The patent's inventor is Kyogoku, Hiroaki (Hyogo, JP).
This patent was filed on
From the background information supplied by the inventors, news correspondents obtained the following quote: "Recently, semiconductor laser diodes have come to be widely used in a variety of types of electrical equipment, for example, laser printers, optical disk apparatuses, fiber-optic communication apparatuses, and mobile phones, because of their compact size, low cost, and ease of use.
"However, the current/quantity of light characteristic of the semiconductor laser diode is dependent on temperature. Accordingly, it is necessary to control quantity of light to obtain a predetermined quantity of light reliably. This quantity of light control is called Automatic Power Control (APC). In the APC process, before the semiconductor laser diode is actually driven, the laser diode is driven in advance, the quantity of light from the laser diode is received by a photo diode (PD), and the detection current values of corresponding quantities of light are stored in a storage device. Then, the semiconductor laser diode is controlled using the current values saved in the storage device so as to obtain a desired quantity of light reliably.
"FIG. 1 is a schematic diagram illustrating a related art image forming apparatus 200X. As illustrated in FIG. 1, the image forming apparatus 200X may be a copier, a facsimile machine, a printer, a multifunction printer using electrophotographic process used in a copier, a facsimile machine, a printer, a multifunction printer having at least one of copying, printing, scanning, plotter, and facsimile functions, or the like.
"In FIG. 1, the image forming apparatus 200X includes a semiconductor laser unit (edge emitting laser unit) 1, a polygon mirror 2, a scanning lens 3, a photoreceptor 4, a beam sensor 5, an image control unit 6, and a laser driver 7.
"In an image forming process, a semiconductor laser (laser diode) LD (edge-emitting laser unit) functioning as a lighting source in the semiconductor laser unit 1 emits a laser beam, and the laser beam is scanned (deflected) by the polygon mirror 2 that rotates at a predetermined velocity. Then, the lased beam forms a lighting spot on the photoreceptor 4 (scanned medium) via the scanning lens 3 (f .theta. lens).
"The deflected laser beam scans and exposes in a main scanning direction orthogonal to a sub-scanning direction in which the photoreceptor 4 rotates, and records image signals with respect to each line thereof.
"The beam sensor 5 is disposed at a position at which the laser beam is radiated, that is, a position close to the one end of the photoreceptor 4, to generate a main scanning synchronized signal. The image control unit 6 generates image data Di and automatic power control (APC) timing signal Sapcsh synchronized with the main scanning synchronized signal. The semiconductor laser driver 7 controls power of lighting of laser diode LD based on the APC timing signal Sapcsh, and emits the semiconductor laser LD, synchronized with the image data D.
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