Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

SCANNING ELECTROMETER AUTO ZERO SYSTEM

IP.com Disclosure Number: IPCOM000023926D
Original Publication Date: 1979-Apr-30
Included in the Prior Art Database: 2004-Apr-01
Document File: 4 page(s) / 718K

Publishing Venue

Xerox Disclosure Journal

Abstract

A block diagram of the scanning electrometer system of the present invention is shown in Figure 1. A photoreceptor or X-rayimage receptor 1, consisting of conducting substrate 2, voltage source 1 ' being connected thereto and a semi-conductor coating 3 having a latent image or charge distribution pattern representing desired information thereon. A probe 5 senses the charge pattern on the surface of photoreceptor 3 across the gap 4, Probe 5 drives the input of detector 14 such that the output voltage on lead 13 is fed to an inverting amplifier 6. The amplifier output at terminal 7 corresponds to the latent image.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 4

XEROX DISCLOSURE JOURNAL

SCANNING ELECTROMETER AUTO ZERO SYSTEM
Lee M~Klynn

2-\

Proposed Classification U~S~CL 324/4
Int
0 CL GOlv 3/16

3

p

+

"OPERATE"

t

Volume 4 Number 2 March/April 1979 229

[This page contains 1 picture or other non-text object]

Page 2 of 4

SCANNING ELECTROMETER AUTO ZERO SYSTEM (Cont'd)

A block diagram of the scanning electrometer system of the present invention is shown in Figure 1. A photoreceptor or X~rayimage receptor 1, consisting of conducting substrate 2, voltage source 1 ' being connected thereto and a semi~ conductor coating 3 having a latent image or charge distribution pattern representing desired information thereon. A probe 5 senses the charge pattern on the surface of photoreceptor 3 across the gap 4, Probe 5 drives the input of detector 14 such that the output voltage on lead 13 is fed to an inverting amplifier
6. The amplifier output at terminal 7 corresponds to the latent image.

The detector 14, such as a metal oxide semiconductor P~channelenhancement field effect transistor, tends to accumulate charge on its input due to surface leakage, its extremely high input impedance and small input capacitance. This charge produces an offset which increases with time during measurements.

The charge offset is reduced to a small value by grounding the input with a switch or relay 12. When the relay 12 is opened, any residual charge will be parametrically amplified to a significant but unpredictable value due to the change in the input capacitance.

To eliminate the residual offset at the output, the output at terminal 7 is amplified by a high~gain,non~4nvertingamplifier 8 which passes thru switch or relay 9 to charge a capacitor 10. The charge or voltage on capacitor 10, which is proportional to the residual offset, is amplified by a non~4nvertingamplifier 11 to produce a current at the input to amplifier 6 proportional to the residual offset. This current is fed into the inverting input of amplifier 6 to cause the output at terminal 7 to go to zero when switch 9 is closed. When switch 9 is open, the zeroing current remains proportional to the charge stored on the capacitor 10. Leakage from capacitor 10 is minimized by selecting a stable, high quality, low~4eakagecapacitor dielectric such as a polystyrene or polycarbonate. Amplifier 11 has an FET input to give it a very high input impedance or low current drain...