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EP0054637A2
Expired / Lapsed
EP
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Image density test circuit for an electrophotographic copier
Assignee: International Business Machines Corp
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Filing: 1981-10-09
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Granted: —
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Expires: 2001-10-09
Abstract
Abstract An image density test circuit for an electrophotographic copier includes a light source (33) and a sensor (34) for monitoring a test patch (30) produced on the imaging element (26) of the copier. Whilst the bare photoconductor is being sensed an energising circuit sets the light source output to a first level and a storage circuit holds the value of the sensor output. When the light beam contacts the leading edge of the patch, the storage circuit is isolated from the sensor and drive circuits (102,103) switch the energising circuit to drive the light source to a level at which, for a predetermined patch density, the sensor output remains unchanged. The output of the sensor is then compared with the value in the storage circuit by a comparator (121) to provide a first output if the test patch is below the predetermined density or a second output if not.
Inventors
- 👤 Robert Wayne Pries
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-28 16:02
CPC Classifications
G; G03; G03G; G03G15/00; G03G15/06; G03G15/08; G03G15/0822; G03G15/0848; G03G15/0849; G03G15/0855; G03G15/50; G03G15/5033; G03G15/5041
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
214 words
An image density test circuit for an electrophotographic copier of the type in which, in a test cycle, a toned test area adjacent an untoned area are produced on a substrate, said circuit including a light source (33) arranged to direct a beam of light on to the substrate and a light sensor (34) positioned to sense light reflected by said areas from the beam, characterised by switching means (111) switchable into a first and a second condition to provide a substantially equal output from the sensor in response respectively to the reflected light from the untoned area and from the toned area, when of a predetermined density, means (117) for storing a first signal indicative of the sensor output when sensing the untoned area with the switching means in the first condition, means (114, 119) responsive to the sensor sensing a change from the untoned to the toned area for switching the switching means to the second condition, and comparator means (121) for comparing a second signal indicative of the sensor output when sensing the toned area with the switching means in said second condition with the stored first signal to provide a first or a second output signal in accordance with whether or not the toned area is below said predetermined density.
Claim 2
Dependent Claim
214 words
An image density test circuit for an electrophotographic copier of the type in which, in a test cycle, a toned test area adjacent an untoned area are produced on a substrate, said circuit including a light source (33) arranged to direct a beam of light on to the substrate and a light sensor (34) positioned to sense light reflected by said areas from the beam, characterised by switching means (111) switchable into a first and a second condition to provide a substantially equal output from the sensor in response respectively to the reflected light from the untoned area and from the toned area, when of a predetermined density, means (117) for storing a first signal indicative of the sensor output when sensing the untoned area with the switching means in the first condition, means (114, 119) responsive to the sensor sensing a change from the untoned to the toned area for switching the switching means to the second condition, and comparator means (121) for comparing a second signal indicative of the sensor output when sensing the toned area with the switching means in said second condition with the stored first signal to provide a first or a second output signal in accordance with whether or not the toned area is below said predetermined density.
Claim 3
Dependent Claim
49 words
A test circuit as claimed in claim 1, further characterised by means (110) for energising said light source coupled to said switching means to energise the light source to first and second levels in response to the switching of the switching means into said first and second conditions respectively.
Claim 4
Dependent Claim
25 words
A test circuit as claimed in claim 1 or claim 2, further characterised in that said substrate comprises the photoconductive imaging element of the copier.
Claim 5
Dependent Claim
52 words
A test circuit as claimed in any of the previous claims, further characterised by a switch device coupled to said means for storing, said switch device being coupled to the means responsive to the sensor sensing said change to isolate the means from storing from the sensor in response to such sensing.
References Cited (Backward Citations)
No citation records indexed.
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