Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1990-08-14
1992-08-04
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
356432, 73602, G01N 2188, G01N 2125
Patent
active
051361728
ABSTRACT:
A method and apparatus are disclosed for detection of surface defects and internal defect information of a sample, such as a semiconductor device, using the photoacoustic effect. Operationally, an intensity-modulated laser beam is provided having a predetermined desired frequency. The intensity-modulated laser beam is focused on the sample thereby inducing said photoacoustic effect inside the sample which is detected in two-dimensional directions of the sample so as to compose a two-dimensional photoacoustic image of the excited sample. Surface and internal information of the sample is then extracted from the two-dimensional photoacoustic image and an inverse filtering factor is in turn computed on the basis of a thermal impulse response of the particular sample for compensating degradation of the resolution of the actual photoacoustic image obtained. Lastly, the computed inverse filtering factor is then applied to the detected photoacoustic image to arrive at an image having greatly improved resolution.
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Masanori Hangyo, et al., "Photoacoustic Microscope", Department of Applied Physics, Faculty of Engineering OSAKA University, (Hihakai Kensa, Nondestructive Testing), vol. 36, No. 10, Oct. 1987, pp. 730-736.
P. Cielo, et al., "Laser Generation of Convergent Acoustic Waves and Applications to Materials Evaluation", IEEE 1986 Ultrasonics Symposium, pp. 515-526.
Kembo Yukio
Kitamori Takehiko
Nakata Toshihiko
Sawada Tsuguo
Hitachi , Ltd.
Lee J.
Nelms David C.
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