Chart, adjustment method for imaging optical system, evaluation method for imaging optical system, and evaluation apparatus

Abstract

To appropriately evaluate an imaging optical system without replacing a chart.SOLUTION: A chart 100 has a chart pattern 100p for evaluating an imaging optical system. The chart pattern 100p includes multiple closed regions 110, each having the same shape as a contour with two sides that are orthogonal to each other. Each of the multiple closed regions 110 is composed of a bright region having a circular shape and a dark region surrounding the bright region. The multiple closed regions include a central closed region located at a center 101 of the chart pattern 100p and multiple peripheral closed regions arranged radially from the center 101 and on concentric circles 150 centered at the center 101.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The disclosure of this specification relates to a chart, a method for adjusting an imaging optical system, a method for evaluating an imaging optical system, and an evaluation apparatus.

Background Art

[0002] An imaging optical system used in optical devices such as microscopes and cameras is composed of a plurality of lenses, and sufficient performance is exhibited when these plurality of lenses are arranged as designed. Therefore, in the assembly process of the imaging optical system, it is evaluated whether the imaging optical system exhibits the expected performance. If the performance is not sufficiently exhibited, it is determined that the lenses constituting the imaging optical system are not arranged as designed, and operations such as adjusting the eccentricity of the lenses and the lens intervals are performed.

[0003] One method for evaluating an imaging optical system in the assembly process is known, which uses a flat plate (hereinafter referred to as a chart) on which a predetermined pattern is formed. In this method, the imaging optical system is evaluated based on the image of the chart formed through the imaging optical system to be evaluated.

[0004] The chart used for evaluating the imaging optical system is described in, for example, Patent Document 1. Patent Document 1 describes a technique for calculating the MTF from the image of the edge portion of the pattern using the chart.

[0005] In addition to the method using the contrast of an image as described in Patent Document 1, for example, a method using the shape of a pinhole image is also known as a typical evaluation method of an imaging optical system using a chart.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the evaluation of an imaging optical system by the above two types of evaluation methods, dedicated charts are usually used respectively. Therefore, in order to comprehensively evaluate the imaging optical system by both of these evaluation methods, it is necessary to switch the charts.

[0008] However, the charts used for evaluation require higher accuracy than the performance of the imaging optical system to be evaluated. When switching such charts that require high accuracy, even if each is manufactured with sufficiently high accuracy, the error between the charts makes it difficult to correctly evaluate the imaging optical system.

[0009] Based on the above circumstances, an object according to one aspect of the present invention is to provide a technique that enables appropriate evaluation of an imaging optical system without exchanging charts.

Means for Solving the Problems

[0010] A chart according to one aspect of the present invention is a chart having a chart pattern for evaluating an imaging optical system, wherein the chart pattern includes a plurality of closed regions having the same shape each including two sides orthogonal to each other as a contour, and each of the plurality of closed regions consists of a bright portion having a circular shape and a dark portion surrounding the bright portion, and the plurality of closed regions include a central closed region placed at the center of the chart pattern and a plurality of peripheral closed regions arranged radially from the center and on concentric circles centered on the center.

[0011] A method for adjusting an imaging optical system according to an aspect of the present invention includes: arranging the chart according to the above aspect so that a bright portion of a closed region provided at the center of a chart pattern of the chart is located on the optical axis of the imaging optical system; imaging the chart with an image sensor through the imaging optical system to obtain an imaging image of the chart; generating a plurality of enlarged images obtained by enlarging portions of a plurality of closed regions included in the chart pattern from the imaging image, and displaying the enlarged images corresponding to different closed regions in respective ones of a plurality of display regions arranged in two dimensions; and adjusting eccentricity of the imaging optical system, inclination of an image plane formed by the imaging optical system, and flatness of the image plane based on information displayed in the plurality of display regions.

[0012] A method for adjusting an imaging optical system according to another aspect of the present invention includes: arranging the chart according to the above aspect so that a bright portion of a closed region provided at the center of a chart pattern of the chart is located on the optical axis of the imaging optical system; imaging the chart with an image sensor through the imaging optical system to obtain an imaging image of the chart; displaying images of a plurality of closed regions included in the chart pattern in the imaging image; calculating an evaluation result of the imaging optical system in each of the plurality of closed regions based on the imaging image; displaying the evaluation result in a corresponding closed region near each of the images of the plurality of closed regions; and adjusting eccentricity of the imaging optical system, inclination of an image plane formed by the imaging optical system, and flatness of the image plane based on the displayed evaluation result.

[0013] A method for evaluating an imaging optical system according to an aspect of the present invention includes: arranging the chart according to the above aspect such that a bright portion of a closed region provided at the center of a chart pattern of the chart is located on the optical axis of the imaging optical system; imaging the chart with an imaging device through the imaging optical system to obtain an imaging image of the chart; generating a plurality of enlarged images obtained by enlarging portions of a plurality of closed regions included in the chart pattern from the imaging image, and displaying the enlarged images corresponding to different closed regions in respective ones of a plurality of display regions arranged in two dimensions; and determining, based on information displayed in the plurality of display regions, the eccentricity of the imaging optical system, the inclination of an image plane formed by the imaging optical system, and the necessity of adjusting the flatness of the image plane.

[0014] A method for evaluating an imaging optical system according to another aspect of the present invention includes: arranging the chart according to the above aspect such that a bright portion of a closed region provided at the center of a chart pattern of the chart is located on the optical axis of the imaging optical system; imaging the chart with an imaging device through the imaging optical system to obtain an imaging image of the chart; displaying images of a plurality of closed regions included in the chart pattern in the imaging image; calculating an evaluation result of the imaging optical system in each of the plurality of closed regions based on the imaging image; displaying the evaluation result in the corresponding closed region near each of the images of the plurality of closed regions; and determining, based on the displayed evaluation result, the eccentricity of the imaging optical system, the inclination of an image plane formed by the imaging optical system, and the necessity of adjusting the flatness of the image plane.

[0015] An evaluation apparatus according to an aspect of the present invention includes a microscope including an imaging optical system, an imaging device that images the chart according to claim 1 through the imaging optical system, and a processor. The processor calculates an evaluation result of the imaging optical system in each of a plurality of closed regions included in a chart pattern of the chart based on an imaging image that is an image of the chart imaged by the imaging device, and determines whether adjustment of the imaging optical system is necessary based on the plurality of evaluation results of the imaging optical system corresponding to the plurality of closed regions.

Advantages of the Invention

[0016] According to the above aspect, it is possible to provide a technique that enables appropriate evaluation of the imaging optical system without exchanging the chart.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Embodiments for Carrying Out the Invention

[0018] FIG. 1 is a diagram illustrating a microscope system according to an embodiment of the present invention. The microscope system 1 shown in FIG. 1 is a system used for evaluating an imaging optical system using a chart 100, and includes a microscope 10, an imaging device 20, a computer 30, and a display 40.

[0019] The microscope 10 includes an imaging optical system to be evaluated. An imaging device 20 is attached to the lens barrel of the microscope 10. The imaging optical system projects an image of the chart 100 placed on the stage of the microscope 10 onto the imaging device 20. The imaging device 20 includes an imaging element and acquires an image of the chart 100 (hereinafter referred to as an imaging image) by imaging the chart 100 through the imaging optical system of the microscope 10. The chart 100 has a chart pattern for evaluating the imaging optical system. Therefore, the performance of the imaging optical system between the chart 100 and the imaging device 20 is appropriately reflected in the imaging image.

[0020] The microscope 10 may be an upright microscope or an inverted microscope. Also, in the microscope 10, transmitted illumination may be adopted, or epi-illumination may be adopted. Hereinafter, a case where the microscope 10 is an upright microscope that projects an image of the chart 100 onto the imaging device 20 using transmitted illumination will be described as an example.

[0021] The computer 30 is, for example, a personal computer having a processor 31 and a memory 32. Based on the fact that the performance of the imaging optical system is reflected in the imaging image, the computer 30 processes the imaging image acquired by the imaging device 20 and generates information useful for evaluating the imaging optical system. The computer 30 further causes the display 40 to display the generated information useful for evaluating the imaging optical system. These processes are performed by the processor 31 executing a program stored in the memory 32.

[0022] The user of the microscope system 1 checks the information displayed on the display 40 to evaluate the imaging optical system and determine whether the imaging optical system is properly assembled so as to exhibit the designed performance. Further, when the user determines that it is not properly assembled, the user performs an adjustment operation on the imaging optical system.

[0023] The imaging optical system includes the objective lens 11 and other lenses (such as an imaging lens and an adapter lens). When the other lenses are sufficiently adjusted in advance, the objective lens 11 can be substantially evaluated by evaluating the imaging optical system.

[0024] FIG. 2 is a diagram illustrating a chart according to an embodiment of the present invention. FIG. 3 is an enlarged view of a closed region included in the chart shown in FIG. 1. FIG. 4 is an example of an image obtained by imaging the closed region shown in FIG. 3 through the imaging optical system. FIG. 5 is a diagram for explaining an adjustment operation of the imaging optical system. Hereinafter, the chart 100 used in the microscope system 1 will be described with reference to FIGS. 2 to 5.

[0025] The chart 100 has a chart pattern 100p for evaluating the imaging optical system, which enables comprehensive evaluation of the imaging optical system from both aspects of the contrast and shape of the image. Specifically, as shown in FIG. 2, the chart pattern 100p includes a plurality of closed regions 110.

[0026] Each of the plurality of closed regions 110 has the same shape including two orthogonal sides as its contour, as shown in FIGS. 2 and 3. The shape of the closed region 110 is a square in this example, but it may have two orthogonal sides, and may be a rectangle or a sector having two orthogonal sides.

[0027] The two orthogonal sides that form the contour are suitable for evaluating the contrast of the image 210 (image 230 of the peripheral region 130 to be described later) of the closed region 110 shown in FIG. 4. To evaluate the contrast of the image, by processing in the computer 30, for example, the density profile of the portion (line) straddling the two sides of the image 230 shown in FIG. 4 is differentiated to calculate the LSF (Line Spread Function), and the MTF (Modulation Transfer Function) may be calculated by performing a Fourier transform on the LSF. Also, as a method for evaluating the contrast of the image, the difference in luminance values of adjacent pixels in the X and Y directions may be squared and the integrated value (Brenner Gradient) may be used as the evaluation value.

[0028] Note that the two orthogonal sides of the closed region 110 are preferably inclined with respect to the XY direction in which the pixels of the captured image are aligned, as shown in FIGS. 2 and 3. By differentiating the density profiles of a plurality of lines straddling the inclined sides (edges) and synthesizing the obtained plurality of LSFs, it is possible to calculate a synthesized LSF with a finer virtual sampling pitch. Note that the inclination of the edge is not particularly limited, but is, for example, about 1.5° to 3°.

[0029] Each of the plurality of closed regions 110 is composed of a pinhole 120 and a peripheral region 130 surrounding the pinhole 120, as shown in FIG. 3. The pinhole 120 is an example of a bright portion having a circular shape. The pinhole 120 may be, for example, an opening (through hole) provided in the chart 100, or may be composed of a transmissive member that transmits illumination light. The peripheral region 130 is an example of a dark portion surrounding the bright portion and has the two orthogonal sides described above. The peripheral region 130 may be, for example, a light-shielding member provided on the surface of the chart 100. Note that the light-shielding member is formed of a thin metal film. The thickness of the light-shielding member is, for example, 0.1 μm or less and has substantially no thickness.

[0030] The pinhole 120, which is a bright portion surrounded by the peripheral region 130 that is a dark portion, is suitable for evaluating the shape of the image (pinhole image 220). To evaluate the shape of the image (pinhole image 220), for example, by processing in the computer 30, the direction in which the pinhole image (pinhole image 220) blurs and trails (angle θ in FIG. 4), the length of the trail (ΔP in FIG. 4), etc. may be calculated.

[0031] As described above, each of the closed regions 110 in which the pinhole 120 is provided within the dark portion (peripheral region 130) having orthogonal edges (two sides) is suitable for both the evaluation of the contrast of the image and the evaluation of the shape of the pinhole image. Therefore, by using the chart 100, the imaging optical system can be comprehensively evaluated from both aspects of the contrast and shape of the image. Also, since the chart pattern 100p has a plurality of closed regions 110, without moving the chart 100 with respect to the imaging optical system, the evaluation of the imaging optical system at each position corresponding to each closed region 110 within the field of view can be performed individually.

[0032] Furthermore, as shown in FIG. 2, the plurality of closed regions 110 include a closed region 110 placed at the center 101 of the chart pattern 100p (this is referred to as the central closed region), and a plurality of closed regions 110 arranged radially from the center 101 and on concentric circles 150 centered on the center 101 (these are referred to as peripheral closed regions). That is, the chart pattern 100p has a plurality of closed regions 110 (peripheral closed regions) on each of the circles (concentric circles 151, concentric circles 152, concentric circles 153, concentric circles 154, concentric circles 155) that constitute the concentric circles 150 centered on the center 101. Further, each of the plurality of closed regions 110 (peripheral closed regions) on each circle is arranged in the same azimuth from the center 101 as the corresponding closed region 110 (peripheral closed region) on the other circles. In this way, since the plurality of closed regions 110 are aligned in the radial direction and the circumferential direction with the center 101 as the center, by comparing the evaluations at the positions corresponding to each closed region 110, it is possible to grasp how the evaluation changes for each of the radial direction and the circumferential direction.

[0033] By using the chart 100 having the chart pattern 100p, it is possible to comprehensively evaluate whether the imaging optical system exhibits the expected performance in terms of both the contrast and shape of the image for each position within the field of view (more precisely, the position corresponding to each closed region 110). In the evaluation, since it is not necessary to replace the chart 100, it is possible to avoid the adverse effect on the evaluation due to the difference in error between the charts 100. Also, since it is not necessary to move the chart 100 for evaluating different positions within the field of view, it is possible to avoid the influence of errors in position and inclination caused by the movement. Furthermore, by comparing the evaluations at each position within the field of view, it is also possible to grasp the bias in the performance of the imaging optical system.

[0034] Based on this information, the user may perform the necessary adjustments to the imaging optical system (the objective lens 11). For example, as shown in FIG. 5, the lens 14 fixed to the lens frame 15 may be adjusted for eccentricity by pushing the lens unit 16 with an adjustment rod through the hole 13 provided in the barrel member 12 of the objective lens 11. Also, the objective lens 11 may be reassembled to adjust the lens interval. Thereby, it is possible to adjust so that the imaging optical system exhibits the designed performance.

[0035] Also, in order to accurately evaluate up to the periphery of the optical system, it is desirable to define the diagonal direction of the chart pattern 100p and the radius D of the outermost concentric circle 155 constituting the concentric circles 150 so that the closed regions are imaged around the four corners of the field of view (the rectangle obtained by projecting the imaging element onto the object plane) of the imaging device used, that is, so that the closed regions are arranged in the diagonal direction of the field of view of the imaging device.

[0036] For example, when the aspect ratio of the imaging device 20 (imaging element) is 4:3, it is desirable to arrange the closed regions 110 so that the closed regions 110 are located around the four corners thereof, regardless of whether the imaging device 20 is arranged in the vertical direction or the horizontal direction with respect to the chart pattern 100p. Thereby, it is possible to accurately evaluate the field of view range of the imaging device 20 regardless of whether the imaging device 20 is arranged in the vertical direction or the horizontal direction.

[0037] Specifically, as shown in FIG. 2, in addition to the vertical and horizontal directions, it is desirable to arrange the closed region 110 in four diagonal directions (±36° direction and ±54° direction). The rectangles 20a and 20b in FIG. 2 respectively show the viewing ranges of the imaging device when the imaging device is arranged in the vertical and horizontal directions. The chart 100 is configured such that the closed region 110 is arranged at all four corners of either of the rectangles 20a and 20b.

[0038] When the aspect ratio of the imaging device 20 (image sensor) is 1:1, in addition to the vertical and horizontal directions, the closed region 110 may be arranged in two diagonal directions (±45° direction).

[0039] Next, a more desirable configuration of the chart pattern 100p will be described. First, a desirable configuration of the closed region 110 included in the chart pattern 100p will be described, and then a desirable configuration of the interval between the closed regions 110 will be described.

[0040] As shown in FIG. 3, the pinhole 120 of each closed region 110 is preferably near the center of gravity of the closed region 110. For example, the center of gravity position of the closed region 110 is preferably located within the pinhole 120. Also, the diameter of the pinhole 120 is preferably 1 / 5 or less of the short side of the closed region 110. That is, when the diameter of the pinhole 120 is P and the length of the short side of the two orthogonal sides included in the contour of the closed region 110 is L1, it is desirable for the chart 100 to satisfy the following conditional expression (1). P≦L1 / 5 ···(1)

[0041] Since the pinhole 120 is near the center of gravity of the closed region 110 and the conditional expression (1) is satisfied, it becomes possible to more appropriately evaluate the imaging optical system from both the contrast and shape of the image using the chart 100.

[0042] Although the pinhole 120 is surrounded by the peripheral region 130, if the adjustment of the imaging optical system is insufficient, the shape of the image 220 of the pinhole 120 will be distorted as shown in FIG. 4, for example. At this time, in order to correctly recognize the shape of the image 220 of the pinhole 120, it is desirable that the image 220 of the pinhole 120 is contained within the image 230 of the peripheral region 130 which is the dark part. If the image 220 protrudes from the image 230, it becomes difficult to correctly grasp the shape of the image 220 of the pinhole, so the sensitivity to the insufficient adjustment of the imaging optical system (for example, misalignment, etc.) decreases.

[0043] If the pinhole 120 is located at a position greatly deviated from the center of gravity of the closed region 110, the image 220 of the pinhole 120 is likely to protrude from the image 230 of the peripheral region 130, which is not desirable. Also, even when the pinhole 120 is near the center of gravity of the closed region 110, if the pinhole 120 is too large with respect to the closed region 110, the image 220 of the pinhole 120 is likely to protrude from the image 230 of the peripheral region 130, which is not desirable. For this reason, in order to appropriately evaluate the shape of the image 220 of the pinhole 120, it is desirable that the pinhole 120 is near the center of gravity of the peripheral region 130 and satisfies the conditional expression (1).

[0044] Also, if the image 220 of the pinhole 120 protrudes from the image 230 of the peripheral region 130, there is a possibility of adversely affecting the contrast evaluation of the edge of the peripheral region 130. For this reason, in order to appropriately evaluate the contrast of the image 230 of the peripheral region 130 as well, it is desirable that the pinhole 120 is near the center of gravity of the peripheral region 130 and satisfies the conditional expression (1).

[0045] The conditional expression (1) shows the condition that the pinhole 120 is not too large with respect to the peripheral region 130, but it is also not desirable that the pinhole 120 is too small with respect to the peripheral region 130.

[0046] The pinhole 120 desirably has a size such that the shape of the image 220 of the pinhole 120 enlarged through the imaging optical system can be visually recognized. That is, it is desirable that the user observing the image 220 of the pinhole 120 can recognize how much it deviates from the circular shape. Also, the diameter of the pinhole 120 desirably is at least larger than the resolution of the imaging optical system (Rayleigh resolution, Abbe resolution, Hopkins resolution, etc.). Specifically, when the wavelength of the light used for evaluating the imaging optical system is λ and the numerical aperture on the object side of the imaging optical system is NA, it is desirable that the chart 100 satisfies the following conditional expression (2). When a human visually observes and evaluates, visible light (400 nm to 700 nm) is used, so the wavelength λ is, for example, 550 nm with high relative visual sensitivity. P≧1.5×λ / NA ···(2)

[0047] Since the image 220 of the pinhole 120 is visible and the conditional expression (2) is satisfied, it becomes possible to more appropriately evaluate the imaging optical system using the chart 100 from the shape of the pinhole image.

[0048] For example, when evaluating an objective lens with NA 0.70, the closed region 110 of the chart 100 may be configured with the following size as an example. Pinhole diameter P = 2 μm Length of two sides L = 30 μm (=L1 = L2)

[0049] The closed region 110 desirably is smaller than one-tenth of the maximum image height evaluated using the chart pattern 100p. Further, it is desirable that there is a gap such that at least one more closed region 110 can fit between the closed regions 110 adjacent in the image height direction (radial direction). That is, when the length of the long side of the two orthogonal sides included in the contour of the closed region 110 is L2, the radius of the outermost concentric circle 155 constituting the concentric circles 150 is D, and the minimum gap between the closed regions 110 adjacent in the radial direction of the concentric circles 150 is G, it is desirable that the chart 100 satisfies the following conditional expressions (3) and (4). L2≦D / 10 ···(3) G ≥ L2 ···(4)

[0050] The evaluation of the imaging optical system is often performed in steps of 0.1 times the image height ratio. If the size of the closed region 110 becomes larger than one-tenth of the maximum image height, there is a risk that the closed regions 110 arranged at positions corresponding to the image height in steps of 0.1 will overlap each other. Therefore, in order to correctly perform the evaluation at each image height, it is desirable to satisfy the conditional expression (3).

[0051] Also, if the closed region 110 itself is too large, it becomes difficult to regard the four corners of the closed region 110 as points at the same image height. In particular, when the gap between the radially adjacent closed regions 110 is small and the gap is smaller than the length of the closed region 110 (for example, the diagonal length or L2, etc.), it is difficult to say that it is appropriate to treat the evaluation of the imaging optical system in each closed region 110 as the evaluation at a specific image height. Therefore, it is desirable to simultaneously satisfy the conditional expression (3) and the conditional expression (4).

[0052] Hereinafter, in each embodiment, specific examples of the adjustment method and evaluation method of the imaging optical system using the above-described chart 100 will be described.

[0053] <First Embodiment> FIG. 6 is a flowchart showing an example of the procedure of the adjustment method of the imaging optical system according to the present embodiment. FIG. 7 is an example of a screen displayed in the adjustment method of the imaging optical system according to the present embodiment. FIG. 8 is an enlarged view of the contrast information shown in FIG. 7.

[0054] In the adjustment method of the imaging optical system according to the present embodiment, as shown in FIG. 6, first, the chart 100 is placed on the stage of the microscope system 1 (step S1). Here, the chart 100 is arranged so that the pinhole 120 of the closed region 110 provided at the center 101 of the chart pattern 100p is located on the optical axis of the imaging optical system. This arrangement may be manually performed by the user of the microscope system 1, for example, or may be automatically performed by the electric part of the microscope system 1.

[0055] Next, the microscope system 1 captures an image of the chart 100 with the imaging device 20 via the imaging optical system, and acquires a captured image of the chart 100 (step S2). Thereafter, the microscope system 1 causes the display 40 to display an image of the closed region 110 based on the captured image acquired in step S2 (step S3).

[0056] In step S3, the microscope system 1 first generates a plurality of enlarged images (enlarged images 311 to 319) obtained by enlarging portions of a plurality of closed regions 110 included in the chart pattern 100p from the captured image. The plurality of enlarged images may be generated by selecting two or more closed regions 110 from all the closed regions 110 included in the chart pattern 100p. Each of the enlarged images is generated, for example, by cutting out and enlarging a portion of the closed region 110 from the captured image.

[0057] Thereafter, as shown in FIG. 7, the microscope system 1 displays a plurality of enlarged images (enlarged images 311 to 319) on the screen 40a of the display 40. More specifically, the microscope system 1 displays an enlarged image corresponding to a different closed region in each of a plurality of display regions (display regions 41 to 49) arranged two-dimensionally on the screen 40a of the display 40. The enlarged image may be displayed on the display 40 at a display magnification higher than the magnification when the entire captured image is displayed on the display 40.

[0058] Which enlarged image is displayed in which display region is determined based on the positional relationship between the display region and the closed region. That is, the process of step S3 includes a process of determining the enlarged image to be displayed in each of the plurality of display regions based on the positional relationship between the display region and the closed region.

[0059] Specifically, in the central display area 45 among the nine display areas shown in FIG. 7, the microscope system 1 may display an enlarged image 315 corresponding to the central closed area placed at the center 101 of the chart pattern 100p (or an enlarged image corresponding to the peripheral closed area adjacent to the central closed area). Further, in the microscope system 1, among the remaining eight display areas shown in FIG. 7, for the display areas in the up, down, left, and right directions from the center, enlarged images corresponding to the peripheral closed areas in the up, down, left, and right directions from the center 101 may be respectively displayed. For the display areas in the upper left, lower left, upper right, and lower right directions from the center, enlarged images corresponding to the peripheral closed areas in the upper left, lower left, upper right, and lower right directions from the center 101 may be respectively displayed. Note that the enlarged images 311 to 319 displayed in the display areas 41 to 49 shown in FIG. 7 each include the closed areas 111 to 119 shown in FIG. 2.

[0060] When step S3 ends, the microscope system 1 calculates an evaluation result of the imaging optical system in each of a plurality of closed areas corresponding to a plurality of display areas based on the captured image obtained in step S2 (step S4). The evaluation result calculated in step S4 is, for example, information indicating the contrast of the enlarged image of the closed area (hereinafter simply referred to as contrast information).

[0061] After calculating the evaluation result, the microscope system 1 displays the evaluation result calculated in step S4 on the screen 40a of the display 40 (step S5). Specifically, based on the evaluation result calculated in step S4, the microscope system 1 displays, as shown in FIG. 7, contrast information (contrast information C1 to contrast information C9), which is the evaluation result in the corresponding closed area, in each of the plurality of display areas.

[0062] The contrast information C (a general term for contrast information C1 to C9) is, for example, a band graph as shown in FIG. 8 that allows intuitive grasp of the level of contrast. This band graph, for example, displays the region R1 from 0 to the current value Vc of the contrast and the region R2 from the current value Vc to the peak value Vp in different colors. Note that the peak value Vp is the peak value of the contrast in the corresponding closed region. For example, if the evaluation of the imaging optical system is being performed while focusing, the peak value Vp can be regarded as the contrast value in the most focused state.

[0063] The execution order of steps S3 to S5 described above is not particularly limited. As shown in FIG. 7, it is sufficient that the enlarged image of the corresponding closed region and the evaluation result are displayed in each of the plurality of display regions.

[0064] When the enlarged image and the evaluation result are displayed, the imaging optical system is adjusted (step S6) based on the information (enlarged image and contrast information) displayed in the plurality of display regions. More specifically, the user of the microscope system 1 adjusts the eccentricity of the lens of the imaging optical system and the lens interval, thereby adjusting the eccentricity of the imaging optical system, the tilt of the image plane formed by the imaging optical system, and the flatness of the image plane.

[0065] According to the method for adjusting the imaging optical system using the chart 100 shown in FIG. 6 described above, the user can evaluate the shape of the pinhole image from the enlarged image displayed on the display 40, and further evaluate the contrast of the image from the contrast information displayed on the display 40. Therefore, the imaging optical system can be comprehensively evaluated based on the shape and contrast of the image, and the necessary adjustments can be made to the imaging optical system.

[0066] In addition, an enlarged image of a corresponding plurality of closed regions and an evaluation result are displayed in each of a plurality of display regions that divide the screen 40a. Since the enlarged image of the closed region and the evaluation result displayed in each display region are determined based on the positional relationship between the display region and the closed region, the user can grasp at a glance how the performance of the imaging optical system changes within the field of view based on the information displayed in the plurality of display regions.

[0067] <Second Embodiment> FIG. 9 is an example of a screen displayed in the adjustment method of the imaging optical system according to the present embodiment. The procedure of the adjustment method of the imaging optical system using the chart 100 according to the present embodiment is the same as that of the first embodiment except that the evaluation results calculated in step S4 and displayed in step S5 are different.

[0068] In the present embodiment, in step S4, the microscope system 1 calculates, as the evaluation result, in addition to the contrast information of the enlarged image of the closed region corresponding to the evaluation result, shape information indicating the shape of the pinhole image. The shape information indicating the shape of the pinhole image includes, for example, the direction in which the tail of the pinhole image extends (for example, the angle θ in FIG. 4) and the length of the tail of the pinhole image (for example, the length ΔP in FIG. 4).

[0069] When the evaluation result is calculated in step S4, in step S5, the microscope system 1 displays the screen 40b shown in FIG. 9 on the display 40 based on the evaluation result calculated in step S4. The screen 40b is different from the screen 40a of the first embodiment in that contrast information (contrast information C1 to contrast information C9) and shape information (shape information E1 to shape information E9), which are evaluation results in the corresponding closed regions, are displayed in each of the plurality of display regions.

[0070] Note that the shape information E (a general term for shape information E1 to shape information E9) may be information that can intuitively grasp the degree of deterioration of the shape of the pinhole image. For example, it may be an arrow graphic as shown in FIG. 9. In this case, the size (thickness and length) and color density of the arrow may indicate the length of the tail, and the direction of the arrow may indicate the direction of the tail.

[0071] Even with the method for adjusting the imaging optical system according to the present embodiment, the user can comprehensively evaluate the imaging optical system from the shape and contrast of the image and perform necessary adjustments, similar to the first embodiment. In particular, in the present embodiment, in addition to the enlarged images (enlarged images 311 to 319) displayed on the display 40, the shape of the pinhole image can also be evaluated from the shape information (shape information E1 to shape information E9).

[0072] <Third Embodiment> FIG. 10 is an example of a screen displayed in the method for adjusting the imaging optical system according to the present embodiment. The procedure of the method for adjusting the imaging optical system using the chart 100 according to the present embodiment is the same as that of the first embodiment, except that the evaluation result calculation step of step S4 and the evaluation result display step of step S5 are omitted.

[0073] In the present embodiment, the microscope system 1 displays the screen 40c shown in FIG. 10 on the display 40. The user evaluates both the shape of the pinhole image and the contrast of the image from the enlarged image displayed on the display 40. Therefore, even with the adjustment method according to the present embodiment, the imaging optical system can be comprehensively evaluated from the shape and contrast of the image, and necessary adjustments can be made.

[0074] <Fourth Embodiment> FIG. 11 is an example of a screen displayed in the method for adjusting the imaging optical system according to the present embodiment. The procedure of the method for adjusting the imaging optical system using the chart 100 according to the present embodiment is the same as that of the second embodiment, except that in step S3, the images themselves (images 411 to 419) cut out from the captured image instead of the enlarged image are displayed, and in step S5, the evaluation results (contrast information C) are displayed for each image displayed in the display area instead of for each display area.

[0075] In this embodiment, in step S3, the microscope system 1 displays images of a plurality of closed regions included in the chart pattern 100p in the captured image. The plurality of images may be generated by selecting two or more closed regions 110 from all the closed regions 110 included in the chart pattern 100p. Each of the images is generated, for example, by cutting out the portion of the closed region 110 from the captured image.

[0076] In this embodiment, in step S3, the microscope system 1 displays images of a plurality of closed regions included in the chart pattern 100p in the captured image. Specifically, the microscope system 1 first selects two or more closed regions 110 from all the closed regions 110 included in the chart pattern 100p, and cuts out the portions of the selected closed regions 110 from the captured image to generate a plurality of images. Then, as shown in FIG. 11, the microscope system 1 displays different images (images 411 to 419) in each of a plurality of display regions (display regions 41 to 49) arranged two-dimensionally on the screen 40d of the display 40. Each image may include portions of one or more closed regions, or may include portions of a plurality of closed regions.

[0077] When step S3 ends, the microscope system 1 calculates contrast information C and shape information E as evaluation results of the imaging optical system in each of the plurality of closed regions displayed in the plurality of display regions based on the captured image obtained in step S2 (step S4). The shape information E is an example of first evaluation information indicating the direction in which the bright portion included in the image of the corresponding closed region extends and the length of the bright portion, and the contrast information C is an example of second evaluation information indicating the contrast of the image of the corresponding closed region.

[0078] When the evaluation result is calculated in step S4, the microscope system 1 displays the evaluation result calculated in step S4 on the screen 40d of the display 40 (step S5). Specifically, as shown in FIG. 11, the microscope system 1 displays the evaluation results (contrast information C and shape information E) in the corresponding closed region near each of the images of the plurality of closed regions. That is, when the image contains images of a plurality of closed regions as in the image 411, the evaluation results for each closed region are displayed near the image of the closed region.

[0079] Also, with the imaging optical system adjustment method according to the present embodiment, the user can comprehensively evaluate the imaging optical system from the shape and contrast of the image and perform necessary adjustments, similar to the above-described embodiments. Further, in the present embodiment, by displaying an image cut out from the captured image, it is possible to display images of more closed regions than when displaying a magnified image, and thereby, it is possible to confirm the performance of a wider range within the field of view. Also, although it becomes more difficult to grasp the shape of the pinhole image from the image compared to the case of displaying a magnified image by not using the magnified image, by displaying the shape information E in addition to the image, it is possible to appropriately evaluate the shape of the pinhole image equivalently to the case of displaying a magnified image.

[0080] In the first to fourth embodiments, an example in which the user determines whether adjustment of the imaging optical system is necessary while looking at the screen displayed on the display 40 has been shown. However, the microscope system 1 may determine whether adjustment of the imaging optical system is necessary, and the determination result may be displayed on the display 40. Hereinafter, an example in which the microscope system 1 operates as an evaluation device that determines whether adjustment of the imaging optical system is necessary and displays the determination result will be described.

[0081] <Fifth Embodiment> FIG. 12 is a flowchart showing an example of the procedure of the imaging optical system evaluation method according to the present embodiment. FIG. 13 is an example of a screen displayed in the imaging optical system evaluation method according to the present embodiment.

[0082] In the method for evaluating the imaging optical system according to this embodiment, as shown in FIG. 12, first, a chart 100 is placed on the stage of the microscope system 1 (step S11). Then, the microscope system 1 acquires a captured image of the chart 100 (step S12), and based on the captured image, enlarged images corresponding to different closed regions are displayed on each of a plurality of display regions arranged two-dimensionally on the screen 40a of the display 40 (step S13). Further, the microscope system 1 calculates the evaluation result of the imaging optical system in each of a plurality of closed regions corresponding to the plurality of display regions based on the captured image acquired in step S2 (step S14), and displays the evaluation result in the corresponding closed region on each of the plurality of display regions based on the evaluation result calculated in step S4 (step S15). Note that the processing from step S11 to step S15 is the same as the processing from step S1 to step S5 of the method for adjusting the imaging optical system according to the second embodiment.

[0083] Thereafter, the microscope system 1 determines whether adjustment of the imaging optical system is necessary (step S16). Here, the microscope system 1 determines the necessity of adjusting the eccentricity of the imaging optical system, the inclination of the image plane formed by the imaging optical system, and the flatness of the image plane based on the information displayed in the plurality of display regions. The determination method is not particularly limited. For example, the eccentricity of the imaging optical system may be determined based on whether the evaluation results (contrast information C, shape information E) of each closed region fall within the allowable range of the expected performance. Further, the inclination and flatness of the image plane of the imaging optical system may be determined based on the presence or absence of deviation in the evaluation results of the closed regions within the field of view.

[0084] Finally, the microscope system 1 displays the determination result regarding whether adjustment of the imaging optical system is necessary (step S17). The display method of the determination result is not particularly limited. For example, as shown in FIG. 13, the microscope system 1 may pop up and display a new window W1 including the determination result on the screen 40a of the display 40. Note that the user who has confirmed the determination result may then adjust the imaging optical system.

[0085] According to the method for evaluating the imaging optical system according to this embodiment, the microscope system 1 can comprehensively evaluate the imaging optical system from the shape and contrast of the image, and determine whether adjustment of the imaging optical system is necessary. Further, by evaluating the imaging optical system according to a certain standard, the microscope system 1 can perform adjustment work based on whether adjustment of the imaging optical system is determined according to a certain standard regardless of the user of the microscope system 1. Furthermore, since the microscope system 1 displays the enlarged images of the respective closed regions and the evaluation results on the screen 40a, the user himself / herself can confirm whether the determination made by the microscope system 1 is appropriate based on the enlarged images and the evaluation results. Therefore, since the determination made by the microscope system 1 is not black-boxed, the user can be convinced of the determination and adjust the imaging optical system as necessary.

[0086] <Sixth Embodiment> FIG. 14 is an example of a screen displayed in the method for evaluating the imaging optical system according to this embodiment. The processing from step S11 to step S15 of the procedure of the method for evaluating the imaging optical system using the chart 100 according to this embodiment is the same as the processing from step S1 to step S5 of the method for adjusting the imaging optical system according to the fourth embodiment.

[0087] Thereafter, the microscope system 1 determines whether adjustment of the imaging optical system is necessary (step S16), and displays the determination result regarding whether adjustment of the imaging optical system is necessary (step S17). The method of displaying the determination result is not particularly limited. However, for example, as shown in FIG. 14, the microscope system 1 may pop-up display a new window W2 including the determination result on the screen 40d of the display 40. Note that the user who has confirmed the determination result may then adjust the imaging optical system.

[0088] Even with the method for evaluating the imaging optical system according to the present embodiment, the microscope system 1 can comprehensively evaluate the imaging optical system from the shape and contrast of the image and determine whether adjustment of the imaging optical system is necessary, in the same manner as the evaluation method according to the fifth embodiment. Further, by evaluating the imaging optical system by the microscope system 1 according to a certain standard, the user can perform an adjustment operation based on whether adjustment of the imaging optical system determined according to the certain standard is necessary, and the user can also confirm whether the determination made by the microscope system 1 is appropriate based on the image and the evaluation result, which is the same as in the fifth embodiment.

[0089] The above-described embodiments are presented with specific examples for easy understanding of the invention, and the present invention is not limited to these embodiments. Modified forms of the above-described embodiments and alternative forms that replace the above-described embodiments may be included. That is, each embodiment can deform the components without departing from the spirit and scope thereof. Further, by appropriately combining a plurality of components disclosed in one or more embodiments, a new embodiment can be implemented. Also, some components shown in each embodiment may be deleted, or some components may be added to the components shown in the embodiment. Furthermore, the processing procedures shown in each embodiment may be performed in a different order as long as there is no contradiction.

[0090] In the above-described embodiment, the chart 100 including one pinhole 120 in one closed region 110 is exemplified, but the chart for evaluating the imaging optical system may include a plurality of pinholes 120 in one closed region 110. Also in this case, although the pinhole 120 satisfies the conditional expression (1), a more stringent condition such as P ≦ L1 / 10 may be imposed on the diameter P of the pinhole 120 according to the number of pinholes 120 included in the closed region 110.

[0091] Also, the sizes of the plurality of pinholes 120 included in one closed region 110 may be the same or different. In the case of different sizes, the pinhole diameter may be set according to the specifications of the imaging optical system such as NA and magnification.

[0092] In addition, when a plurality of pinholes 120 are included in one closed region 110, there may be a case where a bright portion corresponding to the pinhole 120 is not located at the center of gravity position of the closed region 110.

[0093] In the above-described embodiment, the chart 100 has been shown as an example having a pinhole 120 that transmits light as a circular bright portion, but the bright portion is not limited to the pinhole 120. In a microscope system employing epi-illumination, the chart may include a configuration that reflects light as a circular bright portion, or may be configured such that light passes through a dark portion surrounding the bright portion.

[0094] In the above-described embodiment, an example in which a plurality of closed regions 110 are arranged radially has been shown. However, as long as they are arranged in a plurality of directions from the center 101, they do not necessarily have to be arranged radially. However, the radial arrangement is desirable in that the imaging optical system can be evaluated from the evaluation results of the plurality of closed regions 110 arranged on different concentric circles for each direction.

[0095] In the above-described embodiment, an example in which the same number of a plurality of closed regions 110 are arranged on each concentric circle has been shown. However, as long as a plurality of closed regions 110 are arranged on each concentric circle, the same number of closed regions 110 do not necessarily have to be arranged.

[0096] Although not particularly mentioned in the above-described embodiment, it is desirable that the evaluation of the imaging optical system be performed with the chart 100 in focus. The steps after the image acquisition in the methods shown in FIGS. 6 and 12 may be performed for each z position at the time of focus adjustment. That is, at the time of focus adjustment, image acquisition, calculation of evaluation, and display of the image and evaluation results may be repeatedly performed in real time. Further, in this case, the contrast information C displayed in each display region may be used to determine whether the focus is achieved.

[0097] In the above-described embodiments, an example in which a plurality of display areas have the same size has been shown, but the plurality of display areas may include display areas of different sizes. For example, in the example shown in FIG. 11, a display area 45 in which the range of the image to be displayed is relatively narrow may be configured to be smaller than the surrounding display areas. Thereby, the space within the screen 40d can be utilized more efficiently.

[0098] In this specification, the expression "based on A" does not mean "based only on A", but means "based at least on A", and further means "based at least in part on A". That is, "based on A" may be based on B in addition to A, or may be based on a part of A.

Explanation of Reference Numerals

[0099] 1 Microscope system 10 Microscope 11 Objective lens 20 Imaging device 30 Computer 31 Processor 32 Memory 40 Display 41~49 Display area 100 Chart 100p Chart pattern 101 Center 110~119 Closed area 120 Pinhole 130 Peripheral area 150~155 Concentric circles 210, 220, 230 Images 311~319 Enlarged images 411~419 Images C, C1~C9 Contrast information E, E1~E9 Shape information

Claims

1. A chart having a chart pattern for evaluating an imaging optical system, wherein the chart pattern includes a plurality of closed regions each having the same shape with two sides perpendicular to each other included in the contour, each of the plurality of closed regions includes a bright portion having a circular shape, and a dark portion surrounding the bright portion, and the plurality of closed regions include a central closed region placed at the center of the chart pattern, and a plurality of peripheral closed regions arranged radially from the center and on concentric circles centered on the center, A chart characterized by the above.

2. In the chart according to Claim 1, the centroid position of each of the plurality of closed regions is located within the bright portion, and satisfies the following conditional expression P ≤ L1 / 5... (1) A chart characterized by satisfying the above. However, L1 is the length of the shorter side of the two sides included in the contour of the closed region, and P is the diameter of the bright portion.

3. In the chart according to Claim 2, and satisfies the following conditional expression P ≥ 1.5 × λ / NA... (2) A chart characterized by satisfying the above. However, λ is the wavelength of light used for evaluating the imaging optical system, and NA is the numerical aperture on the object side of the imaging optical system.

4. In the chart according to Claim 1 or Claim 2, and satisfies the following conditional expressions L2 ≤ D / 10... (3) G ≥ L2... (4) A chart characterized by satisfying the above. However, L2 is the length of the long side of the two sides included in the contour of the closed region, D is the radius of the outermost circle constituting the concentric circles, and G is the minimum gap between the closed regions adjacent in the radial direction of the concentric circles.

5. A method for adjusting an imaging optical system, comprising: arranging the chart according to claim 1 so that the bright part of the closed region provided at the center of the chart pattern of the chart is located on the optical axis of the imaging optical system; imaging the chart with an imaging device through the imaging optical system to obtain an imaging image of the chart; generating a plurality of enlarged images obtained by enlarging portions of a plurality of closed regions included in the chart pattern from the imaging image, and displaying the enlarged images corresponding to different closed regions in respective ones of a plurality of display regions arranged in a two-dimensional manner; adjusting eccentricity of the imaging optical system, inclination of an image plane formed by the imaging optical system, and flatness of the image plane based on information displayed in the plurality of display regions. A method characterized by the above.

6. The method according to claim 5, further comprising: calculating an evaluation result of the imaging optical system in each of the plurality of closed regions corresponding to the plurality of display regions based on the imaging image; displaying the evaluation result in the corresponding closed region in each of the plurality of display regions. A method characterized by the above.

7. The method according to claim 5 or claim 6, wherein the step of displaying the enlarged image includes determining the enlarged image to be displayed in each of the plurality of display regions based on a positional relationship between the display region and the closed region. A method characterized by the above.

8. A method for adjusting an imaging optical system, comprising: The step of arranging the chart according to claim 1 such that the bright part of the closed region provided at the center of the chart pattern of the chart is located on the optical axis of the imaging optical system; The step of imaging the chart with an image sensor through the imaging optical system to obtain an image of the chart; The step of displaying images of a plurality of closed regions included in the chart pattern in the captured image; The step of calculating an evaluation result of the imaging optical system for each of the plurality of closed regions based on the captured image; The step of displaying the evaluation result for the corresponding closed region in the vicinity of each of the images of the plurality of closed regions; The step of adjusting eccentricity of the imaging optical system, inclination of the image plane formed by the imaging optical system, and flatness of the image plane based on the displayed evaluation result, characterized by the above.

9. In the method according to claim 8, the evaluation result includes first evaluation information indicating a direction in which a bright part included in the image of the corresponding closed region extends and a length of the bright part, and second evaluation information indicating contrast of the image of the corresponding closed region. characterized by the above.

10. In the method according to claim 8 or claim 9, the step of displaying images of the plurality of closed regions includes the step of determining a position for displaying the images of the plurality of closed regions based on a positional relationship of the plurality of closed regions. characterized by the above.

11. A method for evaluating an imaging optical system, comprising: The step of arranging the chart according to claim 1 such that the bright part of the closed region provided at the center of the chart pattern of the chart is located on the optical axis of the imaging optical system; The step of imaging the chart with an image sensor through the imaging optical system to obtain an image of the chart; Generating a plurality of enlarged images by enlarging portions of a plurality of closed regions included in the chart pattern from the captured image, and displaying the enlarged images corresponding to different closed regions in respective ones of a plurality of display regions arranged two-dimensionally; Determining a necessity for adjustment of decentration of the imaging optical system, inclination of an image plane formed by the imaging optical system, and flatness of the image plane based on information displayed in the plurality of display regions. A method characterized by the above.

12. In the method according to claim 11, further comprising: Calculating an evaluation result of the imaging optical system in each of the plurality of closed regions corresponding to the plurality of display regions based on the captured image; Displaying the evaluation result in the corresponding closed region in each of the plurality of display regions. A method characterized by the above.

13. In the method according to claim 11 or claim 12, The step of displaying the enlarged image includes determining the enlarged image to be displayed in each of the plurality of display regions based on a positional relationship between the display region and the closed region. A method characterized by the above.

14. A method for evaluating an imaging optical system, comprising: Arranging the chart according to claim 1 such that a bright portion of a closed region provided at the center of the chart pattern of the chart is located on the optical axis of the imaging optical system; Imaging the chart with an image sensor via the imaging optical system to obtain a captured image of the chart; Displaying images of a plurality of closed regions included in the chart pattern in the captured image; Calculating an evaluation result of the imaging optical system in each of the plurality of closed regions based on the captured image; Displaying the evaluation result in the corresponding closed region in the vicinity of each of the images of the plurality of closed regions. Based on the indicated evaluation results, a step of determining the necessity of adjusting the eccentricity of the imaging optical system, the inclination of the image plane formed by the imaging optical system, and the flatness of the image plane is included. A method characterized by this.

15. In the method according to claim 14, The evaluation results are First evaluation information indicating the direction in which the bright part included in the image of the corresponding closed region extends and the length of the bright part, and Second evaluation information indicating the contrast of the image of the corresponding closed region, and includes A method characterized by this.

16. In the method according to claim 14 or claim 15, The step of displaying the images of the plurality of closed regions includes a step of determining the positions for displaying the images of the plurality of closed regions based on the positional relationship of the plurality of closed regions. A method characterized by this.

17. A microscope including an imaging optical system, An image sensor that images the chart according to claim 1 through the imaging optical system, A processor, and is provided with The processor Based on the captured image, which is an image of the chart captured by the image sensor, calculates the evaluation results of the imaging optical system in each of the plurality of closed regions included in the chart pattern that the chart has, Determines whether adjustment of the imaging optical system is necessary based on the plurality of evaluation results of the imaging optical system corresponding to the plurality of closed regions. An evaluation apparatus characterized by this.

18. In the evaluation apparatus according to claim 17, The evaluation results are First evaluation information indicating the direction in which the bright part included in the image of the corresponding closed region extends and the length of the bright part, and Second evaluation information indicating the contrast of the image of the corresponding closed region, and includes An evaluation apparatus characterized by the following.

Images