A theoretical investigation of generalized grating imaging and its application to optical encoders

Ye, Guoyong; Li, Hongzhong; Fan, Shanjin; Li, Xuan; Yu, Haoyu; Lei, Biao; Shi, Yongsheng; Yin, Lei; Lu, Bingheng

doi:10.1016/j.optcom.2015.05.023

Cited by 16 publications

(7 citation statements)

References 23 publications

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“…Figure 1(b) shows the schematic diagram for illustrating the formation of the grating image. As we have derived in pre vious work [19], the grating image with maximum contrast can be achieved when the parameters shown in figure 1(b) sat isfy the following equations…”

Section: Operating Principle Of Optical Encoder Based On Generalized ...mentioning

confidence: 96%

“…The divergent light beam from an infrared LED illu minates the index grating firstly. Then the light is diffracted by the scale grating, and the interference of the diffraction beams would result in a grating image (interference fringes pattern) according to generalized grating imaging [3,18,19]. Figure 1(b) shows the schematic diagram for illustrating the formation of the grating image.…”

Section: Operating Principle Of Optical Encoder Based On Generalized ...mentioning

confidence: 99%

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Optimizing design of an optical encoder based on generalized grating imaging

Shi

et al. 2016

Meas. Sci. Technol.

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The interpolation error of an optical encoder is largely determined by the imperfections in the electrical signals, such as amplitude error, phaseshift error, DC error and higher harmonic distortion. In this paper, an optimized optical encoder based on generalized grating imaging is presented. We first describe the basic principle and configuration of the optical encoder. To achieve four electrical signals with equal amplitudes, equal DC contents and accurate 90° electrically phaseshift, a photodiodes array is adopted as the photodetector. The photodiodes array offers the advantage of singlefield scanning. Then, to solve the remaining problem of higher harmonic distortion, a slitwidthmodulated index grating is proposed to suppress the dominant third order and fifth order harmonics simultaneously, and the cell's width of the photodiodes array is optimized to further reduce the fifth order harmonic. Experiments have been carried out to verify the theoretical results. The feasibility and effectiveness of the proposed optimizing methods have been confirmed from the experimental results.

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Section: Operating Principle Of Optical Encoder Based On Generalized ...mentioning

confidence: 96%

Section: Operating Principle Of Optical Encoder Based On Generalized ...mentioning

confidence: 99%

Optimizing design of an optical encoder based on generalized grating imaging

Shi

et al. 2016

Meas. Sci. Technol.

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“…Optical linear encoders use various types of optical-scanning principles (e.g., Talbot effect [46,47], Lau effect [48,49], Moiré effect [50][51][52], generalized grating imaging [53][54][55][56], interferometric [57][58][59]) to generate electric-output signals that are used to determine a precise position. Depending on subsequently used electronics, optical encoders can have different interfaces to ensure the reliable exchange of information [60].…”

Section: Metrological Process and Subdivisional Errors In Optical Encmentioning

confidence: 99%

Experimental Investigation of Linear Encoder’s Subdivisional Errors under Different Scanning Speeds

2020

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Optical encoders are widely used in applications requiring precise displacement measurement and fluent motion control. To reach high positioning accuracy and repeatability, and to create a more stable speed-control loop, essential attention must be directed to the subdivisional error (SDE) of the used encoder. This error influences the interpolation process and restricts the ability to achieve a high resolution. The SDE could be caused by various factors, such as the particular design of the reading head and the optical scanning principle, quality of the measuring scale, any kind of relative orientation changes between the optical components caused by mechanical vibrations or deformations, or scanning speed. If the distorted analog signals are not corrected before interpolation, it is very important to know the limitations of the used encoder. The methodology described in this paper could be used to determine the magnitude of an SDE and its trend. This method is based on a constant-speed test and does not require high-accuracy reference. The performed experimental investigation of the standard optical linear encoder SDE under different scanning speeds revealed the linear relationship between the tested encoder’s traversing velocity and the error value. A more detailed investigation of the obtained results was done on the basis of fast Fourier transformation (FFT) to understand the physical nature of the SDE, and to consider how to improve the performance of the encoder.

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“…A generalized grating imaging configuration based optical encoder was adopted here, because optical encoders based on this configuration are more compact and robust [12,28]. A reading head is developed based on our previous work [29,30]. This was fixed at the moving bridge of a high precision long travelling aerostatic stage, and the scale gratings were mounted in parallel with the moving direction of it.…”

Section: Comparison Test Of Photoelectric Signals and Position Error ...mentioning

confidence: 99%

Fabrication of high-resolution reflective scale grating for an optical encoder using a patterned self-assembly process

Fan¹,

Jiang²,

Li³

et al. 2016

J. Micromech. Microeng.

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Steel tape scale grating of a reflective incremental linear encoder has a key impact on the measurement accuracy of the optical encoder. However, it is difficult for conventional manufacturing processes to fabricate scale grating with high-resolution grating strips, due to process and material problems. In this paper, self-assembly technology was employed to fabricate high-resolution steel tape scale grating for a reflective incremental linear encoder. Graphene oxide nanoparticles were adopted to form anti-reflective grating strips of steel tape scale grating. They were deposited in the tape, which had a hydrophobic and hydrophilic grating pattern when the dispersion of the nanoparticles evaporated. A standard lift-off process was employed to fabricate the hydrophobic grating strips on the steel tape. Simultaneously, the steel tape itself presents a hydrophilic property. The hydrophobic and hydrophilic grating pattern was thus obtained. In this study, octafluorocyclobutane was used to prepare the hydrophobic grating strips, due to its hydrophobic property. High-resolution graphene oxide steel tape scale grating with a pitch of 20 μm was obtained through the self-assembly process. The photoelectric signals of the optical encoder containing the graphene oxide scale grating and conventional scale grating were tested under the same conditions. Comparison test results showed that the graphene oxide scale grating has a better performance in its amplitude and harmonic components than that of the conventional steel tape scale. A comparison experiment of position errors was also conducted, demonstrating an improvement in the positioning error of the graphene oxide scale grating. The comparison results demonstrated the applicability of the proposed self-assembly process to fabricate high-resolution graphene oxide scale grating for a reflective incremental linear encoder.

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A theoretical investigation of generalized grating imaging and its application to optical encoders

Cited by 16 publications

References 23 publications

Optimizing design of an optical encoder based on generalized grating imaging

Optimizing design of an optical encoder based on generalized grating imaging

Experimental Investigation of Linear Encoder’s Subdivisional Errors under Different Scanning Speeds

Fabrication of high-resolution reflective scale grating for an optical encoder using a patterned self-assembly process

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