JP2003035513A - Laser measuring machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser measuring machine realizing a simpler and easier alignment to enhance a measurement accuracy. SOLUTION: In the machine, there is a reflection plane almost parallel with a reflection plane of a mobile mirror 18 placed opposite to through-holes 16, 17 of the measuring machine body 10, and a reflector 1 is placed on the opposite side of the mobile mirror 18 for the measuring machine body 10. Thus the machine is configured so as to accomplish its desired alignment by adjusting the reflector 1 to be parallel with the mobile mirror 18.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser interferometer and the like used for measuring a moving distance and a position of an object to be measured such as a microscope stage. Related to laser length measuring instruments. 2. Description of the Related Art Generally, a laser length measuring device irradiates an object to be measured with laser light from a laser light source such as a semiconductor laser, obtains interference light, and uses the interference light as a basis. Thus, the moving distance and the position of the measured object are measured. [0003] Fig. 3 shows such a conventional laser length measuring device.
A semiconductor laser 11 is provided corresponding to the collimator lens. The laser light emitted from the semiconductor laser is converted into parallel light by the collimator lens 12 and is incident on the polarization beam splitter 13 at the subsequent stage. The polarization beam splitter 13 divides the incident light into a P polarization component and an S polarization component, transmits the P polarization component, and reflects the S polarization component. The transmitted P-polarized light component is transmitted through a λ / 4 plate 14 whose crystal axis is inclined at 45 degrees with respect to the plane of the paper and is converted into circularly polarized light. Moving mirror 1 which passes through the exit hole 16 and is set on the object to be measured.
The light is reflected by the laser beam 8, passes through the exit hole 16 again, passes through the λ / 4 plate 14, and is guided to the polarization beam splitter 13 as S-polarized light. The S-polarized light guided to the polarizing beam splitter 13 is reflected and reflected by the corner cube prism 2.
0, is reflected again by the polarizing beam splitter 13 through the corner cube prism 20, and
The movable mirror 18 is again irradiated from the exit hole 16 provided in the length measuring device main body 10. Then, the reflected light reflected by the movable mirror 18 returns to the exit hole 17 of the length measuring device main body 10, λ /
The light passes through the polarizing beam splitter 13 via the four plates 14 and enters the interference light detector 21. Similarly, the S-polarized light component from the semiconductor laser 11 reflected by the polarization beam splitter 13 is similarly operated by the polarization operation of the λ / 4 plate 15 and the centrally symmetric reflection of the corner cube prism 20, thereby obtaining the main body of the length measuring instrument. The light is reflected twice by a reference mirror 19 fixed inside 10, is superimposed on the optical path of the movable mirror 18, and enters the interference light detector 21. Here, the interference light detector 21 generates a signal corresponding to the optical path difference between the moving mirror 18 and the reference mirror 19 based on each input light, and moves the moving mirror 18 based on the signal. The distance is measured. By the way, such a laser measuring device is
When measuring an object to be measured, alignment of a measurement system is performed by adjusting the optical axis by a user. This alignment is performed by adjusting the angle of the length measuring device main body 10 so that the light emitted from the emission hole 16 of the length measuring device main body 10 is perpendicularly incident on the movable mirror 18. A method of visually confirming that the light beam from 16 is reflected by the movable mirror 18 and returns to the exit hole 16 is adopted (see FIG. 4). As a result, the two reflected lights from the reference mirror 19 and the moving mirror 18 are superimposed on the same optical path and overlap each other.
And a signal having a high contrast, that is, a signal having a high S / N ratio is obtained in the interference light detector 21. Further, to ensure the vertical incidence of the incident light on the movable mirror 18 in this way also means to suppress the occurrence of geometric errors in the measurement system. FIG. 5 shows the state of occurrence of a geometrical error of the movable mirror 18, in which the vertical to the movable mirror 18 collapses.
When there is an incident angle θ of the laser beam to the movable mirror 18,
The moving distance of the moving mirror 18 measured by the length measuring device main body 10 with respect to the moving distance L of the true moving mirror 18 is L1. The difference between the moving distances L1 and L is a length measurement error caused by the angle of incidence on the moving mirror 18 during alignment. The amount is (1-cos θ) * as shown in FIG.
L, which is an error proportional to the measurement distance. Accordingly, it is very important to make the light perpendicularly incident on the movable mirror 18 from the viewpoint of both the contrast of the obtained signal and the reduction of error. As a technique relating to such an alignment, a method for improving the position visibility of reflected light is as follows.
Japanese Patent Application Laid-Open No. Hei 5-302825 proposes a method of improving the visibility of a positional deviation of a beam smaller than the exit hole by adding an element for generating a specific diffraction pattern to the beam at the time of alignment. When an invisible semiconductor laser is used as a light source, Japanese Patent Laid-Open No. 5-126519 proposes a method for visualizing an adjustment beam. Both of these proposals share the same idea in that the alignment is basically confirmed as a deviation at the position of the injection hole. [0013] Such a laser length measuring device, when trying to measure a short distance change of several tens of mm or less with a high resolution, is affected by environmental fluctuations such as fluctuations in measured values due to atmospheric turbulence and vibrations. In consideration of the above, it is desirable to dispose the movable mirror 18 as close to the length measuring device main body 10 as possible in order to secure the reliability of the measured value. However, the adjustment method based on the criterion of the displacement of the laser beam at the position of the exit hole of the length measuring device main body 10 as in the conventional example has a disadvantage that the accuracy of alignment is inferior. That is, when the positional deviation of the laser beam is visually determined, it is difficult to determine a small deviation, and an alignment error of about several hundred μm remains. This residual displacement occurs similarly regardless of the position of the movable mirror 18. According to this, the moving mirror 18 is several hundred meters.
If it is sufficiently far, such as from m to several meters, it is possible to make the mirror almost perpendicular to the movable mirror 18, but
If the movable mirror 18 is located at a close position, a large incident angle will remain even with the same residual displacement. For example, when the residual displacement d is 300 μm and the distance M to the movable mirror 18 and the incident angle θ are: M: 15 mm θ: 34 ′. Considering the residual error with respect to the aforementioned geometric error, an error of about 50 ppm in the length measurement distance occurs at θ: 34 ′, and it becomes difficult to perform highly accurate measurement. For this reason, in the laser length measuring device, when the distance between the length measuring device main body 10 and the movable mirror 18 is small, it is difficult to obtain sufficient alignment accuracy, and a large geometrical error occurs, resulting in a measurement. There is a problem that accuracy is reduced. In particular, in a configuration using invisible light as a light source, there is a problem that alignment itself is complicated and sufficient alignment is difficult. As described above, the conventional laser length measuring device has a problem that it is difficult to obtain a sufficient alignment and the measuring accuracy is reduced. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a laser length measuring device which is simple and can realize easy alignment and improves measurement accuracy. . According to the present invention, there is provided a laser light source, light splitting means for splitting laser light from the laser light source into reference light and measurement light, and a reference mirror for reflecting the reference light. A moving mirror installed on an object to be measured that reflects the measuring light, and optical interference that guides the reference light reflected by the reference mirror and the measuring light reflected by the moving mirror to one optical path to obtain interference light. Means, and a measuring device for measuring a moving distance of the movable mirror by an interference signal from the optical interference means, wherein the laser measuring device is installed at an angle perpendicular to the measurement light output toward the movable mirror. It is configured with a reflecting mirror. According to the above configuration, the alignment of the laser measuring device is an operation of adjusting the reflecting mirror so as to be parallel to the moving mirror attached to the object to be measured, and is affected by the installation position of the moving mirror. It is possible to obtain an adjustment index without any.
Therefore, high-precision measurement can be performed without being affected by the usage mode such as the moving range of the movable mirror. Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a laser length measuring apparatus according to an embodiment of the present invention. In FIG. 1, the same portions as those in FIGS. 3 to 5 are denoted by the same reference numerals, and description thereof will be omitted. That is, the feature of the present invention resides in that the reflecting mirror 1 for alignment is installed on the opposite surface of the length measuring device main body 10 from the laser light emitting side, in other words, on the opposite side to the movable mirror 18. . The reflecting mirror 1 is installed so as to be perpendicular to the laser beam emitted from the exit hole 16 of the length measuring device main body 10. When the reflecting mirror 1 is installed on the length measuring device main body 10, for example, the moving mirror 18 disposed at a sufficient distance from the length measuring device main body 10 is moved to the length measuring device main body 1.
The laser beam emitted from the zero exit hole 16 to the movable mirror 18 is arranged on the length measuring device main body 10 so as to be vertical.
In this arrangement state, while adjusting the reflecting mirror 1 so as to be parallel to the moving mirror 18 by using the autocollimator 2 installed so that its angle with respect to the moving mirror 18 can be checked in advance, It is attached to the surface opposite to the movable mirror 18. In the above configuration, when the length measuring device is actually used, the alignment of the length measuring device main body 10 is set on the length measuring device main body 10 with respect to the movable mirror 18 mounted on the object to be measured. The parallelism is adjusted using the parallelism as a criterion so that the reflecting mirror 1 is parallel. To determine the degree of parallelism, for example, a well-known autocollimator 2 is arranged to face the reflecting mirror 1 after being aligned with the movable mirror 18 and installed on the back of the length measuring device main body 10 by the autocollimator 2. While observing the angle of the reflecting mirror 1, the position of the reflecting mirror 1 with respect to the moving mirror 18 is adjusted for several seconds and the direction is adjusted. Thus, regardless of the position of the movable mirror 18, alignment of the length measuring device main body 10 and the movable mirror 18 can be adjusted with extremely high accuracy. As described above, according to the laser length measuring apparatus of the present embodiment, it is possible to provide the alignment index of the angle of the reflecting mirror. For example, even when the moving range of the moving mirror 18 is small, the fluctuation of the atmosphere,
Even if the movable mirror 18 is arranged close to the length measuring device main body 10 so as to cope with the influence of vibration and the like, high-precision alignment can be performed, and the occurrence of geometric errors can be suppressed. Can be promoted. Further, the present invention is not limited to the above-described embodiment, but may be, for example, as shown in FIG.
The light transmission hole 3 reaching the laser light emission side may be provided in parallel with the reflecting mirror 1 on the surface opposite to the laser light emission side where the emission holes 16 and 17 are provided. According to this, the reflecting mirror 1 of the length measuring device main body 10
Mirror 1 and moving mirror 18 through the light transmitting hole 3 from the installation side of
At the same time, it is not necessary to keep the autocollimator 2 always in a fixed position during the alignment, and even after the alignment is completed, the main body of the length measuring device is passed through the light transmitting hole 3. 10
By confirming the installation state of, it is possible to continuously secure the conditions for high-accuracy measurement. As a result, the simplification of the alignment adjustment operation is further promoted, and the precision of the alignment is promoted. Further, in the above-described embodiment, a case has been described where the semiconductor laser 11 as a laser light source is configured as an integrated type in which the semiconductor laser 11 is housed and arranged in the length measuring device main body 10. However, the present invention is not limited to this. It is also possible to arrange outside the length measuring device main body 10 and connect it to the interference system by transmission through an optical fiber, and substantially the same effect can be expected. In the embodiment using this optical fiber,
The end of the optical fiber guided into the length measuring device main body 10 functions as a laser light source. Therefore, the present invention is not limited to the above-described embodiment, and various other modifications can be made in the implementation stage without departing from the scope of the invention. Furthermore, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some components are deleted from all the components shown in the embodiment, the problem described in the section of the problem to be solved by the invention can be solved, and the effects described in the effects of the invention can be solved. Is obtained, a configuration from which this configuration requirement is deleted can be extracted as an invention. As described in detail above, according to the present invention, there is provided a laser length measuring instrument which can realize simple and easy alignment and which improves measurement accuracy. Can be.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram showing a configuration of a main part of a laser length measuring device according to an embodiment of the present invention. FIG. 2 is a configuration diagram showing a configuration of a main part of a laser length measuring device according to another embodiment of the present invention. FIG. 3 is an explanatory diagram showing a configuration for explaining a concept of length measurement of a laser length measuring device to which the present invention is applied; FIG. 4 is a configuration diagram for explaining an alignment adjustment operation of a conventional laser length measuring device. FIG. 5 is a configuration diagram shown to explain a state of occurrence of a geometric error in a state where the vertical to the movable mirror is broken. [Explanation of Signs] 1 ... Reflecting mirror 2 ... Autocollimator. 3. Light transmission hole. 10 Wavelength device body. 11 Semiconductor laser. 12 ... Collimator lens. 13 ... polarization beam splitter. 14 .lambda. / 4 plate. 15 λ / 4 plate. 16 ... injection hole. 17 ... injection hole. 18… a moving mirror. 19… Reference mirror. 20… Corner cube prism. 21 ... interference light detector

Claims (1)

Claims: 1. A laser light source, a light splitting means for splitting laser light from the laser light source into reference light and measurement light, a reference mirror for reflecting the reference light, and A movable mirror installed on the object to be reflected, light interference means for guiding the reference light reflected by the reference mirror and the measurement light reflected by the movable mirror to one optical path to obtain interference light, and the light A measuring unit for measuring a moving distance of the movable mirror based on an interference signal from an interfering unit, comprising: a reflecting mirror disposed at an angle perpendicular to the measuring light output toward the moving mirror. A laser measuring device characterized by the above-mentioned.