JP2004177307A - Optical measuring device using photoelectron multiplier for photo acceptance unit, confocal microscope system and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To adjust into the appropriate amount of light received by preventing a photoelectron multiplier from being saturated without giving adverse effects to an optical system and a light source driving circuit containing an optical path of a projecting side, and to obtain an image with high reliability. <P>SOLUTION: This optical measuring device receives light from a sample wk by using the photoelectron multiplier 19 as a photo acceptance unit through a pinhole of a pinhole plate 9, and observes or measures the sample wk based on an electric signal corresponding to the amount of light received output from the photoelectron multiplier 19. A ND filter 49 limiting the light transmission quantity is arranged between the pinhole of the pinhole plate 9 and the photoelectron multiplier 19. Means 70, 71, 72 for changing the light transmission quantity by the ND filter are arranged. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical measurement device that receives light from a sample through a pinhole with a photomultiplier tube, and observes or measures the sample based on an electric signal corresponding to the amount of light received from the photomultiplier tube.
[0002]
[Prior art]
There is a confocal microscope as such an optical measuring device. A confocal microscope scans a sample with monochromatic light emitted from a light source such as a laser, receives light from the sample with a light-receiving element via a confocal optical system, and based on the amount of received light, a super-focus depth image of the sample. Information such as height and height distribution. For example, when the distance between the sample placed on the stage and the objective lens is changed in the optical axis direction, the amount of light incident on the light receiving element via the confocal optical system, that is, the amount of received light changes, and the surface of the sample changes. The amount of received light is maximized when the object is in focus. Therefore, height information of the surface of the sample is calculated from the relative distance between the sample and the objective lens when the maximum amount of received light is obtained, and the height distribution of the surface of the sample is obtained by scanning the surface of the sample with light. be able to.
[0003]
The acquired height distribution is displayed on the screen of the display device by, for example, three-dimensional display. Alternatively, the height distribution replaced with a luminance distribution or a color distribution is displayed on the screen. A CRT (cathode ray tube) or an LCD (liquid crystal display) is used as a display device, and a controller for control, a display device, a console, and the like are connected to the confocal microscope to form a confocal microscope system.
[0004]
In addition, by connecting information on the amount of light received when each point (pixel) on the sample surface is focused (that is, information on the maximum luminance of each pixel), a monochrome image of the sample surface with a very deep depth of focus can be obtained. Can be. This image is a so-called super-depth image.
[0005]
In the above confocal microscope system, a photomultiplier tube (photomultiplier tube) is often used as a light receiving element. A photomultiplier is a vacuum tube composed of a photocathode, a secondary electron multiplying mechanism, and an anode.Photoelectrons emitted when light enters the photocathode are multiplied and collected by the anode. It is taken out. By using a multistage secondary electron emission surface, a large multiplication factor (high light receiving sensitivity) can be obtained.
[0006]
In an optical measuring device using such a photomultiplier tube as a light receiving element, particularly in a confocal microscope, when a sample having a very high light reflectance such as a mirror surface is measured (observed), an excessive amount of light increases. A photocurrent exceeding the maximum rating flows into the multiplier and the photomultiplier may be destroyed.
[0007]
In order to prevent this phenomenon, the output of light (for example, laser light) emitted from the light source is reduced, or an ND filter that restricts the amount of transmitted light is inserted into the optical path on the light projecting side, thereby reducing the amount of light applied to the sample. Limiting the intensity (light quantity) is performed by a conventional confocal microscope. In addition, there is an optical measuring device capable of adjusting the photoelectric conversion efficiency (gain) of the photomultiplier tube itself so that a current exceeding the maximum rating does not flow through the photomultiplier tube.
[0008]
[Problems to be solved by the invention]
However, the method of lowering the output of light (for example, laser light) emitted from the light source may cause a deterioration in the S / N ratio in the case of, for example, a configuration in which a light receiving element for monitoring the amount of light is separately provided. When the light source is a semiconductor laser, its electrostatic breakdown state and life degradation can be determined from the operating current. However, if the operating current is reduced to reduce the output, electrostatic breakdown and life degradation may occur. It is difficult to accurately determine the progress. In addition, it is difficult to maintain a constant output due to external factors such as environmental temperature. To stabilize the output of a light source such as a semiconductor laser, it is desirable to design the drive circuit so as to be stable with a configuration as simple as possible.
[0009]
Further, the method of inserting an ND filter into the light path on the light projecting side to limit the amount of light requires high accuracy in fixing the ND filter. That is, unless the ND filter is fixed exactly at right angles to the optical axis, the optical axis shifts, and the optical performance may deteriorate due to an unexpected optical axis shift. In particular, when a plurality of ND filters having different light transmission amounts (light transmittances) are switched and used, all the ND filters need to be accurately perpendicular to the optical axis. , Which increases manufacturing costs.
[0010]
In addition, the method of adjusting the photoelectric conversion efficiency (gain) of the photomultiplier tube itself so that a current exceeding the maximum rating does not flow through the photomultiplier tube has the following problem. That is, if the light incident on the light receiving surface of the photomultiplier tube is too strong, a saturation phenomenon (a phenomenon in which the photocurrent does not increase in proportion to the amount of received light) occurs on the light receiving surface itself. A photomultiplier tube can output a photocurrent following an instantaneous large amount of light, but has a characteristic that when a large amount of light continuously enters, the output is reduced due to saturation. As a result, ringing occurs in the output current.
[0011]
When an image of the sample surface is acquired by scanning the sample surface with laser light, a phenomenon such as a white tail in the scanning direction occurs at the edge of the image where the light reflectance of the sample surface switches from low to high. May occur. This is because, in a portion where a dark portion having a low light reflectance changes to a bright portion having a high light reflectance, a brighter portion is displayed than a surrounding bright portion. Such a phenomenon may not only deteriorate the appearance of the obtained image, but also adversely affect measurement accuracy and reliability.
[0012]
In view of the above problems, the present invention prevents saturation of a photomultiplier tube, adjusts an appropriate amount of received light, without affecting optical systems including a light path on a light emitting side and a light source driving circuit. It is an object of the present invention to provide an optical measurement device, a confocal microscope system, and a computer program capable of obtaining an image with high reliability.
[0013]
[Means for Solving the Problems]
An optical measurement apparatus according to the present invention is an optical measurement apparatus that receives light from a sample through a pinhole with a photomultiplier tube, and performs observation or measurement of the sample based on an electric signal corresponding to an amount of light received from the photomultiplier tube. The measuring device is characterized in that an ND filter for limiting the amount of light transmission is arranged between the pinhole and the photomultiplier tube, and means for changing the amount of light transmission by the ND filter is provided.
[0014]
According to such a configuration, saturation of the photomultiplier can be prevented without adversely affecting the optical system including the light path on the light projecting side and the light receiving element for monitoring the amount of light. That is, the arrangement accuracy of the optical element in the optical system after passing through the pinhole is not so severe compared to the optical system before passing through the pinhole. Further, in order to make full use of the performance of the photomultiplier, it is necessary to secure a certain distance between the pinhole and the photomultiplier. By arranging the ND filter by utilizing the space between the pinhole and the photomultiplier, saturation of the photomultiplier can be effectively prevented.
[0015]
The optical measuring device according to the present invention is preferably a confocal microscope system. That is, the confocal microscope system according to the present invention receives light from the sample via the confocal optical system with the light receiving element, acquires height information and light amount information on the surface of the sample based on the received light information, Is a confocal microscope system that displays an image of the surface of the screen on a screen. A photomultiplier tube is used as a light receiving element, and the amount of light transmission between the pinhole and the photomultiplier tube that constitute the confocal optical system is limited. An ND filter is provided, and means for changing the amount of light transmitted by the ND filter is provided.
[0016]
With such a configuration, it is possible to prevent saturation of the photomultiplier tube and adjust the amount of received light to an appropriate level without adversely affecting the optical system including the light path on the light emitting side and the light receiving element for monitoring the amount of light. A high image (such as a super-depth image) can be obtained.
[0017]
Further, a computer program according to the present invention is a program to be executed by a computer connected to the confocal microscope system, wherein the brightness of a screen display is increased by a predetermined amount of light slightly smaller than a limit at which a light receiving surface of a light receiving element is saturated. Adjusting the light-receiving gain so that the light-receiving gain is saturated, storing the adjusted light-receiving gain as a lower limit, and limiting the light-receiving gain to be lower than the lower limit when adjusting the brightness of the screen display by the user. Informing the user that it is necessary to reduce the amount of light transmitted by the ND filter to further reduce the brightness of the screen display.
[0018]
When setting and adjusting the measurement conditions of the confocal microscope system using a computer connected to the confocal microscope system, the intensity of light incident on the light receiving element (photomultiplier tube) by the computer program as described above. Is appropriately adjusted by the ND filter. As a result, saturation of the photomultiplier is prevented, and a highly reliable image can be obtained.
[0019]
Such a computer program is supplied in a state of being stored in a computer-readable storage medium such as a CD-ROM, and is installed in a computer from the storage medium and executed.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0021]
FIG. 1 shows a schematic configuration of a confocal microscope system which is an optical measurement device according to an embodiment of the present invention. The confocal microscope system 1 includes a confocal microscope having a confocal optical system 2 and a non-confocal optical system 3, a light source driving circuit 44 of the confocal microscope, a first AD converter 41, a CCD driving circuit 43, and a second AD conversion. A controller including a device 42, an objective lens moving mechanism 40, a controller 46 using a microcomputer, and the like, and a display device 47 and an input device (console) 48 connected to the controller are provided.
[0022]
First, the confocal optical system 2 of the confocal microscope and its signal processing will be described. The confocal optical system 2 includes a light source 10 for irradiating the sample wk with monochromatic light (for example, laser light), a collimating lens 11, a polarizing beam splitter 12, a quarter-wave plate 13, a horizontal / vertical deflection device 14, and a half mirror 15. , An objective lens 17, a PH lens 18, a pinhole plate 9, a light receiving element 19, and the like.
[0023]
As the light source 10, for example, a semiconductor laser is used. However, the light source 10 is not limited to a laser, and may be a monochromatic light source. Further, even if the light source is not a monochromatic light source such as a mercury lamp, it can be used as a monochromatic light source by combining with a band filter. The laser light emitted from the light source 10 driven by the light source drive circuit 44 passes through the collimator lens 11, the optical path is bent by the polarization beam splitter 12, and passes through the 波長 wavelength plate 13. Thereafter, the light is deflected in the horizontal (horizontal) direction and the vertical (vertical) direction by the horizontal / vertical deflection device 14, reflected by the half mirror 15 to bend the optical path, and placed on the sample stage 30 by the objective lens 17. The light is focused on the surface of the sample wk.
[0024]
The horizontal / vertical deflection device 14 includes a horizontal (resonant) scanner for horizontal deflection and a galvano (electromagnetic) scanner for vertical deflection. By deflecting the laser light in both the horizontal and vertical directions, the surface of the sample wk is scanned with the laser light. For convenience of description, the horizontal direction is referred to as an X direction, and the vertical direction is referred to as a Y direction. The objective lens 17 is driven in the Z direction (optical axis direction) by the objective lens moving mechanism 40. Thus, the distance between the focus of the objective lens 17 and the sample wk in the optical axis direction (that is, the height direction of the sample wk) can be changed.
[0025]
However, the distance in the optical axis direction between the focal point of the objective lens 17 and the sample wk can be changed by another method. For example, instead of driving the objective lens 17 in the Z direction, the sample stage 30 may be driven in the Z direction. Alternatively, a configuration in which the focal point of the objective lens 17 is moved in the Z direction by inserting a lens whose refractive index changes between the objective lens 17 and the sample wk is also possible.
[0026]
In the confocal microscope of the present embodiment, the objective lens 17 can be electrically moved in the Z-axis direction via the objective lens moving mechanism 40 by a control signal from the control unit 46, and the sample stage 30 is provided with a stage manual operation mechanism. It can be displaced in the X direction, the Y direction and the Z direction by a manual operation via 31. In addition, the objective lens 17 can be moved up and down via the control unit 46 and the objective lens moving mechanism 40 by a key operation of the input device 48 (for example, an operation of an up / down key).
[0027]
The laser beam reflected by the sample wk is reflected by the half mirror 15 through the objective lens 17 and reversely passes through the quarter-wave plate 13 via the horizontal / vertical deflection device 14 so as to follow the above optical path in reverse. . As a result, the laser light passes through the polarizing beam splitter 12 and is collected by the PH lens 18. The condensed laser light passes through the pinhole of the pinhole plate 9 arranged at the focal position of the PH lens 18, passes through the ND filter 49, and enters the light receiving element 19. The light receiving element 19 is constituted by a photomultiplier tube (photomultiplier tube), and converts the amount of received light into an electric signal. The electric signal corresponding to the amount of received light is provided to the first AD converter 41 via an output amplifier and a gain control circuit (not shown), and is converted into a digital value.
[0028]
The height (depth) information of the sample wk can be acquired by the confocal optical system 2 configured as described above. The principle will be briefly described below.
[0029]
As described above, when the objective lens 17 is driven in the Z direction (optical axis direction) by the objective lens moving mechanism 40, the relative distance in the optical axis direction between the focal point of the objective lens 17 and the sample wk changes. When the focus of the objective lens 17 is focused on the surface of the sample wk, the laser light reflected on the surface of the sample wk is condensed by the PH lens 18 through the above-described optical path, and almost all the laser light is focused. It passes through the pinhole of the hole plate 9. Therefore, at this time, the amount of light received by the light receiving element 19 is maximized. Conversely, when the focus of the objective lens 17 is shifted from the surface of the sample wk, the laser light condensed by the PH lens 18 focuses on a position shifted from the pinhole plate 9, so that a part of the laser light Only the pinhole can pass. As a result, the amount of light received by the light receiving element 19 is significantly reduced.
[0030]
Therefore, if the amount of light received by the light receiving element 19 is detected at any point on the surface of the sample wk while driving the objective lens 17 in the Z direction (optical axis direction), the objective lens 17 when the amount of received light is maximized is detected. (Distance in the optical axis direction between the focal point of the objective lens 17 and the sample wk) can be uniquely obtained as height information.
[0031]
In practice, each time the objective lens 17 is moved by one step (one pitch), the surface of the sample wk is scanned by the horizontal / vertical deflection device 14 to obtain the amount of light received by the light receiving element 19. When the objective lens 17 is moved in the Z direction from the lower end to the upper end of the measurement range in the Z direction, light reception amount data that changes according to the Z direction position is obtained for each point (pixel) in the scanning range.
[0032]
FIG. 2 is a graph illustrating an example of the amount of received light that changes according to the position of the objective lens 17 in the Z direction. Based on such received light amount data, the maximum received light amount and the Z-direction position at that time are obtained for each point (pixel). Therefore, the distribution of the surface height of the sample wk on the XY plane is obtained. This process is executed by the control unit 46 using a microcomputer.
[0033]
The obtained surface height distribution information can be displayed on the monitor screen of the display device 47 by several methods. For example, the height distribution (surface shape) of the sample can be displayed three-dimensionally by three-dimensional display. Alternatively, the height data can be converted into luminance data to be displayed as a two-dimensional distribution of brightness. By converting the height data into color difference data, the height distribution can be displayed as a color distribution.
[0034]
Further, a surface image (monochrome image) of the sample wk can be obtained from a luminance signal using the received light amount obtained for each point (pixel) in the XY scanning range as luminance data. If a luminance signal is generated using the maximum amount of received light in each pixel as luminance data, an ultra-deep image with an extremely deep focal depth focused at each point having a different surface height can be obtained. When the height (Z-direction position) at which the maximum amount of received light is obtained at an arbitrary pixel of interest is fixed, the amount of received light of a pixel having a large height difference from the pixel of interest is significantly small, and An image in which only portions having the same height are bright (ie, a slice image) is obtained.
[0035]
In FIG. 1, an ND filter 49 provided in front of a light receiving element (photomultiplier tube) 19 is a filter for limiting an amount of light transmission (transmittance), and enters the light receiving element (photomultiplier tube) 19. It has the function of limiting the light intensity (light amount). Further, a plurality of ND filters 49 having different light transmittances are arranged in an annular shape on the disk 70, and a motor 71 for rotating the disk 70 is provided. The control unit 46 controls the drive of the motor 71 via the drive circuit 72, and can switch between the plurality of ND filters 49. That is, the means for changing the amount of light transmitted by the ND filter 49 includes the disk 70, the motor 71, the drive circuit 72, and the like.
[0036]
It should be noted that the optical system after passing through the pinhole of the pinhole plate 9 is not so severe in the arrangement accuracy of the optical elements as compared with the optical system before passing through the pinhole. Therefore, there is no problem even if the ND filter 49 is added after the design of the optical system. In addition, since there is no need for the surface finishing or the anti-reflection coating treatment of the ND filter 49, the cost can be reduced.
[0037]
In order to make full use of the performance of the photomultiplier tube as the light receiving element 19, it is necessary to secure a certain distance between the pinhole plate 9 and the light receiving element 19. By arranging the ND filter 49 by effectively utilizing the space between the pinhole plate 9 and the light receiving element 19, the saturation of the light receiving element 19 can be effectively prevented. Further, since it is not necessary to adjust the output of the light source 10 for adjusting the amount of light received by the light receiving element 19, the configuration of the light source driving circuit 44 can be simplified. A method of adjusting the amount of light received by the light receiving element 19 (a method of adjusting the brightness of screen display) will be described later.
[0038]
Next, the non-confocal optical system 3 and its signal processing will be described. The non-confocal optical system 3 includes a white light source 20, a collector lens 21, a condenser lens 22, a filter half mirror 16, a half mirror 15, an objective lens for irradiating the sample wk with white light (illumination light for capturing a color image). 17, an imaging lens 23 and a color CCD (color image sensor) 24 are included. The half mirror 15 and the objective lens 17 are shared by the confocal optical system 2 and the non-confocal optical system 3, and the optical axis of the objective lens 17 is common to the confocal optical system 2 and the non-confocal optical system 3.
[0039]
For example, a white lamp is used as the white light source 20, but natural light or indoor light may be used without providing a special light source. The white light emitted from the white light source 20 passes through the collector lens 21 and the condenser lens 22, is reflected by the filter half mirror 16, the optical path is bent, passes through the half mirror 15, and is sampled on the sample stage 30 by the objective lens 17. It is focused on the surface of wk.
[0040]
The white light reflected by the sample wk passes through the objective lens 17 and the half mirror 15 so as to follow the above optical path in reverse. Then, the light passing through the filter half mirror 16 passes through the imaging lens 23 and enters the color CCD 24 to form an image. The color CCD 24 is provided at a position conjugate with or close to the pinhole of the pinhole plate 9 of the confocal optical system 2. The color image picked up by the color CCD 24 is read out by the CCD drive circuit 43, and its analog output signal is given to the second AD converter 42 and converted into a digital value.
[0041]
The filter half mirror 16 is formed of a metal film or a dielectric film on a filter glass in which impurities are mixed so as not to pass monochromatic light from the light source (semiconductor laser) 10 but to pass most components of white light from the white light source 20. Is deposited to form the reflection surface 16a. Therefore, the light that passes through the filter half mirror 16 and is imaged on the color CCD 24 by the imaging lens 23 hardly contains monochromatic light from the semiconductor laser 10. As a result, the possibility that the color CCD 24 (particularly the color filter) is damaged by the laser spot having a high energy density is eliminated. The color image obtained as described above is displayed on the monitor screen of the display device 47 as an enlarged color image for observing the sample wk. The color image is also useful for locating the surface of the sample to be measured such as an ultra-depth image using a confocal optical system. Further, the super-depth image obtained by the confocal optical system 2 and the normal color image obtained by the non-confocal optical system 3 are combined to obtain a deep color super-depth with a focal depth substantially in focus at all pixels. Images can also be generated and displayed.
[0042]
The controller including the control unit 46 is also in charge of the processing regarding the color image as described above. An input device 48 such as a console (operation console) and a display device 47 such as a CRT (cathode ray tube) or an LCD (liquid crystal display device) are connected to the controller.
[0043]
The user can set various measurement parameters using the input device 48 according to the guidance displayed on the screen of the display device 47. For example, a moving range (measurement range) and a moving pitch of the objective lens 17 in the Z direction are set. Alternatively, by setting the light receiving sensitivity (light receiving gain) of the light receiving element 19 and the light transmittance (attenuation) by the ND filter 49 in accordance with the light reflectance of the surface of the sample wk, the ultra-depth displayed on the screen is obtained. Adjust so that the image or slice image has appropriate brightness (luminance). Further, the shutter speed, gain, and white balance for obtaining a color image by the color CCD 24 are set.
[0044]
The confocal microscope system 1 (controller) of the present embodiment is also provided with a communication interface for connecting an external computer system such as a personal computer. By connecting an external computer system in which dedicated software for controlling the confocal microscope system 1 is installed to the confocal microscope system 1, processing of acquired image information and height distribution information of the sample wk can be performed seamlessly. It is possible to do.
[0045]
FIG. 3 is a block diagram illustrating an example of a hardware configuration in which an external computer system 50 is connected to a controller of the confocal microscope system 1. The external computer system 50 includes a display device 51 such as a CRT or LCD, a keyboard 52, a mouse (or another pointing device) 53, a communication interface 54 such as an RS232C, a USB (universal serial bus), IEEE1394, and a processing device (CPU). 55, a main memory 56 as a semiconductor storage medium, a fixed disk device 57 as an auxiliary storage device, and a removable disk device 58.
[0046]
The dedicated software for controlling the confocal microscope system 1 is supplied in a state stored in a storage medium 59 such as a CD-ROM, and is supplied from the storage medium 59 by a removable disk device 58 such as a CD-ROM drive. It is read and installed in the fixed disk device 57. The dedicated software installed in the fixed disk device 57 is loaded into the main memory 56 and executed by the processing device 55. The processing executed by such dedicated software includes processing for setting measurement conditions of the confocal microscope system 1 and processing of an image obtained as a result of the measurement.
[0047]
FIG. 4 is a diagram illustrating an example of a screen display of the display device 51 by the dedicated software. In a screen display 60 displayed on the display device 51, an image display area 61 on the left side is for displaying measurement results such as a color image, an ultra-depth image, a slice image, and a height distribution image obtained from the confocal microscope system 1. A vertically long operation section area 62 for setting measurement conditions is displayed on the right side of the area.
[0048]
FIG. 5 is an enlarged view of the operation section area 62 in the screen display 60 of FIG. By using the mouse 53 to operate a push button or a slide bar in the operation section area 62, select each pull-down menu, and the like, manual setting of each measurement parameter can be performed. For example, if the slide lever 63 for gain adjustment is moved up and down by a drag operation of the mouse 53, the light receiving sensitivity (light receiving gain) of the light receiving element 19 changes, and the brightness (luminance) of the image can be adjusted. The brightness (brightness) of the image can also be adjusted by moving the ND filter adjustment slide lever 64 adjacent thereto up and down to change the light transmission amount.
[0049]
Alternatively, by selecting an appropriate numerical value from a pull-down menu that appears when the triangle mark 65 on the right side of the distance is clicked with the mouse 53, the Z-direction movement range (measurement range) of the objective lens 17 can be set. Similarly, by selecting an appropriate numerical value from a pull-down menu that appears when the triangle mark 66 is clicked on the lower pitch, an appropriate Z-direction movement pitch can be set.
[0050]
In addition, if the measurement button 67 is pressed after appropriately setting various settings including the setting of the measurement mode and the scanning mode, the automatic measurement starts, and after a predetermined measurement time elapses, an ultra-depth image (or a color ultra-depth image) or The height distribution image appears in the image display area 61 of the screen display 60.
[0051]
FIGS. 6 and 7 are flowcharts relating to a method of adjusting the brightness of an image by adjusting the light receiving gain and adjusting the light transmittance of the ND filter. These flowcharts include a step in which the processing device 55 of the external computer system 50 performs processing according to dedicated software (computer program) and a user's operation step, which will be clarified in the following description.
[0052]
First, a process for setting the lower limit of the light receiving gain will be described with reference to FIG. In step # 101, the user causes a predetermined amount of light slightly smaller than the limit at which the light receiving surface of the photomultiplier tube (which may be abbreviated as PMT), which is the light receiving element 19, to enter the photomultiplier tube. In the following step # 102, the user adjusts the light receiving gain (PMT gain) so that the brightness of the screen display is saturated. Then, in step # 103, the processing device 55 stores the adjusted light receiving gain as a lower limit value. As described later, when the brightness is adjusted by the user, the processing device 55 notifies the user that an appropriate adjustment is performed using the stored lower limit.
[0053]
Saturation of the light receiving surface of the photomultiplier tube, which is the light receiving element 19, can be prevented if the intensity of light (incident light amount) incident on the light receiving surface does not exceed a certain value. When the brightness of the image generated from the output signal of the light receiving element 19 is too strong, the user performs an operation for lowering the brightness. That is, in the operation section area 62 shown in FIG. 5, the light receiving gain is reduced or the light transmission amount of the ND filter 49 is reduced (the attenuation amount is increased).
[0054]
At this time, when the amount of light transmitted through the ND filter 49 is reduced, the amount of light incident on the light receiving element 19 decreases, but when the light receiving gain is reduced, the amount of light incident on the light receiving element 19 remains unchanged. That is, even if the light receiving gain is reduced when the amount of incident light exceeds a certain value, the saturated state of the light receiving surface is not eliminated. Therefore, as in the above steps # 101 to # 103, the light receiving gain is set so that the brightness of the screen display is saturated when the light amount slightly smaller than the limit at which the light receiving surface of the light receiving element 19 is saturated. Is adjusted, and the adjusted light receiving gain is stored.
[0055]
Next, brightness adjustment by the user is performed according to the flowchart of FIG. If the user determines in step # 201 that the brightness of the screen display is saturated, the user lowers the light receiving gain (PMT gain) in the next step # 202. As a result, when the saturated state has been eliminated (Yes in step # 203), the adjustment process ends. However, when the saturated state has not been eliminated yet (No in step # 203), the user attempts to further reduce the light receiving gain. I do. At this time, the processing device 55 reads out the stored lower limit value of the light receiving gain and compares it with the current light receiving gain in step # 204. If the current light receiving gain is larger than the lower limit, the process returns to step # 202 to allow further adjustment to further reduce the light receiving gain. However, if the current light receiving gain reaches the lower limit (No in step # 204), the next step is performed. In step # 205, the user performs adjustment to reduce the transmission amount of the ND filter 49.
[0056]
At this time, the processing device 55 restricts the light receiving gain from falling below the lower limit value and notifies the user that it is necessary to reduce the amount of light transmitted by the ND filter 49 in order to further reduce the brightness of the screen display. For example, in the operation section area 62 shown in FIG. 5, a message that prohibits the downward movement of the gain adjustment slide lever 63 for lowering the light receiving gain and prompts the ND filter 49 to reduce the amount of light transmitted is displayed. indicate.
[0057]
If it is determined in the next step # 206 that the saturated state has been eliminated, the adjustment process is terminated. If it is determined that the saturated state has not been eliminated, the process returns to step # 205 to further reduce the transmission amount of the ND filter 49. Adjustments will be made.
[0058]
According to the brightness adjustment method as described above, when the user performs the adjustment to reduce the brightness of the screen, the user cannot reduce the transmission amount by the ND filter 49 because the adjustment cannot only be performed to reduce the light reception gain but to the desired brightness. Since the adjustment for lowering is performed, the amount of light incident on the light receiving element can always be suppressed to be equal to or less than the saturated amount of light. Thus, a highly reliable image can be obtained.
[0059]
As described above, the embodiments of the present invention have been described including the modified examples as appropriate. However, the present invention is not limited to the above embodiments, and can be implemented in various forms. For example, the optical measuring device of the above embodiment is a reflection type color confocal microscope, but the present invention can be applied to a transmission type color confocal microscope. In the case of a transmission type color confocal microscope, laser light of a confocal optical system and white light of a non-confocal optical system are emitted from the back surface of the sample. The monochromatic light source used in the confocal optical system is not limited to the laser light source, and the monochromatic light source may be configured by a combination of a light source including a plurality of wavelengths such as a mercury lamp and a band filter. The light source of the non-confocal optical system can be replaced by natural light or room light. Further, the present invention is not limited to a confocal microscope, but can be widely applied to an optical measuring device using a photomultiplier tube as a light receiving element.
[0060]
【The invention's effect】
As described above, according to the optical measurement device, the confocal microscope system, and the computer program of the present invention, the ND filter is provided between the pinhole and the photomultiplier tube as the light receiving element, and the light transmission amount is provided. , The saturation of the photomultiplier can be effectively prevented without complicating the optical system including the light path on the light projecting side, the driving circuit of the light source, and the like.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a confocal microscope system which is an optical measurement device according to an embodiment of the present invention.
FIG. 2 is a graph illustrating an example of a light receiving amount that changes according to a Z-direction position of an objective lens.
FIG. 3 is a block diagram illustrating a hardware configuration example in which an external computer system is connected to a controller of the confocal microscope system.
FIG. 4 is a diagram showing an example of a screen display of a display device using dedicated software.
FIG. 5 is an enlarged view of an operation unit area in the screen display of FIG. 4;
FIG. 6 is a flowchart illustrating a method of adjusting the brightness of an image by adjusting the light receiving gain and adjusting the light transmittance of the ND filter.
FIG. 7 is a flowchart illustrating a method of adjusting the brightness of an image by adjusting the light receiving gain and adjusting the light transmittance of the ND filter.
[Explanation of symbols]
2 confocal optical system 9 pinhole plate 17 objective lens 19 light receiving element (photomultiplier tube)
24 color imaging device (color CCD)
49 ND filters 70, 71, 72 Means wk for changing light transmission amount by ND filter Sample

Claims (4)

An optical measurement device that receives light from a sample through a pinhole with a photomultiplier tube and performs observation or measurement of the sample based on an electric signal corresponding to a received light amount output from the photomultiplier tube,
An optical measurement device, comprising: an ND filter that restricts an amount of light transmitted between the pinhole and the photomultiplier tube; and a unit that changes an amount of light transmitted by the ND filter. Light from a sample is received by a light receiving element via a confocal optical system, height information and light amount information of the surface of the sample are acquired based on the received light information, and an image of the surface of the sample is displayed on a screen. A focus microscope system,
A photomultiplier tube is used as the light receiving element, and an ND filter for limiting an amount of light transmission is arranged between a pinhole constituting the confocal optical system and the photomultiplier tube. A confocal microscope system comprising means for changing the amount. A program to be executed by a computer connected to the confocal microscope system,
Adjusting the light receiving gain so that the brightness of the screen display is saturated by a predetermined amount of light slightly smaller than the limit at which the light receiving surface of the light receiving element is saturated;
Storing the light reception gain after the adjustment as a lower limit value,
When adjusting the brightness of the screen display by the user, the user is required to limit the light reception gain from falling below the lower limit value and to reduce the amount of light transmitted by the ND filter in order to further reduce the brightness of the screen display. A computer program. A computer-readable storage medium on which the computer program according to claim 3 is recorded.

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