formed on the pupil plane of two objective lenses, and 4 The first and second aberrations among the aberrations having sufficient sensitivity to the decenter and tilt of the lens to be adjusted are detected from the four interference fringes received, respectively. Changing the position of the lens to be adjusted by a predetermined amount on a plane having the reference optical axis as a normal line, and detecting the first and second aberrations at the changed position; Based on the detection results of the first and second aberrations, the relationship between the change amount of aberration with respect to the change in position of the adjusted lens and the relationship between change amount of aberration with respect to the obtained change in the position of the adjusted lens On the basis of this, the position where the aberration amount for the first light and the aberration amount for the second light are equal, and the position where the aberration amount for the third light and the aberration amount for the fourth light are equal, respectively. Yo A step of calculating the second aberration, a step of individually calculating a decenter amount and a tilt amount of the lens to be adjusted from the calculated first aberration and the positional deviation amount of the second aberration, and the calculated decenter amount. And a step of adjusting the position of the lens to be adjusted based on the tilt amount.
[0015]
In this group lens adjustment method, since the light has an inclination of a predetermined angle with respect to the reference optical axis, the amount of change in aberration becomes larger than that for light on the axis, that is, light with an incident angle of 0 degrees, and the aberration Since the intersection of symmetrical positions can be detected with high accuracy, even a lens with a large MTF degradation for light with a large angle of view, such as a digital still camera lens, can be positioned without any problem, and the reference lens and the target can be adjusted. Even if a lens with a large NA is used, the decenter amount and tilt amount of the lens to be adjusted can be detected independently and with high accuracy, so that the position of the lens to be adjusted can be adjusted very accurately. Can do.
[0016]
The group lens adjustment device according to claim 2 of the present invention is a group lens adjustment device that adjusts the position of the lens to be adjusted with the optical axis of the reference lens as the reference optical axis, and a light source that emits coherent parallel light; The first light and the second light each having a predetermined angle of inclination in the + direction and the − direction with respect to the reference optical axis on the first plane including the reference optical axis, and the first light, A total of four third and third lights each having a predetermined angle of inclination in the + direction and the − direction with respect to the reference optical axis on a second plane including the reference optical axis. A first diffraction grating that diverges into light; a moving means that moves the lens to be adjusted on a plane with the reference optical axis as a normal; and the four lights are condensed by the reference lens and the lens to be adjusted. A second diffraction grating for diffracting light, and the second diffraction case Is moved in a direction including the component perpendicular to the groove direction in the lattice plane, and interference light on the pupil plane of the objective lens is imaged on the image receiving element by the imaging lens, and the interference image is obtained. Interference image observation system for observing the image, and processing for detecting two aberrations among aberrations having sensitivity to decenter and tilt of the lens to be adjusted by processing the interference images of the four interference image observation systems And a control device that drives and controls the moving means based on an adjustment amount calculated based on the detected aberration of the processing device.
[0017]
In this group lens adjusting device, a first diffraction grating that divides parallel light into four lights, a moving means that moves the lens to be adjusted, and a second diffraction grating that diffracts the light collected by the four lights, , A fine movement stage for displacing the second diffraction grating, four interference image observation systems for observing the interference image, and processing the interference image to detect two aberrations sensitive to the decenter and tilt of the lens to be adjusted And a control device that drives and controls the moving means based on the adjustment amount calculated based on the detected aberration of the processing device, so that the combined lens adjustment method according to claim 1 is faithfully embodied and adjusted. The same effect as the method can be reliably obtained.
[0018]
The group lens adjustment method according to claim 3 of the present invention is a group lens adjustment method for adjusting the position of the lens to be adjusted with the optical axis of the reference lens as the reference optical axis, and the coherent first wavelength optical axis and A step of condensing first parallel light that is parallel by the reference lens and the adjusted lens, a step of diffracting and interfering the collected light, and interference on the pupil plane of the objective lens by the interference light Forming a fringe and forming an image on the first image-receiving element; and detecting one of the aberrations having sufficient sensitivity to the decenter of the lens to be adjusted from the formed interference image And changing the position of the lens to be adjusted by a predetermined amount on a plane having the reference optical axis as a normal, and detecting the aberration at the changed position, and based on the detection result of the aberration, Aberration with respect to change in position of lens to be adjusted A step of obtaining the relationship of the conversion, a step of calculating the position of the lens to be adjusted at which the aberration becomes zero from the obtained relationship, and forming an image of the second light having the second wavelength, and then forming the image Adjusting the position so as to substantially coincide with the position of the center of curvature of the surface of the lens to be adjusted, and entering the lens to the lens to be adjusted; and reflecting the second light reflected from the lens to be adjusted by the second light. An image is formed on an image element to detect the center of curvature of the surface of the lens to be adjusted, and the imaging position of the second light is substantially coincident with the center of curvature of the back surface of the lens to be adjusted. Adjusting, and imaging the reflected light of the second light from the back surface of the lens to be adjusted onto the second image receiving element to detect the center of curvature of the back surface of the lens to be adjusted; From the center positions of curvature of the detected front and back surfaces of the adjusted lens Calculating a tilt amount of the adjusting lens, characterized in that it has a step of said adjusting the position of the adjusting lens on the basis of the aberration zero position and the tilt amount of the object to be adjusted lens the calculated.
[0019]
Also in this group lens adjustment method, similarly to the first aspect of the invention, even with an adjusted lens having a small NA, the decenter amount and the tilt amount can be detected independently and with high accuracy. The position can be adjusted accurately.
[0020]
A group lens adjusting device according to a fourth aspect of the present invention is a group lens adjusting device that adjusts the position of a lens to be adjusted using the optical axis of the reference lens as the reference optical axis. A first light source that emits light, displacement means that displaces the lens to be adjusted in two axial directions orthogonal to each other on a plane having the reference optical axis as a normal line, and condensed light from the reference lens and the lens to be adjusted. A diffraction grating that diffracts and interferes, a fine movement stage that displaces the diffraction grating in a direction including a component perpendicular to the groove direction in the grating plane, and interference light on the pupil plane of the objective lens An interference image observation system that forms an image on the first image receiving element with the image forming lens and observes interference fringes, and processes the interference image of the interference image observation system so as to be sensitive to the decenter of the lens to be adjusted. For detecting one of the aberrations having An apparatus, a second light source that emits second light having a second wavelength, a collimating lens that forms an image of the second light on the center of curvature of the front or back surface of the lens to be adjusted, An image lens, a first half mirror, a moving means for moving the collimating lens in the optical axis direction thereof, a second half mirror for observing reflected light from the front or back surface of the lens to be adjusted, and a second An image receiving element and a control device for driving the adjusting means based on the adjustment amount calculated from the detected aberration and the reflected light position are provided.
[0021]
In this group lens adjusting device, the group lens adjusting method according to claim 3 can be faithfully realized, and the same effect as that of the adjusting method can be reliably obtained.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a schematic configuration of a group lens adjusting device that embodies the group lens adjusting method according to the first embodiment of the present invention. In this group lens adjusting device, the optical axis of the reference lens 20 fixed to the lens barrel 19 is used as the reference optical axis (that is, the Z axis) of the device. The coherent parallel light emitted from the light source 21 is incident on the first plane including the optical axis (XZ plane in the figure) by the first diffraction grating 22 at a predetermined angle on the + direction side with respect to the reference optical axis. The first light having an inclination of (+ ψ1 degree), the second light having an inclination of a predetermined angle (−ψ1 degree) on the − direction side with respect to the reference optical axis, and the first axis Third light having a predetermined angle (+ ψ2 degrees) on the + direction side with respect to the optical axis on a second plane (YZ plane in the figure) orthogonal to the plane, and on the − direction side with respect to the reference optical axis The light is branched into four lights together with the fourth light having an inclination of a predetermined angle (−ψ2 degrees).
[0023]
2A and 2B show an example of the first diffraction grating 22. FIG. 2A is an enlarged perspective view, FIG. 2B is a sectional view in the X-axis direction, and FIG. 2C is a sectional view in the Y-axis direction. The four lights branched by the first diffraction grating 22 pass through the reference lens 20 and then enter the adjusted lens 23. The four lights transmitted through the lens 23 to be adjusted are condensed on the second diffraction grating 24 by the lenses 20 and 23, respectively.
[0024]
FIG. 3 is an enlarged plan view showing an example of the shape of the second diffraction grating 24. The second diffraction grating 24 is arranged so that the normal line at the center 24a thereof substantially coincides with the reference optical axis. The light transmitted through the second diffraction grating 24 is diffracted. Therefore, by appropriately selecting the diffraction grating pitch p with respect to the light collection angle φ and wavelength λ with respect to the second diffraction grating 24, the 0th order diffracted light and the + 1st order diffracted light, or the 0th order diffracted light and the −1st order diffracted light. Overlap. The overlapped light has a first interference image observation system 27 and a second interference image observation system 28 whose centers are substantially located on the first plane, and a second center whose center is substantially located on the second plane. The third interference image observation system 29 and the fourth interference image observation system 30 are respectively observed.
[0025]
The first to fourth interference image observation systems 27 to 30 have the same basic configuration, but FIG. 4 shows the first interference image observation system on behalf of the interference image observation systems 27 to 30. A schematic diagram of the system 27 is illustrated. The interference image observation system 27 includes an objective lens 31, an imaging lens 32, and a CCD camera (image receiving element) 33. The light diffracted through the second diffraction grating 24 forms interference fringes on the pupil plane of the objective lens 31, and the interference fringes are imaged on the image receiving element of the CCD camera 33 by the imaging lens 32. Is done.
[0026]
Returning to FIG. 1, the processing device 34 detects aberration based on the interference fringes imaged on the image receiving element of the CCD camera 33. Here, the aberration detected by the processing device 34 is two aberrations having sufficient sensitivity to the decenter of the lens 23 to be adjusted and having a difference in sensitivity to tilt, for example, astigmatism and coma aberration. It is.
[0027]
As described above, the fringe scanning method is preferably used for detecting the aberration. That is, the fine diffraction stage 37, which is a piezo-type moving mechanism using a piezo element, is used to place the second diffraction grating 24 in a direction orthogonal to the grating direction or a direction including the orthogonal component (for example, the example shown in FIG. In the direction B or C), the light intensity in the interference region changes in a sine wave shape, and the aberration can be detected with high accuracy based on the phase difference without being affected by the unevenness of the light intensity. Then, the processing device 34 drives and controls the fine movement stage 37 to move the second diffraction grating 24 to obtain a plurality of light intensity phases on a certain reference line set in the interference region, The corresponding aberration is determined based on the phase difference.
[0028]
Next, a method for adjusting the position of the adjusted lens 23 with respect to the reference optical axis using the optical axis of the reference lens 20 as a reference optical axis will be described with reference to the flowchart of FIG. First, the reference lens 20 held by the lens barrel 19 is fixed by the lens barrel holder 38 (step S1), and the adjusted lens 23 is held by the lens holder 39 (step S2). Subsequently, the control device 41 in FIG. 1 drives and controls the adjusting device 40 with the parallel movement mechanism to move the adjusted lens 23 to the first measurement point via the lens holder 39 (step S3). In this state, the light source 21 is caused to emit light, and the processing device 34 measures the two aberrations of the adjusted lens 23 at the first measurement point (step S4). Further, the control device 41 drives and controls the adjusting device 40 with a parallel movement mechanism, and finely moves the lens 23 to be adjusted along the YX plane by a predetermined amount along the YX plane in the straight line X = Y direction, that is, the 45 degree direction. As a result, the adjusted lens 23 is moved to the second measurement point (step S5), and then the two aberrations of the adjusted lens 23 at the second measurement point are again measured by the processing device 34 (step S6). .
[0029]
The control device 41 obtains a graph (characteristic diagram) showing the relationship between the aberration change amount and the positional change of the lens to be adjusted for the two aberrations from the measurement results of the processing device 34 at the first and second measurement points. (Step S7). A control process for obtaining the relationship between the change amount of the aberration and the change in the position of the lens to be adjusted will be described with reference to FIGS.
[0030]
6A and 6B show the first plane (XZ plane) measured by the first interference image observation system 27 and the second interference image observation system 28 with respect to the position change of the lens 23 to be adjusted in the X direction. FIG. 6 is a characteristic diagram showing changes in the amount of aberration, where C1 shows the aberration measured by the first interference image observation system 27, and C2 shows the aberration measured by the second interference image observation system 28, respectively. FIG. 7 shows each of the above-described second planes (YZ planes) measured by the third interference image observation system 29 and the fourth interference image observation system 30 with respect to the position change of the lens 23 to be adjusted in the X direction. FIG. 6 is a characteristic diagram showing the change in the amount of aberration, in which C3 shows the aberration measured by the third interference image observation system 29, and C4 shows the aberration measured by the second interference image observation system 30, respectively.
[0031]
As shown in FIG. 7, the second plane (YZ plane) measured by the third interference image observation system 29 and the fourth interference image observation system 30 with respect to the movement of the lens to be adjusted 23 in the X direction. The amount of aberration above hardly changes. On the other hand, as shown in FIG. 6, the aberration on the first plane (XZ plane) measured by the first interference image observation system 27 increases with the movement of the adjusted lens 23 in the X direction, and The aberration on the first plane (XZ plane) measured by the second interference image observation system 28 decreases, and its intersection is an aberration symmetric position where the two aberrations are equal. This is the position where the optical axis and the optical axis of the lens to be adjusted 23 coincide.
[0032]
Similarly, when the lens 23 to be adjusted is moved in the Y direction, aberrations on the second plane (YZ plane) measured by the third interference image observation system 29 and the fourth interference image observation system 30 respectively. The amount changes in the same manner as in the characteristic diagram of FIG. 6, and the aberration symmetry position is obtained. On the other hand, for the movement of the adjusted lens 23 in the Y direction, the amount of aberration on the first plane (XZ plane) measured by the first interference image observation system 27 and the second interference image observation system 28 is as follows. As in the characteristic diagram of FIG.
[0033]
Therefore, when the aberration is measured while moving the lens 23 to be adjusted linearly along the 45 degree direction (straight line X = Y direction) on the XY plane by the adjusting device 40 with the parallel movement mechanism, the X direction and the Y direction are shown in FIG. Since a graph like the characteristic diagram can be drawn, it is possible to obtain the intersections at which the respective aberrations are symmetrical. Usually, in the case of a lens or a lens group for a digital still camera, degradation of MTF (lens evaluation index) with respect to light with a large angle of view is large and affects the characteristics. However, in the group lens adjustment device of this embodiment, Since the light has an angle of ± ψ1 ° or ± ψ2 ° with respect to the optical axis as described above, the amount of change in aberration becomes larger than that for light on the axis, that is, light with an incident angle of 0 °, Intersections of aberration symmetry positions can be detected with high accuracy.
[0034]
Here, when the adjusted lens 23 has a tilt, the adjusted lens 23 is linearly moved by a predetermined amount along the direction of 45 degrees (X = Y) on the XY plane, and the first measurement point and When the two aberrations are detected at the second measurement point, a graph as shown in FIG. 8 can be drawn in the X direction and the Y direction. In the figure, C5 is astigmatism measured by the first and third interference image observation systems 27 and 29, C6 is astigmatism measured by the second and fourth interference image observation systems 28 and 30, and C7 is the first astigmatism. Coma measured by the first and third interference image observation systems 27 and 29, C8 measured by the second and fourth interference image observation systems 28 and 30, P1 an astigmatism intersection point, and P2 a coma aberration. Each intersection is shown. When the adjusted lens 23 has a tilt, for example, coma has a higher sensitivity to tilt than astigmatism. Therefore, as clearly shown in FIG. A positional shift amount (tilt amount) indicated by G1 occurs between the aberration symmetrical positions P1 and P2. Therefore, the processing device 34 calculates a positional deviation amount G1 at the symmetrical position of the two aberrations in the X direction and the Y direction (step S8).
[0035]
FIG. 9 shows the position of the intersection of astigmatism and coma aberration with respect to the tilt amount of the lens to be adjusted 23, and the amount of deviation of the position of the intersection, C9 is the position of the point of astigmatism, and C10 is the coma aberration. G2 represents the position of the intersection point, and G2 represents the amount of deviation of the intersection point of astigmatism and coma aberration. The intersection position deviation amount G2 is a value determined with respect to the tilt amount of the lens 23 to be adjusted. Therefore, the processing device 34 calculates the tilt amount of the lens 23 to be adjusted by measuring the intersection position deviation amount G2, and at the same time calculates the intersection position, that is, the decenter amount when the tilt amount is zero (step S9). . From the tilt amount and the center position, a correction adjustment position from the center position of the lens to be adjusted 23 corresponding to the tilt amount can be obtained, and the obtained correction adjustment position is a position where the NTF is optimal. This arithmetic processing is executed by the processing device 34.
[0036]
The correction adjustment position data obtained by the processing device 34 is sent to the control device 41. The control device 41 drives and controls the adjustment device 40 with the parallel movement mechanism based on the input correction adjustment position data, and adjusts the lens to be adjusted. The relative position of the lens 23 to be adjusted with respect to the reference lens 20 is adjusted by moving 23 on the XY plane (step S10).
[0037]
As described above, in the group lens adjusting device of this embodiment, when adjusting the position of the lens 23 to be adjusted using the optical axis of the reference lens 20 as the reference optical axis, the coherent parallel light is converted into the first diffraction grating. 22, the first light having an inclination of + ψ1 degree with respect to the reference optical axis on the first plane (XZ plane) including the reference optical axis and the second light having an inclination of −ψ degree with respect to the reference optical axis. And a third light and a reference optical axis that are orthogonal to the second plane (YZ plane) and have an inclination of + ψ2 degrees with respect to the reference optical axis on the second plane (YZ plane) including the reference optical axis. On the other hand, after branching into a total of four lights with a fourth light having an inclination of −ψ2 degrees, a step of condensing the reference light by the reference lens 20 and the lens to be adjusted 23 and the four condensed lights are respectively second light. From the step of diffracting and interfering with the diffraction grating 24 and the interference of four lights Forming interference fringes on the pupil planes of the four objective lenses 31 respectively, forming images on the four image receiving elements 33 by the imaging lens 32, and decentering of the adjusted lens 23 from the four received interference fringes, respectively. The step of detecting the first and second aberrations among the aberrations having sufficient sensitivity to tilt, and the position of the lens 23 to be adjusted on a plane (XY plane) having the reference optical axis as a normal line Changing the predetermined amount, detecting the first and second aberrations at the changed positions, and changing the aberration with respect to the position change of the adjusted lens 23 based on the detection results of the first and second aberrations And a third position where the aberration amount for the first light and the aberration amount for the second light are equal to each other based on the step of determining the relationship of the amount, and the relationship of the amount of aberration change with respect to the determined position change of the adjusted lens 23. Against light A step of calculating for each of the first and second aberrations a position where the amount of aberration and the amount of aberration with respect to the fourth light are equal, respectively, and a lens to be adjusted from the calculated first and second aberrations The optical axis (reference optical axis) of the reference lens 20 is obtained through a step of individually calculating the decenter amount and tilt amount of 23 and a step of adjusting the position of the adjusted lens 23 based on the calculated decenter amount and tilt amount. Since the relative position of the lens 23 to be adjusted is adjusted, the decenter amount and the tilt amount of the lens 23 to be adjusted can be individually set even when the reference lens 20 and the lens 23 to be adjusted have a large NA. Since the detection can be performed independently with high accuracy, the position of the adjusted lens 23 can be adjusted extremely accurately.
[0038]
In the above embodiment, the aberration measurement for calculating the aberration symmetry position is performed at two measurement points on a 45-degree straight line on the XY plane by moving the lens 23 to be adjusted. If aberration measurement is performed at three or more measurement points on the 45-degree straight line, the accuracy is further improved. In the above embodiment, the decentering is adjusted according to the tilt amount of the lens 23 to be adjusted. However, if the adjusting device 40 with a parallel movement mechanism is provided with a rotation adjusting function, both decentering and tilting can be performed. It can also be adjusted.
[0039]
FIG. 10 is a schematic configuration diagram showing a group lens adjustment device that embodies the group lens adjustment method according to the second embodiment of the present invention. In FIG. 10, the same as or equivalent to FIG. A reference numeral is attached, and a duplicate description is omitted. Also in this group lens adjusting device, the optical axis of the reference lens 20 fixed to the lens barrel 19 is used as the reference optical axis (that is, the Z axis) of the device.
[0040]
The light having the first wavelength λ 1 emitted from the first light source 42 is converted into parallel light by the first collimating lens 43 and then enters the reference lens 20 and the adjusted lens 23. The light transmitted through the lenses 20 and 23 is collected on the diffraction grating 44 by the lenses 20 and 23. The light transmitted through the diffraction grating 44 is diffracted. By appropriately selecting the diffraction grating pitch with respect to the light collection angle φ and the wavelength λ with respect to the diffraction grating 44, the 0th-order diffracted light and the + 1st-order diffracted light, or the 0th-order diffracted light and the −1st-order diffracted light overlap. These overlapped lights form interference fringes on the pupil plane on the objective lens 47, and the interference fringes are imaged on the image receiving element of the first CCD camera 49 by the first imaging lens 48. Then, the processing device 34 detects aberration based on the received interference fringes.
[0041]
The detected aberration is one of aberrations having sufficient sensitivity with respect to the adjusted lens 23, for example, coma aberration. Then, the processing device 34 moves (finely moves) the diffraction grating 44 by the fine movement stage 37 that is a piezo type moving mechanism, and obtains the phase of the light intensity at a plurality of points on a certain reference line set in the interference region, Corresponding aberrations are obtained based on these phase differences.
[0042]
On the other hand, the light having the second wavelength λ 2 emitted from the second light source 50 is converted into parallel light by the second collimating lens 51, and further passes through the second imaging lens 52 and passes through the first half mirror 53. Then, the second imaging lens 52 forms an image at the imaging point F. The imaged light travels while spreading again and enters the reference lens 20 and the adjusted lens 23. Here, the second collimating lens 51 is moved by the moving means 54 in the optical axis direction of the collimating lens 51 so that the image formation point F substantially coincides with the center of curvature of the front surface or the back surface of the lens 23 to be adjusted. Adjusted to In this case, the light reflected by the front surface or the back surface of the lens 23 to be adjusted is condensed again at the imaging point F, returns along the same path as the incident light, is reflected by the second half mirror 57, and is reflected by the second image receiving element. An image is formed on the child 58. By observing this imaging position, the center positions of curvature of the front and back surfaces of the lens 23 to be adjusted can be obtained. Furthermore, the tilt amount of the lens 23 to be adjusted can be calculated from the center positions of curvature of the front and back surfaces.
[0043]
The light having the first wavelength λ1 is transmitted through the filter 59, and the light having the second wavelength λ2 is reflected by the filter 59. The filter 59 prevents the light having the second wavelength λ2 from entering the first CCD camera 49 and degrading the measurement accuracy.
[0044]
Next, a method for adjusting the position of the adjusted lens 23 with respect to the reference optical axis will be described with reference to the flowchart of FIG. First, the reference lens 20 fixed to the lens barrel is fixed by the lens barrel holder 38 (step S11), and the adjusted lens 23 is held by the lens holder 39 (step S12). Subsequently, the second light source 50 is caused to emit light, and the second collimating lens 51 is moved by the moving means 54 so that the imaging point F substantially coincides with the center of curvature of the surface of the lens 23 to be adjusted. The center of curvature of the surface of the lens 23 is measured (step S13). Further, the second collimating lens 51 is moved so that the imaging point F substantially coincides with the curvature center position of the back surface of the lens 23 to be adjusted, and the curvature center position of the back surface of the lens 23 to be adjusted is measured (step S14). ). Then, the tilt amount of the lens 23 to be adjusted is calculated from the center positions of curvature of the front and back surfaces (step S15).
[0045]
Subsequently, the lens 23 to be adjusted is moved to the first measurement point by the adjustment device 40 with the parallel movement mechanism (step S16), the first light source 42 is caused to emit light, and the aberration is measured by the processing device 34 (step). S17). Further, the adjusted lens 23 is moved by a predetermined amount along an angle of 45 degrees (straight line Y = X) on the XY plane by the adjusting device 40 with a parallel movement mechanism and then moved to the second measurement point (step S18). Then, the aberration is measured again by the processing device 34 (step S19). In this measurement, the change in coma aberration in the X direction when the lens 23 to be adjusted is moved in the X direction is shown in FIG. 12, and the change in coma aberration in the Y direction is shown in FIG. As the lens to be adjusted 23 moves in the X direction, the coma aberration in the Y direction hardly changes as shown in FIG. 13, whereas the coma aberration in the X direction changes as shown in FIG.
[0046]
When the adjusted lens 23 has no tilt, the coma aberration zero point position in the X direction matches the optical axis of the reference lens 20 (reference optical axis) and the optical axis of the adjusted lens 23 in the X direction. Similarly, when the lens 23 to be adjusted moves in the Y direction, the coma aberration in the Y direction changes as shown in FIG. 12, and the zero point position of the aberration is obtained, whereas the coma aberration in the X direction hardly changes. . Accordingly, the coma aberration in the X direction and the Y direction is measured as shown in FIG. 12 by measuring the aberration while moving the lens 23 to be adjusted along an angle of 45 degrees on the XY plane by the adjusting device 40 with the parallel movement mechanism. (Characteristic diagram) is acquired (step S20), and the respective aberration zero point positions are obtained (step S21).
[0047]
Here, the control device 41 calculates the optimum position of the lens 23 to be adjusted, for example, the optimum position of the MTF, according to the tilt amount obtained in the previous step, and thereby the adjustment position of the lens 23 to be adjusted is obtained. And the control apparatus 41 adjusts the position of the to-be-adjusted lens 23 by driving-controlling the adjustment apparatus 40 with a parallel displacement mechanism based on the calculated | required adjustment position, and moving the to-be-adjusted lens 23 on XY plane. (Step S22).
[0048]
As described above, in the second embodiment, when adjusting the position of the lens 23 to be adjusted using the optical axis of the reference lens 20 as a reference optical axis, it is parallel to the optical axis of the coherent first wavelength λ1. A step of condensing certain first parallel light by the reference lens and the lens to be adjusted, a step of diffracting the condensed light by the diffraction grating 44 and interfering with the interference fringes on the pupil plane of the objective lens 47 The step of forming an interference fringe and forming an image on the first image receiving element 49 by the first imaging lens 48 and sufficient sensitivity to decentering of the lens 23 to be adjusted from the formed interference image. A step of detecting one of the aberrations, a step of changing the position of the lens 23 to be adjusted by a predetermined amount on a plane whose normal is the reference optical axis, and detecting the aberration at the changed position; Based on the detection result of the aberration, A step of obtaining a relationship between the change in aberration with respect to a change in the position of the lens 23, a step of calculating the position of the lens 23 to be adjusted from which the aberration is zero based on the obtained relationship, and a second light of the second wavelength λ2. The second collimating lens 51 and the second imaging lens 52 are used to adjust the second collimating lens 51 so that its imaging position substantially coincides with the center of curvature of the surface of the lens 23 to be adjusted. The step of entering the lens 23 to be adjusted and the reflected light of the second light from the lens 23 to be adjusted is imaged on the second image receiving element 58 by the second imaging lens 52 and the second collimating lens 51. The step of detecting the center of curvature of the surface of the lens 23 to be adjusted and the second collimating lens 51 so that the imaging position of the second light substantially coincides with the position of the center of curvature of the back surface of the lens 23 to be adjusted. Adjust The reflected light of the second light from the back surface of the process and the lens to be adjusted 23 is imaged on the second image receiving element 58 by the second imaging lens 52 and the second collimating lens 51, and the lens to be adjusted 23 is adjusted. The step of detecting the center of curvature of the back surface of the lens, the step of calculating the tilt amount of the lens to be adjusted 23 from the detected center of curvature of the front and back surfaces of the lens to be adjusted 23, and the calculated aberration of the lens to be adjusted 23 Through the process of adjusting the position of the adjusted lens 23 based on the zero point position and the tilt amount, the decenter amount and the tilt amount can be detected independently and with high accuracy even for the adjusted lens 23 having a small NA. As a result, the position of the adjusted lens 23 can be adjusted accurately.
[0049]
In the second embodiment, aberration measurement for calculating the aberration zero point position is performed by moving the lens 23 to be adjusted along a straight line having an angle of 45 degrees on the XY plane. Although the measurement is performed at the measurement point, the detection accuracy is further improved if the measurement is performed at three or more measurement points on the straight line. Further, if the relationship between decenter and aberration is obtained in advance, the aberration zero point position can be calculated only by measurement at one measurement point on a straight line having an angle of 45 degrees on the XY plane. Furthermore, in the above embodiment, the decentering is adjusted according to the tilt amount of the lens 23 to be adjusted. However, if the adjusting device 40 with a parallel movement mechanism is provided with a rotation function, both decentering and tilting can be performed. Can be adjusted.
[0050]
【The invention's effect】
As described above, according to the group lens adjustment method of the present invention, since the light has an inclination of a predetermined angle with respect to the reference optical axis, the aberration is larger than that for light on the axis, that is, light with an incident angle of 0 degrees. Since the change amount of the aberration becomes large and the intersection of the symmetrical positions of the aberration can be detected with high accuracy, even a lens such as a digital still camera lens that has a large MTF degradation with respect to light with a large angle of view can be adjusted without any problem. In addition, even when a lens having a large NA is used as the reference lens and the lens to be adjusted, the decenter amount and the tilt amount of the lens to be adjusted can be detected independently and with high accuracy. The position can be adjusted very accurately.
[0051]
Further, according to the group lens adjusting device of the present invention, the first diffraction grating that divides the parallel light into the four lights, the moving means that moves the lens to be adjusted, and the light that collects the four lights are diffracted. The second diffraction grating, the fine movement stage for displacing the second diffraction grating, four interference image observation systems for observing the interference image, and processing the interference image to make the sensitivity to the decenter and tilt of the lens to be adjusted. And a control device that drives and controls the moving means based on the adjustment amount calculated based on the detected aberration of the processing device, so that the combined lens adjustment method according to the present invention is faithfully provided. It can be realized and the same effect as the adjustment method can be surely obtained.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a schematic configuration of a group lens adjustment device that embodies a group lens adjustment method according to a first embodiment of the present invention;
FIGS. 2A and 2B are examples of a first diffraction grating in the above-described group lens adjustment device, where FIG. 2A is an enlarged perspective view, FIG. 2B is an enlarged sectional view in an X-axis direction, and FIG. Sectional drawing.
FIG. 3 is an enlarged plan view showing an example of the shape of a second diffraction grating in the group lens adjusting apparatus same as above.
FIG. 4 is a schematic configuration diagram of the first interference image observation system in the above-described group lens adjustment device.
FIG. 5 is a flowchart showing control processing for adjusting the position of a lens to be adjusted according to the embodiment.
FIG. 6 shows two aberration amounts on the XZ plane respectively measured by the first interference image observation system and the second interference image observation system with respect to a change in the position of the lens to be adjusted in the X direction in the embodiment described above. The characteristic view which shows a change.
FIG. 7 shows two aberration amounts on the YZ plane respectively measured by the third interference image observation system and the fourth interference image observation system with respect to a change in the position of the adjusted lens in the X direction in the embodiment. The characteristic view which shows a change.
FIG. 8 is a characteristic diagram showing an aberration fluctuation amount with respect to a lens position fluctuation when there is a tilt in the embodiment.
FIG. 9 is a characteristic diagram showing a positional deviation amount of astigmatism and coma aberration with respect to a lens tilt amount in the embodiment;
FIG. 10 is a schematic configuration diagram showing a group lens adjustment device that embodies a group lens adjustment method according to a second embodiment of the present invention.
FIG. 11 is a flowchart showing a control process for adjusting the position of the lens to be adjusted according to the embodiment;
FIG. 12 is a characteristic diagram showing the amount of change in X-direction coma with respect to the change in position in the X direction of the lens to be adjusted according to the embodiment.
FIG. 13 is a characteristic diagram showing the amount of change in Y-direction coma with respect to the change in position in the X direction of the lens to be adjusted according to the embodiment.
FIG. 14 is a schematic configuration diagram showing a conventional group lens adjusting device.
FIG. 15 is an explanatory diagram of diffraction by a diffraction grating in the group lens adjustment apparatus same as above.
[Explanation of symbols]
20 Reference lens
21 Light source
22 First diffraction grating
23 Lens to be adjusted
24 Second diffraction grating
27-30 Interference image observation system
31 Objective lens
32 Imaging lens
34 Processing equipment
33 CCD camera (image sensor)
37 Fine movement stage
40 Adjustment device with parallel movement mechanism (moving means)
41 Control device
42 First light source
44 diffraction grating
47 Objective lens
48 First imaging lens
49 First image receiving element
50 Second light source
51 Second collimating lens
52 Second imaging lens
53 First half mirror
54 Moving means
57 Second half mirror
58 Second image receiving element

Claims (4)

A combined lens adjustment method that adjusts the position of the lens to be adjusted with the optical axis of the reference lens as the reference optical axis,
Coherent parallel light is converted into a first light and a second light each having a predetermined angle of inclination in a + direction and a − direction with respect to the reference optical axis on a first plane including the reference optical axis; A total of four third and third lights that are orthogonal to one plane and have a predetermined angle of inclination in the + and − directions with respect to the reference optical axis on a second plane including the reference optical axis. Branching into four lights, and collecting the four lights by the reference lens and the adjusted lens;
Diffracting and interfering each of the four condensed lights; and
Forming interference fringes on the pupil planes of the four objective lenses from the interference of the four lights, and forming images on the four image receiving elements;
Detecting first and second aberrations of aberrations having sufficient sensitivity to decenter and tilt of the lens to be adjusted from the received four interference fringes,
Changing the position of the lens to be adjusted by a predetermined amount on a plane having the reference optical axis as a normal line, and detecting the first and second aberrations at the changed position;
Obtaining a relationship of an amount of change in aberration with respect to a change in position of the lens to be adjusted based on detection results of the first and second aberrations;
Based on the obtained relationship of the amount of aberration change with respect to the position change of the adjusted lens, the position where the amount of aberration for the first light and the amount of aberration for the second light are equal, the amount of aberration for the third light, and the Calculating a position at which the amount of aberration for the fourth light is equal for each of the first and second aberrations;
Individually calculating a decenter amount and a tilt amount of the lens to be adjusted from the calculated displacement amounts of the first aberration and the second aberration;
Adjusting the position of the lens to be adjusted based on the calculated decenter amount and tilt amount. A lens assembly adjusting device that adjusts the position of the lens to be adjusted using the optical axis of the reference lens as the reference optical axis,
A light source that emits coherent parallel light;
The first light and the second light each having a predetermined angle of inclination in the + direction and the − direction with respect to the reference optical axis on the first plane including the reference optical axis, and the first light, A total of four third and third lights each having a predetermined angle of inclination in the + direction and the − direction with respect to the reference optical axis on a second plane including the reference optical axis. A first diffraction grating that branches into light;
Moving means for moving the lens to be adjusted on a plane whose normal is the reference optical axis;
A second diffraction grating that diffracts the light collected from the four lights by the reference lens and the adjusted lens;
A fine movement stage for displacing the second diffraction grating in a direction including a component in a direction perpendicular to the groove direction within the grating plane;
Four interference image observation systems for observing the interference image by forming the interference light on the pupil plane of the objective lens on the image receiving element by the imaging lens;
A processing device that processes interference images of the four interference image observation systems to detect two aberrations among aberrations having sensitivity to decenter and tilt of the lens to be adjusted;
And a control device that drives and controls the moving unit based on an adjustment amount calculated based on the detected aberration of the processing device. A combined lens adjustment method that adjusts the position of the lens to be adjusted with the optical axis of the reference lens as the reference optical axis,
Condensing first parallel light parallel to the optical axis of the coherent first wavelength with the reference lens and the adjusted lens;
Diffracting and interfering with the collected light; and
Forming interference fringes on the pupil plane of the objective lens by the interference light, and forming an image on the first image receiving element;
Detecting one of the aberrations having sufficient sensitivity to the decenter of the lens to be adjusted from the formed interference image;
Changing the position of the lens to be adjusted by a predetermined amount on a plane having the reference optical axis as a normal line, and detecting the aberration at the changed position;
Obtaining a relationship of an aberration change with respect to a position change of the lens to be adjusted based on the detection result of the aberration;
Calculating the position of the lens to be adjusted at which the aberration becomes zero from the obtained relationship;
After the second light of the second wavelength is imaged, adjusting the imaging position so that it substantially coincides with the center of curvature of the surface of the lens to be adjusted, and entering the lens to be adjusted;
Forming reflected light of the second light from the lens to be adjusted on a second image receiving element, and detecting the center of curvature of the surface of the lens to be adjusted;
Adjusting the imaging position of the second light so that it substantially coincides with the center of curvature of the back surface of the lens to be adjusted;
Imaging the reflected light of the second light from the back surface of the lens to be adjusted onto the second image receiving element to detect the center of curvature of the back surface of the lens to be adjusted;
Calculating a tilt amount of the lens to be adjusted from the center positions of curvature of the detected front and back surfaces of the lens to be adjusted;
Adjusting the position of the lens to be adjusted based on the calculated aberration zero point position and tilt amount of the lens to be adjusted. A lens assembly adjusting device that adjusts the position of the lens to be adjusted using the optical axis of the reference lens as the reference optical axis,
A first light source that emits coherent parallel light of a first wavelength;
Displacing means for displacing the lens to be adjusted in a biaxial direction orthogonal to a plane having the reference optical axis as a normal line;
A diffraction grating that diffracts and interferes with the condensed light from the reference lens and the lens to be adjusted;
A fine movement stage for displacing the diffraction grating in a direction including a component in a direction perpendicular to the groove direction within the grating plane;
An interference image observation system that forms interference light on the pupil plane of the objective lens on the first image receiving element by the first imaging lens and observes interference fringes;
A processing device that processes an interference image of the interference image observation system to detect one of the aberrations having sensitivity to the decenter of the lens to be adjusted;
A second light source that emits second light of a second wavelength;
A collimating lens that forms an image of the second light at the center of curvature of the front or back surface of the lens to be adjusted, a second imaging lens, and a first half mirror;
Moving means for moving the collimating lens in the optical axis direction thereof;
A second half mirror and a second image receiving element for observing reflected light from the front or back surface of the lens to be adjusted;
And a control device that drives the adjusting means based on the adjustment amount calculated from the detected aberration and the reflected light position.

Images