The research of the multifunctional analyzer which integrates absorbance detection, fluorescence detection, time-resolved fluorescence detection, biochemical luminescence detection methods, can make efficient detection and analysis for a variety of human body nutrients. This article focuses on the absorbance detection and fluorescence detection system. The two systems are modular in design and controlled by embedded system, to achieve automatic measurement according to user settings. In the optical path design, the application of confocal design can improve the optical signal acquisition capability, and reduce the interference. A photon counter is used for detection, and a high performance counter module is designed to measure the output of photon counter. In the experiment, we use neutral density filters and potassium dichromate solution to test the absorbance detection system, and use fluorescein isothiocyanate（FITC）for fluorescence detection system performance test. The experimental results show that the absorbance detection system has a detection range of 0~4OD, and has good linearity in the detection range, while the fluorescence detection system has a high sensitivity of 1pmol/L concentration.
Automatic eyeglass lens edging system is now widely used to automatically cut and polish the uncut lens based on the spectacle frame shape data which is obtained from the spectacle frame measuring machine installed on the system. The conventional approach to acquire the frame shape data works in the contact scanning mode with a probe tracing around the groove contour of the spectacle frame which requires a sophisticated mechanical and numerical control system. In this paper, a novel non-contact optical measuring method based on structured light to measure the three dimensional (3D) data of the spectacle frame is proposed. First we focus on the processing approach solving the problem of deterioration of the structured light stripes caused by intense specular reflection on the frame surface. The techniques of bright-dark bi-level fringe projecting, multiple exposuring and high dynamic range imaging are introduced to obtain a high-quality image of structured light stripes. Then, the Gamma transform and median filtering are applied to enhance image contrast. In order to get rid of background noise from the image and extract the region of interest (ROI), an auxiliary lighting system of special design is utilized to help effectively distinguish between the object and the background. In addition, a morphological method with specific morphological structure-elements is adopted to remove noise between stripes and boundary of the spectacle frame. By further fringe center extraction and depth information acquisition through the method of look-up table, the 3D shape of the spectacle frame is recovered.
Known disparity search range is a crucial parameter for many stereo matching algorithms. It is necessary to estimate the disparity search range automatically in real time systems. In this work, we present an approach to estimate disparity search range of each pixel to be matched. A dual-mode camera which can be used to take stereo images or coarse depth maps is developed in our work. Under the constraint of the coarse depth map with the same spatial resolution as the stereo pairs, expected disparity of each pixel is limited within a narrow search range. We demonstrate the effectiveness of the proposed approach on benchmark images with ground truth as well as on images captured in our lab.
The Raman spectrum technology is widely used for it can identify various types of molecular structure and material. The portable Raman spectrometer has become a hot direction of the spectrometer development nowadays for its convenience in handheld operation and real-time detection which is superior to traditional Raman spectrometer with heavy weight and bulky size. But there is still a gap for its measurement sensitivity between portable and traditional devices.
However, portable Raman Spectrometer with Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy (SHINERS) technology can enhance the Raman signal significantly by several orders of magnitude, giving consideration in both measurement sensitivity and mobility. This paper proposed a design and implementation of driver and digital circuit for high accuracy CCD sensor, which is core part of portable spectrometer. The main target of the whole design is to reduce the dark current generation rate and increase signal sensitivity during the long integration time, and in the weak signal environment. In this case, we use back-thinned CCD image sensor from Hamamatsu Corporation with high sensitivity, low noise and large dynamic range. In order to maximize this CCD sensor’s performance and minimize the whole size of the device simultaneously to achieve the project indicators, we delicately designed a peripheral circuit for the CCD sensor. The design is mainly composed with multi-voltage circuit, sequential generation circuit, driving circuit and A/D transition parts. As the most important power supply circuit, the multi-voltage circuits with 12 independent voltages are designed with reference power supply IC and set to specified voltage value by the amplifier making up the low-pass filter, which allows the user to obtain a highly stable and accurate voltage with low noise. What’s more, to make our design easy to debug, CPLD is selected to generate sequential signal. The A/D converter chip consists of a correlated double sampler; a digitally controlled variable gain amplifier and a 16-bit A/D converter which can help improve the data quality. And the acquired digital signals are transmitted into the computer via USB 2.0 data port.
Our spectrometer with SHINERS technology can acquire the Raman spectrum signals efficiently in long time integration and weak signal environment, and the size of our system is well controlled for portable application.
Proc. SPIE. 8910, International Symposium on Photoelectronic Detection and Imaging 2013: Imaging Spectrometer Technologies and Applications
KEYWORDS: Detection and tracking algorithms, Spectroscopy, High power lasers, Light scattering, Laser applications, Control systems, Semiconductor lasers, Raman spectroscopy, Laser stabilization, Temperature metrology
The intensity of Raman light is very weak, which is only from 10-12 to 10-6 of the incident light. In order to obtain the required sensitivity, the traditional Raman spectrometer tends to be heavy weight and large volume, so it is often used as indoor test device. Based on the Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy (SHINERS) method, Raman optical spectrum signal can be enhanced significantly and the portable Raman spectrometer combined with SHINERS method will be widely used in various fields. The laser source must be stable enough and able to output monochromatic narrow band laser with stable power in the portable Raman spectrometer based on the SHINERS method. When the laser is working, the change of temperature can induce wavelength drift, thus the power stability of excitation light will be affected, so we need to strictly control the working temperature of the laser, In order to ensure the stability of laser power and output current, this paper adopts the WLD3343 laser constant current driver chip of Wavelength Electronics company and MCU P89LPC935 to drive LML - 785.0 BF - XX laser diode(LD). Using this scheme, the Raman spectrometer can be small in size and the drive current can be constant. At the same time, we can achieve functions such as slow start, over-current protection, over-voltage protection, etc. Continuous adjustable output can be realized under control, and the requirement of high power output can be satisfied. Max1968 chip is adopted to realize the accurate control of the laser’s temperature. In this way, it can meet the demand of miniaturization. In term of temperature control, integral truncation effect of traditional PID algorithm is big, which is easy to cause static difference. Each output of incremental PID algorithm has nothing to do with the current position, and we can control the output coefficients to avoid full dose output and immoderate adjustment, then the speed of balance will be improved observably. Variable integral incremental digital PID algorithm is used in the TEC temperature control system. The experimental results show that comparing with other schemes, the output power of laser in our scheme is more stable and reliable, moreover the peak value is bigger, and the temperature can be precisely controlled in ±0.1°C, then the volume of the device is smaller. Using this laser equipment, the ideal Raman spectra of materials can be obtained combined with SHINERS technology and spectrometer equipment.
A novel beam-shaping method which obtains nearly uniform illumination for a high-power Laser Diode (LD) stack is
introduced. Based on the properties of the angular distribution during the Gaussian beams propagate, a flat-topped beam
profile can be achieved by the superposition of Multi-tilted Gaussian beams. Due to the theory above, the individual
lensing techniques are introduced to shape the beams of the LD stack. Cylindrical lenses are used to control the
divergence-angle of the output beams. By adjusting the offset of each cylindrical micro-lens, each output beam on the
fast axis gains the different tilted emitting-angle. Meanwhile the beams on the slow axis are also shaped by a large
cylindrical lens. Thus the beam-shaping optical system is designed to reconfigure the beams of a high power LD stack to
form a Multi-tilted Gaussian beam shape for a 10°×10° field-angle illumination. The simulation results from ASAP
software show that uniform illumination can be obtained in the far-field district. With the proper uniformity and high
efficiency, the beam-shaping optical system we have proposed for high-power LD stacks can be well suitable for laser
illuminator in laser active imaging and detecting system.
The area array three-dimensional (3D) active imaging laser radar is a kind of remote sensing system which benefits high
detection speed. This type of laser radars employ area optical modulation devices such as micro-channels plate (MCP)
image intensifiers to modulate the photons flying time into intensity which can be detected by a charge coupled device
(CCD). The distance measurement precision of this kind of laser radars is determined by the short noise of the photons
numbers. This property limits the performance of this kind of laser radar. In this paper, a method based on second-order
coherence is presented to compensate the short noise. The analysis result shows the photon bunching effect improves the
SNR of the distance measurement with the same photon numbers. The second-order coherence based method is
proposed to prove the 3D active imaging laser radar SNR. An experiment system is introduced which has results verified
Scannerless imaging laser radar has been a focus of research in these years for its fast imaging speed and high resolution.
We introduced a three-dimensional imaging laser radar using intensified CCD as the receiver with constant gain and line
modulated gain. The distance map of a scene is obtained from two intensity images. According to the transmission
characteristics of the imaging system, a model of degeneration of the gray images is established and the range accuracy
of imaging laser radar based on this model is analyzed. The results show that the range accuracy is related with the
reflectivity, the actual distance and some other factors on the fast-distance-varying region, while it is mainly concerned
with shot noise for the flat area. On the basis of the cause of measurement error and the distribution characteristics of
noise, a method which uses iterative restoration algorithms on obtained intensity images is presented, Simulation is
carried out and the results show that root mean square error of distance map obtained with this method is decreased by
50%, compared with the distance map obtained by measurement. Finally the restoration results of radar images are
demonstrated to verify the effectiveness of this method.
Efficient beam shaping with uniform illumination is required in laser active imaging and detecting systems. In this paper, a beam-shaping method by superposition of tilted fundamental-mode Gaussian beams to produce nearly uniform illumination is proposed. The analytical formula for the average intensity of propagating multitilted Gaussian beams (MTGBs) is derived and used to study the uniformity of the beam profile with Fourier analysis. It is found that the MTGB maintains its flat-topped shape as it propagates and its uniformity is controlled by the parameters of fundamental-mode beams and superposition. Numerical examples are given. The method is used to reconfigure the beams of a high-power laser diode stack to form a MTGB shape for illumination of a 9×11.6-deg angular field. The simulation results from ASAP software show a shaping efficiency of 75%, and the rms deviation of the irradiance distribution from a flat-top shape is approximately 8%.
Three-Dimensional(3D) Active imaging are usually employed for target detection and recognition[1~3].
In recent years, many methods have been presented for high-speed 3D active imaging[4~5]. However,
for those methods employ one group of images only maintains one more gated partition, the depth
resolution increases linearly with the number of images. This character limits the performance of 3D
active imaging systems. In this paper, we demostrate how to overcome this limitation. In our method,
we introduce an exponential code method to ploting out partitions which makes the depth resolution
increased exponential with the number of images. Furthemore, oure poltiong is robust and realible for it
is based on binary principle.
A novel three-dimensional (3D) camera concept system could capture 3D image with thousands of pixels at range of
several kilometer in real time was presented. The camera used a pulse laser to illuminate the scene, a solid-stat chargecouple
device(CCD) sensor, and sample cumulation technology based on a gated binary image intensifier. The
cumulation charges captured in CCD carried the information of range. The system was designed to have some significant
advantages, such as low cost, simply schemes, high speed mainly limited to the speed of CCD frame capture. Potential
applications include navigation of autonomous helicopter, large target identification, sensing and guidance, auto collision
avoidance, robotic vision, atmospheric sensing and topography. In the paper, we discussed the fundamental principle and
schemes of the 3D camera system based on sample cumulation and presented the feasible experiment result with a photo
multiplier tube with binary character to simulate one pixel of the 3D camera system. Then we discussed the factors
which influence the quality of 3D image according to the experiment result.
It is convenient to apply three-dimensional (3D) detecting instruments to automatic drive, virtual reality modeling,
terrain reconnaissance, etc. It is presented that a new high-speed camera which achieves one three-dimensions image by
only one light pulse in this paper. It has a measurement range of one kilometer and a distance resolution of five meters.
This camera is composed with a pulse laser and three receivers which are made up with a Micro Channel Plate (MCP)
and a Charge Coupled Device (CCD) each. These parts are mature commercial productions that provide low cost and
high reliable to the 3D camera. As soon as the pulse laser emits a light pulse, the three receivers are modulated with
synchronistical control circuits. A 3D picture can be calculated by three different density images which are obtained by
that. The one-light-pulse-one-picture mode gives a flexible way to work with a gate signal. A 3D camera working with
high-speed gate signal can achieve high-speed photography easily. A mathematic model is established to describe
measurement range, distance detection precision and space resolving of the camera. The best modulation functions of the
receivers are given with consideration of white noise by Euler-Lagrange equation. Due to the best modulation function
we give a scheme is follows: The first receiver is modulated by a const gain, the second one is modulated by a linearly
increasing gain and the last one is modulated by a linear decreasing gain. This combination achieve both low noise and
simple structure. Because of the simple structure, several fibers which we named amending fibers can be used to amend
error of receiver modulation and synchronistical error. Analysis of the detection precisions of the camera and continuous
wave detection systems are carried out both in time domain and frequency domain. The results indicate pulse laser can
increase the detection range by suppressing background light greatly and decreasing imaging time. But it achieves lower
precision if the background light is faintness. Simulation experiment results are presented in this paper. A 1.4 kilometers
fiber was used in this experiment to simulate a 700 meters distant, a Laser Diode (LD) is employed to simulate the pulse
laser. A high voltage modulation circuit was designed to modulate the gain of MCP to implement the modulation
function. The experiment results with and without amending fibers indicated that the primary noises come from CCD and
the high voltage modulation circuit. The amending fibers can weaken the circuit errors in some degree. Future
improvement is described in the end of the paper also.
As the digital camera user base grows, so does the demand for digital imaging services. A new digital photo finishing system based on Liquid Crystal On Silicon (LCOS) is presented. The LCOS panel motherboard is made up of CMOS chip. Three individual streams of light (red, green, blue) are directed to corresponding Polarization Beam Spliter (PBS) to make the S polarization beam arrive at LCOS panel. When the Liquid appears light, the S polarization beam is changed to P polarization beam and reflected to pass through Polarization Beam Spliter. Compared with Thin Film Transistor-Liquid Crystal Display (TFT-LCD), LCOS has many merits including high resolution, high contrast, wide viewing angle, low cost and so on. In this work, we focus on the way in which the images will be displayed on LCOS. A liquid crystal on silicon microdisplay driver circuit for digital photo finishing system has been designed and fabricated using BRILLIAN microdisplay driver lite(MDD-LITE) ASIC and LCOS SXGA (1280×1024 pixel) with a 0.78"(20mm) diagonal active matrix reflective mode LCD. The driver includes a control circuit, which presents serial data, serial clock , write protect signals and control signals for LED, and a mixed circuit which implements RGB signal to input the LCOS. According to a minimum error sum of squares algorithm, we find a minimum offset and then shift RGB optical intensity vs voltage curves right and left to make these three curves almost coincide with each other. The design had great application in the digital photo finishing.
We are developing a new active three Dimension (3D) laser range imaging system based on a pulse light-source and a modulated receiver (PLMR). A double-frequency YAG laser emits light pulses, which are expanded to light cones, with a frequency of 60Hz. A light pulse can illumine a full scene and a modulated image intensifier micro-channel plate (MCP) selects the reflected light with proper optical imaging devices. A Charge Coupled Device (CCD) receives the MCP output signal and generates an intensity image, and two modulated avalanche photo diodes (APD) collects the light splitting from the light pulse as correct intensified values for the intensity image. The system generates a 3D image, which needs a minimum of two different intensity images. These intensity images are obtained with or without illumination of light pulse and with different modulation applied to the MCP. The above imaging times are equal and relate to detection range. We present the best combination of the modulations and illumination conditions, in the meaning of minimum variance, and the relative theoretical analyses. Detection range, measurement resolution and scan frame rate of the system are given considering the influence of background light and circuit noise. Comparing to other 3D imaging systems, our system has the advantage of achieving both long measurement range and high spatial resolution. Potential applications to industry and military of the 3D laser imaging system are also presented.
The thickness of metallic foil is measured by differential low-coherence interferometry. Two tandem Michelson Interferometers (MI), of which reflective surfaces measured are the corresponding surfaces of metallic foil, are used as basic interferometric system to obtain interference fringes on a spectrometer. Therefore, the interference fringes only depend on the path differences due to the thickness of metallic foil. The interference fringes are analyzed with a modified extremum method based on the least root mean square (RMS) deviation. The experimental results on thickness measurement are presented.