Reflectance Transformation Imaging (RTI) is a computational photography technology that allows interactive manipulation of virtual lighting within two-dimensional images to enhance object surface information. RTI is based on the reflection characteristics of the surface of the object characterized by a specific parabolic function, of which the most classic is Polynomial Texture Mapping (PTM) based on biquadratic polynomial. Therefore, RTI is ideal for diffusely reflecting objects, and metal materials with specular reflection are nearly out of consideration before. In this article, several metal samples with different surface topography were selected to explore the potential of RTI for subtle traces on metal surfaces. The results show that, with the cooperation of different image enhancement algorithms, especially Specular Enhancement and Diffuse Gain, RTI can be well applied to the detection of metal, even metal with relatively strong specular reflection. And the No-Reference Structural Sharpness (NRSS) assessment is consistent with subjective perception, confirming that RTI not only helps to explore the 2D or 3D geometric texture of the surface of metal materials, but also plays an important role in understanding and spreading the cultural phenomena implied in the content on metal surfaces. Promisingly, RTI is expected to be extended to a wider range of fields.
Fast, accurate and high-quality extraction of trace information is important in the fields of criminal investigation, archaeology and inspection. Reflection transformation imaging is based on a digital photography and surface reflection imaging model, and can record and process the surface texture information of the object, thereby realizing a three-dimensional visual rendering image of the object. In different occasions, the objects carrying the traces are different in the type and color, and the dimensions, types, colors, etc. of the traces are also different. In order to make the different trace features clear, this paper builds a detection device based on the principle of reflection transformation imaging. LED used in the device has four colors: white, red, green and blue. Traces with different colors and types have different reflectivity for different wavelengths of illumination light, thus a high contrast trace image is achieved by using the device. And the device can render the image and get clear visibility of traces. The local histogram equalization algorithm is further used to extract edge information of the traces of different rendering effects, and the detail information of the trace image is further enhanced. This paper introduces a non-reference image evaluation function to evaluate the quality of the image. In this paper, the device is used to detect the traces written by colorless pen, colorless ballpoint pen, black pen and black ballpoint pen on the white paper. Then the device is used to detect traces written by different color water-based pen and oily-based pen on the white paper. Compared with monochromatic source illumination, the device can obtain higher contrast trace information according to the color and type of the trace. Furthermore, edge extraction of these rendered trace images makes the traces easier to identify. For different colors of papers and traces, the device can obtain high contrast images by selecting the appropriate illumination wavelength. Therefore, the device will have important application prospects in the fields of criminal investigation and ancient cultural relics identification.
Handwriting is a special kind of trace, which carries important information such as writing content, writing tools and writing habits. Reflection transform imaging (RTI) is a computational photography method that creates an interactive image to further display the 2D and 3D texture features of the inspection surface. In this paper, Reflection Transform Imaging is applied to study the colored and colorless handwriting traces produced by pen and water-based pen. By combining different lighting directions and rendering modes, not only the writing content of different handwriting traces can be obtained, but also the three-dimensional texture information of handwriting traces can be obtained. Especially for the colorless handwriting trace, the two-dimensional and three-dimensional texture of the handwriting detail features can reveal the differences between different writing tools and show the shape of the brush. The experimental results show that reflection transform imaging technique can clearly display the colored and colorless handwriting traces, and it can provide powerful help for the case detection by revealing various information hidden in the handwriting traces.
Latent fingerprint is one of the important evidences used to identify criminals in criminal cases, so fast and non-destructive detection of latent fingerprints is important. At present, the usual method always preprocess the sample before detecting the latent fingerprints, and it will cause a certain degree of damage to the latent fingerprints. Based on the characteristic that the organic components of latent fingerprints will produce the fluorescence when induced by ultraviolet, a fast, non-destructive and high-contrast detection technique is studied. In this paper, an ultraviolet induced fluorescence detection method based on two-dimensional laser scanning system is proposed to realize the rapid scanning of latent fingerprint area. The experimental parameters are optimized according to the contrast of fingerprint striae, the fingerprint image is reconstructed by image processing. In order to verify the feasibility of this method in practical application, the experiment of detecting the aged latent fingerprints on five kinds of papers deposed for different days is carried out. The detection results show that the aged latent fingerprints deposed for three days can be clearly visualized. For aged latent fingerprints deposed for five days and seven days, the contrast of fingerprint striae is reduced, but the fingerprints can still be distinguished. The method can realize fast, non-destructive and high-contrast detection of latent fingerprints on papers. It can be used in different fields such as criminal investigation and trace detection.
Beam stabilization system is one of the most important units for lithography, which can accomplish displacement and pointing detection and control and includes beam measurement unit(BMU) and beam steering unit(BSU). Our group has set up a beam stabilization system and verified preliminarily beam stabilization algorithm of precise control beam position and angle. In the article, we establish beam delivery mathematic model and analyze the system inherent error. This shows that the reason why image rotation effect arises at the output plane of beam stabilization is the fast steering mirror (FSM) rotation of BSU in the process of beam stabilization. Two FSMs rotation around 45o axis of FSM make the most contribution to image rotation which rotates 1.414 mrad as two FSMs rotation angle difference changes 1 mrad. It is found that error sources include three key points: FSM accuracy; measurement noise and beam translation by passing through of beam splitters changing as the ambient temperature changing. FSM accuracy leads to the maximum 13.2μm displacement error and 24.49μrad angle error. Measurement inaccuracy as a result of 5μm measurement noise results in the maximum 0.126mm displacement error and 57.2μrad angle error. Beam translation errors can be negligible if temperature is unchanged. We have achieved beam stability of about 15.5μrad for angle and 28μm for displacement (both 1σ) after correcting 2mm initial displacement deviation and 5mrad initial angle deviation with regard to the system rebuilt due to practical requirements.
Illumination uniformity is one of the key specifications of lithography illumination system because of its strong influence on the critical dimension (CD) uniformity in optical lithography. Refractive microlens array (MLA) has been extensively adopted in lithography system to achieve highly homogeneous illumination field with less light loss relative to diffractive element. Off-line homogenization inspection of the MLA provides important data for entire system integration. It is still a challenge work to investigate the optical performance for such high-end MLA with large clear aperture and high sensitivity to the incident light parameters. In order to address these issues, subaperture stitching method has been proposed to be applied and studied in this work. The feasibility of this method has been verified by theoretical simulation of a diffracting homogenizer. In the experiment, a corresponding optical setup is constructed, and a crossed-cylindrical single-plate MLA has been tested. The experimental results are consistent with the simulation ones. It could be concluded that subaperture stitching method is a powerful method to evaluate the homogeneous performance of MLA.
This paper introduces the design of a novel time-resolved fluorometer based on immunochromatograghy. Different from
the other time-resolved fluorometers, it tests the immunochromatographic strip which is labeled with lanthanide ions and
their chelates. This instrument can provide a rapid, quantitative measurement of analytes present in samples without any
washing steps and it can be used to carry out point-of-care test (POCT). The immunochromatograghy-based timeresolved
fluorometer is composed of a specific optical sensor, a scanning stage, a signal processing system and a
computer control system. The light from UV LED is focused on the test strip by a condense lens group in the optical
sensor. If the labels are present in samples, the fluorescence at 613nm will be exited (when Eu3+chelate is used for
marking substance). After a delay of some microseconds, the fluorescence will be collected by the optical sensor and
converted into electronic signal by a photomultiplier tube (PMT). The concentration of the sample can be calculated
through the standard working curve of this instrument. By testing, the sensitivity is several ng/ml level (when Eu3+chelate is used for marking substance), test linear range is from several ng/ml to 103 ng/ml, in which correlation
coefficient is 99.97%.
A novel biosensor based on up-converting phosphor technology (UPT) was developed several years ago. It is a kind
of optical biosensor using up-converting phosphor (UCP) particles as the biological marker. From then on, some
improvements have been made for this UPT-based biosensor.
The primary aspects of the improvement lie in the control system. On one hand, the hardware of the control system
has been optimized, including replacing two single chip microcomputers (SCM) with only one, the optimal design of the
keyboard interface circuit and the liquid crystal module (LCM) control circuit et al.. These result in lower power
consumption and higher reliability. On the other hand, a novel signal processing algorithm is proposed in this paper,
which can improve the automation and operating simplicity of the UPT-based biosensor.
It has proved to have high sensitivity (~ng/ml), high stability and good repeatability (CV<5%), which is better than
the former system. It can meet the need of some various applications such as rapid immunoassay, chemical and
biological detection and so on.
Gold labeled immunochromatography assay is widely used in many fields. Quantitative test can be realized by using a
reflectance photometer. However, theoretical analysis of the strip and the photometer has seldom been reported. In this
paper, the microstructure of immunochromatographic strip labeled by nanogold particles is analyzed with scanning
electron microscope (SEM). Based on the SEM images of the strip, Mie's scattering theory is used to investigate the
scattering behaviors of particles in the strip, and Lambert cosine law is applied to analyze the diffuse reflection of porous
strip. Besides, a reflectance photometer for gold labeled test strip has been developed for fast quantification of
immunochromatography assay in our group. Theoretical model is achieved by introducing the parameter of the
developed reflectance photometer. The calculated scattering signal distribution is well consistent with that measured by
the reflectance photometer.
A new generation of Up-converting phosphor technology-based biosensors (UPT-based biosensor) has been developed
for immunoassay, where a kind of novel Up-converting phosphor (UCP) particle serves as the biological marker. Its
control system is based on a micro-computer control unit instead of a personal computer, which results in low power
consumption, high reliability and portability for field detection. By detecting the content of the UCP on the test strip, the
system figures out the concentration of the biological molecular of interest, which can be used in field examination of
biological analytes. In this paper, a series concentration of standard samples have been tested by the biosensor, which is
proved to have higher sensitivity (~ng/ml), higher stability (CV<3~5%), better linear relationship and an excellent
correlation (R2≥0.95). The UPT-based biosensor has stable, reliable and sensitive performances. It can meet the need of
various rapid bioassay applications.
A method to measure displacements based on Moire technique and polarization modulation is presented and analyzed with Fourier transform and Jones matrix in this paper. A collimated laser beam illuminates a scale grating moved in the direction perpendicular to its groove. The scale grating is imaged on a two-phase index grating through a 4f system with an aperture in its frequency plane to form Moire fringes. The scale grating and the index grating have same grating period and their line and space ratio is 1:1. Two sections of the index grating are imaged on two parts of a bi-cell detector through a telecentric system, thereby the displacement of the scale grating can be obtained by detecting the Miore signals on the detector. Before the index grating, a polarizer and a Savart plate are placed. In the telecentric system, a photoelastic modulator between two quarter-wave plates and an analyzer are arranged. Thus the polarization modulation of the Moire signals is realized. The polarization modulation improves the measurement accuracy of the displacement. The analysis shows the displacement measuring method is of nanometer accuracy. In experiments, we verified the feasibility of the method. The repeatability of the method was less than 12nm.
The performance inspection of focusing optics, such as focusing lens and focusing assemblies, is of great importance in the machining of optical elements, alignment and regular maintenance of optical facilities. Currently, however the interferometric method and the knife-edge method used normally for the measurement of the large-aperture surface have limitations for the test in the large optical equipment. To solve the problems, a scanning Hartmann inspection apparatus based on the Hartmann principle for focusing optics performance test has been developed. In this paper, the experimental setup and test principle are described, experimental results and analysis are given, and the improvement plan further to obtain better test capability is briefly presented in the end.
An up-converting phosphor technology-based biosensor (UPT-based biosensor) has been developed for immunoassay using Up-converting phosphor (UCP) as the biological marker. The UPT system has realized quantitative detection and has good ability to meet the need of some emergencies. High sensitivity (nanogram/ml), good linear response characteristics and an excellent correlation (R2greater than or equal to 0.95) have been verified by quantitative detection results. The sensitivity of the UPT-based biosensor is better than that of the indirect hemagglutination test in the practical application. All the results are comparable with that obtained by Western Blot detection.