# US 4,111,540 A · Field lens for an electrophotographic printing machine

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- Number: US 4,111,540 A
- Document ID: US4111540A
- Status: Granted
- Kind: A
- Application number: 05/687,562
- Filed: 1976-05-17
- Granted: 1978-09-05
- Earliest claimed: 1976-05-17
- Assignees: Xerox Corporation
- Inventors: James E. Bollman
- Web page: https://patentgrep.com/patent/US4111540A

## CPC

- G03G 15/60: {Apparatus which relate to the handling of originals (for photographic purposes in general G03B)}
- G03G 15/011: {for exposing}
- G03G 2215/00185: original at rest
- G03G 2215/00265: Overhead Transparency, i.e. OHP
- G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY

## Abstract

An electrophotographic printing machine in which the platen thereof is a field lens. In the opaque reproduction mode, the original document is positioned on the platen in a light receiving relationship with the illumination system. The presence of the field lens does not interfere with the opaque copying mode of the printing machine. When a transparency is being reproduced, the light image of the transparency is projected through the platen. The field lens converges the diverging light rays of the transparency light image.

## Claims

### Claim 1

An electrophotographic printing machine, including:
a photoconductive member;
means for charging at least a portion of said photoconductive member to a substantially uniform level;
means for illuminating an opaque original document;
a field lens having the opaque original document disposed thereon in a light receiving relationship with light rays transmitted from said illuminating means; and
means for forming a light image of the opaque original document and irradiating the charged portion of said photoconductive member therewith to record thereon an electrostatic latent image of the original document.

### Claim 2

An apparatus for transmitting a transparency light image or for holding an original document, including:
a substantially rigid frame member having an aperture therein;
a field lens mounted in the aperture of said frame member, said field lens being arranged to support the original document thereon when the transparency light image is not being transmitted therethrough and being arranged to transmit the transparency light image therethrough when the original document is not disposed thereon; and
a cover member mounted movably on said frame member, said cover member being mounted movably from an opened position permitting the original document to be disposed on said field lens or the transparency to be copied and to a closed position securing releasably thereon the original document.

### Claim 3 (depends on 2)

An apparatus as recited in claim 2, wherein said cover member includes:
a substantially rigid outer shell; and
a resilient sheet member secured to said outer shell, said resilient sheet member being positioned to contact the original document disposed on said field lens in the closed position.

### Claim 4 (depends on 3)

An apparatus as recited in claim 3, further including resilient means secured to said frame member on the periphery of the aperture therein with said field lens being mounted on said resilient means in the aperture of said frame member.

### Claim 5 (depends on 2)

An apparatus as recited in claim 2, wherein said field lens includes preferably 200 gratings per inch.

### Claim 6

An electrophotographic printing machine for reproducing an opaque original document or a transparency, including:
a photoconductive member;
means for charging at least a portion of said photoconductive member to a substantially uniform level;
means for illuminating the opaque original document;
a field lens arranged to support the opaque original document in a light receiving relationship with light rays transmitted from said illuminating means;
a substantially rigid frame member having an aperture therein, said frame member being mounted in the aperture of the printing machine;
resilient means secured to said frame member on the periphery of the aperture therein with said field lens being mounted on said resilient means in the aperture of said frame member;
means for forming a light image of the opaque original document and irradiating the charged portion of said photoconductive member therewith to record thereon an electrostatic latent image of the original document;
means for projecting a light image of the transparency through said field lens onto the charged portion of said photoconductive member to record thereon an electrostatic latent image of the transparency, said projecting means being inoperative during the reproduction of the original document;
means for modulating the light image of the transparency; and
a composition frame disposed on said field lens in a light receiving relationship with said illuminating means when said projecting means is operative, said forming means exposing the charged portion of said photoconductive member to a light image of said composition frame recording thereon a combined electrostatic latent image comprising the electrostatic latent image of the transparency and the electrostatic latent image of said composition frame.

### Claim 7 (depends on 6)

A printing machine as recited in claim 6, further including a cover member mounted movably on said frame member, said cover member being mounted movably from an opened position permitting the original document to be disposed on said field lens or the transparency to be copied and to a closed position securing releasably thereon the original document.

### Claim 8 (depends on 7)

A printing machine as recited in claim 7, wherein said cover member includes:
a substantially rigid outer shell; and
a resilient sheet member secured to said outer shell, said resilient sheet member being positioned to contact said composition frame disposed on said field lens in the closed position.

### Claim 9 (depends on 6)

A printing machine as recited in claim 6, wherein said field lens includes preferably 200 gratings per inch.

### Claim 10 (depends on 6)

A printing machine as recited in claim 6, wherein said projecting means includes a slide projector arranged to project a light image of the transparency through said field lens.

### Claim 11 (depends on 10)

A printing machine as recited in claim 10, wherein said modulating means includes a screen interposed between said field lens and said composition frame.

### Claim 12 (depends on 11)

A printing machine as recited in claim 11, wherein said forming means includes a lens.

### Claim 13 (depends on 12)

A printing machine as recited in claim 12, wherein said screen member includes a plurality of spaced, soft gray square dots.

### Claim 14 (depends on 13)

A printing machine as recited in claim 13, wherein said screen member preferably includes 85 dots per inch.

### Claim 15 (depends on 14)

A printing machine as recited in claim 14, further including means for filtering the light image of the original document to form a single color light image which irradiates the charged portion of said photoconductive member to record thereon a single color electrostatic latent image.

### Claim 16 (depends on 15)

A printing machine as recited in claim 15, further including:
means for developing the single color electrostatic latent image recorded on said photoconductive member with toner particles complementary in color to the color of the single color light image;
means for transferring the toner powder image from the electrostatic latent image recorded on said photoconductive member to a sheet of support material; and
means for permanently affixing the toner powder image to the sheet of support material.