Lateral Effect Position Sensitive Detector Research Articles

Position-Sensitive Detector (PSD) Guided Servoing Method for Industrial Robot Calibration

This article presents our recently developed position-sensitive detector (PSD) guided servoing system for precise localization of industrial robots. The system is portable and affordable, and can position robot precisely so as to benefit further research on the calibration applications of industrial robots. To achieve highly precise position feedback, we have employed a high performance lateral-effect PSD with a resolution of 0.5 µ m. Based on the system kinematics and dynamics, a PSD guided servo (PSDGS) control method is then developed and simplified to be a planar motion control approach in which an on-line estimation of the transformation matrix between the PSD object and the robot base is applied. The experiments have been implemented on an ABB industrial robot IRB1600. The achieved results demonstrate that the mean localization precision of the industrial robot using the developed PSDGS method is totally better than 20 µ m.

Nanometer gold–silica composite particles manipulated by optical tweezers

We have studied the behavior of nano or micro size composite particles submitted to optical trapping forces and a comparison was made with homogeneous particles of similar dimension. The forces were measured using the power spectrum signal analysis. Most of the results presented were obtained using a lateral effect position sensitive detector (PSD), which allowed the fluctuations of the particle position in the optical trap to be monitored. A 4-quadrant photodiode was also used for the same purpose. We bring clear experimental evidence that the trapping force was increased by a factor of about 2–3 for composite particles made of a colloidal gold core encapsulated in a silica shell, with respect to homogeneous silica or latex beads. These results were discussed in the frame of the various approaches currently used for modeling optical tweezing forces.

Principle of FT spectrometer based on a lateral effect position sensitive detector and multi channel Fabry–Perot interferometer

The principle of a new type of multi channel Fourier-Transform spectrometer based on a multi channel wedge Fabry–Perot interferometer using a one dimensional lateral effect Position Sensitive Detector and a scanning slit for interferogram readout have been shown. The design of this spectrometer is very compact and the readout electronics very simple. The drawback of using a scanning slit system is minimized by the use of a position sensitive detector where the position is inherently known for each measurement. Experiments show that the position can be resolved with high accuracy and the summation of the two photocurrents gives the interferogram distribution after scanning the slit between the wedge interferometer and the position sensitive detector. The spectral resolution obtained with a 25 mm wedge interferometer together with a 45 mm position sensitive detector and a 25 μm slit is about 5 nm around 600 nm wavelength range, which is close to the theoretically anticipated resolution. The evaluated spectrometer setup show promising results and could be used in applications where compact and low cost spectrometers are required.

Improved Accuracy of 2-D Non-Contact Range Sensors Using 2-D Lateral Effect Position Sensitive Detector

This paper presents a new set of estimation formulae for non-contact 2D displacement measurement by using the principle of triangulation and the position sensitive detector (PSD) as a 2-D range sensor. It has been shown in theory that the new set of formulae outperforms the conventional formulae by providing much more accurate estimate of the 2D displacement. The theoretical analysis has been verified by simulation studies.

Evaluation of an integrated Fourier-transform spectrometer utilizing a lateral effect position sensitive detector with a multi-channel Fabry–Perot interferometer

The basis of this paper is the evaluation of an integrated multi-channel Fourier-transform (FT) spectrometer based on a multi-channel wedge Fabry–Perot interferometer and a one-dimensional lateral effect position sensitive detector (PSD). The use of a PSD for an interferogram readout allows for a simple scanning mechanism with no requirement for any position reference. The use of a wedge-shaped interferometer makes it possible to integrate it directly onto the PSD surface, thus producing a very compact spectrometer. The capabilities of the spectrometer are demonstrated by absorption spectral measurements using a reference sample. In addition, spectral measurements on 532 nm DPSS and 632.8 nm He–Ne lasers are presented. The resolution of the spectrometer is approximately 5 nm. The evaluated spectrometer set-up can be used in applications where compact and low cost spectrometers are required, such as in process control and in education. Further, it is shown that there are deteriorations in very high accuracy position measurements, which are caused by changes in incident light intensity. A model describing the above-mentioned nonlinearities was developed based on analysing the equivalent circuit for PSDs and parameters such as leakage current and serial resistance. Additionally, a method is proposed to assist in the reduction of the nonlinearity caused by this effect.

Processing and Characterization of a MOS-Type Tetra Lateral Position Sensitive Detector With Indium Tin Oxide Gate Contact

A 2-D tetra lateral position sensitive detector (PSD) based on the metal-oxide-semiconductor (MOS) principle has been manufactured and characterized. The active area of the device is 5 mm times 5 mm and the intention is to use the central 4 mm times 4 mm for low nonlinearity measurements. The gate contact is made of indium tin oxide (ITO) that is a degenerate electrically conducting semiconductor, which, in addition, is also transparent in the visible part of the spectrum. The use of a MOS structure results in a processing with no necessity to use implantation or diffusion in order to make the resistive p-layer as in a conventional p-n junction lateral effect PSD. Position measurements show good linearity in the middle 4 mm times 4 mm area. Within the middle 2.1 mm times 2.1 mm, the nonlinearity is within plusmn1.7% of the active area with a position detection error of maximum 60 mum. Measured MOS IV characteristics are compared to a level 3 spice model fit and show good agreement. The threshold voltage is determined to be -0.03 V. Responsivity measurements show a high sensitivity in the visible spectral region.

The effect of mechanical stress on lateral-effect position-sensitive detector characteristics

Abstract Position-sensitive detectors (PSDs) are widely used in noncontact measurement systems. In order to minimize the size of such systems, interest has increased in mounting the PSD chip directly onto printed circuit boards (PCBs). Stress may be induced in the PSD because of the large differences in thermal expansion coefficients, as well as the long-term geometrical stability of the chip packaging. Mechanical stress has previously been shown to have an effect on the performance of semiconductors. The accuracy, or linearity, of a lateral effect PSD is largely dependent on the homogeneity of the resistive layer. Variations of the resistivity over the active area of the PSD will result in an uneven distribution of photo-generated current, and hence an error in the readout position. In this work experiments were performed to investigate the influence of anisotropic mechanical stress in terms of nonlinearity. PSD chips of 60×3 mm active area were subjected, respectively, to different amounts of compressive and tensile stress to determine the influence on the linearity.

Simulation of a low atmospheric-noise modified four-quadrant position sensitive detector

A modified four-quadrant position sensitive detector (PSD) is developed. This structure is less sensitive to atmospheric turbulence that is a major drawback with the traditional four-quadrant detector. The inter-electrode resistance is as high as for the four-quadrant detector, which is an advantage compared to the lateral effect PSD. The linearity for the modified four-quadrant detector is good in the whole active range of sensing. The structures are limited to small sensing areas with well focused beams and are suitable for use in detectors up to 1 mm in size.

A binary photodetector array for position sensing

The implementation and test results of a 16 × 16 CMOS photodetector array for position-sensing applications are presented. Unlike conventional position-sensitive detectors (PSDs), it can be used for simultaneous multiple spot detection with high accuracy. To decrease the signal-processing overhead characteristic of area arrays, binary detection and random access readout are used. The fill factor and pitch of the array are 30% and 50 μm, respectively. Spatial-quantization-limited position-sensing accuracy of 4.3 μm is achieved using a uniform spot of 280 μm in diameter, total signal power of about 8 nW and pulse width of 8 ms. At lower signal levels, the accuracy is decreased by the spatial noise caused by the mismatch of threshold-setting current mirrors operating in weak inversion. The array outperforms a typical largearea (~ 100 mm 2) lateral effect PSD (LEP) when a measurement bandwidth less than 10 kHz is used.

Position detection of multiple light beams using phase detection

Earlier work on lateral-effect position-sensitive detectors (PSD) has used an amplitude detection signal-processing scheme to determine the position of the centroid of the incident light beam on the PSD surface. In this work we introduce a phase detection method of position measurement which is based on detecting the phase difference between the sinusoidal currents flowing through the metal electrodes. A distributed transmission line model for the PSD and a one-pole model for the transimpedance preamplifier are used in the analysis of the sensor. Experimental results are presented and are found to be in close agreement with simulation results. It is seen that the spatial resolution is proportional to the modulation frequency. With a light modulation frequency of 50 kHz and the introduction of frequency multiplication (/spl times/8) after the transimpedance preamplifier, a spatial resolution of 2 /spl mu/m is demonstrated. For application in multi-degree-of-freedom position sensors, we demonstrate the simultaneous detection of centroids of multiple light beams using frequency division multiplexing. Application of the phase method of position detection to a two dimensional PSD shows a maximum deviation from linearity of 1% over the working range of the PSD. >

Position dependence of the transient response of a position-sensitive detector under periodic pulsed light modulation

A model based on sinusoidal steady-state analysis is developed for the position-sensitive detector (PSD), which is approximated as a distributed RC transmission line. This model is used to study the output response of the lateral effect PSD (i) when only one pulse-modulated light beam is incident and (ii) when two light beams of different wavelengths, with one beam modulated at a frequency f and the other beam modulated at a frequency 2f, are incident at the same time. The simulation shows, and experiments confirm, that the transient response of the PSD consists of a position-dependent dead time (time for the output current to sense the change in the induced photocurrent) and a position-independent exponential rise decay time. For the application of resolving the positions of two or more pulsed-modulated light spots, it is shown that there is a position-dependent upper limit on the usable modulation frequency. With the per-unit-length values chosen for the sheet resistance as R=315 Omega /mm and the junction capacitance as C=330 pF/mm, the modulation frequency limit is determined to be 20 kHz.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>