Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1999-11-30
2001-11-20
Allen, Stephone B. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C359S627000, C362S327000
Reexamination Certificate
active
06320182
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a light collector for directing light to a concentrated area on a target surface and, in particular, to a linear light collector for an LED array used in an erase lamp in an electrophotographic printer.
(2) Description of the Related Art
In electrophotographic printing, a charge-retentive, photosensitive surface, known as a photoreceptor, is initially charged uniformly. In an exposure step, light either from an original image focused on the photoreceptor or created by the action of digital image data modulating a scanning laser selectably discharges specific areas of the surface to create a latent image. In a development step, toner particles are applied to the latent image. The toner particles adhere only to those areas on the photoreceptor on which an electrostatic charge remains. This developed image on the photoreceptor is then transferred to a print sheet on which the desired print or copy is fixed. After the developed image has been transferred, the photoreceptor is cleaned to remove any toner particles and paper fibers that may adhere to the belt.
In printing process outlined above there are various times, in addition to the exposure step, where it is desirable to discharge the photoreceptor. For example, prior to the transfer step, the photoreceptor is often discharged to reduce the holding charge on the toner and to improve the transfer efficiency. Similarly, during the cleaning step it is desirable to remove any and all residual charge on the photoreceptor prior to the next cycle.
One common method of reducing or removing the charge from the photoreceptor is to expose the photoreceptor to light. In xerographic equipment, what is commonly known as an “erase lamp” or “erase bar” is used to generate a small, well-defined band of light to discharge portions of the photoreceptor. An ideal erase lamp would be capable of selectably discharging the photoreceptor without generating stray light that may interfere with the operation of other portions of the printer. That is, as the performance of many of the elements of a xerographic printer, e.g., corotrons, optical sensors and imagers, are degraded in the presence of stray light, an ideal erase lamp would be efficient and direct substantially all of this light against the photoreceptor in a narrow band, with no unwanted stray light that may illuminate the above-mentioned elements.
A preferred light source for use in erase lamps is a light-emitting diode, or LED. When lit, an LED creates light that emanates from an area that is generally small when compared to the dimensions of the optic elements of a typical lamp and thus creates a near point-source form. A collector is often used to take the light from a line of LEDs and direct the beams therefrom so that the beams appear to be emanating from a single linear light source.
Many devices have been designed for directing light from an array of LEDs to a small linear area on a target surface. U.S. Pat. No. 4,767,172 discloses a collector for an LED array wherein each LED within the array is provided with a linear collector, including a central convex lens portion and an outer parabolic reflecting surface. Light exiting substantially perpendicular to the substrate on which the LED is mounted is applied to the convex lens and collimated, while light exiting substantially parallel to the substrate on which the LED is mounted strikes a parabolic reflecting surface, and is also collimated, resulting in two concentric collimated beams which are directed onto a target surface.
U.S. Pat. No. 5,526,190 discloses an optical element adapted to be interposed between an array of light sources and a target surface. A central cylinder lens collimates light beams from the light source and directs the collimated light beams to a preselected area on the target surface. First and second outer reflective portions, each attached to and extending parallel to the cylinder lens, totally internally reflect light beams from the light source and direct the light beams reflected therein to the target surface.
The above-described devices collect light from an array of LEDs and direct the light to a small linear area on a target surface. However, one drawback associated with the devices described above arises from their shape. In both of the devices the central lens portion is lower in profile than the outer reflecting portion thereby creating a deep cavity or pocket over the central lens portion. These pockets tend to collect optical contaminants such as toner particles and paper fibers increasing the difficulty of the periodic cleaning required for all erase lamps.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, there is provided a light collector adapted to be interposed between a light source and a target surface. The light collector includes a cylinder lens having an upper surface and a lower surface with a tongue extending therefrom. The cylinder lens is supported by a pair of reflecting members that reflect light beams from the light source and direct the reflected light beams to the lower surface of the cylindrical lens. A number of cross-ribs extend between the reflecting members to specularly reflect light beams from said light source.
According to a second aspect of the present invention, there is provided an apparatus for irradiating a target surface, comprising a plurality of light sources arranged in linear array, first and second reflecting members adapted to reflect light beams from the light sources and direct the reflected light beams in a uniform direction, and a cylinder lens supported by the reflecting members. The cylinder lens includes an upper surface and a lower surface with a tongue extending therefrom. The cylinder lens is adapted to receive the reflected light beams at the lower surface and direct the light beams to a preselected area on the target surface. A number of cross-ribs extend between the reflecting members to specularly reflect light beams from said light source.
One advantage of the present invention is the provision of a light collector adapted to be interposed between a light source and a target surface, which light collector includes a plurality of cross-ribs that fix the position of first and second reflecting members relative to each other to maintain the light collector profile along the length of the collector without affecting the optical collecting properties of the collector.
Another advantage of the present invention is the provision of a light collector adapted to be interposed between a light source and a target surface, which light collector includes a plurality of cross-ribs that mechanically stabilize two reflecting members to facilitate the coating and/or assembly of the light collector to a substrate during manufacture.
Further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.
REFERENCES:
patent: 1977689 (1934-10-01), Muller
patent: 2224178 (1940-12-01), Bitner
patent: 2254961 (1941-09-01), Harris et al.
patent: 2254962 (1941-09-01), Harris et al.
patent: 4767172 (1988-08-01), Nichols et al.
patent: 5526190 (1996-06-01), Hubble
patent: 5757557 (1998-05-01), Medvedev et al.
patent: 5973853 (1999-10-01), Gaebe et al.
patent: 6115184 (2000-09-01), Hubble, III et al.
Aurand Steven L.
Floridio G. Peter
Hubble, III Fred F.
Scheuer Mark A.
Soures Nicholas M.
Allen Stephone B.
Fay Sharpe Fagan Minnich & McKee LLP
Xerox Corporation
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