JP2013160815A - Microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microscope capable of carrying out speedy and correct autofocus processing in accordance with the type of a sample and/or an operation mode.SOLUTION: The microscope condenses light from a sample, placed on a stage, by use of an objective lens, and picks up an image of the sample on the basis of the condensed light, thereby creating image data for observation. The microscope includes a control section that carries out autofocus such that an image of a sample is automatically focused using a target value for automatic exposure determined in accordance with the type of the sample and/or an operation mode for the microscope.

Description

  The present invention relates to a microscope having a function of forming an image of a sample to be observed and capturing the image.

  2. Description of the Related Art In recent years, in the field of a microscope, an image pickup apparatus such as a digital camera having an autofocus (AF) function is mounted and an image captured by the image pickup apparatus is displayed on a display unit. In AF processing of an image pickup apparatus, a method (contrast AF) in which adjacent pixels in an image pickup device such as a CCD are compared and contrast calculation is performed, and a position where the contrast calculation value is maximized is used as a focus position (contrast AF) has been put into practical use. .

  In contrast AF in microscopic observation, the position of a focusing unit such as a stage that moves up and down by electric control (hereinafter referred to as the Z position) is changed, and then Z position information is obtained from a control unit such as a CPU. A hill-climbing method is widely put into practical use in which the Z position information is acquired and registered as image position information, and the in-focus position where the contrast value is maximized is obtained from the result of contrast calculation. The contrast calculation in this hill-climbing method is generally calculated by averaging the difference between adjacent pixels or the square of the difference between adjacent pixels over the entire pixel or a specified range.

  As an example of contrast AF, a technique for performing contrast AF while moving the stage from the AF start position at a fine pitch is disclosed (for example, see Patent Document 1). In this technique, in order to increase the contrast AF, a coarse focus operation (hereinafter referred to as Rough scan) with a large stage drive pitch and a fine focus operation (hereinafter referred to as Fine scan) with a small stage drive pitch. Two types of AF processing are performed. More specifically, after finding a rough focus position by the Rough scan, an accurate focus position is found by the Fine scan. In this technique, image data captured by the imaging device is acquired and contrast calculation is performed. However, the exposure time must be optimized every time imaging is performed, and there is a problem that AF processing takes time. .

  In order to solve the problem of Patent Document 1 described above, a technique is disclosed in which a charge accumulation condition suitable for an observation condition is set, and an optimum exposure time is determined based on this condition and the output value of the image sensor ( For example, see Patent Document 2). According to this technique, a quick and stable AF process can be performed.

JP-A-10-197784 JP-A-7-13064

  However, in the case of the method of controlling the exposure time as in the above-described prior art, for example, when using the following sample, focusing cannot be performed by AF.

(1) A sample that easily causes halation A sample made of metal or the like. In this case, when halation occurs, the contrast is lost due to whiteout at the focus position, and focusing cannot be performed by AF.

(2) Calibration sample The calibration sample is a sample used when zoom calibration is performed, and is a sample obtained by vapor-depositing a metal pattern whose pitch dimension is known in advance on the surface of a glass substrate. When performing calibration using calibration samples, the number of pixels is counted at each zoom magnification for several points in the zoom stroke, and the error rate is calculated by comparing with the number of pixels at the ideal magnification. Is interpolated with a predetermined function to correct the magnification error for XY plane measurement for the entire zoom region.

  FIG. 13 is a diagram illustrating a configuration of a sample used when measuring the zoom magnification error. A calibration sample 201 shown in the figure is a line and space (L / S) sample in which a metal pattern is formed on the surface of a glass substrate by vapor deposition or the like. On the surface 202 of the calibration sample 201, an L / S pattern LS1 for a high magnification objective lens, an L / S pattern LS2 for a medium magnification objective lens, and an L / S pattern LS3 for a low magnification objective lens are formed. . Each L / S pattern has a different line width and pitch. For example, the low magnification is 5 times or less, the medium magnification is 5 to 20 times, and the high magnification is 20 times or more.

  FIG. 14 is a diagram illustrating a display example of a microscope image of the calibration sample 201. In the microscopic image 301 shown in the figure, the light and darkness of the glass and the metal L / S pattern are reversed. That is, in the microscope image 301, the luminance value of the image portion of the metal portion having a high reflectance is high (white), and the luminance value of the image portion of the glass portion having a low reflectance is low (black).

  The measurement of the line width and space width of the calibration sample is generally obtained from the number of pixels corresponding to the half width from the maximum value (peak) of the contrast calculation value. For this reason, in order to perform accurate line width measurement, it is necessary that the image luminance value is not saturated and the target value for automatic exposure is low (underexposure). FIGS. 15 and 16 are a diagram showing a microscopic image when the target value of automatic exposure is low (70) and a partially enlarged view of a luminance profile on a straight line. FIGS. 17 and 18 are a diagram showing a microscopic image when the target value of automatic exposure is high (180), and a partially enlarged view of a luminance profile on a straight line. As shown in FIGS. 17 and 18, when the luminance of the image is saturated, an accurate line width measurement result cannot be obtained. Thus, in order to perform accurate line width measurement, it is desirable that the target value for automatic exposure is low.

  When performing zoom calibration, in order not to cause focus shift during calibration due to zoom magnification, after performing calibration at a zoom high magnification with a relatively small depth of focus, zoom low Perform calibration at doubling. In this case, when AF is first performed at a zoom high magnification, it is necessary to search for a focus in a narrow focal depth range within a wide search range, which takes time. Therefore, in order to increase the calibration speed, it is common to perform AF at a zoom high magnification after performing AF at a zoom low magnification.

  However, when the exposure during the AF process is under, the amount of light received by the image sensor is drastically reduced at a position that is greatly out of focus during AF, and the microscope image becomes dark. This tendency becomes prominent when further defocusing is performed. When calculating the contrast value, since adjacent pixels of the image element are compared, if the microscope image becomes dark, noise appears in the luminance and the contrast value increases. As an example of such a case, FIG. 19 shows a position (AF) that deviates greatly from the focus position when the target value for automatic exposure is 70 at a zoom high magnification in which the amount of light incident on the image sensor changes dramatically in and out of focus. It is a figure which shows the brightness | luminance profile on the straight line of the position corresponding to a starting position. FIG. 20 is a diagram showing a linear luminance profile when the exposure conditions such as the shutter speed and gain of the image sensor are the same as those in FIG. 19 and the target value of automatic exposure is 100. From the state shown in FIG. FIG. 6 is a diagram showing a luminance profile on a straight line in a state where the focus position is approached. As is clear from the comparison between FIG. 19 and FIG. 20, the amount of light incident on the image sensor increases as it approaches the focus position, so that the image luminance value increases and the noise component also decreases. For this reason, the contrast value decreases as the focus position is approached.

As described above, when AF is performed from a position that is greatly deviated from the focus position in a noise-added image, the contrast value decreases as the focus position is approached, and the image is focused at a position different from the focus position to be detected by the main body. Phenomenon (false focus) occurs. FIG. 21 is a diagram for explaining a situation in which false focusing occurs. After focusing on the surface 202 of the calibration sample 201 by AF processing at low zoom magnification, when AF processing is performed with the zoom magnification at the maximum, the contrast rises closer to the near side than the original peak position. (Contrast curve CH). Therefore, when performing zooming high magnification AF processing, go to Near side from the position O focus low contrast, starting from the position P ₁ after the transfer contrast processing, the search at a position where the contrast curve CH rises For this reason, a change corresponding to falling from the peak is detected, and false focusing is performed at a position P ₂ different from the focusing position.

  On the other hand, if the target value for automatic exposure is high (overexposure), the exposure time becomes longer and the amount of light received by the image sensor is integrated, so the noise component decreases dramatically and contrast increases. The value becomes smaller. FIG. 22 is a diagram showing a luminance profile on a straight line when the target value for automatic exposure is 200 at a position far from the focus position (position corresponding to the AF start position). In FIG. 22, it can be seen that the noise is dramatically reduced as compared with the luminance profiles shown in FIGS.

  As described above, the target value for automatic exposure varies depending on the conditions such as the sample and operation mode. It was not considered.

  The present invention has been made in view of the above, and an object of the present invention is to provide a microscope capable of executing a quick and accurate autofocus process according to a sample type and / or an operation mode.

  In order to solve the above-described problems and achieve the object, the microscope according to the present invention condenses light from a sample placed on a stage by an objective lens, and the above-described light is collected based on the collected light. A microscope that generates image data for observation by taking an image of a sample, and using an automatic exposure target value determined according to the type of the sample and / or the operation mode of the microscope, A control unit that performs autofocusing that automatically focuses an image is provided.

  Further, in the microscope according to the present invention, in the above invention, the sample type is classified into a plurality of types according to reflectance, and the target value of the automatic exposure has a smaller value as the reflectance is higher. Features.

  In the microscope according to the present invention, in the above invention, the operation mode is an autofocus mode in which an image of the sample is automatically focused, and a line width of a line and space provided in a predetermined sample is measured. A line width measurement mode, and the target value of the automatic exposure is larger than the value set in the line width measurement mode when the auto focus mode is set.

In the microscope according to the present invention, in the above invention, the control unit performs peak determination of the contrast value in the autofocus based on a ratio of a contrast value obtained thereafter with respect to the peak candidate value, The target value of the automatic exposure is a value that satisfies the following conditional expression (1) using the target value as a parameter:
Contrast value due to noise x AF determination threshold <background noise (1)
Here, the background noise is the saturation value of the contrast value when the target value of the automatic exposure is changed at an out-of-focus position, or the minimum value of the contrast value in the contrast curve of the focus surface of the sample.

Further, in the microscope according to the present invention, in the above invention, the control unit performs the peak determination of the contrast value in the autofocus based on a comparison between the peak candidate value and a predetermined reference value, and the automatic exposure. The target value is a value that satisfies the following conditional expression (2) using the target value as a parameter:
Contrast value due to noise <peak value−reference value (2)

  According to the present invention, the auto-focus that automatically focuses the image of the sample is performed using the target value of the automatic exposure determined according to the sample type and / or the operation mode of the microscope. And / or quick and accurate autofocus processing can be executed according to the operation mode.

FIG. 1 is a diagram showing a configuration of a microscope according to Embodiment 1 of the present invention. FIG. 2 is a diagram showing AE target values for each sample stored in the storage unit included in the microscope according to Embodiment 1 of the present invention. FIG. 3 is a diagram showing a contrast curve obtained as a result of an experiment using a calibration sample in the microscope according to the first embodiment of the present invention. FIG. 4 is a diagram showing the relationship between the AE steps stored in the storage unit included in the microscope according to Embodiment 1 of the present invention and the shutter speed of the image sensor. FIG. 5 is a diagram showing a display example on the monitor screen of the display device included in the microscope according to Embodiment 1 of the present invention. FIG. 6 is a flowchart showing an outline of AF processing performed by the microscope according to Embodiment 1 of the present invention. FIG. 7 is a diagram illustrating an outline of AF processing performed by the microscope according to the first embodiment of the present invention. FIG. 8 is a flowchart showing an outline of the one-shot AE process performed by the microscope according to the first embodiment of the present invention. FIG. 9 is a diagram showing a configuration of a microscope according to Embodiment 2 of the present invention. FIG. 10 is a diagram illustrating AE target values for each mode stored in the storage unit included in the microscope according to Embodiment 2 of the present invention. FIG. 11 is a diagram illustrating a display example on the monitor screen of the display device included in the microscope according to the second embodiment of the present invention. FIG. 12 is a flowchart showing an overview of zoom calibration processing performed by the microscope according to the second embodiment of the present invention. FIG. 13 is a diagram illustrating a configuration of a calibration sample. FIG. 14 is a diagram illustrating a display example of a microscope image of a calibration sample. FIG. 15 is a diagram showing a microscopic image when the target value for automatic exposure is 70. FIG. FIG. 16 is a diagram showing a microscopic image when the target value for automatic exposure is 70. FIG. 17 is a partially enlarged view of a luminance profile on a straight line when the target value of automatic exposure is 180. FIG. 18 is a partially enlarged view of a luminance profile on a straight line when the target value of automatic exposure is 180. FIG. 19 shows a luminance profile on a straight line at a position greatly deviating from the focus position when the target value of the automatic exposure of the automatic exposure is 70 and the zoom is high in which the amount of incident light on the image sensor changes dramatically in and out of focus. FIG. FIG. 20 is a diagram showing a linear luminance profile in a state where the exposure conditions such as the shutter speed and gain of the image sensor are the same as those in FIG. 19 and closer to the focus position than in the state shown in FIG. FIG. 21 is a diagram for explaining a situation in which false focusing occurs. FIG. 22 is a diagram showing a luminance profile on a straight line when the target value of automatic exposure is 200.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as “embodiments”) will be described with reference to the accompanying drawings. The drawings referred to in the following description are schematic, and when the same object is shown in different drawings, the dimensions, scales, and the like may be different.

(Embodiment 1)
FIG. 1 is a diagram showing a configuration of a microscope according to Embodiment 1 of the present invention. The microscope 1 shown in FIG. 1 has an autofocus (AF) function, and includes a microscope mount 2, a stage 3, a light projection tube 4, an imaging device 5, a control device 6, and a display device 7.

The microscope mount 2 includes a stage support portion 21 that fixes and supports the stage 3, a light projection tube support portion 22 that supports the light projection tube 4 so as to move up and down, and a drive motor that controls the vertical movement of the light projection tube 4. And a control unit 23.
The drive motor control unit 23 moves the light projecting tube 4 and the imaging device 5 up and down by driving a drive motor 45 included in the light projecting tube 4 based on the motor drive amount sent from the control device 6.

The light projecting tube 4 includes an imaging optical system 41, a light source 42, a light source control unit 43, a half mirror 44, and a drive motor 45. The light projecting tube 4 holds the objective lens 8.
The light emitted from the light source 42 is reflected by the half mirror 44 and applied to the sample Sp placed on the stage 3 via the objective lens 8. On the other hand, the light reflected by the sample Sp passes from the objective lens 8 via the half mirror 44, passes through the imaging optical system 41, is condensed by the image sensor 51, and is photoelectrically converted into an electric signal.
The drive motor 45 has a function of a drive unit that drives the light projecting tube 4 and the imaging device 5. Hereinafter, the light projecting tube 4 and the imaging device 5 are collectively referred to as a “head portion”.

  The imaging device 5 includes an imaging device 51 such as a CCD or a CMOS, a signal processing unit 52 that performs signal processing such as A / D conversion on a signal acquired by the imaging device 51, and imaging that controls the operation of the imaging device 5. And a control unit 53.

The control device 6 includes an input unit 61, a contrast calculation unit 62, a storage unit 63, and a control unit 64.
The contrast calculation unit 62 receives image data from the imaging device 5 and performs contrast calculation for performing contrast calculation for calculating the contrast value of the image data.

  The storage unit 63 stores the AE target value for each sample and the relationship between the AE step and the shutter speed table of the image sensor. The storage unit 63 stores a program (application software) that controls the operation of the microscope 1.

FIG. 2 is a diagram showing AE target values for each sample stored in the storage unit 63. The table Tb1 shown in the figure records the AE target value for each sample classified by the sample reflectance. As the AE target value, a value obtained by acquiring a contrast curve in advance for each sample and satisfying the following conditional expression (1) is stored.
Contrast value due to noise x AF determination threshold <background noise (1)
Here, for example, 1/2 can be taken as the AE determination threshold value that gives the ratio of the contrast value obtained thereafter with respect to the peak (candidate value). The background noise on the right side will be described below with reference to FIG.

FIG. 3 is a diagram showing a contrast curve obtained as a result of an experiment using a calibration sample in the microscope 1. In FIG. 3, a contrast value larger than the true peak value is present in the contrast curve C ₁ when the exposure condition is fixed due to underexposure (AE70) at the Z position (Z position at the start of AF) that is greatly out of focus. This occurs on the near side of Z and may cause false focus. On the other hand, the contrast curve C ₂ in the case of overexposure (AE210) at a Z position (Z position at the start of AF) that is greatly out of focus, with a fixed exposure condition, has a contrast larger than the true peak value. There is no value. For this reason, there is a high possibility that focusing can be performed with a true peak value. As described above, in the AF mode, when the target value of moving exposure is high (overexposure), false focusing is less likely to occur. In FIG. 3, background noise refers to the contrast value at a position where the contrast value is saturated by changing the AE target value at an out-of-focus position (point A), or the bottom position (point of the contrast curve on the focus surface of the sample). This is the contrast value (minimum value) in B).

  FIG. 4 is a diagram illustrating a relationship between the AE step stored in the storage unit 63 and the shutter speed of the image sensor. In the table Tb2 shown in the figure, the shutter speeds of the image pickup elements in 10 stages of AE table numbers 1 to 10 are recorded.

  The control unit 64 is configured using a CPU or the like, and comprehensively controls the operation of the microscope 1 as a whole. The control unit 64 performs autofocus for automatically focusing the image of the sample Sp using a target value for automatic exposure determined according to the type of the sample Sp to be observed. The control unit 64 writes and stores the maximum value of the calculation result by the contrast calculation unit 62 and the Z coordinate when the maximum value is obtained in the storage unit 63. The control unit 64 transmits an instruction signal for adjusting the brightness of the light source 42 to the light source control unit 43.

  The display device 7 includes a monitor screen for displaying a microscope image and the like, and a microscope operation GUI touch panel. A touch panel is laminated | stacked on a monitor screen, and receives the input signal according to the contact position from the outside.

  FIG. 5 is a diagram illustrating a display example on the monitor screen of the display device 7. A display image 70 shown in the figure includes a microscope image display unit 71 that displays a microscope image, a focus operation input unit 72 that can input an operation signal when operating the head unit to perform a focus operation, and an autofocusing unit. An AF operation input unit 73 capable of inputting an AF signal for instructing execution and a light source operation input unit 74 capable of inputting a signal for operating brightness and on / off of the light source 42 are provided. When there is a contact from the outside on the icon portion displayed on each of the operation input units 72 to 74, the touch panel detects the contact and receives an input of a signal corresponding to the contact position.

  The AF operation input unit 73 displays an AF icon 731 for instructing execution of AF processing and sample reflectance icons 732 to 734 for selecting the reflectance of the sample. The sample reflectance icon 732 is an icon for selecting a reflectance of “60% or more”, the sample reflectance icon 733 is “10% -60%”, and the sample reflectance icon 734 is a reflectance of “10% or less”. An example of a sample with a sample reflectance of 60% or more is a metal, an example of a sample with a sample reflectance of 10% -60% is a substrate, and an example of a sample with a sample reflectance of 10% or less is glass. .

  FIG. 6 is a flowchart showing an outline of AF processing performed by the microscope 1 having the above configuration. FIG. 7 is a diagram for explaining the outline of the AF process performed by the microscope 1.

  The control unit 64 sends a signal to the drive motor control unit 23 to drive the drive motor 45 so that the head unit moves to a predetermined AF start position (step S1).

  Subsequently, the control unit 64 executes a one-shot AE process (step S2). FIG. 8 is a flowchart showing an outline of the one-shot AE process. First, the control unit 64 acquires the AE target value of the currently selected sample from the table Tb1 stored in the storage unit 63 (step S21).

  Subsequently, the control unit 64 acquires a shutter speed corresponding to the current AE table number from the table Tb2 stored in the storage unit 63, and transmits shutter speed setting information to the imaging control unit 53 (step S22). ). The initial value of the AE table number is 5.

  Thereafter, the control unit 64 acquires image data from the imaging device 5 and calculates an average luminance value in the designated range (step S23).

  Subsequently, the control unit 64 compares the average luminance value calculated in step S23 with a margin value predetermined for the AE target value (step S24). When the average luminance value is larger than AE target value−margin value and smaller than AE target value + margin value (step S24: Yes), the control unit 64 ends the one-shot AE process. On the other hand, when the average luminance value is equal to or less than the AE target value−margin value or equal to or greater than the AE target value + margin value (step S24: No), the microscope 1 proceeds to step S25.

  In step S25, the control unit 64 compares the current average luminance value with the target value (step S25). As a result of the comparison, when the average luminance value is smaller than the target value (step S25: Yes), the control unit 64 increases the AE table value by 1 (step S26) and returns to step S22. On the other hand, when the average luminance value is equal to or greater than the target value as a result of the comparison (step S25: No), the control unit 64 decreases the AE table value by 1 (step S27) and returns to step S22.

  The main routine of FIG. 6 will be described again. In step S3, the control unit 64 outputs an instruction signal for driving the drive motor 45 at a predetermined coarse search pitch to the drive motor control unit 23 (step S3).

  Subsequently, the control unit 64 acquires image data captured by the imaging device 5 (step S4), and performs contrast calculation (step S5).

Thereafter, the control unit 64 determines whether or not a search end condition is satisfied (step S6). The conditional expression for the search end condition is given by the following expression (3).
Contrast calculation peak value × 1/2> current contrast value (3)
Note that another value smaller than 1 may be applied instead of 1/2 of the left side. Further, instead of applying the expression (3) as the search end condition, for example, the search may be ended when the value of the contrast calculation becomes smaller a predetermined number of times after the peak value is exceeded.

  When the search condition is satisfied in step S6 (step S6: Yes), the control unit 64 proceeds to step S7. On the other hand, when the search condition is not satisfied in step S6 (step S6: No), the control unit 64 returns to step S3.

  In step S7, the control unit 64 calculates a fine search start position that is a position returned from the detected peak position (detected peak position) in the Far direction (step S7).

  Subsequently, the control unit 64 sends a signal to the drive motor control unit 23 to drive the drive motor 45 to move the head unit (step S8).

  Thereafter, the control unit 64 transmits a signal to the drive motor control unit 23 to drive the drive motor 45 at a predetermined fine search pitch (step S9). Thereafter, the control unit 64 acquires image data captured by the imaging device 5 (step S10), and performs contrast calculation (step S11).

  Subsequently, the control unit 64 determines whether or not the search end condition of the above expression (3) is satisfied (step S12). As a result of the determination, if the search end condition is satisfied (step S12: Yes), the head portion is moved to the detection peak position (step S13), and the series of AF processes is ended.

  According to the first embodiment of the present invention described above, AF can be executed under optimum conditions for each sample.

(Embodiment 2)
FIG. 9 is a diagram showing a configuration of a microscope according to Embodiment 2 of the present invention. A microscope 11 shown in the figure has an AF function, and includes a microscope mount 2, a stage 3, a light projecting tube 9, an imaging device 5, a control device 10, and a display device 7. The configuration of the microscope 11 excluding the light projecting tube 9 and the control device 10 is the same as that of the microscope 1 according to the first embodiment.

  In addition to the imaging optical system 41, the light source 42, the light source control unit 43, the half mirror 44, and the drive motor 45, the light projecting tube 9 includes a zoom optical system 91 that enlarges or reduces the optical image from the objective lens 8, and a zoom. A zoom motor 92 that drives the optical system 91 and a zoom motor control unit 93 that controls the operation of the zoom motor 92 are included. The zoom motor control unit 93 moves the zoom optical system 91 by driving the zoom motor 92 based on the drive amount sent from the control unit 64.

  The control device 10 includes an input unit 61, a contrast calculation unit 62, a storage unit 101, and a control unit 64. The control unit 64 performs autofocus for automatically focusing the image of the sample Sp using the target value of automatic exposure determined according to the operation mode of the microscope 1.

  The storage unit 101 stores a relationship between the set mode and the AE target value. FIG. 10 is a diagram illustrating AE target values for each mode stored in the storage unit 101. A table Tb3 shown in the figure stores AE target values in the AF mode and the calibration mode. The AE target value is previously determined by experiment and stored. This experiment is performed at the maximum zoom magnification.

  For the AF mode, a contrast curve is acquired in advance by an experiment using a calibration sample, and an AE target value that satisfies the above-described condition (1) is stored. As for the calibration mode, an image is acquired in advance with a calibration sample, and a value at which the image luminance value of the metal portion is not saturated is stored.

  FIG. 11 is a diagram illustrating a display example on the monitor screen of the display device included in the microscope 11. The display image 170 shown in the figure includes a microscope image display unit 171 that displays a microscope image, a focus operation input unit 172 that can input an operation signal when driving the head unit to perform a focus operation, and an autofocusing unit. An AF operation input unit 173 capable of inputting an AF signal instructing execution, a light source operation input unit 174 capable of inputting a signal for operating brightness and on / off of the light source 42, and a calibration signal instructing execution of calibration Calibration operation input unit 175 and zoom operation input unit 176 capable of inputting an instruction signal for changing the zoom magnification. When there is an external contact at the icon portion displayed on each of the operation input units 172 to 176, the touch panel detects the contact and receives an input of a signal corresponding to the contact position.

  FIG. 12 is a flowchart illustrating an overview of zoom calibration processing performed by the microscope 11. The control unit 64 sends a signal to the zoom motor control unit 93 to move the zoom motor 92 so that the zoom optical system 91 has a zoom magnification (minimum) for alignment (step S31).

  Subsequently, the control unit 64 acquires the AE target value of the currently selected sample from the table Tb1 stored in the storage unit 63, and transmits the AE target value setting information to the imaging control unit 53 (step S1). S32).

  Thereafter, the control unit 64 performs AF processing (step S33).

  After focusing in a state where the zoom magnification is minimum, the control unit 64 drives the zoom motor 92 via the zoom motor control unit 93, and the zoom magnification of the zoom optical system 91 is changed to the zoom magnification that is the calibration start magnification. (Maximum) (step S34).

  Thereafter, the control unit 64 executes the AF process again, and focuses with the zoom magnification at the maximum (step S35).

  Subsequently, in order to execute zoom calibration, the control unit 64 acquires an AE target value corresponding to the current mode from the table Tb3 stored in the storage unit 101, and sends the AE target value to the imaging control unit 53. Setting information is transmitted (step S36).

  Subsequently, the control unit 64 executes zoom calibration processing (step S37). Specifically, the microscope image is calibrated to an appropriate image. Thereafter, the AE process is executed while gradually reducing the zoom magnification, and the calibration process for measuring the L / S line width is executed until the zoom magnification is minimized. The zoom calibration process here is performed by a known method using the L / S pattern of the surface 202 of the calibration sample 201.

  According to the second embodiment of the present invention described above, AF can be executed under optimum conditions according to the operation mode (AF mode, line width measurement mode).

(Other embodiments)
So far, the embodiment for carrying out the present invention has been described, but the present invention should not be limited only by the embodiment described above. For example, in the present invention, the one-shot AE in the AF mode is not determined in advance by an experiment, but takes an exposure time with no noise in adjacent pixels by taking a line profile or a designated region of interest (ROI) at the start of AF. It may be used.

  In the present invention, the one-shot AE in the calibration mode may use an exposure time that does not saturate by taking a luminance profile on a straight line or a designated region of interest (ROI), rather than preliminarily determined by experiments. .

  In the present invention, overwriting for updating various tables may be performed.

  Also, in the present invention, the stage is pitch-pitched during AF, but the current coordinates may be acquired from the motor control unit for each imaging by continuously moving the light projection tube.

Further, in the present invention, when the peak determination of the contrast value in autofocus is performed based on a comparison between the peak candidate value and a predetermined reference value as an AF peak detection method, the AE target value is the target value. It is sufficient if the following conditional expression (2) is satisfied as a parameter.
Contrast value due to noise <peak value-reference value (2)

  In the present invention, the three tables Tb1 to Tb3 described above can be stored in the storage unit. In this case, display may be performed so that autofocus and calibration can be selected on the monitor screen of the display device, and autofocus corresponding to the sample reflectance can also be selected.

  As described above, the present invention can include various embodiments and the like not described herein.

DESCRIPTION OF SYMBOLS 1,11 Microscope 2 Microscope mount frame 3 Stages 4, 9 Projection tube 5 Imaging device 6, 10 Control device 7 Display device 8 Objective lens 21 Stage support part 22 Projection tube support part 23 Drive motor control part 41 Imaging optical system 42 Light source 43 Light source control unit 44 Half mirror 45 Drive motor 51 Imaging element 52 Signal processing unit 53 Imaging control unit 61 Input unit 62 Contrast calculation unit 63, 101 Storage unit 64 Control unit 70, 170 Display image 71, 171 Microscope image display unit 72 , 172 Focus operation input unit 73, 173 AF operation input unit 74, 174 Light source operation input unit 91 Zoom optical system 92 Zoom motor 93 Zoom motor control unit 175 Calibration operation input unit 176 Zoom operation input unit 201 Calibration sample 202 Surface 301 Microscope image 7 2-734 Sample reflectance icons C _1, C ₂ contrast curve Sp sample Tb1~Tb3 table

Claims (5)

A microscope that collects light from a sample placed on a stage by an objective lens and generates image data for observation by capturing an image of the sample based on the collected light,
A control unit that performs autofocusing that automatically focuses the image of the sample using a target value of automatic exposure determined according to the type of the sample and / or the operation mode of the microscope, Microscope. The sample types are classified into a plurality of types according to reflectance,
2. The microscope according to claim 1, wherein the target value of the automatic exposure has a smaller value as the reflectance is higher. The operation mode includes an autofocus mode for automatically focusing the image of the sample, and a line width measurement mode for measuring a line width of a line and space provided in a predetermined sample,
3. The microscope according to claim 1, wherein a target value of the automatic exposure is larger than a value set in the line width measurement mode when the auto focus mode is set. The controller is
The peak determination of the contrast value in the autofocus is performed based on the ratio of the contrast value obtained thereafter with respect to the peak candidate value,
The microscope according to any one of claims 1 to 3, wherein the target value of the automatic exposure is a value that satisfies the following conditional expression (1) using the target value as a parameter:
Contrast value due to noise x AF determination threshold <background noise (1)
Here, the background noise is the saturation value of the contrast value when the target value of the automatic exposure is changed at an out-of-focus position, or the minimum value of the contrast value in the contrast curve of the focus surface of the sample. The controller is
The peak determination of the contrast value in the autofocus is performed based on a comparison between the peak candidate value and a predetermined reference value,
The microscope according to any one of claims 1 to 3, wherein the target value of the automatic exposure is a value that satisfies the following conditional expression (2) using the target value as a parameter:
Contrast value due to noise <peak value−reference value (2)