JP2001183178A - Diffraction grating revolving laser optical encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To clearly facilitate mounting a laser optical encoder and a diffraction grating owning to elevation of the allowable error by an optical Fourier transform degree system action and send out high quality optical signals by a high speed operation of this optical system even when unexpected relative error occurs by the grating vibration. SOLUTION: Based on a special layout system of optical elements, two lights are incident to arrive at the same point on a grating, the system survey performance greatly reduces the sensitivity to the inexactness of fixing the position between a movable grating and a stationary unit of the laser optical encoder on an optical head. This effect of reducing the sensitivity can be attained by generating an optical degree system of Fourier transformation with a combination of a focusing lens 708 with a right prism 709.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a diffraction grating rotating laser optical encoder.

[0002]

2. Description of the Related Art At present, there are two types of rotary encoders generally available, both of which comprise a light source, a light control grating, an optical receiver and the like. The first type is
This is a geometric encoder that usually uses a light emitting diode (LED) as a light source. The grating turns according to the distribution of the intensity of the dimming light,
One or more fixed covers and light sensitive devices convert the electronic signal with the last measured light intensity. The spacing between the radially distributed gratings is typically of the order of 10 microns. If more precision is required, the resolution of the encoder can be increased by the reduction grating, but the output signal caused by a considerable degree of diffraction phenomenon exceeds the receivable range and generates a miscellaneous signal.

[0003] The second type is a diffractive laser encoder. It uses a laser dipole to provide a tuned light source, and by using the phase of the diffractive radial grating controlled diffracted light on the pivot axis, forms an interference code by using an optical receiver and rearranging the diffracted light beam. The optical interference signal is converted into an electronic signal by one or several photosensors and transmitted. The spacing between the diffractive radial gratings is typically about 1-5 microns at the center of the light spot, producing diffracted light in a moderate direction. The diffracted light beam generates a signal at an appropriate position in the diffractive laser optical encoder, and does not disturb the original survey signal unlike the geometric optical encoder. Therefore, the diffractive laser optical encoder can obtain a high resolution measurement result with a smaller spacing grating.

[0004] Theoretically, the design of a linear laser optical encoder can be applied to a rotary laser optical encoder as well, provided that the radius of the flat disk on the radial grid on the rotary axis is greater than the size of the light spot.

However, if the optical design of the linear laser optical encoder is directly applied to the measurement of angular movement, the interval between the radial gratings changes along the radial direction, so that the diffraction angle changes continuously, and the diffraction angle before the diffracted light is changed. The wave (wavefront) has the phenomenon of "image scattering, image difference". Many interference codes occur when the parallaxed recovered light beams meet and interfere at the output terminal. And
This code reduces the regulation rate of the survey signal and affects the accuracy of the output signal of the rotary laser optical encoder.

[0006]

However, directly,
When the optical design of the linear laser optical encoder is applied to the measurement of angular movement, the diffraction angle changes continuously along the radial direction because the spacing of the radial grating changes along the radial direction.
The front wave (wavefront) of diffracted light is "image scatter, image difference"
Phenomenon appears. Many interference codes are generated when the parallaxed recovered light beams meet and interfere at the output terminal. This code then reduces the regulation rate of the survey signal and affects the accuracy of the output signal of the swivel laser optical encoder.

The spacing between the radial gratings used in the diffraction grating rotating laser optical encoder has a characteristic of changing linearity in the radial direction (the spacing decreases as approaching the center). Diffracted light that is generated when tunable parallel light is incident and the light source strikes the radial grating is severely dissimilar due to the diffraction effect of the different grating intervals and directions at each point within the incident light point. Is formed. If the optical system of the laser optical encoder cannot correct the terrible “image difference” generated in the above-mentioned radial grating, after the diffracted light propagates through the optical system, the angular movement that occurs at the signal detection terminal at the end, and directly The relevant signals are:
The terrible “image difference” in the diffracted light causes problems such as lowering the ratio of the generated output signals, lowering the performance of the system, reducing the ability to counter external disturbances, and difficulty adjusting the optical system. I do.

[0008] Several patents relating to the swiveling laser optical encoder are currently being granted as follows. UK Patent No. GB2185314A U.S. Pat. No. 4868385 Japanese Patent No. 61-5735 Japanese Patent No. 61-189154 Japanese Patent No. No. 61-189156, U.S. Pat. 5442172

Among them, US Pat. 5442172
Proposes a solution to the "disparity" problem of radial gratings. It corrects the "image difference" of the radial grating by designing the optical system, and raises the miscellaneous signal ratio of the output signal. In this invention, two sets of Fourier-transformed optical sub-systems cover the diffraction ratios of the two different paths to compensate for the "image difference" of the radial grating. However, due to its optical path design, the two sets of Fourier-transformed optical sub-system lenses and right-angle prisms, when accurately focused together, have the largest light difference between the two interfering light beams, ie, 4 mm. Exceed. This 4
The use of a highly tunable laser light source with an optical distance difference of mm allows an output terminal to cause interference phenomena for the first time. However, when the required system actually operates, the long-tuned light source becomes more sensitive to the fluctuation in the state of the surveying light source caused by the optical motion. Also, the optical system of the present invention uses only a single-sided optical system, and one invention requires that the distribution of the grating and the concentricity of the pivot axis be kept within a few microns.

[0010] Accordingly, an object of the present invention is to provide an optical head for a movable optical system and a laser optical encoder, in which two light beams enter and reach the same point on a grid based on a special arrangement method of optical elements. It is an object of the present invention to provide a diffraction grating turning laser optical encoder which greatly reduces the sensitivity to localization inaccuracy with the above stationary device and facilitates accurate surveying.

[0011]

According to the diffraction grating rotating laser optical encoder of the present invention, based on a special arrangement method of optical elements, two lights enter and reach the same point on the grating, and the systematic survey is performed. Performance greatly reduces sensitivity to localization inaccuracies between the moving grating and the stationary device on the optical head of the laser optical encoder. The effect of reducing the sensitivity can be achieved by creating an optical sub-system of Fourier transform, which combines a focusing lens and a right-angle prism.
By the action of the next system, the mounting of the laser optical encoder and the diffraction grating is obviously made easier by increasing the tolerance. Further, by operating this optical system at a high speed, it is possible to transmit a high-quality optical signal even when an unexpected counterpoint error occurs due to the lattice vibration.

The lens and the prism of the optical system of the Fourier transform are located on a common optical path of the two diffracted lights. For this reason, when the position shifts, a front wave (wavefront) image difference generated for two interference lights (indicating between the lens and the prism) is canceled when the two light beams are combined. As a result, there is no formation of an interference code between the two reciprocating light beams. In addition, an optical sub-system of Fourier transform is arranged on the joint optical path of the two diffracted lights to eliminate the negative effect caused by the difference in the focal length of the lens. Heretofore, for the same type of lens commonly encountered so far, the difference between the focal lengths of the different lenses is usually 10% of the standard focal length of this type of lens. If this calculation is successful, US Pat. 54421
The 72 different inventions use two sets of Fourier transform optical sub-systems to cover two different paths of diffracted light, the difference of which is 1 mm. When the two sets of Fourier transform optics and the right-angle prism are both accurately focused, the difference between the two interfering light beams is greater than 4 mm. The use of a highly tunable laser light source allows the output terminal to cause an interference phenomenon only for a light difference of 4 mm. However, when the required system of a long-tuned light source actually operates, the sensitivity of the survey light source state fluctuation caused by the optical motion becomes high.

The embodiment of the laser optical encoder of the present invention can be applied to a single point of light of the radial grating or to one point at each end of the diameter line of the radial grating. Demonstrate its effect. Regarding the design of a single light spot, the two light fluxes are focused on the same light spot on the radial grating when the parallel light flux enters and reaches the diffraction grating. Of the systems using incident parallel light, relatively large spots of light occurring on the grating make the grating less sensitive to defects. Furthermore, the front-wave (wavefront) image difference of the diffracted light caused by the change of the grating interval along the radial direction (of the radial grating) is canceled by the second-order diffraction phenomenon of the same light spot on the same grating. As a result, the front wave (wavefront) of the optical system of the Fourier transform is reversed. However, such a design is quite sensitive to the tilt of the face of the head of the laser optical encoder itself. U.S. Pat. 54421
The 72-turn type laser optical encoder has this characteristic. Therefore, this system requires that the distribution of the grating and the concentricity of the pivot axis be within a few microns. In systems employing a design in which the incident light is focused to form a light spot on the grating, a small light spot on the grating avoids a wavefront image difference. It allows the radial grating to have a relatively large eccentricity (on the order of about 100 microns). However, small spots on the grid increase the sensitivity of the system to faults of the grid. Also, the grid lines of equidistant distribution, when viewed from the eccentric point,
Produces differently sized spherical angles. Therefore, the two single light point design systems described above always have an error in the survey if the eccentric state occurs when assembling the radial grating.

On the other hand, in the bi-spot design using parallel incident light, all rays are diffracted four times by the radial grating. (The symmetry lines at both ends of the diameter line of the radial grating are each diffracted twice.) And, by employing a relatively large light spot, the system has the advantage of being less sensitive to the defects of the grating. Can be maintained. further,
The magnitudes of the inclination angle of the lattice plane of the second diffracted light point and the inclination angle of the lattice plane of the first diffracted light point are equal, and the directions are opposite.
Therefore, the magnitude of the tilt of the optical head surface of the grating (corresponding to the effect caused by the eccentricity of the grating) is naturally canceled.

This laser optical encoder sends out at least two sets of mutually orthogonal sinusoidal signals.
Therefore, in the signal analysis process, the direction in which the surveying object should move can be obtained. The bias value in the output signal can be maintained at a constant value by utilizing the function of the laser efficiency motion circuit. For this reason, a signal to be analyzed including an unexpected signal caused by a change in the laser efficiency wave, a change in the temperature, a change in the grating diffraction efficiency, and the like can obtain a highly accurate survey result. In addition, the differential quadrature signal generated by adding an optical element or optical probe can automatically cancel the DC bias value of the output signal, thereby increasing the range over which the output signal operates. It is. If the position of the optical element is slightly adjusted to increase the single impulse index code on the surface of the grating, it is possible to obtain an index impulse signal out of a constant in the output signal of the laser optical encoder. The optical element that generates the index impulse signal is not described in detail because it does not affect the basic design of the laser optical encoder output quadrature signal.

[0016]

FIG. 2 shows an embodiment of a diffraction grating rotating laser optical encoder according to the present invention.
Laser dipole 701 emits polarized light in a 45 degree direction. The light intensity is equally distributed in the p-polarization state and the s-polarization state. After that, this light beam becomes parallel light through the lens 702 and proceeds toward the polarized spectral lens 703. Among them, the p-polarized light beam passes through the polarized spectral lens 703 and goes to the reflecting lens 704, and the s-polarized light beam is reflected by the polarized spectral lens 703 and then travels toward the reflecting lens 705. The two light beams pass through quarter wave plates 719 and 720, respectively, and reach the same light spot 718 on the reflection type diffraction grating 706. The grating lines of the reflection type diffraction grating 706 are distributed at equal intervals outward from the center of the rotation in the radial direction.

The incident angle of the two light beams and the interval between the gratings are all specially designed, and the +1 step diffracted light of one incident angle and the -1 step diffracted light of the other incident light are used. Is substantially perpendicular to the grating plane. The distance between the radial gratings 706 varies along the radial direction. Therefore, the diffracted light generated when large or small parallel light having a certain light spot hits the grating has a large difference from the front wave (wavefront). In the embodiment of the present invention, when these two diffracted lights reach the front of the right-angle prism 709, they first pass through the lens 708. Grating 706, lens 708 and right angle prism 709
Between the grid 706 at the front focus of the lens 708
This is the distance between the upper light spot 718 and the right-angle edge lens of the right-angle prism 709 at the back focus of 708. Right angle prism 7
09 is parallel to the lattice plane, and the light spot 71 on the lattice
8 is perpendicular to the direction of certain radial grid lines. As the diffracted light passes through the spherical lens 708, the image-distorted front wave (wavefront) that occurs at light spot 718 is transformed by Fourier transformation. Further, the light beam is transmitted to the right-angle prism 7.
After passing through 09, the front wave (wavefront)
The light beam is turned upside down,
8 and reaches a light spot 718 on the grating. Light spot 718
Go through two Fourier transformations,
The reflection effect and the overturning effect caused by the right-angle prism 709 produce the same effect as the conjugate front wave (wavefront) of the image of the light spot 718. Then, the light beam is changed to the right angle prism 70.
A thin film is formed on the right-angle prism 709 so that a polarization state can be maintained in the same manner as when the light is hit on the plane reflection lens through the light source 9, or a “corrugated plate” having the exact amount of delay and direction is provided in front of the right-angle prism 709. It needs to be covered.

The light beam reflected by the right-angle prism 709 is converted by Fourier transformation by the lens 708, and further enters the same light spot 718 on the grating 706.
From the second-order diffracted light generated from the light spot 718, the light enters the reflection lenses 704 and 705 in a direction opposite to the original optical path. 2 with respect to the front wave (wavefront) by lens 708
A Fourier transformation of degrees is performed and the right angle prism 709 swaps the top and bottom of the front wave (wavefront) so that the ray bundle returns to the position of the front wave (wavefront) before the light spot 718 on the grating 706. . This is just like mathematically the first order diffracted light has just left the light spot 718 on the grating 706 and the front wave (wavefront) forms a “multiple conjugate” effect. Therefore, the second-order diffracted light that has passed through the same light spot 718 on the grating 706 is collimated again. This means that the lens 70
8 and the total effect of the right angle prism 709. In fact, this is equivalent to placing it over light spot 718 of right angle prism 706. The direction indicated by the right-angled ridge is along the radial direction of the radial grating 706. Thus, this fictitious right-angle prism is considered similar to the Fourier transform of the original right-angle prism 709.

The two reciprocating light beams are reflected and returned to the polarized spectral lens 703, where they are combined and interfere with each other. Quarter wave plates 719 and 720 change their polarization in orthogonal directions. Of the original light beam, the polarized spectral lens 70
The reciprocating light having the p-polarization amount of 3 is converted to the s-polarization state. The light is reflected by the polarization spectral lens 703. Of the original light beam, the s-polarized light component reflected by the polarized spectral lens 703 passes through the polarized spectral lens 703 as the p-polarized light reciprocates. Therefore, of the two light beams, one diffracts twice in the +1 step and the other diffracts twice in the -1 step. Therefore, the movement of the grating causes the phase of the two diffracted lights to change in different directions. It should be noted that some light bundles (reflected by the grating 706 and then through the lens 708 to the right-angle prism 709)
(And diffracted along the original traveling optical path of the other light beams) is a point passing through the polarized spectral lens 703 and returning to the laser source 701. The phase is
6 does not change. However,
This part of the light beam causes the laser source 701 to change the light source state and other noise signals. In order to avoid such a situation from occurring, it is possible to use the particularity of certain optical elements so that the light beam does not return directly to the laser source 701.

After the two reciprocating light beams are combined by the polarization spectroscopy lens 703, they pass through the quarter wave plate 710, and divide the polarization state into left-handed and right-handed circularly polarized light. The two orthogonal circularly polarized lights having the same intensity become one linearly polarized light, and after being combined into one, the polarization direction of the light beam is determined by the phase difference caused by the motion regulation of the two diffracted lights through the grating 706. Decided. Some of the merged light beams are reflected by the unpolarized spectroscopy lens 711 and reach the photometer 712. By measuring the intensity of the light with the photometer 712, the laser efficiency can be controlled. The remaining merged light beam passes through the non-polarizing
The light enters the 0% non-polarized spectral lens 713. Then, the portion reflected through the spectral lens 713 passes through the polarizing plate 714 and reaches the photometer 716. Also, the spectral lens 7
The portion that has passed through 13 passes through the polarizing plate 715 and reaches the photosensitizer 717. Since the polarization axes of the polarizing plates 714 and 715 indicate the arrangement phase difference of 45 degrees, the photosensitizers 716 and 717 are provided.
Sends out two sets of sine wave quadrature signals with a phase difference of 90 degrees, decodes the signals and then displaces the grid. Further, the degree of analysis of the displacement measurement results reaches 1 to 10 nanometers (nm).
Within the system, a lens 708 and a right angle prism 709
Are arranged on a coaxial optical path of two diffracted lights. Tolerances that occur during the manufacturing process can occur on both surfaces of the lens and prism. Thus, this tolerance is equal to the difference between the images created by the two reciprocating light beams. For this reason, when the two light beams are combined and interfere with each other, they have the effect of canceling each other out, so that no extra interference code is generated. Thus, in this embodiment, the system performs well, even if the tolerances during assembly are not too tight. In the embodiment of FIG. 1, since it is important that the position between the radial grating 706 and the optical head is accurate, the grating will depend on how the minimal swivel angle is located in that plane and the strength of the transmitted signal The size is greatly reduced. Then, depending on the orientation of the optical head with respect to the radial grating 706, a deviation in position on the grating occurs. The problem of the inclination on the plane is such that when the two reciprocating light beams of the second order diffracted light pass through the polarized light spectroscopy lens 703 and then join together, they are inclined to each other. Due to this phenomenon of tilting each other, when the optical path difference becomes larger than half the wavelength, the resulting interference code greatly reduces the amount of adjustment of the signal to be sent.

FIG. 2 shows another embodiment of the present invention. The optical system is almost the same as that shown in FIG. However, in FIG. 1, the optical system of the Fourier transform including the lens 708 and the right-angle prism 709 could be substituted, but in the system of FIG. 2, one right-angle prism 709a has completely replaced it. Assuming that the incidence of the two light beams on the grating 706 is not disturbed, the position of the prism 709a is brought as close as possible to the light spot 718 of the radial grating 706. The right-angled edge of the right-angle prism 709a is the same as the emission direction of the light spot on the light spot 718. Since the right-angled edge of the right-angle prism 709a and the radial grating 706 maintain a certain distance, the light spot 718 reciprocates from the right-angle prism 709a.
, And the first-order diffracted light beam from the light point 718 does not generate a plurality of conjugate front waves (wavefronts). Therefore, the last reciprocating light beam does not become parallel light after second-order diffraction through the radial grating 706. However, the right angle prism 709a in the joint optical path of the two light beams has the same image difference as the two reciprocating light beams. Therefore, the two reciprocating light beams are reflected by the polarized spectral lens 70.
At 3, at the second encounter, there can be no interfering code between the two reciprocating light bundles caused by the light difference.

FIG. 3 shows a first example in which the rotary type laser optical encoder of the present invention is adopted and implemented. All the symmetrical ends of the diameter line of the grating 706 have diffraction optical paths as shown in FIG. As can be seen from the front view of FIG. 3, the parallel laser light is
, And then the reflection lens 704 or 70
5 is incident on light spot 718 on radial grating 706 and diffracted. Thereafter, the diffracted light beam passes through the lens 708 and is reflected by the right-angle prism 709, passes through the prism 708, and is incident again on the same light spot 718 on the radial grating 706. Again, second order diffraction occurs due to radial grating 706. After the second-order diffraction, the two light beams become parallel light again, and the reflection lens 7
04 or 705, and reciprocates with the polarized spectral lens 703.

At this time, the two reciprocating light beams do not travel toward the optical signal receiving system as shown in FIG. 1 after being merged by the polarization spectral lens 703. After passing through the focusing lens 730, the light passes through the quarter wave plate 731 and is focused on the reflection lens 732. As shown in the rear view of FIG. 3, the focused light beam is reflected, passes through the quarter wave plate 731, is incident on the polarized spectral lens 703, and passes through the lens 730. Then, the light beam becomes parallel light again. However, this ray bundle passes through a similar optical path, is split through the polarization splitting lens 703 ', and is reflected by the reflecting lens 704' or 705 '.
Light spot 718 ′ on radial grating 706 is located at light spot 718 at the symmetric end of the diameter line. The diffracted light generated by the diffraction grating passes through the lens 708 ', is reflected by the right-angle prism 709', and passes through the lens 708 'twice before being incident on the same light spot 718' on the grating 706. Produces second order diffraction. After being diffracted twice by the grating 706, the two light beams become parallel light again, and reciprocate with the polarized spectral lens 703 'via the reflecting lens 704' or 705 '. The two reciprocating light beams (the phase of which is controlled by the rotation angle of the radial grating 706) are merged at the position of the polarizing spectral lens 703 'and interfere with each other. Thereafter, the light enters the optical signal receiving device and sends out the electronic signal.

The next system consisting of the lens 730 and the reflecting lens 732 actually corresponds to a cubic reflecting lens at the corner of the center vertex of the radial grating 706. By the action of this next system, the light beam diffracted by the first light spot 718 on the grating 706 reciprocates between the second light spot 718 ′ in a parallel direction. At this time, the two light beams diffracted from the light spot 718 have the light spot 718 ′ regardless of whether the surface of the grating is deviated or whether the optical head is tilted depending on the direction of the optical head relative to the grating. The reciprocating ray bundles that have reached are not tilted. Further, a quarter wave plate 73
1 rotates the polarization states of two mutually orthogonal linearly polarized incident lights by 90 degrees. This rotation effect of the polarization state
The + 1-step diffracted light generated at the light spot 718 is surely
After reaching 8 ′, the light is further advanced along the optical path of the + 1-step diffracted light, and the −1-step diffracted light generated at the light point 718 reaches the light point 718 ′, and then the −1-step diffracted light Along the light path of The inclination of the surface of the grating, or the orientation of the optical head with which the grating is opposite, causes a relative inclination between the light beams after the third and fourth order diffractions are performed at the light spot 718 '. Let it. However, the opposite inclination generated by the latter two diffraction phenomena has the same effect value as the inclination generated by the previous two diffraction phenomena, and the directions are opposite. Therefore, when the two reciprocating light beams meet at the output terminal, the relative angle does not tilt. Therefore, when the two reciprocating light beams finally interfere with each other after passing through the polarized spectral lens 703 ', no extraordinary interference code is generated. The two light spots designed in this example have the property of diffracting 4 degrees, which not only greatly reduces the sensitivity of the system to correctly coping with the grating, but also makes the relatively large light Laser light incident on the grating from a point also has the effect of reducing the sensitivity of system grating defects.

FIG. 4 shows a second example in which the rotary type laser optical encoder according to the present invention is adopted and implemented. The lenses 708, 708 'of FIG.
9, 709 ', except that the two lens and prism system is replaced by the next system consisting of lens 708b and right angle prism 709b.
Is the same as that shown in FIG. The center points of the lens 708b and the right angle prism 709b in FIG. 4 correspond exactly to the center axis of the radial grating 706. The front focus of the lens 708b is on the center of the grating plane of the grating 706. The right angle ridge angle of right angle prism 709b is at the back focal point of lens 708b and is perpendicular to the diameter line having light spots 718 and 718 'at both ends. The size of the lens 708b and the right-angle prism 709b must be sufficient to receive the ray bundles emanating from the light spots 718 and 718 '. This design requires a lens with a relatively large numerical aperture. In addition, as the focal length becomes longer, the altitude of the optical head relatively increases. In this design, the next system of lenses and prisms replaces the next system of two lenses and prisms corresponding to the light reaching light point 718 and the light diffracted from 718 in the original design, respectively. Thus, in terms of the two diffracted light beams, the optical element is caused by the inaccuracy of the corresponding position,
This is the same as the amount of image difference of the front wave (wavefront). Then, by canceling each other, there is no possibility that an unnecessary interference code generated by bending the front wave (wavefront) is generated.

FIG. 5 shows a third example in which the rotary type laser optical encoder of the present invention is adopted and implemented. Except for the fact that the next system consisting of the lens 708b and the right-angle prism 709b in FIG. 4 uses a right-angle prism 709c (the right-angle edge of which is parallel to the diameter line with the light points 718 and 718 'at both ends), other designs are the same. All are the same as those shown in FIG. Assuming that the ray bundle does not impede the incidence on the radial grating 706, the right-angle prism 709c
Is as close as possible to the grid. This design eliminates the lens 708b so that the light beam does not produce a collimated round trip light beam after undergoing second and fourth order diffraction through the diffraction grating. However, the prism 709c
Are all located on the common optical path of the ray bundle,
The front wave (wavefront) caused by the round-trip light beam of the book
Are equal. Therefore, no extra interference code is generated.

FIG. 6 shows a fourth example in which the rotary type laser optical encoder of the present invention is adopted and implemented. The lens 730 and the reflection lens 73 shown in FIGS.
The following system of the fictitious-angle cubic reflecting lens composed of 2 is a true-angle cubic reflecting lens 732 ′ (a polarized spectral lens 70).
Other designs are the same as shown in FIGS. 3 to 5, except that they are replaced by S.3 and 703 '). In FIG. 6, the quarter wave plate 731 is in front of the corner cube reflection lens 732 '. The corner cube reflection lens 732 ′ must be large enough to receive the light beam incident from the polarization splitting lens 730. Then, this light beam must be reflected by the polarized spectral lens 730 '. This design not only simplifies the correspondence of the position at the time of assembling the system, but also ensures that the reflected directions of the two diffracted lights are the same as the direction at the time of incidence by adopting the cube-shaped reflecting lens 732 ′. Be parallel. However, since the vertex of the cube reflection lens 732 ′ cannot be located at the center of the rotation of the grid 706, the inclination of the plane of the grid,
Alternatively, the inclination of the direction causes the two opposite diffracted light beams to be inclined. That is, an inclination between the two light beams is generated at the light spot 718 '.

FIG. 7 shows a fifth example in which the swiveling laser optical encoder of the present invention is adopted and implemented. Other designs, except that two parallel prisms 733 and 733 'have been added to reduce the distance between the ray bundles incident on points 718 and 718' and the rays diffracted from points 718 and 718 '. Are all the same as those shown in FIG. Designed to reduce the distance between all light bundles, it not only makes it easier to find lenses 708b and 730 with large numerical apertures, but also integrates the original two-layer optical element to simplify assembly and reduce production costs. It became possible to lower. In addition, all the optical elements are arranged on the joint optical path of the two diffracted lights,
Even if the optical element does not correspond to the correct position, the two diffracted lights do not generate the same amount of front wave (wavefront) image difference, and there is no significant interference code between them. .

FIG. 8 shows a sixth example in which the rotary type laser optical encoder of the present invention is adopted and implemented. Includes two focusing lenses 741 and 742 on the optical path to collect the incident light at the light spot 718 of the grating 706 and replace the right-angle prism 709 with the angular cubic reflecting lens 743 for other The design is the same as that shown in FIG. As the incident light is collected on the grating 706, the distance between the radial gratings is changed, and the occurrence of the image difference phenomenon can be suppressed. Then, as a result of reducing this image difference, the system becomes more tolerant to the inclination of the plane of the grating or the inclination of the orientation. However, when the beam bundle is focused on the small spots formed on the grating 706, the system becomes extremely sensitive to the shortcomings of the grating. To solve the grid problem, two orientation lenses 7
Adjusting the positions of 41 and 742 can cause a slight defocusing phenomenon, slightly increase the size of the light spots on the grid, and make the system less sensitive to grid imperfections. The front wave (wavefront) image difference generated by the defocusing of the lenses 741 and 742 is adjusted by the lens 708 for adjusting the center.
Adjust by Therefore, when the two diffracted lights finally return to the optical signal receiving device, the state of the collimated light beam can be maintained.

FIG. 9 shows a seventh example in which the rotary type laser optical encoder of the present invention is adopted and implemented. This is obtained by adding some tonality to the arrangement method of the embodiment shown in FIG. In this design, quarter wave plates 719 and 720 of FIG. 8 are replaced by quarter wave plates 744. The quarter wave plate 744 is disposed just in front of the corner cube reflecting lens 743 or the lens 708. Other designs are the same as those shown in FIG.

FIG. 10 shows an embodiment of an optical signal receiving apparatus of a rotary type laser optical encoder having a laser efficiency regulation function. As shown in the figure, the two reciprocating light beams pass through a quarter wave plate 710 and then change into right and left circularly polarized light that are orthogonal to each other. The relative phase of the two round-trip light beams is adjusted by the movement of the grating 706. Therefore, when two circularly polarized light beams having the same intensity and orthogonal to each other become one linearly polarized light beam, the polarization directions are as follows:
It is determined by the phase difference between the two reciprocating light beams. After the two reciprocating light beams are merged, a part of the light beam is reflected by the non-polarizing spectroscopic lens 711 and reaches the photosensitizer 712, and the laser efficiency is measured by using the light intensity measurement. Control. The other parts are the non-polarized spectral lens 71
1 and enters the 50% non-polarized spectroscopic lens 713. Thereafter, the light beam reflected by the spectral lens 713 passes through the polarizing plate 714 and reaches the photosensitizer 716. Then, the light beam that has passed through the spectral lens 713 reaches the photosensitizer 717 through the polarizing plate 715. Among them, the polarizing plates 714 and 715 are arranged at positions where the difference from the polarization axis is 45 degrees. Thus, photometers 716 and 71
Numeral 7 indicates the state of displacement of the lattice by a quadrature signal consisting of a sine wave function with a difference of 90 degrees between the two sets.

FIG. 11 shows an embodiment of an optical signal receiving apparatus of a revolving laser optical encoder for transmitting a differential orthogonal signal. Comparing with the design of FIG. 10, it can be seen that the spectral lens 711 and the optical probe 712 have already been removed in FIG. If the efficiency of the laser dipole is not controlled by another sensitivity meter rule, drive is applied directly with a constant current. In addition, it is also possible to increase the number of optical elements and optical probes in an optical system in order to generate a difference between orthogonal signals. Under this optical structure, any set of transmitted signals consists of two sinusoidal functions. The phases of the two sine wave signals are opposite, but the DC pressure values are equal. Thus, when the transmitted signal passes through the differential expander, its DC bias value is canceled. As shown in FIG. 11, after passing through the quarter wave plate 710, the combined reciprocating ray bundle is equally divided by the 50% non-polarized spectral lens 720. One of the light beams is transmitted to the spectral lens 72.
The light is reflected by 0 to reach the 50% non-polarized spectral lens 722. The half ray bundle reflected by the spectral lens 722 passes through the polarizing plate 726 and reaches the optical detector 729. Then, after passing directly through the spectroscopic lens 722, the half light flux reaches the optical detector 728 via the polarizing plate 724. The polarizing plates 724 and 726 have a phase difference 9 indicated by their polarization axes.
By being arranged at the position of 0 degrees, the optical detectors 728 and 72
Although the signal sent by 9 has conflicting characteristics,
Since the sinusoidal signal generated by the lattice displacement control has an opposite polarization state, the signals sent from the optical detectors 728 and 729 are reduced to each other, and then a sinusoidal signal from which the polarization value is removed is obtained. Can be. Also, directly
After passing through the spectroscopic lens 720, the half ray bundle is 50
The light beam travels toward the% non-polarized spectroscopic lens 735, and through the spectroscopic lens 735, half of the light flux is reflected, passes through the polarizing plate 736, and reaches the optical detector 739. The other half of the transmitted light flux passes through the polarizing plate 734 and reaches the optical probe 738. The polarizing plates 734 and 736 are arranged at a position having a phase difference of 90 degrees indicated by their polarization axes,
The signals sent by the optical detectors 738 and 739 have the same bias pressure value, but the sinusoidal signal generated by the lattice displacement control has opposite characteristics.
After the signals sent out by 8 and 739 are reduced each other, a sine wave signal from which the pressure value is removed can be obtained. Since there is a difference of 45 degrees between the directions indicated by the polarizing plates 724 and 726 and the polarizing plates 734 and 736, the optical probes 728 and 7
The displacement of the non-polarized pressure signal sent out by the
There is a difference of 90 degrees from that sent by 38 and 739. In addition to FIGS. 1-11 using a reflective diffraction grating 706, the system can also employ a transmission diffraction grating. The transmission type diffraction grating and the reflection type generally include a grating having a radial distribution. However, not all the diffracted light passes through the grating uniformly and is not reflected back to the light source. Thus, when utilizing a transmission grating, it receives first and third order diffracted light, eg, lenses 708, 708 'and 708
b, right angle prisms 709, 709 ', 709a, 709
b, 709c and the cubic reflective lens 74 at the corner
Optical elements such as 3 must all be moved to the other side of the radial grating.

Except for the above-mentioned embodiments (the ones shown in FIGS. 1 to 11 and the situation where a transmission type grating is adopted), based on the present invention, these embodiments are all different examples again. It is possible to assemble. The optical path of the incident light between the polarized spectral lens 703 and the light spot 718 and the optical path of the reciprocating light between the polarized spectral lens 703 'and the light spot 718' can be overlapped, and the entire system can be overlapped. Can be reduced in volume. Further, the two can be separated from each other to avoid interference caused by unnecessary reflected light sent out and mode conversion of the laser light source.

The various embodiments and the alternative embodiments described above do not limit the scope of the present invention. All other forms or minor changes relating to the present invention are also within the scope of the present invention.

[0035]

The measurement using the diffraction grating rotating laser optical encoder according to the present invention has high accuracy and helps to reduce the cost.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a swiveling laser optical encoder designed based on the present invention.

FIG. 2 shows another embodiment of a swiveling laser optical encoder designed based on the present invention.

FIGS. 3A and 3B show a first embodiment employing a rotary laser optical encoder of the present invention, wherein FIG. 3A is a left side view, FIG. 3B is a front view, and FIG. It is.

FIGS. 4A and 4B show a second embodiment employing the rotary laser optical encoder of the present invention, wherein FIG. 4A is a left side view, FIG. 4B is a front view, and FIG. It is.

5A and 5B show a third embodiment employing the rotary laser optical encoder of the present invention, wherein FIG. 5A is a left side view, FIG. 5B is a front view, and FIG. 5C is a right side view. It is.

FIGS. 6A and 6B are a left side view, FIG. 6B is a front view, and FIG. 6C is a right side view of a fourth embodiment employing the swiveling laser optical encoder of the present invention. It is.

FIG. 7 is a fifth embodiment employing the rotary laser optical encoder of the present invention, wherein (A) is a left side view, (B) is a front view, and (C) is a right side view. It is.

FIG. 8 is a diagram showing a sixth embodiment employing a swiveling laser optical encoder designed on the basis of the present invention.

FIG. 9 is a view showing a seventh embodiment employing a swiveling laser optical encoder designed based on the present invention.

FIG. 10 is a diagram showing an embodiment of a sub-system of an optical signal receiving device of a rotary type laser optical encoder having a laser source efficiency control action based on the present invention.

FIG. 11 is a diagram showing an embodiment of a sub-system of an optical signal receiving device of a revolving laser optical encoder capable of sending out a differential orthogonal signal based on the present invention.

[Explanation of symbols]

 701 Laser Dipole 702 Lens 703, 703 'Polarized Spectral Lens 704, 705 Reflective Lens 704', 705 'Reflective Lens 706 Reflective Diffraction Grating 708, 708', 708b Lens 709, 709 'Right Angle Prism 709b, 709c Right Angle Prism 710 1/4 wave plate 711 Non-polarized spectral lens 712 Photosensitizer 713 Non-polarized spectral lens 714, 715 Polarizing plate 716, 717 Photosensitizer 718, 718 'Light point 719, 720 1/4 wave Plates 719 ′, 720 ′ Quarter wave plate 722 Non-polarized spectroscopic lens 724 Polarizer 726 Polarizer 728, 729 Optical probe 730 Focusing lens 731 Quarter wave plate 732 Lens 733, 733 ′ Prism 734, 736 Polarizing plate 735 Non-polarized spectral lens 738, 739 Optical probe 741, 74 Atsumariase lens 743 square cube reflective lens 744 4 minutes a wave plate

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F065 AA02 AA09 BB02 BB03 BB16 BB25 BB29 DD03 DD04 FF48 GG04 GG12 HH04 HH12 JJ01 JJ08 LL04 LL10 LL12 LL32 LL36 LL46 MM04 PP13 QQ28 UU07 FE12 BA37 EC01 EC12 EC13 EC14

Claims (51)

[Claims] 1. A diffraction grating which measures displacement by sticking to a revolving object and an incident light point to generate a first and a second light flux and directly hit on the diffraction grating. A ray bundle system which is the generated diffracted light, an optical sub-system of the Fourier transform on the joint optical path of the first-stage positive and negative diffracted light generated in the diffraction grating, and an interference signal generated by the second-order diffracted light of the diffraction grating. And a signal receiving optical element to be probed by two light beams incident from different directions. The same light spot on the diffraction grating or the two When the light reaches the light spot and the angle between the two incident directions and the normal direction of the plane of the grating is almost equal to the positive and negative first-stage diffraction angles of the grating, the incident light is projected and the diffraction generated on the diffraction grating The light beam forms an interference code, Diffraction grating turning laser Opti Cal encoder utilizing the conversion of stem photoelectric signal, characterized that it is possible to know the amount of displacement of the diffraction grating. 2. A light source that emits one approximate linearly polarized tuning light, a light beam generated from the light source, a parallel lens receiving the converted parallel light beam, and a parallel light beam. 2. A diffraction grating swirling laser optical encoder according to claim 1, further comprising a surveying light beam bundle system comprising a polarizing spectral lens which converts two polarization states into linearly polarized lights perpendicular to each other. 3. The optical system according to claim 2, wherein the two incident lights are on a common optical path after passing through the diffraction grating, and have an optical sub-system of a Fourier transform comprising one lens and one right-angle prism. The diffraction grating laser optical encoder according to claim 1. 4. A Fourier transform which is located between the light spots on the diffraction grating or in the center of the two light spots on the diffraction grating to keep the two reciprocating light beams parallel to each other. 4. A diffraction grating rotating laser optical encoder according to claim 3, wherein the optical axis has a right-angled edge of an optical sub-system. 5. The diffraction grating swiveling laser optical encoder according to claim 3, wherein the optical system of the Fourier transform is replaced by a right-angle prism rotating at 90 degrees. 6. A diffraction grating swivel according to claim 1, wherein the number of spherical lenses is increased, the incident light is collected on a grating, and the optical sub-system of the Fourier transform is replaced by an angular cubic reflecting lens. Laser optical encoder. 7. A reflection type diffraction grating is employed, and an optical sub-system of Fourier transform is disposed at an intermediate point between light spots on the diffraction grating or at a center of two light spots on the diffraction grating. 2. A diffraction grating rotating laser optical encoder according to claim 1, further comprising a diffraction grating for surely keeping the two reciprocating light beams parallel. 8. A reflection type diffraction grating which employs a transmission type diffraction grating, is composed of a lens and a prism of an optical sub-system of a Fourier transform, and is replaced on the other side of the grating which is not on the same side as other optical elements. 8. A diffraction grating rotation laser optical encoder according to claim 7, wherein: 9. The diffraction grating swivel laser optical encoder according to claim 8, further comprising a diffraction grating which is a flat radial grating stuck on the swivel object and measures a swivel displacement of the article. 10. A diffraction grating rotating laser optical encoder according to claim 7, further comprising a diffraction grating which is a flat radial grating attached to the rotating object and measures a rotating displacement of the article. 11. A reflection type diffraction grating, wherein a right-angle prism rotating by 90 degrees is placed at an intermediate position between light spots on the diffraction grating.
2. A diffraction grating rotating laser according to claim 1, further comprising a diffraction grating disposed at the center of the two light spots on the diffraction grating to surely keep two reciprocating light beams parallel. Optical encoder. 12. A transmissive diffraction grating, wherein the right-angle prism is not on the same side as the other optical elements of the grating.
12. The method according to claim 11, wherein the other side is replaced.
A diffraction grating rotating laser optical encoder as described. 13. A diffraction grating rotating laser optical encoder according to claim 12, further comprising a diffraction grating which is a flat radial grating attached to the rotating object and measures a rotating displacement of the object. 14. The diffraction grating rotating laser optical encoder according to claim 11, further comprising a diffraction grating which is a flat radial grating attached to the rotating object and measures a rotating displacement of the object. 15. In a reflection type diffraction grating, incident light is collected on the grating by increasing the number of spherical lenses, and a cubic reflection lens having an angle is placed between the light spots on the diffraction grating or on the diffraction grating. 2. A diffraction grating rotating laser optical encoder according to claim 1, further comprising a diffraction grating which is arranged at the center of the two light spots in order to keep the reciprocating light beam parallel. 16. A diffraction grating swirling laser optical encoder according to claim 15, wherein a cubic reflecting lens having a corner is replaced with another side of a grating different from other optical elements instead of a transmission type diffraction grating. . 17. The diffraction grating swivel laser optical encoder according to claim 16, further comprising a diffraction grating which is a flat radial grating stuck on the swivel object and measures a swivel displacement of the article. 18. The diffraction grating swivel laser optical encoder according to claim 15, further comprising a diffraction grating which is a flat radial grating stuck on the swivel object and measures a swivel displacement of the article. 19. The diffraction grating rotating laser optical encoder according to claim 1, wherein no index pulse signal is generated. 20. The method according to claim 1, wherein an optical element outside the constant and an index mark on the grid can be increased to generate one or more index impulse signals.
A diffraction grating rotating laser optical encoder as described. 21. A diffraction grating rotating laser optical encoder according to claim 1, further comprising an optical element having an optical structure designed by assembling discrete optical elements. 22. The diffraction grating swirling laser optical encoder according to claim 1, further comprising an optical element having an optical structure designed by mixing and combining the discrete optical element and the stacked optical element. 23. The diffraction grating swirling laser optical encoder according to claim 22, wherein the stacked optical element can be manufactured using a semiconductor. 24. The diffraction grating rotating laser optical encoder according to claim 1, further comprising an optical element having an optical structure designed by combining the stacked optical elements. 25. The diffraction grating rotating laser optical encoder according to claim 24, further comprising a stacked optical element that can be manufactured using a semiconductor. 26. A diffraction grating for measuring displacement by sticking to a revolving object and an incident light point, and generating a first and a second light flux and directly hitting the diffraction grating. A beam bundle system that is diffracted light, and two sets of optical sub-systems of Fourier transformation, each of which is located on one end of the above-mentioned diffraction grating, and on the common optical path through which the diffracted light of the first stage of the positive / negative of the diameter symmetry point passes through the diffraction grating. And a cubic reflecting lens with a fictitious angle assembled above the diffraction grating and at a vertex on the center line of the diffraction grating, and an interference light signal generated after being diffracted by the diffraction grating A signal receiving optical system for detecting the incident light beam is provided. Two light beams incident from different directions are on the same light spot on the diffraction grating or on a slightly deflected grating using the light source. Two An angle between the two incident directions and the normal direction of the plane of the grating when the light reaches the light spot is almost equal to the positive and negative first-stage diffraction angles of the grating. Is diffracted twice at two points symmetrical to the diameter line of the radial grating. After diffracting the diffracted light beam four times, an interference code is output from the output terminal and the conversion of the system photoelectric signal is used. A diffraction grating rotating laser optical encoder characterized in that the displacement of the grating can be known. 27. A light source that emits one approximate linearly polarized tuning light, a light beam generated from the light source, and a parallel lens that receives the converted parallel light beam; 27. The diffraction grating swirling laser optical encoder according to claim 26, further comprising: a surveying beam bundle system comprising a polarization spectral lens which converts two polarization states into linearly polarized lights perpendicular to each other. 28. The two incident lights are on a common optical path after passing through the diffraction grating, and have an optical sub-system of Fourier transform including one lens and one right-angle prism, and have a fictitious angle. In the cubic reflection lens, the vertex is located on the center line of the above-mentioned diffraction grating. 27. An optical sub-system of a Fourier transform parallel to the direction of the bundle.
A diffraction grating rotating laser optical encoder as described. 29. A fourier transform optics sub-system which is located between the light spots on the diffraction grating or the center of the two light spots on the diffraction grating and ensures that the reciprocating light beam is kept parallel. 29. The diffraction grating rotating laser optical encoder according to claim 28, wherein the encoder has a right-angled edge. 30. A diffraction grating swiveling laser optical encoder according to claim 28, having a Fourier transform optical sub-system that can be replaced by a right-angle prism turning 90 degrees. 31. A diffraction grating swirling laser optical encoder according to claim 28, comprising a fictitious corner cube reflecting lens that can be replaced by using a single true corner cube reflecting lens. 32. The method according to claim 26, wherein the incident light can be collected on the grating by increasing the number of spherical lenses, and the optical sub-system of the Fourier transform can be replaced by a cubic reflecting lens having a corner. Diffraction grating rotating laser optical encoder. 33. Using a reflection type diffraction grating, the optical system of the Fourier transform is located at the center of the two light spots on the diffraction grating, and can surely keep the reciprocating light beam parallel. 27. The diffraction grating rotating laser optical encoder according to claim 26, further comprising a diffraction grating. 34. The reflection type diffraction grating is a transmission type diffraction grating, and the lens and the prism of the optical system of the Fourier transform are replaced with the other side of the grating which is not on the same side as other optical elements. 34. A diffraction grating rotating laser optical encoder according to claim 33. 35. The diffraction grating swivel laser optical encoder according to claim 34, further comprising a diffraction grating which is a flat radial grating stuck on the swivel object and measures a swivel displacement of the object. 36. The diffraction grating swivel laser optical encoder according to claim 33, further comprising a diffraction grating which is a flat radial grating stuck on the swivel object and measures a swivel displacement of the article. 37. A reflection type diffraction grating, wherein a right-angle prism rotating by 90 degrees is placed at an intermediate position between light spots on the diffraction grating.
27. A diffraction grating rotating laser according to claim 26, further comprising a diffraction grating disposed at the center of the two light spots on the diffraction grating to surely keep two reciprocating light beams parallel. Optical encoder. 38. A diffraction grating rotating laser optical encoder according to claim 37, wherein a transmission type diffraction grating is adopted, and the right-angle prism is replaced on the other side which is not the same side as other optical elements of the grating. . 39. A diffraction grating rotating laser optical encoder according to claim 38, further comprising a diffraction grating which is a flat radial grating attached to the rotating object and measures a rotating displacement of the object. 40. The diffraction grating rotating laser optical encoder according to claim 37, further comprising a diffraction grating which is a flat radial grating attached to the rotating object and measures a rotating displacement of the article. 41. In a reflection type diffraction grating, incident light is collected on a grating by increasing the number of spherical lenses, and a cubic reflection lens having an angle is placed between the light spots on the diffraction grating or on the diffraction grating. 27. A diffraction grating rotating laser optical encoder according to claim 26, further comprising a diffraction grating which is arranged at the center of the two light spots in order to keep the reciprocating light beam parallel. 42. A diffraction grating swiveling laser optical encoder according to claim 41, wherein the cubic reflection lens having a corner is replaced with another side of a grating different from other optical elements instead of a transmission type diffraction grating. . 43. A diffraction grating swiveling laser optical encoder according to claim 42, further comprising a diffraction grating which is a flat radial grating stuck on the swiveling object and measures a turning displacement of the article. 44. The diffraction grating swivel laser optical encoder according to claim 41, further comprising a diffraction grating which is a flat radial grating stuck on the swivel object and measures a swivel displacement of the article. 45. The diffraction grating rotating laser optical encoder according to claim 26, wherein no index pulse signal is generated. 46. The method according to claim 2, wherein one or more index impulse signals can be generated by increasing the number of optical elements outside the constant and the index notation on the grid.
6. A diffraction grating rotating laser optical encoder according to 6. 47. A diffraction grating rotating laser optical encoder according to claim 26, further comprising an optical element having an optical structure designed by assembling discrete optical elements. 48. The diffraction grating swirling laser optical encoder according to claim 26, further comprising an optical element having an optical structure designed by combining a discrete optical element and a stacked optical element. 49. The diffraction grating rotating laser optical encoder according to claim 48, wherein the stacked optical element can be manufactured using a semiconductor. 50. The diffraction grating swirling laser optical encoder according to claim 26, further comprising an optical element of an optical structure system formed by assembling the stacked optical element. 51. The diffraction grating rotating laser optical encoder according to claim 50, further comprising a stacked optical element that can be manufactured using a semiconductor.