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Blur Correction Circuit for Scanners

IP.com Disclosure Number: IPCOM000083355D
Original Publication Date: 1975-May-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 3 page(s) / 35K

Publishing Venue

IBM

Related People

Pricer, WD: AUTHOR

Abstract

Image distortion in scanners, for example, area scanners, is eliminated or at least minimized without using light-strobing techniques. In scanners light incident on a photosensitive portion, i.e., a picture or photoelement, is detected by collecting charge generated over a period of time, called the integration time, onto a circuit node. At the end of the integration time, this charge is sequentially gated or shifted out, during a readout time, through circuits associated with other photoelements to an amplifier.

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Blur Correction Circuit for Scanners

Image distortion in scanners, for example, area scanners, is eliminated or at least minimized without using light-strobing techniques. In scanners light incident on a photosensitive portion, i.e., a picture or photoelement, is detected by collecting charge generated over a period of time, called the integration time, onto a circuit node. At the end of the integration time, this charge is sequentially gated or shifted out, during a readout time, through circuits associated with other photoelements to an amplifier.

To prevent the collected signal from a particular circuit node from being modified by light incident on the other circuit nodes, the other circuit nodes are shielded from the incident light or a high-intensity strobing light is used to store the information on the circuit nodes during a short duration integration time and turned off during the readout time. An alternative solution is to employ very long integration periods followed by very rapid shifting out of the data, so as to minimize the amount of blurring.

By utilizing this circuit which corrects for blurring, integration periods and readout periods may be of comparable duration without the need for strobing the scanner with high-intensity light or shielding the circuit nodes.

With the integration time and the readout time equal, as an example, the light intensity at the photoelements is adjusted so that the maximum light intensity will generate charge up to one half of the dynamic range of the circuitry. If the scanner information is shifted from left to right, each sensed photoelement will be blurred by an amount proportional to the incident light on each photoelement to its right.

To correct for blurring in a signal from a particular photoelement, the true signal from all the photoelements to the right of the particular element is detected, and a fraction of the total of these signals is subtracted from the incoming signal associated with the particular photoelement.

The amplifier into which the signals from the photoelements are shifted is a difference amplifier having a first input terminal 10, to which these signals in the form of a voltage Vin are applied. The voltage Vin may be derived from a first photoelement of a light-sensitive charge transfer device, e.g., a charge-coupled device or a bucket-brigade shift register, where the charge is converted to a voltage at a capacitor, as is well known.

During the integration time, the reset switch of the blur correction circuit is closed to discharge the accumulator capacitor, and to apply a zero...