JPH09325277A - Focus detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a focus detector introducing the principle of a confocal microscope. SOLUTION: Light emitted from focus detecting light sources 11, 12 and 13 are reflected by a dichroic mirror 15 arranged in an observation optical path running from an objective lens 1 to an eyepiece 2, then, the light is guided into the observation optical path and an observation sample 5 is irradiated with the light transmitted through the objective lens 1. And the light returning through the objective lens 1 after being reflected by the observation sample 5 is reflected by the dichroic mirror 15 and a half mirror 16 so as to irradiate the pin hole 17a of a photodetecting substrate 17, then, the quantity of light transmitted through the pin hole 17a is detected by a light quantity detector 18. Besides, the focus detector is provided with a focusing device 6 for shifting the sample 5 in up and down directions. The focus detecting light sources and the photodetecting substrate 17 are arranged on the common position of the image plane of the sample 5 by the objective lens 1, then, a just focused state is obtained when the light quantity detected by the light quantity detector 18 comes to the maximum by changing a distance by the focusing device 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for automatically detecting a focused position (focused position) in an optical instrument such as an optical microscope. More specifically, it uses the principle of a confocal microscope. The present invention relates to a device for detecting a focus position.

[0002]

2. Description of the Related Art Various automatic focusing devices for optical instruments such as optical microscopes and telescopes have been proposed and put into practical use. Although the conventional auto-focusing device has its own practicability, there is a demand for a more practical auto-focusing device. Due to such requirements, the present applicant sought a new autofocus device and invented a new focus detection device using the principle of a confocal microscope.

As described above, the present invention relates to an apparatus for automatically detecting the in-focus position by using the principle of a confocal microscope. Therefore, the principle of a confocal microscope will be described first with reference to FIG. In this confocal microscope, the point light source light from the laser diode 71 is applied to the half mirror 72, is reflected here, and is reflected by the objective lens 73.
A point image is formed on the sample 74 by. This light is reflected by the sample 74, passes through the objective lens 73 again, and passes through the half mirror 7
After passing through 2, the pinhole substrate 75 is irradiated. Here, the pinhole substrate 75 is the primary image plane position of the sample 74 by the objective lens 73, that is, the laser diode 7.
It is arranged at a conjugate position with the first light source position and forms a point image on the pinhole 75a formed on the substrate 75. Therefore, the light that forms a point image in this way passes through the pinhole 75a,
Immediately after that, the detector 76 hit
Is detected by

As described above, in the case of the confocal microscope,
Light source position of laser diode 71 and pinhole substrate 7
5 and 5 are arranged at the image plane position (conjugate position) of the objective lens 73, and the amount of light detected by the detector 76 changes according to the focus position of the sample 74. This light amount becomes maximum when the sample 74 is located at the just focus position (focus position), and decreases as the focus shifts.

[0005]

An object of the present invention is to obtain a focus detection device by using the principle of the confocal microscope as described above, and to provide an optical system for observing an observation sample through the objective lens having at least an objective lens. Used in equipment,
It is configured as follows.

This apparatus is arranged in the observation light path from the focus detection light source and the objective lens to the observation position, guides the light from the focus detection light source to the objective lens, and passes the objective lens for observation. The first partial reflection optical element that irradiates the sample (The partial reflection optical element is a function such as a half mirror, a dichroic mirror, and a beam splitter that transmits a part of the incident light as it is but reflects the rest. And an amount of light for detecting the amount of light from the aperture, which is the light returning from the objective lens after being reflected by the observation sample. It comprises a detection means and a focus adjustment means for changing the distance between the observation sample and the objective lens. The light source for focus detection and the opening are arranged at a position conjugate with the image plane of the observation sample by the objective lens, and based on the change in the light amount detected by the light amount detection means when the distance is changed by the focus adjustment means. The focus state of the optical device is detected.

As can be seen from the description of the principle of the confocal microscope, the focus detection light source and the aperture are arranged at a conjugate position where reflected light from the observation sample passes through the objective lens and forms an image of the observation sample. It has the same configuration as the focal microscope and maximizes the light amount detected by the light amount detection means when the observation sample is in the just focus state (focus state). Therefore, when the distance between the observation sample and the objective lens is changed by the focus adjusting means to detect the distance at which the detected light amount of the light amount detecting means is maximum, the position at which the light amount is maximum is the just focus position, and is automatically adjusted. The focus position can be detected.

The first partial reflection optical element guides the light from the focus detection light source to the observation sample through the objective lens and reflects the reflected light from the observation sample toward the focus detection light source. In the detection optical path from the focus detection light source to the first partial reflection optical element, the light reflected by the observation sample and then reflected by the first partial reflection optical element toward the focus detection light source is detected. A second partial reflection optical element for reflecting the light toward the outside of the optical path, and an observation surface in the optical path of the light reflected by the second partial reflection optical element through the opening of the light amount detection means and guided to the outside of the detection optical path. It is preferable to dispose at a position conjugate with the image plane of.

Another focus detection device according to the present invention is
The first partial reflection, which is arranged in the observation light path from the focus detection light source to the observation position from the objective lens, guides the light from the focus detection light source to the observation light path, and irradiates the observation sample through the objective lens. An optical element, a light splitting means for splitting light returning from the objective lens after being reflected by the observation sample into three first to third optical paths, and light passing through the first opening in the first optical path. First light amount detecting means for detecting the light amount of light, second light amount detecting means for detecting the light amount of light passing through the second opening in the second optical path, and passing through the third opening in the third optical path. Third light amount detecting means for detecting the amount of light to be emitted,
It is configured to include a focus adjusting unit that changes the distance between the observation sample and the objective lens. Then, the focus detection light source and the second opening are arranged at a position conjugate with the image plane of the observation sample by the objective lens, and the first opening is observed in the optical axis direction from the conjugate position of the image plane. The third opening is located closer to the specimen, and the third opening is located farther from the observation specimen than the conjugate position of the image plane. Then, when the distance is changed by the focus adjusting means, the focus position of the optical device is detected based on the light amount changes detected by the first to third light amount detecting means.

In the case of the focus detection device having this structure, the first
It is preferable to set the operating direction of the focus adjusting means based on the difference between the light quantity detected by the light quantity detecting means and the light quantity detected by the third light quantity detecting means.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described below with reference to FIG. here,
Objective lens 1, eyepiece lens 2, epi-illumination source 3 and first
An example in which the focus detection device according to the present invention is used for the optical microscope MS having the half mirror 4 is shown. Epi-illumination source 3
The light from is reflected by the first half mirror 4, passes through a dichroic mirror 15 and an objective lens 1 described later,
Illuminate the specimen 5. The light from the illuminated specimen 5 follows the opposite course, and the objective lens 1 and the dichroic mirror 15
Since the image of the sample 5 is formed on the image plane 8 through the first half mirror 4 and the first half mirror 4 in this order, it is configured to be observed through the eyepiece 2.

In this observation, focusing is performed on the specimen 5.
(Specifically, the sample mounting table) is moved up and down by the focus adjusting device 6 as shown by an arrow A to change the distance from the objective lens 1. In this apparatus, the focus position detection by the focus adjustment device 6 is automatically performed by the controller 20, and the focus detection device 10 will be described below.

This device 10 includes a lamp 11 forming a light source for focus detection, a collector lens 12 and an illumination substrate 13.
And collects the light of the lamp 11 into the pinhole 13a of the illumination substrate 13 by the collector lens 12,
The light that has passed through a is emitted as focus detection light. In addition,
The illumination substrate 13 is arranged at a position conjugate with the image plane 8 of the sample 5 by the objective lens 1 of the optical microscope MS. The focus detection light passes through the second half mirror 16 and is applied to the dichroic mirror 15 disposed in the observation optical path of the optical microscope MS, and the light reflected by the dichroic mirror 15 enters the observation optical path. An image of the pinhole 13a is formed on the sample 5 by the objective lens 1.

This light is reflected by the sample 5, passes through the objective lens 1 again, is reflected by the dichroic mirror 15, is then reflected by the second half mirror 16, and reaches the light receiving substrate 17. The light receiving substrate 17 is arranged on the image plane of the sample 5 by the objective lens 1 on the optical axis of the light reflected by the dichroic mirror 15 and the second half mirror 16 as described above (that is, the illumination substrate 13 and It is arranged at a conjugate position with the light receiving substrate 17).
Therefore, an image of the light emitted from the pinhole 13a of the illumination substrate 13 (that is, the pinhole 1
3a).

As can be seen from this configuration, the focus detection apparatus 10 shown here has the same configuration as the confocal microscope, and as can be seen from the above description, the light amount density of the light receiving substrate 17 is when the sample 5 is just in focus. It becomes the maximum and decreases as the focus shifts. That is,
The position of the sample 5 when the light amount density of the light receiving substrate 17 is maximum is the just focus position.

Therefore, in this device 10, the light receiving substrate 1
7 to form a pinhole 17a and the light receiving substrate 17
Immediately after the light amount detector 18, the light amount detector 18 measures the light amount density of the light that forms an image on the light receiving substrate and passes through the pinhole 17a. Then, the measuring device is sent to the controller 20, and the focus adjustment device 6 controls the vertical movement (arrow A) of the observation sample 5 based on the measured value.

FIG. 2 shows the relationship between the light quantity density (vertical axis) measured by the light quantity detector 18 and the vertical position (horizontal axis) of the sample 5.
Qualitatively. The light amount density becomes maximum when the sample 5 is located at the vertical position pj, and the position pj is the just focus position. Here, an example in which automatic focus detection is performed when the sample 5 is located at the position p1 in FIG. 2 will be described.

For automatic focus detection, the controller 2
At 0, first, the sample 20 is moved up or down. For example, if this is moved downward from the position p1 as indicated by the arrow m1, the light amount density decreases, so at the position p2, the controller 20 determines that the focus operation direction is opposite, and performs the reverse operation. As a result, the sample 5 is moved upward as indicated by the arrow m2, and the peak position pj can be detected at the position p3 at which it is detected that the light amount density passes through the peak position pj and is lowered. Therefore, the position returned by the excessive amount (arrow m3) is the just focus position, whereby the automatic focus detection is completed.

[0019]

Second Embodiment of the Invention Next, a second embodiment of the present invention will be described with reference to FIG. In this example as well, the focus detection device according to the present invention is used in the same optical microscope MS as in the example of FIG. That is, the light from the epi-illumination source 3 is reflected by the first half mirror 4, passes through the dichroic mirror 15 and the objective lens 1 described later, and passes through the sample 5.
The light from the illuminated sample 5 is transmitted through the objective lens 1, the dichroic mirror 15 and the first half mirror 4, and an image of the sample 5 is formed on the image plane 8, which is passed through the eyepiece 2. Observe through.

The focus detection device 30 of this example has the same focus detection light source as in the example of FIG. 1, and the light from the lamp 11 is collected by the collector lens 12 into the pinhole 13 of the illumination substrate 13.
The light that has been collected in a and has passed through the pinhole 13a is emitted as focus detection light. The illumination substrate 13 is arranged at a position conjugate with the image plane 8 of the optical microscope MS. The focus detection light passes through the second half mirror 16 and is applied to the dichroic mirror 15, and the light reflected by the dichroic mirror 15 enters the observation optical path and forms an image of the pinhole 13 a on the sample 5 by the objective lens 1. .

This light is reflected by the sample 5, passes through the objective lens 1 again, is reflected by the dichroic mirror 15, is then reflected by the second half mirror 16, and is irradiated upward in the drawing. A light splitting device 31 including third and fourth half mirrors 32 and 33 is disposed here, and the light reflected by the second half mirror 16 is divided by the light splitting device 31 into three parts as shown in the figure. Will be divided. Specifically, first, the light reflected by the third half mirror 32 is applied to the pinhole 41a of the first light receiving substrate 41, and the light that has passed through the third half mirror 32 and the fourth half mirror 33 is the first light. 2 Pinhole 4 of light receiving substrate 43
The light radiated to 3a and reflected by the fourth half mirror 33 is radiated to the pinhole 45a of the third light receiving substrate 45.

Here, the second light receiving substrate 43 is arranged on the optical axis on the image plane of the sample 5 by the objective lens 1, that is, at the position c2 which is conjugate with the illumination substrate 13,
The light receiving substrate 41 is arranged at a position on the front side by a distance L from the conjugate image plane position c1 (a position separated by a distance −L).
The third light receiving substrate 45 is arranged at a position rearward of the conjugate image plane position c3 by a distance L (a position separated by a distance + L). Then, these first to third light receiving substrates 41, 43, 4
Immediately after 5, the pinholes 41a, 43a, 45 of each board are
First to third light amount detectors 4 for detecting the amount of light passing through a
2, 44, 46 are arranged.

In this device 30, each light quantity detector 4
Based on the detected values of 2, 44 and 46, the controller 35 controls the vertical movement of the sample 5 by the focus adjusting device 6 to detect the focus position. Also in this apparatus, basically, the position where the light amount density passing through the pinhole 43a of the second light receiving substrate 43 located at the conjugate image plane position c2 of the sample 5 by the objective lens 5 is the maximum is the just focus position. The automatic focus position detection can be performed in the same manner as the device of FIG.

However, in this device, automatic focus detection can be performed more simply and quickly by using the detection values of the first and third light amount detectors 42 and 46. As described above, the first and third light receiving substrates 41, 45
Are separated from the conjugate image plane positions c1 and c3 by distances -L and + L, respectively, and therefore, the relationship between the sample position and the detection values R1, R2, and R3 of the first to third light amount detectors 42, 44, and 46. Becomes as shown in FIG. In this figure, the peak values of the detection values R1, R2, R3 are the same, but the third and fourth half mirrors that configure the light splitting device 31 so that the same peak value is obtained in this way. 32,
Set 33 performances. However, since it is difficult to manufacture a half mirror having such a setting, it is preferable to adjust the detection gain of each detection value and perform gain correction so that the peak values are the same.

FIG. 4 also shows the difference (R1−R3) between the detection values R1 and R3 of the first and third light amount detectors 42 and 46. This difference is determined by the sample 5 as shown in the figure. As long as it is in the range (range between PL and PH), it is represented by a monotonically decreasing curve and becomes zero at the just focus position pj. Therefore, looking at the value of this difference (R1-R3),
The moving direction of the sample 5 necessary to obtain just focus can be known. Therefore, the controller 35 causes the difference (R1-
The focus adjustment device 6 is operated so as to move the sample 5 in the direction of making R3) zero, so that automatic focus detection can be performed easily and quickly.

The first and third light receiving substrates 41, 45
The diameter D of the pinholes 41a and 45a formed in L is: L> = D / (2NA) where L is the distance from the position of the substrates 41 and 45 to the image planes c1 and c3 NA: Light receiving substrate (light amount detector) It is preferable to set it so that the numerical aperture at the position is satisfied.

If this condition is not satisfied, the pinhole 4
The diameter D of 1a and 45a becomes larger than the light beam diameter, and the detector detects the light amount of the entire light beam in the vicinity of just focus, so that the detection value of the light amount detector does not change even if the sample 5 is moved. Therefore, if a large pinhole diameter that deviates from the above conditions is set, the value of the light amount difference (R1-R3) is always zero in the vicinity of the just focus position, and it becomes difficult to set the focusing direction in this portion. However, by setting a diameter that satisfies the above condition, good focus adjustment can always be achieved.

In the above embodiments (No. 1 and No. 2), a laser diode may be arranged at the position of the illumination substrate 13 instead of the focus detection light source including the light source 11, the collector lens 12 and the illumination substrate 13. . Further, the pinholes 41a, 43a, 45a of the first to third light receiving substrates 41, 43, 45 may be replaced with minute slits. In this case, it is preferable to use the slit width instead of the pinhole diameter D in the conditional expression to set the slit width that satisfies the conditional expression.

[0029]

As described above, according to the present invention,
The focus detection light source and the aperture have the same configuration as the confocal microscope because the reflected light from the observation sample passes through the objective lens and is arranged at the conjugate position where the image of the observation sample is formed. The amount of light detected by the light amount detecting means during focusing (that is, the amount of light passing through the opening) is maximized. Therefore, when the distance between the observation sample and the objective lens is changed by the focus adjusting means to detect the distance at which the detected light amount of the light amount detecting means is maximum, the position at which the light amount is maximum is the just focus position, and is automatically adjusted. The focus position can be detected.

Another focus detection device according to the present invention is
First to third light amount detecting means for respectively detecting the light amounts of the light beams divided into three by the light dividing means and passing through the first to third opening portions, and focus adjusting means for changing the distance between the observation sample and the objective lens. A light source for focus detection and a second
Is arranged at the conjugate position of the image plane of the observation sample by the objective lens, the first aperture is arranged at a position closer to the observation sample than the conjugate position of the image plane on the optical axis, and the third aperture is formed. The part is arranged on the optical axis farther from the conjugate position of the image plane to the observation sample, and when the distance is changed by the focus adjusting means,
The focus position of the optical device is detected based on the change in the light amount detected by the first to third light amount detecting means. Therefore, the just focus position can be detected by detecting the position where the detected light amount of the second light amount detecting means is maximum. However, in the case of the focus detecting device having this configuration, the just focus position can be detected as the light amount detected by the first light amount detecting means. The operating direction of the focus adjusting means can be set based on the difference from the light quantity detected by the third light quantity detecting means, and simpler and faster automatic focus detection is possible.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an optical microscope having a focus detection device according to a first embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a light amount density and a sample position by a light amount detector of this focus detection device.

FIG. 3 is a schematic configuration diagram of an optical microscope having a focus detection device according to a second embodiment of the present invention.

FIG. 4 is a graph showing the relationship between the light amount density by the light amount detector of this focus detection device and the sample position, and the relationship between the difference between the detection values of the first and third light amount detectors and the sample position.

FIG. 5 is a schematic diagram showing a principle configuration of a confocal microscope.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Objective lens 2 Eyepiece 5 Sample 6 Focus adjustment device 13 Illumination substrate 15 Dichroic mirror 17 Light receiving substrate 18 Light quantity detector 20, 35 Controller 31 Light splitting device 41, 43, 45 First to third light receiving substrate 42, 44, 46 First to third light intensity detectors

Claims (10)

[Claims] 1. A focus detection device provided in an optical device for observing an observation sample through an objective lens to detect a focus state of the observation sample, wherein focus detection is a point light source substantially in one predetermined direction. For illuminating the observation sample through the objective lens, which is disposed in the observation optical path from the objective lens to the observation position and guides the light from the focus detection light source to the objective lens. A one-part reflection optical element, and an opening which is a minute opening in one direction corresponding to the predetermined one direction for the light from the light source for focus detection that returns through the objective lens after being reflected by the observation sample. The focus detection light source includes a light amount detection unit that receives light through the opening and detects a light amount of the light from the opening, and a focus adjustment unit that changes a distance between the observation sample and the objective lens. The opening is arranged at a position conjugate with the image plane of the observation sample by the objective lens, and is based on the light amount change detected by the light amount detecting unit when the distance is changed by the focus adjusting unit. A focus detection device, which detects a focus state of the optical device. 2. The first partially reflective optical element transmits the light from the focus detection light source to the observation sample through the objective lens, and reflects the reflected light from the observation sample to the focus detection light source. The light source for focus detection by the first partial reflection optical element after being reflected by the observation sample in the detection optical path from the focus detection light source to the first partial reflection optical element. A second partial reflection optical element that reflects the light reflected toward the outside of the detection optical path, and the opening of the light amount detection means is reflected by the second partial reflection optical element. The focus detection device according to claim 1, wherein the focus detection device is arranged at a position conjugate with an image plane of the observation sample in an optical path of light guided to the outside of the detection optical path. 3. The focus detection device according to claim 2, wherein the first partial reflection optical element is a dichroic mirror, and the second partial reflection optical element is a half mirror. 4. The focus detection light source is a line light source having a shape in which the point light source is extended along a direction orthogonal to the predetermined one direction, and the opening of the light amount detection means is the predetermined light source. The focus detection device according to claim 1, wherein the focus detection device has a slit shape extending along one direction corresponding to a direction orthogonal to the one direction. 5. A focus detection device provided in an optical device for observing an observation sample through an objective lens to detect a focus state of the observation sample, wherein focus detection is a point light source substantially in one predetermined direction. For illuminating the observation sample through the objective lens, which is disposed in the observation optical path from the objective lens to the observation position and guides the light from the focus detection light source to the objective lens. A partially reflective optical element; a light splitting means for splitting light from the focus detection light source, which is reflected by the observation sample and then returns through the objective lens, into first to third optical paths; First light quantity detecting means arranged to receive the light from the light splitting means through the first opening and detect the light quantity of the light from the first opening; and arranged in the second optical path. Is the light splitting means Light from the light splitting means disposed in the third optical path, the second light quantity detecting means for receiving the light of the light through the second opening and detecting the light quantity of the light from the second opening. And a focus adjusting means for changing the distance between the observation sample and the objective lens, the third light amount detecting means for receiving the light through the third opening portion, and detecting the light quantity of the light from the third opening portion. The first to third openings are minute openings in one direction corresponding to the one predetermined direction, and the focus detection light source and the second opening are formed by the objective lens. The first opening is arranged at a position conjugate with the image plane of the observation sample, the first opening is arranged at a position closer to the image axis of the observation sample in the optical axis direction, and the third opening is provided. Is disposed at a position farther in the optical axis direction than the conjugate position of the image plane of the observation specimen. Focus detection of the in-focus state of the optical device is performed based on the light amount changes detected by the first to third light amount detection units when the distance is changed by the focus adjustment unit. apparatus. 6. The operating direction of the focus adjusting means is set based on the difference between the light quantity detected by the first light quantity detecting means and the light quantity detected by the third light quantity detecting means. Item 5. The focus detection device according to item 5. 7. The first partial reflection optical element guides light from the focus detection light source to the observation sample through the objective lens, and reflects light from the observation sample to the focus detection light source. The light source for focus detection by the first partial reflection optical element after being reflected by the observation sample in the detection optical path from the focus detection light source to the first partial reflection optical element. A second partial reflection optical element for reflecting the light reflected toward the outside of the detection optical path, and the light splitting means is provided outside the detection optical path by the second partial reflection optical element. The focus detection device according to claim 5 or 6, wherein the focus detection device is configured to split the light reflected to the first to third optical paths. 8. The focus detection device according to claim 5, wherein the first partial reflection optical element is a dichroic mirror and the second partial reflection optical element is a half mirror. 9. The focus detection light source is a line light source having a shape in which the point light source is extended along a direction orthogonal to the predetermined one direction, and the opening of the first to third light amount detecting means. 9. The focus detecting device according to claim 5, wherein the portion has a slit shape extending along one direction corresponding to a direction orthogonal to the predetermined one direction. 10. The optical device is an optical microscope further having an eyepiece for observing an image of the observation specimen by an objective lens, and the first partially reflective optical element is provided from the objective lens to the eyepiece lens. The focus detection device according to any one of claims 1 to 9, wherein the focus detection device is arranged in an observation optical path up to.