JP5145698B2 - Microscope focus detection apparatus and microscope having the same - Google Patents

Description

  The present invention relates to a microscope focus detection apparatus and a microscope having the same.

  In recent years, with the increase in size of liquid crystal substrates, instead of the conventional method of placing a substrate on a microscope and observing it, a large-scale inspection in which the substrate is placed on a large stage and the microscope head moves on it. Devices are becoming popular. In the case of inspecting a substrate or the like using these, what is conventionally visually observed is taken with an imaging element, and an inspector inspects with a monitor. In order to improve the working efficiency, these apparatuses are required to have an autofocus apparatus (hereinafter, “autofocus” is simply referred to as AF).

  As a conventional AF device, for example, a so-called slit AF device that detects a focal point by projecting a single slit pattern on a sample surface and observing the slit pattern image is known. The slit AF apparatus generally shields the pupil to about half by using knife etching or the like at a position conjugate with the pupil position of the imaging optical system in the slit projection optical system. With this configuration, when the sample is displaced from the in-focus position, the slit image causes a lateral shift, so that the focus can be detected. In the case of such an AF apparatus, there is an advantage that the range in which AF control can be performed (referred to as “retraction range”) is wide. (For example, refer to Patent Document 1).

  There is also known a contrast AF device that projects a plurality of slit patterns instead of a single slit pattern, extracts the edge contrast of the pattern, and applies AF. In this case, since the frequency of the pattern to be projected is known, it is possible to remove the noise component using an electric bandpass filter when detecting the contrast signal, so that the focusing accuracy can be improved. (For example, refer to Patent Document 2).

There is also known an AF apparatus that performs AF based on the contrast of a specimen itself without performing slit or pattern projection. This is also called aka hill-climbing AF because a fitting curve is calculated from data obtained by once moving the specimen up and down to detect a contrast value and moved to the in-focus position. This is a problem that it is necessary to detect the signal once passing through the in-focus position in order to detect the in-focus position, and that it takes a long time to in-focus because of the calculation, Since there is no need for a special illumination system or the like, there is an advantage that it can be constructed at a low cost, but it is impossible in principle to use a follow-up type continuous AF.
JP 2001-42205 A JP 2001-242375 A

  However, the slit AF device has a wide pull-in range, but there is a problem in focusing accuracy when a fine pattern exists on the sample. In contrast, the contrast AF apparatus has high focusing accuracy, but the contrast signal intensity decreases even if it is slightly deviated from the in-focus position, so that the pull-in range is narrow.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a focus detection device for a microscope with a wide pull-in range and high focusing accuracy, and a microscope having the same.

To solve the above problems, the present invention includes a first projection optical system for projecting a single one slit Topa turn specimen via the objective lens, a multiple slit Topa turn the specimen via the objective lens A second projection optical system for projecting, an imaging optical system for forming an image of the single slit pattern and an image of the plurality of slit patterns on an image sensor via the objective lens, and the first projection optical system Includes a first light source, the second projection optical system includes a second light source, and includes a control unit that controls the first light source and the second light source, and the control unit includes the single light source. The shift from the focus detection of the slit pattern image by the image sensor to the focus detection of the plurality of slit pattern images by the image sensor is performed by switching the first light source and the second light source alternately. Slit pattern And the focus detection by the imaging device, the plurality slits of the pattern image the performs focus detection alternately by the image pickup device, the objective lens and changing the relative distance microscope focus detection, wherein the said sample Providing equipment.

  The present invention also provides a microscope comprising the microscope focus detection apparatus.

  According to the present invention, it is possible to provide a microscope focus detection device having a wide pull-in range and high focusing accuracy, and a microscope having the same.

  An AF apparatus according to an embodiment of the present invention and a microscope having the same will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a microscope including an AF apparatus according to an embodiment of the present invention. FIG. 2 is an explanatory diagram of an imaging apparatus mounted on the microscope of FIG. FIG. 3 shows a control flow of the AF apparatus.

  In FIG. 1, a microscope apparatus including an AF apparatus according to an embodiment includes a microscope main body 100 and an AF apparatus 200 that is provided in the microscope main body 100 and performs a focusing operation on a specimen.

  The microscope main body 100 includes an XY stage 2 on which the specimen 1 is placed and the specimen 1 can be moved in the XY direction, a revolver 4 that inserts and removes the plurality of objective lenses 3 into the observation optical path, and an observation illumination optical system 5 that illuminates the specimen 1. The observation optical system 6 that forms a sample image, and the camera 7 that picks up the sample image. A driving device 8 is provided for moving the objective lens 3 up and down along the optical axis in order to focus the specimen 1. The observation optical system 6 is provided with a dichroic mirror 10 for dividing an optical path to the focus detection optical system 9 and is configured to be able to perform a focusing operation by the AF apparatus 200.

  The revolver 4 is rotated by a driving means (not shown) and has a built-in detection means 4a for detecting position information of the objective lens 3 inserted in the observation optical path.

  The specimen 1 is placed on the XY stage 2, a drive signal is sent from an unillustrated input device to the revolver 4 via the control unit 11, and the objective lens 3 having a desired magnification is inserted into the optical path by being rotated by the drive means. The The control unit 11 is provided with a storage device (not shown) that stores information such as the attachment position of the objective lens 3 of the revolver 4 and the magnification and chromatic aberration of the objective lens 3. The control unit 11 selects a desired objective lens 3 based on information from the input device, and inserts the selected objective lens 3 into the optical path by the revolver 4. The revolver 4 detects the position of the revolver 4 of the inserted objective lens 3 by the detection means 4a and transmits it to the control unit 11. The control unit 11 determines whether or not the correctly selected objective lens 3 has been inserted into the optical path. judge.

  The focus detection optical system 9 is formed by a first projection optical system 20 that emits a pattern formed by a single slit, a second projection optical system 30 that emits a pattern formed by a plurality of slits, and both slits. And an image sensor 40 that detects the in-focus state by forming an image of the formed pattern.

  The light that projects the pattern formed by the single slit emitted from the first projection optical system 20 is made to be substantially parallel light by the lens 21, and almost half of the optical path is shielded by the knife edge 22, and the half mirror 23. Then, the light passes through the half mirror 24 and enters the dichroic mirror 10 provided in the microscope main body 100. The light is reflected in the direction of the objective lens 3 by the dichroic mirror 10 and projected onto the sample 1 through the objective lens 3. The reflected light of the light that projects the pattern formed by the single slit projected onto the sample 1 is collected by the objective lens 3, reflected by the dichroic mirror 10 toward the focus detection optical system 9, and then reflected by the half mirror 24. The light is reflected in the direction of the imaging optical system 41, is deflected by approximately 90 degrees by the mirror 42 in the imaging optical system 41, and is imaged by an image sensor 40 (to be described later) with a chromatic aberration correction lens 43 and an imaging lens (not shown). The detection signal from the image sensor 40 is analyzed by the control unit 11, the focus state is detected, and the driving means 8 of the microscope main body 100 is driven to move the objective lens 3 up and down in order to focus the objective lens 3 on the sample 1. . The first projection optical system, the imaging optical system 41, and the control unit 11 constitute a slit AF device.

  The light that projects the pattern formed by the plurality of slits emitted from the second projection optical system 30 is made almost parallel light by the lens 31, deflected by about 90 degrees by the mirror 32, and made incident on the half mirror 23. , Reflected in the direction of the dichroic mirror 10. The optical path after the half mirror 23 is the same as the optical path for projecting a pattern formed by a single slit, passes through the half mirror 24, enters the dichroic mirror 10, is reflected, and is reflected through the objective lens 3. Is irradiated. The reflected light of the light that projects the pattern formed by the plurality of slits projected onto the specimen 1 is collected by the objective lens 3, reflected by the dichroic mirror 10 in the direction of the focus detection optical system 9, and connected by the half mirror 24. The light is reflected in the direction of the image optical system 41, deflected by approximately 90 degrees by the mirror 42 in the image forming optical system 41, and picked up by an image pickup device 40 (to be described later) with a chromatic aberration correction lens 43 and an image forming lens (not shown). The detection signal from the image sensor 40 is analyzed by the control unit 11, the focus state is detected, and the driving means 8 of the microscope main body 100 is driven to move the objective lens 3 up and down in order to focus the objective lens 3 on the sample 1. . The second projection optical system, the imaging optical system 41, and the control unit 11 constitute a contrast AF device.

  The observation illumination optical system 5 of the microscope main body 100 converts the light from the light source 51 into a substantially parallel light by the lens 52, reflects it in the direction of the objective lens 3 by the half mirror 53, and collects the light on the sample 1 through the objective lens 3. To do. The reflected light from the specimen 1 is collected by the objective lens 3, passes through the half mirror 53 and the dichroic mirror 10, forms an image on the camera 7 by the imaging lens 61, and is observed by the user on a monitor (not shown). The

  The image sensor 40 is composed of three parts as shown in FIG. The central portion 40 a is a surface conjugate with the focal plane of the objective lens 3 and is the focal position of the imaging optical system 41. The left portion (left side in FIG. 2) 40b is configured such that the image sensor 40 is positioned at a position where the optical path length is short in the imaging optical system 41, and detects a so-called front focus image. The right portion (right side in FIG. 2) 40c is configured such that the imaging element 40 is positioned at a position where the optical path length is long in the imaging optical system 41, and detects a so-called rear focus image. These optical path length changes are formed by a three-divided prism 44. The light of the previous focus image is reflected at the boundary surface A between the prism 44a on the chromatic aberration correction lens 43 side of the three-part prism 44 and the prism 44b disposed in the vicinity thereof, and the boundary surface B between the prism 44b and the prism 44c disposed in the vicinity thereof. The light at the focal position is incident on the image sensor 40 at the end face C of the prism 44c.

A light source having a wavelength different from that of the light source 51 of the observation illumination optical system 5 is used as the light source 25 of the first projection optical system 20 of the focus detection optical system 9 and the light source 33 of the second projection optical system 30. For example, an infrared light source such as an LED is used for the light source 25 and the light source 33, and a visible light source such as a lamp is used for the light source 51 of the observation illumination optical system 5. If the wavelengths of the light sources are different in this way, the focal position of the camera 7 of the observation optical system 6 conjugate with the focal plane of the objective lens 3 and the focus of the image sensor 40 of the imaging optical system 41 due to the chromatic aberration characteristics of the objective lens 3. Deviation occurs in position. In the AF apparatus 200 according to the present embodiment, a chromatic aberration correction lens 43 that corrects defocus due to chromatic aberration of the objective lens 3 is disposed in the optical path of the imaging optical system 41. By moving the chromatic aberration correction lens 43 arranged in the optical path of the imaging optical system 41 along the optical axis in accordance with the amount of chromatic aberration of the objective lens 3 inserted in the optical path of the observation optical system 6, the objective lens It is possible to correct the defocus due to the chromatic aberration of No. 3.

  Next, a control flow in the AF apparatus of the embodiment will be described with reference to FIG.

The specimen 1 to be observed is placed on the XY stage 2 and an AF operation is started from the input device (not shown) via the control unit 11.
Step S1: Specifying the type of the objective lens 3 inserted in the optical path An instruction for selecting the desired objective lens 3 is input from an input device (not shown), and the revolver 4 is rotationally driven via the control unit 11. The selected objective lens 3 is inserted into the optical path. The control unit 11 stores in advance information on the objective lens 3 mounted corresponding to each address, which is position information of the revolver 4 holding the objective lens, in a storage unit (not shown). The matching objective lens 3 is selected by the control unit 11.
Step S2: Acquisition of chromatic aberration amount information of the objective lens 3 The storage unit of the control unit 11 stores the magnification, working distance, chromatic aberration amount, and the like corresponding to the type of the objective lens 3, so the address of the revolver 4 is detected. Thus, information such as the amount of chromatic aberration of the objective lens 3 inserted in the optical path can be acquired.
Step S3: Chromatic aberration correction lens drive The chromatic aberration correction lens 43 is moved along the optical axis of the imaging optical system 41 in accordance with the amount of chromatic aberration, and the single slit pattern from the first projection optical system 20 and the image sensor 40. To a conjugate relationship.
Step S4: AF operation starts. Step S5: The light source 25 of the first projection optical system 20 is turned on.
When the driving is finished, the light source 25 of the first projection optical system 20 is turned on, and the AF operation by the light for projecting the pattern formed by the single slit of the first projection optical system 20 is started.
Step S6: Driving the relative position of the specimen 1 and the objective lens 3 Since the first projection optical system 20 is a so-called slit AF, the relative distance between the specimen 1 and the objective lens 3 is the in-focus position when the light source 25 is turned on. Since the control unit 11 can determine whether it is farther or closer by a signal from the image sensor 40, the control unit 11 changes the relative distance between the objective lens 3 and the sample 1 in a direction approaching the in-focus position. The driving of the driving means 8 of the microscope main body 100 is started. In the slit AF device, the signal in the image sensor 40 is detected using only the central portion 40 a of the three-divided prisms 44 of the imaging optical system 41.
Steps S5 to S9: ON / OFF of the light source 25 of the first projection optical system 20 and the light source 33 of the second projection optical system 30, AF operation After the driving of the driving means 8 is started, the imaging device 40 (for example, CCD) In synchronization with the refresh rate or the like, the light source 25 of the first projection optical system 20 and the light source 33 of the second projection optical system 30 are alternately turned ON / OFF, and the operation is performed until a contrast signal from the second projection optical system 30 appears. While iteratively, it is driven to change the relative distance between the objective lens 3 and the sample 1 in the direction approaching the in-focus position. The control unit 11 alternately performs a slit AF operation and a contrast AF operation. Note that the conjugate relationship between the second projection optical system 30 and the image sensor 40 is the same as that of the first projection optical system 20, so that the chromatic aberration correction of the second projection optical system 30 is the chromatic aberration of the first projection optical system 20. It has been eliminated by correction.
Step S8: Contrast signal detection When a contrast signal appears in the signal from the image sensor 40, the light source 33 of the first projection optical system 20 and the light source 33 of the second projection optical system 30 are stopped alternately and the light source 33 is turned on. Then, the contrast AF operation by the second projection optical system 30 is executed.
Steps S10 to S12:
In the contrast AF operation, the control unit 11 uses the front focus portion 44b and the rear focus portion 44c of the three-divided prisms 44 of the imaging optical system 41, calculates the difference between the contrast signals of the two, and obtains the SU curve. The relative position between 1 and the objective lens 3 is detected while driving the driving means 8, and the time when the difference becomes zero is determined as the in-focus position.
Step S13: Completion of Focus The control unit 11 completes the focus detection operation when the difference between the contrast signals becomes zero, and thereafter shifts to a mode for controlling to maintain the focus at the focus position. This can be achieved by continuously executing steps S10 to S12. If the contrast signal falls below a preset threshold while the XY stage 2 is driven and the inspection is performed while changing the position of the specimen 1, the control unit 11 starts the focus detection operation again from step S5. By doing this, the contrast AF operation is prevented from becoming unstable, and high-precision focusing is maintained.

  In this manner, the AF apparatus 200 in the embodiment can focus the specimen 1 on the objective lens 3 and maintain it.

  Note that even if there is a step in the sample 1 and the contrast AF device is determined to be in focus, it may be different from the place to be observed. It is preferable that the in-focus position can be finely adjusted by adding an electrical offset.

  In the above embodiment, the first focusing optical system and the second projecting optical system are alternately switched to perform the focusing operation on the sample, and finally, the high-precision focusing operation is performed by contrast AF. However, from the initial focus pull-in operation to focusing, the first projection optical system performs the focusing operation, and the second projection is performed in order to perform focusing with higher accuracy from the position focused by the first projection optical system. It may be configured to perform the focusing operation by switching to the optical system.

  Moreover, although the image pick-up element is comprised from three parts, it is also possible to use not only a three part but a well-known detection method using a 2 division detector. At this time, it is not necessary to arrange the three-divided prism.

  As described above, according to the microscope including the AF device according to the embodiment, it is possible to easily perform the focus pull-in with a wide focus pull-in range by the slit AF, and to focus with high accuracy by the contrast AF. And a microscope having the same can be achieved.

  The above-described embodiment is merely an example, and is not limited to the above-described configuration and shape, and can be appropriately modified and changed within the scope of the present invention.

It is a schematic block diagram of the microscope containing AF apparatus which concerns on one embodiment of this invention. It is explanatory drawing of the imaging device mounted in the microscope of FIG. The control flow of an AF apparatus is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Specimen 2 XY stage 3 Objective lens 4 Revolver 5 Observation illumination optical system 6 Observation optical system 7 Camera 8 Driving means 9 Focus detection optical system 10 Dichroic mirror 11 Control unit 20 First projection optical system 21 Lens 22 Knife edge 23, 24 Half Mirror 25 Light source 30 Second projection optical system 31 Lens 32 Mirror 33 Light source 40 Imaging element 41 Imaging optical system 42 Mirror 43 Chromatic aberration correction lens 44 Tripartite prism 51 Light source 52 Lens 53 Half mirror 61 Imaging lens 100 Microscope main body 200 AF device

Claims (5)

A first projection optical system for projecting a single one slit Topa turn specimen via the objective lens,
A second projection optical system for projecting a slit Topa turn multiple to the specimen through the objective lens,
An imaging optical system that forms an image of the single slit pattern and an image of the plurality of slit patterns on an image sensor through the objective lens ;
The first projection optical system includes a first light source, the second projection optical system includes a second light source, and includes a controller that controls the first light source and the second light source,
The control unit shifts from the focus detection by the image sensor of the single slit pattern image to the focus detection by the image sensor of the plurality of slit pattern images by using the first light source and the second light source. While alternately switching, focus detection by the image sensor of the single slit pattern image and focus detection by the image sensor of the plurality of slit pattern images are alternately performed, and the relative distance between the objective lens and the sample is changed. A focus detection apparatus for a microscope characterized by being changed. The focus detection apparatus for a microscope according to claim 1, wherein the first light source and the second light source are different in wavelength from a light source for observing the specimen.   The focus detection apparatus for a microscope according to claim 1, wherein the imaging optical system includes a correction lens that corrects a defocus due to chromatic aberration of the objective lens. Storage means for storing information of the plurality of objective lenses;
A holding member for holding the plurality of the objective lens,
Detecting means for detecting the position of the objective lens inserted in the optical path of an observation optical system for observing the specimen ;
Driving means for said from the base-out before term memory means to the information from the detecting means obtains the information of the objective lens, and drives the correction lens,
The focus detection apparatus for a microscope according to claim 3, comprising: A microscope comprising the microscope focus detection device according to claim 1 .

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