JP2014109616A - Optical microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a pattern projection measurement while keeping such convenience of an optical microscope that observation magnification can be freely changed, and limiting enlargement of the microscope to the minimum necessary.SOLUTION: First and second light projection parts 110 are each composed of an optical system having a fixed magnification (for typical example, a double sided telecentric lens). A zoom lens is used in a light receiving part 120, so that the light receiving part 120 can receive light in a wide magnification range. An imaging device 121a is constituted by a monochrome imaging device such as a monochrome CCD (charge-coupled device). The imaging device 121a has such a resolution that, when receiving a projection pattern on a subject S on a stage 140, at least one and preferably a plurality of pixels are included in the minimum pattern width on an observation image at the time of the minimum observation magnification (light receiving magnification).

Description

  The present invention relates to an optical microscope, and more particularly to an optical microscope having a pattern projection measurement function capable of handling a wide observation magnification range.

  The optical microscope continues to evolve with digitization as seen in Patent Documents 1 and 2 and the like. In particular, Patent Document 2 proposes an inverted microscope that does not require a dark room and can be placed on a desk that performs daily work to observe an object.

  As is well known, optical microscopes are roughly classified into an upright type and an inverted type depending on the arrangement of optical systems. The upright microscope irradiates illumination light from a light source disposed below the stage toward an object on the stage positioned above, and receives the light with an objective lens (light receiving unit) disposed above the stage. Configuration is adopted.

  On the other hand, an inverted microscope irradiates illumination light from a light source disposed above the stage toward an object on the stage located below, and receives light with an objective lens (light receiving unit) disposed below the stage. Configuration is adopted.

  Whether it is an upright type or an inverted type, a recent optical microscope has a camera having an image element in a light receiving portion, and it is a standard to display an image taken by the camera on a monitor. Note that an eyepiece for observing an object through the human eye is incorporated in the middle of the optical system of the light receiving unit. However, as seen in Patent Documents 1 and 2, an optical microscope without an eyepiece has also appeared. This optical microscope is also called a digital microscope.

  By the way, as can be seen in Patent Document 3, a measuring apparatus using pattern projection is known. In principle, this pattern projection measurement projects the pattern light (slit light in this Patent Document 3) obliquely to the object, receives the reflected light with a camera, and uses the principle of triangulation. It is used to measure the three-dimensional shape of an object.

  Conventional pattern projection measurement apparatuses are generally designed on the assumption of a single magnification. Specifically, manufacturers have a system of lineup as a set that matches the optical magnifications of light projection and light reception. From this, the user can select from the set of magnifications that the manufacturer has lined up. The actual situation is that a desired set is selected.

  In general, it is recognized that it is desirable to design the observation magnification and the projection magnification optically in a fixed pair relationship such as 1: 1, for example, in order to increase the measurement accuracy. Based on this, the manufacturer designs a set that matches the optical magnifications of light projection and light reception.

JP 2008-164642 A JP 2012-18818 A JP 2003-214824 A

  Optical microscopes have achieved high resolution with the evolution of light receiving elements (imaging elements), and since a series of computer processing from observation to measurement, analysis, recording, management, and output is possible, for example, Used for inspection and analysis. One feature of the optical microscope is that it has an optical zoom function, for example, an interchangeable objective lens such as a revolver objective lens, and the observation magnification corresponding to the purpose can be freely selected.

  Attempts have been made to add a function of measuring a three-dimensional shape to the optical microscope. The optical microscope has a function of measuring a three-dimensional shape, thereby creating a 3D (three-dimensional) image and displaying it on the display, measuring the height profile data of an arbitrary line, the height on the measurement line, Not only can the width and unevenness be displayed in a graph, but also the height, width, area, surface roughness, and the like can be measured.

  When developing an optical microscope that can measure a three-dimensional shape, especially an optical microscope equipped with a pattern projection measurement function, when the target is narrowed down to a microscope that can be used on a desk where daily operations are performed, the minimum necessary Efforts to keep it large are required.

  Since pattern projection measurement uses the principle of triangulation as described above, a projection lens that projects pattern light obliquely to an object is required. When such a concept is introduced, it is necessary to change the magnification of the light projecting lens in accordance with the change in the magnification of the light receiving unit.

  An object of the present invention is to provide an optical microscope capable of pattern projection measurement while maintaining the convenience of freely changing the observation magnification of the optical microscope and keeping the size as large as necessary.

  The present invention has been devised as a result of studying the conventional idea itself of designing the observation magnification and the projection magnification in an optically paired relationship. In other words, as long as the conventional design guideline of designing the observation magnification and the projection magnification to be optically paired is followed, it is necessary to add a mechanism that can change the projection magnification in accordance with the change of the observation magnification. It is difficult to avoid the enlargement of the microscope and the complexity of the mechanism.

  The first feature of the present invention is that the observation magnification (light reception magnification) and the projection magnification are separated in the design of the optical system. That is, the first feature of the present invention is that the projection lens is fixed at a constant magnification, and a projection pattern with a constant magnification is always applied to the object regardless of whether or not the observation magnification (light reception magnification) is changed. In other words, the first feature of the present invention is that an optical microscope capable of switching the observation magnification includes a projection pattern illumination optical system that does not have a variable optical system for a plurality of observation magnifications. .

  The second feature of the present invention is that the two-dimensional array is used to generate the pattern light, and the light from the light source of the light projecting unit, that is, the light from the measurement light source is transmitted through the two-dimensional array or reflected by the two-dimensional array. The generated pattern is applied to an object through a projection lens having a constant magnification. As a preferred embodiment of the present invention, a double-sided telecentric lens is employed as the light projecting lens. By adopting the telecentric lenses on both sides, the pattern projection area can be made rectangular even if light is obliquely applied to the object. Here, the received light basic image means an image received when no object is present.

  The third feature of the present invention is that the number of pixels included in the minimum pattern width (minimum pattern width on the observation image) of the projection pattern received by the light receiving element of the light receiving unit is at least one when the light receiving magnification is minimum, Preferably, there are a plurality of points. That is, according to the present invention, even when the light receiving magnification (observation magnification) is set to the lowest magnification, the number of pixels included in the minimum pattern width imaged on the light receiving element is at least one, preferably a plurality. It is a third feature. Here, the minimum pattern width means the minimum pattern width in the pattern on the stage, that is, the minimum pattern width of the projection pattern.

  That is, the third feature of the present invention is that the minimum pattern width in the pattern generation unit and the light receiving pixels are optically paired in the past, but in the present invention, the light receiving magnification (observation magnification) is increased. A plurality of light receiving pixels corresponding to the number of light receiving pixels are included in the minimum pattern width on the light receiving side (observed image). For example, when a light reception magnification of 3 times is selected, a light reception pixel of 3 times is included in the minimum pattern width on the light reception side. For example, when a light reception magnification (observation magnification) of 1.5 times is selected, a light reception pixel of 1.5 times is included in the minimum pattern width on the light reception side. Conversely, for example, even if a light reception magnification (observation magnification) of 0.5 times is selected, it is sufficient to include at least one pixel in the minimum pattern width on the light reception side.

  According to the present invention, since the light projection magnification is set to a constant magnification, there is no need for a mechanism or control for changing the light projection magnification according to the fluctuation of the light reception magnification. The object can be measured three-dimensionally while maintaining the flexibility of a certain observation magnification.

  In addition, since the width of the projection pattern on the observation image is wider than the resolution on the light receiving (observation) side, the measurable depth of field becomes deep. Since the depth on the light projecting side is deeper than that on the light receiving side, the measurement depth is determined by the light receiving depth (observation depth) at the measurement depth defined for the entire system, and the depth can be maximized. If the minimum pattern to be projected is thin, the pattern tends to be blurred due to the depth of the light projecting side, and as a result, the measurement depth is obtained by superimposing the light reception depth and the light projection depth, but the light projection pattern is thick and the pattern Since the blur is not conspicuous, the projection depth is so wide that it can be ignored with respect to the light reception depth, and as a result, the measurement depth can be defined by the light reception depth. In addition, because the pattern is thick, sufficient measurement accuracy can be obtained without increasing the resolution on the light projecting side, and even if a light projection lens with a low resolution is used for the light receiving lens, the measurement accuracy is affected. There is an advantage that it is difficult.

  Even if the observation magnification (light reception magnification) changes, only the number of light receiving pixels included in the minimum pattern width on the observation image changes, and there is no need to change the measurement method according to the observation magnification. In addition, the measurement method has been changed in response to a request to further increase the resolution of received light because it is composed of a system in which multiple light-receiving pixels are included in the minimum pattern width on the observation image. This can be dealt with by adopting a light-receiving element (imaging element) with a high resolution without doing so.

  Other objects and advantages of the present invention will become apparent from the detailed description of the embodiments of the present invention.

It is a block diagram which shows the structure of the optical microscope which concerns on one embodiment of this invention. It is a schematic diagram which shows the structure of the measurement part of the optical microscope of FIG. It is a schematic diagram of the measuring object in the state irradiated with light. It is a schematic diagram of the measuring object in the state irradiated with light. It is a figure which shows an example of GUI which displays an image on 2 screens. It is a figure for demonstrating the principle of a triangulation system. It is a figure for demonstrating the 1st pattern of measurement light. It is a figure for demonstrating the 2nd pattern of measurement light. It is a figure for demonstrating the 3rd pattern of measurement light. It is a figure which shows the relationship between the pixel data (the intensity | strength of the light received) in the specific part of a measuring object, and the order (the order) of the image from which pixel data was obtained. It is a figure for demonstrating the 4th pattern of measurement light. It is a figure for demonstrating the effect when a telecentric lens is employ | adopted as a light projection part. It is a conceptual block diagram of the optical microscope of 2nd Example. It is a figure for demonstrating that a wide magnification range is realizable by the combination and process of a 1st light-receiving part of a low magnification, and a 2nd light-receiving part of a high magnification. It is a conceptual block diagram of the optical microscope of 3rd Example. It is a conceptual block diagram of the optical microscope of 4th Example. It is a conceptual block diagram of the optical microscope of 5th Example. It is a conceptual block diagram of the optical microscope of 6th Example. A relatively low-magnification observation area (observation field) and a relatively high-magnification observation area (observation field) are shown, and the explanation is that the minimum pattern width on the high-magnification observation image is relatively thick. FIG. It is a conceptual block diagram of the optical microscope of 7th Example. FIG. 21 is a conceptual configuration diagram of a minute displacement driving mechanism included in the seventh embodiment of FIG. 20. It is a conceptual block diagram of the optical microscope of 8th Example. It is a conceptual block diagram of the optical microscope of 9th Example. It is a conceptual block diagram of the optical microscope of 10th Example. It is a conceptual block diagram of the optical microscope of 11th Example.

First Example (FIGS. 1 to 12) :
An optical microscope according to a first embodiment to which the present invention is applied will be described. FIG. 1 is a block diagram illustrating a configuration of an optical microscope 500 according to the first embodiment. FIG. 2 is a schematic diagram illustrating the configuration of the measurement unit of the optical microscope 500 of FIG. Referring to FIGS. 1 and 2, the optical microscope 500 includes a measurement unit 100, a PC (personal computer) 200, a control unit 300, and a display unit (monitor) 400 (FIG. 1).

  The measuring unit 100 includes a light projecting unit 110, a light receiving unit 120, an illumination light output unit 130, a stage 140, and a control board 150. The light projecting unit 110 includes a measurement light source 111, a pattern generation unit 112, and a plurality of lenses 113, 114, and 115. The light receiving unit 120 includes a camera 121 and a plurality of lenses 122 and 123. The measuring object S is placed on the stage 140.

  The light projecting unit 110 includes a light projecting unit disposed obliquely above the stage 140. The light projecting unit 110 irradiates light obliquely to the surface of the measuring object S. The measuring unit 100 may include a plurality of light projecting units 110. In the example of FIG. 2, the measurement unit 100 includes two light projecting units 110. Hereinafter, when distinguishing the two light projecting units 110, one light projecting unit 110 is referred to as a first light projecting unit 110A, and the other light projecting unit 110 is referred to as a second light projecting unit 110B. The pair of first and second light projecting units 110 </ b> A and 110 </ b> B are arranged mirror-symmetrically with the optical axis of the light receiving unit 120 interposed therebetween. Since the light from the light projecting unit 110 is obliquely irradiated with respect to the optical axis of the light receiving unit 120, a shadow is generated on the three-dimensional measuring object S including irregularities. On the other hand, the occurrence of this shadow can be suppressed by arranging the pair of first and second light projecting units 110A and 110B in a mirror image symmetry.

  The measurement light sources 111 of the first and second light projecting units 110A and 110B are typically configured by halogen lamps that emit white light. The measurement light source 111 may be another light source such as a white LED (light emitting diode) that emits white light. Light emitted from the measurement light source 111 (hereinafter referred to as measurement light) is appropriately condensed by the condenser lens 113 and then enters the pattern generation unit 112. Here, the first and second light projecting units 110A and 110B are configured by a constant magnification optical system, and typical examples thereof include both-side telecentric lenses 114 and 115. By configuring the light projecting unit 110 with the telecentric lenses 114 and 115 on both sides, high measurement accuracy can be ensured. That is, in the telecentric optical systems 114 and 115, the image formation size of the pattern is constant regardless of the distance between the lens and the object S, and therefore the surface height of the object S that is a solid is not constant ( For example, even if it is an uneven surface), the pattern dimension does not change, and therefore it can be measured with high accuracy.

  The pattern generator 112 is preferably a DMD (digital micromirror device) for forming a two-dimensional array. Here, DMD is a kind of display element, and hundreds of thousands of micromirrors with a square of several μm are arranged like pixels, and the inclination of each micromirror can be changed independently. This characteristic allows light to be reflected in the direction of the optical axis (bright / ON) or deflected outward from the optical axis (dark / OFF) depending on the direction of the micromirror. Since this micromirror can be switched ON / OFF at a high speed of several kHz at the maximum, the gradation of brightness can be adjusted by PWM control. The illumination pattern generated by the pattern generation unit 112 can generate not only a stripe pattern (FIG. 9: multi-slit method) but also an arbitrary two-dimensional pattern. Examples of two-dimensional patterns include binary patterns, slit patterns, sine wave patterns, dot patterns, checker patterns, and two-dimensional code patterns.

  In the embodiment shown in FIG. 2, the pattern generation unit 112 employs a configuration that generates a two-dimensional pattern by transmission. However, as a modification, the pattern generation unit 112 may generate a two-dimensional pattern by reflection.

  The pattern generation unit 112 may be configured by an LCD (Liquid Crystal Display), LCOS (Liquid Crystal on Silicon), or a mask. The measurement light incident on the pattern generation unit 112 is converted into a preset pattern and a preset intensity (brightness) and is projected toward the object S. As described above, the measurement light emitted from the pattern generation unit 112 is a field of view in which the light receiving unit 120 can be observed and measured by the plurality of lenses 114 and 115 constituting the double-sided telecentric optical system employed as a constant magnification projection lens. After being converted into light having a larger diameter, the light is projected onto the measuring object S on the stage 140.

  The light receiving unit 120 includes a camera 121 and light receiving lenses 122 and 123 and is disposed above the stage 140. The light reflected by the measuring object S travels above the stage 140, is condensed and imaged by the plurality of lenses 122 and 123 of the light receiving unit 120, and the reflected light is received by the camera 121.

  The camera 121 is configured by a camera including an imaging element (light receiving element) 121a and a lens. In the embodiment, the light receiving lens unit of a telecentric optical system with a fixed magnification is employed with priority given to accuracy, but a zoom lens may be employed so that it can be used in a wide range of magnifications. The image sensor 121a is preferably composed of a monochrome CCD (charge coupled device), for example. Another imaging device such as a CMOS (complementary metal oxide semiconductor) image sensor may be employed as the imaging device 121a. From each pixel of the image sensor 121a, an analog electrical signal (hereinafter referred to as a light reception signal) corresponding to the amount of received light is output to the control board 150.

  When receiving the light projection pattern on the object S on the stage 140, the resolution is such that the minimum pattern width on the observation image at the minimum observation magnification (light reception magnification) includes at least one pixel, preferably a plurality of pixels. The imaging element, that is, the light receiving element 121a has. When the camera 121 has a zoom mechanism, a camera 121 having a resolution that includes at least one pixel, preferably a plurality of pixels, in the minimum pattern width when a pattern is received at the minimum magnification.

  In other words, the minimum magnification may be set by the light receiving lens so that at least one light receiving pixel, preferably a plurality of light receiving pixels, fits within the minimum pattern width at the minimum magnification, or the minimum pattern width at the minimum magnification of the light receiving lens. The magnification of the light projecting lens may be set so that at least one light receiving pixel, preferably a plurality of light receiving pixels, can be accommodated.

  When a color image sensor is used, each pixel needs to correspond to light reception for red, green, and blue, so the measurement resolution is lower than that of a monochrome image sensor, and a color filter is provided for each pixel. Sensitivity decreases because it is necessary. On the other hand, a monochrome image pickup device 121a is employed, and a color image is obtained by irradiating illumination corresponding to each of the LED light sources of RGB from a later-described illumination light output unit 130 in a time-division manner (sequential irradiation). Can be obtained. With such a configuration, it is possible to acquire a two-dimensional color texture image of a measurement object without reducing measurement accuracy.

  Of course, it goes without saying that a color image sensor may be used as the image sensor 121a as described above. In this case, although the measurement accuracy and sensitivity are reduced, it is not necessary to irradiate the RGB illumination from the illumination light output unit 130 in a time-sharing manner, and a color image can be acquired simply by irradiating white light, so the illumination optical system is simplified. Can be configured.

  On the control board 150, an A / D converter (analog / digital converter) and a FIFO (First In First Out) memory (not shown) are mounted. The light reception signal output from the camera 121 is sampled at a constant sampling period by the A / D converter of the control board 150 and converted into a digital signal based on control by the control unit 300. Digital signals output from the A / D converter are sequentially stored in the FIFO memory. The digital signal stored in the FIFO memory is sequentially transferred to the control PC 200 as pixel data.

  As shown in FIG. 1, the control PC 200 includes a CPU (Central Processing Unit) 210, a ROM (Read Only Memory) 220, a work memory 230, a storage device 240, and an operation unit 250. The operation unit 250 includes a keyboard and a pointing device. A mouse or a joystick is used as the pointing device.

  The ROM 220 stores a system program. The working memory 230 is composed of a RAM (Random Access Memory) and is used for processing various data. The storage device 240 is composed of a hard disk or the like. The storage device 240 stores an image processing program and a shape measurement program. The storage device 240 is used for storing various data such as pixel data supplied from the control board 150.

  The CPU 210 generates image data based on the pixel data given from the control board 150. The CPU 210 performs various processes on the generated image data using the work memory 230 and causes the display unit 400 to display an image based on the image data. Further, the CPU 210 gives a driving pulse to a stage driving unit 145 described later. The display unit 400 is preferably configured by a thin display, for example, an LCD panel or an organic EL (electroluminescence) panel.

  In FIG. 2, two directions orthogonal to each other within a plane (hereinafter referred to as a placement surface) on the stage 140 on which the measurement object S is placed are defined as an X direction and a Y direction, and arrows X and Y respectively. Show. A direction orthogonal to the mounting surface of the stage 140 is defined as a Z direction and is indicated by an arrow Z. A direction rotating around an axis parallel to the Z direction (shown by an arrow θ) is defined as a θ direction.

  The stage 140 includes an XY stage 141, a Z stage 142, and a θ stage 143. The XY stage 141 has an X direction moving mechanism and a Y direction moving mechanism. The Z stage 142 has a Z direction moving mechanism. The θ stage 143 has a θ direction rotation mechanism. The XY stage 141, the Z stage 142, and the θ stage 143 constitute a stage 140. The stage 140 further includes a fixing member (clamp) (not shown) that fixes the measurement object S to the placement surface. The stage 140 may further include a tilt stage having a mechanism that can rotate around an axis parallel to the mounting surface.

  The X-direction moving mechanism, Y-direction moving mechanism, Z-direction moving mechanism, and θ-direction rotating mechanism of the stage 140 are preferably provided with drive sources that can be independently driven and controlled, and stepping motors are typical examples of these drive sources. Can be mentioned. The X direction moving mechanism, Y direction moving mechanism, Z direction moving mechanism, and θ direction rotating mechanism of the stage 140 are driven by the stage operation unit 144 or the stage driving unit 145 of FIG.

  The user manually operates the stage operation unit 144 to move the mounting surface of the stage 140 relative to the light receiving unit 120 in the X direction, the Y direction, the Z direction, or rotate in the θ direction. Can be made. The stage driving unit 145 supplies the current to the stepping motor of the stage 140 based on the driving pulse given from the PC 200, thereby moving the stage 140 relative to the light receiving unit 120 in the X direction, Y direction, or Z direction. It can be moved or rotated in the θ direction.

  Here, as shown in FIG. 2, the central axis (optical axis) of the right and left light projecting units 110 and the central axis (optical axis) of the light receiving unit 120 intersect with each other on a focus plane where the focus of the stage 140 is best. In addition, the relative positional relationship among the light receiving unit 120, the light projecting unit 110, and the stage 140 is determined. Further, since the center of the rotation axis in the θ direction coincides with the center axis of the light receiving unit 120, when the stage 140 rotates in the θ direction, the measurement object does not deviate from the visual field, and the rotation axis is centered. It is designed to rotate within the field of view. Further, the X, Y, θ, and tilt moving mechanisms are supported with respect to the Z direction moving mechanism.

  In other words, even when the stage 140 is rotated or tilted in the θ direction, the observation center axis (optical axis) of the light receiving unit 120 and the movement axis in the Z direction do not shift. With such a stage mechanism, even when the position and orientation of the measurement object are changed, it is possible to move the stage 140 in the Z direction and capture and synthesize a plurality of images at different focal positions. . In the present embodiment, an electric stage that can be driven by a stepping motor has been described as an example. However, a manual stage that can be displaced only manually may be used.

  The control unit 300 includes a control board 310 and an illumination light source 320. A CPU (not shown) is mounted on the control board 310. The CPU of the control board 310 controls the light projecting unit 110, the light receiving unit 120, and the control board 150 based on a command from the CPU 210 of the PC 200.

  The illumination light source 320 includes, for example, three types of LEDs that emit red light (R), green light (G), and blue light (B). By controlling the luminance of the light emitted from each LED, light of an arbitrary color can be generated from the illumination light source 320. Light generated by the illumination light source 320 (hereinafter referred to as illumination light) is output from the ring-shaped illumination light output unit 130 through a light guide member (light guide). Note that the illumination light source 320 may be provided in the measurement unit 100 without providing the illumination light source 320 in the control unit 300. In this case, the illumination light output unit 130 is not provided in the measurement unit 100. When a color image is generated by irradiating the object S using the RGB illumination light output unit 130, for example, the light sources of the respective colors are sequentially switched at 300 Hz.

  The illumination light output unit 130 in FIG. 2 employs ring-shaped illumination having an annular shape centered on the observation center axis. The ring-shaped illumination light output unit 130 is connected to the RGB light source 320 (FIG. 2) via the light guide cable 132. Although not shown in FIG. 2, a collimator lens is disposed adjacent to each color LED of the RGB light source 320, and a bilateral telecentric lens system is disposed.

  The light distribution characteristic at the pupil narrowed by the collimator lens disposed adjacent to the RGB light source 320 is equal to the illuminance distribution on the light emitting surface of the light source 320. For example, if the illuminance distribution on the light emitting surface is uniform, the light distribution at the pupil The characteristics are uniform. That is, the illuminance distribution of the RGB light source 320 becomes the light distribution of the pupil of the collimator lens, while the light distribution of the RGB light source 320 becomes the illuminance distribution of the pupil of the collimator lens. Note that a surface emitting light source generally has a substantially uniform illuminance distribution over the entire light emitting surface. The double-sided telecentric lens system arranged after the collimator lens has a function of forming an image of the pupil of the collimator lens on the light incident portion of the light guide cable 132. That is, a double-sided telecentric lens system is arranged to generate the Kohler effect. The bundle of light whose light distribution characteristics are made uniform by the collimator lens maintains the uniformity of the light distribution characteristics in the process of passing through the both-side telecentric lens system, and the collected light passes through the light guide cable 132 and the illumination light output unit 130. To be supplied.

  Each of the plurality of optical fibers constituting the light guide cable has a characteristic of preserving the angle of light with respect to the axis of the optical fiber, so that the uniformity of the light distribution characteristic is maintained even in the light propagation in each optical fiber. The Randomness is preferably given by, for example, weaving the plurality of optical fibers, so that the object S can be illuminated in a state where slight illuminance unevenness of the RGB light source 320 is eliminated.

  The ring-shaped illumination light output unit 130 is disposed above the stage 140 so as to surround the light receiving unit 120. Accordingly, the illumination light is irradiated from the illumination light output unit 130 to the measurement object S so as not to cause a shadow, and a texture image is acquired. That is, by arranging the ring-shaped illumination around the optical axis of the light receiving unit 120, the measuring object S can be observed almost without shadow. Therefore, the bottom of the hole that cannot be observed only by the light projecting unit 110 that projects light obliquely with respect to the measurement object S can be observed by using the ring-shaped illumination output unit 130.

  3 and 4 are schematic views of the measuring object S in a state irradiated with light. In the example of FIGS. 3 and 4, the measuring object S has a hole Sh at the approximate center of the upper surface. Further, in FIGS. 3A, 3C and 4A, the shadow Ss is represented by hatching.

  FIG. 3A is a plan view of the measuring object S in a state irradiated with measurement light from the first light projecting unit 110A (FIG. 2), and FIG. FIG. As shown in FIGS. 3A and 3B, when the measurement object S is irradiated with the measurement light from the first light projecting unit 110A, the measurement light reaches the bottom of the hole Sh depending on the depth of the hole Sh. Does not reach and a shadow Ss occurs. Therefore, a part of the measuring object S cannot be observed.

  FIG. 3C is a plan view of the measuring object S in a state irradiated with the measurement light from the second light projecting unit 110B (FIG. 2), and FIG. 3D is a view of B in FIG. FIG. As shown in FIGS. 3C and 3D, when the measurement object S is irradiated with the measurement light from the second light projecting unit 110B, the measurement light reaches the bottom of the hole Sh depending on the depth of the hole Sh. Does not reach and a shadow Ss occurs. Therefore, a part of the measuring object S cannot be observed.

  FIG. 4A is a plan view of the measuring object S in a state where measurement light from both the first and second light projecting units 110A and 110B is irradiated, and FIG. 4B is a plan view of FIG. It is a CC sectional view taken on the line of FIG. As shown in FIGS. 4A and 4B, when the measuring object S is irradiated with the measurement light from both the first and second light projecting units 110A and 110B, the first or second light projecting unit. Compared with the case where the measurement object S is irradiated with the measurement light from 110A or 110B, the measurement light that does not reach the bottom of the hole Sh is reduced, and thus the generated shadow Ss is reduced. Therefore, the portion of the measuring object S that can be observed increases.

  FIG. 4C is a plan view of the measuring object S in a state irradiated with illumination light from the illumination light output unit 130 in FIG. 2, and FIG. 4D is a DD line in FIG. It is sectional drawing. As shown in FIGS. 4C and 4D, since the illumination light is irradiated from substantially right above the measurement object S, the illumination light reaches the bottom of the hole Sh regardless of the depth of the hole Sh. To do. Therefore, most of the measuring object S can be observed.

  The image of the measuring object S irradiated with the measuring light from the first light projecting unit 110A and the image of the measuring object S irradiated with the measuring light from the second light projecting unit 110B are displayed side by side on the display unit 400. It may be displayed (two-screen display).

  The PC (personal computer) 200 receives camera image data transmitted from the light receiving unit 120 (control board 150) and executes processing. The display unit 400 functions as a monitor for controlling the optical microscope 500, displays a camera-captured image and a GUI for a control program, and can be operated by a user using input means such as a mouse and a keyboard.

  FIG. 5 is a diagram illustrating an example of a GUI (Graphical User Interface) that displays an image on two screens. As shown in FIG. 5, the display unit 400 is provided with two image display areas 410 and 420 arranged side by side. When displaying an image on two screens, the measurement light is alternately irradiated to the measurement object S from the light projecting units 110A and 110B. In the image display area 410, an image of the measurement object S when the measurement light is irradiated from the first light projecting unit 110A is displayed. In the image display area 420, an image of the measurement object S when the measurement light is irradiated from the second light projecting unit 110B is displayed. Thereby, the user can distinguish and recognize the image of the measuring object S when the measurement light is irradiated by each of the first and second light projecting units 110A and 110B.

  Note that the frequency of switching of the measurement light from the first and second light projecting units 110A and 110B is set to a value (for example, several Hz or more) that allows the user to feel at least a moving image. Therefore, the user observes that the measurement object 100 is irradiated with the measurement light from both the light projecting units 110A and 110B substantially simultaneously and the moving image is updated at the same time. That is, each of the images obtained by irradiating the measurement light from the light projecting units 110A and 110B is recognized by the user like a moving image (live image).

  Still referring to FIG. 5, two brightness setting bars 430 and 440 are displayed on the display unit 400. The brightness setting bar 430 includes a slider 430s that can move in the horizontal direction. The brightness setting bar 440 includes a slider 440s that can move in the horizontal direction. The position of the slider 430s on the brightness setting bar 430 corresponds to the brightness of the measurement light emitted from the first light projecting unit 110A or the camera exposure time when an image is taken with the measurement light from 110A. The position of the slider 440s on the brightness setting bar 440 corresponds to the brightness of the measurement light emitted from the second light projecting unit 110B or the camera exposure time when an image is taken with the measurement light from 110B.

  The user operates the operation unit 250 (typically a mouse) of the PC 200 shown in FIG. 1 to move the slider 430s of the brightness setting bar 430 in the horizontal direction, thereby emitting the light from the first light projecting unit 110A. The measurement light brightness or the camera exposure time corresponding to the first light projecting unit 110A can be changed, and the result is reflected in the display image of the display unit 400 in real time. Similarly, the user operates the operation unit 250 (typically a mouse) to move the slider 440s of the brightness setting bar 440 in the horizontal direction, and thereby the measurement emitted from the second light projecting unit 110B. The brightness of the light or the camera exposure time corresponding to the second light projecting unit 110B can be changed, and the result is reflected in the display image of the display unit 400 in real time.

  As described above, in the image display areas 410 and 420, images of the measurement object S when the measurement light is irradiated by each of the light projecting units 110A and 110B are displayed so as to be aligned. Therefore, the user moves the positions of the sliders 430 s and 440 s of the brightness setting bars 430 and 440 while viewing the image of the measurement object S displayed in the image display areas 410 and 420, respectively. The brightness of the measurement light emitted from each of 110A and 110B or the camera exposure time corresponding to each light projecting unit can be adjusted appropriately.

  Further, there is a correlation between the appropriate brightness of the measurement light emitted from the light projecting units 110A and 110B and the appropriate brightness of the illumination light emitted from the illumination light output unit 130 or the camera exposure time corresponding to each illumination. There may be. In this case, the brightness of the measurement light emitted from each of the light projecting units 110 </ b> A and 110 </ b> B or the camera exposure time corresponding to each light projecting unit is the brightness or illumination of the illumination light emitted from the illumination light output unit 130. It may be automatically adjusted based on the camera exposure time corresponding to the light.

  Alternatively, based on the brightness of the illumination light emitted from the illumination light output unit 130 or the camera exposure time corresponding to the illumination light, the brightness of the measurement light emitted from each of the light projecting units 110A and 110B or the respective projections. An adjustment guide for making the camera exposure time corresponding to the light part appropriate may be displayed on the display part 400. In this case, the user moves the positions of the sliders 430s and 440s of the brightness setting bars 430 and 440 based on the adjustment guide, respectively, so that the brightness of the measurement light emitted from each of the light projecting units 110A and 110B. Or the camera exposure time corresponding to each light projection part can be adjusted appropriately.

  If the light irradiation direction is different, the light reflection direction is also different, so that the brightness of the resulting image varies depending on the light irradiation direction even in the same region. That is, the brightness of illumination suitable for measurement and the exposure time of the image sensor vary depending on the irradiation direction. In this embodiment, it is possible to individually adjust the brightness of each image picked up by irradiating light from the plurality of light projecting units 110A and 110B, so that the appropriate illumination brightness or exposure is provided for each irradiation direction. You can set the time. In addition, since the image whose brightness is being adjusted is displayed while being updated in the image display areas 410 and 420, the brightness can be adjusted while checking the adjusted image. At this time, in the images displayed in the image display areas 410 and 420, by displaying the portion that is too bright and overexposed or the portion that is too dark and underexposed so as to be identifiable, it is possible for the user. It is also possible to display more clearly whether or not the brightness can be adjusted appropriately.

Shape measurement of measurement object :
(1) Shape measurement by triangulation method (Fig. 6) :
In the measuring unit 100, the three-dimensional shape of the measuring object S is measured by a triangulation method. FIG. 6 is a diagram for explaining the principle of the triangulation system. As shown in FIG. 6, an angle α between the optical axis of the measurement light emitted from the light projecting unit 110 and the optical axis of the measurement light incident on the light receiving unit 120 (the optical axis of the light receiving unit 120) is set in advance. The The angle α is larger than 0 degree and smaller than 90 degrees.

  When the measurement object S is not placed on the stage 140, the measurement light emitted from the light projecting unit 110 is reflected by the point O on the placement surface of the stage 140 and enters the light receiving unit 120. On the other hand, when the measuring object S is placed on the stage 140, the measuring light emitted from the light projecting unit 110 is reflected by the point A on the surface of the measuring object S and enters the light receiving unit 120.

  When the distance in the X direction between the point O and the point A is indicated by “d”, the height h of the point A of the measuring object S with respect to the mounting surface of the stage 140 is represented by h = d ÷ tan (α). Given. The CPU 210 of the PC 200 in FIG. 1 measures the distance d between the point O and the point A in the X direction based on the pixel data of the measurement object S given by the control board 150. Further, the CPU 210 calculates the height h of the point A on the surface of the measuring object S based on the measured distance d. By calculating the heights of all points on the surface of the measuring object S, the three-dimensional shape of the measuring object S can be measured. However, in order to measure all points on the surface of the measuring object S, processing such as raster scanning of the measuring light (measuring points) is required for the entire field of view of the measuring object S. A great deal of time is required for processing.

  Therefore, a light cutting method in which a line-shaped irradiation pattern is applied to the surface of the measurement object S and scanned in one direction, and a fringe projection method in which a stripe-shaped irradiation pattern is applied to the surface of the measurement object S and is scanned in one direction. Is well known. Then, the three-dimensional shape of the object S is displayed on the display unit by mapping the object image obtained by applying uniform illumination to the measurement object S as surface texture information with respect to the three-dimensional shape data acquired in this way. 400 can be displayed. Illustrative examples of irradiation patterns that can be employed in the embodiment for obtaining three-dimensional shape data are described below. Here, if the typical example of mapping is concretely explained, the 3D shape measurement data and the 2D texture image are acquired by the same camera, the data of each pixel of the 2D texture image, and the 3D This means that a three-dimensional texture image is generated by associating data of the same pixel of the height image obtained by the shape measurement.

(2) First irradiation pattern of measurement light (FIG. 7: line projection method) :
FIG. 7 is a diagram for explaining a first pattern of measurement light. FIG. 7A shows a state in which the measuring object S on the stage 140 is irradiated with the measuring light from the light projecting unit 110. FIG. 7B shows a plan view of the measuring object S irradiated with the measuring light. As shown in FIG. 7A, as the first pattern, measurement light having a linear cross section parallel to the Y direction (hereinafter referred to as linear measurement light) is emitted from the light projecting unit 110. In this case, as shown in FIG. 7B, the portion of the line-shaped measurement light irradiated on the stage 140 and the portion of the line-shaped measurement light irradiated on the surface of the measurement object S are the same as those of the measurement object S. They are shifted from each other in the X direction by a distance d corresponding to the height h of the surface. Therefore, the height h of the measuring object S can be calculated by measuring the distance d.

  When a plurality of portions along the Y direction on the surface of the measuring object S have different heights, the height h of the plurality of portions along the Y direction is measured by measuring the distance d for each portion. Can be calculated.

  Further, the CPU 210 in FIG. 1 measures the distance d for a plurality of portions along the Y direction at one position in the X direction, and then scans the line-shaped measurement light parallel to the Y direction in the X direction. The distance d is measured for a plurality of portions along the Y direction at other positions in the direction. Thereby, the height h of the several part of the measuring object S along the Y direction in the several position of a X direction is calculated. The height h of all points on the surface of the measuring object S can be calculated by scanning the line-shaped measurement light in the X direction over a range wider than the observation of the light receiving unit 120 and the measurable field of view. Thereby, the three-dimensional shape data of the measuring object S can be acquired.

(3) Second irradiation pattern of measurement light (FIG. 8: sine wave phase shift method) :
FIG. 8 is a diagram for explaining a second pattern of measurement light. As shown in FIG. 8, as the second pattern, measurement light having a linear cross section parallel to the Y direction and having a pattern in which the intensity changes sinusoidally in the X direction (hereinafter referred to as sinusoidal measurement light). ) Is emitted from the light projecting unit 110 a plurality of times (in this example, four times). In the sine wave phase shift method, the height h can be obtained by at least three photographings. As will be described later, if the phase is shifted by 90 degrees (π / 2) and photographing is performed four times, there is an advantage that the calculation formula becomes very simple.

  FIG. 8A shows sinusoidal measurement light emitted for the first time. The intensity of the sinusoidal measurement light emitted for the first time has an initial phase φ at an arbitrary position PO on the surface of the measurement object S. When the sinusoidal measurement light is emitted, the light reflected by the surface of the measurement object S is received by the light receiving unit 120. The intensity of the received light is measured based on the pixel data of the measuring object S. The intensity (luminance) of light reflected by an arbitrary portion PO on the surface of the measuring object S is assumed to be I1.

  FIG. 8B shows sinusoidal measurement light emitted for the second time. The intensity of the sinusoidal measurement light emitted for the second time has a phase (φ + π / 2) at an arbitrary position PO on the surface of the measuring object S. When the sinusoidal measurement light is emitted, the light reflected by the surface of the measurement object S is received by the light receiving unit 120. The intensity of the received light is measured based on the pixel data of the measuring object S. The intensity (luminance) of the light reflected by the portion PO on the surface of the measuring object S is I2.

  FIG. 8C shows sinusoidal measurement light emitted for the third time. The intensity of the sinusoidal measurement light emitted for the third time has a phase (φ + π) at an arbitrary position PO on the surface of the measurement object S. When the sinusoidal measurement light is emitted, the light reflected by the surface of the measurement object S is received by the light receiving unit 120. The intensity of the received light is measured based on the pixel data of the measuring object S. The intensity (luminance) of the light reflected by the portion PO on the surface of the measuring object S is I3.

FIG. 8D shows sinusoidal measurement light emitted for the fourth time. The intensity of the fourth sinusoidal measurement light has a phase (φ + 3π / 2) at an arbitrary position PO on the surface of the measuring object S. When the sinusoidal measurement light is emitted, the light reflected by the surface of the measurement object S is received by the light receiving unit 120. The intensity of the received light is measured based on the pixel data of the measuring object S. The intensity of the light reflected by the portion P _O on the surface of the measuring object S (luminance) and I4.

The initial phase φ is given by φ = tan ⁻¹ [(I1−I3) / (I2−I4)]. By using this four-point method, it is not necessary to know the amplitude and luminance center of the original sine wave, and the height h of an arbitrary part of the measuring object S is obtained by obtaining the initial phase φ from the measured I1 to I4. Is calculated. More specifically, at an arbitrary position PO on the surface of the measurement object S, the initial phase φo when the object S does not exist and the initial phase φs shifted by the presence of the object S are shown. The height h is calculated by obtaining the phase difference (corresponding to the distance d in FIG. 6). That is, according to this method, the initial phase φ of all portions of the measuring object S can be calculated quickly and easily by measuring the intensity of light four times. The initial phase φ can be calculated by irradiating measurement light with different phases at least three times and measuring the intensity (luminance) of the received light. Then, by calculating the height h of all the parts on the surface of the measuring object S, the three-dimensional shape of the measuring object S can be measured. This sine wave phase shift method has an advantage that three-dimensional shape data can be acquired at a high speed because the number of shots is at least three and stereoscopic information can be obtained with a small number of shots.

(4) Third irradiation pattern of measurement light (FIG. 9: multi-slit method) :
FIG. 9 is a diagram for explaining a third pattern of measurement light. As shown in FIG. 9, as the third pattern, there are a plurality of fine line-shaped pattern measuring lights (hereinafter referred to as striped measuring lights) having a linear cross section parallel to the Y direction and aligned in the X direction. The light is emitted from the light projecting unit 110 a plurality of times (in this example, 16 times). In other words, photographing is performed a plurality of times by moving the illumination pattern at a pitch narrower than the slit width. In the embodiment, a combination of the multi-slit method and a spatial code method described later is employed.

  In the striped measurement light, a linear bright portion parallel to the Y direction and a linear dark portion parallel to the Y direction are periodically arranged in the X direction. Here, when the pattern generation unit 112 is a DMD, the dimension of the micromirror is set to one unit.

  The width of each bright portion of the striped measurement light in the X direction is, for example, 3 units, and the width of each dark portion of the striped measurement light in the X direction is, for example, 13 units. In this case, the period of the striped measurement light in the X direction is 16 units. The unit of the bright part and the dark part differs depending on the configuration of the pattern generation unit 112 in FIG. For example, when the pattern generation unit 112 is a liquid crystal, one unit is the size of one pixel.

  When the first striped measurement light is emitted, the light reflected by the surface of the measurement object S is received by the light receiving unit 120. The intensity of the received light is measured based on the pixel data of the first captured image of the measuring object S. FIG. 9A is a first photographed image of the measuring object S corresponding to the first striped measurement light.

  The second striped measurement light has a pattern in which the bright portion and the dark portion are moved by one unit in the X direction from the first striped measurement light. When the second striped measurement light is emitted, the light reflected by the surface of the measurement object S is received by the light receiving unit 120. The intensity of the received light is measured based on the pixel data of the second captured image of the measuring object S.

  The third striped measurement light has a pattern in which the bright part and the dark part are moved by one unit in the X direction from the second striped measurement light. By emitting the third striped measurement light, the light reflected by the surface of the measuring object S is received by the light receiving unit 120. The intensity of the received light is measured based on the pixel data of the third captured image of the measuring object S.

  By repeating the same operation, the intensity of the light corresponding to the 4th to 16th striped measurement light is measured based on the pixel data of the 4th to 16th captured images of the measuring object S, respectively. The striped measurement light whose period in the X direction is 16 units is emitted 16 times, so that the entire surface of the measurement object S is irradiated with the striped measurement light. FIG. 9B is a seventh captured image of the measuring object S corresponding to the seventh striped measurement light. FIG. 9C is a thirteenth captured image of the measuring object S corresponding to the thirteenth striped measurement light.

  FIG. 10 is a diagram illustrating the relationship between the timing (numbered number) at which an image is captured and the intensity of received light in a specific portion of the measurement object S. The horizontal axis in FIG. 10 indicates the number of the captured image, and the vertical axis indicates the intensity of the received light. As described above, the first to sixteenth captured images are generated for the measuring object S. In addition, the intensity (luminance) of light corresponding to each pixel of the generated first to sixteenth captured images is measured.

  As shown in FIG. 10, a scatter diagram is obtained by illustrating the light intensity (luminance) of each part in the image corresponding to the number of the captured image. By fitting, for example, a Gaussian curve, a spline curve or a parabola to the obtained scatter diagram, it is possible to estimate the number (number) of the photographed image when the light intensity becomes maximum with an accuracy of less than 1. . In the example of FIG. 10, the 9.38th photographed image between the ninth and the tenth is shown by the curve indicated by the fitted dotted line (such a photographed image is not actually present but exists only for calculation estimation). In this case, it is estimated that the light intensity becomes maximum.

  In addition, the maximum value of the light intensity can be estimated from the fitted curve. Based on the number of the photographed image in which the light intensity estimated in each part of the measurement object S takes the maximum value, this value is multiplied by the value of how many μm each micromirror unit corresponds to on the object S. Thus, the distance corresponding to “d” in FIG. 6 is obtained, and the height h of each part of the measuring object S can be calculated based on this value d (h = d ÷ tan (α)). . According to this method, since the three-dimensional shape of the measuring object S can be measured based on the intensity of light having a sufficiently large S / N (signal / noise) ratio, the accuracy of the shape measurement of the measuring object S is improved. Can be made.

  In the shape measurement of the measuring object S using a periodic projection pattern of sinusoidal measuring light or striped measuring light, the relative height (relative height) of each part of the surface of the measuring object S is measured. Value) is measured. This is because individual periodic fringes cannot be distinguished and there is an uncertainty corresponding to an integral multiple of one fringe period (2π), so that the absolute phase cannot be obtained. Therefore, a known unwrapping process is performed on the measured height data based on the assumption that the height of one part of the measuring object S and the height of the part adjacent to the part continuously change. It may be done.

  According to this multi-slit method, the number of shots is 16 in the case of a 16-pixel cycle, a slit light with a width of 3 pixels, and a moving pitch of 1 pixel. Since data with high luminance is always used when obtaining an imaging timing (which image is the maximum) for each pixel by interpolation calculation, it is easy to stably improve accuracy.

(5) Fourth irradiation pattern of measurement light (FIG. 11: spatial code method) :
FIG. 11 is a diagram for explaining a fourth pattern of measurement light. As shown in FIG. 11, as the fourth pattern, measurement light having a linear cross section parallel to the Y direction and having a bright portion and a dark portion aligned in the X direction (hereinafter referred to as code-like measurement light) is used. The light is emitted from the light projecting unit 110 a plurality of times (in this example, four times). The ratio of the bright part and the dark part of the code-like measurement light is 50%.

  In the embodiment, the surface of the measuring object S is divided into a plurality of regions (16 in the example of FIG. 11) in the X direction. Hereinafter, the areas of the measurement object S in the X direction divided into a plurality of parts are referred to as first to sixteenth areas, respectively.

  FIG. 11A shows the code-like measurement light emitted for the first time. The code-shaped measurement light emitted for the first time has a bright portion that is irradiated onto the first to eighth regions of the measurement object S. Moreover, the code-shaped measurement light emitted for the first time has a dark part irradiated on the ninth to sixteenth regions of the measuring object S. Thereby, in the code-like measurement light emitted for the first time, the bright portion and the dark portion are parallel to the Y direction and aligned in the X direction. Further, the ratio of the bright part and the dark part of the code-like measurement light emitted for the first time is 50%.

  FIG. 11B shows the code-like measurement light emitted for the second time. The code-like measurement light emitted for the second time has a bright portion that is irradiated onto the fifth to twelfth regions of the measurement object S. Moreover, the code-like measurement light emitted for the second time has dark portions that are irradiated to the first to fourth and thirteenth to sixteenth regions of the measuring object S. Thereby, in the code-like measurement light emitted for the second time, the bright part and the dark part are parallel to the Y direction and aligned in the X direction. Moreover, the ratio of the bright part and the dark part of the code-like measurement light emitted for the second time is 50%.

  FIG. 11C shows the code-like measurement light emitted for the third time. The code-like measurement light emitted for the third time has bright portions that are irradiated on the first, second, seventh to tenth, fifteenth and sixteenth regions of the measurement object S. Moreover, the code-like measurement light emitted for the third time has dark portions that are irradiated on the third to sixth and the eleventh to fourteenth regions of the measurement object S. Thereby, in the code-like measurement light emitted for the third time, the bright part and the dark part are parallel to the Y direction and aligned in the X direction. Further, the ratio of the bright part and the dark part of the code-like measurement light emitted for the third time is 50%.

  FIG. 11D shows the code-like measurement light emitted for the fourth time. The coded measurement light emitted for the fourth time has a bright portion that is irradiated on the first, fourth, fifth, eighth, ninth, twelfth, thirteenth, and sixteenth regions of the measurement object S. . In addition, the coded measurement light emitted for the fourth time is a dark portion irradiated on the second, third, sixth, seventh, tenth, eleventh, fourteenth and fifteenth regions of the measuring object S. Have Thereby, in the code-like measurement light emitted for the fourth time, the bright part and the dark part are parallel to the Y direction and aligned in the X direction. Further, the ratio of the bright part and the dark part of the code-like measurement light emitted for the fourth time is 50%.

  Logic “1” is assigned to the bright part of the code-like measurement light, and logic “0” is assigned to the dark part of the code-like measurement light. In addition, the logic arrangement of the first to fourth code-like measurement lights irradiated on each region of the measurement object S is referred to as a code. In this case, the first region of the measurement object S is irradiated with the code-shaped measurement light with the code “1011”. As a result, the first region of the measuring object S is encoded to the code “1011”.

  The second area of the measurement object S is irradiated with code-shaped measurement light with a code “1010”. As a result, the second region of the measuring object S is encoded to the code “1010”. The third region of the measuring object S is irradiated with code-shaped measurement light with a code “1000”. As a result, the third region of the measuring object S is encoded with the code “1000”. Similarly, the 16th region of the measuring object S is irradiated with the code-shaped measurement light with the code “0011”. Thus, the sixteenth region of the measuring object S is encoded with the code “0011”.

  In this way, between the adjacent regions of the measurement object S, the code-shaped measurement light is irradiated to the measurement object S a plurality of times so that any digit of the code differs by “1”. That is, the code-shaped measurement light is applied to the measurement object S a plurality of times so that the bright portion and the dark portion change into a gray code shape.

  Light reflected by each region on the surface of the measuring object S is received by the light receiving unit 120. Coded measurement light images are generated from the received light (in this example, four images), and the sign of each region is measured from these images. The distance corresponding to “d” in FIG. 6 is obtained by obtaining the difference between this code and the code when the measurement object S does not exist for each region. At this time, the absolute value of “d” is obtained from the characteristic of the coding method that the above-mentioned code appears only once in the X-axis direction in the image. From here, the absolute height (the absolute value of the height) of the region of the measuring object S is calculated. By calculating the height of all regions on the surface of the measuring object S, the three-dimensional shape of the measuring object S can be measured.

In the above description, the surface of the measuring object S is divided into 16 regions in the X direction, and the code-shaped measurement light is emitted from the light projecting unit 110 four times. However, the present invention is not limited to this. The surface of the measurement object S may be divided into 2 ^N regions (N is a natural number) in the X direction, and the code-shaped measurement light may be emitted N times from the light projecting unit 110. In the above description, N is set to 4 for easy understanding. In the shape measurement process in the present embodiment, N is set to 8, for example. Therefore, the surface of the measuring object S is divided into 256 regions in the X direction.

  In the shape measurement of the measuring object S using the code-like measurement light, the minimum resolution at which the stripe can be separated as a code, that is, the distance corresponding to one pixel of light reception is the minimum resolution. Therefore, when the number of pixels in the field of view in the X direction of the light receiving unit 120 is 1024 pixels, a measurement object S having a height of, for example, 10 mm can be measured with a resolution of 10 mm ÷ 1024≈10 μm. In the embodiment, three-dimensional shape data is generated by using an algorithm that combines the shape measurement using the code-shaped measurement light (absolute value is obtained but the resolution is insufficient) and the multi-slit method described above. As a modification, three-dimensional shape data may be generated using an algorithm that combines the above-described code method and sine wave phase shift method. Only the relative value is obtained, but the absolute value of the distance d of the measuring object S can be calculated with higher resolution by the combination of the multi-slit method or the sine wave phase shift method and the code method with high resolution.

  In particular, in the shape measurement of the measuring object S using the striped measurement light in FIG. 9, the resolution can be 1/100 pixels. The resolution of 1/100 pixels is that the surface of the measuring object S is divided into about 100,000 areas in the X direction when the number of pixels of the field of view in the X direction of the light receiving unit 120 is 1024 pixels (that is, N≈ 17).

  According to the shape measuring method using the code-shaped measuring light, there is an advantage that the absolute phase can be obtained, but the resolution is relatively low. Therefore, by combining the spatial code method that can know the absolute phase, the sine wave phase shift method and the multi-slit method that can only obtain the relative phase, a measurement method that can obtain an absolute value with high resolution and Become. That is, the absolute value of the height of the measuring object S can be calculated with higher resolution by combining the shape measurement using the code-shaped measurement light and the shape measurement using the striped measurement light.

  The above-described method of scanning the line-shaped measurement light on the measurement object (first irradiation pattern: FIG. 7) is generally called a light cutting method. On the other hand, a method of irradiating sinusoidal measurement light (second irradiation pattern: FIG. 8), a method of irradiating striped measurement light (third irradiation pattern: FIG. 9), or a method of irradiating code-shaped measurement light (4th irradiation pattern: FIG. 11) is classified into the pattern projection method. Among pattern projection methods, the method of irradiating sinusoidal measurement light and the method of irradiating striped measurement light are classified as phase shift methods, and the method of irradiating code-like measurement light is classified as a spatial code method. Is done.

  In the sine wave phase shift method (second and third irradiation patterns: FIGS. 8 and 9), the measurement object S does not exist when a sine wave that is a periodic projection pattern or a plurality of slit lights is irradiated. From the phase difference calculated based on the received light amount reflected from the reference height position in the case and the phase difference calculated based on the received light amount reflected from the surface of the measurement object S when the measurement object exists The height of the measuring object S is obtained. Although the phase shift method cannot distinguish individual periodic fringes and has an uncertainty corresponding to an integral multiple of one fringe period (2π), there is a drawback that the absolute phase cannot be obtained. Compared to the cutting method, the number of images to be acquired is small, so that the measurement time is relatively short and the measurement resolution is high. On the other hand, in the spatial code method (fourth irradiation pattern: FIG. 11), a code that is changed due to the presence of the object S is obtained for each region of the object, and this code and a code when the object S does not exist The absolute height of the object can be obtained by obtaining the difference between and for each region. The spatial code method can measure with a relatively small number of images and has an advantage that the absolute height can be obtained. However, the measurement resolution is limited compared to the sine wave phase shift method.

  Each of these projection methods has disadvantages and advantages, but both use the principle of triangulation. In the embodiment, as described above, an algorithm in which the third irradiation pattern (FIG. 9: multi-slit method) and the spatial code method (FIG. 11) are combined is employed, but the sine wave phase is used instead of the multi-slit method. An algorithm combining the sine wave phase shift method and the spatial code method may be adopted by adopting the shift method.

  The optical microscope 500 of the first embodiment picks up an image by using a ring-shaped RGB illumination light output unit 130 that emits light directly below and a light projecting unit 110 that emits light obliquely. When only observing the object S, the illumination of the RGB illumination light output unit 130 and the light projecting unit 110 can be appropriately selected or used together to observe the object S in an optimal illumination state. When generating a 3D texture image, a color image (two-dimensional texture image) captured using the ring-shaped RGB illumination light output unit 130 is acquired, and three-dimensional solid data measured using the light projecting unit 110 is obtained. get. Then, the 3D texture image generated by mapping the 2D texture image to the 3D solid data is displayed on the display unit 400. The 3D texture image displayed on the display unit 400 faithfully reproduces the three-dimensional contour when the measuring object S is viewed, and an arbitrary program in which this realistic 3D texture image data is incorporated into the PC 200 is used. Observation from any direction, measurement and analysis can be performed.

  In other words, in a conventional optical microscope, what can display a beautiful image of a measurement object on a monitor is a two-dimensional (2D) image, so that the stereoscopic effect and realism are poor. On the other hand, according to the optical microscope 500 of the embodiment, a beautiful three-dimensional (3D) texture image is displayed on the monitor, so that a real sense can be provided to the user who observes the image. Therefore, the optical microscope 500 according to the embodiment gives a surprise to a user who sees that the realistic 3D texture image is displayed instantaneously, that the monitor display of the realistic 3D texture image is instantaneously performed. In addition, it is possible to give a surprise as if the object S was taken in the display unit 400 of the PC 200 as it is.

  In the embodiment, an optical image of the object S is formed with extremely low distortion by employing a telecentric optical system for the light projecting unit 110 and the light receiving unit 120, and a monochrome image sensor is employed for the image sensor 121a. Thus, a high-sensitivity and high-quality image with a high S / N ratio can be acquired. Then, highly accurate three-dimensional shape data can be generated from this image. Similarly, an illumination image (2D texture image) by the illumination light output unit 130 can also be acquired with high image quality via the common light receiving unit 120. A high-quality 3D (three-dimensional) texture image can be generated by combining the three-dimensional shape data and 2D (two-dimensional texture image). It goes without saying that this high-quality 3D texture image has the aforementioned reality.

  FIG. 12 is a diagram for explaining the operational effect when the double-sided telecentric lenses 114 and 115 are employed in the light projecting unit 110. On the stage 140, the bundle of light from the light projecting unit 110 generates a rectangular projection image as shown in the lower part of FIG. 12, and the horizontal lines of the pixels of the two-dimensional array (pattern generating unit 112) and the light receiving pixels. Parallelism with the horizontal line is maintained. Therefore, when the projection pattern is viewed with the light receiving pixels, the continuity of the minimum pattern width on the screen can be maintained. This facilitates the association between the projection pattern on the stage 140 and the observation image.

  On the other hand, when an optical lens that is not a telecentric lens is disposed in the light projecting unit 110, a trapezoidal projection image is obtained as the light projecting unit 110 is disposed obliquely with respect to the stage 140. The line on the stage 140 that projects the horizontal lines of the pixels of the array (pattern generation unit 112) and the horizontal line on the observation image, that is, the horizontal lines of the light receiving pixels are not parallel. Then, a trapezoidal distortion occurs in which the magnification is relatively low on the side close to the light projecting unit 110 and the magnification is relatively high on the side far from the light projecting unit 110, thereby irradiating from the light projecting unit 110. As a result of the magnification changing along the direction of the light, the uniformity of the pattern width on the observed image cannot be maintained.

  Further, the area of the projection pattern of the stage 140 is larger than the observation area when the observation magnification is low. That is, the projection pattern has a margin with respect to the observation area when the magnification is low. As a result, it is possible to always obtain a projection pattern on the object to be measured, which is installed on the stage 140 at any magnification and has a height corresponding to the measurement depth.

  Referring to FIG. 19, when the light reception magnification is increased at a constant light projection magnification, the number of adjacent pixels having an estimated phase peak is increased, and as a result, the luminance change for each image order is reduced. As a result, the possibility that a relatively close phase peak is estimated increases. In other words, in pattern projection measurement, when three-dimensional measurement is performed by performing phase calculation on each pixel of an image acquired by imaging a plurality of patterns projected by changing the phase, the phase change of the projection pattern is fine. This is limited by the pixel pitch of the pattern generation unit. When a variable magnification optical system is used on the light receiving side and a constant magnification optical system is used on the light projecting side, the image is actually captured when the projection pattern projected by the pattern generation unit is changed as the magnification on the light receiving side becomes higher. The projection pattern will change greatly. In other words, the higher the magnification, the more difficult it is to change the phase of the projected projection pattern to be picked up, making it difficult to distinguish the phase peaks between adjacent pixels, and errors are likely to occur. This means that a vertical line system error is likely to occur in the height result. In order to avoid this, in the image processing, it is preferable to add a process of changing the parameters of the systematic error removal filter (for example, a horizontal Gaussian filter) according to the light reception magnification. That is, since the luminance change for each image order in adjacent light receiving pixels becomes large, the swell width changes as a result. In order to eliminate this, it is preferable to greatly change the horizontal direction of the filter, for example, the Gaussian width and the standard deviation as the light receiving magnification increases.

  Next, another embodiment of the present invention will be described. The same reference numerals are given to the same elements as those in the first embodiment, and the description thereof will be omitted.

Second Example (FIGS. 13 and 14) :
Referring to FIG. 13, the optical microscope 520 of the second embodiment is different from the optical microscope 500 of the first embodiment in the following two points. First, regarding the light projecting unit 110, the light emitted from the measurement light source 111 is reflected by the pattern generation unit (two-dimensional array) 112 to generate a two-dimensional pattern. The use of reflection to generate a two-dimensional pattern has the advantage that the width of the microscope 520 can be reduced, which allows the optical microscope 520 capable of three-dimensional measurement to be miniaturized.

  Secondly, the light receiving unit 120 includes a first light receiving unit 120A having a relatively low magnification and a second light receiving unit 120B having a relatively high magnification, and the first and second light receiving units 120A. , 120B are preferably composed of telecentric lenses.

  The light receiving element 121a of the first light receiving unit 120A with a low magnification is arranged orthogonal to the observation optical axis 125. The light receiving element 121a of the high-magnification second light receiving unit 120B is arranged orthogonal to a branch observation axis 128 that branches off from the observation optical axis 125 by a branch mirror 127 arranged on the observation optical axis 125 and extends in the lateral direction. ing. Three or more light receiving units 120 having different magnifications may be formed by forming a plurality of branch observation axes 128 by arranging a plurality of branch mirrors 127 on the observation optical axis 125.

  When a plurality of light receiving units 120 having different magnifications are configured by a telecentric lens, high telecentricity can be realized in the light receiving unit 120 of each magnification, so that high accuracy can be ensured in height measurement at each magnification. .

  Further, by adopting a high-resolution (high-density) light-receiving element as the light-receiving element 121a of the high-magnification second light-receiving unit 120B, the low-magnification first light-receiving unit 120A and the high-magnification second light-receiving unit 120B. Can provide a wide magnification range.

  This point will be described in a specific example with reference to FIG. 14. When the resolution of the observation image is 1000 pixels horizontal, for example, if an element of 2000 pixels horizontal is used as the light receiving element 121 a, it is illustrated at the top of FIG. As described above, the observation image of the light receiving element 121a is thinned out to obtain a 0.5 times observation image. As shown in the second figure from the top in FIG. 14, an image for 1000 pixels at the center of the light receiving element 121a is cut out to generate an observation image, whereby a 1 × observation image can be obtained. As illustrated at the bottom of FIG. 14, an image for 667 pixels at the center of the light receiving element 121a is cut out, and an observation image is generated by performing pixel interpolation, whereby a 1.5 times observation image can be obtained. Then, the observation magnification of the first light receiving unit 120A is enlarged by 3 times from 0.5 to 1.5 times, and the observation magnification of the second light receiving unit 120B having an optical magnification of 2 times is enlarged by 3 times from 0.5 to 1.5 times. Thus, a magnification of 9 times can be realized by properly using the first and second light receiving portions 120A and 120B.

  The optical microscope 520 of the second embodiment can be provided with an observation magnification range that can be magnified 9 times from 0.5 to 4.5 times as described above by properly using the first and second light receiving portions 120A and 120B. . Since the optical microscope 520 having a wide range of observation magnifications includes the constant magnification projection unit 110 as described above, even if the observation magnification is changed, it is included in the minimum pattern width in the observation image. Only the number of light-receiving pixels changes, and height measurement can be performed with a unified measurement method that does not depend on the magnitude of the observation magnification.

  When thinning processing is performed, height measurement may be performed based on the image (2000 pix) on the upper left light receiving element in FIG. 14, or an observation image shown on the right side, that is, an image after thinning processing is performed. The height may be measured based on the above.

  The area on the stage 140 and the pattern projection area are preferably set larger than the light receiving (observation) area (observation field of view) acquired by the light receiving unit 120 as described above to set the margin. FIG. 19 shows an observation region (observation field) in the first light receiving unit 120A with a low magnification, and below that, an observation region (observation field) in the second light receiving unit 120B with a high magnification is shown. The observation field of view at the high magnification second light receiving unit 120B is smaller than the observation field of view at the low magnification first light receiving unit 120A. In other words, the minimum pattern width on the observation image increases as the observation magnification increases.

  When the minimum pattern width of the pattern generation unit (two-dimensional array) 112 that generates a pattern is held by, for example, a plurality of pixels, the number of pixels that bear the minimum pattern width on the observation image decreases as the observation magnification increases. By adding this control, the number of light receiving pixels included in the minimum pattern width can be suppressed to a predetermined value or less even when the observation magnification range is wide.

Third Example (FIG. 15) :
In the optical microscope 530 of the third embodiment, a zoom mechanism is added to the telecentric lens of the light receiving optical system included in the light receiving unit 120, and the zoom mechanism allows observation at an arbitrary zoom magnification, that is, a stepless magnification.

Fourth Example (FIG. 16) :
In the optical microscope 540 of the fourth embodiment, the objective lens of the light receiving optical system included in the light receiving unit 120 is replaceable, and in this embodiment, observation is performed at a multistage observation magnification by adopting a revolver type objective lens. can do. Of course, it is also possible to realize observation at a multistage observation magnification by attaching and detaching a plurality of objective lenses.

Example 5 (FIG. 17) :
The optical microscope 550 of the fifth embodiment shown in FIG. 17 is also a modification of the optical microscope 500 of the first embodiment described with reference to FIG. (I) of FIG. 17 is a front view of the optical microscope 550 of the fifth embodiment, and (II) is a side view.

  In the optical microscope 550 of the fifth embodiment, the two-dimensional pattern is generated by reflecting the light emitted from the measurement light source 111 by the pattern generation unit (two-dimensional array) 112 with respect to the left and right light projecting units 110A and 110B. . The light receiving unit 120 includes a first light receiving unit 120A having a relatively low magnification and a second light receiving unit 120B having a relatively high magnification, and the first and second light receiving units 120A and 120B. Both are preferably composed of telecentric lenses. The light receiving element 121a of the first light receiving unit 120A with a low magnification is arranged orthogonal to the observation optical axis 125. On the other hand, the light receiving element 121a of the high-magnification second light receiving unit 120B is orthogonal to the branch observation axis 128 that branches from the observation optical axis 125 by the branch mirror 127 disposed on the observation optical axis 125 and extends in the lateral direction. Has been placed.

Example 6 (FIG. 18) :
The optical microscope 560 of the sixth embodiment shown in FIG. 18 is a modification of the fifth embodiment (FIG. 17). (I) of FIG. 18 is a front view of the optical microscope 560 of the sixth embodiment, and (II) is a side view. The optical microscope 560 of the sixth embodiment has a configuration in which a ring-shaped illumination light output unit 130 is arranged coaxially with the observation optical axis 125 in the optical microscope 550 (FIG. 17) of the fifth embodiment. The ring-shaped illumination light output unit 130 may be detachable or may be integrated with the light receiving unit 120.

  As a modification of the ring-shaped illumination light output unit 130, coaxial epi-illumination, transmitted illumination, and side illumination spot illumination may be employed.

Example 7 (FIG. 20) :
When the light projecting unit 110 is configured with a constant light projecting magnification, as can be understood from FIG. 19 described above, as the observation magnification range becomes wider and the magnification becomes higher, the light receiving pixel has a minimum pattern width on the observation image. The ratio increases. As described above, when three-dimensional measurement of the object S is performed, the projection pattern is shifted and a plurality of received light images (observation images) are acquired. This projection pattern shift is performed in units of DMD micromirrors of the pattern generation unit 112 in the above-described embodiment. However, when observing at a high magnification, there is a possibility that the pattern feed pitch and the minimum pattern width when viewed on the observation image cannot be reduced. In other words, as the zoom magnification, that is, the observation magnification range that is a high magnification ratio with respect to the low magnification becomes larger, the feed pitch on the observation image becomes too large, and there is a possibility that the accuracy cannot be ensured. As a countermeasure against this, an optical microscope 570 of the seventh embodiment shown in FIG. 20 incorporates a mechanism for generating a resolution finer than the pixel pitch of the two-dimensional array of the pattern generation unit 112.

  An optical microscope 570 according to the seventh embodiment illustrated in FIG. 20 includes a minute displacement driving mechanism 117 that displaces the two-dimensional array of the pattern generation unit 112. The minute displacement driving mechanism 117 shifts the DMD by a minute feed amount smaller than, for example, one pixel (one micromirror) of the DMD of the pattern generation unit 112. For example, when the observation magnification is 5 times or more, this observation magnification is detected and the minute displacement drive mechanism 117 is operated, and a predetermined pitch may be set as the minute feed pitch. You may make it perform control which makes the pitch of minute feed small. By performing minute feed by the minute displacement drive mechanism 117 at a pitch that can subdivide the minimum pattern width of the pattern on the observation image, the resolution and accuracy relating to height measurement when the observation magnification (light reception magnification) is high are increased. be able to. In the figure, a symbol in which x is surrounded by a circle and a symbol in which a black circle is surrounded by a circle indicate a minute displacement direction perpendicular to the paper surface.

  FIG. 21 is a diagram illustrating a specific configuration example of the pattern generation unit 112 in which the minute displacement driving mechanism 117 is incorporated. A support substrate 572 carrying the two-dimensional array 118 of the pattern generation unit 112 and a control substrate 573 are connected by a flexible cable 514, and a minute displacement driving mechanism 117, a heat sink 574, and the like are interposed between the control substrate 573 and the support substrate 572. Is arranged. The control board 573 is fixed to the frame of the optical microscope 570.

Example 8 (FIG. 22) :
The optical microscope 580 of the eighth embodiment shown in FIG. 22 is also a modification of the seventh embodiment (FIG. 20). In the optical microscope 580 of the eighth embodiment, the two-dimensional array 118 of the pattern generation unit 112 and the measurement light source 111 are unitized, and a minute displacement driving mechanism 117 is assembled to the unit 582. When the unit 582 is displaced by the operation of the minute displacement driving mechanism 117, the projection pattern on the stage 140 can be changed at a pitch finer than the number of pixels of the two-dimensional array.

Ninth embodiment (FIG. 23) :
The optical microscope 590 of the ninth embodiment shown in FIG. 23 is also a modification of the seventh embodiment (FIG. 20) and the eighth embodiment (FIG. 22). In the optical microscope 590 of the ninth embodiment, the two-dimensional array 118 of the pattern generation unit 112, the measurement light source 111, and the light guide optical system such as the light projection lenses 114 and 115 are unitized. Thus, a minute displacement driving mechanism 117 is assembled. When the unit 592 is displaced by the operation of the minute displacement driving mechanism 117, the projection pattern on the stage 140 can be changed at a pitch finer than the number of pixels of the two-dimensional array.

Example 10 (FIG. 24) :
An optical microscope 600 according to the tenth embodiment shown in FIG. 24 has a minute displacement driving mechanism 602 that minutely moves a lens constituting a light guiding optical system such as the light projecting lenses 114 and 115. By performing an operation or a minute tilt operation, the projection pattern on the stage 140 is changed at a pitch finer than the number of pixels of the two-dimensional array.

Example 11 (FIG. 25) :
An optical microscope 610 according to the eleventh embodiment shown in FIG. 25 includes a plate 612 that transmits light to the output side of the light guide optical system such as the light projecting lenses 114 and 115, and a minute displacement that slightly displaces the light transmitting plate 612. The drive mechanism 614 is arranged, and the light transmission plate 612 is micro-reciprocating or tilting to change the projection pattern on the stage 140 at a pitch finer than the number of pixels of the two-dimensional array. Yes. Instead of the light transmission plate 612 in FIG. 25, a mirror that bends light may be arranged, and the bending mirror may be displaced by a minute reciprocating operation or a minute tilt.

  Although the embodiments of the present invention have been described above, the micro displacement drive mechanisms 117, 602, and 614 described in the seventh to eleventh embodiments may be applied to the first to sixth embodiments. It is.

500 Optical microscope 110 Projecting unit 111 Measuring light source (halogen lamp)
112 Pattern generator (DMD)
114, 115 Projection lens (preferably double-sided telecentric lens)
120 light receiving unit 120A low magnification light receiving unit 120B high magnification light receiving unit 121a imaging device (preferably monochrome CCD)
140 Stage 640 Optical axis of observation part (observation center axis)

Claims (8)

A stage on which the object is placed;
A light receiving unit having an observation center axis directed toward an object placed on the stage and having a variable light receiving magnification;
A light projecting unit that irradiates light obliquely to the object,
The light projecting unit has a pattern generation unit, and reflects the measurement light to the two-dimensional array of the pattern generation unit or transmits the measurement light to the two-dimensional array to project the pattern onto the object on the stage. An optical microscope capable of measuring the height of an object by:
The lens of the light projecting unit is fixed at a constant magnification,
An optical microscope, wherein the number of pixels included in the minimum pattern width received by the light receiving element of the light receiving unit is at least one when the minimum magnification of the light receiving unit.   The optical microscope according to claim 1, wherein the light projecting unit includes a double-sided telecentric lens.   The optical microscope according to claim 2, wherein the light receiving unit includes a telecentric lens.   The light receiving unit includes a low-magnification first light receiving unit in which a first light receiving element is arranged orthogonal to the observation center axis, and a second light receiving element orthogonal to a branch observation axis branched from the observation center axis. The optical microscope according to claim 3, further comprising a high-magnification second light-receiving unit arranged.   The optical microscope according to any one of claims 2 to 4, wherein light from a measurement light source of the light projecting unit is reflected by the pattern generation unit and a pattern is projected onto an object on the stage. Having at least a pair of the light projecting portions;
The optical microscope according to any one of claims 1 to 5, wherein the pair of light projecting units are arranged in a mirror image symmetry with respect to an observation center axis of the light receiving unit.   The optical microscope according to claim 1, wherein the light receiving element is monochrome.   The optical microscope according to any one of claims 1 to 7, wherein image processing is performed to change a parameter of an image waviness removal filter in accordance with a magnitude of light reception magnification.

Images