JP2004045327A - Instrument and method for measuring spot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an instrument that can easily and precisely measure the shape of a spot formed by means of a condenser lens etc., used for pickup devices. <P>SOLUTION: The observational light from a spot image formed by making the inspecting light from a laser light source 102 incident on an objective lens 101 to be inspected is reflected by a half mirror 51 through an objective lens 31, image forming lens 41, etc., and made incident on an alignment camera 54. Then centering is performed so that the spot of the observational light may be made incident on the center of the angle of view of the alignment camera 54 by moving an X-Y stage 21b installed on a supporting stage 21. Thereafter, the camera 54 is switched to a measuring camera 74 in image reading and centering is performed so that the spot image of the observational light may be made incident on the center of the angle of view of the camera 74 by again moving the X-Y stage 21b. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
【Technical field】
The present invention relates to a spot measuring device and a spot measuring method for enlarging and observing a spot image condensed by a test lens or the like.
[0002]
[Prior art]
In recent years, in order to increase the density of optical discs, an optical pickup using a light source wavelength of 405 mm and an objective lens of NA 0.85 and an objective lens used therefor have been developed.
[0003]
For optical pickup devices of optical recording / reproducing devices for recording or reproducing information on or from optical discs, and condensing lenses used therefor, the beam convergence characteristics due to this have become an important issue in pickup manufacturing and lens quality inspection. It is desired to precisely measure the spot shape.
[0004]
[Problems to be solved by the invention]
However, there is no device capable of simply and accurately measuring the spot shape of such an imaging lens.
[0005]
Therefore, an object of the present invention is to provide an apparatus for simply and precisely measuring a spot shape formed by a condenser lens or the like used in a pickup device.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problems, a spot measuring device according to the present invention includes an enlargement optical system that enlarges a spot image condensed by a subject and projects the spot image on an imaging surface, and a spot image projected on the imaging surface. The image capturing apparatus further includes: an enlarged image capturing unit that captures an image; a display unit that displays a spot image captured by the enlarged image capturing unit; and a light source for an autocollimator disposed at a position conjugate to the imaging surface. Here, the "display means" is not limited to a display for image display, but includes a printer, etc., and the display method of the "spot image" is not limited to an image. Graphs, numerical tables, and the like.
[0007]
In the spot measuring device, the inclination of the object such as a lens can be removed by the light source for the autocollimator, so that the light condensing state of the object can be accurately detected.
[0008]
In a specific aspect of the spot measuring instrument, the magnifying optical system includes a low-magnification projection optical system having an objective lens and an imaging lens, and a high-magnification projection optical system having a relay (magnification) lens. In this case, the alignment operation can be performed with the low-magnification projection optical system, and the observation of the spot image can be performed with the entire magnifying optical system.
[0009]
In a specific aspect of the spot measuring device, the light source for the autocollimator is disposed on an optical path branched by a branching mirror disposed between the low magnification projection optical system and the high magnification projection optical system. You. In this case, autocollimation using a low magnification projection optical system becomes possible.
[0010]
In a specific aspect of the spot measuring device, an alignment imaging unit that captures a spot image condensed by the test object at a low magnification on an optical path branched by the branching mirror is further provided. In this case, a system for autocollimation using a low magnification projection optical system can be simplified.
[0011]
In a specific aspect of the spot measuring device, when the inclination of the test object is corrected by operating the light source for the autocollimator, the objective lens is retracted from the optical path.
[0012]
In a specific aspect of the spot measuring instrument, the light source for the autocollimator includes a plurality of laser light sources that generate laser lights having different wavelengths. In this case, even if an anti-reflection film for a specific wavelength is formed on the test object, a sufficient amount of reflected light can be obtained from the test object by selecting the wavelength, so that the posture of the test object can be accurately determined. Can be controlled.
[0013]
In a specific aspect of the spot measuring instrument, the high-magnification projection optical system is movable in the optical axis direction. In this case, the convergence and divergence of the parallel light of the pickup excluding the objective lens can be determined. In addition, it is also possible to adjust the tilt when the test object has an R shape.
[0014]
The spot measuring method according to the present invention, in a specific aspect of the spot measuring device, is a spot measuring method for enlarging and projecting a spot image condensed by a test object onto an imaging surface. Photographing a spot image converged by an object with a low-magnification projection optical system including a first objective lens, and a test object based on the spot image photographed with the low-magnification projection optical system including the first objective lens A first centering step of centering the image, and measuring the spot image converged by the test object centered in the first centering step by adding a high-magnification projection optical system to the low-magnification projection optical system including the first objective lens. A step of taking an image with an optical system, and centering the test object based on a spot image taken with a measuring optical system in which a high-magnification projection optical system is added to the low-magnification projection optical system including the first objective lens. A second centering step, a step of photographing a spot image condensed by the test object centered in the second centering step with a high-magnification projection optical system including a second objective lens, and the second objective lens. A third centering step of centering the test object based on the spot image photographed by the low-magnification projection optical system; and a spot image condensed by the test object centered in the third centering step. Photographing with a measurement optical system in which a high-magnification projection optical system is added to a low-magnification projection optical system including a lens.
[0015]
In the above spot measurement method, since the centering is performed stepwise by utilizing the low magnification projection optical system and the high magnification projection optical system, the spot image formed by the test object is placed in the target observation field formed by the measurement optical system. It can be surely introduced.
[0016]
In a specific aspect of the spot measuring method, the magnification of a measurement optical system obtained by adding a high-magnification projection optical system to the low-magnification projection optical system including the first objective lens is adjusted to a low-magnification projection optical system including the second objective lens. It is lower than the magnification of the optical system.
[0017]
Further, in a specific aspect of the spot measuring method, an automatic focusing step is provided before and / or after each centering step. In this case, centering is assured.
[0018]
Further, in a specific mode of the spot measuring method, an automatic dimming step is provided before and / or after each centering step. In this case, centering is assured.
[0019]
In a specific aspect of the spot measuring method, the centering step includes a step of calculating a barycentric position or a peak intensity position of the captured spot image, and a stage that supports a test object, and an optical axis of the barycentric position. Driving by a corresponding amount that cancels the deviation from
[0020]
In a specific aspect of the spot measuring method, the automatic focusing step includes a step of experimentally driving the low-magnification projection optical system or the measurement optical system in advance to predict a focus direction.
[0021]
In a specific aspect of the spot measuring method, the step of photographing with a measuring optical system in which a high-magnification projection optical system is added to the low-magnification projection optical system including the second objective lens includes: Capturing a spot image converged by the test object while moving the target. In this case, the light-collecting characteristics of the test object can be detected stepwise along the optical axis direction, and the spot shape of the test object can be measured three-dimensionally.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a diagram illustrating an external structure of a spot measuring device according to an embodiment of the present invention. The spot measuring apparatus includes a support stage 21 fixed on the pedestal 11 and supporting the object 100 to be inspected including the lens to be inspected, a Z-axis coarse movement stage 23 attached to a column 13 extending from the pedestal 11 in the vertical direction. And an observation head 25 fixed to the Z-axis coarse movement stage 23 and moved up and down.
[0023]
Here, the support stage 21 includes a θ rotation stage 21a that rotates the object 100 around the z-axis by a desired angle, and an XY stage 21b that moves the object 100 to an arbitrary position in the xy plane. And an αβ rotation stage 21c for rotating the subject 100 around the x-axis and the y-axis by a desired angle. By combining these stages 21a to 21c with the Z-axis coarse movement stage 23 and the like, the subject 100 can be three-dimensionally held in an arbitrary arrangement and posture with respect to the observation head 25.
[0024]
At the lower end of the observation head 25, a revolver 34 to which a plurality of objective lenses 31 and 32 of different magnifications are attached is fixed, and the objective lenses 31 and 32 can be switched and arranged on the optical path. In a specific example, the magnifications of the objective lenses 31 and 32 were set to 5 times and 100 times, respectively. Here, the magnification of the objective lens is the ratio of the focal length with the imaging lens 41. For example, if the focal length fc of the imaging lens is 180 mm, when the focal length fo of the objective lens is 1.8 mm, This objective lens is 100 times. Inside the observation head 25, an imaging lens 41 for once collecting parallel light beams from the objective lenses 31 and 32, a half mirror 51 for partially splitting a light beam converged through the imaging lens 41, and a half mirror 51 A branch optical system 52 disposed on the optical path branched by the mirror 51, an ND filter 61 disposed retreatably on the optical path in the vicinity of the focusing point of the imaging lens 41, and an optical path close to the ND filter 61 on the optical path And a high-magnification imaging unit 71 disposed behind the focal point of the imaging lens 41 and movable in the z-axis direction, that is, in the optical axis direction.
[0025]
Here, the high-magnification-side objective lens 31 fixed to the revolver 34 can be finely moved in the Z-axis direction, that is, in the optical axis direction by a Z-axis fine movement device 35 having a built-in piezo element.
[0026]
The branch optical system 52 includes an alignment camera 54 that captures a low-magnification image branched by the half mirror 51, and a pair of laser light sources 55 and 56 that are light sources for an autocollimator. The branched light reflected by the half mirror 54a enters the alignment camera 54 as the alignment imaging means. Further, the first collimator light having a wavelength of, for example, 410 nm from the laser light source 55 is incident on the imaging lens 41 via the dichroic mirror 56a and the half mirrors 54a and 51, and becomes a parallel light flux toward the revolver 34. Further, the second collimator light having a wavelength of, for example, 655 nm from the laser light source 56 is also incident on the imaging lens 41 via the dichroic mirror 56a and the half mirrors 54a and 51, and forms a parallel light flux toward the revolver 34. The dichroic mirror 56a is formed of a dielectric multilayer film, and efficiently couples the first and second collimator lights having different wavelengths and guides them to the same optical path.
[0027]
The chart 63 is for visually measuring the amount of eccentricity of the spot image or the alignment image projected on the high-magnification imaging unit 71 from the optical axis. The spot image and the alignment image can be adjusted relatively easily by displacing the 100 or adjusting the posture. Note that the chart 63 is removed from the optical path at the time of final measurement in which the spot image is read by the high-magnification imaging unit 71 and image processing is performed.
[0028]
The high-magnification imaging unit 71 includes a relay (magnification) lens 73 and a measurement camera 74 as an enlargement imaging unit. The observation light once condensed via the imaging lens 41 is incident on the relay (magnification) lens 73, and an enlarged image of the spot formed by the subject 100 is projected on the imaging surface 74 a of the measurement camera 74. I do. With the relay lens 73 interposed, an image 10 times larger than that of the alignment camera 54 is projected on the measurement camera 74, for example. In other words, by exchanging the high-magnification objective lens 31 and the low-magnification objective lens 32, the measurement camera 74 can observe images of 50 × and 1000 ×. In the alignment camera 54, images of 5 × and 100 × can be observed by exchanging the objective lenses 31 and 32.
[0029]
In the above spot measuring device, the objective lenses 31 and 32, the imaging lens 41, and the relay lens 73 constitute a magnifying optical system, that is, a measuring optical system.
[0030]
FIG. 2 is a diagram illustrating a control system of the spot measuring device shown in FIG. The spot measuring device includes a support stage driving device 26, a lifting stage driving device 27, a revolver driving device 36 for changing the objective magnification, a pair of laser drivers 57 and 58 for an autocollimator, and a brightness adjusting device as a control system. And an imaging unit driving device 76 for driving the imaging unit, a laser driver 110 for measurement, and a computer 80 for controlling these components. The revolver driving device 36 also has a built-in D / A conversion circuit for supplying a driving voltage to the piezo elements constituting the Z-axis fine movement device 35.
[0031]
The support stage driving device 26 controls the position, the rotation angle, or the inclination posture of the subject 100 in the xy plane based on an instruction from the computer 80. The elevating stage driving device 27 raises and lowers the observation head 25 based on an instruction from the computer 80, and adjusts an imaging position, an imaging state, and the like. The revolver driving device 36 can rotate the revolver 34 by an appropriate amount at an appropriate timing based on an instruction from the computer 80, and can arrange any of the objective lenses 31 and 32 on the optical axis OA. The objective lens 31 can be finely moved in the direction of the optical axis OA by operating the built-in Z-axis fine movement device 35 as well as the state without any intervention. The laser drivers 57 and 58 operate the laser light sources 55 and 56 at an appropriate timing based on an instruction from the computer 80 at the time of auto-collimation, and generate alignment light necessary for auto-collimation. When observing the spot image with the measuring camera 74, the filter driving device 65 appropriately operates the ND filter 61 based on an instruction from the computer 80 to adjust the irradiation luminance on the imaging surface 74a. The imaging unit driving device 76 can finely reciprocate the high-magnification imaging unit 71 along the optical axis OA direction based on an instruction from the computer 80, check the convergence and divergence of the parallel light, and check the R at the time of the autocollimator. The tilt of the surface can be adjusted. The laser driver 110 for measurement causes the inspection light to be incident on the objective lens 101 based on an instruction from the computer 80 to form a spot image. The images detected by the alignment camera 54 and the measurement camera 74 are appropriately processed by the computer 80. At this time, the brightness or brightness of the image can be adjusted by adjusting the electronic shutter of the alignment camera 54 or the measurement camera 74.
[0032]
Hereinafter, the operation of the spot measuring device shown in FIGS. 1 and 2 will be described. First, the alignment of the test object 100 using the autocollimator function will be described. At this time, the operation of the laser light source 102 on the test object 100 side is stopped, and the laser light source 55 or 56 on the branch optical system 52 side is operated. At this time, the revolver 34 is operated to retract the objective lenses 31 and 32 outside the optical axis OA. The alignment light from the laser light source 55 or 56 is incident on the upper surface of the objective lens 101 via the imaging lens 41. Since a relatively flat annular surface is usually formed on the outer periphery of the upper surface of the objective lens 101 to be measured, the measurement light reflected on this annular surface is turned back and travels almost in parallel, and the imaging lens 41 and the like are turned around. And enters the alignment camera 54 as an alignment image. Next, the inclination of the test object 100 is adjusted by operating the αβ rotation stage 21 c and the like provided on the support stage 21, and the spot image of the measurement light is centered so as to enter the center of the angle of view of the alignment camera 54. Thereby, the optical axis of the test objective lens 101 can be made substantially coincident with the optical axis OA of the spot measuring instrument. At this stage, the reading of the image is switched from the alignment camera 54 to the measurement camera 74. Next, the high-magnification imaging unit 71 is moved in the direction of the optical axis OA via the imaging unit driving device 76 to minimize the spot diameter of the alignment image detected by the measurement camera 74. Next, the αβ rotation stage 21c and the like provided on the support stage 21 are finely moved again to adjust the inclination posture of the test object 100 so that the alignment image of the measurement light is incident on the center of the angle of view of the measurement camera 74. Center. Thereby, the optical axis of the test objective lens 101 can be precisely arranged in parallel with the optical axis OA of the spot measuring instrument.
[0033]
At this time, the alignment light to be incident on the objective lens 101 can be either one or both of the two laser light sources 55 and 56. However, if the anti-reflection coat is formed on the objective lens 101, Since there is a possibility that the reflected light of one of the laser light sources 55 and 56 becomes weak, one of the laser light sources 55 and 56 is appropriately selected so as to obtain the measurement light of high intensity.
[0034]
In the above description, the optical surface itself may be used when the annular surface of the outer periphery of the objective lens 101 to be inspected has an R shape or when the central optical surface of the objective lens 101 to be inspected is substantially flat. it can. When the annular surface or the central optical surface on the outer periphery of the test objective lens 101 is a curved surface, the high-magnification imaging unit 71 is moved in the direction of the optical axis OA to minimize the alignment image and adjust the tilt. From the position or displacement of the high-magnification imaging unit 71, the degree of convergence and divergence of the measurement light, that is, the curvature of the surface can be quantitatively confirmed to some extent.
[0035]
Hereinafter, observation of a spot image formed by the subject 100 will be described. In this case, the laser light source 102 on the test object 100 side is operated, and the operation of the laser light sources 55 and 56 on the branch optical system 52 side is stopped. At this time, the revolver 34 is operated to dispose the objective lens 31 and the like on the optical axis OA. Observation light from a spot image formed by making the inspection light from the laser light source 102 incident on the objective lens 101 to be inspected is reflected by the half mirror 51 via the objective lens 31, the imaging lens 41, and the like, and is reflected by the alignment camera 54. Incident on. Next, the XY stage 21b provided on the support stage 21 is operated to perform centering so that the spot of the observation light is incident on the center of the angle of view of the alignment camera 54. Next, the image reading is switched from the alignment camera 54 to the measurement camera 74. Next, the XY stage 21b provided on the support stage 21 is operated again to perform centering so that the spot image of the observation light enters the center of the angle of view of the measuring camera 74. In this manner, the shape and brightness distribution of the spot image projected at the center of the angle of view of the measuring camera 74 can be measured, and the spot image can be measured on a display 81 or a printer as a display means provided in the computer 80. Results and analysis results can be displayed.
[0036]
In the alignment and measurement of the spot image as described above, the focus of the spot image is adjusted by appropriately operating the Z-axis coarse movement stage 23 and the Z-axis fine movement device 35. In alignment and measurement of the spot image, the brightness of the spot image detected by the alignment camera 54 and the measurement camera 74 is adjusted by adjusting the transmittance of the ND filter 61 and the shutter speed of the alignment camera 54 and the measurement camera 74. Is adjusted as appropriate.
[0037]
Further, when measuring the spot image, the objective lens 31 is finely moved stepwise in units of, for example, about 25 nm in the z-axis direction by the Z-axis fine movement device 35, while the spot image is captured by the measurement camera 74, and the captured image is read. By performing the analysis, the profile of the spot image in the optical axis OA direction can also be measured.
[0038]
FIG. 3 is a flowchart illustrating a process of causing the spot measuring device shown in FIGS. 1 and 2 to perform an automatic alignment operation under the control of the computer 80. Here, the “automatic alignment operation” means a series of steps for automatically guiding a spot image formed by the subject 100 to the center of the image of the measurement camera 74.
[0039]
First, the state of the spot measuring device is initialized (step S1a). Specifically, the revolver 34 is driven to set the objective lenses 31 and 32 on the low magnification side, and the image to be processed by the computer 80 is set as the image on the alignment camera 54 side.
[0040]
Next, as preparation for performing auto-focusing on the spot image formed by the objective lens 101 near the optical axis OA, an auto-gain process is performed (step S1b), and an auto-centering process is performed (step S1c). . In the auto gain process, the brightness of the spot image obtained by the alignment camera 54 is adjusted to a state suitable for measurement, and in the auto centering process, the spot image obtained by the alignment camera 54 is moved to the center of the screen.
[0041]
Next, using the Z-axis coarse movement stage 23 and the Z-axis fine movement device 35, the spot image obtained by the alignment camera 54 is auto-focused to obtain a sharp image (step S1d).
[0042]
Next, even when the magnification is increased in the next process, the auto gain process is performed in the same procedure as in steps S1b and S1c so that the spot image is included in the image of the measurement camera 74 (see FIG. In step S1e), an auto centering process is performed (step S1f).
[0043]
Next, it is determined whether the objective lenses 31, 32 currently on the optical axis OA are high magnification or low magnification (step S1g). Initially, since the magnification is low, in the next step S1h, it is determined whether the camera under observation is of the measurement type or the alignment type. Initially, the image on the alignment camera 54 side is processed, so in the next step S1i, the camera is switched to the measurement system, the image from the measurement camera 74 is taken into the computer 80, and the process returns to step S1b. In this case, the image processed by the computer 80 is magnified 5 to 50 times.
[0044]
After that, the spot image obtained from the measuring camera 74 is subjected to an auto gain process (step S1b), an auto centering process (step S1c), and an auto focus process (step S1d). Further, an auto gain process is performed so that the spot image is contained in the image in the next process (step S1e), and an auto centering process is performed (step S1f). Next, in step S1g, the current objective lens 32 is again determined to have a low magnification, but in the next step S1h, the camera under observation is determined to be of the measurement system. In this case, in the next step S1j, the camera is switched to the alignment system again, and the low magnification objective lens 32 is switched to the high magnification objective lens 31 (step S1k). In this case, the image processed by the computer 80 is magnified 50 to 100 times.
[0045]
Thereafter, the spot image obtained from the alignment camera 54 is subjected to an auto gain process (step S1b), an auto centering process (step S1c), and an auto focus process (step S1d). Further, an auto gain process is performed so that the spot image is contained in the image in the next process (step S1e), and an auto centering process is performed (step S1f). In the next step S1g, it is determined that the current objective lens 31 has a high magnification, and in the next step S1m, it is determined that the camera under observation is of the alignment type. In this case, in the next step S1n, the camera is switched to the measurement system again. In this case, the image processed by the computer 80 is enlarged 100 times to 1000 times.
[0046]
Thereafter, the spot image obtained from the measuring camera 74 is subjected to an auto gain process (step S1b), an auto centering process (step S1c), and an auto focus process (step S1d). Further, an auto gain process is performed so that the spot image is contained in the image in the next process (step S1e), and an auto centering process is performed (step S1f). The spot image of the test objective lens 101 obtained as described above is the largest enlarged image, and is further centered at the center of the image, and is suitable for spot shape measurement.
[0047]
FIG. 4 is a flowchart conceptually explaining the auto gain processing in steps S1b and S1e in FIG. First, an initial setting relating to the imaging gain is performed (step S2a). Specifically, the shutter speed of the electronic shutter of the alignment camera 54 and the measuring camera 74 is set to the highest speed so as to darken the spot image, and the transmittance of the ND filter 61 is set so as to brighten the spot image. The largest. Next, automatic shutter adjustment for obtaining an optimum value of the shutter speed is performed (step S2b). Specifically, the brightness distribution of the spot image is detected by gradually increasing the shutter speed, and when the brightness peak value of the spot image is saturated, the shutter speed is set to a set value. In the case of the alignment camera 54, since the adjustment by the ND filter 61 cannot be performed, the shutter speed immediately before the saturation is set as the set value. Next, it is determined whether the camera currently used is of the measurement type or the alignment type (step S2c). If the image on the alignment camera 54 is being processed, the process is terminated. If the image on the measurement camera 74 is being processed, the automatic ND adjustment is performed in the next step S2d (step S2d). Specifically, the luminance distribution of the spot image is detected by gradually increasing the transmittance of the ND filter 61, and when the saturation of the luminance peak value of the spot image has been eliminated, the shutter speed is set to the set value.
[0048]
FIG. 5 is a flowchart conceptually illustrating the auto-centering process in steps S1c and S1f in FIG. First, the image after the automatic gain processing is read from the alignment camera 54 or the measurement camera 74 (step S3a). Next, the luminance distribution of the captured image is analyzed to detect how much the center of gravity of the spot image deviates from the pixel center of the camera (step S3b). At this time, the shift amount in pixel units is converted into a shift amount in μm units, and further converted into the number of motor pulses for driving the XY stage 21b. Finally, the XY stage 21b is moved to move the center of gravity of the spot image to the center of the pixel (step S3c).
[0049]
FIG. 6 is a flowchart conceptually illustrating the autofocus processing in step S1d of FIG. First, the focus direction, that is, the driving direction of the Z-axis fine movement device 35 or the Z-axis coarse movement stage 23 is predicted (step S4a). For this reason, the image is reacquired by shaking the focus slightly larger in a specific direction, and the spot image is almost in the screen and the detected energy (that is, the sum of the luminance distributions) is increased, or the spot image diameter is reduced. Is the focusing direction. Next, the Z-axis fine movement device 35 and the Z-axis coarse movement stage 23 are driven in the focusing direction obtained in step S4a (step S4b). Next, the image after the movement in step S4b is captured and compared with the image before the movement to determine whether or not the spot diameter is reduced (step S4c). If the spot diameter is narrow, a new position on the z-axis is updated and recorded as the best focus position (step S4d). If the spot diameter has not become narrow or the update of the best focus position has been completed, it is determined whether or not the spot diameter has become large (step S4e). If the spot diameter is not large, the process returns to step S4b and repeats the processing up to step S4e. If the spot diameter is large, the Z-axis fine movement device 35 or The Z-axis coarse movement stage 23 is driven to return to the best focus position (step S4f).
[0050]
Hereinafter, the contents of the flowcharts shown in FIGS. 4 to 6 will be described in detail as specific examples.
[0051]
7 to 9 are flowcharts showing details of the auto gain processing of FIG. First, in FIG. 7, it is determined whether or not the camera is a measurement system (step S21a). If "YES", that is, if an image is captured from the measurement camera 74, the ND filter 61 is opened (step S21b). Next, after setting the speed of the electronic shutter to the highest speed (step S21c), an automatic shutter adjustment process is performed (step S21d). In the next step S21e, it is determined whether or not an error has occurred in the automatic shutter adjustment processing. If an error has occurred, an error message is displayed and the processing is interrupted. If no error has occurred, it is determined in step S21f whether or not the camera is a measurement system. If an image from the alignment camera 54 has been captured, the process ends. If the is loaded, the automatic ND adjustment process is performed (step S21g). In the next step S21h, it is determined whether or not an error has occurred in the automatic ND adjustment processing. If an error has occurred, an error message is displayed and the processing is interrupted. If no error has occurred, the automatic gain processing ends.
[0052]
FIG. 8 is a flowchart illustrating an automatic shutter adjustment process corresponding to step S21d in FIG. First, a shutter speed is acquired from the camera currently capturing an image (step S22a), and an image is captured at the shutter speed (step S22b). In the next step S22c, it is determined whether or not the peak intensity of the brightness of the image is saturated. If not, it is determined whether or not the shutter speed is set to the lowest value and the brightest (step S22d). . If the shutter speed is the lowest value, this process ends. If the shutter speed is not the lowest value, the image is brightened by increasing the shutter speed by one step (step S22e). On the other hand, when it is determined in step S22c that the peak intensity of the luminance is in a saturated state, it is determined whether the camera is an alignment system (step S22f). When the image is captured from the alignment camera 54, the shutter speed is lowered by one step to darken the image (step S22g), and then the process ends.
[0053]
FIG. 9 is a flowchart illustrating the automatic ND adjustment processing corresponding to step S21g in FIG. First, the current ND value of the ND filter 61 is obtained (step S23a), and it is determined whether or not the ND value is set to be the darkest (step S23b). If the ND value is not the darkest, the ND value of the ND filter 61 is raised by one step to make it darker (step S23c), and an image is captured with the ND value (step S23d). In the next step S23e, it is determined whether or not the peak intensity of the luminance is in a non-saturated state. If the peak state of the luminance is in a non-saturated state, the process returns to step S23a and the processing up to step S23d is repeated. If there is, this process ends. On the other hand, if it is determined in step S23b that the ND value is the darkest, the shutter speed is acquired for the current camera (step S23f). Next, it is determined whether or not the shutter speed is the fastest value (step S23g). If the shutter speed is the fastest value and the darkest setting, it is determined that a normal image has not been obtained, and the processing is interrupted. On the other hand, if it is determined that the shutter speed is not the highest value, it is determined that the adjustment by the ND filter 61 has not been completed, and the ND filter 61 is opened and returned to the original state (step S23h).
[0054]
FIGS. 10 and 11 are flowcharts showing details of the auto-centering process of FIG. First, the field of view is acquired by the camera currently capturing an image (step S31a), and the size (movement amount) per pixel is calculated. In the next step S31b, it is determined whether or not the following loop has been repeated six times. If the number of repetitions is five or less, an image is captured from the current camera (step S31c). Next, the luminance center of gravity is calculated as coordinates on the pixel from the captured image (step S31d), and it is determined whether or not the contrast of the image is low (step S31e). If the contrast of the image is low, the processing is interrupted assuming that sufficient measurement accuracy cannot be obtained, and if the contrast of the image is equal to or greater than a predetermined value, the amount of shift of the luminance centroid from the image center image is calculated (step S31f). . In the next step S31g, it is determined whether or not the displacement is less than ± 2 pixels (step S31g). If the displacement is ± 2 pixels or more, the obtained displacement is supported for driving the XY stage 21b. It is converted into a pulse amount of a pulse motor or an encoder provided in the stage driving device 27 (step S31h). Next, the pulse position of the movement destination, that is, the coordinate position converted into the pulse is calculated (step S31j). Next, the movement of the XY stage 21b is started with the target pulse position as the target value (step S31k). In the next step S31m, it is determined whether or not the target position has been reached or a time-out has occurred. If not, the process waits for 50 ms (step S31n), returns to step S31m, and repeats the above checks. If "YES" is determined in the step S31m, it is determined whether or not the process has left the step S31m due to a timeout in a next step S31p. If the timeout has not occurred, it is determined that the process has left step S31m due to the arrival at the target position, and the process returns to step S31b and repeats the deviation correction processing up to step S31n. If the timeout has occurred, an error message is displayed and the processing is interrupted. If it is determined in step S31b that the loop has been completed six times, or if it is determined in step S31g that the swaging amount is equal to or more than two pixels, it is determined that the centering has been completed or substantially completed, and the processing is terminated.
[0055]
FIG. 12 is a flowchart that embodies the autofocus process of FIG. First, the magnification of the currently used objective lens is obtained from the revolver driving device 36. In the next step S41b, it is determined whether or not the objective lens has a high magnification and whether or not the camera currently used is of a measurement type or an alignment type (step S41b). When the objective lens has a low magnification or when processing an image from the alignment camera 54, the Z-stage AF process is performed by driving the Z-axis coarse movement stage 23 via the elevation stage driving device 27. (Step S41c). On the other hand, when the objective lens has a high magnification and processes an image from the measuring camera 74, a piezo element constituting the Z-axis fine movement device 35 is controlled via a control circuit provided in the revolver driving device 36. To perform the PZT-AF process (step S41d). After the PZT-AF processing, the 0 set position of the piezo element is reset to secure a movable range necessary for the next PZT-AF processing (step S41e). After the above steps S41c and S41e, it is determined whether or not an error has occurred during autofocusing (step S41f). If an error has occurred, an error message is displayed and the process is interrupted. If no error has occurred, the auto focus process ends.
[0056]
FIGS. 13 to 16 are diagrams for explaining the Z stage AF processing corresponding to step S41c in FIG. 12 in detail. First, in FIG. 13, focus direction prediction processing is performed (step S42a). Next, the moving speed of the Z-axis coarse movement stage 23 is determined based on the total magnification (step S42b). Next, a fine adjustment amount of the moving speed, that is, a step moving amount is obtained from a predetermined table (step S42c). Next, while starting the fine movement in the expected focus direction obtained in step S42a (step S42d), the position where the spot diameter becomes minimum is initialized (step S42e). Next, the current position of the Z-axis coarse movement stage 23 is obtained (Step S42f), the image at this time is captured (Step S42g), and the maximum luminance value on the screen is calculated (Step S42h). Next, the spot diameter is calculated (step S42i). At this time, regarding the luminance distribution in the x-axis direction, 1 / e ² Is the spot diameter. In the next step S42j, it is determined whether or not the spot diameter is equal to or less than 600 pixels among the maximum pixels 640. When the spot diameter is larger than 600 pixels and blur is large, the setting of the next movement speed is increased (step S42k), and the Z-axis coarse movement stage 23 is moved at the above-mentioned next movement speed (step S42m). The current spot value is stored as the stored value of (Step S42n). Thereafter, the process returns to step S42f to repeat the processing. On the other hand, when the spot diameter is 600 pixels or less and the blur is small, the setting of the next moving speed is slowed down (step S42p). In the next step S42q, it is determined whether or not the spot diameter this time is smaller than the previous time. When it is determined that the pot diameter has become narrow, this spot diameter is updated as the best spot diameter, and the position of the Z-axis coarse movement stage at this time is updated as the best focus position. In the next step S42s, it is determined whether or not the spot diameter this time is larger than the previous time. If the spot diameter is not thick, the stored value of the number of continuous expansions of the spot diameter is temporarily reset (step S42t), and the process proceeds to step S42m. On the other hand, when it is determined in step S42s that the pot diameter is large, 1 is added to the stored value of the number of continuous expansions (step S42u). In the next step S42v, it is determined whether or not the number of continuous inflation is four. If the number of continuous inflation is less than four, the process proceeds to step S42m, and if the number of continuous inflation is four, Proceeding to step S42w, the operation of the Z-axis coarse movement stage 23 is stopped (step S42w), the Z-axis coarse movement stage 23 is moved to the best focus position in step S42r, and the process is terminated.
[0057]
FIG. 15 illustrates details of the focus direction prediction processing in step S42a of FIG. First, information as to whether or not the Z-axis fine movement device 35, that is, the piezo element is valid is taken in (step S43a). That is, in the low-magnification objective lens 32, since the Z-axis fine movement device 35 is not provided, the piezo element becomes invalid. Next, the plus side movement distance is acquired (step S43b). This + side moving distance is appropriately determined by the total magnification. Next, an image is captured from the camera currently used (step S43c), and it is determined whether or not the contrast of the image is low (step S43d). Whether the contrast is low or not is determined as low contrast if the spot diameter is larger than 500 pixels and no saturation occurs. If the contrast of the image is low, the + side movement distance is extended and reset (step S43e), and the total energy of the spot image is calculated from the current image (step S43f). Next, including the case where the contrast of the image is high, the focus direction is moved to the + side comparison position moved by the + side movement distance (step S43g). At this time, if the piezo element is effective and the + side movement distance is within the range that can be covered by the piezo element, the piezo element, that is, the Z-axis fine movement device 35 is operated. Conversely, when the piezo element is invalid or the + side movement distance exceeds the range that can be covered by the piezo element, the Z-axis coarse movement stage 23 is operated. Next, in step S43h, it is determined whether or not the determination in step S43d is low contrast. If the contrast is equal to or more than a predetermined value, the spot diameter in the image at the + side comparison position is acquired (step S43i), and the direction in which the spot diameter becomes smaller is compared with the focus direction before and after moving to the + side comparison position. (Step S43j). On the other hand, if it is determined in step S43h that the contrast is low, the total energy at the + side comparison position is calculated (step S43k), and before and after moving to the + side comparison position, the direction in which the total energy becomes higher is focused. The direction is set (step S43m).
[0058]
FIG. 16 illustrates details of the + side comparison position moving process in step S43g of FIG. First, the position of the Z-axis fine movement device 35, that is, the position of the piezo element is obtained (step S44a), and the movement target is determined (step S44b). When the current moving distance of the + side described with reference to FIG. 15 is a range that can be covered by the piezo element and the current objective lens is provided with the Z-axis fine movement device 35 at a high magnification, the moving object is the piezo element, that is, the Z-axis fine movement device 35 And In other cases, the movement target is the Z-axis coarse movement stage 23. When the movement target is the Z-axis fine movement device 35 in step S44b, the piezo element is driven by the + side movement distance obtained in the previous step in the processing of FIG. 15 (step S44c), and the image from the camera under observation is displayed. (Step S44d), and the piezo element is returned to the original position (step S44e). The reason why the piezoelectric element is returned to the original position is to leave a margin for performing AF when returning to the flow of FIGS. 13 and 14 (this is a description of the Z coarse movement stage 23, The + side comparison position moving process is also used in the PZT-AF process.) On the other hand, when the movement target is the Z-axis coarse movement stage 23 in step S44b, the current stage position is acquired (step S44f). Next, the Z-axis coarse movement stage 23 is driven to move by the + side movement distance (step S44g). At this time, the + side moving distance is converted into the number of pulses required for driving the motor. In the next step S44h, it is determined whether or not the target position has been reached or a time-out has occurred. If neither is reached, the process waits for 50 ms (step S44i) and returns to step S44h. If YES is determined in the step S44h, it is determined whether or not the process has left the step S44h due to a timeout in the next step S44j. If it is determined that the target position has not been reached due to timeout, an error message is displayed and the processing is interrupted. On the other hand, when it is determined that the target position has been reached without time-out in step S44j, it is determined whether an image has been sampled (step S44k). If the image has not been collected, the image is captured (step S44m), and the Z-axis coarse movement stage 23 is returned to the original position (step S44n).
[0059]
FIG. 17 and FIG. 18 are flowcharts illustrating details of the PZT-AF processing in step S41d of FIG. First, the image is brightened by setting the shutter speed to the minimum value (step S45a), and the image is brightened by setting the ND value to the minimum value (step S45b). Next, the focus direction prediction process described with reference to FIG. 15 is performed (step S45c). Next, the piezo element, that is, the Z-axis fine movement device 35 is step-moved in the focusing direction obtained in step S42a (step S45e). The unit of the step movement is, for example, 0.05 μm. Next, an image is captured (step S45f), and a maximum luminance value is detected (step S45g). Next, it is determined whether or not the maximum luminance value is saturated (step S45h). If the maximum luminance value is saturated, it is determined whether or not the shutter speed is the fastest value and the darkest setting (step S45i). If it is determined in step S45i that the shutter speed is not the highest value, the image is darkened by increasing the shutter speed by one step, and the process returns to step S45f. If it is determined in step S45h that the shutter speed is not saturated, or if it is determined in step S45i that the shutter speed is the fastest value, the spot diameter is calculated from the image captured in step S45f (step S45k), and the step movement by the piezo element is performed. It is determined whether or not the diameter is smaller than the previously registered minimum spot diameter (step S45m). If it is determined that the spot diameter has decreased, the spot diameter at this time is updated and stored as the minimum spot diameter (step S45n), and the piezo position corresponding to this minimum spot diameter is updated and stored (step S45p). Thereafter, it is determined whether or not the spot diameter calculated in step S45k is larger than the minimum spot diameter ten times in a row (step S45q). Even if the spot diameter becomes larger than the minimum spot diameter, if it is less than 10 times in a row, the process returns to step S45e and repeats the processing up to step S45p. On the other hand, if it is determined in step S45q that the spot diameter has become larger than the minimum spot diameter continuously for 10 times or more, it is determined that the best focus has been passed, and the focus is returned to the piezo position stored in step S45p (step S45r). .
[0060]
【The invention's effect】
As is clear from the above description, according to the spot measuring device of the present invention, the inclination of the test object can be removed by the light source for the autocollimator, so that the light condensing state by the test object can be accurately detected. it can.
[0061]
Further, according to the spot measuring method of the present invention, since the centering is performed stepwise using the low-magnification projection optical system or the high-magnification projection optical system, the spot image formed by the test object is formed by the measurement optical system. Can be reliably introduced into the observation field of view of the target.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an external structure of a spot measuring device according to an embodiment.
FIG. 2 is a diagram illustrating a control system of the spot measuring device shown in FIG.
FIG. 3 is a flowchart illustrating a process for causing the spot measuring device shown in FIGS. 1 and 2 to perform an alignment operation.
FIG. 4 is a flowchart conceptually explaining an auto gain process in FIG. 3;
FIG. 5 is a flowchart conceptually illustrating an auto-centering process in FIG.
FIG. 6 is a flowchart conceptually explaining an autofocus process in FIG. 3;
FIG. 7 is a flowchart illustrating the processing of FIG. 4 in more detail;
FIG. 8 is a flowchart illustrating the processing of FIG. 4 in more detail;
FIG. 9 is a flowchart illustrating the processing of FIG. 4 in more detail;
FIG. 10 is a flowchart illustrating the processing of FIG. 5 in more detail;
FIG. 11 is a flowchart illustrating a continuation of the processing in FIG. 10;
FIG. 12 is a flowchart illustrating the processing of FIG. 6 in more detail;
FIG. 13 is a flowchart illustrating the processing of FIG. 12 in more detail;
FIG. 14 is a flowchart illustrating a continuation of the processing in FIG. 13;
FIG. 15 is a flowchart illustrating the processing of FIG. 13 in more detail.
FIG. 16 is a flowchart illustrating the processing of FIG. 15 in more detail;
FIG. 17 is a flowchart illustrating the processing of FIG. 12 in more detail;
FIG. 18 is a flowchart illustrating a continuation of the processing in FIG. 17;
[Explanation of symbols]
23 Z axis coarse movement stage
25 Observation head
26 Support stage drive
27 Lifting stage drive
31, 32 each objective lens
35 Z axis fine movement device
41 Imaging lens
51 Half mirror
52 branch optical system
54 Alignment Camera
55,56 laser light source
57,58 Laser driver
61 ND filter
71 High magnification imaging unit
73 relay lens
74 Camera for measurement
80 Computer
101 Objective lens to be inspected
102 laser light source

Claims (14)

An enlargement optical system for enlarging a spot image focused by the test object and projecting the spot image on an imaging surface;
Magnifying imaging means for photographing a spot image projected on the imaging surface,
Display means for displaying a spot image picked up by the enlarged image pickup means;
And a light source for an autocollimator disposed at a position conjugate to the imaging surface. The spot measuring machine according to claim 1, wherein the magnifying optical system includes a low-magnification projection optical system having an objective lens and an imaging lens, and a high-magnification projection optical system having a relay lens. 3. The spot measuring machine according to claim 2, wherein the light source for the autocollimator is disposed on an optical path branched by a branching mirror disposed between the low magnification projection optical system and the high magnification projection optical system. 4. The spot measuring apparatus according to claim 3, further comprising an alignment imaging unit configured to capture a low-magnification spot image condensed by the test object on the optical path branched by the branching mirror. 3. The spot measuring machine according to claim 2, wherein when the inclination of the test object is corrected by operating the light source for the autocollimator, the objective lens is retracted from an optical path. The spot measuring machine according to claim 1, wherein the light source for the autocollimator includes a plurality of laser light sources that generate laser lights having different wavelengths. The spot measuring apparatus according to claim 2, wherein the high-magnification projection optical system is movable in an optical axis direction. A spot measurement method for enlarging and projecting a spot image condensed by a test object onto an imaging surface,
Photographing a spot image converged by the test object with a low-magnification projection optical system including a first objective lens;
A first centering step of centering the test object based on a spot image captured by the low-magnification projection optical system including the first objective lens;
Photographing a spot image condensed by the test object centered in the first centering step with a measurement optical system in which a high-magnification projection optical system is added to a low-magnification projection optical system including the first objective lens;
A second centering step of centering the test object based on a spot image taken by a measurement optical system obtained by adding a high-magnification projection optical system to the low-magnification projection optical system including the first objective lens;
Capturing a spot image focused by the test object centered in the second centering step with a high-magnification projection optical system including a second objective lens;
A third centering step of centering the test object based on a spot image captured by the low-magnification projection optical system including the second objective lens;
Capturing a spot image converged by the test object centered in the third centering step with a measurement optical system in which a high-magnification projection optical system is added to a low-magnification projection optical system including the second objective lens;
A spot measurement method comprising: The magnification of a measurement optical system obtained by adding a high-magnification projection optical system to the low-magnification projection optical system including the first objective lens is lower than the magnification of the low-magnification projection optical system including the second objective lens. Item 8. The spot measuring method according to item 8. 10. The spot measuring method according to claim 8, further comprising an automatic focusing step before or after each centering step or both. 10. The spot measuring method according to claim 8, further comprising an automatic dimming step before or after each of the centering steps or both. The centering step is a step of calculating a center of gravity position or a peak intensity position of a captured spot image, and a step of driving a stage supporting a test object by a corresponding amount that offsets a deviation from the optical axis of the center of gravity position. The spot measuring method according to claim 8, comprising: 11. The spot measuring method according to claim 10, wherein the automatic focusing step includes a step of driving the low-magnification projection optical system or the measurement optical system experimentally to predict a focus direction in advance. The step of taking an image with the measuring optical system in which the high-magnification projection optical system is added to the low-magnification projection optical system including the second objective lens is performed by moving the imaging surface stepwise in the optical axis direction while collecting the light by the test object. 10. The spot measuring method according to claim 8, further comprising a step of photographing a spot image.

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