JPH0617785B2 - Interference contrast method linear meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Object of the Invention [Industrial field of use] The present invention relates to a linear meter using an interference contrast method.

For example, in a machine tool or the like, a tool rest or the like moves linearly along a guide, and the quality of the linearity of the motion is an important factor for determining the quality of machining accuracy. Therefore, in such a machine tool or the like, it is necessary to inspect lateral shake (displacement one component or two components in a plane perpendicular to the movement direction) of the tool post or the like at the time of assembly or accuracy inspection. There is also an attempt to constantly detect the lateral shake of a tool post or the like during machining and control the motion linearly to improve machining accuracy. Further, a precision moving table is incorporated in an optical machine and a precision machine, and a highly accurate measurement inspection is required in the manufacturing process.

[Prior Art] In such a case, a linear meter is used, and as the optical linear meter, an auto collimator, a laser linear meter (tooling laser), or the like is conventionally used.

[Problems to be Solved by the Invention] However, these conventional linear meters detect the rotation or displacement of one component, and the measurement accuracy is on the order of μ, and the accuracy is insufficient. It was insufficient for the purpose.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a linear meter that can perform real-time interference easily and that enables highly accurate displacement measurement.

(B) Configuration of the Invention [Means for Solving the Problem] To this end, the interference contrast method linear meter of the present invention is a light source that forms a light beam on the optical axis at one end side of the optical axis. A device, an interference fringe observation device at one end of the optical axis, and another two light beams which are located in the middle of the optical axis and are symmetrical to the optical axis from the light beam and a lateral deviation occurs. A two-beam generation device that causes a phase shift between the other two light beams, and a pair that is positioned symmetrically to the optical axis on the other end side of the optical axis and that reflects the other two light beams in the same direction as the incident direction. A mirror, the light source device, the interference fringe observation device, and the pair of mirrors are attached to one of a fixed body and a moving body to be inspected, and the two-beam generation device is attached to the fixed body and the inspected body. It is characterized by being attached to the other of the moving bodies.

Hereinafter, details of the present invention will be described with reference to the drawings illustrating an embodiment.

In FIG. 1, 1 is a linear meter. The linear meter 1 has a light source device 2. As the light source device 2, a He-Ne laser light source, a semiconductor laser light source, or the like can be used. The light source device 2 is located on one end side of the optical axis 3 and forms a light beam 6 on the optical axis 3 via the mirror 4 and the half mirror 5.

An interference fringe observation device 7 is located on the transmission side of the half mirror 5. The interference fringe observation device 7 includes a mirror 8 and an observation surface 11. A photodetector for measuring the intensity of light is placed at the position 0 on the observation surface 11. This observation surface 11
May be replaced by the hologram H as described later. Optical axis 3
A two-beam generation device 12 is arranged midway. The two-beam generation device 12 has two beams 1 symmetrical with respect to the optical axis 3 from the incident beam.
It is possible to use a grating G or a wedge glass 17 having two symmetrical sloping surfaces 5 and 16 having the same angle, which will be described later. When the grating G is irradiated with the light beam 6, (+) first-order and (−) first-order diffracted lights 13 and 14 are generated, and these lights are used. As the grating G, a commercially available one can be used, or a grating (hologram grating) produced by recording light in an oblique direction on a photographic plate using parallel light as reference light may be used. A pair of mirrors 21 and 22 are arranged on the other end side of the optical axis 3. A pair of mirrors 2
1, 22 are symmetric with respect to the optical axis 3 and the two light beams 1
It is perpendicular to the optical axes of 3,14. Therefore, the pair of mirrors 21 and 22 reflects the two light fluxes 13 and 14 in the incident direction.

Light source device 2, interference fringe observation device 7, pair of mirrors 21,2
2 is mounted on the fixed body 23, and the two-beam generator 12 is mounted on the moving body 24. The moving body 24 is scheduled to move in the direction of the optical axis 3, and the displacement Δx in the direction perpendicular to the moving direction when moving in the optical axis direction is the detection target amount. .

[Operation] Lateral displacement Δ in the interferometric linear meter 1 configured as described above
The detection of x is performed as follows.

A laser beam is emitted from the light source device 2, the optical path is changed by the mirror 4 and the half mirror 5, and the light beam is incident on the two-beam generation device 12. Since the two-beam generation device 12 uses the grating G, the incident light beam is split into two light beams symmetrical with respect to the optical axis 3, that is, the light beam 13 and the light beam 14. The light flux 13 and the light flux 14 are reflected in the incident direction by the mirrors 21 and 22, and are overlapped by the two light flux generation device 12 to form an interference fringe. The interference fringes pass through the half mirror 5 and the mirror 8
The optical path is changed by and the image is observed on the observation surface 11 at the zero point.

FIG. 2 shows the relationship between the lateral deviation Δx of the grating G and the phase change of the interference fringes. In FIG. 2, the solid line represents the light beam for indicating the phase in the initial state, and the broken line represents the light beam for indicating the phase delay when the lateral deviation occurs.

Assuming that the inclination angle of the slope 15 of the light flux 13 is θ, a phase shift δ when the moving body laterally shifts from left to right.
₁ is δ ₁ = (2π / λ) ΔX sin θ, and the phase shift δ ₂ when the moving body laterally shifts from right to left is δ ₂ = (2π / λ) ΔX sin θ.

Regarding the light flux 14, the phase shift δ ₃ when the moving body laterally shifts from left to right is δ ₃ = − (2π / λ) ΔX sin θ, and the phase shift δ when the moving body laterally shifts from right to left. ₄ is [delta] ₄ =-(2 [pi] / [lambda]) [Delta] Xsin [theta].

After all, the overall phase shift δ is δ = (δ ₁ + δ ₂ ) − (δ ₃ + δ ₄ ) = δ ₁ = (8π / λ) ΔX sin θ (1) On the other hand, the intensity change of the interference fringes and the phase change The relationship with is: I (ΔX) = A + Bcosδ ... (2) (1) Substituting the light intensity of the interference fringes into I (ΔX), I (ΔX) = A + Bcos {(8π / λ) × ΔX sin θ} (3) FIG. 3 shows the relationship between light intensity and phase. In this case as well, as in the normal interference contrast method, 0 to π
Used as a linear meter between The values of A + B and A−B are obtained in advance. Next, when the intensity I (ΔX) is observed,
ΔX is calculated from the equation (3). However, θ is measured in advance when the grating is made.

In this way, by observing the change in the light intensity of the interference fringes on the observation surface 11, the lateral displacement amount ΔX of the moving body can be obtained from the equation (3).

For example, if θ = 30 ° and δ = π / 100, then ΔX = 1.5 × 10 ⁻³ μm.

[Other Embodiments] The hologram H may be arranged in place of the observation surface 11 located at the 0 point. In this case the hologram is
At the reference position between the fixed body 23 and the moving body 24, a photographic plate was placed at the position of 0, and the object light 5 was recorded by using the light of the interference fringes of the light fluxes 13 and 14 as the reference light, and the photographic processing was completed. It is a thing. In such a configuration, when the hologram H is illuminated with the object light 25 and the light of the interference fringes, the object light 25 and the reproduction light of the hologram H form an interference fringe, and thus the interference fringe is observed to detect the lateral shift. Will be done.
When the adjustment of the angles of the mirrors 21 and 22 is incomplete, the accuracy is lowered. However, by using the hologram H, even if the adjustment of the mirrors 21 and 22 is incomplete, the hologram H is used for correction and complete adjustment is made. Is detected with the same intensity photodetector as (This is the same idea as the correction of the aberration of the hologram.) FIG. 4 shows a linear meter 1a according to another embodiment of the present invention. In this linear meter 1a, a wedge glass 17 is used instead of the grating G. The wedge glass 17 is composed of symmetrical inclined surfaces 15 and 16 having the same angle, and when the light beam 6 and the light beam 6'reflected from the front and back surfaces of the half mirror 5 illuminate the wedge glass 17, the wedge glass 17 is symmetrical with respect to the optical axis 3. 2 light fluxes 13 and 14 are generated.

(C) Effects of the Invention As is clear from the above description, according to the present invention, it is possible to obtain a linear meter that enables displacement measurement with particularly high accuracy.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of an interference contrast method linear meter according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing a relationship between a lateral shift amount and a phase change of interference fringes, and FIG. FIG. 4 is a diagram showing a phase relationship, and FIG. 4 is a structural explanatory diagram showing an interferometric linemeter according to another embodiment of the present invention. 1 ... Linear meter, 2 ... Light source device, 3 ... Optical axis, 4 ... Mirror, 5 ... Half mirror, 6 ... Luminous flux, 7 ... Interference fringe observation device, 8 ... Mirror, 11 ... Observation plane, 12 …… 2
Luminous flux generator, 13 ... Luminous flux, 14 ... Luminous flux, 15 ...
Slope, 16 ... Slope, 17 ... Wedge glass, 21 ...
… Mirror, 22 …… Mirror, 23 …… Fixed body, 24 ……
Moving object, 25 ... Object light, H ... Hologram, G ... Grating

Claims (1)

[Claims] 1. A light source device which forms a light beam on the optical axis at one end side of the optical axis, an interference fringe observation device at one end side of the optical axis, and an intermediate position of the optical axis. A two-beam generation device that generates another two light beams symmetrical to the optical axis from the light beam and causes a phase shift in the other two light beams when a lateral shift occurs, and the light beam on the other end side of the optical axis. And a pair of mirrors that are symmetrical with respect to the axis and that reflect the other two light beams in the same direction as the incident direction. The light source device, the interference fringe observation device, and the pair of mirrors are fixed to the fixed body and the mirror. An interference contrast method linear meter, characterized in that it is attached to one of the moving bodies to be detected, and the two-beam generation device is attached to the other of the fixed body and the moving body to be inspected.