JPS61175505A - Micrometer - Google Patents

Abstract

PURPOSE:To enable the measurement of length with a high resolution, by mounting a first optical means on a box body to reflect laser light to a measuring element while a second optical means is mounted somewhere in the course thereof to form an interferring light to accomplish photoelectric conversion of the interferring light. CONSTITUTION:A laser light comprising two frequencies f1 and f2 are emitted in the direction of the arrow 8 from a laser oscillator 5. A part of the laser light is converted into a reference signal SR with the frequency f1-f2 with the first photoelectric detector 12. On the other hand, a part of the laser light as such with the frequency f2 only is shifted in the direction with a prism 18 to be emitted in the direction of the arrow 17. On the other hand, the laser light transmitted through a halfmirror 14 will be as such with the frequency f1 and converged with the laser light with the frequency f2 in the direction of the arrow 17 to be received with the second photoelectric detector 29. Then, when an object to be measured is removed from a base, the laser light with the frequency f1 in the direction of the arrow 24 changes in the frequency and a Doppler signal SD is outputted from the detector 29. Thus, after the counting of the signals SR and SD with counters 32 and 33, the counts signal SC1 and SC2 are outputted to a subtractor 34 to compute the difference there between.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a micrometer that measures displacement using interference of laser light.

[Technical background of the invention and its problems]

Generally, micrometers used for precision length measurement are
The pitch of the screw is used. By using a vernier, it is possible to measure at 0.01 m1. When measuring length with higher precision, an electric micrometer with a built-in differential transformer is used.

However, conventional electric micrometers have the disadvantage that it is difficult to obtain a resolution of 1 μm or less.

On the other hand, even if the length can be measured with a resolution of 1 μm or less, the measurement range is very short and it is impossible to measure a large amount of displacement with a resolution of 1 μm or less.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a micrometer that can measure length with high resolution even if the displacement is large.

[Summary of the invention]

A first optical means for reflecting a laser beam is integrally attached to a probe elastically supported in a movable manner in a housing, and an interference beam is emitted along with a reflected laser beam from a tenth optical means in the middle of the housing. A second optical means for forming the probe is attached, and the amount of displacement of the probe is calculated based on an electrical signal obtained by photoelectrically converting the interference light.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the micrometer of this embodiment.

This micrometer has two slightly different frequencies'
A reference signal SR and a Doppler signal 8D are obtained by a laser beam oscillation unit (1) that generates a coherent laser beam of 1 + ft and a laser beam emitted from the laser beam oscillation unit (1) in which various optical components are stored. A main body (2);
It consists of a calculation section (3) that performs length measurement calculation processing based on the reference signal SR and Doppler signal SD. The main body (2) has a cylindrical housing (4). and,
The laser beam oscillator (1) includes a Helium Neon (He-Ne) laser oscillator (5) provided apart from the housing (4), one end connected to this laser oscillator (5), and the other end connected to the He-Ne laser oscillator (5). is connected to one end plate (6) of the housing (4), and an optical system (7
). The laser light emitted from this optical system (7) is projected in the direction of the arrow (8). Accordingly, the main body (2) has a beam of laser light from the optical system (7) installed inside the housing (4) and the end plate (6) and extending in the direction of the arrow (8). An optical system (9) consisting of a combination of lenses that magnify and make parallel light; and a laser beam fixed to the inner wall of the housing (4) at a position in front of this optical system (9) in the direction of arrow (8). Arrow (8)
A first half mirror (Ll) that branches in the direction of arrow a1 perpendicular to the direction, and a first half mirror (Ll) fixed to the inner wall of the housing (4), which receives laser light in the direction of the arrow and photoelectrically converts it to a frequency of f, -
A first photoelectric detector a outputs a reference signal SR of f, and a laser beam fixed to the inner wall of the housing (4) in front of the first No.-7 mirror housing in the direction of arrow (8). A second half mirror α-shaft splits a part of the light in the direction of arrow α4, which is a right angle direction, and a second half mirror α is fixed to the inner wall of the housing (4) and directs the laser beam in the direction of arrow α4 to the direction of arrow (8). Arrows in parallel and opposite directions (total reflection in one direction and this arrow (1
The laser beams in four directions are totally reflected in the direction of the arrow (le) which is parallel and opposite to the direction of the arrow 0, and then enter the second half mirror (14) again, and the laser beams are reflected by the second half mirror (I). 8) Arrow α that is parallel and opposite to the direction
η Corner cube that reflects the force direction (corner c
It is fixed to the inner wall of the casing (4) so as to be between the first prism α barrel shaped like an arrow (13) and the first prism H and the second half mirror α barrel. f
1. Frequency f of the laser light consisting of f.

A first optical filter 0 that emits only the laser beam toward the first prism (Ie) and the other end plate of the housing (4).
The arrow (8) is axially through the sleeve Qυ.

A measuring element @ which is slidably supported in the αη direction and whose tip is formed into a hemispherical shape is connected to the rear end of the measuring element Co., Ltd., and an arrow ( The laser beam in the direction 8) is shown by the arrow (11) which is parallel to the
After total reflection in direction C), total reflection in direction of arrow Aη on the same optical path as direction of arrow aη force is applied to Konaki Island-B(
corner cube) shaped second prism (c)
and.

Between the second half mirror (14) and the second prism (C), the V- in the direction of arrow (8) is composed of two frequencies f, f, f, emitted from the second half mirror (14). A 20th optical filter (G) fixed to the inner wall of the casing (4) so that the laser beam with a frequency f1 among the laser beams enters the second prism (C) K;
c) The second half mirror - the housing (4) close to the α side
A ring-shaped support plate protruding from the inner wall, and an intervening device between the support plate and the second prism (A) and between the end plate and the second prism (A). An elastic body (c) that elastically supports the probe at a certain position when no external force is applied to the probe is attached, and an elastic body (c) that is fixed to the end plate (6) and receives the αη force indicated by the arrow It consists of four second photoelectric detectors that input directional laser light and perform photoelectric conversion. Therefore, the frequency of the laser beam having the same wave number f1 incident on the second prism (c) K changes by Δf due to the Doppler effect accompanying the movement of the probe (2). Therefore, arrow 124
The frequency of the laser beam in the direction is f1±Δf. Therefore,
The frequency of the laser beam in the direction of arrow αη force emitted from the second half mirror side consists of two frequencies: w′1±Δf1 and f. A second photoelectric detector receives laser light in the direction of force indicated by the arrow αη, which includes the two frequencies of .

Doppler signals SD with frequencies f, -f, ±Δf are output. On the other hand, the arithmetic unit (3) includes a first amplifier (to) which is electrically connected to the output side of the first photoelectric detector @ and amplifies the reference signal SR, and an output side of the 20th photoelectric detector @. a second electrically connected to the Doppler signal SD for amplifying the Doppler signal SD;
amplifier C31) and the output side of the first counter (3 points and second amplifier G1) that is connected to the output side of the first amplifier (to) and counts the frequency of the reference signal SR over a certain period of time. a second counter (c) which is connected and powers the frequency of the Doppler signal 8D over a certain period;
a subtracter (product) that calculates the difference between the count signal SC8 output from the counter C33 and the count signal SC1 output from the second counter (to) and outputs a difference signal SX;
It consists of a computing unit (to) that performs arithmetic processing for length measurement based on the difference signal SX output from the machine (to), and a display (to) that displays the length measurement result of this computing unit (to). .

Next, the operation of the micrometer having the above configuration will be described.

First, as shown in FIG. 2, the main body (2) is fixed so that the probe contacts the upper surface of the base 07 in the released state. Next, push up the measuring head (sha) and place the measured object amount on the base (
37), as well as the measuring head (sha) and base C17.
) to hold the object to be measured (to). Thus, a laser beam having two frequencies '1 +f is emitted in the direction of the arrow (8) via the laser oscillator (5) and the optical system (7).

Then, a part of the laser beam in the direction of arrow (8)
The half mirror αυ branches in the direction of arrow a1.

The laser beam in the direction of arrow α1 is transmitted to the first photoelectric detector α2
The signal is photoelectrically converted and one frequency is converted into a reference signal of f, -f. On the other hand, a portion of the laser light in the direction of arrow (8) that has passed through the first half mirror αυ is changed direction by the second 8-7 mirror I in the direction of arrow 0.

When the laser beam in the direction of arrow 13 passes through the first optical filter member, it becomes a laser beam with only a frequency f, and the direction is sequentially changed to the directions of arrows ni and rLe by the first prism α$. , again the first half mirror (1
After being incident on 1), the light is emitted in the direction of arrow CL, ).

On the other hand, the laser beam in the direction of arrow (8) that has passed through the second half mirror I becomes a laser beam with only a different frequency when it passes through the second optical filter (1), and passes through the second prism (C). incident. Therefore, the laser beam of frequency f that is incident on this second prism (c) is as shown by the arrow.

(Foundation) direction. When the laser beam in the direction of the arrow passes through the second half mirror I, it merges with the laser beam of frequency f in the direction of the arrow C4.

The light is received by a second photoelectric detector. Next, measure the object (
property) is removed from the base 07). Then, the measurement forecast descends in the direction of the arrow (8) due to the urging force of the elastic body (to) and comes into contact with the upper surface of the base (b). At this time, the measuring head (a)
The second prism (c) is lowered integrally with this. the result.

The frequency of the laser beam having a frequency f in the direction of arrow C4 changes by Δf due to the Doppler effect, and becomes fl±Δf.

Therefore, one frequency ft-f, ±
A top 2 signal SD of Δf is output. Thus, the reference signal 8R and the Doppler signal SD are amplified by the first and second amplifiers, Gυ, and input to the first and second counters, respectively. Therefore, the frequencies of these first and second counters (to) and (to) are counted over the entire period during which the probe (2) is displaced from position X to position -. Then, after the counting is completed, the count signals sc, , sc, indicating the counting results are outputted to a subtracter, and the difference N between them is calculated. By the way, the difference N
Since Δf is integrated during the movement of the second prism (c), a linear relational expression is established.

Here, the relationship f1λ1=C (where C is the speed of light) is used. Also &) C! -"l indicates the amount of displacement of the measuring head (company) and the length 7 to be measured by the pick. Therefore.

λ.

One - N 00. ■ Therefore, the arithmetic unit (goods) to which the difference signal SX indicating the difference N is input
Then, the length L is calculated according to the above equation (2), and the result is displayed on the display (G).

Thus, the micrometer of this example.

High precision measurement is possible without restrictions on the measurement range. For example, when a He-Ne laser is used as the laser beam, the resolution is about 0.15 μm in a length range of several meters.

In the above embodiment, N is counted using the Doppler effect, but as shown in FIG. After projecting a laser beam toward the device (40 and the beam splitter (41), which is integrally attached to the measuring head □□□, which can be freely displaced in the axial direction), The laser beam reflected by Gi3 is again branched by the beam splitter (41) in the perpendicular direction (in the direction of the arrow), and is first split into the beam splitter (41).
1J, the laser beam is reflected in the opposite direction to the direction of the arrow and merged with the laser beam reflected again in the direction of the arrow from the reflecting mirror (c) K fixed to the inner wall of the casing (cll).
A photoelectric detector fixed to the inner wall of II) may be made to receive light from K side.

Then, based on the electrical signal output from the photoelectric detector IA6), the number N of changes in the brightness of the interference light when the measuring tip (@ is displaced by the measuring distance) is counted. The length J of the object to be measured can be calculated using the following equation.However, 1 is a fraction.

Tsumashi, in this case 1 reflector (when moving 43,
This method utilizes the fact that the brightness of the interference light changes periodically with a period of movement of 1/2 wavelength. Furthermore, in the first embodiment described above, the first half mirror (11) may be replaced by a beam splitter. Furthermore, the second
half mirror I and first and second optical filters (
1) and (E) can be replaced with a polarizing beam splitter that transmits only the laser beam of one frequency f1. Yet again.

The first and second prisms αL (cat's eye) are made of a combination of a convex lens and a concave mirror.
ye) may also be used. In addition, the first and second amplifiers (
), connect a doubler to the output side of 01).

By multiplying the frequency and making the length corresponding to l dipit even smaller than λ,/2, the reading can be made more precise. Furthermore, in the case of the embodiment shown in Fig. 3, if the reflected light from the beam splitter (41) is re-reflected by the prism (c) via the fixed reflecting mirror (c), the 1/4 wavelength It changes periodically with the movement of (4th
(see figure). In any case, since the embodiments shown in FIGS. 3 and 4 use a semiconductor laser device (4G) as the laser beam oscillation section, the micrometer can be made smaller and lighter, and has the special effect of improving portability. play.

〔Effect of the invention〕

The micrometer of the invention enables high-precision length measurement with a resolution of 0.15 μm or less over a length range of several meters, without the measurement range being restricted as with electric micrometers.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a micrometer according to an embodiment of the present invention, FIG. 2 is a diagram showing length measurement by the micrometer of FIG. 1, and FIGS. 3 and 4 are diagrams showing other embodiments of the invention. FIG. 2 is a configuration diagram of main parts of a micrometer. (1): Laser oscillation section, (2): Main body section. (3): Arithmetic unit, (4): Housing. α4 = second half mirror (second optical means). @: Measuring head. (c): Second prism (first optical means). @: Second photoelectric detector. Agent: Patent attorney Kensuke Chika (and 1 other person)

Claims (1)

[Claims] A micrometer characterized by having the following configuration. (a) Laser light oscillation unit that oscillates laser light. (b) A casing on which the laser beam is projected inside, a probe elastically supported by the casing so as to be movable back and forth, and a probe attached to the probe to reflect the laser beam to obtain a reflected laser beam. a first optical means; a second optical means attached to the housing and reflecting the laser beam along the same optical path as the reflected laser beam to obtain interference light; a second optical means attached to the housing and generating the interference light; A main body including a photoelectric detector that receives interference light and converts it into electricity. (c) A calculation unit that calculates the amount of displacement of the probe based on the electrical signal output from the photoelectric detector.