JPH05306904A - Length measuring device - Google Patents

Abstract

(57) [Summary] (Corrected) [Purpose] Length measuring equipment that does not cause measurement error even if the temperature changes
Provision of storage. [Structure] Counts the number of light and dark that occur due to light interference
In a length measuring device that measures length by doing
The body 10 is mounted on a base 11 and a laser beam provided on the base 11.
The oscillator 12 and the optical path of the light emitted from the laser oscillator 12
Movable target 14 that can slide and laser oscillator 1
The light emitted from 2 is the measurement light L₁And reference light L_TwoSplit into and
Interference beam splitter 16 and movable target 14
Measurement reference point P, which is the movement start point ₀Fixed near the
Target 20 and interference beam splitter 16
Split reference light L_TwoTo guide the fixed target 20
In addition, the light reflected by the fixed target 20
A reflective optical member (mirror) 18 that guides the slitter 16 is provided.
Yes, the amount of expansion and contraction due to temperature changes in the measurement optical path and the reference optical path are the same.
I chose

Description

Detailed Description of the Invention

[0001]

[Industrial application] When a coherent device constructs a rangefinder that utilizes the interference of two lights, the interference fringes repeat light and dark each time the phase of one light advances by half a wavelength. It is well known that it is expressed as a function, and the present invention relates to a length measuring device that accurately measures the length of a block gauge or the like by utilizing the interference effect of this light.

[0002]

2. Description of the Related Art FIGS. 3 and 4 show a conventional length measuring device, which comprises a length measuring device main body 1 and a display device 2. The length measuring device main body 1 includes a laser oscillator 3 provided at one end of the gantry 1a.
A movable target prism 4 provided at the other end of the pedestal 1a, a fixed target prism 6 with a built-in interference beam splitter 5 provided in the vicinity of the laser oscillator 3 on the optical path of the laser light, and inside the laser oscillator 3. And a light receiving sensor (not shown) for measuring the intensity change of the interference fringes due to the interference effect of the light produced by the movable target prism 4 and the fixed target prism 6, and a position in front of the light receiving sensor in the laser oscillator 3 as well. It is provided with a polarization optical system (not shown) for discriminating whether the movable target prism 4 moves forward or backward.

The laser beam emitted from the laser oscillator 3 is split into a reference beam reflected by the fixed target prism 6 and a measuring beam reflected by the movable target prism 4 in the interference beam splitter 5. When the movable target prism 4 is slid by an amount corresponding to the length of the object to be measured W, the light receiving sensor 8 outputs light and dark data generated by the interference between the reference light and the measurement light, and this is displayed on the display 2
The length of the object to be measured W is measured by counting with an internal processing circuit (not shown). Reference numeral P ₀ is a movement start point of the movable target prism 4, which is a reference point for length measurement.

[0004]

However, in the above-described conventional length-measuring device, when the temperature of the mount 1a of the length-measuring device main body 1 changes, the reference point P ₀ changes due to thermal expansion.
For example, the length of the frame 1a is at 3m, the thermal expansion coefficient of the material (cast iron) of the frame 1a 11.6 × 10 ^- temperature between When ⁶ / ° C., which was left to measuring machine body 1a 1 hour Is 0.5 ° C
When elevated, stand 1a is 3 × 11.6 × 10 ^{- 6}
X 0.5 = 0.0000174 m, that is, the reference point P ₀ extends 0.017 mm from the left end of the gantry 1a, and the reference optical path on the fixed target prism 6 side does not change, but the measurement optical path on the movable target prism side changes. It will be extended by 0.017 mm. Therefore, the origin display value on the display device 2 changes from "0.0000 mm" to "-0.0174 mm". In short, there is a problem that the change in thermal expansion of the pedestal 1a of the length measuring device body cannot be absorbed, which leads to a measurement error.

In particular, when several tens to several hundreds of DUTs having the same shape are continuously measured, a few tens of measurements are completed in a short time, but it is quite necessary to complete the measurement. take time. For example, if the reset button is pressed and the reference value is changed (zero point correction) prior to the measurement every one or every ten units, no error will occur.
It is very cumbersome and practically difficult to perform this zero correction for each measurement. For this reason, the temperature rises several hours after the start of the measurement, and when the measurement is continued despite the reference point position being shifted, the measured value is greatly deviated. Therefore, conventionally, measurement in a room where the temperature change is small has been forced.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide a length measuring device which does not cause a measurement error even if the ambient temperature in which the length measuring device is placed changes. ..

[0007]

In order to achieve the above object, in a length measuring apparatus according to the present invention, a laser beam is used as a reference light directed to a fixed target prism by a beam splitter, and a measurement light directed to a movable target prism. And the reference light reflected by the fixed target prism,
The measurement light reflected by the movable target prism when moving the movable target prism is received by the light receiving sensor,
In a length-measuring device that measures the length by counting the number of dark and light caused by the interference of these lights, a length-measuring device main body is provided on a long frame and at one end of the frame. A laser oscillator that emits light, a movable target prism that is mounted on a pedestal and can slide on the optical path of the emitted light from the laser oscillator, and is provided on the optical path of the laser light near the emission end of the laser light. , An interference beam splitter that splits the light emitted from the laser oscillator into a measurement light that travels straight and a reference light that is orthogonal to the measurement light, and a fixed beam provided near the measurement reference point that is the movement start point of the movable target prism on the pedestal The target light and the reference light split by the interference beam splitter are guided to the fixed target prism, and the light reflected by the fixed target prism is interfered with. A reflecting optical member for guiding the beam splitter, which is constituted to include.

According to a second aspect of the present invention, in the length measuring apparatus according to the first aspect, the laser oscillator is provided separately from the gantry.

[0009]

The fixed target prism is provided in the vicinity of the measurement reference point even if the pedestal expands and contracts and the optical path length of the measurement light changes due to a change in the temperature of the atmosphere in which the length measuring device body is placed. Therefore, the optical path length of the reference light changes by the same amount as the optical path length of the measurement light, and the expansion / contraction amount of the optical path length is offset.

Although the laser oscillator generates heat during operation, the heat generated by the laser oscillator is not transmitted to the gantry by separating the laser oscillator from the gantry.

[0011]

Embodiments of the present invention will now be described with reference to the drawings. 1 and 2 show an embodiment of a length measuring device according to the present invention. FIG. 1 is a front view of the length measuring device, and FIG. 2 is the length measuring device when measuring an object to be measured. FIG. In these drawings, reference numeral 10 is a length measuring device main body provided with a laser oscillator, a fixed target prism, a movable target prism, a light receiving sensor, etc., and the output of the light receiving sensor provided in the length measuring device main body 10 is data. It is displayed on the display unit 30 having a built-in processing circuit.

Reference numeral 11 denotes a long pedestal which is a case of the length measuring machine main body 10. The laser oscillator 1 is attached to one end of the pedestal 11.
2 is arranged horizontally, and the gantry 11 is provided with a movable target prism 14 that is slidable along the optical path of the laser light emitted from the laser oscillator 12.
A movement start reference point P ₀ of the movable target prism 14 is provided at the other end of the gantry 11, and the movable target prism 14 can slide from this reference point P ₀ to a position P ₁ close to the laser oscillator. An interference beam splitter 16 is provided at a position close to the laser oscillator 12 on the optical path of the laser light, and the laser light emitted from the laser oscillator 12 is a straight light by passing through the interference beam splitter 16. The measurement light L ₁ and the reference light L ₂ orthogonal to the measurement light (straight light) L ₁ are split. Stand 1
A mirror 18 is provided in the vicinity of the beam splitter 16 of No. 1, and the measurement light L ₂ passes through this mirror 18 and serves as a reference point P _0.
Is guided to the fixed target prism 20 fixed to the gantry 11 in the vicinity of. The reference light L ₂ is reflected by the fixed target prism 20, is reflected by the mirror 18, passes through the interference beam splitter 16, is provided in the laser oscillator 12, and is a polarization optics for discriminating the forward and backward movements of the movable target prism 14. It is guided to a light receiving sensor (not shown) also provided in the laser oscillator 12 via a polarization beam splitter (not shown) which is a system.

On the other hand, the measurement light L ₁ transmitted straight through the interference beam splitter 16 is reflected by the movable target prism 14 and is also guided to the light receiving sensor via the interference beam splitter 16. In the light receiving sensor that detects the phases of the measurement light L ₁ and the reference light 12, the movable target prism 14
The phase information is output together with the light and dark information due to the interference effect of light generated by the movement of the. Then, the output of the light receiving sensor is counted by the data processing circuit (not shown) in the display unit 30 for the number of light and dark, converted into numerical data and digitally displayed on the display unit 30.

In the actual length measurement work, first, the movable target prism 14 is positioned at the reference point P ₀ and a reset button (not shown) is pressed to set the zero point position. Next, the movable target prism 14 is slid to set the reference point P.
A sufficient space is provided between ₀ and the movable target prism 14 to hold the object to be measured W. At this time, the display 30
A distance La from the reference point P ₀ of the movable target prism 14 is displayed along with the sliding of the movable target prism 14.

Next, the object to be measured W is placed in this space and the movable prism 14 is slid to the reference point P ₀ side, as shown in FIG.
As shown in, the position of the object to be measured W contacts the reference point P ₀ . At this time, in the data processing circuit in the display device 30, the slide of the movable target prism 14 in the reverse direction (to the right) is processed as the subtraction value ΔL, and the subtraction value ΔL is subtracted from the distance display La. Distance La- △
L = Lb is displayed.

In the above-described embodiment, the laser oscillator 12 is directly fixed to the pedestal 11, but the laser oscillator 12 mounted on a table different from the pedestal 11 is used.
The pedestal 11 may be configured so as not to be easily affected by the heat generated by the laser oscillator 12.

[0017]

As is apparent from the above description, according to the length measuring apparatus of the present invention, the pedestal expands and contracts due to the change in the temperature of the atmosphere in which the length measuring apparatus is placed, and the optical path of the measuring light is increased. Even if the length changes, the fixed prism is installed in the vicinity of the measurement reference point, so the optical path length of the reference light changes by the same amount as the optical path length of the measurement light and cancels out. Error does not appear.

Particularly, when a large number of objects having the same shape are to be measured over a long period of time, continuous measurement is performed without paying attention to temperature changes in the room where the length measuring device is placed and without performing zero adjustment one by one. Even if the measurement is performed for a long time, an accurate measurement value can be obtained. Therefore, since an accurate measurement can always be performed under any temperature atmosphere, there is an excellent effect that it can be used under a condition where the temperature changes drastically, which has been impossible in the past.

In the second aspect, the pedestal is less susceptible to the heat generated by the laser oscillator, so that the error in measurement is further reduced.

[Brief description of drawings]

FIG. 1 is a front view of an embodiment of a length measuring device according to the present invention.

FIG. 2 is an explanatory view explaining a measuring operation of the length measuring apparatus.

FIG. 3 is a front view of a conventional length measuring device.

FIG. 4 is an explanatory view explaining an operation of the length measuring device.

[Explanation of symbols]

11 mount 12 laser oscillator 14 movable target prism 16 interference beam splitter 18 mirror which is a reflection optical member 20 fixed target prism 30 indicator L ₁ measurement light L ₂ reference light

Claims (2)

[Claims] 1. A laser beam is split by a beam splitter into reference light directed to a fixed target prism and measurement light directed to a movable target prism, and the reference light reflected by the fixed target prism and the movable target prism are moved. In a length-measuring device that receives the measurement light reflected by the movable target prism and a light-receiving sensor, and measures the number of times of light and dark caused by the interference of these lights, the length-measuring device main body has a long shape. A mount, a laser oscillator that is provided at one end on the mount and emits light along the mount, a movable target prism that is assembled to the mount and can slide on the optical path of the light emitted from the laser oscillator, and a laser. Measurement light and measurement light that are provided on the optical path of the light and near the emission end of the laser light and that travel straight through the light emitted from the laser oscillator. Interference beam splitter that splits into a reference beam that is orthogonal to, a fixed target prism that is provided near the measurement reference point that is the moving start point of the movable target prism on the gantry, and the reference beam that is split by the interference beam splitter is fixed While guiding to the target prism,
A length measuring device comprising: a reflection optical member that guides light reflected by a fixed target prism to an interference beam splitter. 2. The length measuring apparatus according to claim 1, wherein the laser oscillator is provided at a position separated from the gantry so that heat generated by the laser oscillator is less likely to be transmitted to the gantry.