JP2008152011A - Confocal microscope and method for picking up confocal image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a confocal microscope which can be easily focused, and a method for picking up a confocal image. <P>SOLUTION: The confocal microscope is equipped with: a galvano mirror 105 for scanning linear light from a slit plate 130; a lens 107 for forming an image of the linear light on a sample arranged at a position conjugate to the slit plate 130; a CCD line sensor 110 having a pixel string corresponding to the linear light; a light shielding plate 120 for shielding a part of the light; a two-division optical sensor 109 for detecting the light reflected on the sample 300 out of the light scanned with the linear light by the galvano mirror 105; and a Z-axis drive motor 208 adjusting the focal position of the linear light based on an output from the two-division optical sensor 109 when the light shielding plate 120 is arranged on an optical path. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a confocal microscope and a method for capturing a confocal image.

A conventional confocal microscope employs a configuration in which light transmitted through one slit is illuminated on a sample, and reflected light from the sample is detected by a one-dimensional CCD (Charge-Coupled Device) ( For example, Patent Document 1). In such a conventional slit confocal microscope, it is common to perform focusing by manual operation. That is, focusing is performed according to the amount of light detected by the one-dimensional CCD camera. In a conventional confocal microscope, for example, focusing is performed based on image contrast and sharpness. Alternatively, autofocus is performed using a focus optical system installed separately from the observation optical system.
JP-A-10-104523

  However, in recent use of a microscope, there is a need to automatically measure a predetermined line width, step, and roughness. In constructing such a system, a low-cost focusing mechanism has become an indispensable mechanism. And it is necessary to observe and measure in a focused state. However, the conventional slit confocal microscope has a problem that focusing cannot be performed with a simple configuration.

Thus, the conventional confocal microscope has a problem that the focus cannot be easily adjusted.
The present invention has been made in view of the above-described problems, and an object thereof is to provide a confocal microscope and a confocal image capturing method capable of adjusting the focus with a simple configuration.

  A confocal microscope according to a first aspect of the present invention includes a light source that emits illumination light, a light conversion unit that converts illumination light from the light source into linear light, and scanning that scans the linear light. And imaging means for imaging the linear light on a sample disposed at a position conjugate with the light conversion means, and imaging transmitted light or reflected light from the sample on an imaging surface; An observation detector disposed on the imaging surface to receive the transmitted light or the reflected light and having a pixel row corresponding to the linear light, and disposed on an optical path of light from the light source, A light shielding member for shielding a part of light from a light source, a focus position sensor for detecting light reflected by the sample out of light scanned together with the linear light by the scanning means, and the light shielding member. Output from the focus position sensor in the state of being placed on the optical path Zui and, in which and a focus adjustment means for adjusting the focal position of the line-shaped light. Thereby, the focus can be adjusted with a simple configuration.

  A confocal microscope according to a second aspect of the present invention is the confocal microscope described above, further comprising an integration circuit that integrates an output from the position detection sensor, and based on an integration value in the integration circuit. The focus adjusting means adjusts the focus. Thereby, the focus can be accurately adjusted.

  A confocal microscope according to a third aspect of the present invention is the above-described confocal microscope, comprising: a scanning position detection detector disposed at a scanning end of the scanning means; and the scanning position detection detector. And a clamp circuit that performs a clamp operation that does not increase or decrease the integration value of the integration circuit based on the output. Thereby, the focus can be accurately adjusted.

  A confocal microscope according to a fourth aspect of the present invention is the confocal microscope described above, wherein the integration value of the integration circuit is reset based on an output from the scanning position detection detector. To do. Thereby, the focus can be accurately adjusted.

  A confocal microscope according to a fifth aspect of the present invention is the above-described confocal microscope, wherein the light conversion means is a slit plate having a line-shaped opening for illumination, and the slit plate is used for a focal position. A focal position opening through which light received by the sensor is transmitted is provided. Thereby, a focus can be prepared with a simple configuration.

  A confocal microscope according to a sixth aspect of the present invention is the confocal microscope described above, wherein linear light is received by the observation detector while the focus is adjusted by the focus adjusting means. When the observation is performed, the light shielding member does not shield part of the light from the light source. Thereby, it can observe in the state which adjusted the focus correctly.

  A confocal image capturing method according to a seventh aspect of the present invention is a confocal image capturing method for detecting a light through a confocal optical system and capturing a confocal image, which is disposed on an optical path. A step of shielding a part of the light by the light shielding member, a step of scanning the shielded light by a scanning means, a step of condensing and irradiating the scanned light on the sample, A step of detecting reflected reflected light with a focus position sensor, a step of adjusting the focus of the sample based on an output from the focus position sensor, and a state in which the focus of the sample is adjusted are linear. Scanning with the scanning means, condensing and irradiating the sample with linear light scanned by the scanning means, and irradiating the sample. The reflected light reflected by the sample or the transmitted light transmitted through the sample is received through the confocal optical system by the observation detector having a pixel row corresponding to the linear light. And a step of performing. Thereby, a focus can be easily prepared.

  The confocal image capturing method according to the eighth aspect of the present invention is the above-described image capturing method, wherein the step of adjusting the focus of the sample is based on an integrated value obtained by integrating the output from the focus position sensor. Then, the focus is adjusted. Thereby, the focus can be accurately adjusted.

  A confocal image capturing method according to a ninth aspect of the present invention is the above-described image capturing method, characterized in that the scanning means performs a clamping operation that does not increase or decrease the integral value at the scanning end. is there. Thereby, the focus can be accurately adjusted.

  A method for capturing a confocal image according to a tenth aspect of the present invention is the above-described image capturing method, wherein the integral value is reset at one end of scanning of the scanning unit. Thereby, the focus can be accurately adjusted.

  A confocal image capturing method according to an eleventh aspect of the present invention is the above-described imaging method, wherein the linear light is generated by a slit plate having a line-shaped illumination opening, and the slit plate has The reflected light reflected by the sample after passing through the provided focal position opening is detected by the focal position sensor. Thereby, a focus can be easily prepared.

  A confocal image capturing method according to a twelfth aspect of the present invention is the above-described imaging method, wherein a part of the light is not shielded in the step of scanning the line-shaped light by the scanning unit. It is characterized by this.

  ADVANTAGE OF THE INVENTION According to this invention, the confocal microscope which can adjust a focus with a simple structure, and the imaging method of a confocal image can be provided. Thereby, it can observe in the state which adjusted the focus correctly.

  The confocal microscope according to the present embodiment has a focus mechanism having a two-divided sensor composed of an optical sensor having two regions and a light shielding plate provided in the vicinity of the slit. With this focus mechanism, focusing in a confocal microscope can be performed automatically and at a low cost. Hereinafter, embodiments to which the present invention can be applied will be described. The following description is to describe the embodiment of the present invention, and the present invention is not limited to the following embodiment. For clarity of explanation, the following description is omitted and simplified as appropriate. Moreover, those skilled in the art can easily change, add, and convert each element of the following embodiments within the scope of the present invention.

  The configuration of the confocal microscope according to the present invention will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of a confocal microscope 1. The confocal microscope 1 according to the present embodiment includes an optical system 100 and a circuit unit 200. The optical system 100 includes a light source 101, lenses 102, 103, 106, 107, 108, a beam splitter 104, a galvano mirror 105, a two-part photosensor 109, a CCD line sensor 110, and a sample holder 111. The optical system 100 of the confocal microscope 1 according to the present embodiment includes a light shielding plate 120 and a slit plate 130. Further, the light from the optical system 100 is collected on the sample 300 placed on the sample holder 111. Thus, the microscope according to the present embodiment is a slit confocal microscope.

  In the present embodiment, a CCD line sensor 110 that captures a confocal image of the sample 300 is provided. The light transmitted from the light source 101 through the slit plate 130 reflects the sample 300 and is detected by the CCD line sensor 110. Further, by using the galvanometer mirror 105, light can be scanned on the sample 300. That is, the galvanometer mirror 105 is used to scan the sample 300, whereby the focal position of the light from the light source 101 changes in a direction perpendicular to the axis of the objective lens 107. The galvanometer mirror 105 scans light at 30 Hz, for example. The galvanometer mirror 105 scans the linear light that has passed through the slit plate 130. Thereby, a slit confocal image is imaged.

  The light source 101 is, for example, a white light source, a fluorescence excitation light source, and more specifically, various light sources such as a mercury lamp and a halogen lamp can be used. Further, the light source may be configured by two-dimensionally arranging laser diodes having different oscillation phases. Oscillation of laser diodes having different oscillation phases can suppress the generation of speckles (small spots generated by light interference). Further, a bundle fiber in which a plurality of optical fibers are bundled may be provided in the light source 101. That is, the light emitted from the bundle fiber may be used as illumination light.

  The two-divided optical sensor 109 is a two-divided PD (Photo diode) divided into two regions, region A and region B. In the confocal microscope according to the present embodiment, it is possible to determine whether or not the sample surface is deviated from the focal position based on the light amounts detected in the two regions of the two-split optical sensor 109. In addition, when the sample surface is displaced with respect to the focal position, it can be determined whether the sample surface is displaced toward the lens 107 or away from the lens 107. That is, the two-part optical sensor 109 is used for focusing.

  The sample holder 111 has a Z-axis drive motor 208 so that the sample 300 can be moved up and down in FIG. The sample holder 111 is moved up and down by a Z-axis drive motor 208, which will be described later, and is controlled so that the sample surface comes to the focal position by this up and down movement. That is, focus adjustment is performed by moving the sample holder 111 up and down. Specifically, the Z-axis drive motor 208 is driven according to the output from the two-split optical sensor 109. Then, the sample holder 111 is moved up and down by driving the Z-axis drive motor 208 to move the sample 300 to the in-focus position. The configuration is not limited to the configuration in which the sample holder 111 is moved to recognize the focal position, but the focal position may be adjusted by moving the lens 107 or the like.

  The light shielding plate 120 is provided in the vicinity of the slit plate 130 and can be moved left and right in FIG. The light shielding plate 120 is disposed between the slit plate 130 and the lens 103. At the time of detecting the focal position, the light shielding plate 120 moves on the optical path so as to block the light from the light source 101 by half. On the other hand, at the time of normal mask inspection, the light shielding plate 120 moves to the left in FIG. 1 to irradiate the sample 300 with all the light from the light source 101. That is, when observing with a confocal microscope, the light shielding plate 120 is removed from the optical path. As described above, the light shielding plate 120 is movably provided on the optical path. The light shielding plate 120 is removed from the optical path during normal observation, and is disposed on the optical path during focus position detection. The light shielding plate 120 is accurately moved by an actuator such as a solenoid, a motor, or a cylinder. If this light-shielding plate 120 is arranged on the optical path, the pupil can be illuminated asymmetrically. Specifically, one half of the pupil is shielded and illuminated from only the other half.

  The slit plate 130 is disposed on the optical path near the light source 101. The slit plate 130 converts light from the light source 101 into linear light. The position of the slit plate 130 is conjugate with the position of the primary image plane, the position of the CCD line sensor 110, and the position of the sample surface. By scanning the light from the slit plate 130, it is possible to change the region in the sample 300 where the confocal image is captured. That is, the imaging region is changed by driving the galvanometer mirror 105. The galvanometer mirror 105 scans light in a direction perpendicular to the linear light. Thereby, the incident position of the light on the sample 300 is changed, and the linear light is scanned. Then, the reflected light reflected by the sample 300 is detected by the CCD line sensor 110. The pixels of the CCD line sensor 110 are arranged corresponding to linear light. That is, the CCD line sensor 110 has a pixel row corresponding to linear light. Thereby, a confocal image can be taken. Thus, a confocal image can be observed by the output from the CCD line sensor 110.

  FIG. 2 shows a schematic structural diagram of the slit plate 130 and a sensor arrangement corresponding thereto. 2A and 2B, the schematic structural diagram of the slit plate 130 is shown on the upper side, and the arrangement of the line sensor 110 and the two-part photosensor 109 is shown on the lower side. As shown in FIG. 2, the slit plate 130 has a focal position opening 131 and an image illumination opening 132. The image illumination opening 132 is a horizontally long line-shaped opening. By passing through the image illumination opening 132, the light from the light source 101 is converted into linear light. The focal position opening 131 and the image illumination opening 132 may be arranged in a direction perpendicular to the longitudinal direction of the image illumination opening 132 as shown in FIG. In this case, the line sensor 110 and the two-split light sensor 109 are arranged perpendicular to the arrangement direction of the pixels of the line sensor 110. Alternatively, as shown in FIG. 2B, the focal position opening 131 and the image illumination opening 132 may be arranged in a direction parallel to the longitudinal direction of the slit. In this case, the line sensor 110 and the two-part optical sensor 109 are arranged in a direction parallel to the arrangement direction of the pixels of the line sensor 110. In the configuration shown in FIG. 2B, the focal position opening 131 and the image illumination opening 132 may be connected. That is, the end of the line-shaped opening may be used as the image illumination opening 132 and the remaining opening may be used as the focal position opening 131. As described above, the positions of the two-part optical sensor 109 and the CCD line sensor 110 are determined in accordance with the positional relationship between the focal position opening 131 and the image illumination opening 132. Therefore, restrictions due to the physical size of the two-split optical sensor 109 and the CCD line sensor 110 can be relaxed. Therefore, the lateral direction of the two-split optical sensor can be increased, and the focal position can be detected more accurately.

  The image illumination opening 132 converts light from the light source 101 into line-shaped light. That is, the image illumination opening 132 generates line-shaped light. By observing the light reflected from the sample 300 by the CCD line sensor 110, a confocal image of the sample 300 is captured. Further, the light that has passed through the focal position opening 131 is irradiated onto the two-divided optical sensor 109 to perform focusing. The focal position opening 131 has a shape corresponding to the shape of the two-split optical sensor 109. Here, the focal position opening 131 is rectangular.

  Here, the path of the light emitted from the light source 101 will be described with reference to FIG. The light emitted from the light source 101 is collected by the lens 102 and enters the slit plate 130. The light that has entered the slit plate 130 is converted into line-shaped light at a portion that has passed through the image illumination opening 132 and is incident on the lens 103. Similarly, the light that has passed through the focal position opening 131 is incident on the lens 103. The light incident on the lens 103 is converted into parallel light by the lens 103, reflected by the beam splitter 104, and incident on the galvanometer mirror 105. The light reflected from the galvanometer mirror 105 enters the lens 106. The lens 106 condenses the light on the primary image plane. The light refracted by the lens 106 enters the lens 107. Thereafter, the light is refracted by the lens 107 and illuminates the sample 300. The lens 107 is an objective lens and collects illumination light on the sample 300. Then, by rotating the galvanometer mirror 105, it is possible to illuminate a predetermined imaging position on the sample 300.

  The reflected light reflected from the sample 300 enters the lens 107. The lens 107 condenses the reflected light on the primary image plane. Thus, the lens 107 forms an image of light on the sample and the primary image plane. This reflected light is incident on the lens 106. The reflected light is refracted by the lens 106 to become a parallel light beam. The reflected light that has become a parallel light beam is reflected by the galvanometer mirror 105. The reflected light reflected by the galvanometer mirror 105 is descanned and enters the beam splitter 104. A part of the reflected light passes through the beam splitter 104 and is condensed on the CCD line sensor 110 by the lens 108. Further, the light passing from the light source 101 through the focal position opening 131 in the slit plate 130 passes through the same optical path as the light passing through the image illumination opening 132 and is condensed on the two-split optical sensor 109. The That is, light that has passed through the focal position opening 131 is incident on the sample 300 via the beam splitter 104, the galvanometer mirror 105, the lens 106, and the lens 107. Then, the light from the focal position opening 131 reflected by the sample 300 enters the two-divided optical sensor 109 via the lens 107, the lens 106, the galvanometer mirror 105, the beam splitter 104, and the lens 108. As a result, the reflected light reflected by the sample 300 can be received by the two-split optical sensor 109.

  Next, how to focus in the confocal microscope according to the present embodiment will be described. First, the illumination location of the two-part optical sensor 109 when the pupil is illuminated symmetrically will be described with reference to FIG. The two-split optical sensor 109 is divided into two areas A and B. 3A shows the case where the sample surface is located at the focal position, FIG. 3B shows the case where the sample surface is located before the focal position, and FIG. 3C shows the case where the sample surface is located behind the focal position. This is the case.

  As shown in FIG. 3A, when the sample surface is located at the focal position, the focal point is located on the two-split optical sensor 109. In such a state, the amount of light irradiation in both the region A and the region B is substantially the same without changing. In addition, even when the sample surface is positioned before the focal position (see FIG. 3B) and when the sample surface is positioned behind the focal position (see FIG. 3C), the region A In both the region B and the region B, the light irradiation amount does not change. That is, the light on the two-split optical sensor 109 is blurred, but the center position is not changed. Therefore, when the pupil is illuminated symmetrically, the difference in the amount of light detected between the region A and the region B does not change depending on the focal position. Therefore, it is difficult to determine where the sample surface is with respect to the focal position.

  On the other hand, when the pupil is illuminated asymmetrically, the difference in the amount of light detected between the region A and the region B varies depending on the focal position. Thereby, the position with respect to the focal position of the sample surface can be determined. Here, the illumination part of the two-part optical sensor 109 when the pupil is illuminated asymmetrically will be described with reference to FIG. FIG. 4A to FIG. 4C are diagrams schematically showing incident light incident on the sample and reflected light reflected by the sample. In FIG. 4, the solid line indicates the incident light incident on the sample, the dotted line indicates the reflected light reflected by the sample, and the alternate long and short dash line indicates the optical axis. 4A shows the case where the sample surface is located at the focal position, FIG. 4B shows the case where the sample surface is located before the focal position, and FIG. 4C shows the case where the sample surface is located before the focal position. This is the case behind. In this case, only half of the pupil is cut by the light shielding plate 120. That is, FIG. 4 shows a state illuminated with only the left side light. Accordingly, the reflected light reflected by the sample surface is incident on the two-part photosensor 109 mainly through the right side of FIG.

  As shown in FIG. 4A, when the sample surface is located at the focal position, both the region A and the region B are illuminated in the same region, and both the region A and the region B have substantially the same level of signal. Output. On the other hand, when the sample surface is positioned before the focal position, illumination is performed only on the region B side (see FIG. 4B). In addition, when the sample surface is located behind the focal position, illumination is performed only on the region A side (see FIG. 4C). That is, the incident position of the reflected light changes according to the focal position. From the above, it is possible to determine whether the sample surface is on the front side or the rear side with respect to the focal position by measuring the doses of the regions A and B. That is, the light received in the region A and the region B differs depending on the focal position. Therefore, focusing can be performed according to the difference between the amount of light applied to the region A and the amount of light applied to the region B. In this way, at the pupil position, the focal position can be easily detected by shielding only one half and illuminating with one half.

  In this determination, generally, a signal in which (a + b) obtained by adding the light amount a irradiated to the region A and the light amount b irradiated to the region B is used as a denominator and (a−b) as a numerator is used. It is done. That is, a signal obtained by dividing (a−b) by (a + b) is used. Then, the sample holder 111 is moved by the Z-axis drive motor 208 according to the size of (a−b) / (a + b). Thereby, the sample 300 can be focused. That is, when the size of (a−b) / (a + b) becomes substantially zero, it is determined that the sample surface is the in-focus position. Furthermore, it can be determined whether the focus is shifted forward or backward depending on whether the value of (a−b) / (a + b) is positive or negative. For example, when the value of (a−b) / (a + b) is positive, that is, it is determined that the focal position is in front of the sample 300 (see FIG. 4C). Then, the shift amount of the focal position can be determined by the magnitude of the value of (a−b) / (a + b).

  Next, the circuit unit 200 includes a clamp circuit 201a, 201b, a subtraction circuit 202, an addition circuit 203, a division circuit 204, an integration circuit 205, a sample hold circuit 206, a drive amplifier 207, a Z-axis drive motor 208, a PD (Photo diode). ) 209a and 209b, and a timing circuit 210. By this circuit unit 200, the focal position when observing with a confocal microscope is adjusted to the sample 300. Note that a digital circuit or an analog circuit may be used as the circuit unit 200. Of course, as the circuit unit 200, a circuit in which an analog circuit and a digital circuit are combined may be used.

  The clamp circuits 201a and 201b are connected to the two-split optical sensor 109. As described above, the two-divided optical sensor 109 is divided into two regions A and B. The clamp circuit 201 a is connected to the area A of the two-divided optical sensor 109, and the clamp circuit 201 b is connected to the area B of the two-divided optical sensor 109. The clamp circuits 201a and 201b are also connected to the timing circuit 210. The clamp circuits 201a and 201b determine that the signal from the two-part optical sensor 109 while receiving the timing signal from the timing circuit 210 is light other than the light reflected from the sample surface, and the signal level at this time The output signal from the two-part optical sensor 109 is offset so that becomes zero. Thereby, noise due to steady stray light or the like can be reduced.

  Further, the two-divided optical sensor 109 is connected to the subtraction circuit 202 and the addition circuit 203 through the clamp circuits 201a and 201b. That is, the signal from the two-part optical sensor 109 with the offset adjusted as described above is input to the subtraction circuit 202 and the addition circuit 203. In the subtraction circuit 202, a value (ab) obtained by subtracting the light amount b detected in the region B of the two-split optical sensor 109 from the light amount a detected in the region A of the two-split optical sensor 109 is used as a signal to the division circuit 204. Output. Further, in the addition circuit 203, a value (a + b) obtained by adding the light amount a detected in the region A of the two-split optical sensor 109 and the light amount b detected in the region B of the two-split optical sensor 109 to the division circuit 204 as a signal. Output. The division circuit 204 calculates a signal of (ab) / (a + b) using the signal (a + b) from the subtraction circuit 202 as a denominator and the signal (ab) from the addition circuit 203 as a numerator. As described above, the focal position is adjusted based on the signal (a−b) / (a + b).

  The value (ab) / (a + b) calculated by the division circuit 204 is output to the integration circuit 205. The integrating circuit 205 integrates (ab) / (a + b) from the dividing circuit 204 with respect to time. This integration time is controlled by a reset signal from the timing circuit 210. The integrating circuit 205 is connected to the sample and hold circuit 206. When the sample signal from the timing circuit 210 is output to the sample and hold circuit 206, the sample and hold circuit 206 extracts an integration value with respect to the time of (a−b) / (a + b) from the integration circuit 205. The value taken out by the sample hold circuit 206 is output to the drive amplifier 207, converted into a current value corresponding to the Z-axis drive motor 208 by the drive amplifier 207, and output. In other words, the drive amplifier 207 converts the amount of current into the amount that the Z-axis drive motor 208 can move by the amount of deviation from the focal position obtained from the value extracted by the sample hold circuit 206. The Z-axis drive motor 208 moves the sample holder 111 up and down in FIG. 1 according to the amount of current input from the drive amplifier 207. As a result, the sample 300 can be moved to the focal position.

  Further, PDs 209 a and 209 b are arranged on the upper part of the end portion of the sample 300. That is, when it is time to irradiate the end portion of the sample 300 by the galvanometer mirror 105, light is irradiated onto the PDs 209a and 209b. Accordingly, the PDs 209a and 209b are irradiated with light at the timing when the rotation direction of the galvano mirror 105 is reversed. When the PDs 209a and 209b are irradiated with light, signals are output from the PDs 209a and 209b to the timing circuit 210. That is, when light is illuminated at a position where the end of the sample is irradiated while the sample surface is scanned by the galvanometer mirror 105, a signal is output from the PDs 209a and 209b to the timing circuit 210. . The PDs 209a and 209b are arranged on the primary image plane. The PDs 209a and 209b are arranged outside the field of view. The PDs 209a and 209b receive light that has passed through the focal position opening 131.

  When light scans over the sample 300, the direction is changed at the end of the sample 300. That is, the scanning direction of the galvanometer mirror 105 is reversed by 180 ° at the end of the sample 300, for example. Since the direction change performed at that time cannot be performed rapidly, the light irradiated to the end portion of the sample 300 is irradiated for a predetermined time. For this reason, when integration with respect to time is performed by the integration circuit 205, if there is a cause of noise at the end of the sample 300, the noise in this portion is integrated for a predetermined time. Therefore, the noise in this portion has a great influence on the value integrated by the integration circuit 205. That is, the influence during the direction change becomes large. In the confocal microscope according to the present embodiment, the PDs 209a and 209b are arranged so that light is not irradiated to the end portion of the sample 300. In other words, the PDs 209 a and 209 b are arranged at both ends of the scanning of the galvanometer mirror 105.

  As described above, the PDs 209a and 209b detect the light amount of the irradiated light and at the same time serve as a mask at the scanning end. Accordingly, it is possible to prevent the light that has passed through the focal position opening 131 from entering the sample 300 when changing the direction of the scanning direction at the scanning end. Therefore, the influence of noise during the direction change can be reduced, and focusing can be performed accurately. Thus, the scanning position can be detected by using the PDs 209a and 209b arranged at the scanning end. That is, it is possible to determine whether or not the scanning of the galvano mirror 105 is at the scanning end based on the outputs of the PDs 209a and 209b. It is possible to prevent light from entering the two-part photosensor 109 while the scanning direction of light is reversed at the scanning end.

  Next, FIG. 5 shows a timing chart of the integration circuit 205, the sample hold circuit 206, and the clamp circuits 201a and 201b. The timing circuit 210 creates a clamp signal output to the clamp circuits 201a and 201b from the signals output from the PD 209a and the PD 209b. FIGS. 5B to 5D show the timing of the clamp signal and the signals output from the PDs 209a and 209b. That is, the clamp signal is output from the timing circuit 210 while the PD 209a and the PD 209b are irradiated. Further, the deflection angle of the galvanometer mirror 105 is shown in FIG. Here, the reference angle of the deflection angle of the galvanometer mirror 105 is set to 0, and the deflection angle from the reference angle is indicated by ±. The deflection angle of the galvanometer mirror 105 changes at a constant period. The speed of the deflection angle in the + direction is different from the speed of the deflection angle in the − direction.

  PD1 and PD2 shown in FIGS. 5C and 5D are signals from the PD 209a and the PD 209b. PD1 and PD2 are either PD209a or PD209b depending on the scanning direction. That is, one of PD1 and PD2 corresponds to a signal from PD 209a, and the other corresponds to a signal from PD 209b. Here, when observing while scanning from the PD 209a to the PD 209b, the speed from the PD 209b to the PD 209a is generally faster than the speed from the PD 209a to the PD 209b. For example, since a certain signal amount level is required for generating an image signal by scanning light, scanning in one direction is performed at a relatively low speed. That is, scanning is performed at low speed only in one direction, and the output from the line sensor 110 is made to reach a predetermined signal amount level. On the other hand, scanning in the opposite direction is performed at a high speed in order to reduce the loss time. In such a case, PD1 corresponds to PD209b and PD2 corresponds to PD209a. This is shown as an example in the present embodiment, and the scanning direction may be reversed, and the scanning speed in either direction is constant, and the gist of the present invention is not affected. . As shown in FIGS. 5C and 5D, PD1 and PD2 have a pulse waveform in which pulses are output at time intervals corresponding to the scanning cycle. Here, each of PD1 and PD2 outputs one pulse for each scanning period. Here, the scanning cycle is a time period from when one end of scanning is performed to the other end to when it returns to one end. Accordingly, since light reciprocates in one scanning cycle, it passes through the center of scanning twice. The timing of PD1 and PD2 and the pulse are shifted according to the scanning speed. Further, since the PDs 209a and 209b are arranged at both ends of scanning, the pulses of PD1 and PD2 are alternately output.

  The clamp signal is, for example, an OR output between PD1 and PD2. Accordingly, the clamp signal is output at the timing when the light enters the PD 209a and at the timing when the light enters the PD 209b. Therefore, two pulses are output for each scanning cycle in the clamp signal. While the clamp signal is output to the clamp circuits 201a and 201b, the clamp circuits 201a and 201b perform a clamp operation. This clamping operation is an operation in which the values output from the clamping circuit 201a and the clamping circuit 201b are set to substantially zero with reference to the value of the signal from the two-part optical sensor 109. By doing so, the value output from the dividing circuit 204 to the integrating circuit 205 becomes zero, so that the integrated value in the integrating circuit 205 takes a constant value. That is, the integral value does not increase or decrease while the clamp signal outputs a pulse and the clamp operation is performed. Therefore, the signal at the end of the sample 300 can be prevented from being integrated by the integration circuit 205. Thereby, the focal position can be accurately adjusted.

  The timing circuit 210 generates a sample signal and a reset signal based on the signal from the PD1. The timings of the sample signal and the reset signal are shown in FIGS. 5 (e) and 5 (f). The sample signal is a pulse signal that is output when PD1 rises and has a shorter pulse width than the signal of PD1. The reset signal is a pulse signal that is output when PD1 falls and has a shorter pulse width than PD1. The sample signal is output to the sample hold circuit 206. In response to the sample signal, the sample hold circuit 206 extracts and holds the value accumulated in the integration circuit 205. Then, the sample hold circuit 206 outputs this value to the drive amplifier 207. The reset signal is output to the integration circuit 205. The integration circuit 205 resets the integrated value in response to the reset signal to zero. That is, the integration circuit 205 integrates the (a−b) / (a + b) signal output from the division circuit 204 only between the reset signal and the next input reset signal. That is, the (a−b) / (a + b) signal is integrated for one scanning period excluding the scanning end. Then, after one scanning cycle elapses, the integral value is reset to zero.

  By doing as described above, the value integrated by the integration circuit 205 becomes a value as shown in FIG. First, when light comes to the first end of scanning, a reset signal is output and the value in the integrating circuit 205 becomes zero. Next, the light scanning position is moved from the first end of the sample 300 to the second end by the galvanometer mirror 105. While moving from the first end to the second end, the (ab) / (a + b) signal is integrated. Here, it is assumed that the focal position is on the rear side of the sample 300, and the value of (a−b) / (a + b) is positive (see FIG. 4C). In this case, as shown in FIG. 5G, the integration value in the integration circuit 205 gradually increases. That is, the integrated value changes with a slope corresponding to the amount of positional deviation and the scanning speed. When the light scanning position moves to the second end, a clamp signal is output from the timing circuit 210 to the clamp circuits 201a and 201b. That is, since light enters PD2, a pulse of a clamp signal based on the output of PD2 is output. Since the integral value is clamped while the clamp signal pulse is output, the integral value is constant. Therefore, while the clamp signal pulse is output, the integration value in the integration circuit 205 is a positive value and constant.

  Then, the direction is changed by the galvanometer mirror 105 to reverse the scanning direction. Thereby, the scanning position of the light moves from the second end portion of the sample 300 to the first end portion. While scanning from the second end to the first end, the integration circuit 205 performs integration. Here, since the substantially same position on the sample 300 is operated, the focal position is behind the sample 300 as described above. Therefore, the value of (a−b) / (a + b) is positive. Therefore, the integrated value gradually increases even while the scanning position moves from the second end of the sample 300 to the first end. Here, the scanning speed is changed when the scanning direction is reversed. As a result, the slope of increase in the integrated value also changes. However, the increase amount of the integral value during the movement from the first end portion to the second end portion and the increase amount of the integral value during the movement from the second end portion to the first end portion are: The values are almost the same. This is because the same region is scanned while being reversed only in the scanning direction.

  Then, when the first end is scanned with light, a clamp signal is output from the timing circuit 210 to the clamp circuits 201a and 201b. That is, since light enters PD1, a pulse of a clamp signal based on the output of PD1 is output. Since the integral value is clamped while the clamp signal pulse is output, the integral value is constant. At this time, a sample signal is output from the timing circuit 210 to the sample hold circuit 206, and an integral value of the (a−b) / (a + b) signal is extracted. Thereafter, the integrated value in the integrating circuit 205 returns to zero by the reset signal. The integrated value is calculated in the same manner in the next scan. Thus, during the movement from the first end to the second end and during the movement from the second end to the first end, (ab) / (a + b) ) Continuous signal integration. That is, while the scanning by the galvano mirror 105 makes one round trip, the integration is continued except when the pulse of the clamp signal is output. Then, the focal point is adjusted by the integral value during one reciprocation of scanning. Thereby, the capture noise on the sample surface can be canceled. That is, noise generated by the pattern on the surface of the sample 300 can be reduced.

  For example, when a pattern is formed on the sample surface, the reflectance varies depending on the formed pattern. Accordingly, there is a difference in the amount of reflected light in the vicinity of the pattern boundary. In this case, even if the focal position coincides with the sample surface, the light detected by the PD 209a and the light detected by the PD 209b are different. For example, the amount of light detected by the PD 209a is higher than that detected by the PD 209b. In this case, noise occurs in the integrated signal due to the difference in the reflectance of the pattern. However, in the present embodiment, the (ab) / (a + b) signal is integrated while the scanning by the galvanometer mirror makes one round trip. Thereby, said noise can be reduced. That is, since the light passes through the boundary of the same pattern twice in one round-trip period, the above noise is canceled. Furthermore, noise generated on the inclined surface or step of the end of the pattern is also canceled. In this way, it is possible to perform accurate focusing by using the integral value. Therefore, accurate focusing can be performed on the sample 300 on which various patterns are formed. Of course, integration may be performed not only during one reciprocation of scanning but also during a plurality of reciprocations of scanning.

  As described above, the timing circuit 210 outputs and controls the clamp signal, reset signal, and sample signal based on the signals from the PDs 209a and 209b. Thereby, the focusing can be automatically performed from the signal of the two-split optical sensor 109. That is, it is possible to detect the deviation of the focal position of the region by the integral value during one round of scanning. At this time, the amount of misalignment of the focal position is an average value in an area illuminated during one reciprocation of scanning. And when actually observing, the Z-axis drive motor 208 is operated according to said positional deviation amount. Thereby, it can observe in the state in which the focus position substantially corresponded to the sample surface. For example, the in-focus position is obtained while the sample holder 111 is moved. Then, when performing actual observation, the focal position is set in accordance with the integral value in the illuminated area. Further, autofocus may be performed from a focal position corresponding to the integral value. As described above, in the confocal microscope according to the present embodiment, it is possible to easily focus by using the two-part optical sensor 109, the light shielding plate 120, and the circuit unit 200.

  Various measurements are performed with the focus adjusted as described above. For example, three-dimensional shape measurement and pattern step and line width are measured. At this time, since the focus is adjusted, the measurement can be easily performed.

  In the above description, light is scanned by the galvanometer mirror 105, but the present invention is not limited to this. For example, the slit plate 130 may be moved to scan the light. In this case, the slit plate 130 moves in a direction perpendicular to the longitudinal direction of the image illumination opening 132. For example, the slit plate 130 can move in a direction perpendicular to the paper surface in FIG. By moving in this way, it is possible to scan the light passing through the focal position opening together with the linear light passing through the image illumination opening 132. That is, the imaging light and the focus position detection light may be scanned by the same scanning unit. Accordingly, the imaging light and the focusing light may be light from different light sources. Furthermore, not only the slit plate 130 but also a linear light can be converted by a cylindrical lens or a liquid crystal panel. Furthermore, the slit plate 130 may be a multi slit provided with a plurality of image illumination openings 132.

  In the above description, the light shielding member that shields a part of the light for focusing is described as the light shielding plate 120, but the present invention is not limited to this. For example, even when a liquid crystal panel arranged on the optical path is used as a light shielding member, part of the light can be shielded. In this case, light shielding can be switched only by electrical switching. That is, it is not necessary to move in and out of the light blocking member from the optical path. Furthermore, it is possible to capture a confocal image with the confocal microscope 1 even while part of the light is blocked by the light blocking member. That is, when a part of the light is blocked, the field of view is halved, but even in this case, observation is possible. Moreover, although the said confocal microscope 1 was demonstrated as an epi-illumination microscope which observes using the light reflected by the sample 300, it does not restrict to this. A transmission illumination microscope that observes using light transmitted through the sample 300 may be used.

It is a composition schematic diagram of the confocal microscope of this embodiment. It is a schematic structure figure in the slit in a confocal microscope. It is an example of the positional relationship of the opening part for focus positions and the opening part for image illumination in the slit in a confocal microscope. It is a figure which shows the illumination location of the 2-part dividing optical sensor at the time of illuminating to a pupil symmetrically. It is a figure which shows the illumination location of the 2-part dividing optical sensor at the time of illuminating a pupil asymmetrically.

Explanation of symbols

1 Confocal microscope 100 optical system,
DESCRIPTION OF SYMBOLS 101 Light source 104 Beam splitter 105 Galvanometer mirror 102, 103, 106, 107, 108 Lens 109 Two-part optical sensor 110 Line sensor 111 Sample holder 120 Light-shielding plate 130 Slit 131 Focal position opening part 132 Image illumination opening part 200 Circuit part 201a , 201b Clamp circuit 202 Subtraction circuit 203 Addition circuit 204 Division circuit 205 Integration circuit 206 Sample hold circuit 207 Drive amplifier 208 Axis drive motor 209a, 209b PD
210 Timing circuit 300 Sample

Claims (12)

A light source that emits illumination light;
Light converting means for converting illumination light from the light source into linear light;
Scanning means for scanning the linear light;
An imaging means for imaging the linear light on a sample disposed at a position conjugate with the light conversion means, and imaging transmitted light or reflected light from the sample on an imaging surface;
An observation detector disposed on the imaging surface to receive the transmitted light or the reflected light and having a pixel row corresponding to the linear light;
A light shielding member that is disposed on an optical path of light from the light source and shields part of the light from the light source;
A focus position sensor for detecting light reflected by the sample from light scanned together with the linear light by the scanning means;
A confocal microscope comprising: a focus adjusting unit that adjusts a focus position of the linear light based on an output from a focus position sensor in a state where the light shielding member is disposed on the optical path. An integration circuit for integrating the output from the position detection sensor;
The confocal microscope according to claim 1, wherein the focus adjustment unit adjusts a focus based on an integration value in the integration circuit. A detector for detecting a scanning position disposed at a scanning end of the scanning means;
The confocal microscope according to claim 2, further comprising: a clamp circuit that performs a clamp operation that does not increase or decrease an integration value of the integration circuit based on an output from the scanning position detection detector.   4. The confocal microscope according to claim 3, wherein an integration value of the integration circuit is reset based on an output from the scanning position detection detector. The light conversion means is a slit plate having a line-shaped illumination opening,
5. The confocal microscope according to claim 1, wherein a focal position opening through which light received by the focal position sensor is transmitted is provided in the slit plate. 6.   When the observation detector receives linear light with the focus being adjusted by the focus adjustment means, the light shielding member does not shield part of the light from the light source. A confocal microscope according to any one of claims 1 to 5. A confocal image capturing method for detecting light through a confocal optical system and capturing a confocal image,
Shielding a part of the light with a light shielding member disposed on the optical path;
Scanning the shielded light by a scanning means;
Condensing and irradiating the scanned light onto the sample;
Detecting reflected light reflected by the sample with a focus position sensor;
Adjusting the focus of the sample based on the output from the focus position sensor;
Scanning the line-shaped light with the scanning means in a state where the focus of the sample is adjusted;
Condensing and irradiating the sample with linear light scanned by the scanning means;
Of the line-shaped light irradiated to the sample, the reflected light reflected by the sample or the transmitted light transmitted through the sample is confocal-optic by an observation detector having a pixel array corresponding to the line-shaped light. And a step of receiving light through a system.   8. The method of capturing a confocal image according to claim 7, wherein in the step of adjusting the focus of the sample, the focus is adjusted based on an integrated value obtained by integrating the output from the focus position sensor.   9. The method of capturing a confocal image according to claim 8, wherein a clamping operation that does not increase or decrease the integral value is performed at the scanning end of the scanning unit.   The method for capturing a confocal image according to claim 8 or 9, wherein the integrated value is reset at one end of scanning of the scanning unit. The linear light is generated by a slit plate having a linear illumination opening,
11. The controller according to claim 7, wherein the focus position sensor detects reflected light that has passed through a focus position opening provided in the slit plate and reflected by the sample. A method for capturing a focal image.   12. The confocal image capturing method according to claim 7, wherein in the step of scanning the line-shaped light by the scanning unit, a part of the light is not shielded.

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