# US 5,072,259 A · Image forming apparatus having magnification capabilities with charge removal outside image area

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- Number: US 5,072,259 A
- Document ID: US5072259A
- Status: Granted
- Kind: A
- Application number: 07/532,227
- Filed: 1990-06-05
- Granted: 1991-12-10
- Earliest claimed: 1982-11-20
- Assignees: Canon Kabushiki Kaisha
- Inventors: Yoshinori Ikeda
- Web page: https://patentgrep.com/patent/US5072259A

## CPC

- G03G 15/041: with variable magnification
- G03G 15/047: for discharging non-image areas
- G03G 2215/0439: Automatic detection of properties
- G03G 2215/0446: Magnification degree
- G03G 2215/0451: Light-emitting array or panel
- G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY

## Abstract

An image forming apparatus has as control unit which controls an image formation area on a photosensitive drum in accordance with original document size information detected by an original document size detector and magnification/reduction scale determined by a selected magnification/reduction mode. Unnecessary area other than a desired image formation area is discharged.

## Claims

### Claim 1

An image forming apparatus comprising:
a platen adapted for putting thereon an original document;
means for illuminating the original document put on said platen;
a photosensitive medium;
charging means for applying electric charge on said photosensitive medium;
means for setting a desired magnification;
means for forming a latent image corresponding to the illuminated original document on the charged photosensitive medium wherein said latent image is formed at the desired magnification set by said setting means;
means for removing charge from a portion of said photosensitive medium, said removing means comprising a plurality of light sources each individually operable;
developing means for providing a visible image for the latent image formed on said photosensitive medium;
means for transferring the visible image on said photosensitive medium to a recording sheet;
a plurality of sensing means each for sensing whether the original document is absent at associated ones of a plurality of predetermined positions on said platen;
means for detecting a size of the original document prior to the latent image forming operation by said forming means, said detecting means designating the original document to corresponding to one of a plurality of fixed sizes based on respective outputs of said plurality of sensing means;
means for determining light sources to be turned on and light sources to be turned off among said plurality of light sources, and for determining a period of time for the light sources to be turned off on the basis of the combination of the magnification set by said setting means and the size detected by said detecting means; and
means for controlling, during the latent image forming operation of said forming means, the operation of said plurality of light sources in accordance with a determination result of said determining means to that charge can be removed from an area on said photosensitive medium other than the area of the latent image corresponding to the original document.

### Claim 2 (depends on 1)

An image forming apparatus according to claim 1, wherein said forming means is arranged to form the latent image on said photosensitive medium based on a light image from the original document placed on said platen.

### Claim 3 (depends on 2)

An image forming apparatus according to claim 2, wherein said forming means includes an optical member for focusing the light image from the original document on said photosensitive medium, and means for driving said optical member in accordance with the desired magnification.

### Claim 4 (depends on 1)

An image forming apparatus according to claim 1, wherein each of said sensing means includes a light source for exposing the original document and a photo-receiving means for receiving light from said light source, and said detecting means is arranged to detect the size of the original document based on an output of said photo-receiving means.

### Claim 5 (depends on 1)

An image forming apparatus according to claim 1, wherein said forming means is adapted to form the latent image in a plurality of mutually different magnifications, and said setting means sets a desired one of said plurality of different magnifications.

### Claim 6 (depends on 1)

An image forming apparatus according to claim 1, wherein said removing means comprises a plurality of LEDs illuminating said photosensitive medium.

### Claim 7 (depends on 1)

An image forming apparatus according to claim 1, wherein said photosensitive medium has a rotatable drum configuration.

### Claim 8 (depends on 1)

An image forming apparatus according to claim 1, further comprising generating means for generating timing pulses synchronized with movement of said photosensitive medium and said controlling means controls the operation of said plurality of light sources bases on the timing pulses.