Optical means for using diode laser arrays in laser multibeam printers and recorders

• US 5,745,153 A
• Filed: 12/07/1992
• Issued: 04/28/1998
• Est. Priority Date: 12/07/1992
• Status: Expired due to Fees

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Kessler, David, Endriz, John G.
• Primary Examiner(s): Yockey, David F.
• Application Number:
  US07/986,207
• Time in Patent Office: 1,968 Days
• Field of Search: 346/107 R, 346/108, 359/710, 359/619, 359/621, 359/626, 359/455, 347/241, 347/244, 347/251
• US Class Current: 347/241
• CPC Class Codes: B41J 2/45 using light-emitting diode [LED] or laser arrays
• CPC Class Codes: B41J 2/451 Special optical means therefor, e.g. lenses, mirrors, focusing means
• CPC Class Codes: G02B 19/0014 at least one surface having optical power
• CPC Class Codes: G02B 19/0057 in the form of a laser diode array, e.g. laser diode bar semiconductor laser arrays with beam combining arrangement H01S5/4012
• CPC Class Codes: G02B 27/09 Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for adapting the beam shape of a laser diode G02B19/0052; adapting the beam shape of an LED G02B19/0061; coupling into light guides using intermediate optical elements G02B6/4204; beam shaping specially adapted for lasers H01S3/005
• CPC Class Codes: G02B 27/0961 Lens arrays lens arrays per se G02B3/0006
• CPC Class Codes: G02B 27/0966 Cylindrical lenses cylindrical lenses per se G02B3/06
• CPC Class Codes: G02B 3/005 arranged along a single direction only, e.g. lenticular sheets G02B3/0043 takes precedence
• CPC Class Codes: G02B 3/0068 arranged in a single integral body or plate, e.g. laminates or hybrid structures with other optical elements G02B5/1885, G02B17/002, G02B30/27 take precedence
• CPC Class Codes: G02B 3/06 with cylindrical or toric faces
• CPC Class Codes: H01S 5/4012 Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms
• CPC Class Codes: H01S 5/4025 Array arrangements, e.g. constituted by discrete laser diodes or laser bar H01S5/42 takes precedence
• CPC Class Codes: H01S 5/4031 Edge-emitting structures

Abstract

A laser multibeam printer or recorder includes a laser diode array generating multiple modulated parallel and diverging light beams with predetermined light intensities at any instant of time. Optical means reduce the divergence of the parallel light beams from the laser diode array by a predetermined amount, do not focus the light beams in a first cross-section direction along a width of the laser diode array, and focus the light beams onto a plane of an entrance pupil of a printing lens in a second cross-sectional direction normal to the first cross-sectional direction. A separate lenslet of a lenslet array directs a corresponding light beam from the laser diode array towards a predetermined area on a plane in front of the printing lens (e.g., the entrance pupil) in the first cross-sectional direction, and focuses the light beam onto the plane of the entrance pupil in a second cross-sectional direction. The printing lens images the light beams at the entrance pupil onto a light sensitive media as a corresponding array of closely-spaced spots of data with predetermined intensities. Various other arrangements using a field lens in combination with the lenslet array with or without a micro lenslet array can be used to process light beams and form an image of closely-spaced spots of light on the light sensitive media.

Claims

1. A laser multibeam printer comprising:

a monolithic laser diode array comprised of a plurality of diode lasers, each of the diode lasers generating a separate one of a plurality of modulated diverging light beams having a predetermined intensity at any instant of time and having predetermined emitting source size, each of the diode lasers spaced from adjacent diode lasers by at least the size of the emitting source size;

a printing lens having an entrance pupil for imaging each of the light beams from the laser diode array at a plane of the entrance pupil onto a light sensitive media as a corresponding compact array of spots of predetermined intensities with a spacing between the spots less than the size of the spot;

optical means for reducing the aperture or divergence of each of the light beams from the plurality of diode lasers by a predetermined amount, and for directing each of the light beams onto the plane of the entrance pupil of the printing lens;

a lenslet array comprising a separate lenslet associated with each of the light beams, wherein each said lenslet directs said associated one of the light beams in a first cross-sectional direction along a width of the laser diode array towards a predetermined area on a plane in front of the printing lens, for focusing each of said light beams in a second cross-sectional direction onto the plane of the entrance pupil, wherein;

the lenslet array substantially collimates each of the light beams from the optical means in the first cross-sectional direction, and directs each of the substantially collimated light beams parallel to each other towards the plane of the entrance pupil; and

a field lens which receives each of the light beams from the lenslet array and focuses and overlaps each of the light beams at the entrance pupil of the printing lens.

2. A laser multibeam printer comprising:

a laser diode array comprised of a plurality of diode lasers, each of the diode lasers generating a separate one of a plurality of modulated diverging light beams of a predetermined intensity at any instant of time and having predetermined emitting source size, each of the diode lasers spaced from adjacent diode lasers by at least the size of the emitting source size;

a printing lens having an entrance pupil for imaging each of the light beams from the laser diode array received at the entrance pupil onto a light sensitive media as a corresponding compact array of spots of predetermined intensities with a spacing between the spots less than the size of the spot;

a first cylinder lens having a first numerical aperture for collecting each of the diverging light beams from the laser diode array, and for reducing the aperture or divergence of each of the beams from the plurality of diode lasers by a predetermined amount;

a second cylinder lens having a second numerical aperture which is less than the first numerical aperture for collecting each of the light beams from the first cylinder lens, for further shaping each of the light beams, and for continuing the direction of each of the light beams onto a plane of the entrance pupil of the printing lens;

a lenslet array comprising a separate lenslet for each of the light beams for directing each of the light beams in a first cross-sectional direction along a width of the laser diode array towards a predetermined area on a plane in front of the printing lens, and for focusing each of the light beams in a second cross-sectional direction normal to the first cross-sectional direction onto the entrance pupil wherein;

the lenslet array substantially collimates each of the light beams from the second cylinder lens in the first cross-sectional direction, and directs each of the substantially collimated light beams parallel to each other towards the plane of the entrance pupil; and

a field lens which receives each of the substantially collimated light beams from the lenslet array and focus and overlap each of the light beams at the entrance pupil of the printing lens.

3. A method of generating an array of closely-spaced spots of predetermined intensities on a light sensitive media in a laser multibeam printer from a plurality of diverging light beams of predetermined intensities generated by a monolithic array of laser diodes, said printer including a printing lens having an entrance pupil, the method comprising the steps of:

(a) transmitting the plurality of light beams generated by the array of laser diodes through an optical means for reducing the aperture or divergence of the light beams from the plurality of diode lasers by a predetermined amount in a first cross-sectional direction;

(b) transmitting the light beams from step (a) through a separate lenslet of a lenslet array for directing each of the light beams in a second cross-sectional direction, normal to the first cross-sectional direction, along a width of the laser diode array towards a predetermined area on a plane of the entrance pupil;

(b1) receiving each of the light beams from the optical means at the lenslet array; and

(b2) arranging the lenslet array for directly focusing and overlapping each of the light beams at the entrance pupil of the printing lens;

(c) focusing each of the light beams from the lenslet array onto the plane of the entrance pupil; and

(d) imaging each of the light beams from the entrance pupil onto a light sensitive media in a corresponding array of closely-spaced spots.

4. A method of generating an array of closely-spaced spots of predetermined intensities on a light sensitive media in a laser multibeam printer from a plurality of diverging light beams of predetermined intensities generated by a monolithic array of laser diodes, said printer including a printing lens having an entrance pupil, the method comprising the steps of:

intensities generated by a monolithic array of laser diodes, said printer including a printing lens having an entrance pupil, the method comprising the steps of;

(a) transmitting each of the plurality of light beams generated by the array of laser diodes through an optical means for reducing the aperture or divergence of each of the light beams from the plurality of diode lasers by a predetermined amount in a first cross-sectional direction;

(a1) forming the plurality of diode lasers of the laser diode array into a plurality of subarrays of closely-spaced diode lasers for forming separate multimode light sources generating separate multimode light beams, each of the subarrays being driven by a separate current source, and each of the diode lasers of a subarray being driven concurrently;

(a2) transmitting each of the plurality of multimode light beams generated by the subarrays of laser diodes through a first cylinder lens having a numerical aperture for collecting the diverging light beams from the laser diode array, and for reducing the aperture of divergence of each of the light beams from the plurality of diode lasers by a predetermined amount; and

(a3) collecting each of the light beams from the first cylinder lens by a second cylinder lens having a second numerical aperture which is less than the first numerical aperture for further shaping the light beams, and for continuing the direction of the light beams onto a plane of the entrance pupil of the printing lens;

(b) transmitting each of the light beams from step (a) through a separate lenslet of a lenslet array for directing each of the light beams in a second cross-sectional direction, normal to the first cross-sectional direction, along a width of the laser diode array towards a predetermined area on a plane of the entrance pupil;

(c) focusing each of the light beams from the lenslet array onto the plane of the entrance pupil; and

(d) imaging each of the light beams from the entrance pupil onto a light sensitive media in a corresponding array of closely-spaced spots.

5. A method of generating an array of closely-spaced spots of predetermined intensities on a light sensitive media in a laser multibeam printer from a plurality of diverging light beams of predetermined intensities generated by a monolithic array of laser diodes, said printer including a printing lens having an entrance pupil, the method comprising the steps of:

(a) transmitting each of the plurality of light beams generated by the array of laser diodes through an optical means for reducing the aperture or divergence of each of the light beams from the plurality of diode lasers by a predetermined amount in a first cross-sectional direction;

(a1) forming the plurality of diode lasers of the laser diode array into a plurality of subarrays of closely-spaced diode lasers for forming separate multimode light sources generating separate multimode light beams, each of the subarrays being driven by a separate current source, and each of the diode lasers of a subarray being driven concurrently;

(a2) transmitting each of the plurality of multimode light beams generated by the subarrays of laser diodes through a first cylinder lens having a numerical aperture for collecting the diverging light beams from the laser diode array, and for reducing the aperture of divergence of each of the light beams from the plurality of diode lasers by a predetermined amount; and

(a3) collecting each of the light beams from the first cylinder lens by a second cylinder lens having a second numerical aperture which is lass than the first numerical aperture for further shaping the light beams, and for continuing the direction of the light beams onto a plane of the entrance pupil of the printing lens;

(b) transmitting each of the light beams from step (a) through a separate lenslet of a lenslet array for directing each of the light beams in a second cross-sectional direction, along a width of the laser diode array towards a predetermined area on the plane of the entrance pupil;

(c) focusing each of the light beams from the lenslet array onto the plane of the entrance pupil; and

(d) imaging each of the light beams from the entrance pupil onto a light sensitive media in a corresponding array of closely-spaced spots.