JPH095018A - Device for measuring moving quantity - Google Patents

Abstract

PURPOSE: To detect the moving quantity of a lens mount on the optical axis of objective lens or the like, by providing a moving mirror means and a fixed mirror means, according to the change in the light path length difference between the reflection beams of a measurement beam and a reference beam made incident on each reflection surface. CONSTITUTION: A laser beam from a laser light source 1 is made incident on a polar beam splitter 2 and divided into a reference beam and a measurement beam. The reference beam reflected on the splitter 2 passes through a 1/4 wavelength plate 8 and reflected on a board mirror 9, then returns to pass through the plate 8 again to become the reference beam linearly polarized, passing through the splitter 2. The reference beam passes through a corner cube 6 and a 1/2 wavelength plate 7 and reflected on the splitter 2 and a reflection mirror 3. Thereafter, the reference beam passes through a 1/4 reflection plate 4 and reflected on the mirror 9, and then passes through a wavelength plate 4 and made incident on a detector 10. The measurement beam passed through the splitter 2 is reflected at a plate 3, then passes the plate 4 and made incident on the detector 10 again after being reflected on a planar mirror 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a movement length measuring device for measuring a displacement in a direction of an optical axis of an objective lens of a microscope to which a plane mirror interferometer is applied with high precision by a laser beam.

[0002]

2. Description of the Related Art Conventionally, there is a movement amount measuring device which is attached to an objective lens of a microscope or the like and measures the displacement in the optical axis direction. As a configuration generally used, as shown in FIG. 2, a glass scale 21 is fixed to a mirror body 20 of a microscope, and a read head 22 is mounted on a mount 11 of an objective lens 12 so as to be superposed on the glass scale 21. Is fixed and configured. In this configuration, the reading head 22 moves as the objective lens 12 moves, and the amount of movement is read and measured by the glass scale 21.

[0003]

However, in the above-described conventional movement length measuring device, since the respective parts are attached to the mirror body 20 and the mount 11 (objective lens 12), the optical axis of the objective lens 12 and There is no choice but to install the glass scale 21 at a remote position. That is, instead of directly measuring the amount of movement of the objective lens 12 itself, the mount 11
The amount of movement of the mount 11 is measured as the amount of movement of the objective lens 12 on the premise that the displacement of the optical axis does not occur in the movement of. However, the mount 11 is actually
It moves due to its mechanical structure, and even if it is made up of precision members, even if it is a slight amount, blurring will inevitably occur. This blur causes a blur on the optical axis of the objective lens.

Therefore, it is difficult to avoid Abbe error due to the influence of the shake of the true angle when the objective lens is moved. If a glass scale is installed directly above the objective lens, Abbe error can be eliminated, but such an arrangement is difficult because it is necessary to secure an observation path by the objective lens.

Therefore, the present invention is to provide a moving amount measuring device which is miniaturized and which highly accurately measures the moving amount of an objective lens of a microscope in the optical axis direction by utilizing the interference of laser light. To aim.

[0006]

To achieve the above object, the present invention provides a laser light source, a polarization beam splitter for splitting the laser light from the laser light source into reference light and measurement light, and a movable objective lens. The movable mirror means is fixed to a peripheral portion outside the observation path range of the lens barrel, and is arranged in parallel with the reflecting surface of the moving mirror means at a predetermined interval, and the moving mirror means for reflecting the incident measuring light at at least two points on the reflecting surface. Fixed mirror means for reflecting the incident reference light at at least two points on the reflection surface, reference light and measurement light reflected by the movable mirror means and the fixed mirror means, and the reference light and the measurement light Detecting means for detecting the amount of movement of the objective lens barrel by changing the difference in optical path length, reference light and measurement light split by the polarization beam splitter, the moving mirror means and the fixed mirror hand. Respectively guided to a predetermined reflection point of
Provided is a movement length measuring device including a reference light reflected at each reflection point and an optical path means for guiding the measurement light to the detecting means.

[0007]

The movement length measuring device having the above-described structure includes the moving mirror means attached to the peripheral portion of the objective lens barrel (lens mount) outside the observation path range of the microscope and the lens mount in the microscope. The measuring light and the reference light are made incident on the fixed mirror means provided in the vicinity thereof and at least two reflecting points of each reflecting surface by the optical path means, and the objective lens or the like is caused by the change in the optical path length difference between the reflected light. The amount of movement of the lens mount on the optical axis of is detected.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows, as an embodiment according to the present invention, a schematic configuration of a moving distance measuring apparatus to which the principle of a plane mirror interferometer mounted on a microscope is applied.

This moving distance measuring apparatus moves up and down by a laser light source 1 for generating a laser beam, a polarization beam splitter 2 for splitting the generated laser beam into reference light and measuring light which will be described later, and a drive unit (not shown). A perforated plane mirror (moving mirror) 5 attached to the upper part of a possible lens mount (objective lens barrel) 11, and a perforated plane mirror 5 fixed between the polarization beam splitter 2 and the perforated plane mirror 5. Also a large-diameter perforated plane mirror 9, a polarization beam splitter 2, and a perforated plane mirror (fixed mirror) 9
A quarter-wave plate 8 provided between the reference beam and the measurement beam, and the corner cube 6 and the half-wave plate 7 provided on the opposite side of the polarization beam splitter 2 from the polarization beam splitter 2. The reflecting mirror 3 that reflects between the perforated plane mirrors 5 and 9, the quarter-wave plate 4 provided between the reflective mirror 3 and the perforated plane mirrors 5 and 9, and the perforated plane mirror 5, Detector 1 for detecting reference light and measurement light reflected by 9
0, and the objective lens 12 of the microscope attached to the lens mount 11. What is mounted on the lens mount 11 is not limited to the objective lens of the microscope. The perforated plane mirror 9 is fixed to the polarization beam splitter 2 and the reflection mirror 3.

A length measuring operation in the moving distance length measuring device thus constructed will be described. First, the laser light source 1
The laser light from is incident on the polarization beam splitter 2,
It is split into reference light and measurement light. Here, the reference light and the measurement light are linearly polarized lights that are orthogonal to each other.

The reference light reflected by the polarization beam splitter 2 is transmitted through the quarter-wave plate 8 and a plane mirror 9 with a hole is formed.
The reflected light is transmitted through the quarter-wave plate 8 again, becomes linearly polarized reference light rotated by 90 degrees, and is transmitted through the polarization beam splitter 2. The reference light that has passed through the polarization beam splitter 2 passes through the corner cube 6 and the half-wave plate 7 and becomes linearly polarized reference light that is rotated 90 degrees again, and is reflected by the polarization beam splitter 2 and the reflecting mirror 3. To be done.

Further, the reference light reflected by the reflecting mirror 3 is 1
It passes through the quarter wave plate 4, is reflected by the perforated plane mirror 9, passes through the quarter wave plate 4 again, and is rotated 90 degrees,
It is incident on the detector 10.

On the other hand, the measurement light transmitted by the polarization beam splitter 2 is reflected by the reflecting mirror 3, is transmitted through the quarter-wave plate 4, is reflected by the perforated plane mirror 5, and is again the quarter-wave plate 4. Of the linearly polarized light, which is rotated by 90 degrees and becomes the measuring light of linearly polarized light, which is reflected by the reflecting mirror 3 and the polarization beam splitter 2.
Then, the measurement light reflected by the polarization beam splitter 2 passes through the corner cube 6 and the half-wave plate 7 to become the measurement light of linearly polarized light which is rotated by 90 degrees again, and becomes the polarization beam splitter 2 and the quarter-wave plate 4. Is reflected by the perforated plane mirror 5, again transmitted through the quarter-wave plate 4, reflected by the polarization beam splitter 2, and incident on the detector 10.

The perforated plane mirror 5 is fixed to the lens mount 11. The perforated plane mirror 9 is fixed to the polarization beam splitter 2 and the reflection mirror 3. The perforated plane mirrors 5 and 9 are both objective lenses 12
A hole of a size that does not block the observation light path is secured. Here, when the lens mount 11 moves by the displacement L, the detector 10 obtains a periodic interference signal with the wavelength of the laser light source 1 as a length reference.

When this interference signal is I, it can be expressed as follows: I = A1 ² + A2 ² + 2 · A1 · A2 · Cos (4nL / λ). Where A1 is the amplitude of the measurement light, A
2 is the amplitude of the reference light, λ is the laser wavelength value of the laser light source 1,
n is the refractive index of the optical path, and is the refractive index of air when used in air.

Usually, the amount of movement of the objective lens is very small, and high resolution and high accuracy are often required. In FIG. 1, the reference light and the measurement light have a substantially common optical path, which is resistant to disturbance and enables stable length measurement.

The perforated plane mirror 5 reflects the measurement light twice, but since it is reflected once at each target position with respect to the optical axis of the objective lens 12, the optical axis of the objective lens 12 is reflected. The amount of movement of the upper lens mount 11 can be accurately measured.

That is, it becomes possible to eliminate the Abbe error generated in the conventional structure shown in FIG. Further, since the optical path length difference ΔZ (shown in FIG. 1) between the reference light and the measurement light can be set to about several nm, the wavelength stability of the laser light source 1 does not need to be high.

Therefore, if the length measurement accuracy is not particularly required to be high, a simple wavelength-stabilized laser can be used, which is advantageous for cost reduction and size reduction. For example, it is possible to use a small laser light source such as a semiconductor laser, and it is possible to realize a small size and a low price as a whole. In particular, when an interferometer utilizing the interference of laser light as shown in FIG. 1, for example, an interferometer applying the principle of a plane mirror interferometer is incorporated in a microscope or the like, a great advantage can be obtained in terms of downsizing.

Although the description has been made based on the above embodiment, the present invention also includes the following inventions. (1) A laser light source, a polarization beam splitter for splitting the laser light from the laser light source into a reference light and a measurement light, and a movable objective lens barrel, which is attached to the upper end of the movable path of the objective lens barrel and does not enter the observation path. Moving mirror means for reflecting the measurement light at least at two points on the flat reflecting surface, and fixed parallel to the reflecting surface of the moving mirror means at a predetermined interval, and at least the incident reference light on the flat reflecting surface. Fixed mirror means reflecting at two points, reference light and measurement light reflected by the moving mirror means and the fixed mirror means are incident, and the objective on the optical axis is changed by a change in optical path length difference between the reference light and the measurement light. Detecting means for detecting the amount of movement of the lens barrel, and predetermined reflection of the reference light and the measuring light split by the polarization beam splitter by the moving mirror means and the fixed mirror means, respectively. Guided at the movement amount measuring apparatus for measuring light and reference light reflected by the respective reflecting locations, characterized by comprising, an optical path means for guiding said detecting means.

(2) Each of the plane mirrors of the movable mirror means and the fixed mirror means reflects the measurement light at a target position with respect to the optical axis of the objective lens once and twice respectively, and the objective lens The distance measuring device according to (1) above, which measures the amount of movement of the objective lens barrel (lens mount) on the optical axis.

(3) The movement length measuring device according to (2), wherein the plane mirror has a shape in which a hole is formed so as not to enter the observation path of the objective lens of the lens mount.

(4) The laser light from the laser light source is
The movement length measuring device according to (1), wherein the polarization beam splitter splits the reference light and the measurement light, which are linearly polarized light orthogonal to each other.

(5) The reflecting surface of the moving mirror means and the reflecting surface of the fixed mirror means are arranged close to each other by a predetermined distance (optical path length difference ΔZ between the reference light and the measurement light) to obtain a predetermined wavelength stability. The movement length measuring device according to (1) above.

[0025]

As described above in detail, according to the present invention, the amount of movement of the lens mount on the optical axis of the objective lens or the like in the microscope can be measured by utilizing the interference of laser light. A length measuring device can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a movement length measuring device which is attached to an objective lens or the like of a microscope of the present invention and measures a displacement in a direction of an optical axis.

FIG. 2 is attached to an objective lens of a conventional microscope,
It is a figure which shows schematic structure of the movement amount measuring device which measures length by the displacement to an optical axis direction.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Laser light source, 2 ... Polarization beam splitter, 3 ... Reflecting mirror, 4, 8 ... 1/4 wavelength plate, 5, 9 ... Perforated plane mirror, 6 ... Corner cube, 7 ... 1/2 wavelength plate, 10 ... Detector, 11 ... Mount, 12 ... Objective lens.

Claims (3)

[Claims] 1. A laser light source, a polarization beam splitter for splitting the laser light from the laser light source into a reference light and a measurement light, and a movable objective lens barrel which is attached to a peripheral portion outside an observation path range and is incident. The moving mirror means for reflecting the measured light at at least two points on the reflecting surface, and the fixed reference light which is fixed in parallel with the reflecting surface of the moving mirror means at a predetermined interval, and the incident reference light at at least two points on the reflecting surface. Fixed mirror means for reflecting the light on the optical axis, the reference light and the measurement light reflected by the movable mirror means and the fixed mirror means, and the objective lens mirror on the optical axis due to a change in optical path length difference between the reference light and the measurement light. Detecting means for detecting the amount of movement of the cylinder, and the reference light and the measuring light split by the polarization beam splitter are respectively reflected at predetermined reflection points of the moving mirror means and the fixed mirror means. Come, the movement amount measuring apparatus reference light reflected by the respective reflecting locations and the measurement light, characterized by comprising, an optical path means for guiding said detecting means. 2. The optical path means of the movement length measuring device comprises a plurality of wavelength plates for performing predetermined polarization, a corner cube for changing the optical path direction, and a reflecting mirror, and the reference light split by the polarization beam splitter is , First
Of the linearly polarized reference light which is transmitted through the 1/4 wavelength plate, is reflected at the first predetermined position on the reflecting surface of the fixed mirror means, is transmitted again through the 1/4 wavelength plate, and is rotated by 90 degrees. Polarized light, transmitted through the polarization beam splitter, passed through a corner cube and a half-wave plate, and again becomes linearly polarized reference light rotated by 90 degrees, and is reflected by the polarization beam splitter and a reflecting mirror. The reference light reflected by the reflecting mirror is transmitted through the second quarter-wave plate, is reflected at the second predetermined position on the reflecting surface of the fixed mirror means, and is again reflected by the second quarter-wave plate. The measurement light, which is transmitted and rotated by 90 degrees to form a first optical path incident on the detection means, and which is branched by the polarization beam splitter is reflected by the reflecting mirror to generate a second quarter wavelength. Transmits through the plate and is reflected at the first predetermined location on the reflecting surface of the moving mirror means. It is again transmitted through the second quarter-wave plate, 90
The linearly polarized measuring light rotated by a degree is reflected by the reflecting mirror and the polarizing beam splitter, and the measuring light reflected by the polarizing beam splitter passes through the corner cube and the half-wave plate, and again. 9
After being polarized into the linearly polarized measuring light rotated by 0 °, it is transmitted through the first quarter-wave plate, is reflected at the second predetermined position on the reflecting surface of the moving mirror means, and is again the first. Transmitted through the quarter-wave plate and reflected by the polarization beam splitter,
2. The movement length measuring device according to claim 1, wherein a second optical path that enters the detection means is formed, and the reference light and the measurement light are formed in a common optical path except for a reflecting surface. 3. Amplitude of the measurement light is A1, amplitude of the reference light is A2, and laser wavelength value of the laser light source is a change in the optical path length difference between the reference light and the measurement light detected by the detection means of the movement amount measuring device. Is λ, the refractive index of the optical path is n, and the displacement length of the objective lens barrel is L, the detection means is: I = A1 ² + A2 ² + 2 · A1 · A2 · Cos (4nL
2. The movement length measuring apparatus according to claim 1, wherein a periodic interference signal I based on the wavelength of the laser light source as a length reference is obtained based on / λ).