# US 4,400,617 A · Correction circuit of a halftone dot area rate detector

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- Number: US 4,400,617 A
- Document ID: US4400617A
- Status: Granted
- Kind: A
- Application number: 06/320,096
- Filed: 1981-11-10
- Granted: 1983-08-23
- Earliest claimed: 1980-12-01
- Assignees: Dainippon Screen Seizo Kabushiki Kaisha
- Inventors: Yasuhiro Yonekura
- Web page: https://patentgrep.com/patent/US4400617A

## CPC

- G03C 5/02: Sensitometric processes, e.g. determining sensitivity, colour sensitivity, gradation, graininess, density; Making sensitometric wedges
- G01N 21/5907: {Densitometers}
- G03F 5/00: Screening processes; Screens therefor {(plates or light sensitive layers with incorporated screen G03F7/004)}
- H04N 1/407: Control or modification of tonal gradation or of extreme levels, e.g. background level
- G03C: PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES (for photomechanical purposes G03F); PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY (photographic processes characterised by the use or manipulation of apparatus classifiable per se in subclass G03B, see G03B; photomechanical production of textured or patterned surfaces G03F; electrophotography, magnetography G03G)
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G)
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

A correction circuit of a halftone dot area rate detector wherein a relation between a detected halftone dot area rate and a light transmittance or reflectance of an object obtained by a halftone photography is approximately expressed by a turning curve having at least one turning point, which comprises line segments, by using a turning point correction circuit comprising an inverting amplifying circuit, wherein another inverting amplifying circuit is coupled in parallel with the turning point correction circuit, and wherein a potensiometer couples the outputs of the two circuits and outputs a signal corresponding to a correction amount.

## Claims

### Claim 1

A correction circuit of a halftone dot area rate detector wherein a relation between a detected halftone dot area rate and a light transmittance or reflectance of an object obtained by a halftone photography is approximately expressed by a turning curve having at least one turning point, which comprises line segments, by using a turning point correction circuit comprising an inverting amplifying circuit, the improvement which comprises:
(a) another inverting amplifying circuit which is coupled in parallel with the turning point correction circuit; and
(b) a potentiometer which couples the outputs of the two circuits and which outputs a signal corresponding to a correction amount.

### Claim 2 (depends on 1)

A correction circuit as defined in claim 1, wherein another inverting amplifying circuit comprises an operational amplifier and resisters connected thereto.