Patent
1989-02-27
1990-10-02
Mintel, William
357 32, 357 68, 357 51, H01L 2714
Patent
active
049610961
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a semiconductor image position sensitive device for use in optical measurement of distance, position, movement, distortion, etc. and particularly to construction of a semiconductor image position sensitive device which is adequate for high-precision measurement. This invention also relates to a method for improving precision of image position sensing by use of the position sensitive device.
BACKGROUND ART
As image position sensitive devices for use in optical measurement of position, distance, movement, deformation, etc., there have been widely used semiconductor position sensitive devices(PSD) in which a resistive layer is provided on a photo sensitive layer. In the PSD, photo current is generated under a photo image projected on the photo sensitive layer. The photo current is transmitted through the resistive layer to opposite output electrodes. And the photo current is outputted from the opposite output electrodes. The intensities of the output currents are detected and the center of the intensities of the currents is calculated to determine the position of the photo image. The prior arts are disclosed, for examples, in G. P. Petersson and L. E. Lindholm, "Position sensitive light detectors with high linearity", IEEE J. Solid-State Circuits, vol. SC-3, pp. 392-399, 1987, D. J. W. Noorlag and S. Middelhoek, "Two-dimensional position sensitive photodetector with high linearity made with standard IC-technology", IEEE J. Solid State and Electron Dev., vol. 3, pp. 75-82, 1979, and D. J. W. Noorlag "Quantitative Analysis of Effects Causing Nonlinear Position Response in Position-Sensitive Photodetectors", IEEE Trans. Electron Devices, vol. ED-29, No. 1, pp. 158-161, 1982.
FIG. 5 shows a cross-sectional view of a typical prior art semiconductor position sensitive device. When light L is projected on a photo sensitive layer P, photo current is generated in the photo sensitive layer P. After passing through a resistive layer R, output currents I.sub.A and I.sub.B are outputted from the output electrodes T.sub.A and T.sub.B. Values of the output currents I.sub.A and I.sub.B are obtained by dividing the amount of the photo current in the resistance ratio of the resistive layer between the light incident position and the output electrodes T.sub.A and T.sub.B, respectively. Thus, value obtained by dividing the difference between the output currents (I.sub.A -I.sub.B) with the sum of the output currents (I.sub.A +I.sub.B) is proportional to the light incident position X.sub.D from the center. Accordingly, we can obtain information about the light incident position by introducing the output currents I.sub.A and I.sub.B into a signal processing circuit as shown in FIG. 6. In the circuit, the output currents are amplified by buffer amplifiers B.sub. 1 and B.sub.2. Next, the above operation is carried out by operational amplifiers A.sub.1 and A.sub.2 and a divider .div., and further, analog to digital conversion is carried out by an analog to digital converter A/D.
The precision of the prior art image position sensing method mainly depends on the precision of the analog signal processing means and the precision (resolution) of the analog to digital conversion. Improvement of the precision of the analog processing means has been almost impossible and even if it is realized it would be very expensive. This creates a big problem for improving the precision (resolution) of image position sensing by use of the semiconductor image sensing device.
DISCLOSURE OF THE INVENTION
In order to solve the above problem, that is, in order to realize high-precise image position sensing without improving precision (resolution) of the analog processing means and that of the analog to digital converter, in this invention, the sensing region of the semiconductor image position sensitive device is divided into a plurality of sections so that an arbitrary section or arbitrary successive sections can be operated as a sole semiconductor image position sensitive device as a result of selection of ou
REFERENCES:
Peterson et al., "Position-Sensitive Light Detectors with High Linearity," IEEE Jour. of Solid-State Circuits, vol. SC-3, No. 3, Jun. 1978, pp. 393-399.
Noorlag et al., "Two-Dimensional Position-Sensitive Photodetector with High Linearity Made with Standard I.C.-Technology," Solid-State and Electron Devices, May 1979, vol. 3, No. 3, May 1979, pp. 75-82.
Noorlag et al., "Quantitative Analysis of Effects Causing Nonlinear Position-Sensitive Photodetectors", IEEE Transactions on Electronics Devices, vol. ED-29, No. 1, Jan. 1982.
Wang et al., "The Linearity and Sensitivity of Lateral Effect Position Sensitive Devices--An Improved Geometry," IEEE Transactions on Electron Devices, vol. 36, No. 11, Nov. 1989, pp. 2475-2480.
Mintel William
Rikagaku Kenkyusho
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