Based on the difference between theoretical with real interferogram images the figure of original aspheric surface can be
obtained using an algorithm of Reverse iterate Optimization Reconstruction (ROR) calculating technique. Because the
procedure of ray tracing path needed an accurate geometry of optical structure size so the aspheric and compensator LC must be located in the optical path. To avoid the compensator LC resulted in bigger spherical aberration a smart located method is proposed in this paper. Before measurement an aplanatic lens consists of compensator LC and another
removable lens LM that the last surface is a standard one. So Fiezau interference is formed by the standard one with reflected ray from the vertex of aspheric that the aspheric surface detected can be accurately located. At testing the
lenses LM will be removed and the aspheric is moved to an adapted position. The experiments show the displacement locating accuracy is an amount of micron. The RMS for aspheric testing of ROR calculating technique is better than 1/200 wavelength.
KEYWORDS: Aspheric lenses, Wavefronts, Interferometry, Sensors, Computer simulations, Beam splitters, Ray tracing, Digital cameras, Systems modeling, Nano opto mechanical systems
With respect to null test, non-null test is more flexible and can provide fast, general test with acceptable accuracy. A
non-null interferometric aspheric testing system, which employs partial null lens and reverse optimization
reconstruction, is proposed. The partial null lens compensates most of the longitude aberration of the aspheric under test
and keeps the slope of the non-null wavefront within the resolution of the detector. The reverse optimization
reconstruction procedure reduces the retrace error of the non-null test and reconstructs the figure of the test aspheric. The
characteristic, design process of the partial null lens and especially the implement of the reverse optimization
reconstruction are discussed in detail. Computer simulation shows the reverse optimization reconstruction procedure can
reconstruct the aspheric figure error with an accuracy better than 1/200wave within 5 mins. The error analysis is also
considered and some conclusions are given. This research is of great importance for general aspheric surfacing and testing.
This paper describes a novel synchronous control system of high speed imaging, which combines a common path
interferometer system modulated by the space phase. The system can continuously grab multiple frame interferograms,
which contain transient flow field distortion. The study of this system will provide a fire-new means for the research of
aerodynamics. The light source of the system is Nd: YLF semiconductor pump solid pulsed laser of which wavelength is
1053 nanometers. The laser pulse width is less than 30 nanoseconds, far less than the exposure time of the camera
shutter. Thus the laser pulse can freeze the flow field within several dozen nanoseconds and catch the biggish change of
turbulent flow. The pulsed laser beam containing the information of turbulent flow enters a cyclical radial shearing
interferometer. The emergent lights, being respectively contracted and expanded, re-combine and form fringe pattern in
high space frequency, modulated with a definite carrier frequency. The fringe pattern is formed on the high speed CMOS
camera at last. An accurate short time delay circuit is provided for synchronization matching of the pulsed laser and
camera exposure. The speed of image acquisition in full pixels with 1280×1024 can reach 450 frames per second. This
interferogram acquisition system with compact configuration and strong anti-disturbance capability, has successfully
grabbed clear transient interferograms that provided reliable image information for follow-up image processing and flow
field density calculating.
It is an important part to measure the distortion and divergence of laser pulse wavefront in ICF (Inertial Confinement Fusion). The paper described a radial shearing interference system with spatial phase modulation. It can be used for testing the wavefront distortion and control the beam quality. Because it is a cyclical common path interference system and no any reference surface, both radial sheared wavefront are formed by a Galilean optical system. A 512x512 pixels CCD camera recorded interference pattern. The wavefront reconstructed is finished by means of optical information processing method and software. The software procedure consists of the Fourier transform, shifting frequency, inverse Fourier transform, unwrapping 2π and wave iterations reconstructed. The interferometer has been used for testing a wavefront distortion of laser pulse with 1064nm near-infrared wavelength and 10 ns pulse time width. Results of the pulse wavefront quality and distribution of energy can be displayed by a perfect software procedure. Diameter of beam be measured is up to 150 mm. The testing precision of RMS(root-mean-square) is better than 1/15 wavelength.
VISAR is an effective tool to measure very high-speed motion objects. However, because of the limitation of response speed of the detector, it is unable to resolve the number of shifting fringes in
a very short time at the beginning of motion of the object, which lead to a question of fringe lost. The Double-sensitivity VISAR is one of ways to solve the question. In this article, we advance an
improved double-sensitivity VISAR that only uses a set of velocity interferometer and detection system.
The approximate Strehl Ratio expressions that need only the wave phase distribution is not appropriate in the laser fusion system when the phase has great aberration. The accurate Strehl Ratio value need both the phase and the amplitude distribution information. The paper provide a method of reconstructing wave phase and amplitude
distribution by a single radial shearing interferogram. The radial shearing interferometer based on spatial phase modulation is simple and stable, needs only one interferogram. The principle and structure of cyclic radial shearing interferometer are briefly discussed and the process of spatial phase modulation, Fourier transform method and wavefront reconstruction are analyzed. It also illluminates the physical meaning and establish the mathematical model. The process of getting SR value is simulated by computer. The simulation result indicates that the RMS error of the reconstructing wavefront can achieve λ/100.
The interferometer can measures accurately a static or dynamic wavefront . It can be done using a system of circular radial shearing interference with spatial phase modulated. Because the method only needs one frame interferogram so that can rejected the effect of vibrations and noises. The wavefront errors measured make adaptive optic system (AOS) that contain a deformable mirror correct the wavefront aberrations again. This paper described a system of radial shearing interference with spatial phase modulation. It is based on the Fourier transform method that the analysis and data processing of the interference fringe pattern with suitable linear carrier. An algorithm of shearing wavefront reconstructed can obtain the original wavefront. The system of diagnostics can check the operation of the AOS and quantify laser beam quality. Finally, the interference experiment and data processing results have been given in this paper.
The paper described a double-focus interference profiler, its characteristics as below: There isn't standard reference mirror in the instrument. Non-destructive testing is operated for surface. It will be valid for rejecting various noises using interference and electronic common-mode processing system. All measurements are carried out by computer then surface roughness parameters are displayed. The results are compared with commercial WYKO and identity is very well. The instrument is suitable for testing nanometer and sub-nanometer surface, especially soft materials and films. The instrument has a sensitivity to height of 0.1 nm and the lateral sensitivity 1 micrometers .
A new optical interferometer suitable for the scanning force microscope is presented in this paper. The cantilever itself is used as a micro interferometer element. The deflection of the cantilever is detected by the interference between the geometrical reflected wave and the backward diffracted wave. This interferometer has a very simple structure, fewer optical components, lower cost, and complete common light path. 0.01 nm vertical resolution is gotten by this instrument.
A novel double focus optical interferometer for scanning force microscope is presented in this paper. The deflection of the force sensing cantilever is measured by detecting the phase shift of two orthogonal polarized light beams reflected from the end of the cantilever and a reference plane with a hole in the center. We have tested some samples by using this instrument and gotten some high resolution pictures. The instrument provides 0.1 nm height resolution and 5 nm lateral resolution and is especially applicable in the profilometer of the integral circuit, fine grate, etc.
An optical non-contact profilometer is presented for in-process measurement of super-smooth surfaces, applying a common-path interferometer and signal correlation processing technique. Environmental disturbation and laser amplitude noise, which commonly exist in similar instruments are overcome in the system. The overall simplicity of the optics and electronics, the low cost of components and the ease of alignment make this a convenient system to implement.
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