CN102435136A - Spatial phase-shifting unit, interferometry system applying same and phase-correcting unit - Google Patents

Abstract

Translated fromChinese

本发明提供一种干涉测量装置，包括用以产生偏振状态相互正交线偏振光的装置，该相互正交线偏振光分别称为参考光和测试光；相位调制式空间光调制器，设置于参考光或测试光的光路中，用以改变光波前的空间相位分布；该空间光调制器具有复数个像素，每一像素具备特定的相位分布；其中，经所述空间光调制器相位调制后的光称为调制光，未经调制的光称为未调制光；基于所述调制光和未调制光实现干涉测量的干涉仪；对干涉仪产生的相干光探测的光探测装置；且二者像素相对应。本发明提供的装置，不但可以实现多个空间载波相移分布时的测量，而且还可以实现高精度动态测量。本发明还提供一种空间相移装置以及液晶空间光调制器相位校正装置。

The invention provides an interferometry device, including a device for generating mutually orthogonal linearly polarized light with polarization states, and the mutually orthogonally polarized light is called reference light and test light respectively; a phase modulation spatial light modulator is arranged on In the light path of the reference light or the test light, it is used to change the spatial phase distribution of the light wavefront; the spatial light modulator has a plurality of pixels, and each pixel has a specific phase distribution; wherein, after phase modulation by the spatial light modulator The light is called modulated light, and the unmodulated light is called unmodulated light; an interferometer that realizes interferometry based on the modulated light and unmodulated light; a light detection device that detects coherent light generated by the interferometer; and both corresponding to pixels. The device provided by the invention can not only realize the measurement of phase shift distribution of multiple space carriers, but also realize high-precision dynamic measurement. The invention also provides a spatial phase shift device and a liquid crystal spatial light modulator phase correction device.

Description

Translated fromChinese

空间相移装置及应用该装置的干涉测量装置、相位校正装置Spatial phase shifting device, interferometry device and phase correction device using the device

技术领域technical field

本发明涉及光学检测技术领域，具体涉及一种空间相移装置。本发明还同时提供一种相位校正装置、应用该空间相移装置的干涉测量装置。The invention relates to the technical field of optical detection, in particular to a spatial phase shift device. The invention also provides a phase correction device and an interferometric measurement device using the space phase shifting device.

背景技术Background technique

干涉仪在光学元件面形检测方面有着重要的应用价值。就干涉测量方法而言，可分为时域相移法、傅里叶分析法和空间载波相移法。时域相移法测量精度高，在光学检测中应用广泛，但它至少需要三幅干涉图，受环境振动影响大，所以不适合动态环境下测量。傅里叶分析法只需要一幅空间载波干涉图，所以适合动态环境下测量，但傅里叶分析法测量精度相对较低且不能判断被测相位的正负。空间载波相移法结合了时域相移法和傅里叶分析法的优点，通过处理单幅空间载波干涉图近似达到时域相移法的精度，所以空间载波相移法在动态高精度干涉测量方面有着重要的应用前景。Interferometer has important application value in the surface shape detection of optical components. As far as the interferometry method is concerned, it can be divided into time-domain phase shift method, Fourier analysis method and space carrier phase shift method. The time-domain phase shift method has high measurement accuracy and is widely used in optical detection, but it requires at least three interferograms and is greatly affected by environmental vibrations, so it is not suitable for measurement in dynamic environments. The Fourier analysis method only needs a space carrier interferogram, so it is suitable for measurement in a dynamic environment, but the measurement accuracy of the Fourier analysis method is relatively low and cannot judge the positive or negative of the measured phase. The space carrier phase shift method combines the advantages of the time domain phase shift method and the Fourier analysis method, and approximately achieves the accuracy of the time domain phase shift method by processing a single space carrier interferogram, so the space carrier phase shift method is used in dynamic high-precision interference There are important application prospects in measurement.

目前实现空间载波相移的方法主要有两种：一种是通过倾斜参考镜引入一个适当的空间载频量，使相邻像素点间的位相差为π/2，但是实际测量时很难调整参考镜使空间载频严格等于理论值。另一种是利用偏振分光器件在同一个CCD上得到四幅相移π/2的干涉图，在公开号为CN101111739A的中国专利文献中即公开了该装置，该专利文献中，设置菲索干涉仪的参考镜和测试镜，使他们具有不同的斜率，从而分离测试光T和参考光R，然后使测试光和参考光经过不同的偏振光学元件，在测试光和参考光之间引入空间载波相移，最后实现了在同一个CCD上得到四幅相移π/2的干涉图。上述介绍的装置能够实现动态干涉测量，但是由于参考光和测试光的夹角较大，他们属于非共路系统，容易引进较大的系统误差。为此，在专利号为US7230717B2美国中，公开了一种共光路的动态干涉仪系统，该美国专利中参考光和测试光的夹角接近为零，但两者的偏振态是正交的，通过在CCD前加一个偏振相位掩模板，偏振相位掩模板的像素分布与CCD的像素分布一致。偏振相位掩模板使参考光和测试光在CCD上每个像素内引入一个特定的相位差，从而获得了空间载波相移分布。At present, there are two main methods to achieve spatial carrier phase shift: one is to introduce an appropriate spatial carrier frequency by tilting the reference mirror, so that the phase difference between adjacent pixels is π/2, but it is difficult to adjust in actual measurement The reference mirror makes the space carrier frequency strictly equal to the theoretical value. The other is to utilize a polarization splitting device to obtain four interferograms with a phase shift of π/2 on the same CCD. The device is disclosed in the Chinese patent document with the publication number CN101111739A. In this patent document, a Fizeau interferometer is set The reference mirror and the test mirror make them have different slopes, thereby separating the test light T and the reference light R, and then make the test light and the reference light pass through different polarization optical elements, and introduce a spatial carrier phase between the test light and the reference light Finally, four interferograms with a phase shift of π/2 can be obtained on the same CCD. The devices described above can realize dynamic interferometry, but due to the large angle between the reference light and the test light, they belong to the non-common path system, which is easy to introduce large system errors. For this reason, in the U.S. Patent No. US7230717B2, a dynamic interferometer system with a common optical path is disclosed. In this U.S. patent, the angle between the reference light and the test light is close to zero, but the polarization states of the two are orthogonal. By adding a polarization phase mask in front of the CCD, the pixel distribution of the polarization phase mask is consistent with the pixel distribution of the CCD. The polarization phase mask makes the reference light and the test light introduce a specific phase difference in each pixel on the CCD, thus obtaining the spatial carrier phase shift distribution.

上述偏振相位掩模板虽然可以引入空间载波相移，但是它的加工比较困难，容易产生加工误差，而且不易校正加工误差，而加工误差将直接影响干涉测量的精度，因此上述美国专利US7230717B2介绍的偏振相位掩模板的精度有待进一步提高；此外，一个加工好的偏振相位掩模板只能产生特定的空间载波相移分布，不能进行人为的修改，应用不免受到限制。Although the above-mentioned polarization phase mask can introduce space carrier phase shift, its processing is more difficult, it is easy to produce processing errors, and it is not easy to correct processing errors, and processing errors will directly affect the accuracy of interferometric measurements. Therefore, the polarization The accuracy of the phase mask needs to be further improved; in addition, a processed polarization phase mask can only produce a specific spatial carrier phase shift distribution, which cannot be artificially modified, and its application will inevitably be limited.

发明内容Contents of the invention

本发明提供一种干涉测量装置，本发明的干涉测量装置不但可以实现多个空间载波相移分布时的测量，而且还可以实现误差校正，提高测量精度。本发明还同时提供一种空间相移装置以及液晶空间光调制器相位校正装置。The invention provides an interference measurement device. The interference measurement device of the invention can not only realize the measurement of the phase shift distribution of multiple space carriers, but also realize error correction and improve measurement accuracy. The invention also provides a spatial phase shift device and a liquid crystal spatial light modulator phase correction device.

本发明提供的一种干涉测量装置，包括，An interferometry device provided by the present invention includes:

用以产生偏振状态相互正交线偏振光的装置，该相互正交线偏振光分别称为参考光和测试光；means for generating mutually orthogonal linearly polarized light of polarization states, the mutually orthogonally linearly polarized light being referred to as reference light and test light, respectively;

相位调制式空间光调制器，设置于参考光或测试光的光路中，用以改变光波前的空间相位分布；该空间光调制器具有复数个像素，每一像素具备特定的相位分布；其中，经所述空间光调制器相位调制后的光称为调制光，未经调制的光称为未调制光；The phase modulation spatial light modulator is arranged in the optical path of the reference light or the test light to change the spatial phase distribution of the light wavefront; the spatial light modulator has a plurality of pixels, and each pixel has a specific phase distribution; wherein, The light modulated by the spatial light modulator is called modulated light, and the unmodulated light is called unmodulated light;

基于所述调制光和未调制光实现干涉测量的干涉仪；An interferometer for interferometry based on said modulated light and unmodulated light;

对干涉仪产生的相干光探测的光探测装置，该光探测装置具备与所述空间光调制器相同的像素分布；且二者像素相对应。A light detection device for detecting coherent light generated by the interferometer, the light detection device has the same pixel distribution as that of the spatial light modulator; and the two pixels correspond to each other.

可选的，所述空间光调制器为反射式液晶空间光调制器。Optionally, the spatial light modulator is a reflective liquid crystal spatial light modulator.

可选的，所述产生偏振状态相互正交线偏振光的装置包括共轴设置的线偏振光起偏器和偏振分光棱镜。Optionally, the device for generating linearly polarized light with mutually orthogonal polarization states includes a linearly polarized light polarizer and a polarization beam splitter prism arranged coaxially.

可选的，所述产生偏振状态相互正交线偏振光的装置还进一步包括使偏振分光镜后的正交线偏振光产生相位延迟的结构。Optionally, the device for generating mutually orthogonal linearly polarized light with polarization states further includes a structure for causing a phase delay to the orthogonally linearly polarized light after the polarization beam splitter.

可选的，液晶空间光调制器至少包括一组2×2分布的像素单元，且所述像素单元中每一像素具有不同的相位。Optionally, the liquid crystal spatial light modulator includes at least a group of pixel units distributed in 2×2, and each pixel in the pixel units has a different phase.

可选的，所述每一像素单元中相位分布分别为0、π/2、π和3π/2。Optionally, the phase distributions in each pixel unit are respectively 0, π/2, π and 3π/2.

可选的，所述干涉仪为菲索干涉仪。Optionally, the interferometer is a Fizeau interferometer.

可选的，还包括相干光源。Optionally, a coherent light source is also included.

本发明还提供一种空间相移装置，包括：沿准直光束照射方向依次设置的偏振器件和液晶空间光调制器，还包括用于对所述液晶空间光调制器相位调制的控制装置。The present invention also provides a spatial phase shifting device, comprising: a polarizing device and a liquid crystal spatial light modulator sequentially arranged along the irradiation direction of the collimated light beam, and a control device for phase modulation of the liquid crystal spatial light modulator.

本发明还提供一种液晶空间光调制器相位校正装置，包括沿光轴依次设置的干涉仪、参考镜、偏振片和液晶空间光调制器。The invention also provides a phase correction device for a liquid crystal spatial light modulator, which includes an interferometer, a reference mirror, a polarizer and a liquid crystal spatial light modulator arranged in sequence along the optical axis.

与现有技术相比，本发明提供的基于液晶空间光调制器干涉测量装置，参考光和测试光的夹角接近为零，因此干涉仪系统像差引起的参考光和测试光之间的光程差的误差较小，即系统误差较小；同时本实施例采用液晶空间光调制器实现空间载波相移，通过控制输入信号在液晶空间光调制器上每个像素对应的灰度，可以得到设计所需的空间载波相移分布，同时它还可以人为地设计输入信号的灰度修改空间载波相移的分布；本发明可实现采集一帧空间载波相移干涉条纹，从中可以提取多帧帧具有特定相移的子干涉图；而且，本发明提供的干涉测量装置，可以通过计算机控制得到任意的空间载波相移分布，从而具有更广泛的应用价值；Compared with the prior art, in the liquid crystal spatial light modulator-based interferometry device provided by the present invention, the angle between the reference light and the test light is close to zero, so the light between the reference light and the test light caused by the aberration of the interferometer system The error of the path difference is small, that is, the system error is small; at the same time, this embodiment uses a liquid crystal spatial light modulator to realize the spatial carrier phase shift, and by controlling the gray level corresponding to each pixel of the input signal on the liquid crystal spatial light modulator, it can be obtained Design the required space carrier phase shift distribution, and it can also artificially design the gray level of the input signal to modify the distribution of the space carrier phase shift; the invention can realize the acquisition of a frame of space carrier phase shift interference fringes, from which multiple frames can be extracted A sub-interferogram with a specific phase shift; moreover, the interferometric device provided by the present invention can obtain any spatial carrier phase shift distribution through computer control, thus having wider application value;

本发明的干涉测量装置还可以实现误差校正，因此可实现高精度动态测量。The interferometric measuring device of the present invention can also realize error correction, so high-precision dynamic measurement can be realized.

附图说明Description of drawings

图1为本发明的干涉测量装置的实施例的示意图；Fig. 1 is the schematic diagram of the embodiment of interferometry device of the present invention;

图2为施加到液晶空间光调制器的周期信号灰度分布的示意图；Fig. 2 is a schematic diagram of the grayscale distribution of a periodic signal applied to a liquid crystal spatial light modulator;

图3为液晶空间光调制器引入的的空间载波相移分布；Fig. 3 is the spatial carrier phase shift distribution introduced by the liquid crystal spatial light modulator;

图4为本发明的干涉测量装置的实施例产生的干涉图；Fig. 4 is the interferogram produced by the embodiment of the interferometric device of the present invention;

图5为从图4中提取的四帧具有特定相移的子干涉图；Figure 5 is a sub-interferogram with a specific phase shift of four frames extracted from Figure 4;

图6为本发明的空间相移装置的实施例的示意图；6 is a schematic diagram of an embodiment of a spatial phase shifting device of the present invention;

图7为本发明的液晶空间光调制器相位校正装置的实施例的示意图。FIG. 7 is a schematic diagram of an embodiment of a phase correction device for a liquid crystal spatial light modulator of the present invention.

具体实施方式Detailed ways

在下面的描述中阐述了很多具体细节以便于充分理解本发明。但是本发明能够以很多不同于在此描述的其它方式来实施，本领域技术人员可以在不违背本发明内涵的情况下做类似推广，因此本发明不受下面公开的具体实施的限制。In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, the present invention can be implemented in many other ways different from those described here, and those skilled in the art can make similar extensions without violating the connotation of the present invention, so the present invention is not limited by the specific implementations disclosed below.

图1为本发明的干涉测量装置的实施例的示意图。请参看图1，本实施例中，干涉测量装置中包括正交偏振光源、相位调制式空间光调制器、干涉仪以及光探测装置。其中，FIG. 1 is a schematic diagram of an embodiment of the interferometric device of the present invention. Please refer to FIG. 1 , in this embodiment, the interferometric device includes an orthogonally polarized light source, a phase-modulated spatial light modulator, an interferometer, and a light detection device. in,

所述正交偏振光源用于产生偏振状态相互正交的线偏振光，该相互正交的线偏振光分别称为参考光和测试光，本实施例中该正交偏振光源包括短相干光源、线偏振光起偏器以及线偏振光分束器。The orthogonally polarized light source is used to generate linearly polarized light whose polarization states are orthogonal to each other, and the mutually orthogonally polarized light is called reference light and test light respectively. In this embodiment, the orthogonally polarized light source includes a short coherent light source, Linearly polarized light polarizers and linearly polarized light beam splitters.

空间光调制器设置于上述的参考光或者测试光的光路中，以实现对参考光或者测试光的相位调制，改变光波前的空间相位分布。该空间光调制器具有复数个像素，每一像素具备特定的相位分布；其中，经所述空间光调制器相位调制后的光称为调制光，未经调制的光称为未调制光；The spatial light modulator is arranged in the optical path of the above-mentioned reference light or test light, so as to realize the phase modulation of the reference light or test light, and change the spatial phase distribution of the light wavefront. The spatial light modulator has a plurality of pixels, and each pixel has a specific phase distribution; wherein, the light modulated by the spatial light modulator is called modulated light, and the unmodulated light is called unmodulated light;

本实施例中的干涉仪为动态索菲干涉仪，其中，所述调制光和未调制光构成索菲干涉仪的测试光和参考光，索菲干涉仪基于所述调制光和未调制光实现干涉测量。当然，所述干涉仪还可以为其它动态干涉仪。The interferometer in this embodiment is a dynamic Sophie interferometer, wherein the modulated light and unmodulated light constitute the test light and reference light of the Sophy interferometer, and the Sophy interferometer realizes based on the modulated light and unmodulated light Interferometry. Certainly, the interferometer may also be other dynamic interferometers.

所述光探测装置设置于索菲干涉仪的干涉图像面位置，用于对干涉图进行探测。其中，该光探测装置具备与所述空间光调制器相同的像素分布；且二者像素相对应。本实施例中，光探测装置为CCD 17。The light detection device is arranged at the position of the interference image plane of the Sophy interferometer, and is used for detecting the interference image. Wherein, the light detection device has the same pixel distribution as that of the spatial light modulator; and the pixels of the two are corresponding. In this embodiment, the photodetection device is aCCD 17.

下面进行详细进行描述。A detailed description is given below.

如图1所示，短相干光源1输出的光束经过作为起偏器的偏振片2之后得到线偏振光，线偏振光束经过偏振分光棱镜3后分成P光和S光，其中，P光沿线偏振光入射方向由偏振分光分光棱镜3透射而出，S光经偏振分光棱镜分束面反射，沿垂直于线偏振光入射方向向下出射。As shown in Figure 1, the light beam output by the short coherentlight source 1 passes through thepolarizer 2 as a polarizer to obtain linearly polarized light, and the linearly polarized light beam is divided into P light and S light after passing through the polarization beam splitter prism 3, wherein the P light is polarized along the line The incident direction of light is transmitted by the polarization beam splitting prism 3, and the S light is reflected by the beam splitting surface of the polarization beam splitting prism, and exits downward along the direction perpendicular to the incident direction of the linearly polarized light.

在所述偏振分光棱镜3的右后侧和下侧分别设置第一波片5和第二波片4。其中，两波片均为四分之一波片。P光经过所述第一波片5之后被放置在该第一波片5之后的第一参考镜7所反射，并再次经过第一波片5后，P光偏振方向旋转90度后进入偏振分光棱镜3，经分束面反射后由偏振分光棱镜3上面的出射，该光束定义为S2光束，S2光束的相位是一个平面。Afirst wave plate 5 and asecond wave plate 4 are respectively arranged on the right rear side and the lower side of the polarization beam splitter prism 3 . Wherein, the two wave plates are quarter wave plates. After the P light passes through thefirst wave plate 5, it is reflected by thefirst reference mirror 7 placed behind thefirst wave plate 5, and after passing through thefirst wave plate 5 again, the polarization direction of the P light is rotated by 90 degrees and enters the polarization The beam-splitting prism 3 is reflected by the beam-splitting surface and emerges from the top of the polarization beam-splitting prism 3. The beam is defined as an S2 beam, and the phase of the S2 beam is a plane.

另一方面，S光经过第二波片4和第一偏振片22a后，被设置于第一偏振片22a下侧的空间光调制器23相位调制后反射，并再次通过第一偏振片22a和第二波片4，偏振方向旋转90度后通过偏振分光棱镜3，该光束定义为P2。On the other hand, after the S light passes through thesecond wave plate 4 and thefirst polarizer 22a, it is reflected after being phase-modulated by the spatiallight modulator 23 arranged on the lower side of thefirst polarizer 22a, and passes through thefirst polarizer 22a and thefirst polarizer 22a again. Thesecond wave plate 4 rotates the polarization direction by 90 degrees and passes through the polarization beam splitter prism 3, and the light beam is defined as P2.

本实施例中，空间光调制器23为反射式液晶空间光调制器，该液晶空间光调制器23具备复数个像素。所述的液晶空间光调制器23与计算机24连接，在相位调制模式下，计算机24通过液晶空间光调制器的驱动电路输入一定的灰度信号，可使得液晶空间光调制器的像素产生一定的相位变化。根据液晶空间光调制器的相位调制特定可知，输入信号的灰度与相位调制的大小成正比，对不同的像素输入不同的灰度信号，可使得不同的像素产生不同的相位变化，从而可通过计算机控制液晶空间光调制器的相位分布。In this embodiment, the spatiallight modulator 23 is a reflective liquid crystal spatial light modulator, and the liquid crystal spatiallight modulator 23 has a plurality of pixels. The liquid crystal spatiallight modulator 23 is connected to thecomputer 24. In the phase modulation mode, thecomputer 24 inputs a certain grayscale signal through the driving circuit of the liquid crystal spatial light modulator, so that the pixels of the liquid crystal spatial light modulator can generate certain grayscale signals. phase change. According to the specificity of the phase modulation of the liquid crystal spatial light modulator, the gray level of the input signal is proportional to the size of the phase modulation. Inputting different gray level signals to different pixels can cause different phase changes in different pixels, so that it can be passed A computer controls the phase distribution of the liquid crystal spatial light modulator.

本实施例中，液晶空间光调制器23共有1024×768个像素，通过在计算机上施加与所述液晶空间光调制器23像素分布相同的、且为周期性的灰度分布信号，如图2所示(图2示出的为其中16个像素的信号灰度分布)，可在液晶空间光调制器23上产生周期性的相位分布。在本实施例中，以相邻2×2个像素为一个周期，称为像素单元。在一个周期中，像素的相位分布分别为0，π/2，π和3π/2。当光束经液晶空间光调制器23反射后，再经过第一偏振片22a，其光束被调制后的相位分布将如图3所示，其也是周期分布。当然，还可以通过改变计算机信号的灰度分布，得到其它的相位分布，例如，可以使得相邻2×2个像素的相位分布分别为0，π/2，3π/2和π，或者0，π/3，2π/3，和π。In this embodiment, the liquid crystal spatiallight modulator 23 has a total of 1024×768 pixels. By applying the same periodic gray scale distribution signal as the pixel distribution of the liquid crystal spatiallight modulator 23 on the computer, as shown in FIG. 2 As shown (FIG. 2 shows the signal grayscale distribution of 16 pixels), a periodic phase distribution can be generated on the liquid crystal spatiallight modulator 23 . In this embodiment, a period of adjacent 2×2 pixels is called a pixel unit. In one cycle, the phase distributions of the pixels are 0, π/2, π and 3π/2, respectively. When the light beam is reflected by the liquid crystal spatiallight modulator 23 and then passes through thefirst polarizer 22a, the modulated phase distribution of the light beam will be as shown in FIG. 3 , which is also a periodic distribution. Of course, other phase distributions can also be obtained by changing the grayscale distribution of the computer signal, for example, the phase distributions of adjacent 2×2 pixels can be 0, π/2, 3π/2 and π, or 0, π/3, 2π/3, and π.

可见，通过计算机24向液晶空间光调制器23输入如图2所示的周期信号，则得到光束P2的相位如图3所示。光束S2和P2经过聚焦透镜9，被分光棱镜10反射，然后经准直镜11准直，光束S2被索菲干涉仪中设置的第二参考镜12和第二测试镜13反射后的光束分别定义为SR和ST，光束P2被第二参考镜12和第二测试镜13反射后的光束分别定义为PR和PT。It can be seen that, through thecomputer 24 inputting the periodic signal as shown in FIG. 2 to the liquid crystal spatiallight modulator 23 , the phase of the light beam P2 is obtained as shown in FIG. 3 . The light beams S2 and P2 pass through the focusinglens 9, are reflected by thedichroic prism 10, and then are collimated by thecollimating mirror 11. The light beams S2 are reflected by thesecond reference mirror 12 and thesecond test mirror 13 provided in the Sophy interferometer respectively are defined as SR and ST, and the beams of the light beam P2 reflected by thesecond reference mirror 12 and thesecond test mirror 13 are respectively defined as PR and PT.

本实施例中，第二参考镜12和第二测试镜13反射光间的光程差为2ΔL，，通过一维平移台8调节第一参考镜7的位置，使P2和S2的光程差也为2ΔL，则SR和ST的光程差为2ΔL，PR和PT的光程差为2ΔL，SR和PR的光程差为2ΔL，ST和PT的光程差为2ΔL，PT和SR的光程差为0，只有ST和PR的光程差为4ΔL，因为光源是短相干长度光源，其相干长度远小于2ΔL，因此只有光束PT和光束SR才有可能干涉。In this embodiment, the optical path difference between thesecond reference mirror 12 and the reflected light of thesecond test mirror 13 is 2ΔL, and the position of thefirst reference mirror 7 is adjusted through the one-dimensional translation stage 8, so that the optical path difference between P2 and S2 It is also 2ΔL, then the optical path difference between SR and ST is 2ΔL, the optical path difference between PR and PT is 2ΔL, the optical path difference between SR and PR is 2ΔL, the optical path difference between ST and PT is 2ΔL, the light of PT and SR The path difference is 0, and only the optical path difference of ST and PR is 4ΔL, because the light source is a short coherence length light source, and its coherence length is much smaller than 2ΔL, so only the light beam PT and the light beam SR can interfere.

光束PT和光束SR透过分光棱镜10，再经成像透镜15和第二偏振片22b，最后在CCD 17(CCD 17具有与液晶空间光调制器23相同的像素数和分布，设置于干涉测量装置时，二者像素相对应。)，和上得到空间载波相移干涉条纹，如图4所示，该干涉图中包含被测光学元件-第二测试镜13的面形误差，同时它还包含液晶空间光调制器23引进的空间载波相移分布信息。因为空间载波相移分布是预先设计并有计算机控制的，所以空间载波相移分布是已知的，如图3所示。在空间载波相移干涉条纹中，把空间载波相移值为0对应的所有像素组成第一幅子干涉图，将把空间载波相移值为π/2，π和3π/2对应的所有像素分别组成第二、第三和第四子干涉图，如图5所示，利用传统的四步相移算法就能从这四幅子干涉图中提取被测光学元件(第二测试镜13)的误差分布。The light beam PT and the light beam SR pass through thedichroic prism 10, then through theimaging lens 15 and thesecond polarizer 22b, finally at the CCD 17 (theCCD 17 has the same pixel number and distribution as the liquid crystal spatiallight modulator 23, and is arranged on the interferometric device When, the two pixels are corresponding.), and above obtain the space carrier phase shift interference fringe, as shown in Figure 4, this interferogram contains the surface error of the measured optical element-thesecond test mirror 13, and it also contains simultaneously The liquid crystal spatiallight modulator 23 introduces phase shift distribution information of the spatial carrier. Because the spatial carrier phase shift distribution is predesigned and computer controlled, the spatial carrier phase shift distribution is known, as shown in Figure 3. In the space carrier phase shift interference fringe, all the pixels corresponding to the space carrier phase shift value of 0 are composed into the first sub-interferogram, and all the pixels corresponding to the space carrier phase shift value of π/2, π and 3π/2 Respectively form the second, third and fourth sub-interferograms, as shown in Figure 5, the traditional four-step phase shift algorithm can be used to extract the measured optical element (second test mirror 13) from these four sub-interferograms Error distribution.

本发明的实施例提供的基于液晶空间光调制器干涉测量装置，参考光和测试光的夹角接近为零，因此干涉仪系统像差引起的参考光和测试光之间的光程差的误差较小，即系统误差较小；同时本实施例采用液晶空间光调制器实现空间载波相移，通过控制输入信号在液晶空间光调制器上每个像素的灰度，可以得到设计所需的空间载波相移分布，同时它还可以人为地设计输入信号的灰度修改空间载波相移的分布；因此，本实施例可实现CCD采集一帧空间载波相移干涉条纹，我们从中可以提取四帧相移π/2的子干涉图，因此本实施例提供的干涉仪也可以在动态环境下测量。而且，本发明提供的干涉测量装置，可以通过计算机控制得到任意的空间载波相移分布，从而具有更广泛的应用价值。In the liquid crystal spatial light modulator-based interferometry device provided by the embodiment of the present invention, the angle between the reference light and the test light is close to zero, so the error of the optical path difference between the reference light and the test light caused by the aberration of the interferometer system Smaller, that is, the system error is small; at the same time, this embodiment uses a liquid crystal spatial light modulator to realize the spatial carrier phase shift, and by controlling the grayscale of each pixel of the input signal on the liquid crystal spatial light modulator, the space required for design can be obtained. Carrier phase shift distribution, and it can also artificially design the gray scale of the input signal to modify the distribution of spatial carrier phase shift; Shift the sub-interferogram by π/2, so the interferometer provided by this embodiment can also be measured in a dynamic environment. Moreover, the interferometric device provided by the present invention can obtain any spatial carrier phase shift distribution through computer control, thus having wider application value.

此外，本发明还提供一种空间相移装置，如图6所示，该相移装置包括沿准直光束照射方向依次设置的偏振器件22和液晶空间光调制器23，还包括用于对所述液晶空间光调制器相位调制的控制装置24。本实施例中，所述控制装置24为计算机以及液晶空间光调制器控制电路。此外所述液晶空间光调制器23为反射式。In addition, the present invention also provides a spatial phase shifting device, as shown in Figure 6, the phase shifting device includes apolarizer 22 and a liquid crystal spatiallight modulator 23 arranged in sequence along the irradiation direction of the collimated beam, and also includes aA control device 24 for phase modulation of the liquid crystal spatial light modulator. In this embodiment, thecontrol device 24 is a computer and a liquid crystal spatial light modulator control circuit. In addition, the liquid crystal spatiallight modulator 23 is reflective.

通过控制输入信号在液晶空间光调制器23上每个像素的灰度，可以得到设计所需的空间载波相移分布。其中，输入信号、液晶空间光调制器和CCD的像素个数要一致。By controlling the gray level of each pixel of the input signal on the liquid crystal spatiallight modulator 23, the spatial carrier phase shift distribution required by the design can be obtained. Wherein, the number of pixels of the input signal, the liquid crystal spatial light modulator and the CCD must be consistent.

本发明还提供一种液晶空间光调制器相位校正装置，如图7所示，包括沿光轴依次设置的干涉仪25、参考镜26、偏振片22和液晶空间光调制器23。液晶空间光调制器23与控制装置24相连接。The present invention also provides a liquid crystal spatial light modulator phase correction device, as shown in FIG. 7 , comprising aninterferometer 25 , areference mirror 26 , apolarizer 22 and a liquid crystal spatiallight modulator 23 arranged in sequence along the optical axis. The liquid crystal spatiallight modulator 23 is connected to acontrol device 24 .

通过该装置可校正液晶空间光调制器23和偏振片22的面形误差。其步骤如下，先将液晶空间光调制器23上所有像素的输入信号的灰度设置为零，然后用干涉仪测量液晶空间光调制器23和偏振片22的面形误差之和。根据输入信号的灰度与相位调制的大小成正比的特性，计算校正液晶空间光调制器23和偏振片22的面形误差之和所要求的输入信号的灰度分布，将该灰度分布保存到计算机内，用于液晶空间光调制器的校正。每次使用液晶空间光调制器23时，将校正用的灰度分布和设计得到的灰度分布共同作用到液晶空间光调制器23上，这样就能有效地抑制面形误差的影响，从而得到高精度的空间载波相移分布。The surface error of the liquid crystal spatiallight modulator 23 and thepolarizer 22 can be corrected by this device. The steps are as follows: first set the gray levels of the input signals of all pixels on the liquid crystal spatiallight modulator 23 to zero, and then use an interferometer to measure the sum of the surface errors of the liquid crystal spatiallight modulator 23 and thepolarizer 22 . According to the characteristic that the grayscale of the input signal is proportional to the size of the phase modulation, calculate the grayscale distribution of the input signal required to correct the sum of the surface errors of the liquid crystal spatiallight modulator 23 and thepolarizer 22, and save the grayscale distribution Into the computer for calibration of the liquid crystal spatial light modulator. Every time the liquid crystal spatiallight modulator 23 is used, the gray scale distribution used for correction and the gray scale distribution obtained by design are jointly applied to the liquid crystal spatiallight modulator 23, so that the influence of the surface shape error can be effectively suppressed, thereby obtaining High precision spatial carrier phase shift distribution.

可见，本发明上述实施例的干涉测量装置还可以应用图7所示液晶空间光调制器相位校正装置实现误差校正，因此可实现高精度动态测量。It can be seen that the interferometric device of the above-mentioned embodiment of the present invention can also use the phase correction device of the liquid crystal spatial light modulator shown in FIG. 7 to realize error correction, so that high-precision dynamic measurement can be realized.

本发明虽然以较佳实施例公开如上，但其并不是用来限定本发明，任何本领域技术人员在不脱离本发明的精神和范围内，都可以做出可能的变动和修改，因此本发明的保护范围应当以本发明权利要求所界定的范围为准。Although the present invention is disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection should be based on the scope defined by the claims of the present invention.

Claims (10)

Translated fromChinese

1.一种干涉测量装置，其特征在于包括，1. An interferometry device, characterized in that it comprises,用以产生偏振状态相互正交线偏振光的装置，该相互正交线偏振光分别称为参考光和测试光；means for generating mutually orthogonal linearly polarized light of polarization states, the mutually orthogonally linearly polarized light being referred to as reference light and test light, respectively;相位调制式空间光调制器，设置于参考光或测试光的光路中，用以改变光波前的空间相位分布；该空间光调制器具有复数个像素，每一像素具备特定的相位分布；其中，经所述空间光调制器相位调制后的光称为调制光，未经调制的光称为未调制光；The phase modulation spatial light modulator is arranged in the optical path of the reference light or the test light to change the spatial phase distribution of the light wavefront; the spatial light modulator has a plurality of pixels, and each pixel has a specific phase distribution; wherein, The light modulated by the spatial light modulator is called modulated light, and the unmodulated light is called unmodulated light;基于所述调制光和未调制光实现干涉测量的干涉仪；An interferometer for interferometry based on said modulated light and unmodulated light;对干涉仪产生的相干光探测的光探测装置，该光探测装置具备与所述空间光调制器相同的像素分布；且二者像素相对应。A light detection device for detecting coherent light generated by the interferometer, the light detection device has the same pixel distribution as that of the spatial light modulator; and the two pixels correspond to each other.2.根据权利要求1所述的干涉测量装置，其特征在于，所述空间光调制器为反射式液晶空间光调制器。2 . The interferometric device according to claim 1 , wherein the spatial light modulator is a reflective liquid crystal spatial light modulator.3.根据权利要求1所述的干涉测量装置，其特征在于，所述产生偏振状态相互正交线偏振光的装置包括共轴设置的线偏振光起偏器和偏振分光棱镜。3 . The interferometric device according to claim 1 , wherein the device for generating linearly polarized light with mutually orthogonal polarization states comprises a coaxially arranged linearly polarized light polarizer and a polarization beam splitter prism. 4 .4.根据权利要求3所述的干涉测量装置，其特征在于，所述产生偏振状态相互正交线偏振光的装置还进一步包括使偏振分光镜后的正交线偏振光产生相位延迟的结构。4 . The interferometric device according to claim 3 , wherein the device for generating mutually orthogonal linearly polarized light with polarization states further comprises a structure for causing phase delay in the orthogonally polarized light after the polarization beam splitter. 5 .5.根据权利要求3所述的干涉测量装置，其特征在于，液晶空间光调制器至少包括一组2×2分布的像素单元，且所述像素单元中每一像素具有不同的相位。5 . The interferometric device according to claim 3 , wherein the liquid crystal spatial light modulator comprises at least one group of pixel units distributed in 2×2, and each pixel in the pixel units has a different phase.6.根据权利要求5所述的干涉测量装置，其特征在于，所述每一像素单元中相位分布分别为0、π/2、π和3π/2。6 . The interferometric device according to claim 5 , wherein the phase distributions in each pixel unit are respectively 0, π/2, π and 3π/2.7.根据权利要求1所述的干涉测量装置，其特征在于，所述干涉仪为菲索干涉仪。7. The interferometry device according to claim 1, wherein the interferometer is a Fizeau interferometer.8.根据权利要求7所述的干涉测量装置，其特征在在于，还包括相干光源。8. The interferometric apparatus according to claim 7, further comprising a coherent light source.9.一种空间相移装置，其特征在于包括：沿准直光束照射方向依次设置的偏振器件和液晶空间光调制器，还包括用于对所述液晶空间光调制器相位调制的控制装置。9. A spatial phase shifting device, characterized by comprising: a polarizing device and a liquid crystal spatial light modulator arranged in sequence along the irradiation direction of the collimated light beam, and a control device for phase modulation of the liquid crystal spatial light modulator.10.一种液晶空间光调制器相位校正装置，其特征在于包括沿光轴依次设置的干涉仪、参考镜、偏振片和液晶空间光调制器。10. A liquid crystal spatial light modulator phase correction device, characterized in that it comprises an interferometer, a reference mirror, a polarizer and a liquid crystal spatial light modulator arranged in sequence along the optical axis.

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