Browse Prior Art Database

LCD Panel/Filter Image Recognition System

IP.com Disclosure Number: IPCOM000038910D
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 3 page(s) / 46K

Publishing Venue

IBM

Related People

Broockman, EC: AUTHOR [+3]

Abstract

LCDs (liquid crystal displays) are utilized to generate an unknown image for recognition and a master pattern for comparison. Polarized, collimated light rays traverse the unknown image and the master comparison image and are focussed through a lens onto a photodetector to measure the quanta of total light transmitted by the pair of LCD panels. The unknown image is first compared against a negative of the master image and any transmitted light is quantified. Then the negative of the unknown image is compared against the positive of the master image, and any transmitted light is also quantified. The algebraic addition of the two quantified values represents the Exclusive ORing of the images and represents a measure of the number of pixels of mismatch between the two LCD displays. The optical apparatus, shown in Fig.

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LCD Panel/Filter Image Recognition System

LCDs (liquid crystal displays) are utilized to generate an unknown image for recognition and a master pattern for comparison. Polarized, collimated light rays traverse the unknown image and the master comparison image and are focussed through a lens onto a photodetector to measure the quanta of total light transmitted by the pair of LCD panels. The unknown image is first compared against a negative of the master image and any transmitted light is quantified. Then the negative of the unknown image is compared against the positive of the master image, and any transmitted light is also quantified. The algebraic addition of the two quantified values represents the Exclusive ORing of the images and represents a measure of the number of pixels of mismatch between the two LCD displays. The optical apparatus, shown in Fig. 1, utilizes a pair of liquid crystal displays 3A and 3B which are exposed to a light source 1 which has been collimated through a collimator 2. The light source 1 and

(Image Omitted)

collimator 2 are arranged to produce a polarized light source so that the LCD panel will either transmit or block passage of most of the light depending upon their state of activation. A lens 4 focusses light transmitted by the panels 3A and 3B onto a photodetector, such as a photo diode 5. The total current conducted by the photo diode is proportional to the amount of light passing through the combined LCD panels. For pattern recognition, two patterns are used. The master image is called M and the unknown image to be studied for authenticity and matched against the master is called U. This disclosure performs matching by initially storing the image U on the LCD 3A closest to the light source 1. Next, the negative image of the master M is stored in the LCD array 3B closest to the lens 4. The light collected by the lens 4 and focussed onto the photodetector 5 is thus the logical AND of U and not M. The same procedure is then repeated with images inverted; i.e., not U and M are ANDed together. This may be achieved either by displaying the negative of the unknown and the positive of the master image or simply by rotating the collimated polarized light source through an angle sufficient to cause the rotated portions of the display in the panel which are blocking the polarized light beam to transmit, and vice versa. The algebraic sum of the ANDing of U and not M and not U and M is equivalent to the Exclusive ORing of the images U and M.

If the two images are identical, it will be observed that the total light transmitted will be...