TW475053B - Diffractive type laser ruler having high tolerance of grating rule phase shift and alignment error - Google Patents

Abstract

The main concept of the diffractive type laser ruler of the present invention is to use the phase information in the diffractive light of the grating to analyze the speed and position shift of the object adhered to the grating. The objective of the allocation of the optical devices of the present optical ruler is to project the light source onto the diffractive grating, and make the whole optical ruler system has high tolerance of the phase shift resulted from the grating rule and the relative alignment error between the grating ruler and laser pickup head through the relative allocation of optical devices. Since the incident light beam is focused onto the diffractive grating, the wavefront of signal light is relatively not prone to be affected by the geometrical characteristics of the diffractive grating such as nonuniform spacing or surface bending, the design of the present invention can be applied no matter in linear, radius shape or cylindrical grating, and further to obtain a very good signal visibility. Since the optical devices of the present invention is greatly simplified and the diffractive grating is thinner and smaller than the general geometrical grating, it is suitable for the positioning of minute systems.

Description

475053 V. Description of the invention α) Background of the invention (1) Types of optical encoders The optical rulers currently used in the market can generally be divided into two categories. The basic idea is to use a moving grating to modulate the optical signal and receive the modulated signal to The analysis of the speed and displacement of the grating movement is only different in the optical modulation method and the optical signal analysis processing. The first type refers to a geometrical optical ruler (as shown in Figure 1), while the second type refers to a diffractive optical ruler (as shown in Figure 2). The example shown in Figure 1 is a geometric optical ruler system based on geometric optics. The light source generally uses a light emitting diode (LED), and the grating is attached to the moving object to be measured. The relative movement between the gratings modulates the light intensity distribution and converts the obtained light intensity signals into electronic signals for processing. In the geometric optical ruler system, the grating spacing is usually selected at a level of about 10 microns, which is generally visible. Laser light is on the order of 10 times the wavelength. Since the basic resolution of a geometric system is proportional to the pitch of the grating itself, the pitch of the grating cannot be further reduced because the diffraction phenomenon will make the system noise ratio too low, so it can only be obtained by the advancement of electronic signal segmentation. Smaller resolution, which is also the main concern of today's geometric optical ruler systems. The second type of diffraction optical ruler is based on diffraction optics. As shown in Figure 2, it uses a laser diode to provide a coherent light source. After moving the diffraction grating on the object to be modulated, the incident grating is modulated. The phase change of the diffracted light is received, the diffracted light is received for interference, and is caused by one or more optical signal detectors.

Page 7 475053 V. Description of the invention (2) The light intensity signal conversion produces an advantage of the order of about 1 micron, which can generate diffraction and increase the evolution of diffractive light. Among them, light can be simply fixed by mathematics. Define an integer between Comb (X) = on the XY plane. Similarly, in other cases, the sub-signal output is near the grating surface. In the diffractive optical ruler, the grating pitch is usually maintained at about 10 times compared to the ^ geometric optical ruler system. The grating pitch is also proportional to the diffraction angle. The system resolution, as long as the = is calculated, the grating pitch can continue to be reduced, which is the resolution required, except for the electronic signal segmentation technology, which is achieved by reducing the grating pitch. The phase modulation caused by the diffracted light generated by the motion is described as follows. First, the Z axis is used as the optical axis. Since the Y direction is consistent on the grating, γ can be set to 20, and then Σ del ta (xn) , Where n is a negative infinity to a positive infinity. When | X | $ 0.5, Rect (x) = 1, and when Rect (x) = 0. Since the distribution of the reflected light field after the incidence of parallel light is close to the shape of the grating, it can be regarded as

Comb (x / a) * Rect (x / b), where a can be regarded as the distance between gratings, and 氺 represents convolution. Considering the phenomenon of far-field diffraction, it conforms to the Fraunhofer diffraction pattern. , Can use mathematical Fourier Transform (Fourier Transform) to equalize its light field, in other words,

Comb (x / a) * Rect (x / b) — ft Comb (aFx) Sinc (bFx) (1) So F x = n / a, and the diffraction light of each order can be written as U (x, t) ~ exp (j (27rFxx-wt)) If the grating moves at constant velocity V, its x can be replaced by x-V Qt. At this time, the diffraction light of each order can be expressed as

Page 8 475053 V. Explanation of the invention (3) U (x, t) ~ exp (j (2; rFx (x-V0t) -wt)) = exp (j ((27Γ Fxx-wt) + 27r FxV〇t )) When V Qt = a and η = 1, 2; r F XV Qt = 27Γ, so it can be known that when the grating moves a distance, the phase of the positive first-order diffracted light will increase by 2; Skills and techniques, 5 more 9 poles, 5 benefits, 6 specials, 2 off 7 phases, 3 orders, issued 3, 5 speeds, 7 fast 8 steps, 3 into 7, 3 technical skills Such as the year number 2 2 8 0 9 2 1 Q ^ \ No. 1 of the 1st year, 5 2 1 00 8 9 1 case of the first year \ 5 for the new number ο Ben 8 7th, No. 2 No. 8 Xu 9 Special 1 r --Η / # 8th profit 6 special 9 countries 3 English 3, 7 years 4 5 8th profit 9 special τΗ country / US number, 2 # A 3 4 00 1 ± 9 3 5th, 8 years 1 2 2

BG 7 9 0 9 LO T-Η No. / No. 2 00 1 ± 9 0 0 Λ- \ No. 5 4 No. 6 8 Years 8 2 8 9 9 9 4 1 No. No. 8 00 IX 8 4 9 9 5 9 4 IX 7/5 No. 5 3 8th, 2 years 9 6 9 9 0 9 No. 1 Lee / Special Number Bay 4 Pass 3, 7 years 0 6 0 9 5 9 LO r-i No. / No. Year ο 2 6 Case 4 4 of the first 8 2 Li 9 books 9 ο is the first view of the Li Ke Zhuan Bay, Tongkou, etc., year 8 8 4 9 0 Taiwan 6 9 ο the real rule of the British State η 光 ο sex η line a C dew (explained by the Department of Justice A good 4 series 1, 3 of 5 shown 8 shown in Figure 2 3 B G as Dilizhuan and 20% of the lens is transmissive into line 1 Flat 1 through 1 through the mirror in the light and light split the same polarization to the outgoing and incoming 1-I will shoot after the thunder and light 'will be evenly divided. For example, the implementation is

Page 9 5. Description of the invention (4) Linearly polarized light. Gan Shi, the beam reflected by the quarter- 分 = light mirror 11 1 at ^. The wave plate 41 becomes circularly polarized light and will be incident on the diffraction generated by the convergent transmission G 3 t around Λ light 乂 3 Diffraction light of a specific order will go back to the original optical path, so the beam correction / 41 5 1 and the mirror 1 4 1 are reflected first and the secondary chirped clay is reflected. Therefore, the% incident light will enter the diffraction grating 3 again to produce a quarter. Γ 波 拓 ^ The secondary diffracted light generated by the diffraction grating 3 passes through the optical mirror 1 1 ^ and enters 4 and 1 Ϊ will return to linearly polarized light '# After passing through the polarization division, this channel is circularly polarized # 合 四 \ One of the wave plates 4 2 becomes circularly polarized light. One of the wave plates 4 2 will be reflected back to the quarter by the eight-mirror mirror 1 6 1 and restored to a linear polarization knife—wave plate 4 2 , Its polarization state will be split-wave plate 5 and then reflected by the polarization beam splitter 1 1 1 to two, and its polarization direction will be two: this: the beam reflected to the half-wave plate 12 will be later, the beam will be again; H 7 wave plate 12 rotates 90 degrees; wave plate 4 5 enters the quarter light mirror 1 with the polarized beam splitter 1 12 and the circularly polarized light Two ... In the end, these two beams will be incident on the other side of the signal after they become linearly polarized light ... i. ". 2 will be incident on the other side, Ma Shui. It will be incident on the first half ^ one by the polarization beam splitter 1 1 1 After the generated transmitted light enters the wave plate 12 again and rotates 90 degrees in the axial direction, then the wave plate 4 3 is reflected by the quarter-diffraction grating 3 as the optical mirror 1 1 2 And the stomach is made of oscillating light, and then this circularly polarized light will be incident on the specific order diffraction light generated by the convergent lens 13% light ray 3, the beam mask 15 2 and the reflector 142, because

Page 10 475053 V. Description of the invention (5) This diffracted light will be incident on the diffraction grating 3 again to generate a second time. Second: The two under-diffracted light passes through the quarter wave plate 4 3--first. It will directly pass through the polarization beam splitter 1 1 2 to be incident on the four J 4 ″, #, the circular skin lens 16 generated by the quarter wave plate 4 4 2, when this circularly polarized light is reflected by the mirror 16 After 2 reflections i, the light beam is incident and returns to linearly polarized light, and -wave plate 4 5, 3 and wood polarizing beam splitter 1 1 2 are reflected to a quarter of a circularly polarized #light rear basin: the beam passes The quarter wave plate 4 5 is then converted into two beams, which are incident on the spectroscope 1 7 and are divided *, and finally, the light 1 is first beamed " so as not to pass through the polarizing plate 7 2 7 2 It will be superimposed by Ma Chuyi and # ， 2 8 2. In this case, the two secondary diffracted lights, ie, the secondary diffracted lights generated by the fringe beam, are superimposed to produce the dryness. Laser optical ruler ^ 〇 〇 over-level: system architecture diagram. & As shown in the figure, a beam of light emitted by a semiconductor laser is wound around a lens and collimated into parallel light, which is then incident on a polarization beam splitter and divided into two light beams, namely, P-polarized light and S-polarized light. Then, these two rays of light 4: Do not enter the diffraction grating from the two ends of the chirp group to generate a first-order diffraction. ^ "The incident light is incident on the reflection subsystem and is reflected back to the diffraction grating. This reflection subsystem is a GR 1 N lens. At the same time, in order to eliminate the aberration caused by grating plating, the (^^ lens On the back, except for a small part of the wire reflection layer in the middle, the rest are transparent. In other words, the secondary shape of this reflection acts as a pinhole to filter the optical phase difference. The secondary reflection is caused by the secondary reflection system. The incident light will re-enter into the group 稜鏡 and overlap each other.

475053 V. Description of the invention (6) After the polarization direction of the combined beam is received, its beam components will enter the orthogonal signals respectively. The one shown in Figure 5 is a laser optical ruler of I b Μ. As shown in the figure, after the diffraction light is generated by the diffraction grating, the first light is reflected by the lens and the mirror, and then reflected back to the diffraction grating. The diffraction grating generates a secondary diffraction grating plane, so they will coincide with each other and the displacement of the grating will make the two polarized light beams combined with the secondary diffraction light to receive the dry conversion function generated by the secondary diffraction light. An example can be obtained that can represent the one shown in the sixth figure, which is a Taiwanese network. As shown in the figure, the direction of the polarized polarization of thunder rays is 45 degrees, and the intensity is equally distributed. After this linear polarization becomes a parallel beam, it enters the polarization and the “P-polarized light directly passes through the polarization division 〇4” and is reflected to four The half-wave vibrating beam splitter 7 0 3 reflects and enters the quarter-wave plate 7 2 0; then, the influence of the four-blade one-wave plate changes to the light signal receiving diode and the output is applied to the magnetic disk servo. The laser light parallelized by the writing mechanism converges to the reflector when it enters the secondary system of the + 1st-order diffracted light and the first to first-order windings, and returns to the position of the light spot of the diffraction grating 3 mm apart. Then, this In the case of two diffracted lights, the interference fringes are generated because both of them are perpendicular to the turns; the relative phase of the diffracted light is modulated to affect the direction. Therefore, when the optical signal receiving device receives the fringes, the optical signal transmits the orthogonal signal shifted by the grating. . The light emitted by the diode 7 0 1 disclosed in Lee No. 0 9 9 2 8 3 causes the P-polarized light and S-polarized light to pass through the parallelizing lens 7 〇2 to split the spectroscope 7 0 3, The light mirror 7 0 3 is incident on the reflection mirror 7 and the plate 7 1 9 ′, and the S-polarized light is reflected by the polarization reflection mirror 7 0 5 ′ and the two passes respectively pass through a quarter wave

Page 12 475053 V. Description of the invention (7) The first beams of the plates 7 1 9 and 7 2 0 will be incident on the light spot 7 1 8 of the reflective diffraction grating 7 0 6 at the same time. Moreover, because the incident angle of the two incident lights and the distance between the diffraction gratings are specially selected so that the first + 1st order diffraction light of one of the incident light and the first first order diffraction light of the second incident light are almost perpendicular to the grating flat. At this time, the two primary diffracted lights generated by the light spot 7 丄 8 will be focused on the reflecting mirror 7 009 through the lens 708, and at this time, the diffraction grating 7 〇6, the lens 708 and the reflecting mirror The relative distance between 70 and 9 is also specially designed so that the light spot 7 1 8 on the diffraction grating 7 〇6 is located at the front focus of the lens 708, and the mirror 709 is located at the back of the lens 708. The focal point, therefore, when the above-mentioned diffracted light is focused on the mirror 7 009 and is reflected back to the lens 708, it will pass through the lens 708 and become parallel light again, and will be incident on the diffraction grating 7 〇6 again. The light spot 7 丄 8 generates secondary diffracted light. After that, the two secondary diffracted lights, after passing through the quarter-wave plates 7 119 and 7 2 0 and incident on the mirrors 704 and $ 05, will be reflected into the polarization beam splitting respectively. Mirror ^ hit people and join each other. In the optical path, the polarization directions of the quarter wave plates 7 1 q and 7? Are each rotated by 90 degrees, that is, after the original incident ρ is reduced to 90 °, the polarization beam splitter 7 will change. The ςα, 、, and 工 are reflected by the polarizing beam splitter 7 0 3, and the original incident light is returned to the polarizing beam splitter 7 0 3 when it returns to the polarizing beam splitter 7 0 3, and the polarizing beam splitter 7 0 3; In addition, because the refraction diffraction light passes: owing order ^ :: dagger, the second refraction diffraction light is in the-1st order, and the radiance 2 + system will have some luck in the first grid, which will affect the two windings. Phase modulation

V. Description of the invention (8) When the above two are combined, the combined beams of the beams are respectively diverted and the diffracted light is the phase difference between the two orthogonal and linearly polarized light. At 11:00, the feedback control by the non-optical signal detector rate will be incident on the mirror 7 1 3. The signal detector 7 will pass through the polarizing plate 7 degrees at this time to make the optical signal signal. The two groups at the back focus in this embodiment cause the corners to exist, so that the two diffracted light beams are held in the lens. After the diffracted light, such as the trajectory re-entangled beam, will become cross-diffracted light intensity linear, When the polarization is divided into 7 1 2 and the straight non-polarized reflection 16, the vibration plate 7 1 4 is out of phase with the detector. Because of this, the reflecting cube reverses the direction 8 and the obliquely diffracted light passes through the phase vertical grating 7 0 Equal polarized light This linear light mirror 7 passes through the beam splitter and passes through 15 15 7 15 7 16 9 0-degree reflecting surface mirror 7 The diffracted light of the mirror travels, either through the mirror or by rotating incidence The direction of circular polarization up to 6 quarters is taken to be polarized light 1 1 light intensity is non-polarized 7 1 3 polarized incident through polarized non-polarization and 7 1 orthogonal mirror 7 0 0 9 and the optical machine is reversed That is, 7 0 9, the two polarization split-one wave plates are squarely deflected. Depending on the composition of the dimming amount of the incident measuring beam splitter generated; vibration plate 7 and finally the direction of the beam splitter optical signal output line 7 is sinusoidal with a lens 9 7 system. After shooting, as long as the effective channel diffracting mirror 7 7 10 vibrates, its phase is equivalent to two return unpolarized reflected lights. It can be used for 7 11. The non-1 4 and 7 13 detectors are configured to represent representative signals. . Putting the light at 0 8 will ensure that two lines of light around the aperture range 0 3 are heavy, so that the two and two are two. Therefore, when the light is diffracted in a line, the beam splitter 7 will be incident on the laser for laser power. The transmitted light polarized beam splitting incident light into the transmitted light 7 17, phase difference 4 5 grating combination lens 7 0 8 the combination of the mechanism of light along the original one to protect the light, also into the light path also page 14 475053 5. Description of the invention (9) There will be no offset; it is a phenomenon of being arranged on two channels 708 and the reflecting surface, and the errors of the re-diffracted diffracted lights on the two channels are mutually different, which results in a considerable degree of error. Furthermore, since the lens 708 and the reflection light of the incident light of the reflecting mirror 7 share a common optical path, the diffraction light caused by the production error of the mirror 7 09 will cause the same amount of aberration, so when the phases coincide When interference fringes are generated, the remaining interference fringes are not allowed. Therefore, the lens can be defocused during assembly. The phase of the two productions. Summary of the invention Above the grating, it is more used than the general geometric grating. In addition, due to the relatively easy wavefront of the wavefront, the grating or cylindrical grating (visibility). When the surface of the grating is radial, the main concept of the interspersed grating optical ruler is to use the optical information to analyze the speed of the object attached to the grating and the configuration of the geometries. Diffraction grating is very small, so it is very suitable to use the internal of the micro system as the beam system to focus on the diffraction grating. The geometry of the diffraction grating is not affected by the unevenness of the grating. Both have excellent signal visibility grids that move around to their own positioning light or surface light.

When there is a change in the spacing caused by geometric factors, such as the distance increases with the radius, or the cylindrical grating cuts along the

4〇υ53 V. Description of the invention (10) Different pitches in the direction of direction will result in aberrations with varying degrees of diffracted wavefronts. The worse the difference is, it is inferred that reducing the number of surface periods covered to the extent that the grating diffraction phenomenon still exists should be an excellent strategy to achieve both, and this idea is one of the design concepts of the present invention. Since the line width of the diffraction grating used today is about 1.6 micrometers, if the laser beam of 2 mm (mm) is directly projected onto it without focusing, the period of the covered grating changes about 1200 times. If the beam is focused and projected onto the grating, the appropriate selection of the lens can make the light spot reach about 30 microns, and the grating period covered at this time; the change is about 20 times, which is i / 60 of the former, so the wavefront image The difference can be greatly reduced to improve the visibility in the optical signal and reduce the error in signal analysis. In order to repeatedly project the incident light onto the diffraction grating and synthesize the tiger beam, the present invention cleverly uses a polar pole in the design of the optical path; the combination of a soil mirror and a quarter wave plate and a reflecting surface is as much as possible Increasing the utilization rate of single + components, greatly reducing the size, cost and assembly difficulty of the optical head; compared with traditional optical rulers, reducing, complex alignment and expensive costs, the present invention has a universal application Within industrial inspection and micro systems. Continued The preferred embodiment of the present invention, as shown in Fig. 7, is the linear optical rule of the diffraction grating of the present invention.

475053 V. Description of the invention (11) The basic structure diagram, in which the emitted beam passes through the polarizer 0 2 and returns to the polarized beam splitter 0 2 and reflects through the quarter of its original incident path. At this time, a flat pole is generated due to the incident path. What the beam splitter α2 passes through directly is that a beam can enter the corner cube and it will work as expected; the wave plate 0 9 and 11 will pass through the wave plate to produce the first positive and negative. Direction, the mirror 11 that is returning to the diffraction grating for the first time should be placed on the lens to form a corner mirror. It will return to the polarized wave plate along the original light path. 12 The two beams of circularly polarized light will pass through the beam. Each beam is further polarized 稜鏡 1 7 relative to the light source 0 1 can be a laser light source or a laser diode, so the polarizing beam splitter 0 2 beams, the P polarized light penetrates the polarized wave plate 0 3, to The plane mirror 04 reflects and then reflects along the polarizing beam splitter 0.2, and the S polarized light passes through the quarter wave plate 0 5 and the corner mirror 0. The corner mirror 0 6 acts to make the S polarized light and its original shift. Misalignment, after passing through a quarter wave plate 05, it is partially transparent. The mechanism that the quarter-wave plate and the reflecting surface in the optical path rotates the polarization direction of the light by 90 degrees to control the penetration or reflection of the light mirror. In addition, the corner mirror Xia is coated with a polarization-maintaining polar coating to make the above. The parallel light emitted by the two self-polarizing beam splitters 0 2 of the optical path will be divergent and focused by the lens 0 7 to the diffraction grating 0 8 to diffract the first-order diffracted light. Here, the selection of the lens parameters needs to make the order of the diffracted light direction polar. The normal negative first-order diffracted light parallel to the grating plane passes through the lens 0 7 and the mirror 1 丄 to generate a second positive and negative first-order diffracted light, in which the optical mechanism at the back focal point is: After the second positive and negative first-order diffracting polarizing beam splitter 02 is synthesized, the quarter-polarized polarized light passing through the rear part is respectively converted into left-handed circularly polarized light and right-handed non-polarized polarized light splitter 稜鏡 13 divided into two beams of equal intensity. The polarizing beam splitter 稜鏡 1, 14 and 7 beams, of which the polarizing beam splitting prism 1 4 has a 45 degree tilt, so that

Page 17 475053 V. Description of the invention (12) The signal obtained through the back of this two-division beam produces a phase difference of 90 degrees, which is the basic source of the PQ orthogonal signal; The detectors 1, 5, 16 and 18, 19 receive the light intensity and convert them into voltage signals. After the pedestrian path is created, the voltage signals obtained by the light detectors 15 and 16 are subtracted and subtracted. Obtain a pure Q orthogonal signal. Subtract the constant part of the electro-acoustic ^^ of the photodetector 18 and 19 to eliminate the constant part. Obtain a pure P orthogonal signal. Go through step A comparison and electronic fine division to obtain a grating. The displacement vector of the object and the long return sentence. ~ Because the optical behavior of the combination of lens 0 7 and mirror 11 is actually equal to a corner mirror, the wavefront and position of the incident and reflected light will be symmetrical to the center of the corner mirror, so for gratings The aberrations caused by the relative tilt of the plane to the plane of the optical head provide an average. In the above-mentioned optical architecture, the diffraction grating 08 used can be linear, radiant, or cylindrical, so it has a wide range of applications, and due to focusing, it can largely avoid poor signal caused by wavefront aberrations. In addition, The same components are used repeatedly in the design of the optical path, making the optical head part smaller in size than other optical rulers in the world, and the adjustment process is easier. As shown in the eighth figure, another architecture diagram of the diffraction grating linear optical ruler of the present invention is different from the previous architecture in that the quarter wave plates in the previous architecture are 0.9 and 1.0. Combined into one, and the mirror 11 is directly plated on the center of the wave plate 0 9 and is still placed at the back focus of the lens 0 7 to form the optical mechanism of the corner mirror. This / architecture can make the optical element Further reduction and simplification of the system's optical adjustment procedure; In addition, it is also possible to avoid the two beams and second-order diffraction light directly reflected by the self-diffraction grating from entering the rear light detection

475053 V. Description of the invention (13) caused background noise, so the noise ratio can be greatly improved.

I11BI Page 19 475053 Brief description of the drawings Brief description of the drawings The first picture: the basic design of a typical geometric optical ruler. The second figure: system structure of a custom linear optical ruler using a reflective diffraction grating. Third figure: Linear optical rule of GB 2 1 8 5 3 1 4A. The fourth figure: a Canon's linear laser ruler (L — 104) ° The fifth figure: I B LM laser ruler applied to the writing mechanism of the disk servo. Fig. 6: One embodiment of the optical ruler disclosed in Taiwan Patent No. 0 9 2 8 3. Fig. 7: A first embodiment of a linear grating with a diffraction grating designed based on the present invention. Eighth Fig. · A second embodiment of a linear grating of a diffraction grating designed based on the present invention. Ming said # 符 件 元 1 2 ο ο Laser Diode

Page 20 475053 Brief description of the drawing 0 3 quarter wave plate 0 4 plane mirror 0 5 quarter wave plate 0 6 corner mirror 0 7 convex lens 0 8 diffraction grating 0 9 quarter wave plate 10-quarter wave plate 11 plane mirror 12 quarter wave plate 13 non-polarizing beam splitter prism 14 polarizing beam splitter 15, 16 light detector 17 polarizing beam splitter 18, 19 light detection Device

Page 21

Claims (1)

475053 _ Case No. 90117765 VI. Scope of patent application 丨 Bucha 1 · An optical automatic control encoder with a diffraction grating that is immune to uneven spacing of the grating surface and has a high tolerance for misalignment. Its composition includes at least a light source to generate a sufficient coherence length An optical ruler with a diffraction grating to detect the displacement of the object to be measured; an optical head that can split a single input beam to provide two parallel light outputs with linear polarization directions perpendicular to each other and two linear beams Parallel incident light with polarizing directions perpendicular to each other is combined into a single beam output. Due to the existence of a polarization switching mechanism in the optical path, a single input beam and a single output beam can be misaligned, so that this input and output mechanism can be applied at the same time. The light beam is divided into a first incident light and a second incident light; the first incident light and the second incident light are both linear polarized lights, and their polarization directions are perpendicular to each other; wherein the first incident light is switched by the first polarized state The mechanism switches the polar state to be perpendicular to the original polarization direction. The second incident light passes through the second polar state switching mechanism. The polarized state is also switched to be perpendicular to its original polarization direction. At this time, because the respective polarized states have been switched, the first incident light and the second incident light are parallel in space; and then the first incident light and the second incident light are parallel. After the light is converted from a linearly polarized state to a circularly polarized state, each light is focused on a diffraction grating of the optical ruler; the angle between the first incident light direction and the normal direction of the plane of the diffraction grating must be sufficiently close to the positive of the grating The first-order diffraction angle produces a positive first-order diffraction light upon incidence, and the first positive first-order diffraction light is approximately perpendicular to the plane of the diffraction grating, and the angle between the direction of the second incident light and the normal direction of the grating plane is sufficiently close The negative first-order winding of the grating is 475053 _Case No. 90117765_ YYYY_6. The patent application range of the angle of incidence produces a negative first-order diffracted light once incident, and the negative negative first-order diffracted light is approximately perpendicular to the winding. The plane of the grating; the primary positive first-order diffracted light enters the diffraction grating in the opposite direction after reflection, generating a secondary positive first-order diffracted light, which coincides with the first incident light but travels in space square The first negative first-order diffracted light enters the linear diffraction grating perpendicularly to generate the second negative first-order diffracted light, which coincides with the second incident light but travels in the opposite direction in the space; the _ After the second positive first-order diffracted light and the second negative first-order diffracted light are polarized from the circular polarized state to the linear polarized state, the second positive first-order diffracted light travels along the reverse path of the first incident light The misaligned output becomes the first output light; the second negative first-order diffracted light travels along the reverse path of the second incident light, and the misaligned output becomes the second output light. At this time, the first output light and the second output light The polarization directions are perpendicular to each other and cannot be separated in space to form a signal beam; and an optical signal precipitation system that divides the aforementioned signal beam and detects a change in light intensity; the signal beam is evenly divided into a first signal beam and a A second signal beam; and dividing the first signal beam into a first orthogonal beam and a second orthogonal beam, and detecting the first orthogonal beam and the second orthogonal beam to obtain a first orthogonal signal And the second time The first orthogonal signal and the second orthogonal signal are 180 degrees out of phase; the first orthogonal signal and the second orthogonal signal are differentiated to obtain a first orthogonal signal; The second signal beam is divided into a third orthogonal beam and a fourth orthogonal beam, and the third orthogonal beam and the fourth orthogonal beam are detected to obtain a third orthogonal signal and a fourth positive beam. Page 22 475053 _Case No. 90117765_Amendment of the month of the year_ Sixth, the patent application scope of the cross signal, the third orthogonal signal and the fourth orthogonal signal are 180 degrees out of phase; the third orthogonal signal The signal is differentiated from the fourth orthogonal signal to obtain a second orthogonal signal. The first orthogonal signal is 90 degrees out of phase with the second orthogonal signal. 2 · An optical encoder with a diffraction grating as described in item 1 of the scope of the patent application, which is immune to uneven spacing of the grating surfaces and has a high tolerance for misalignment. The light thumb can be a linear diffraction light thumb. 3 · An optical encoder with diffraction grating as described in item 1 of the scope of the patent application, which is immune to uneven spacing of the grating surfaces and has a high tolerance for misalignment. The optical ruler contains a winding The diffraction grating may be a cylindrical diffraction grating. 4 · An optical encoder with diffraction grating as described in item 1 of the scope of patent application, which is immune to uneven surface spacing and has a high tolerance for misalignment. The diffraction grating may be a radial diffraction grating. 5 · An optical encoder with diffraction grating as described in item 1 of the scope of the patent application, which is immune to uneven spacing of the grating surface and has a high tolerance for misalignment. The optical head is a component of the optical encoder. At least it contains: a polarizing beam splitter, providing a polarizing beam splitting mechanism and a reflection or transmission mechanism due to the polarization direction, < a rectangular reflection beam, providing a reflection and dislocation mechanism; a first quarter wave Plate, which cooperates with the right angle reflection to form a first deflection Page 23 475053 ____ Case No. 90117765 ________ ί —— ________________________________ Amendment VI. Patent application scope polar state switching mechanism; a first plane mirror to provide a reflection mechanism; a second quarter wave plate to cooperate with the first A plane mirror forms a second polarization switching mechanism; a convex lens is used to guide two parallel lights output from the polarizing beam splitter prism to an application system, and receive a diffraction light signal generated from the diffraction grating; a first A third quarter wave plate is placed between the first incident light beam and the convex lens to rotate the polarized light state; a fourth quarter wave plate is placed on the second The incident light is between the polarizing beam splitter and the convex lens to rotate the polarized light state; and a second plane mirror provides a reflection mechanism for the once-first-order diffraction light and the once-negative-order diffraction light, And cooperate with the third quarter-wave plate and the fourth quarter-wave plate to form a second-polarity switching mechanism and a fourth-polarity switching machine with 4``. ^ 乂 V .. ', 6 · As encountered in the first scope of patent application There is a kind of optical automatic control encoder with diffraction grating, which can be immune to the uneven spacing of the grating surface and has a high tolerance for misalignment. The optical signal extraction system includes: a quarter wave plate, The single signal light output from the optical measurement system is changed from linear polarized light to circular polarized light; a first non-polarized polarizing beam splitter splits the signal beam into a part of light to form a reference beam; a light detection Transmitter for receiving the reference beam to provide light source power modulation Page 24 475053 _Case No. 90117765__Year Month and Date__ VI. Signals required for patent application; A second non-polarized beam splitting prism that evenly divides the signal beam remaining through the light rotating beam splitting unit into a first signal A light beam and a second signal beam; a first polarizing beam splitting prism that divides the first signal beam into a first orthogonal beam and a second orthogonal beam; and a second polarizing beam splitting prism that divides the second beam The signal beam is divided into a third orthogonal beam_ and a fourth orthogonal beam. 7 · An optical automatic control encoder with a diffraction grating as described in item 5 of the scope of patent application, which is immune to uneven surface spacing and has a high tolerance for misalignment. The right-angle reflective prism can A silver-plated corner cube mirror instead. 8 · An optical automatic control encoder with diffractive grating as described in item 5 of the scope of patent application, which is immune to uneven spacing of the grating surface and has a high tolerance for misalignment, wherein the first quarter The one-wave plate and the second quarter-wave plate can be plated directly on the outside of the right-angle reflection chirp. 9 · An optical automatic control encoder with diffractive grating as described in item 5 of the scope of patent application, which is immune to uneven surface spacing and has a high tolerance for misalignment, wherein the third quarter One wave plate and the fourth quarter wave plate can be replaced by the same quarter wave plate, and the second plane mirror can be designed to be placed in the center of the wave plate to simplify the two wave plates Board and the configuration of the plane mirror. Page 25