WO2017177968A1 - 一种绝对式光栅尺 - Google Patents

一种绝对式光栅尺 Download PDF

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Publication number
WO2017177968A1
WO2017177968A1 PCT/CN2017/080590 CN2017080590W WO2017177968A1 WO 2017177968 A1 WO2017177968 A1 WO 2017177968A1 CN 2017080590 W CN2017080590 W CN 2017080590W WO 2017177968 A1 WO2017177968 A1 WO 2017177968A1
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Prior art keywords
mask
light
mask plate
grating
main grating
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PCT/CN2017/080590
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English (en)
French (fr)
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李星辉
倪凯
王欢欢
周倩
王晓浩
冒新宇
曾理江
肖翔
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清华大学深圳研究生院
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Priority to JP2018552216A priority Critical patent/JP6641650B2/ja
Publication of WO2017177968A1 publication Critical patent/WO2017177968A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/36—Forming the light into pulses
    • G01D5/38—Forming the light into pulses by diffraction gratings
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness

Definitions

  • the present invention relates to the field of measurement, and more particularly to an absolute scale.
  • the absolute grating has two code channels on the main grating.
  • One incremental code track is engraved with equal-distance raster lines for incremental displacement measurement, and the other code track is engraved with several reference points for the grating scale.
  • the absolute measurement of the grating ruler can be realized.
  • most of the grating product reading heads on the market adopt the reflection measurement method, and the obtained reference point signal is a negative pulse.
  • the signal therefore, the signal strength at the peak is often very low, then the interference of the slight external light signal will make the contrast of the signal very poor, and it is not easy to accurately locate the reference point.
  • the present invention provides an absolute scale to effectively enhance the contrast of the reference signal.
  • An absolute scale includes a main grating and a readhead component, the readhead component including an incremental displacement measuring unit, the readhead component further including a first beam splitter, a mask, and a reference position photodetection a plurality of reference code channels distributed on the main grating, and a distance between any two adjacent reference code channels is different from a distance between any two adjacent reference code channels, the first The beam splitter is configured to split the light of the light source into a light beam that is directed toward the main grating and a light beam that is directed toward the incremental displacement measuring unit, and the light beam that is directed toward the main grating passes through the mask plate to reach the main grating and is reflected.
  • the mask plate After passing through the mask again, it is received by the reference position photodetector, and the mask plate is provided with the same code channel as the reference code channel, and the position of the mask plate is set to: The light beam of the mask is not reflected by the reference position photodetector after being reflected by the mask.
  • An angle between the light beam directed to the mask and the normal of the mask is an acute angle, that is, the mask is rotated by an angle around the ⁇ x direction in FIG. 2, in parallel with the main grating. Thereby, there is an acute angle between the light beam directed to the mask and the normal to the mask.
  • the mask in the readhead is slightly rotated by a small angle about the direction perpendicular to the slit, so that the light field distribution after the beam passes through the mask is consistent with the previous one, and The light reflected back by the mask itself is deviated, is not received by the photodetector, effectively enhances the contrast of the pulse signal, and improves the discrimination accuracy of the reference position (reference code).
  • the acute angle is less than 5°.
  • a light transmitting unit and a light reflecting unit are distributed on the code track on the mask.
  • the beam size directed to the mask is greater than the width of the code track on the mask.
  • the code of the code channel is:
  • Each of the light transmitting units and each of the light reflecting units has a width of 10 ⁇ m.
  • the reference position can be aligned by using the spike of the pulse signal.
  • the peak width of the pulse signal is proportional to the line width of the code.
  • the code line width used here is 10 ⁇ m, and the obtained peak width is 26 ⁇ m, which can achieve a reference point of 0.6 ⁇ m precision. Positioning.
  • the coding is a simulation design result considering the diffraction effect.
  • the minimum slit width is 10 ⁇ m, which is much larger than the wavelength of 660 nm, the small diffraction effect can greatly weaken the sharp pulse of the reference signal, so it must be considered.
  • the effect of the diffraction effect on the beam path the first diffraction occurs after the beam passes through the mask in the readhead, and the diffraction is approximated by Fresnel diffraction, when the beam reaches the reference on the main grating.
  • the reflected light will undergo a second Fresnel diffraction.
  • the second Fresnel diffraction light field is cross-correlated with the slit structure of the mask.
  • the pulse signal waveform can be obtained for the positioning of the reference point.
  • the invention adopts the above technical solutions and has the following advantages: 1.
  • the obliquely placed mask can reflect its own light outside the photodetector, enhance the contrast of the reference signal, and improve the reference.
  • the 100-bit random coding is designed to obtain a sharp pulse signal with a tip width of 26 ⁇ m, which can achieve a reference point positioning accuracy of 0.6 ⁇ m.
  • FIG. 1 is a schematic block diagram of an absolute scale of some embodiments of the present invention.
  • Figure 2 is a partial schematic view of Figure 1;
  • 3 is an incremental code channel of a main raster and a reference code thereof according to some embodiments of the present invention
  • Figure 5 is a reference pulse signal of some embodiments of the invention.
  • an absolute scale of an embodiment includes a main grating 15 and a readhead component, the readhead component including an incremental displacement measuring unit 23 and a reference position measuring unit 22, wherein
  • the position measuring unit 22 includes a first beam splitter 12, a mask 13 and a reference position photodetector 14, on which a plurality of reference code tracks 2 are distributed.
  • the light source 11 (for example, a laser diode) emits a red laser light L0 having a wavelength of 660 nm, is collimated into a parallel beam by a collimating lens, and then passes through an aperture stop to shape the beam into a beam having a diameter of 1.2 mm, the first beam splitting.
  • the mirror (energy beam splitter) 12 splits the light of the light source 11 into two laser beams: one beam is turned 90° and then directed to the main grating 15 , and the other beam is transmitted through the first beam splitting mirror 12 to the incremental displacement measuring unit 23 for The incremental displacement of the readhead relative to the movement of the primary grating 15 is measured.
  • the light beam L1 that is incident on the main grating passes through the mask plate 13 to reach the main grating 15 and is reflected by the main grating 15 and passes through the mask plate 13 again (light beam L2) to pass through the first beam splitting.
  • the mirror 12 is received by the reference position photodetector 14.
  • the incremental displacement measuring unit 23 can be a technical solution commonly used in the prior art for measuring the incremental displacement of the readhead relative to the movement of the main grating 15.
  • the mask plate 13 is provided with a code channel corresponding to the reference code channel, and is composed of a series of light transmitting units 8 (such as a white slit in FIG. 4) and an opaque unit 7 (as shown in FIG. 4). Black line pattern) composition.
  • the incremental displacement measuring unit 23 includes an interference optical path, and the laser beam directed to the incremental displacement measuring unit 23 is further divided into two beams by the second beam splitter 16, one beam directed toward the reference grating 19, and the other beam directed
  • the -N-order diffracted light of the main grating 15 is diffracted by the beam transmitted by the mirror 20 and the second dichroic mirror 16, and the -N-order diffracted light of the reference grating forms interference fringes with the -N-order diffracted light of the main grating (for example,
  • the -1st order diffracted light of the reference grating 19 is reflected by the mirror 21 and the second beam splitter 16 and is diffracted by the beam
  • the interference fringes will change once and for all, and some light is placed in the optical path.
  • the detector 17 and the photodetector 18 are used to sense the change of the intensity of the interference fringes, and the incremental displacement of the readhead movement can be calculated by counting the number of changes in the light-dark period of the interference fringes.
  • a plurality of reference codes 2 are disposed on the main grating 15, and the rest are raster lines, that is, incremental code track 1.
  • the grating period of the equally spaced raster lines is 1 ⁇ m.
  • the grating type is a reflective holographic diffraction grating.
  • the distance between any two adjacent reference code channels 2 is different from the distance between the remaining two adjacent reference code channels, that is, the reference code channel 2 is distributed according to the distance coding design.
  • this distance encoding causes the distance between two adjacent reference codes to be a uniquely determined value.
  • the distance between two adjacent reference codes is D 0 +k ⁇
  • the distance between the other two adjacent reference codes is D 0 +(k+1) ⁇ . Since the distance between each two reference codes is uniquely determined, the absolute position at which the readhead is initially located can be calculated each time the readhead passes through two adjacent reference codes.
  • the incremental displacement measuring unit 13 can calculate the incremental displacement as x1;
  • the mask 13 is aligned with the reference code 3.
  • the light transmitted from the mask 13 is now a light pulse, and the reference position photodetector 14 can detect a corresponding reference pulse signal.
  • the incremental displacement measuring unit 13 starts to calculate the distance x2; when the reading head reaches the reference code 4, the mask 13 is aligned with the reference code 4, and the light transmitted from the mask 13 is a light pulse at this time.
  • the reference position photodetector 14 is capable of detecting a corresponding reference pulse signal, whereby the incremental displacement measuring unit 13 can determine the value of the distance x2; since the reference code on the main raster is designed by distance coding, between each two There is a certain distance, so the calculated distance x2 can be used to determine the absolute position of the reference code, and x1-x2 to determine the absolute position of the point at which the readhead is initially located.
  • the incident light first passes through the mask to modulate the light for the first time.
  • the code track on the mask 13 modulates the incident beam into a stripe beam of light and dark, after which The modulated stripe beam light is reflected back to the mask in the reference code region on the main grating. At this time, the light is modulated a second time, and finally the light passes through the mask 13 again for the third modulation.
  • the main grating 15 and the reference grating 19 are of a reflective grating.
  • the intensity of the light received by the photodetector also changes, which is equivalent to autocorrelation of the coding structure of the mask itself, when the coded track of the mask is When the same reference code 2 on the main grating is fully aligned, the correlation is the largest, and the intensity received by the detector is the smallest.
  • the code channel on the mask and the reference code on the main grating are shifted by one bit, the light intensity changes sharply. Large, so that a negative reference pulse signal can be formed for alignment of the reference position.
  • the light intensity received at the detector is theoretically 0, that is, the peak W2 corresponding to the pulse signal, and the reference peak is realized by using the peak value. Positioning.
  • the peak of the reference pulse signal is a very small light intensity, so the interference of the external light to the detector will seriously affect the contrast of the reference signal.
  • the mask material is often Glass fiber, even if it is coated with anti-reflective material on its surface, can not eliminate its reflection effect, so that the mask itself will reflect a part of the light into the detector, which is equivalent to superimposing a DC component on the reference pulse signal.
  • the contrast is greatly reduced, which affects the positioning accuracy of the reference code.
  • the mask is rotated by a small angle ( ⁇ 5°) in a direction perpendicular to the slit, and the reflected light is reflected outside the detector. The area can enhance the contrast of the light intensity signal and improve the positioning accuracy of the reference code.
  • the code track of the mask on the mask has a coded number of 100 and a line width of 10 ⁇ m, wherein there are 23 light transmissive units 8 and 77 opaque units 7 as shown in FIG.
  • the total width is 1mm and the beam diameter is 1.2mm, which covers an area of 1mm.
  • a slit of 10 ⁇ m width is much larger than the wavelength of the laser used by 660 nm, which only produces a small diffraction effect, but since the signal at the peak of the reference pulse is very weak, a small diffraction effect can mask the signal in noise.
  • the design of the code therefore takes into account the effect of the diffraction effect on it.
  • the 100-bit encoding structure is designed by using the enumeration method.
  • the specific encoding is: “0110000100000000100110000110100000001000000000011001000000100000000101000001100010000001001000001110”, with a sharp pulse signal, the width of the peak is W1 is 26 ⁇ m, and the reference point positioning of 0.6 ⁇ m can be realized through circuit subdivision. degree.

Abstract

一种绝对式光栅尺，其中，主光栅（15）上分布有若干个参考编码道（2），任意相邻的两个参考编码道（2）之间的距离与其余任意相邻的两个参考编码道（2）之间的距离不相同，第一分光镜（12）将光源（11）的光分成射向主光栅（15）的光束和射向增量位移测量单元（23）的光束，射向主光栅（15）的光束经过掩膜板（13）到达主光栅（15）并被反射后，再次经过掩膜板（13）后被参考位置光电探测器（14）接收，掩膜板（13）上设有与参考编码道（2）相同的编码道，掩膜板（13）的位置设置成：掩膜板（13）绕θx方向倾斜一个小的角度，使得射向掩膜板（13）的光束被掩膜板（13）反射后不被参考位置光电探测器（14）接收，可以增强参考信号对比度，实现0.6μm的参考点定位精度。

Description

一种绝对式光栅尺 【技术领域】
本发明涉及测量领域，尤其涉及一种绝对式光栅尺。
【背景技术】
绝对式光栅尺的主光栅上拥有两条码道，一条增量码道上刻有等间距的光栅线纹用于增量位移的测量，另一条码道上刻有若干参考点标记，用于光栅尺开机时参考点的定位，结合增量位移测量和参考点的定位即可实现光栅尺的绝对测量，目前市场上的大部分光栅尺产品读数头采用反射式测量方式，得到的参考点信号为负脉冲信号，因此尖峰处的信号强度往往很低，这时轻微的外界光信号的干扰便会使得信号的对比度变的很差，不易于参考点的精确定位。
【发明内容】
为了克服现有技术的不足，本发明提供了一种绝对式光栅尺，以有效增强参考信号的对比度。
一种绝对式光栅尺，包括主光栅和读数头部件，所述读数头部件包括增量位移测量单元，所述读数头部件还包括第一分光镜、掩膜板和参考位置光电探测器，所述主光栅上分布有若干个参考编码道，任意相邻的两个参考编码道之间的距离与其余任意相邻的两个参考编码道之间的距离不相同，所述第一分光镜用于将光源的光分成射向主光栅的光束和射向增量位移测量单元的光束，所述射向主光栅的光束经过所述掩膜板到达所述主光栅并被反射后，再次经过所述掩膜板后被所述参考位置光电探测器接收，所述掩膜板上设有与所述参考编码道相同的编码道，所述掩膜板的位置设置成：射向所述掩膜板的光束被所述掩膜板反射后不被所述参考位置光电探测器接收。
优选地，
射向所述掩膜板的光束与所述掩膜板的法线之间具有一个锐角夹角，即在掩膜板与主光栅平行下，掩膜板绕图2中的θx方向转动一个角度从而使射向所述掩膜板的光束与所述掩膜板的法线之间具有一个锐角夹角。
为了提高脉冲信号的对比度，将读数头中的掩膜板绕与狭缝垂直的方向略微旋转一个小的角度，这样既可以保证光束穿过掩膜板后的光场分布与之前一致，又可以使掩膜板本身反射回的光偏离，不被光电探测器所接收，有效地增强脉冲信号的对比度，提高参考位置(参考编码)的判别精度。
优选地，
所述锐角夹角小于5°。
优选地，
所述掩膜板上的编码道上分布有透光单元和反光单元。
优选地，
射向所述掩膜板的光束大小大于所述掩膜板上的编码道的宽度。
优选地，
所述编码道的编码为：
0110000100000000100110000110100000001000000000011001000000100000000101000001100010000001001000001110，其中，1代表透光单元，0代表反光单元。
优选地，
每个透光单元和每个反光单元的宽度为10μm。
利用脉冲信号的尖峰即可实现参考位置的对齐，脉冲信号的尖峰宽度与编码的线宽成正比，这里使用的编码线宽为10μm，得到的尖峰宽度为26μm，可以实现0.6μm精度的参考点定位。
所述的编码是考虑了衍射效应后的仿真设计结果，虽然最小的狭缝宽度为10μm，远远大于波长660nm，但是微小的衍射效应便可极大的削弱参考信号的尖脉冲，因此必须考虑衍射效应对其的影响，在此种光路结构中，光束经过读数头中掩膜板后发生第一次衍射，将此种衍射近似为菲涅尔衍射进行处理，当光束到达主光栅上的参考点区域时，反射光将发生第二次菲涅尔衍射，当反射回读数头中的掩膜板后，将第二次菲涅尔衍射的光场与掩膜板的狭缝结构做互相关即可得到脉冲信号波形，用于参考点的定位。
本发明由于采用以上技术方案，具有以下优点：1、倾斜放置的掩膜板可以将其自身的光反射到光电探测器之外，增强参考信号对比度，提高参 考点的定位精度。2、考虑了衍射效应后仿真设计出100位随机编码，可以得到尖锐的脉冲信号，其尖端宽度为26μm，可以实现0.6μm的参考点定位精度。
【附图说明】
图1是本发明一些实施例的绝对式光栅尺的原理框图；
图2是图1的局部示意图；
图3是本发明一些实施例的主光栅的增量码道及其参考编码；
图4是本发明一些实施例的读数头中掩膜板上的编码道；
图5是本发明一些实施例的参考脉冲信号。
【具体实施方式】
以下对发明的较佳实施例作进一步详细说明。
图1和2所示，一种实施例的绝对式光栅尺，包括主光栅15和读数头部件，所述读数头部件包括增量位移测量单元23和参考位置测量单元22，其中，参考位置测量单元22包括第一分光镜12、掩膜板13和参考位置光电探测器14，所述主光栅15上分布有若干个参考编码道2。
光源11(例如激光二极管)发出波长为660nm的红光激光L0，经过准直透镜准直为平行光束，之后经过一个孔径光阑，将光束整形为直径为1.2mm的光束，所述第一分光镜(能量分光镜)12将光源11的光分成两束激光：一束转折90°后射向主光栅15，另一束透过第一分光镜12射向增量位移测量单元23，用于测量读数头相对于主光栅15移动的增量位移。所述射向主光栅的光束L1经过所述掩膜板13到达所述主光栅15，并被主光栅15反射后，再次经过所述掩膜板13后(光束L2)，透过第一分光镜12被所述参考位置光电探测器14接收。
增量位移测量单元23可以是现有技术常用的技术方案，用于测量读数头相对于主光栅15移动的增量位移。
所述掩膜板13上设有与所述参考编码道相对应的编码道，由一系列透光单元8(如图4中的白色狭缝)与不透光单元7(如图4中的黑色线纹)组成。
增量位移测量单元23包含了干涉光路，射向增量位移测量单元23的激光束又被第二分光镜16分为两束，一束射向参考光栅19，另一束射向 主光栅15，其中参考光栅的+N级衍射光会与主光栅的+N级衍射光形成干涉条纹(例如参考光栅19的+1级衍射光经过反射镜24和第二分光镜16反射后，与主光栅15的+1级衍射光经过反射镜20和第二分光镜16透射后的光束衍射)，参考光栅的-N级衍射光会与主光栅的-N级衍射光形成干涉条纹(例如参考光栅19的-1级衍射光经过反射镜21和第二分光镜16反射后，与主光栅15的-1级衍射光经过反射镜25和第二分光镜16透射后的光束衍射)，当读数头沿主光栅长度方向发生位移时，由于多普勒效应，干涉条纹会发生明暗变化，每当读数头移动一个光栅周期时，干涉条纹便会发生一次明暗变化，光路中还放置有若干光电探测器17和光电探测器18，用于感应干涉条纹的光强变化，通过计数干涉条纹的明暗周期变化个数可以解算出读数头移动的增量位移。
如图3所示，在主光栅15上设置有若干参考编码2，其余为光栅线纹，即增量码道1，在增量码道1上，等间距的光栅线纹的光栅周期为1μm，光栅类型为反射式全息衍射光栅。在主光栅15上，任意相邻的两个参考编码道2之间的距离与其余任意相邻的两个参考编码道之间的距离不相同，即参考编码道2按照距离编码的设计方式分布在增量码道1上，此距离编码使得相邻两个参考编码间的距离为唯一确定的值。例如，某两个相邻的参考编码的距离为D0+kδ，另两个相邻的参考编码的距离为D0+(k+1)δ。由于每两个参考编码之间的距离都是唯一确定的，每当读数头经过相邻的两个参考编码时，便可以计算出读数头初始所在的绝对位置。
假设读数头初始位置在a点，当读数头移动一段距离，经过其相邻两个参考编码3和参考编码4时，增量位移测量单元13可以计算出增量位移为x1；而在读数头到达参考编码3时，掩膜板13与参考编码3对齐，从掩膜板13透射出的光此时是一个光脉冲，此时参考位置光电探测器14能够检测到一个对应的参考脉冲信号，此时增量位移测量单元13开始计算距离x2；当读数头到达参考编码4时，掩膜板13与参考编码4对齐，从掩膜板13透射出的光此时是一个光脉冲，此时参考位置光电探测器14能够检测到一个对应的参考脉冲信号，至此增量位移测量单元13可以确定距离x2的值；由于主光栅上的参考编码是经过距离编码设计的，每两个之间都有确定的距离，因此通过计算出的距离x2便可以确定参考编码所处的绝对位置，通过x1-x2进而确定读数头初始所在a点的绝对位置。
如图1和2所示，入射光首先穿过掩膜板，将光进行了第一次调制，所述掩膜板13上的编码道可以将入射光束调制为明暗相间的条纹状光束，之后调制过的条纹状光束光又射向主光栅上的参考编码区域被反射回掩膜板，这时光被第二次调制，最后光又再次穿过掩膜板13，进行第三次调制后被光电探测器所接收。在本实施例中主光栅15和参考光栅19采用的是反射式光栅。当掩膜板与主光栅15发生相对位移时，被光电探测器所接收的光强也会发生变化，这相当于对掩膜板自身的编码结构做自相关，当掩膜板的编码道与主光栅上的相同的参考编码2完全对齐时相关度最大，被探测器所接收到的光强最小，当掩膜板上的编码道与主光栅上参考编码错开一位时，光强急剧变大，这样便可以形成一个负的参考脉冲信号用于参考位置的对准。如图5所示，当掩膜板与主光栅上的参考点完全对齐时，此时探测器上接收的光强理论上为0，即对应脉冲信号的尖峰W2，利用这个尖峰值实现参考编码的定位。
如图3所示，参考脉冲信号的尖峰是一个极小的光强，因此很小的外界光对探测器的干扰便会严重影响到参考信号的对比度，实际使用中，掩膜板材料往往是玻璃纤维，即使在其表面镀有防反射材料，也不能杜绝其反射效应，这样掩膜板自身便会反射一部分光进入探测器之中，这就相当于给参考脉冲信号整体叠加了一个直流分量，使其对比度大打折扣，影响到参考编码的定位精度，此时将掩膜板绕与狭缝垂直的方向旋转一个小的角度(<5°)，将自身反射的光反射到探测器之外的区域，可以增强光强信号的对比度，提高参考编码的定位精度。
在一个实施例中，掩膜板上的码道的编码位数为100，线宽为10μm，其中透光单元8有23个，不透光单元7有77个，如图2所示，因此总的宽度为1mm，光束直径1.2mm，可以覆盖1mm的区域。在此方案中，10μm宽度的狭缝远大于所用激光波长660nm，只会产生很小的衍射效应，但由于参考脉冲的尖峰处信号非常微弱，小的衍射效应即可将信号掩膜在噪声之中，因此编码的设计考虑了衍射效应对其的影响。使用枚举法设计了100位的编码结构，具体编码为：“0110000100000000100110000110100000001000000000011001000000100000000101000001100010000001001000001110”，具有尖锐的脉冲信号，其尖峰的宽度W1为26μm，经过电路细分，可以实现0.6μm的参考点定位精 度。
以上内容是结合具体的优选实施方式对本发明所作的进一步详细说明，不能认定本发明的具体实施只局限于这些说明。对于本发明所属技术领域的普通技术人员来说，在不脱离本发明构思的前提下，还可以做出若干简单推演或替换，都应当视为属于本发明由所提交的权利要求书确定的专利保护范围。

Claims (7)

  1. 一种绝对式光栅尺，包括主光栅和读数头部件，所述读数头部件包括增量位移测量单元，其特征是，所述读数头部件还包括第一分光镜、掩膜板和参考位置光电探测器，所述主光栅上分布有若干个参考编码道，任意相邻的两个参考编码道之间的距离与其余任意相邻的两个参考编码道之间的距离不相同，所述第一分光镜用于将光源的光分成射向主光栅的光束和射向增量位移测量单元的光束，所述射向主光栅的光束经过所述掩膜板到达所述主光栅并被反射后，再次经过所述掩膜板后被所述参考位置光电探测器接收，所述掩膜板上设有与所述参考编码道相同的编码道，所述掩膜板的位置设置成：射向所述掩膜板的光束被所述掩膜板反射后不被所述参考位置光电探测器接收。
  2. 如权利要求1所述的绝对式光栅尺，其特征是，
    射向所述掩膜板的光束与所述掩膜板的法线之间具有一个锐角夹角。
  3. 如权利要求1所述的绝对式光栅尺，其特征是，
    所述锐角夹角小于5°。
  4. 如权利要求1所述的绝对式光栅尺，其特征是，
    所述掩膜板上的编码道上分布有透光单元和反光单元。
  5. 如权利要求1所述的绝对式光栅尺，其特征是，射向所述掩膜板的光束大小大于所述掩膜板上的编码道的宽度。
  6. 如权利要求1所述的绝对式光栅尺，其特征是，所述编码道的编码为：
    0110000100000000100110000110100000001000000000011001000000100000000101000001100010000001001000001110，其中，1代表透光单元，0代表反光单元。
  7. 如权利要求6所述的绝对式光栅尺，其特征是，每个透光单元和每个反光单元的宽度为10μm。
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