High-accuracy single F-P plate angular displacement measurement instrument

A displacement measurement, high-precision technology, applied in the field of high-precision single F-P plate angular displacement measuring instrument, can solve the problem of difficult high-precision angular displacement measurement, and achieve the effects of improving measurement accuracy, reducing measurement errors, and enhancing anti-interference ability.

Inactive Publication Date: 2004-07-28
SHANGHAI INST OF OPTICS & FINE MECHANICS CHINESE ACAD OF SCI
0 Cites 4 Cited by

AI-Extracted Technical Summary

Problems solved by technology

However, it is difficult to use F-P plate interference t...
the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
View more

Abstract

The present invention relates to a high-accuracy single F-P plate angular displacement measuring instrument. It includes modudation light source with drive power supply, on the forward direction of light-beam sent out by modulation light source a high-beam collimating objective lens and a reflector, and on the forward direction of reflecting light-beam of reflector a body to be tested in set, and on the formward direction of the reflecting light of the body to be tested a F-P plate and a beam splitter is set, and a lens and a photoelectric converting element are set on the direction of the light-beam transmitted from port 6 of light splitter, the photoelectric converting element is connected with A/D conversion element connected with computer, and on the direction of light-beam reflected by port C of light splitter a CCD image detector is set, and said CCD image detector is connected with A/D conversion element connected with computer.

Application Domain

Technology Topic

Image detectorBeam direction +8

Image

  • High-accuracy single F-P plate angular displacement measurement instrument
  • High-accuracy single F-P plate angular displacement measurement instrument
  • High-accuracy single F-P plate angular displacement measurement instrument

Examples

  • Experimental program(1)

Example Embodiment

[0019] Please refer to FIG. 1, which is a schematic diagram of the structure of the high-precision single F-P plate angular displacement measuring instrument of the present invention. The high-precision single FP plate angular displacement measuring instrument of the present invention includes: a modulated light source 2 with a driving power source 1, a beam collimating objective lens 3 and a reflecting mirror 4 are arranged along the forward direction of the light beam emitted by the modulated light source 2 The object 5 to be measured is placed in the forward direction of the reflected light beam of the mirror 4. An F-P plate 6 and a beam splitter 7 are arranged in the forward direction of the reflected light of the object 5 to be measured. A lens 8 and a photoelectric conversion element 9 are arranged in the direction of the transmitted light beam at the port b of the beam splitter 7. The photoelectric conversion element 9 is connected to the analog-to-digital conversion element 10 connected to the computer 13. A photoelectric conversion element 11 is arranged in the direction of the reflected light beam at the port c of the beam splitter 7, and the photoelectric conversion element 11 is connected to the analog-to-digital conversion element 12 connected to the computer 13.
[0020] The modulated light source 2 mentioned above is a semiconductor laser (also called a laser diode, or LD for short).
[0021] The driving power supply 1 provides DC and sinusoidal AC signals to the modulated light source 2.
[0022] The photoelectric conversion element 9 is a photodiode, a photovoltaic cell, or the like.
[0023] The photoelectric conversion element 11 is a CCD image detector.
[0024] The beam splitter 7 refers to an element capable of splitting the incident light into two beams at a light intensity ratio close to 1:1. Such as light splitting prisms, parallel plates coated with light-separating film and anti-reflection film on both sides, etc.
[0025] The F-P plate 6 is a transparent flat plate with two parallel sides.
[0026] The measured object 5 refers to an optical surface that produces angular displacement, such as a mirror surface, a silicon wafer surface, a metal surface, and so on.
[0027] The specific working process of the high-precision single FP plate angular displacement measuring instrument of the present invention is: the light emitted by the modulated light source 2 with the driving power supply 1 passes through the collimating objective lens 3 and is reflected by the reflector 4 to the measured object 5, and the measured object 5 reflects The beam of light irradiates the beam splitter 7 through the FP plate 6. The beam splitter 7 divides the incident light into reflected light and transmitted light. The reflected light is emitted from the port c of the beam splitter 7 to the photoelectric conversion element 11. The electrical signal output by the photoelectric conversion element 11 is converted into a digital signal by the analog-to-digital conversion element 12 and then enters the computer 13; the port b of the beam splitter 7 exits The transmitted light is condensed by the lens 8 to the photoelectric conversion element 9, and the electrical signal output by the photoelectric conversion element 9 is converted into a digital signal by the analog-to-digital conversion element 10 and enters the computer 13.
[0028] When the photoelectric conversion element 9 detects the interference signal
[0029] s(t)=cos(zcos(ωt+θ)+α), (1)
[0030] Where s(t) is the interference signal generated by the two beams formed by the beam passing through the F-P plate 6. z is the phase modulation amplitude of the interference signal s(t), ω is the frequency of the sinusoidal phase modulation signal of the driving power supply 1, t is time, and α is the phase change of the interference signal s(t) caused by the rotation of the object 5 to be measured. Take the initial phase of α as zero
[0031] α = 4 πnh λ [ cos i 1 - cos ( i 1 + 2 iΔ ′ ) ] . - - - - - - ( 2 )
[0032] Where λ is the center wavelength of light source 2. n and h are the refractive index and the distance between the upper and lower surfaces of the F-P plate 6 respectively. i 1 Is the refraction angle in the F-P plate corresponding to the initial incident angle i, i 1 +Δi' is the angle of refraction in the F-P plate corresponding to the incident angle i+Δi. see figure 2. From the formula (2)
[0033] Δi ′ = α ( 4 πnh / λ ) sin i 1 . - - - - - - - - ( 3 )
[0034] The angular displacement δ of the measured object 5 can be obtained by the following formula
[0035] δ = Δ i ′ 2 1 - sin 2 i 1 1 - n 2 sin 2 i 1 = α ( 8 πh / λ ) sin i 1 1 - sin 2 i 1 1 - n 2 sin 2 i 1 . - - - - - - - ( 4 )
[0036] (4) Sini in the formula 1 There is the following relationship with the horizontal distance d between the two beams of light transmitted from the F-P plate 6:
[0037] sin i 1 = { [ ( 1 + d 2 4 h 2 ) + ( 1 + d 2 4 h 2 ) 2 - 4 n 2 d 2 4 h 2 ] / ( 2 2 ) } 1 / 2 . - - - - - - - ( 5 )
[0038] The light emitted by the modulated light source 2 with the driving power supply 1 passes through the collimating objective lens 3 and is reflected by the reflector 4 to the measured object 5, and the light beam reflected by the measured object 5 is divided into two beams by the F-P plate 6 to cause interference. The interference light irradiated on the beam splitter 7 is divided into two paths of transmitted light and reflected light. The transmitted light is condensed by the lens 8 to the photoelectric conversion element 9. The analog-to-digital conversion element 10 converts the interference signal s(t) detected by the photoelectric conversion element 9 into a digital signal and inputs it into a computer for processing. Analysis can get α. The reflected light from the beam splitter 7 irradiates the photoelectric conversion element 11, and the analog-digital conversion element 12 converts the light intensity distribution signal detected by the photoelectric conversion element 11 into a digital signal, which is input to the computer for information processing to obtain the d value. n and h are the parameters of the F-P board 6, which are substituted into equation (5) together with d to obtain sini. Substituting α and sini and instrument parameters λ, n and h into equation (4) can obtain the angular displacement of the measured object 5.
[0039] If the wavelength of the modulated light source 2 is selected to be 661 nm, the refractive index and thickness of the F-P plate 6 are 1.5163 and 12 mm, respectively. Since the sinusoidal phase modulation method is used to measure the phase change α of the interference signal, the measurement resolution is above 0.01rad. Substituting the above data into equation (4), it can be obtained that the measurement resolution of angular displacement δ is 10 -8 rad order of magnitude.
[0040] The high-precision single F-P plate angular displacement measuring instrument of the present invention can be used to measure the angular displacement of a rotating object.
[0041]Figure 1 is the structure of the high-precision single F-P plate angular displacement measuring instrument of the present invention. Among them, the modulated light source 2 uses a single-mode semiconductor laser with a center wavelength of 661 nm. Driven by the DC and AC signals provided by the driving power supply 1, the emitted light passes through the collimating objective lens 3 and is reflected by the reflector 4 to the measured object 5, and the light beam reflected by the measured object 5 is divided into two beams by the FP plate 6 to cause interference . The F-P plate 6 is a glass plate with two sides highly parallel, and its surface is coated with a 90% anti-reflection film at a wavelength of 661 nm, and its refractive index and thickness are 1.5163 and 12 mm, respectively. The interference light irradiated on the beam splitter 7 is divided into two paths of transmitted light and reflected light. The beam splitter 7 adopts a parallel flat plate with a light-reducing film and an anti-reflection film on both sides. The transmitted light is condensed by the lens 8 to the photoelectric conversion element 9, and the photoelectric conversion element 9 is a photodiode. The analog-to-digital conversion element 10 converts the interference signal s(t) detected by the photoelectric conversion element 9 into a digital signal to be input to a computer for processing, and α can be obtained by performing spectrum analysis on s(t). The reflected light from the beam splitter 7 irradiates the photoelectric conversion element 11, which is a CCD image detector. The analog-to-digital conversion element 12 converts the light intensity distribution signal detected by the photoelectric conversion element 11 into a digital signal and inputs it to the computer 13 for processing. We can obtain d. n and h are the parameters of the F-P board 6, which are substituted into equation (5) together with d to obtain sini. Substituting α and sini and parameters λ, n and h into equation (4) can obtain the angular displacement of the measured object 5. Its measurement resolution is 10 -8 rad order of magnitude.
[0042] The trial shows that the present invention has the following advantages:
[0043] 1. The invention uses CCD to detect the center distance of the two transmitted beam spots of the F-P plate, and obtains the initial angle of the incident light through simple calculations. It solves one of the difficult problems of using F-P plate interferometry to measure angular displacement, that is, the problem of determining the initial angle of incident light.
[0044] 2. The single F-P plate sinusoidal phase modulation laser interferometer of the present invention has a simple structure and can perform high-precision angular displacement measurement.
[0045] 3. Compared with the prior art [1], the present invention uses sinusoidal phase modulation interferometry to measure the angular displacement of the object by measuring the phase of the interference signal, which enhances the anti-interference ability of the instrument against stray light and reduces the measurement error of the instrument , Improve the measurement accuracy of the instrument.
the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to view more

PUM

no PUM

Description & Claims & Application Information

We can also present the details of the Description, Claims and Application information to help users get a comprehensive understanding of the technical details of the patent, such as background art, summary of invention, brief description of drawings, description of embodiments, and other original content. On the other hand, users can also determine the specific scope of protection of the technology through the list of claims; as well as understand the changes in the life cycle of the technology with the presentation of the patent timeline. Login to view more.
the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to view more

Similar technology patents

Classification and recommendation of technical efficacy words

  • Simple structure
  • Improve anti-interference ability

Microlithographic projection exposure apparatus

InactiveUS20050068499A1Simple structureReliable and low-maintenance operationProjectorsPhotomechanical exposure apparatusCamera lensPhysics
Owner:CARL ZEISS SMT GMBH
Who we serve
  • R&D Engineer
  • R&D Manager
  • IP Professional
Why Eureka
  • Industry Leading Data Capabilities
  • Powerful AI technology
  • Patent DNA Extraction
Social media
Try Eureka
PatSnap group products