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.
A polarizer-compensator-sample-analyzer (PCSA) imaging ellipsometer with large field of view is presented. The sample is imaged on a CCD sensor by a telecentric imaging system and its tilt is monitored by an optical autocollimator. The sample, the telecentric imaging system and the CCD sensor satisfy the Scheimpflug condition. In measurement, the light extinction measurement method and the four quadrants average method are used to improve the accuracy. In experiments, a chromium thin film sample is measured by the imaging ellipsometer and a spectroscopic ellipsometer. The measurement results by two ellipsometers are consistent. The usefulness of the imaging ellipsometer is verified.
The step-and-scan lithographic illumination system has a scanning slit which could not only control the exposure field size but also assist the wafer to complete scanning process with high uniformity. The scanning slit is comprised by four blades which are drive by four electric actuators. This paper presents a 193nm lithographic illumination system without utilizing scanning slit. A microlens array, a micromirror array and a collimating lens are used to generated a certain intensity distribution on the surface of the aperture array. A fast scanning mirror is used in to change the position of the formed intensity distribution to change the illuniated area on the mask. That can realize lithographic scanning process without slit.
For the projection lithography, off-axis illumination has become one important resolution enhancement technique, which can also increase the depth of focus. It is realized by the pupil shaping unit to change the partial coherence factor. The pupil shaping unit is composed of a zoom system, diffractive optical elements (DOE) and axicons. By changing the focal length of the zoom system, a continuously adjustable diameter of the pupil is achieved. For the zoom system, its front focal plane and the back focal plane must be fixed and the telecentricity should be maintained in the process of zoom. In this paper, a zoom system with a zoom ratio of eight is designed. The system comprises only five lenses. The first lens works as the front fixed group and the last lens works as the back fixed group. The second lens is the zoom group to achieve the desired focal length, while the third and fourth lenses constitute the compensatory group to compensate the image shift. To eliminate the aberrations and obtain a compact structure, these five lenses are aspherical lenses. By using the multi-configuration design of ZEMAX software, the system is optimized to have a high imaging quality. Under the working wavelength of 193.368nm, the modulation transfer function is close to the diffraction limit. With this zoom system, the pupil shaping unit is simulated using ASAP software. The simulation results show that this zoom system can meet the requirement of pupil shaping of the lithography tool.
An illuminator with a micro scanning slit array for NA 0.75 lithography system has been proposed in this paper. In this illuminator, the beam is shaped by a diffractive optical element (DOE), a zoom and axicon lenses. The beam is homogenized by a micro intergrator rod array. The micro scanning slit array is used to substitute for the traditional internal rema. A micro lens array and a condenser image the micro scanning slit array onto the mask. This illuminator needs no illumination lens group and reduces the effect of the vibration introduced by the internal rema. The illuminator is designed and simulated. The result shows that the illuminating field on the mask has good uniformity and trapezoidal distribution along the scanning direction. The feasibility of the illuminator is verified.