Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
1998-09-11
2003-06-10
Pham, Hai (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S256000
Reexamination Certificate
active
06577332
ABSTRACT:
BACKGROUND
1. Field
The apparatus and method described in this patent specification relate to an optical apparatus, in particular, an optical apparatus using a light source in the form of a micro-light source array such as an LED (light emission diode) array or an EL (electroluminescence) array, etc., employed in the optical writing-in unit of a scanner, etc., or in an electrophotographic printer, a digital copying machine, a facsimile device, etc.
2. Background Technology
In recent years, there has been an increase in the use at home or in small businesses of office equipment that previously was found mainly in larger firms. As a result, there has been an increase in the demand for compact and low-cost office equipment such as electrophotographic printers, etc., that still provide high resolution and high print or copy quality.
One example of such apparatus is an LED printer, which is an electrophotographic printer employing an LED (light emitting diode) array comprising a large number of LEDs. Because a printer of such type uses a fixed writing light source incorporating the LED array, the apparatus itself can be more compact than a comparable raster scanning printer employing a semiconductor laser (laser diode) and a mirror scanning system. In addition, the LEDs in an LED printer can write in parallel (simultaneously) and thereby make it simpler to increase writing speed.
When the light source is an LED array, the light from the individual LEDs needs to be delivered onto the light-receiving surface (e.g., photosensitive or photoconductive surface) at high resolution and high efficiency. Furthermore, in order to make the apparatus more compact, the distance between the light source (LED array) and the light-receiving surface needs to be minimized. For this reason, a suitable focusing optical system is required. A rod lens array composed of bundled plural rod lenses has been used for such focusing in many LED printers.
FIG. 5
illustrates a structure discussed in the published specification of Japanese Laid-open Patent Publication No. 7-108709/1995, and is an example of an optical apparatus employing such a rod lens array in which light rays emitted from each of LEDs
102
in an LED array
101
(comprising a number of LEDs
102
arranged in a row extending in a direction perpendicular to the drawing sheet) are projected onto a photosensitive surface
105
by the focusing action of a corresponding rod lens
104
in the rod lens array
103
(which also comprises a number of lenses
104
arranged in a row extending in a direction perpendicular to the drawing sheet). As a result, a fine spot image is focused on the photosensitive surface
105
. The rod lens array
103
forms the focusing optical system
106
.
FIG. 22
is a similar cross-sectional view of the proposal discussed in the same Patent Publication, and shows that the light rays emitted from an LED
302
in an LED array
300
are projected onto a photosensitive surface
306
by the focusing action of a corresponding rod lens
304
in a rod lens array
103
to thereby produce a finely focused light spot at photosensitive material
306
.
Another use of an LED array in an optical apparatus is illustrated in
FIGS. 6 and 23
, and is discussed in the published specification of Japanese Laid-open Patent Publication 8-1998/1996. In
FIG. 6
, light rays emitted from an LED
112
in an LED array chip (LED array)
111
are guided to a photosensitive surface facing or contacting an optically opaque block
114
through a corresponding light guiding path
113
in block
114
, which is mounted on the LED array chip
111
. In
FIG. 23
, light rays emitted from an LED
312
in an LED array
310
are guided to a photosensitive surface facing or contacting an optically opaque layer
314
through a corresponding guiding path
316
in the form of a light pipe formed in layer
314
.
The rod lenses of a rod lens array system of the type illustrated in
FIGS. 5 and 22
, transmit light relatively efficiently to the photosensitive surface
105
. However, because the light emission angle of an LED
102
in the LED array
101
is inherently wide and includes much more than the facing area of the corresponding rod lens
104
, much of the light energy emitted from an LED does not reach its rod lens
104
. As a result, there is poor utilization efficiency of the light energy that an LED emits. Consequently, if a predetermined amount of light energy or intensity is required at the photosensitive surface
105
, it is necessary to emit much more energy or intensity from the LED, with a corresponding need for high drive electric current to the LED
102
and a corresponding undesirable heating of the LED
102
.
The LED arrays of the type shown in
FIGS. 6 and 23
also have a relatively poor light energy utilization and, in addition, fail to provide a light focusing function and, therefore, unless the photosensitive surface is brought very close to or in contact with the optical system (the layer
114
), the light image formed on the photosensitive surface is out of focus, resulting in poor resolution.
SUMMARY OF THE DISCLOSURE
The system and method disclosed in this patent specification are designed to overcome these and other deficiencies in known approaches and to provide improvements in delivering light energy to a light receiving surface efficiently and effectively.
To this end, the disclosed system and method use a light source such as an LED or an EL array in an arrangement that increases the light energy utilization as compared with known systems and methods, while retaining significant benefits of such known systems and methods. One aspect of the disclosed approach is to use technology similar to that used in the integrated circuit (IC) technology to form an LED at the bottom of a recess whose walls serve to direct much more of the light energy from the LED to an element such as a rod lens that guides or some other focusing or light guiding system that in turn delivers the light energy to a light receiving surface.
REFERENCES:
patent: 3991339 (1976-11-01), Lockwood et al.
patent: 4698730 (1987-10-01), Sakai et al.
patent: 4980700 (1990-12-01), Ng
patent: 4980893 (1990-12-01), Thornton et al.
patent: 5055892 (1991-10-01), Gardner et al.
patent: 5119174 (1992-06-01), Chen
patent: 6034712 (2000-03-01), Iwasaki
patent: 7108709 (1995-04-01), None
patent: 8-1998 (1996-01-01), None
Osawa Yasuhiro
Saitoh Tetsuro
Cooper & Dunham LLP
Pham Hai
Ricoh & Company, Ltd.
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