GB2208942A - Retractable registration member having diffusely reflective underside in document illumination apparatus - Google Patents

Abstract

A document illumination apparatus includes a transparent platen 10 for supporting a document 11, illumination means for illuminating the document through the platen, and a retractable registration member 32 adjacent an edge of the platen. The upper portion of the registration member provides a registration gate 31 for documents on the platen. The registration member includes a lower portion provided with a lip 37 which extends beneath the platen edge, and the underside 35 of the lower portion is diffusely reflective. The surface 36 of the registration member adjacent said platen edge may be diffusely reflective. <IMAGE>

Description

REGISTRATION EDGE This invention relates a to a document illumination apparatus including a transparent platen tor supporting a document, illumination means for illuminating the document through the platen, and a retractable registration member adjacent an edge of the platen, the upper portion of the registration member providing a registration gate for documents on the platen.

Such an apparatus is particularly, although not exclusively, useful in a copying machine such as a xerographic copying machine where documents to be copied are placed successively on a platen, either manually or automatically by a document feeder.

In copying machines generally, and particularly xerographic copying machines, copying the edges of a document without showing a black border is a persistent problem.

One way of over coming this problem is the use of a deletion technique which deletes information from a band around the copy of the document, the deletion band be!ng broad enough to overlap the edge of the document. A disadvantage of this technique Is the loss of any information in the narrow band just Inside the edge of the document. An alternative technique is to magnify the document slightly so that the edges of the image of the document fall outside the area of the copy. This technique also suffers from the disadvantage that information is lost from a small area around the edge of the copy, as well as the disadvantage that the dimensions of the information contained on the copy are larger than those on the original, which may not always be desirable.

In copying machines of the kind using scanning illuminators, the scanning lamps are usually arranged to illuminate the platen from two directions, i.e. leading and trailing the scan. At the lead edge of the document, the illumination is reduced because of the shadow produced by the edge of the platen glass and by the registration member.

In some copying machines, such as the Xerox (trademark) 1045 machine, the platen glass is about six millimetres thick, and some replacement of document edge illumination occurs by total internal reflection at the edge of the glass. In order to hide the black gap between the glass and the registration member, a thin, flexible, white plastic strip is secured to the underside of the registration member, and projects beneath the edge of the platen glass to produce a narrow edge deletion effect. An arrangement of this kind has the disadvantages that the white plastic strip must be secured to the registration member, involving the use, for example, of adhesives as well as means to accurately locate the plastic strip to avoid either a black edge occurring, or an undue amount of deletion around the lead edge of the document.Furthermore, the plastic strip. and any adhesive used, must be able to withstand mechanical abuse and the high temperature produced by the illuminator.

It is an object of the present Invention to provide a document illumination apparatus in which these disadvantages are overcome, and in which an inexpensive means is provided for obtaining an accurate but minimal amount of leading edge deletion.

Accordingly, the invention provides a document illumination apparatus of the kind specified which Is characterised in that the registration member includes a lower portion which extends beneath the platen edge, and that the underside of the lower portion is diffusely reflective.

In addition, the surface of the registration member adjacent the platen is preferably diffusely reflective.

The apparatus of the invention provides a robust and inexpensive way of deleting the required narrow edge portion at the leading edge of the document, and in its preferred form also enables the use of thinner platen glasses, where total internal reflection provides less edge replacement of illumination than is the case with thicker platens.

A document illumination apparatus in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 Is a diagrammat!c cross sectionai view of the imaging system of a xerographic copying machine incorporating the invention; and Figure 2 Is a cross sectional view of the registration member of a document illumination apparatus in accordance with the invention.

Referring to Figure 1 a platen 10 supports a document 11 so that an image of the document may be projected onto the surface of a photoreceptor 12. The platen 10 is made of transparent glass and is illuminated from below by means of a lamp 13 mounted in a reflector 14. Lamp 13 and reflector 14 are carried on a full rate scanning carriage 15, which is mounted for movement to left and right as shown in the drawing, directly below and parallel with the platen 10. Also mounted on full rate carriage 15 is a full rate mirror 16 which is arranged to receive light reflected generally vertically downwards from the document 11 on the platen.

Mirror 16 is set at 45" to the plane of the platen, so that it reflects the light generally parallel with the platen towards the half rate mirrors 17 and 18 which are mounted on a half rate carriage 19. Mirrors 17 and 18 are arranged to reflect the light back in the opposite direction and through a lens 20. Lens 20 focuses the light, via three further mirrors as will be described, onto the photoreceptor 12. The first two mirrors beyond the lens 20, i.e. mirror pair 21 and 22, are arranged to again reverse the direction of the light beam, and are mounted on a reductionlenlargement carriage 23. A fixed mirror 24 is arranged to reflect the light generally vertically onto the lower run of photoreceptor 12, which is in the form of an endless belt arranged for circulation about support rollers.

In order to produce an electrostatic latent image of the document on the photoreceptor 12, the document is scanned by moving the full rate carriage 15 at a first speed and in a first direction , and by simultaneously moving the half rate carriage 19 in the same direction at half the speed. This maintains a constant optical path length, while scanning the document a strip at a time. The photoreceptor 12 is driven in synchronism with the scanning movement so that the image is directed a strip at a time onto the photoreceptor. The photoreceptdr, which has previously been electrostatically charged, is then discharged in image configuration by the image of the document. The image is then developed with a toner material, and the developed image is transferred to a copy sheet and fixed on it as is well known in the art.

In order to change the magnification of the image compared with the document, the lens may be moved along the optical path and appropriate adjustments to the conjugate length made by moving the reduction/enlargement carriage 23 appropriately. The lens and the carriages are preferably driven to appropriate positions by stepper motors, controlled by a suitable software program.

Referring now also to Figure 2, the leading edge 30 of the document 11 is registered against a registration edge 31 that is provided on a registration member 32. The registration member 32 is formed integrally with a sheet guide 33 that is pivotally mounted parallel with the leading edge 30 by means of pivot 34. When the sheet guide is pivoted anti-clockwise, as shown in solid Iines in Figure 2, the registration edge 31 projects above the top surface of platen 10 so that a document 11 may be registered against it. When it is desired to feed the document across the platen, for example when using a automatic document handler, the registration member is retracted to the dotted line position shown in Figure 2.The registration edge 31 is then below the top of the platen 10, so that a document may be fed off the edge the platen and onto the sheet guide for further handling by the automatic document handler.

The lower portion of the registration member 32 has a lip 34 extending beneath the lower edge of the platen 10. The underside 35 of the registration member 32 is coated with a diffusely reflective material, for example diffusely reflective white paint. The end face 36 of registration member of 32 adjacent the platen edge is similarly coated. The bottom surface 35 reflects into the optical path light from the reflector 14, and fills the space between the paper registration edge and the document as seen through the platen glass. The lip 34 preferably overlaps the platen by about 0.6 millimetres.

The reflective end face 36 of the registration member fills in the area of the platen which would otherwise be shadowed by the illuminator, thus preventing any shadows along the leading edge

Claims (4)

1. CLAIMS 1. Document illumination apparatus including a transparent platen for supporting a document, illumination means for illuminating the document through the platen, and a retractable registration member adjacent an edge of the platen, the upper portion of the~ registration member providing a registration gate for documents on the platen, characterised in that the registration member Includes a lower portion which extends beneath said platen edge, and that the underside of the lower portion is diffusely reflective.
2. 2. The apparatus of claim 1 wherein the surface of the registration member adjacent said platen edge is diffusely reflective.
3. 3. The apparatus of claim 1 or claim 2 wherein the registration member is provided on an edge of a sheet guide member for guiding documents fed across the platen.
4. 4. The apparatus of claim 3 wherein the sheet guide member is pivotally mounted about an axis parallel with said platen edge to enable retraction of the registration plate below the upper surface of the platen when a document is to be fed across the platen.