Modular optical printhead for hard copy printers

• US 4,875,057 A
• Filed: 09/01/1988
• Issued: 10/17/1989
• Est. Priority Date: 09/01/1988
• Status: Expired due to Term

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Pham, Hieu, Ng, Yee S., Hediger, Edwin A.
• Primary Examiner(s): Reynolds, Bruce A.
• Assistant Examiner(s): ROGERS, SCOTT A
• Application Number:
  US07/239,564
• Time in Patent Office: 411 Days
• Field of Search: 346/107 R, 346/160, 358/302
• US Class Current: 347/242
• CPC Class Codes: B41J 2/451 Special optical means therefor, e.g. lenses, mirrors, focusing means

Abstract

Modular optical LED printhead arranged for a fixed focus distance outside the printhead structure. A supporting and registration plate contains a rectangular opening in which the lens is located. The plate is secured to the overall LED supporting structure of the printhead by end members which, with side members, completely seal the LED'"'"'s and connections from contaminants. The registration plate has at least two surfaces thereon which mate with surfaces in the associated apparatus to accurately position the plate. During the alignment process of the printhead, the lens and plate are adjusted to provide a focus at a fixed distance from one of the registration surfaces of the plate. Alignment of the lens across the axis of the LED array is provided by recessed set screws and a shim. Because of the fixed distance from the registration surface, the printhead can be installed in suitably constructed apparatus without further alignment.

Claims

1. A modular printhead assembly for selectively exposing a moving photosensitive surface to provide a latent image, said printhead comprising:

a circuit arrangement including a linear array of light emitting diodes (LED'"'"'s) which extend along a first axis;

a rigid heat sink to which the LED circuit arrangement is connected;

a linear optical lens;

a lens supporting structure non-adjustably attached to said heat sink to form an integral lens-LED combination;

adjustable means for securing the lens to the supporting structure after the lens has been aligned; and

a printed circuit board (PCB) positioned substantially between the heat sink and the supporting structure;

said lens supporting structure also providing means for mounting and registering the aligned printhead in associated apparatus, with said registration allowing the aligned printhead assembly to be interchanged between different apparatus without realignment of the lens.

2. The modular printhead of claim 1 wherein the lens is aligned to focus light from the LED'"'"'s to a fixed distance from the registration position.

3. The modular printhead of claim 1 wherein the supporting structure substantially covers the circuit arrangement to enclose the LED'"'"'s and provide a sealed barrier around the LED'"'"'s.

4. The modular printhead of claim 3 wherein the PCB extends outside the enclosed area for electrical attachment to other circuits and for access to electrical adjustment components on the PCB.

8. The modular printhead of claim 1 wherein the mounting and registering means includes a plate having a rectangular opening therein containing the lens, said plate having at least two perpendicular surfaces thereon precisely dimensioned for accurate positioning of the printhead in the associated apparatus.

5. A modular printhead assembly for selectively exposing a moving photosensitive surface to provide a latent image, said printhead comprising:

a circuit arrangement including a linear array of light emitting diodes (LED'"'"'s) which extend along a first axis;

a rigid heat sink to which the LED circuit arrangement is connected;

a linear optical lens;

means for supporting said lens from said heat sink to form an integral lens-LED combination;

means for securing the lens to the supporting means after the lens has been aligned; and

a printed circuit board (PCB) positioned substantially between the heat sink and the supporting means;

wherein said lens supporting means also provides means for mounting and registering the aligned printhead in associated apparatus, with said registration allowing the aligned printhead assembly to be interchanged between different apparatus without realignment of the lens; and

wherein said lens supporting means includes first and second spacer bars mounted to the PCB and oriented parallel to said first axis, first and second end supports which are connected to the heat sink at opposite ends of the spacer bars and oriented perpendicular to said axis, and a plate having a rectangular opening therein and being positioned across said spacer bars and said end supports.

6. The modular printhead of claim 5 wherein the securing means includes at least one recessed set screw in said plate which forcibly holds the lens in the rectangular opening of the plate.

7. The modular printhead of claim 6 wherein the lens is aligned in one direction by the thickness of a shim between the lens and a surface of the rectangular opening.

9. A modular printhead assembly for selectively exposing a moving photosensitive surface to provide a latent image, said printhead comprising:

a circuit arrangement including a linear array of light emitting diodes (LED'"'"'s) which extend along a first axis;

a rigid heat sink to which the LED circuit arrangement is connected;

a linear optical lens;

means for supporting said lens from said heat sink to form an integral lens-LED combination;

means for securing the lens to the supporting means after the lens has been aligned; and

a printed circuit board (PCB) positioned substantially between the heat sink and the supporting means;

said lens supporting means also providing means for mounting and registering the aligned printhead in associated apparatus, with said registration allowing the aligned printhead assembly to be interchanged between different apparatus without realignment of the lens; and

said mounting and registering means including a plate having a rectangular opening therein containing the lens, said plate having at least two perpendicular surfaces thereon precisely dimensioned for accurate positioning of the printhead in the associated apparatus.

10. The modular printhead of claim 9 wherein one of the precise surfaces is located on the face of the plate which is closest to the photosensitive surface when installed in the associated apparatus, and wherein the other precise surface is located on a face of the plate which extends perpendicular to said first axis.

11. A modular printhead assembly for selectively exposing a moving photosensitive surface to provide a latent image, said printhead comprising:

a circuit arrangement including a linear array of light emitting diodes (LED'"'"'s) which extend along a first axis;

a rigid heat sink to which the LED circuit arrangement is connected;

a linear optical lens and a lens supporting structure non-adjustably attached to the heat sink to form an integral lens-LED combination, said supporting structure enclosing the LED'"'"'s to provide a sealed barrier around the LED'"'"'s;

a printed circuit board (PCB) to which the circuit arrangement is electrically connected, said PCB extending outside the enclosed area for electrical attachment to other circuits and for access to electrical adjustment components on the PCB; and

adjustable means for securing the lens to the supporting structure after the lens has been aligned, said alignment focusing light from the LED'"'"'s to a fixed distance from a registration position;

said lens supporting structure also providing means for mounting and registering the aligned printhead in associated apparatus, with said registration allowing the aligned printhead assembly to be interchanged between different apparatus without realignment of the lens.

12. A modular printhead assembly for selectively exposing a moving photosensitive surface to provide a latent image, said printhead comprising:

a circuit arrangement including a linear array of light emitting diodes (LED'"'"'s) which extend along a first axis;

a rigid heat sink to which the LED circuit arrangement is connected;

a linear optical lens and means for supporting said lens from the heat sink to form an integral lens-LED combination, said supporting means enclosing the LED'"'"'s to provide a sealed barrier around the LED'"'"'s;

a printed circuit board (PCB) to which the circuit arrangement is electrically connected, said PCB extending outside the enclosed area for electrical attachment to other circuits and for access to electrical adjustment components on the PCB; and

means for securing the lens to the supporting means after the lens has been aligned, said alignment focusing light from the LED'"'"'s to a fixed distance from a registration position;

wherein said lens supporting means also provides means for mounting and registering the aligned printhead in associated apparatus, with said registration allowing the aligned printhead assembly to be interchanged between different apparatus without realignment of the lens; and

wherein the lens supporting means includes first and second spacer bars mounted to the PCB and oriented parallel to said first axis, first and second end supports which are connected to the heat sink at opposite ends of the spacer bars and oriented perpendicular to said axis, a plate having a rectangular opening therein and being positioned across said spacer bars and said end supports, with the lens being located within said rectangular opening, said plate having at least two perpendicular surfaces thereon precisely dimensioned for accurate registration of the printhead in the associated apparatus, with one of the precise surfaces being located on the face of the plate which is closest to the photosensitive surface when installed in the associated apparatus, and with the other precise surface being located on a face of the plate which extends parallel to said first axis, at least one recessed set screw positioned in said plate which forcibly holds the lens in the rectangular opening of the plate, and a shim located between the lens and a surface of said rectangular opening for the purpose of aligning the lens in one direction.