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Document Scanning and Illumination Mechanism

IP.com Disclosure Number: IPCOM000075775D
Original Publication Date: 1971-Nov-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 52K

Publishing Venue

IBM

Related People

Bruce, GD: AUTHOR [+6]

Abstract

Figs. 1 and 2 illustrate an optical scanning system for copying machines. Illumination, as well as the scanning, of the document and reduction mode copying are provided for.

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Document Scanning and Illumination Mechanism

Figs. 1 and 2 illustrate an optical scanning system for copying machines. Illumination, as well as the scanning, of the document and reduction mode copying are provided for.

Fig. 1 is a left view of the scanning and illumination mechanism, as it would appear with left cover 1 and left end reflectors 2 and 3 (shown in Fig. 2) removed. Fig. 2 is a front view of this mechanism as it would be seen with front cover 4 removed. A document placed on top of flat glass plate 5 is scanned by the movement of scanning mirror 6 between positions 6a and 6b imaging rotating drum 8 through lens assembly 9, the optical axis of which is vertical, and through aperture 10, which determines the area scanned, by stationary lower mirror 11.

If mirror 6 is extended, as shown by dashed lines 6c, it may be moved horizontally through a smaller distance. The direction of motion of mirror 6, between positions 6a and 6b, during each scanning operation is determined by the direction of rotation of drum 8. The optical path of the centerline of the scanned document area, as determined by the center of aperture 10, lies at an angle 12 from the perpendicular to the surface of drum 8, from the optical axis of lens 9, and from the perpendicular to the document surface. The path taken by the image of this centerline through the lens is called the off-axis scan line and is designated 13.

In order to minimize the energy required for document illumination, it is desirable that the light used for this purpose be focused along the scanned area of the document. This effect is achieved by use of a pair of lamps 14, mounted in associated reflectors 15, the reflective surfaces of which form portions of an ellipse with its major axis line along the off-axis scan line 13 with one focal point at the filaments of lamps 14, and with the other focal point at the point 16, the intersection of the off-axis scan line and an extension of the document surface. The light path distance remains constant, that is, the sum of the length of the line between points 17 and 18, plus the length of the line between points 18 and 19 remains constant for all positions of mirror 6. This property of the system is also used to achieve a constant light path distance between reflectors 15 and the document surface. The angle 12 between the reflections of the major axis of the ellipse partially formed by the surfaces of reflectors 15 and perpendicular from the document surface also remains constant for all positions of mirror 6.

Thus, the focusing properties of the elliptical reflectors can be used to obtain uniform illumination in the scan areas throughout the scanning process.

The same effect may be alternately achieved by locating the lamp and reflector combinations elsewhere. For example, if mirror 6 is suitably extended as shown by line 6c, the lamps...