Browse Prior Art Database

Electronic Control of Responsivity and Color Response in CCD Imaging Devices

IP.com Disclosure Number: IPCOM000087829D
Original Publication Date: 1977-Mar-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 72K

Publishing Venue

IBM

Related People

Chamberlain, SG: AUTHOR

Abstract

In page readers and document reading machines used for document scanning, the luminance (brightness) of the document usually varies by few orders of magnitude. Thus the machine is required to detect characters of wide luminance variations with reasonable signal-to-noise ratio. At low luminance the machine should give an output with good signal-to-noise ratio and should be free from blooming (charge spilling) at high luminance levels. For color copying machines, it is also required that the scanning devices have the appropriate response for blue, green and red colors.

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Electronic Control of Responsivity and Color Response in CCD Imaging Devices

In page readers and document reading machines used for document scanning, the luminance (brightness) of the document usually varies by few orders of magnitude. Thus the machine is required to detect characters of wide luminance variations with reasonable signal-to-noise ratio. At low luminance the machine should give an output with good signal-to-noise ratio and should be free from blooming (charge spilling) at high luminance levels. For color copying machines, it is also required that the scanning devices have the appropriate response for blue, green and red colors.

This article describes a device structure and a method to electronically control the photosensitivity of charge coupled image scanning devices. In addition, the quantum response of the device for each color can be electronically controlled.

Figs. 1A and 1B show the proposed device structure. A buried n/+/ layer is introduced to the conventional CCD (charge-coupled device) imaging device. This layer is reverse-biased with respect to the substrate. The signal, which is a photogenerated charge, consists of essentially two components: (1) carriers generated within the space charge layer (SCLI) and (2) carriers generated in the neutral region (d) and within the space charge layer (SCLI).

Control of the photosensitivity is achieved by varying the bias, V(b). The responsivity of the device (charge collected per watt cm/-2/ of incident light) will be a strong function of the bias V(B) since the latter modulates the width (d) of the neutral...