CA1208951A - Solid-state laser scanning system - Google Patents
Solid-state laser scanning systemInfo
- Publication number
- CA1208951A CA1208951A CA000445886A CA445886A CA1208951A CA 1208951 A CA1208951 A CA 1208951A CA 000445886 A CA000445886 A CA 000445886A CA 445886 A CA445886 A CA 445886A CA 1208951 A CA1208951 A CA 1208951A
- Authority
- CA
- Canada
- Prior art keywords
- variations
- lens
- counteract
- photoreceptive
- plane
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/435—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of radiation to a printing material or impression-transfer material
- B41J2/47—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of radiation to a printing material or impression-transfer material using the combination of scanning and modulation of light
- B41J2/471—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of radiation to a printing material or impression-transfer material using the combination of scanning and modulation of light using dot sequential main scanning by means of a light deflector, e.g. a rotating polygonal mirror
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
- G02B26/10—Scanning systems
- G02B26/12—Scanning systems using multifaceted mirrors
- G02B26/127—Adaptive control of the scanning light beam, e.g. using the feedback from one or more detectors
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/0025—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical correction, e.g. distorsion, aberration
- G02B27/0031—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical correction, e.g. distorsion, aberration for scanning purposes
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Laser Beam Printer (AREA)
- Exposure Or Original Feeding In Electrophotography (AREA)
- Dot-Matrix Printers And Others (AREA)
- Facsimile Scanning Arrangements (AREA)
- Mechanical Optical Scanning Systems (AREA)
Abstract
SOLID-STATE LASER SCANNING SYSTEM
Abstract of the Disclosure An optical system for use with solid state laser chips to counteract variations in wavelength produced by solid-state chips, to counteract astigmatism effects common to laser chips, to counteract variations in the distance between the plane of emission of the beam and the plane of a collimating lens, to counteract variations in beam size in perpendicular planes, to counteract variations in the divergence angle of emission common to laser chips, and to counteract tilt variations caused by imperfect reflecting surfaces. The system includes an apertured achromatic doublet lens for collimating the beam, a cylindrical lens, a rotating mirror, and a combination of toroidal and spherical lens.
Abstract of the Disclosure An optical system for use with solid state laser chips to counteract variations in wavelength produced by solid-state chips, to counteract astigmatism effects common to laser chips, to counteract variations in the distance between the plane of emission of the beam and the plane of a collimating lens, to counteract variations in beam size in perpendicular planes, to counteract variations in the divergence angle of emission common to laser chips, and to counteract tilt variations caused by imperfect reflecting surfaces. The system includes an apertured achromatic doublet lens for collimating the beam, a cylindrical lens, a rotating mirror, and a combination of toroidal and spherical lens.
Description
Sl SOLID-ST.~TE LASER SCANNING SYSTE~I
This in~,~ention rela-tes to a laser scanni.ny system and more particularly to a system designed for use with a soli~l-state laser generator.
Background of the Invention Optical scanning syste~s are used in variou~s types of mach~nes and the invention to be described hexein is to a system which can be used in many of these different mach.ines. For illustrative purposes, -the invention will be described in the context of an electrophotographic printing machineO
In electrophotographic printing machines, prints are produced hy creating an electrostatic representation of the print on a photoreceptive surface, developing the ïmage and then fusing the image to print material. In machines which utilize plain bond paper or other ;.mage receiving material not coated with photoreceptive material, the electrophotographic process is of the transfer type where photoreceptive material is placed around a rotating drum or arranged as a belt to be driven by a systam of rollers. In the typical transer process, photorece~tive ~aterial .is passed under a stationary charge generating station to place a relatively uniform electrostatic charge, us-lally several hundred volts, across the ent;.ret~T of the photoreceptive surface. ~lex~,, the photoreceptor is moved to an imaging stat;.on where lt receives .l.ight rays generated by a light source. In electrophotographic printing machines such as the IB~l 6670 Information Distributor, light rays are used to discharge the photoreceptive material in white or hackground areas to relativel.y low levels while areas which are desired to print out as dark areas continue ~2a~ 5~
to carxy high voltage levels aftex -the exposure. In -that manner, the photoreceptive material is caused to bear a charge pattern which corresponds to the printing, shading, etc. which is desired.
Production of the image on the photoreceptive surface can be produced by a scanning optical beam where the desired characters are produced by driving a light generating source from information held in di~ital memory. The generating source may be a laser gun, an array of light-emitting diodes, light modulators, etc. which direct light rays to t,he pho-toreceptor and cause it to bear the desixed charge pattern.
An exarnple of a li~ht scanning and printing system such as is employed in the IBM 6670 Information Distributor is disclosed in U.S. Patent Mo.
3,750,18~. In that s~stem, a lasex beam is directed through a colli~ating lens system and ocused as a line on a rotating mirror. The reflectecl beam is passed through a combination of a toroidal and a spherical lens to focus the line image on the final image plane, that is, the photoxeceptor. The shape of the focused heam on the photorece~tor is designed to be slightly elliptica]. in order to compensate for the dlfferent image forming properties of the optical system in the scan and non--scan dlrections.
The type of light source provided in the IB~l 6670 Information Distxibutor for use with the optical system of the above-xeferenced patent is a helium neon generating source ox a similAr type source which provides a continuous laser beam modulated to carry the digital information desired for reproduction. In the current invention, an optical system is provided which is designed for use with solid-state laser sources where si,gnificantly diff2rent problems are -~`; 2~1i39~
encountered and which require solution in orcler to accurately and economically produce a satisfactory lmage .
The special pxoblems associated with solid-state laser generating sources include changes in the wavelength being produced by the laser chip as the chip aqes or as the chip experiences heat variations in the machine environment in which it is located.
Another problem is a difference in wavelength produced froin one laser chip to another. Because of these factors, the inventors herein describe an optical system which is designed to accommodate changes in wavelength ~roduced by the chip.
Another signif~cant problem which must be addressed is variation in the divergence angle of the laser beam which is produced by different chips and which is produced in different planes b~r the same chip. In addition, an optical system should provide depth of focus to eliminate various problems including astigmatism~ and counteract tilt variations in the surface of the rotating mirror. The s~rstem of this invention also accommodates these factors.
~5 Summarv of the Invention The optical s~stem of the current invention provides an achromatic doublet len~ positioned adjacent to the solid-state laser generating source together with an aperture locate~ just after or just prior to the achromatic doublet lens. The doublet lens collimates the beam and passes it -to a cylindrical lens for focusing the beam onto the surface of a rotating mirror, then through a toroidal lens together with a spherical lens to focus the beam onto a moving photoreceptive surface.
5~
Brie~ Description of the Drawinc3s The above-mentioned and other featllres and objects of this invention anc~ the manner of attaining them will become more apparent and -the invention itself will best he understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, the description of ~hich follows.
FIG. 1 illustrates the paper path of the IBM 6670 Information Distributor.
FI~. 2 is a perspective view of the optical system of the current disclosure which could be usecl in an electrophotographic machine such as that shown in FIG. 1.
FIG. 3 shows a plan view of the optical system.
FIG. 4, comprisecl of FIGS. 4A and 4B, shows an unfolded line drawing of the op-tical system of the current invention in perpendicular planes.
Detailed Description An electrophotographic machine capable of using the instant invention is shown in FIG. l. A drum 11 carries upon its surface photoreceptive material 12 which is charged by charge corona 13 to a rela-tively uniform charge. The optical system of the instant invention shown as module 14 generates light rays 15 which strike the movillg photoreceptive surface at exposure station 16. The lat:ent image produced at exposure station 16 is developed by developer 51 and a transfer is made at transfer station 52 to print receiving materi~l. Any clevelopment material ~L2~ S~
continuing to reside on the surface of photoreceptor 12 after -transfer ls cleaned away at cleaning station 53O The process then repeats for the producti.on of additional prints.
After transfer of the image to the print receivi.ng material at transfer station 52, that material is passed through fu.ser rolls 60 at which the developing materi~l is permanently bonded to the print receiving material. The pri.nt receiving material ls ultimately deposited at a fi.nishing station 17 or ln an exit pocket l8. Other machine elements shown in FIG. 1 include drive motor 90, print material bins 62 and 63, and the elements of an opkical system for imaging an original document when the machine is used as a copier machine instead of as a printer.
A common variation on the electrophotographic process shown in FIG. l involves the use o~ coatea paper where the print paper itself carries a coating OL
photosensitive material. In that technique, the image is presented di.rectlv to the print paper. The paper is sent through a developer and then to a fuser for permanent bonding. Machines of this tvpe avoid the residual cleveloper problem and therefore there is no need for cleaning stations, erase lamps, preclean generating coronas, etc. ~Iowever, the resulting print paper with its special photosensitive coating is more expen.sive than plain bond paper and special coating is considered to detract from the resulting product. As a consequence, coated paper machines are usually favored only for low volume applications or when quality products are not essential. However, the instant invention involving an optical system can be used in either type of machine.
g~
Optical system module 14 is shown in detail in FIG. 2 where a solid-state lase.r chip and a collimating lens are housed in assembly 100. TJaser heam 15 passes from assembly 100 through cylindrical lens 101 -to a rotating mirror 102 wh~ich is produced with a pluralitv of facets, such as facet 103, around the periphery of the mirror~ ~he laser beam is reflected from a single facet, such as facet 103, in such a manner as to scan through an angle ~. As each succeeding facet of rotating mirror 102 rotates into position to xeceive beam 15, another scan through the angle ~ is produced. Upon reflection from the rotating mirror facet, the laser beam is passed through assembly 104 at which a toroidal lens and a spherical lens are used to finally shape the beam and to focus i-t upon the photorecepti~7e surface 12 shown in FIG. 1. It may be noted that assembly 104 could also be composed of a combination of a cylindrical and spherical lens to perform this function. A
20 beam-fold mirror 105 is shown in both FIGS. 1 and 2 i].lustrating the final foldincJ mechanism to direct the laser beam to the photoreceptive surface. Motor 106 is provided to drive ~he rotating mirror 102 while a start-of-scan mirror 107 is providecl to direct the laser heam to a start-of-scan detector lns .
FIG. 3 illustrates a plan view of the optical sYStem with laser beam emi.s~ion from the solid--state chip shown at 200. The achromatic doublet lens 201 is placed, as an example, approximately 10 millimeters from the plane of laser beam emission 200. An aperture 202 is shown posltioned just beyond doublet lens 201 but can be just prior to that lens if cle.sired. A collimated heam produced by lens 201 is passed through cylindrical lens 101 for focuslng the laser onto the surface of rotatin~ mirror 102. The beam is reflected from mirror 102 through a toroidal lens 203 and spherical lens 204 to a photoreceptive surface shown at plane 205. The plane of the fold mirror 105 is shown at 2b6.
FIGS. 4A and 4B show a completely unfolded schematic representation of the optical path of the system shown in FIGS. 2 and 3. FIG. 4A shows the beam 15 in a first plane, for example, horizontal, while FIG. 4B
shows the beam 15 in a second perpendicular plane, for e~ample, vertical.
In FIG. 4A, laser chip 200 emits laser beam 15 at a relatively wide divergence angle as compared to the divergence angl~ shown in FIG. 4B. Correspondingly~
aperture 202 contains a relatively wide opening in FIG. 4A as compared to the aperture opening shown in FIG. 4B. The elliptical shape of aperture 202 is important in compensating for the various divergence angles in the perpendicular planes to enahle the production of correct spot size at the image plane.
Aperture 202 also corrects for different divergence angles of emission from chip to chip thu.s providing an optical system which features improved assemhly and service.
Note that the point of laser beam emission in FIG. 4A
is at the surface of chip 200 while the point of emission in FIG. 4B is somewhat removed from the surface and appears located in the material itself.
This illustrates an astigmatism which is not uncommon to solid~state laser chi.ps. The combination of this douhlet lens and aperture provi.des a depth of focus which tends to counteract astigmatism in the formulation of beam 15.
~L2~
~ - 8 An additional benefit of the greater clepth of focus provided by the dou~let lens and aperture is to counteract changes in the distance between the plane of laser emission and the plane o. the doublet lensO
Such changes may be due to variations to the temperature of the mountings of these elements.
FIGS. 4A and 4B show that the elliptical beam 15 is collimated in the horizontal plane but may not be fully collimated in the vertica~ plane. The combination of cylindrical ]ens 101, toroiclal lens 203 and spherical lens 204 ~ompensate for this factor and produce the. desired spot size at image plane 12~
Note that cvlindrical lens ].01 passes the colllmated beam 15 in the horiæonta]. plane and focuses beam 15 in the vertical plane to a poi.nt at or ncar the surface of rotating mirrbr 102. In that manner the laser beam appears as a line of light at the facets of mirror 102 and is reflected therefrom to toroidal 20 lens 203 and spherical lens 204 for focusing the beam. The plane of the fold mirror 105 is shown at 206.
As ~reviously mentioned, the wavelength of soli~-state laser chip 200 is subject to change as the chip ages, as it is suhjected to heat, or if the need arises to replace the chip. The use of achromatic doublet lens 201 is important in a solid-state laser system in order to assure that a 30 substantial degree of insensitivity is provided to changes in wavelength. The achromatic doublet lens 201 compensates for changes in the wavelength of laser 200 by maintaining a relatively constant focal length despite changes in wavelength. Additionally, the use of the doublet lens 201 together with the aperture 2.02 provides a system for shaping the beam to the correct collimated beam size regardless of the ~L2~95~ -, ~
laser divergerlce angle ~Jhich may be emitted from laser chip 200. The doublet lens and aperture combination also provides greater depth of focus to compensate for variation in the distance bet~ieen the point of laser emissi~,n and the plane of the doublet lens which ma~ be caused by e~pansion of the mountings as mentioned above. Finally, the improved depth of focus helps to counteract astigmatism effects. Thus, the optical system of the instant invention provides a solution to those several problems encountered in using solid-state laser sources in scanning systems.
t~hile the invention has been particularl~ sho~in and described ~ith reference to a preferred embodiment thereof, it will be understood by those skilled i.n the art that the foregoing and other changes in form and details may be made therein ~ithout departing from the spirit and scope of the invention.
This in~,~ention rela-tes to a laser scanni.ny system and more particularly to a system designed for use with a soli~l-state laser generator.
Background of the Invention Optical scanning syste~s are used in variou~s types of mach~nes and the invention to be described hexein is to a system which can be used in many of these different mach.ines. For illustrative purposes, -the invention will be described in the context of an electrophotographic printing machineO
In electrophotographic printing machines, prints are produced hy creating an electrostatic representation of the print on a photoreceptive surface, developing the ïmage and then fusing the image to print material. In machines which utilize plain bond paper or other ;.mage receiving material not coated with photoreceptive material, the electrophotographic process is of the transfer type where photoreceptive material is placed around a rotating drum or arranged as a belt to be driven by a systam of rollers. In the typical transer process, photorece~tive ~aterial .is passed under a stationary charge generating station to place a relatively uniform electrostatic charge, us-lally several hundred volts, across the ent;.ret~T of the photoreceptive surface. ~lex~,, the photoreceptor is moved to an imaging stat;.on where lt receives .l.ight rays generated by a light source. In electrophotographic printing machines such as the IB~l 6670 Information Distributor, light rays are used to discharge the photoreceptive material in white or hackground areas to relativel.y low levels while areas which are desired to print out as dark areas continue ~2a~ 5~
to carxy high voltage levels aftex -the exposure. In -that manner, the photoreceptive material is caused to bear a charge pattern which corresponds to the printing, shading, etc. which is desired.
Production of the image on the photoreceptive surface can be produced by a scanning optical beam where the desired characters are produced by driving a light generating source from information held in di~ital memory. The generating source may be a laser gun, an array of light-emitting diodes, light modulators, etc. which direct light rays to t,he pho-toreceptor and cause it to bear the desixed charge pattern.
An exarnple of a li~ht scanning and printing system such as is employed in the IBM 6670 Information Distributor is disclosed in U.S. Patent Mo.
3,750,18~. In that s~stem, a lasex beam is directed through a colli~ating lens system and ocused as a line on a rotating mirror. The reflectecl beam is passed through a combination of a toroidal and a spherical lens to focus the line image on the final image plane, that is, the photoxeceptor. The shape of the focused heam on the photorece~tor is designed to be slightly elliptica]. in order to compensate for the dlfferent image forming properties of the optical system in the scan and non--scan dlrections.
The type of light source provided in the IB~l 6670 Information Distxibutor for use with the optical system of the above-xeferenced patent is a helium neon generating source ox a similAr type source which provides a continuous laser beam modulated to carry the digital information desired for reproduction. In the current invention, an optical system is provided which is designed for use with solid-state laser sources where si,gnificantly diff2rent problems are -~`; 2~1i39~
encountered and which require solution in orcler to accurately and economically produce a satisfactory lmage .
The special pxoblems associated with solid-state laser generating sources include changes in the wavelength being produced by the laser chip as the chip aqes or as the chip experiences heat variations in the machine environment in which it is located.
Another problem is a difference in wavelength produced froin one laser chip to another. Because of these factors, the inventors herein describe an optical system which is designed to accommodate changes in wavelength ~roduced by the chip.
Another signif~cant problem which must be addressed is variation in the divergence angle of the laser beam which is produced by different chips and which is produced in different planes b~r the same chip. In addition, an optical system should provide depth of focus to eliminate various problems including astigmatism~ and counteract tilt variations in the surface of the rotating mirror. The s~rstem of this invention also accommodates these factors.
~5 Summarv of the Invention The optical s~stem of the current invention provides an achromatic doublet len~ positioned adjacent to the solid-state laser generating source together with an aperture locate~ just after or just prior to the achromatic doublet lens. The doublet lens collimates the beam and passes it -to a cylindrical lens for focusing the beam onto the surface of a rotating mirror, then through a toroidal lens together with a spherical lens to focus the beam onto a moving photoreceptive surface.
5~
Brie~ Description of the Drawinc3s The above-mentioned and other featllres and objects of this invention anc~ the manner of attaining them will become more apparent and -the invention itself will best he understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, the description of ~hich follows.
FIG. 1 illustrates the paper path of the IBM 6670 Information Distributor.
FI~. 2 is a perspective view of the optical system of the current disclosure which could be usecl in an electrophotographic machine such as that shown in FIG. 1.
FIG. 3 shows a plan view of the optical system.
FIG. 4, comprisecl of FIGS. 4A and 4B, shows an unfolded line drawing of the op-tical system of the current invention in perpendicular planes.
Detailed Description An electrophotographic machine capable of using the instant invention is shown in FIG. l. A drum 11 carries upon its surface photoreceptive material 12 which is charged by charge corona 13 to a rela-tively uniform charge. The optical system of the instant invention shown as module 14 generates light rays 15 which strike the movillg photoreceptive surface at exposure station 16. The lat:ent image produced at exposure station 16 is developed by developer 51 and a transfer is made at transfer station 52 to print receiving materi~l. Any clevelopment material ~L2~ S~
continuing to reside on the surface of photoreceptor 12 after -transfer ls cleaned away at cleaning station 53O The process then repeats for the producti.on of additional prints.
After transfer of the image to the print receivi.ng material at transfer station 52, that material is passed through fu.ser rolls 60 at which the developing materi~l is permanently bonded to the print receiving material. The pri.nt receiving material ls ultimately deposited at a fi.nishing station 17 or ln an exit pocket l8. Other machine elements shown in FIG. 1 include drive motor 90, print material bins 62 and 63, and the elements of an opkical system for imaging an original document when the machine is used as a copier machine instead of as a printer.
A common variation on the electrophotographic process shown in FIG. l involves the use o~ coatea paper where the print paper itself carries a coating OL
photosensitive material. In that technique, the image is presented di.rectlv to the print paper. The paper is sent through a developer and then to a fuser for permanent bonding. Machines of this tvpe avoid the residual cleveloper problem and therefore there is no need for cleaning stations, erase lamps, preclean generating coronas, etc. ~Iowever, the resulting print paper with its special photosensitive coating is more expen.sive than plain bond paper and special coating is considered to detract from the resulting product. As a consequence, coated paper machines are usually favored only for low volume applications or when quality products are not essential. However, the instant invention involving an optical system can be used in either type of machine.
g~
Optical system module 14 is shown in detail in FIG. 2 where a solid-state lase.r chip and a collimating lens are housed in assembly 100. TJaser heam 15 passes from assembly 100 through cylindrical lens 101 -to a rotating mirror 102 wh~ich is produced with a pluralitv of facets, such as facet 103, around the periphery of the mirror~ ~he laser beam is reflected from a single facet, such as facet 103, in such a manner as to scan through an angle ~. As each succeeding facet of rotating mirror 102 rotates into position to xeceive beam 15, another scan through the angle ~ is produced. Upon reflection from the rotating mirror facet, the laser beam is passed through assembly 104 at which a toroidal lens and a spherical lens are used to finally shape the beam and to focus i-t upon the photorecepti~7e surface 12 shown in FIG. 1. It may be noted that assembly 104 could also be composed of a combination of a cylindrical and spherical lens to perform this function. A
20 beam-fold mirror 105 is shown in both FIGS. 1 and 2 i].lustrating the final foldincJ mechanism to direct the laser beam to the photoreceptive surface. Motor 106 is provided to drive ~he rotating mirror 102 while a start-of-scan mirror 107 is providecl to direct the laser heam to a start-of-scan detector lns .
FIG. 3 illustrates a plan view of the optical sYStem with laser beam emi.s~ion from the solid--state chip shown at 200. The achromatic doublet lens 201 is placed, as an example, approximately 10 millimeters from the plane of laser beam emission 200. An aperture 202 is shown posltioned just beyond doublet lens 201 but can be just prior to that lens if cle.sired. A collimated heam produced by lens 201 is passed through cylindrical lens 101 for focuslng the laser onto the surface of rotatin~ mirror 102. The beam is reflected from mirror 102 through a toroidal lens 203 and spherical lens 204 to a photoreceptive surface shown at plane 205. The plane of the fold mirror 105 is shown at 2b6.
FIGS. 4A and 4B show a completely unfolded schematic representation of the optical path of the system shown in FIGS. 2 and 3. FIG. 4A shows the beam 15 in a first plane, for example, horizontal, while FIG. 4B
shows the beam 15 in a second perpendicular plane, for e~ample, vertical.
In FIG. 4A, laser chip 200 emits laser beam 15 at a relatively wide divergence angle as compared to the divergence angl~ shown in FIG. 4B. Correspondingly~
aperture 202 contains a relatively wide opening in FIG. 4A as compared to the aperture opening shown in FIG. 4B. The elliptical shape of aperture 202 is important in compensating for the various divergence angles in the perpendicular planes to enahle the production of correct spot size at the image plane.
Aperture 202 also corrects for different divergence angles of emission from chip to chip thu.s providing an optical system which features improved assemhly and service.
Note that the point of laser beam emission in FIG. 4A
is at the surface of chip 200 while the point of emission in FIG. 4B is somewhat removed from the surface and appears located in the material itself.
This illustrates an astigmatism which is not uncommon to solid~state laser chi.ps. The combination of this douhlet lens and aperture provi.des a depth of focus which tends to counteract astigmatism in the formulation of beam 15.
~L2~
~ - 8 An additional benefit of the greater clepth of focus provided by the dou~let lens and aperture is to counteract changes in the distance between the plane of laser emission and the plane o. the doublet lensO
Such changes may be due to variations to the temperature of the mountings of these elements.
FIGS. 4A and 4B show that the elliptical beam 15 is collimated in the horizontal plane but may not be fully collimated in the vertica~ plane. The combination of cylindrical ]ens 101, toroiclal lens 203 and spherical lens 204 ~ompensate for this factor and produce the. desired spot size at image plane 12~
Note that cvlindrical lens ].01 passes the colllmated beam 15 in the horiæonta]. plane and focuses beam 15 in the vertical plane to a poi.nt at or ncar the surface of rotating mirrbr 102. In that manner the laser beam appears as a line of light at the facets of mirror 102 and is reflected therefrom to toroidal 20 lens 203 and spherical lens 204 for focusing the beam. The plane of the fold mirror 105 is shown at 206.
As ~reviously mentioned, the wavelength of soli~-state laser chip 200 is subject to change as the chip ages, as it is suhjected to heat, or if the need arises to replace the chip. The use of achromatic doublet lens 201 is important in a solid-state laser system in order to assure that a 30 substantial degree of insensitivity is provided to changes in wavelength. The achromatic doublet lens 201 compensates for changes in the wavelength of laser 200 by maintaining a relatively constant focal length despite changes in wavelength. Additionally, the use of the doublet lens 201 together with the aperture 2.02 provides a system for shaping the beam to the correct collimated beam size regardless of the ~L2~95~ -, ~
laser divergerlce angle ~Jhich may be emitted from laser chip 200. The doublet lens and aperture combination also provides greater depth of focus to compensate for variation in the distance bet~ieen the point of laser emissi~,n and the plane of the doublet lens which ma~ be caused by e~pansion of the mountings as mentioned above. Finally, the improved depth of focus helps to counteract astigmatism effects. Thus, the optical system of the instant invention provides a solution to those several problems encountered in using solid-state laser sources in scanning systems.
t~hile the invention has been particularl~ sho~in and described ~ith reference to a preferred embodiment thereof, it will be understood by those skilled i.n the art that the foregoing and other changes in form and details may be made therein ~ithout departing from the spirit and scope of the invention.
Claims (6)
1. An optical system in combination with a semicon-ductor laser light source for producing a light beam, said system being adapted to scan said eight beam produced by said source across a photoreceptive surface, comprising:
said semiconductor laser light source for producing said light beam;
an achromatic lens means to receive light produced by said light source and for compensating variations in the wavelength of light produced by said light source, said variations occurring over a period of time;
reflecting means for reflecting said beam to move said beam in a scanning fashion;
a cylindrical lens means for receiving said beam from said achromatic lens means and for focusing said beam onto the surface of said reflecting means; and a combination of lenses to receive said beam reflected from said reflecting means to focus said beam onto said photoreceptive surface.
said semiconductor laser light source for producing said light beam;
an achromatic lens means to receive light produced by said light source and for compensating variations in the wavelength of light produced by said light source, said variations occurring over a period of time;
reflecting means for reflecting said beam to move said beam in a scanning fashion;
a cylindrical lens means for receiving said beam from said achromatic lens means and for focusing said beam onto the surface of said reflecting means; and a combination of lenses to receive said beam reflected from said reflecting means to focus said beam onto said photoreceptive surface.
2. The optical system of claim 1 wherein said achromatic lens means is a doublet and which functions to collimate said beam for transmission to said cylindrical lens.
3. The optical system of claim 2 wherein said re-flecting means is a rotating mirror.
4. The optical system of claim 3 wherein said com-bination of lenses includes a toroidal and a spherical lens.
5. The optical system of claim 1 wherein said achromatic lens means further includes an aperture, and wherein said achromatic lens means functions to counteract astigmatism effects, functions to counteract variations in the distance between the plane of emission of said beam and the plane of said achromatic lens means, functions to counteract variations in the beam size in perpendicular planes and functions to counteract variations in the diver-gence angle of emission of said beam from said light source.
6. In an electrophotographic printing machine having photoreceptive material mounted on supporting means;
motive means connected to said supporting means to cause said photoreceptive material to move in a cyclic manner;
charge generating means for charging said photoreceptive material;
developing means for developing said image;
transfer means for transferring said image to print receiving material; and fuser means for fusing the transferred image to said print receiving material;
an exposure means for selectively discharging said photoreceptive material, said exposure means including a semiconductor laser chip for producing a light beam modulated according to digitized information desired for reproduction, an achromatic doublet lens and aperture means for receiving said beam from said chip and for compensating variations in wavelength of the light beam produced by said laser chip, said variations occurring over a period of time, for counteracting astigmatism effects, for counteracting variations in the distance between the plane of emission of said beam and the plane of said achromatic doublet lens and aperture means, for counteracting variations in beam size in perpendicular planes, for counteracting variations in the divergence angle of emission of said beam from said laser chip, and for collimating said light beam, a cylindrical lens means for receiving said collimated light beam and focusing said beam onto a moving reflection surface, and a combination of lenses for receiving said beam from said moving reflection surface and focusing said beam onto said photoreceptive surface such that said beam repeatedly scans across said surface to produce an image thereon;
whereby a print is produced to visually reproduce that information used to modulate said beam.
motive means connected to said supporting means to cause said photoreceptive material to move in a cyclic manner;
charge generating means for charging said photoreceptive material;
developing means for developing said image;
transfer means for transferring said image to print receiving material; and fuser means for fusing the transferred image to said print receiving material;
an exposure means for selectively discharging said photoreceptive material, said exposure means including a semiconductor laser chip for producing a light beam modulated according to digitized information desired for reproduction, an achromatic doublet lens and aperture means for receiving said beam from said chip and for compensating variations in wavelength of the light beam produced by said laser chip, said variations occurring over a period of time, for counteracting astigmatism effects, for counteracting variations in the distance between the plane of emission of said beam and the plane of said achromatic doublet lens and aperture means, for counteracting variations in beam size in perpendicular planes, for counteracting variations in the divergence angle of emission of said beam from said laser chip, and for collimating said light beam, a cylindrical lens means for receiving said collimated light beam and focusing said beam onto a moving reflection surface, and a combination of lenses for receiving said beam from said moving reflection surface and focusing said beam onto said photoreceptive surface such that said beam repeatedly scans across said surface to produce an image thereon;
whereby a print is produced to visually reproduce that information used to modulate said beam.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/472,430 US4538895A (en) | 1983-03-07 | 1983-03-07 | Scanning optical system for use with a semiconductor laser generator |
| US472,430 | 1990-01-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1208951A true CA1208951A (en) | 1986-08-05 |
Family
ID=23875477
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000445886A Expired CA1208951A (en) | 1983-03-07 | 1984-01-23 | Solid-state laser scanning system |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4538895A (en) |
| EP (1) | EP0121033B1 (en) |
| JP (1) | JPS59193414A (en) |
| CA (1) | CA1208951A (en) |
| DE (1) | DE3482060D1 (en) |
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| US4753521A (en) * | 1984-09-19 | 1988-06-28 | Siemens Aktiengesellschaft | Lens system for focussing a divergent laser beam |
| JPH0734068B2 (en) * | 1984-11-22 | 1995-04-12 | ミノルタ株式会社 | Imaging optics |
| JPS61191083A (en) * | 1985-02-20 | 1986-08-25 | Canon Inc | Picture recording device |
| DE3603544A1 (en) * | 1986-02-05 | 1987-08-06 | Sick Optik Elektronik Erwin | OPTICAL SCANNER |
| JPH0627904B2 (en) * | 1986-02-06 | 1994-04-13 | 旭光学工業株式会社 | Laser beam scanning optics |
| US4681424A (en) * | 1986-05-20 | 1987-07-21 | Ibm Corporation | Compensation for fine line prints |
| US4820911A (en) * | 1986-07-11 | 1989-04-11 | Photographic Sciences Corporation | Apparatus for scanning and reading bar codes |
| JPH0727123B2 (en) * | 1986-08-21 | 1995-03-29 | ミノルタ株式会社 | Surface tilt correction scanning optical system |
| US4847643A (en) * | 1987-02-19 | 1989-07-11 | Minolta Camera Kabushiki Kaisha | Laser printing system |
| GB2248310A (en) * | 1987-12-09 | 1992-04-01 | Rank Xerox Ltd | Thermal imaging apparatus |
| US4902084A (en) * | 1988-07-29 | 1990-02-20 | Oren Aharon | Optical scanning system |
| US5486944A (en) * | 1989-10-30 | 1996-01-23 | Symbol Technologies, Inc. | Scanner module for symbol scanning system |
| US5304788A (en) * | 1988-10-31 | 1994-04-19 | Symbol Technologies, Inc. | Laser diode scanner with enhanced visibility at an aiming distance relative to the reading distance |
| JP2757308B2 (en) * | 1988-12-16 | 1998-05-25 | キヤノン株式会社 | Light beam scanning optical device |
| EP0378149B2 (en) * | 1989-01-09 | 1998-12-16 | Canon Kabushiki Kaisha | Achromatic-type laser scanning optical system |
| US5270851A (en) * | 1989-01-09 | 1993-12-14 | Canon Kabushiki Kaisha | Achromatic-type laser scanning optical system |
| US4963900A (en) * | 1989-08-01 | 1990-10-16 | International Business Machines Corporation | Multiple laser beam scanning optics |
| US5179465A (en) * | 1990-02-07 | 1993-01-12 | Canon Kabushiki Kaisha | Optical system for light beam scanning |
| JP2623147B2 (en) * | 1990-02-07 | 1997-06-25 | キヤノン株式会社 | Optical system for light beam scanning |
| US5247383A (en) * | 1990-03-20 | 1993-09-21 | Olive Tree Technology, Inc. | Scanner with a post facet lens system |
| US5196957A (en) * | 1990-03-20 | 1993-03-23 | Olive Tree Technology, Inc. | Laser scanner with post-facet lens system |
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| DE69233409T2 (en) * | 1991-05-14 | 2005-03-03 | Seiko Epson Corp. | Image forming apparatus |
| US5859417A (en) * | 1991-06-14 | 1999-01-12 | Symbol Technologies, Inc. | Optical scanners having dual surface optical elements for dual working ranges |
| US6948662B2 (en) | 1991-07-25 | 2005-09-27 | Symbol Technologies, Inc. | Two-dimensional optical code scanner with scanning pattern having region of greater apparent brightness for assisting alignment of scanning pattern |
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| CA2580841C (en) | 1995-03-17 | 2008-08-05 | Symbol Technologies, Inc. | System and method for reading optically encoded information |
| US6029893A (en) * | 1995-05-22 | 2000-02-29 | Symbol Technologies, Inc. | Optical scanner having a reflected light collector including holographic optical elements |
| WO2005107867A2 (en) * | 2004-04-30 | 2005-11-17 | Led Healing Light, Llc | Hand held pulse laser for therapeutic use |
| US20070188875A1 (en) * | 2006-02-10 | 2007-08-16 | Gruhlke Russell W | Refractive lens array for scanner application that reduces lateral tolerance sensitivity |
| US9553422B2 (en) | 2009-08-04 | 2017-01-24 | Medical Coherence Llc | Multiple aperture hand-held laser therapy apparatus |
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| US3626317A (en) * | 1970-02-19 | 1971-12-07 | Ibm | Digitalized scanlaser |
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| JPS4919088U (en) * | 1972-05-27 | 1974-02-18 | ||
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| JPS5488139A (en) * | 1977-12-26 | 1979-07-13 | Olympus Optical Co Ltd | Optical scanner using rotary polyhedral mirror |
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| DE2904435C3 (en) * | 1979-02-06 | 1981-11-12 | Erwin Sick Gmbh Optik-Elektronik, 7808 Waldkirch | Hole detection device for material webs |
| DE2925734C3 (en) * | 1979-06-26 | 1982-06-24 | Erwin Sick Gmbh Optik-Elektronik, 7808 Waldkirch | Optical troubleshooting device for material webs |
| US4379612A (en) * | 1979-09-04 | 1983-04-12 | Canon Kabushiki Kaisha | Scanning optical system having a fall-down correcting function |
| JPS5636622A (en) * | 1979-09-04 | 1981-04-09 | Canon Inc | Scanning optical system having inclination correcting function |
| US4305646A (en) * | 1979-11-19 | 1981-12-15 | Eltra Corporation | Optical system for electro-optical scanner |
| JPS57144516A (en) * | 1981-03-03 | 1982-09-07 | Canon Inc | Scan optical system having fall compensating function |
| US4383755A (en) * | 1982-01-11 | 1983-05-17 | Burroughs Corporation | Unitary, modular, demountable optical system for laser diode/printing copying apparatus |
-
1983
- 1983-03-07 US US06/472,430 patent/US4538895A/en not_active Expired - Lifetime
-
1984
- 1984-01-02 EP EP84100007A patent/EP0121033B1/en not_active Expired
- 1984-01-02 DE DE8484100007T patent/DE3482060D1/en not_active Expired - Fee Related
- 1984-01-23 CA CA000445886A patent/CA1208951A/en not_active Expired
- 1984-01-31 JP JP59014584A patent/JPS59193414A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| DE3482060D1 (en) | 1990-05-31 |
| EP0121033A3 (en) | 1987-09-30 |
| JPS59193414A (en) | 1984-11-02 |
| JPH0443248B2 (en) | 1992-07-16 |
| US4538895A (en) | 1985-09-03 |
| EP0121033A2 (en) | 1984-10-10 |
| EP0121033B1 (en) | 1990-04-25 |
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Legal Events
| Date | Code | Title | Description |
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| MKEX | Expiry |