GB2079049A - Light emitting diode assembly - Google Patents

Light emitting diode assembly Download PDF

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Publication number
GB2079049A
GB2079049A GB8119412A GB8119412A GB2079049A GB 2079049 A GB2079049 A GB 2079049A GB 8119412 A GB8119412 A GB 8119412A GB 8119412 A GB8119412 A GB 8119412A GB 2079049 A GB2079049 A GB 2079049A
Authority
GB
United Kingdom
Prior art keywords
led
light emitting
monoliths
sites
assembly
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.)
Granted
Application number
GB8119412A
Other versions
GB2079049B (en
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Pitney Bowes Inc
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Pitney Bowes Inc
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Filing date
Publication date
Application filed by Pitney Bowes Inc filed Critical Pitney Bowes Inc
Publication of GB2079049A publication Critical patent/GB2079049A/en
Application granted granted Critical
Publication of GB2079049B publication Critical patent/GB2079049B/en
Expired legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/024—Details of scanning heads ; Means for illuminating the original
    • H04N1/032—Details of scanning heads ; Means for illuminating the original for picture information reproduction
    • H04N1/036—Details of scanning heads ; Means for illuminating the original for picture information reproduction for optical reproduction
    • 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
    • B41J2/447—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 arrays of radiation sources
    • B41J2/45—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 arrays of radiation sources using light-emitting diode [LED] or laser arrays
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L25/00—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof
    • H01L25/03—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes
    • H01L25/04—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers
    • H01L25/075—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers the devices being of a type provided for in group H01L33/00
    • H01L25/0753—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers the devices being of a type provided for in group H01L33/00 the devices being arranged next to each other
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/0001—Technical content checked by a classifier
    • H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Computer Hardware Design (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Signal Processing (AREA)
  • Multimedia (AREA)
  • Optics & Photonics (AREA)
  • Health & Medical Sciences (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Toxicology (AREA)
  • Led Device Packages (AREA)
  • Led Devices (AREA)
  • Printers Or Recording Devices Using Electromagnetic And Radiation Means (AREA)
  • Dot-Matrix Printers And Others (AREA)
  • Devices For Indicating Variable Information By Combining Individual Elements (AREA)
  • Optical Couplings Of Light Guides (AREA)

Abstract

An assembly of monoliths 16 containing light emitting diodes 18 (LED's) yields a relatively long array of LED's with high light density and a contiguous set of light centers. Each monolith has two parallel rows of light emitting diodes, and the light emitting diodes of one row are laterally offset towards to the light emitting diodes of the adjacent row to give a higher light density than would be the case if they were not so offset. A fiber optic cover 24 is placed over the exposed surfaces of the LED's to limit escape of light and to protect the LED's from damage. A gel 28 having a relatively high refractive index is applied between the LED's and the fiber optic cover. The assembly may be used in apparatus for electronically recording data using a xerographic machine. <IMAGE>

Description

SPECIFICATION Light emitting diode assembly This invention relates to a light emitting diode assembly.
Light emitting diodes (LED's) have a multiplicity of uses, among which is the application of light in the printing industry. For example, LED's may be used in combination with xerographic copiers, photographic film, and the like for the purpose of recording an image of a message that is transmitted electronically.
The use of LED's for this purpose has certain drawbacks. Primarily, high density light is required in such printing applications in order to obtain good contrast and high resolution, but the light output of individual LED's is not high. Consequently, a large number of LED's must be placed in a small area to provide the required high light density. This has proved difficult to achieve because of the size constraints imposed by the crystalline structure involved. More specifically, a major drawback to the use of LED's is that the length of the monoliths from which LED's are made is limited. This is because the LED's are formed upon monoliths that are of monocrystalline form. Because of the methods required to form the monocrystalline material, there is a limitation upon the size of monoliths which can be made.Present techniques of manufacturing can achieve a monocrystalline boule three inches in diameter, thus limiting the maximum length of a monlith to approximately three inches in length. The most commonly commercially used crystalline boules for LED fabrication are only somewhat larger than one inch in diameter, thus placing a greater limitation on the possible length of an LED array. Many expedients and techniques have been tried and used in attempts to overcome these shortcomings, but to date none has been completely satisfactory.
Another problem associated with the use of LED's in the printing industry is their fragile nature, particularly the electrical connections for such LED's. In order to ensure that the amount of light reaching the receiving surface is high, the LED's are placed as close to the surface as possible. This increases the possibility of damage to the LED's when there is relative movement between the receiving surface and the LED's.
According to the invention, there is provided a light emitting diode assembly, comprising: two generally parallel rows of LED sites extending longitudinally on the assembly, a fiber optic cover covering and spaced from the LED sites, and a gel having a refractive index greater than unity disposed between the LED sites and the fiber optic cover.
Also according to the invention, there is provided a light emitting diode assembly comprising: a plurality of elongated monoliths attached in an end-to-end manner, each of said monoliths having longitudinally opposed end surfaces at an angle to the longitudinal direction each of said monoliths having two generally parallel rows of laterally spaced LED sites extending longitudinally thereon, the LED sites of the rows on each monolith being located such that when the monoliths are assembled end-to-end the sites are in a continuous linear array formed by two parallel lines of LED sites.
It has been found that an LED assembly having a high light density may be obtained by forming the LED's within a monolith in rows in such a manner that the individual LED's of one row are laterally staggered relative to the LED's in the other row. In addition, the monoliths from which the assembly is made have their ends cut at an angle and are assembled together so that the units can be joined to form a required length while achieving one contiguous set of centers. In addition, a fiber optic cover is placed over the exposed surface of the LED's so as to transmit light columnarly from the LED to the light receiving surface and to protect the LED's from being damaged by inadvertant contact with the light receiving surface.A gel with a relatively high refractive index is applied between the LED's and the fiber optic cover to counter the effects of the divergent angle of light emitting from the LED's.
The invention will be better understood from the following non-limiting description of an example thereof given with reference to the accompanying drawings in which: Figure 1 shows portions of a pair of adjacent monoliths that incorporate features of the present invention.
Figure 2 shows a partial, cross-sectional view of an LED assembly that incorporates features of the present invention, the assembly being shown in position in relation to a receiving surface.
Figure 3 shows a portion of circuitry for the LED's of the assembly shown in Fig. 1.
Referring now to Figs. 1 and 2, an assembly of monoliths having LED's thereon is shown generally at 10 spaced relative to a surface 12 such as a photoconductive belt or drum made of zinc oxide, selenium, cadmium sulfide and the like. The assembly 10 includes a substrate 14 made of a dielectric material such as aluminum oxide (Al203) with a conductive material 15 applied to portions of the surface thereof. A plurality of n-type monoliths 16 are attached to the conductive material 15 by an adhesive 17 such as a silver epoxy. The monoliths 16 are made of a material such as gallium arsenide and have a number of doped locations to create p-type sites 18 which in combination with the monolith define light emitting diode (LED's).The doping is accomplished in such a fashion that the p-type sites of LED's 18 are located along two rows, each of which is substantially parallel the longitudinal edge of a monolith 16. The LED sites 18 of one row are laterally offset (staggered) relative to the LED's of the opposite row, as seen in Fig. 1. Although the LED sites are shown as being circular, it will be appreciated that non-circular sites, such as elliptical, may be fashioned for occasions when non-square resolution is required. According to a preferred embodiment of the invention, a one inch length would have eight monoliths 16 with thirty-two LED sites situated on each monolith. The monoliths 16 are joined together at their ends to form an assembly 10 of the required length. For example, if an eight inch assembly is required, sixty-four monoliths would be assembled end to end to provide 2048 LED sites 18.
A metallic coating 20 is deposited upon the monolith 16b at the location of each of the LED sites 18, an open portion or aperture being formed in each coating to expose the LED's. A lead 22 provides electrical connection between the conductive material 15 and the metallic coatings 20 so as to allow power to be supplied to each LED. The leads 22 may be either soldered or epoxy bonded to the conductive material 15 and metallic coatings 20. A fiber optic cover 24 is placed over the length of the monoliths 16 intermediate the monoliths and the photoconductive surface 12. The fiber optic cover 24 has relief portions 25 that extend the length of the cover and are located above the locations where the leads 22 are connected to the metallic coatings 20. The fiber optic cover 24 may be made of either glass or methylmethacrylate.A gel 28 having a refractive index greater than one is applied between the LED's 18 and the fiber optic cover 24. Preferably, the gel is polydimethyl siloxane which has a refractive index of 1.465.
The assemblies 10 are made up of a plurality of monoliths 16 each having a diagonal cut at both of its ends 26 thereof. The diagonal ends 26 preferably are in a plane at an angle to the plane of the monoliths 16, the most preferred angle being about 60 degrees.
An advantage of the construction as illustrated in Fig. 1 is that a high light density is obtained by having the LED's 18 of one row being placed as illustrated in relation to the LED's of the adjacent row. More specifically, the two rows of LED's 18 extend longitudinally with the LED's of one row being laterally offset relative to the LED's of the other row.
This arrangement gives the appearance to the surface 12 of a single continuous line of light.
The linear array of LED's is maintained from one monolith 16 to the next, i.e. across the ends 26, so that the LED's are linearly arranged in a series of monoliths. More specifically, after a crystal boule is drawn, it has a cylindrical shape. It is then cut into a number of thin wafers having the shape of thin discs.
Next, the sites 18 are doped to produce the ptype junction and the metal coating 20 is deposited upon the LED's as shown in Fig. 1.
The discs are then cut into monoliths with a saw that typically results in a three thousands of an inch wide cut. With the diagonal cut, none of the sites 18 is damaged and the monolith 16 may be assembled with others to give the appearance of one continuous assembly having a uniform distribution of LED's along its entire length. Although only two rows of LED's 18 are shown, it will be appreciated that a larger number of rows may be included. Another way of obtaining the diagonal cut is to cut the monoliths by a laser scoring procedure. By driving a laser with a stepper motor controlled by a microprocessor, a plurality of steps can be formed which match a plurality of steps cut on an adjacent monolith. The monoliths would then be assembled in an end-to-end manner as described previously.
The advantage achieved in using the fiber optic cover 24 at the face of the LED's 18 is that columnar light is transmitted to the surface 12. A light source such as an LED tends to form a divergent light cone as a result of the light passing through air. By using the fiber optic cover 24 and a gel 28 whose refractive index is greater than that of air, it has been found that the aforementioned loss of light is reduced. Furthermore, the fiber optic cover 24 provides a degree of protection to the LED's which are rather fragile, especially at the bond connection with the leads 22. This protection is particularly important since the LED's must be placed close to the receiving surface 12 in order to enhance resolution.
Referring to Fig. 3, a portion of the circuit used to control input to the LED's 18 on a selective basis is shown. A set of anode rails or bus bars 30 are shown with the individual leads 22 providing connection between the bus bars and the LED's 18, there being a bus bar for each LED in a monolith. A set of cathode rails or bus bars 32 is also provided, each bus bar 32 being connected in parallel to all the LED's 18 of a given monolith 16.
Appropriate controls may be utilized to selectively energise the LED sites 18, but such controls do not form part of the novelty of this invention.

Claims (5)

1. A light emitting diode assembly, comprising: two generally parallel rows of LED sites extending longitudinally on the assembly, a fiber optic cover covering and spaced from the LED sites, and a gel having a refractive index greater than unit disposed between the LED sites and the fiber optic cover.
2. A light emitting diode assembly comprising: a plurality of elongated monoliths attached in an end-to-end manner, each of said monoliths having longitudinally opposed end surfaces at an angle to the longitudinal direction, each of said monoliths having two generally parallel rows of laterally spaced LED sites extending longitudinally thereon, the LED sites of the rows on each monolith being located such that when the monoliths are assembled end-to-end the sites are in a continuous linear array formed by two parallel lines of LED sites.
3. The assembly of claim 2 including a fiber optic cover placed over and spaced from the LED sites.
4. The assembly of claim 3 wherein a gel having a refractive index greater than one is disposed between the LED sites and the fiber optic cover.
5. A light emitting diode assembly substantially as herein described with reference to and as illustrated in the accompanying drawings.
GB8119412A 1980-06-25 1981-06-24 Light emitting diode assembly Expired GB2079049B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US16296880A 1980-06-25 1980-06-25

Publications (2)

Publication Number Publication Date
GB2079049A true GB2079049A (en) 1982-01-13
GB2079049B GB2079049B (en) 1985-02-06

Family

ID=22587886

Family Applications (1)

Application Number Title Priority Date Filing Date
GB8119412A Expired GB2079049B (en) 1980-06-25 1981-06-24 Light emitting diode assembly

Country Status (5)

Country Link
JP (1) JPS5728379A (en)
CA (1) CA1175884A (en)
DE (1) DE3117923A1 (en)
FR (1) FR2485813B1 (en)
GB (1) GB2079049B (en)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0086907A2 (en) * 1982-02-19 1983-08-31 Agfa-Gevaert N.V. Recording apparatus
EP0097261A2 (en) * 1982-06-19 1984-01-04 AEG Olympia Aktiengesellschaft Printer with an optical print head for the linear registration of graphic and text information
US4445132A (en) * 1980-06-13 1984-04-24 Tokyo Shibaura Denki Kabushiki Kaisha LED Module for a flat panel display unit
EP0115088A1 (en) * 1983-01-21 1984-08-08 Agfa-Gevaert N.V. Recording apparatus
EP0125632A1 (en) * 1983-05-10 1984-11-21 Pitney Bowes, Inc. Light emitting diode array and method of producing the same
DE3616530A1 (en) * 1985-05-17 1986-11-20 Alps Electric Co Ltd ARRANGEMENT OF OPTICAL ELEMENTS
US5184114A (en) * 1982-11-04 1993-02-02 Integrated Systems Engineering, Inc. Solid state color display system and light emitting diode pixels therefor
EP0571737A1 (en) * 1992-05-29 1993-12-01 Kabushiki Kaisha Toshiba Image forming apparatus

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS58203071A (en) * 1982-05-21 1983-11-26 Mitsubishi Electric Corp Light emitting diode array
JPS6027565A (en) * 1983-07-25 1985-02-12 Mitsubishi Electric Corp Luminous diode array head and manufacture thereof
JPS60166166U (en) * 1984-04-12 1985-11-05 沖電気工業株式会社 Light emitting element array head
JPH0638516B2 (en) * 1984-06-26 1994-05-18 沖電気工業株式会社 Light emitting element array
JPS6357262A (en) * 1986-08-29 1988-03-11 Fuji Xerox Co Ltd Optical writing apparatus
JP5075789B2 (en) * 2008-10-20 2012-11-21 株式会社アルバック Light irradiation device

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1924209A1 (en) * 1969-05-12 1971-01-14 Beneking Dr Rer Nat Heinz Electro-optical display
US3900864A (en) * 1973-05-17 1975-08-19 Bell Telephone Labor Inc Monolithic led displays
US3877052A (en) * 1973-12-26 1975-04-08 Bell Telephone Labor Inc Light-emitting semiconductor apparatus for optical fibers
DE2414778A1 (en) * 1974-03-27 1975-10-02 Siemens Ag Monolithic luminescent diodes with p- and n- conducting strips - have light output zones on surface, minimising loss by absorption
JPS5117685A (en) * 1974-08-05 1976-02-12 Mitsubishi Electric Corp
JPS5845191B2 (en) * 1976-12-08 1983-10-07 浜松ホトニクス株式会社 photo diode array
JPS5563269A (en) * 1978-11-07 1980-05-13 Matsushita Electric Ind Co Ltd Recording head

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4445132A (en) * 1980-06-13 1984-04-24 Tokyo Shibaura Denki Kabushiki Kaisha LED Module for a flat panel display unit
EP0086907A2 (en) * 1982-02-19 1983-08-31 Agfa-Gevaert N.V. Recording apparatus
EP0086907A3 (en) * 1982-02-19 1984-11-28 Agfa-Gevaert Naamloze Vennootschap Recording apparatus
EP0097261A2 (en) * 1982-06-19 1984-01-04 AEG Olympia Aktiengesellschaft Printer with an optical print head for the linear registration of graphic and text information
EP0097261A3 (en) * 1982-06-19 1985-05-15 Olympia Werke Ag Printer with an optical print head for the linear registration of graphic and text information
US5184114A (en) * 1982-11-04 1993-02-02 Integrated Systems Engineering, Inc. Solid state color display system and light emitting diode pixels therefor
EP0115088A1 (en) * 1983-01-21 1984-08-08 Agfa-Gevaert N.V. Recording apparatus
EP0125632A1 (en) * 1983-05-10 1984-11-21 Pitney Bowes, Inc. Light emitting diode array and method of producing the same
DE3616530A1 (en) * 1985-05-17 1986-11-20 Alps Electric Co Ltd ARRANGEMENT OF OPTICAL ELEMENTS
EP0571737A1 (en) * 1992-05-29 1993-12-01 Kabushiki Kaisha Toshiba Image forming apparatus

Also Published As

Publication number Publication date
FR2485813A1 (en) 1981-12-31
GB2079049B (en) 1985-02-06
DE3117923C2 (en) 1988-07-28
JPH0137862B2 (en) 1989-08-09
DE3117923A1 (en) 1982-04-29
FR2485813B1 (en) 1985-11-15
JPS5728379A (en) 1982-02-16
CA1175884A (en) 1984-10-09

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Legal Events

Date Code Title Description
PE20 Patent expired after termination of 20 years

Effective date: 20010623