In order to utilize the LCoS, this paper advances a new patten liquid material which is ferroelectric liquid crystal. It has
the characteristics, such as time division-style full-color display, high resolution, low voltage and high speed response. If
it is used in the microdisplay, we can attain large area visual display, high open rate and high responding time. The
alignment of ferroelectric liquid crystal is very complicated, so we use photo-alignment, rubbing or hybrid-alignment to
determine the direction of liquid. Once the liquid layer has been fabricated, we use space parameter method to analyse
the liquid layer, and we make sure the detailed optical thickness and pretilted angle.
A two-dimensional system model, including the birefringent low-pass filter (BLF), was designed and a cost function was formulated. This model takes optical system into account in designing BLF. Optimization of the parameter of BLF is acquired by this new method. Best performance of BLF is realized when distance d of o light and e light is about half size of a pixel. Moreover, the relation between the optimized distance d and the cutoff frequency of ideal optical system was established. It is proved that the optimized distance d becomes smaller when the cutoff frequency of optical system increases.
The graduator is a very important standard device in the optical angular measuring instrument, which determines the
measure precision of the measuring instrument. A new graduator test method is discussed in this paper.
This test method is a dual dynamic imaging measurement method with dual digital microscope system, which acquires
the images of the graduator rotated by a rotating motor.
Here is the introduction of this method with more detail. At first, fix a graduator to be measured on a rotary stage, this
stage will be driven by a high precision programmable motor. Make the stage rotate with a constant angular velocity ω.
Then place the digital microscope system upon the graduator. The digital microscope system includes two digital
microscopes, which placed in the opposite diameter direction. Each digital microscope is made up of optical lens and a
CMOS electro-ocular. The sampling frequency f can be set in the control software of the elector-ocular. The two digital
microscopes make up a dual dynamic image acquire system. This system can acquire two images of the moving
graduator at the same time with the sampling frequency f. Then, a serial of the graduator images can be acquired after a
period of rotation, and there is a constant angular difference ω/f between every adjacent image. Each image of the
graduator includes several graduation lines, identify these lines and get the position of the lines with image processing
method. The measuring value of the rotate angle can be calculated from the adjacent line positions. Use the angular
difference ω/f as a standard value of the rotate angle. Compare the measuring value and the standard value with the
"comparing method of graduator measurement" formula. A compare result will be given to judge the graduator is good or
not at last.
The whole system is divided into four functional units: 1,the motion control unit;2,the dual dynamic imaging unit; 3, the
image processing unit; 4,the data analysis unit.
The measurement principle is introduced in the first part of the paper. In this part, the background of graduator
measurement and the theories of graduator measurement are referred. According to the measurement principle a system
design is made in the second part of the paper. In this part, the whole measure system is described: the structure of the
system, the function of each component and the specifications for the key components. An experiment system is build up
under the design, and some measurement data is obtained, the error analyses of the measure data is given at the last of
Two-dimensional optical low pass filter (OLPF) was designed, fabricated and tested in our lab. The modulation transfer function (MTF) of OLPF shows that cut-off frequency is 96.15lp/mm in x and y direction, which is satisfied with our design. The transmissions in the visible and infrared regions of the spectrum are mostly above 95% and less than 2%, respectively. The error of every plate thickness is tested less than 0.34% by the experiment of pulse response. The spatial frequency test results show that our device has good low filter performance, matches with the solid state image sensor and well restrains the moire effect and false colors distortion.
A new photoelectric model of silicon based position sensitive detector (PSD) is built and the formulas of the photocurrent and spectral response are got with it. The effect of every layer thickness and SiO<sub>2</sub> thickness to the spectral response is analysis and calculation. The spectral response of PSD is affected by the thickness of p layer mainly at short wavelength and by the thickness of the depletion layer mainly at long wavelength. With the results, a new silicon based near infrared two dimensional pincushion PSD is designed and fabricated. Some necessary tests show that the peak spectral sensitivity of our device is 0.626A/W at 920nm wavelength.
Implementation of a 4 by 1 comb-type Position sensitive detector (PSD) array for position sensing applications is presented. Unlike conventional application, we utilize the method of subdivision to increase the resolution of PSD beyond the feature of photosensitive area, which is presented periodically. To obtain output signal of comb-type PSD, classic grating subdivision circuit is used. Resolution of 6.25μm of comb-type PSD is achieved using optical grating array of a 50μm in pitch and signal power of 3mW. The resolution is limited by the spacing of comb-type PSD and the mismatch of position of PSD array and optical grating array.
A new edge detection method based on nonlinear fitting is used in the measurement of the curvature of lens in this paper. Non-contact Newton's rings are formed by an interferometer. In order to detect the diameters of dark rings and calculate the lens radius of curvature, the edge detection method is used for the image process. The auto-measuring system of lens curvature captures the gray scale image by CMOS image sensor, and then processes the data and calculates the position by a microprocessor. The scale of image pixels corresponding to Newton's rings that are related to the radius of curvature is obtained by scanning fringes or other optical methods. The accuracy of measurement is better than 0.3 percent.
A digitalization measurement method of structure parameters of optical low-pass filter (OLPF) is presented in this paper. OLPF which comprises two or three crystal plates is adopted in front of the CCD to reduce aliasing in a digitized image. Transiting a triple plate OLPF, an object of the point-source light can separate into eight points which are imaged in CMOS array. The distance of point to point provides us with the information of thickness of each crystal plate. The accuracy of measurement is better than 0.15μm.
The fabrication and testing results of a 65-pin ceramic packaged 4×4 arrayed position sensitive detector are presented. The detector, consisting of 16 tetra-lateral sensitive areas, is a p-n-n+ configuration made on 3-in. 111 n-type high resistance crystal silicon substrates. A 100-nm antireflection SiO2 thin film is formed on the surface, along with a multilayer cover glass with transmissivity >98% from 400 to 950 nm. Primary tests of the device show that it has a low dark current, high spectral sensitivity, very fast response speed, and very good linearity. The dark current of an element unit is less than 20 nA, which is the allowable maximum dark current. The peak spectral sensitivity of the sensor is over 505 mA/W at 800-nm wavelength. Its response time is 8 ns at 45-V reverse bias and the nonlinearity of the total sensitive area is less than 1%.
Position sensitive detectors (PSD) use the lateral photo effect to determine the centroid position of an incident light spot focused on it. A 65-pin ceramic packaged 4×4 arrayed position sensitive detector was fabricated first time as a new prototype of Hartmann-Shack wavefront sensor. The detector, consisting of 16 tetra-lateral sensitive areas, is a p-n-n+ configuration made on 3-inch <111> n-type high resistance crystal silicon substrate. A 100nm antireflection SiO<sub>2</sub> thin film was formed on the surface and a multi-layer cover glass with transmissivity > 98% from 400nm to 950nm. The main parameters of the arrayed as wavefront detector, such as reverse voltage, dark current photosensitivity, response time were reported in the paper.
Position Sensitive Detector (PSD) is a position sensor utilizing the lateral photoelectric effect produced by the non-uniform illumination of a rectifying semiconductor junction. Recently, mostly researches of PSD focus on the linear requirements or response characters of PSD with p-n junction. However, this paper concentrates on a novel characteristics of PSD based on the Schottky junction. This junction has many distinguished traits comparing with the p-n junction. Since the intrinsic excellent characteristics, the Schottky PSD has faster response and higher sensitivity to the incident radiation, lager current density, low current leakage and so on. This paper provides an analysis and model of the Schottky-barrier PSD lateral potential creation, response characteristic and position linearity condition with the Schottky junction, which is deduced by the charge conversation law and the model of carriers transport. All the study work is the theoretical basis for design of this junction with better performance.
This paper represents the testing of grating spectral intensity distribution and describes the testing of semi-split beam
grating of DVD. Then some methods to improve the stability of the data are introduced.
Optical low pass filter (OLPF) made of artificial crystal is demonstrated. From the view of 1-D, 2-D, 3-D crystal’s filter
and gratings filter, the design of relative parameters and the influence of processing are discussed..
In variation calculus, the Fermat’ s theory is similar to the Hamilton’ s theory except that Hamilton’ s theory uses time as the independent variable to achieve minimum of a function while Fermat’ s theory uses space as the independent variable1. That is one of the essential differences between dynamics and optics. When time
coordinate t in dynamics is substituted by space coordinate z, and generalized momentum is introduced, optics is obviously similar to dynamics. Thus, we can use corresponding quantum mechanics methods to
handle similar phenomena in optics. First, in this paper, the concept of potential energy of Hamilton operator is introduced. Based on this, the law of energy minimization of a system, which is composed of two parallel waveguide, is used to deal with the transverse coupling between them. A more understandable result is gotten
and the comparison between the results of classical electromagnetic methods is discussed.
Position Sensitive Detector (PSD) is a device utilizing the lateral photoelectric that produced by the non-uniform illumination of a rectifying semiconductor junction. The linear requirement, spectral responds, position detection error of 1D PSD were presented in this paper. All these studied works are the theoretical basis for designing and fabrication PSD with excellent performance. The experimental results show that the rms non-linearity and the typcial position error are 0.1% of full length (8 mm) and ±5μm.
The performance parameter of 2D Position Sensitive Detector (PSD) are analyzed and calculated theoretically. The non-linearity and distortion grid map of the theoretical calculation using this structure position formula are in good agreement with the experimental result. The experimental results show that with the signal processor, the position non-linearity (rms) is less than 0.15% in the 60% range of a 13 mm x 13 mm active area, the position error is less than ±20 μm. It has demonstrated that 2D PSD was obtained the best position non-linearity results of 13 mm x 13 mm.
Because massive amounts of various information from embedded fiber sensors in composite are required to intelligently monitor the integrity and health of the structure, smart structures face the challenge of signal processing in future applications. In this paper, we give our studies on the processing of signals from polarimetric fiber sensors to assess strain distribution by an improved optical Hopfield neural network.