Browse Prior Art Database

Image Registration Detection System

IP.com Disclosure Number: IPCOM000097414D
Original Publication Date: 1962-Nov-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 3 page(s) / 64K

Publishing Venue

IBM

Related People

Flemming, DC: AUTHOR

Abstract

In character recognition machines using the multiple image masking system, recognition timing is controlled by determining when optimum registration of images and masks occurs.

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Image Registration Detection System

In character recognition machines using the multiple image masking system, recognition timing is controlled by determining when optimum registration of images and masks occurs.

In A, document 10 is moved to position printed character 4 under light source 11 and rotating mirror 12. Mirror 12 has multiple reflecting surfaces 13, each tilted at a slightly increasing angle with respect to the mirror axis. During rotation, each surface reflects a character image into all lenses 14 and onto respective transparent image masks 15. Mirror rotation causes the images to move vertically across masks 15 repetitively and simultaneously advance in horizontal increments along the masks. The horizontal and vertical advance of each image across its mask compensates for character misregistration relative to its mask so that reliable recognition occurs at optimum registration.

Behind each mask 15,is a photocell 17 providing an output voltage proportional to the mask area covered by an image. The outputs of 17 are compared. The cell producing the largest voltage change is interpreted as covered with the most image and representative of coincidence between mask and image. This system must be confined in operation to the times when all the images are optimally registered with their respective masks.

The circuits are controlled in their operation by use of transparent registration mask 18 and photocell 20 which also receive an image. The position of mask 18 is offset at least two horizontal advance increments in the leading direction to detect optimum registration of its image and then activate the circuits.

In B, the 4 images repetitively traverse 18 and 15. With each sweep to the right in B, photocell 20 produces a horizontal registration envelope of flat-topped output pulses (C). Each increases in amplitude until the image on each sweep falls entirely within the transparent area when the signals become uniform in amplitude. With further horizontal progression, increasing amounts of the image fall off the mask on the right so that the succeeding output pulses decrease in amplitude. Since mask 18 is offset to the left in the leading direction, it receives decreasing quantities of image just as the images on masks 15 reach optimum registration. The decrease of signal amplitude from the maximum is used to activate recognition circuits.

To accurately detect optimum registration, two successive sample pulses are compared to determine which is closest to optimum registration. Only pulses that become less negative are considered in the comparison. To reduce premature indications that the registration envelope has started to decrease, a valid upturn of the envelope is required to depart from the horizontal negative flat-top at a minimum angle, for instance, at 45 degrees (Ca).

The detection of a valid optimum registration is obtained by the circuit of D. Image signals at photocell 20 are amplified and clipped at circuit 21 t...