JPH089697Y2 - Microscope autofocus equipment - Google Patents

Description

[Detailed description of the device] [Industrial applications]

 This invention relates to an autofocus device for a microscope.

[Prior art]

Conventionally, as shown in FIG. 3, a light beam 2 from a light source 1 such as a laser diode passes through a beam splitter 3 and an objective lens 4 and is substantially orthogonal to a surface 5A to be measured of an object 5 to be measured. The reflected light which is projected in the direction and scattered and reflected by the surface 5A to be measured is reflected again at a right angle by the reflecting surface 3A of the beam splitter 3 through the objective lens 4 and the beam splitter 3 again. There is an autofocus device in which the light is incident on the light receiving element 8 via. The light receiving element 8 is an inner element including a photodiode or the like.
8A and the outer element 8B adjacent to the outside thereof,
The outputs of the inner element 8A and the outer element 8B are input to a detector (not shown) via the comparator 9. Here, the outputs of the inner element 8A and the outer element 8B increase / decrease correspondingly when the distance of the measured surface 5A from the light source 1 changes, and based on the difference between the two outputs, The distance of the surface 5A to be measured from the light source 1, that is, the displacement of the surface can be measured. In other words, when there is a boundary line between the inner element 8A and the outer element 8B at the focus position of the reflected light focused by the Foucault prism 6, the difference between the outputs of these elements becomes zero and the focus can be detected.

[Problems to be solved by the device]

By the way, a microscope generally includes a plurality of objective lenses having different magnifications, and an objective lens having an optimum magnification can be selected by rotationally driving a revolver. Here, the problem that an accurate focusing operation cannot be performed if autofocus is performed with an objective lens for normal visible light, in which the aberration of the wavelength of the output light of the laser diode that is the light source has not been corrected There was a point. Therefore, conventionally, when a laser beam is used as a light source, the objective lens that can perform the autofocus is limited, and when it is unavoidable, the objective lens is adjusted so that the aberration correction wavelength includes the wavelength of the output light of the laser diode. I had to design and produce a new lens. If only one type of objective lens is used, the position of the light receiving element may be shifted when a laser diode is used as a light source as compared with the case of normal light. Generally, a plurality of different types are used, and there is a problem that it cannot be dealt with by shifting the position of the light receiving element. This invention has been made in view of the above-mentioned conventional problems, in which autofocus is performed without shifting the position of the light receiving element and corresponding to a plurality of types of objective lenses having different aberrations, An object of the present invention is to provide an autofocus device for a microscope capable of performing an accurate focusing operation.

[Means for Solving the Problems]

This invention is directed to a light source that emits a light beam; a plurality of objectives that are arranged so as to face a surface of the object to be measured and that can be selectively arranged on an optical path of the light beam that is substantially orthogonal to the surface to be measured. A lens; disposed on the opposite side of the object to be measured with respect to the objective lens on the optical path of the light beam, the light beam traveling straight through the optical path to the surface to be measured, and reflected by the surface to be measured. And a polygonal pyramid-shaped Foucault prism that collects the reflected light that has passed through the objective lens at a plurality of positions; A plurality of light receiving elements which are different for each side corresponding to the positions of a plurality of light spots on which reflected light is condensed through the plurality of different objective lenses; For changing the light spot position of reflected light A detector for detecting the in-focus point by a change in the output signal; and a light-receiving element corresponding to the selected one objective lens, which is interlocked with the means for selecting the plurality of objective lenses, from the plurality of light-receiving elements The mode selecting device for sending the output signal of the light receiving element to the detector, and the autofocus device of the microscope are constituted by the mode selecting device;

[Action]

In this invention, a light receiving element is arranged along each side of a polygonal pyramid Foucault prism, corresponding to a plurality of types of objective lenses, at the position of an optical spot focused by each objective lens. Moreover, since the focus position is detected based on the output signal from the light receiving element corresponding to the selected objective lens, without moving the light receiving element or designing a new objective lens, Autofocus can be performed easily.

【Example】

Embodiments of the present invention will be described below with reference to the drawings. This embodiment, as shown in FIGS. 1 and 2,
A light source 12 consisting of a laser diode emitting a light beam 10.
Four objective lenses 16A, which are arranged to face the surface 14 to be measured of the object 14 to be measured and can be selectively arranged on the optical axis 11 of the light beam 10 substantially orthogonal to the surface 14A to be measured. 16D;
It is arranged on the opposite side of the object to be measured 14 with respect to the objective lens 16A, 16B, 16C or 16D on the optical axis 11 of the light beam 10, and the light beam 10 passes through the optical path to the surface to be measured 14A. A quadrangular pyramid-shaped Foucault prism 18 that collects the reflected light that has traveled straight and is reflected by the measured surface 14A and that has passed through the objective lens 16A, 16B, 16C or 16D at four locations.
The Foucault prism 18 is arranged at a position facing each side of the quadrangular surface, and the position is the objective lens 16A.
.About.16D, corresponding to the positions of the four light spots on which the reflected light is focused, four light receiving elements 21 to 24 which are different for each side; and these light receiving elements 21 to 24. A detector 26 for detecting the in-focus point by the change of the output signal based on the change of the light spot position of the reflected light; and the four objective lenses
The light receiving element 21, 22, 23, or 24 corresponding to the selected objective lens 16A, 16B, 16C, or 16D is selected in association with the revolver 27 that is a means for selecting 16A to 16D, and the selected light receiving is selected. A mode selecting device 28 for sending the output signal of the element to the detector 22 is included to constitute an autofocus device of the microscope. The light source 12 emits its light beam with respect to the optical axis 11.
They are arranged on the side of the optical axis 11 so that the optical axes of 10 are orthogonal to each other. At the intersection between the light beam 10 emitted from the light source 12 and the optical axis 11, a half mirror 30 is provided at the position between the objective lens 16 (general term of 16A to 16D) and the Foucault prism 18. It is arranged so as to form an angle of 45 ° with respect to each of the emission optical axes of the light beam 11 from the light source 11 and the light source 12. A focusing lens 32 is arranged on the optical axis 11 between the half mirror 30 and the Foucault prism 18. Further, between the half mirror 30 and the light source 12, a light source
Emission of light beam 10 from 12 Collimator lens 34 on the optical axis
Are arranged. The collimator lens 34 makes the light beam 10 emitted from the light source 12 incident on the half mirror 30 as a parallel light beam orthogonal to the optical axis 11. Further, the objective lens 16 collects the light beam 10 which is a parallel light beam reflected along the optical axis 11 at a right angle by the half mirror 30 on the surface 14A to be measured, and parallelizes the light beam reflected from the surface 14A to be measured. The light beam is made to reach the focusing lens 32 through the half mirror 30. The focusing lens 32 focuses the reflected light, which is a parallel light beam along the optical axis 11, and focuses it on the light receiving elements 21 to 24 via the Foucault prism 18. The light receiving elements 21 to 24 are each composed of a combination of outer elements 21A to 24A and inner elements 21B to 24B. These are the four objective lenses 16 whose laser light has different magnifications.
At the four focusing positions of the reflected rays that are condensed by A to 16D and pass through the Foucault prism 18, the boundary line between the inner element and the outer element is parallel to each side of the square end face of the Foucault prism 18. It is arranged to be. Further, the sensitivities of these light receiving elements 21 to 24 are such that the output of the outer element and the output of the inner element become equal when the reflected light is focused on the boundary line between the inner element and the outer element. The detector 26 is the outer element 21 of the light receiving elements 21 to 24.
A buffer amplifier 36 for amplifying any output A ₁ , A ₂ , A ₃ or A ₄ of A to 24A and any corresponding inner element 21B to 2
Buffer amplifier 38 that amplifies 4B output B ₁ , B ₂ , B ₃ or B ₄
And the difference between the output Ai of the outer element and the output Bi of the inner element (Ai-B
a subtractor 40 for calculating i) via a buffer amplifier 36,
An adder 42 for calculating the sum (Ai + Bi) of the outputs via the buffer amplifier 38, and a divider 44 for calculating the quotient using the output signals of the subtractor 40 and the adder 42 as the numerator and denominator, respectively. Has been done. Reference numeral 46 in FIG. 2 indicates a focus display means for displaying the output from the divider 44. The mode selection device 28 includes switching switches 51A to 54A arranged on the signal line from the outer elements 21A to 24A to the buffer amplifier 36, and switching switches 51A to 54A arranged on the signal line from the inner elements 21B to 24B to the buffer amplifier 38. 51B ~ 5
4B and these switching switches 51A to 54A and 51B to 54B,
51A and 51B on, other off first mode, 52A, 52B
Select a second mode that turns on and turns off the other, a third mode that turns on 53A and 53B and turns off the other, and a fourth mode that turns on 54A and 54B and turns off the other. Therefore, it is composed of a mode selector 52 for controlling these switching switches 51A to 54A and 51B to 54B. The mode selector 52 rotationally drives the objective lenses 16A to 16D, receives a signal of the selected objective lens from a revolver 27 for selecting one of the objective lenses 16A to 16D, and receives the objective lens.
The first mode, the second mode, the third mode or the fourth mode is selected corresponding to 16A, 16B, 16C or 16D. Next, the operation of the apparatus of the above embodiment will be described. The light beam 10 is emitted from the light source 12, is reflected by the half mirror 30 along the optical axis 11, and is irradiated onto the measured surface 14A of the measured object 14 via the objective lens 16. The reflected light from the surface 14A to be measured passes through the objective lens 16 again, and then the half mirror 30, the focusing lens 32, and the Foucault prism.
After passing through 18, the light receiving elements 21 to 24 are focused. The output signal (Ai-Bi) of the subtractor 40 becomes zero at the in-focus position. Therefore, the objective lens 16 is moved along the optical axis 11, and the difference Ai between the output of any of the outer elements 21A to 24A of the light receiving elements 21 to 24 and the output of any of the corresponding inner elements 21B to 24B.
If −Bi = 0, then ΔS = 0 and the in-focus point can be detected. That is, the output signal of the subtractor 40 in the detector 26 may be zero. Here, in the divider 44, the output signal ΔS of the subtractor 40 is divided by the output signal of the adder 42 because ΔS is divided by the total amount of light received by each of the light receiving elements 21-24. This is because it is possible to reduce the influence of the difference in the reflectance of the surface to be measured 14A and obtain stable resolution. When the light source 12 is a laser diode, its emitted light is coherent light, so if the objective lens is not subjected to aberration correction of the wavelength of the laser light, the focal point will deviate from the normal light. . In this embodiment, for example, if the objective lens 16B does not require aberration correction for laser light, the other three objective lenses 16A, 16C and 16D need aberration correction. For this, as shown in FIG. 2, as described above, the light receiving elements 21, 23, and 24 may be arranged at the focus positions of the laser light, offset from the normal light. Therefore, in the case of normal light, the second mode is selected by the mode selector 52, and in the case of using laser light, the first to fourth modes are selected corresponding to the objective lenses 16A to 16D. To do so. In the above embodiment, the Foucault prism 18 having a quadrangular pyramid shape is used.
However, the present invention is not limited to this, and any polygonal pyramidal Foucault prism may be used depending on the number of objective lenses. Therefore, for example, the shape may be a triangular pyramid shape or a pentagonal pyramid shape. Further, in the above embodiment, the light beam 10 from the light source 12 is irradiated onto the surface to be measured 14A via the objective lens 16 as an irradiation light beam having a relatively wide surface. The laser beam from the light source 12 may be oscillated by a tuning fork or the like in the vertical direction in FIG. By doing so, the influence of the surface shape of the surface to be measured 14A can be reduced.

[Effect of device]

Since the present invention is configured as described above, without using an aberration-corrected objective lens for laser light or the like,
There is an excellent effect that the focusing operation can be surely performed according to the wavelength of the light source light without moving the light receiving element.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of an autofocus device for a microscope according to the present invention, FIG. 2 is a plan view including a partial circuit diagram showing a Foucault prism, a light receiving element and a detector in the embodiment, FIG. 3 is a sectional view showing a conventional autofocus device. 10 ... Light beam, 12 ... Light source, 14 ... Object to be measured, 14A ... Surface to be measured, 16A-16D ... Objective lens, 18 ... Foucault prism,
21 to 24 ... Light receiving element, 26 ... Detector, 27 ... Revolver, 28 ...
Mode selection device.

 ─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-54-39101 (JP, A) JP-A-63-138310 (JP, A) JP-A-62-283427 (JP, A) JP-A-62- 223613 (JP, A) JP 61-270719 (JP, A) Actually developed 58-141434 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. A light source that emits a light beam; a plurality of light sources that are arranged so as to face a surface to be measured of an object to be measured and can be selectively arranged on an optical path of the light beam substantially orthogonal to the surface to be measured. An objective lens; disposed on the opposite side of the object to be measured with respect to the objective lens on the optical path of the light beam, the light beam traveling straight through the optical path to the surface to be measured, and at the surface to be measured; A polygonal-pyramidal Foucault prism that is formed by being reflected and focuses the reflected light that has passed through the objective lens at a plurality of positions; A plurality of light receiving elements whose positions are different for each side corresponding to the positions of a plurality of light spots on which reflected light is condensed through the plurality of different objective lenses; For changing the light spot position of the reflected light A detector for detecting the in-focus point by a change in the output signal; and a light-receiving element corresponding to the selected one objective lens, which is interlocked with the means for selecting the plurality of objective lenses, from the plurality of light-receiving elements And a mode selection device for sending the output signal of the light receiving element to a detector, and an autofocus device for a microscope.