GB1586112A - Scanning apparatus - Google Patents

Description

(54) SCANNING APPARATUS (71) We XEROX CORPORATION of Xerox Square, Rochester, New York, United States of America, a corporation organised under the laws of the State of New York, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a full- and halfrate reflector scanning apparatus, particularly, although not exclusively, for use in an electronic data transmission apparatus.

Scanning systems using full- and halfrate mirrors are well known in, for example, xerographic copying machines. In a typical system of this kind a first mirror, the full rate mirror, is mounted on a carriage that is arranged to carry the first mirror at a uniform speed along a path below and parallel with a transparent platen.

The platen also carries a document to be copied. Also mounted on the carriage is a light source. The plates (and any document placed on it) is illuminattd by the light source, and light reflected from the document is further reflected by the first mirror to a second mirror, which is the halfrrate mirror. The half-rate mirror is arranged to move, in synchronism with the full-rate mirror, in a parallel direction but at half the speed. It is arranged that the light patli from the full-rate mirror to the half-rate mirror is inclined to the plane of the platen so that the returning light rays avoid the full-rate mirror. A lens is usually placed in the path of light reflected from the half-rate mirror, and further reflectors may be used to prdvide an image which is of the same sense as the document being copied, or of the opposite sense, as appropriate. As the full-rate mirror and the light source move across the platen, a line-byline image of the document on the platen is formed in the focal plane of the lens.

Systems of the kind just described are found to work well, and could be readily adapted for use in the electronic transmission of data by placing photosensitive detectors, such as an array of charge coupled devices (CCDs), in the focal plane of the lens. However, these known systems suffer from the disadvantage that they occupy a relatively large volume because of the configuration of the optical path through the system and because of the large mirrors which have to be used to allow for shift in the light path which occurs at the half-rate mirror as the scan progresses.

It is an object of the present invention to at least partially overcome this disadvantage by providing a relatively compact full- and half-r,ate reflector scanning apparatus.

According to the present invention there is provided a full- and half-rate reflector scanning apparatus in which a light source is contained in a reflective housing and is arranged for movement with the full-rate reflector to scan an object plane, the fullrate reflector being mounted so as to receive light reflected from the object plane through an aperture in said housing and so as to reflect said light along a path substantially parallel with said object plane, and the half rate reflector comprising a roof type reflector arranged to return the light substantially parallel with the object plane, and between the object plane and said path, through further apertures in said housing to an imaging position.

A full- and half-rate reflector scanning apparatus will now be described, by way of example with reference to the accompanying drawings, in which: - Figure 1 is a diagrammatic cross-section of one embodiment of the apparatus of the invention; and Figure 2 is a diagrammatic cross-section of another embodiment.

Referring to Figure 1, the full- and halfrate reflector scanning apparatus includes a light source 1, a platen 2, a full-rate reflector 3, and a half-rate reflector 4. The light source 1 is typically a linear filament lamp of small diameber, preferably less than 5mm. The light source 1 is mounted in a housing which includes an elliptical re flector 5. The reflector 5, which is of elongate form with a part elliptical cross-section, is mounted on a carriage (not shown) so that the mouth of the reflector is just below the lower surface of the platen 2. The carriage is arranged for linear motion across the apparatus from right to left as shown.

This causes any document placed on the platen to be illuminated in a scanning or line-by-line fashion. The full rate reflector 3 is mounted on the same carriage as the reflector 5 and is arranged to receive light reflected from the platen 2 through a slitlike aperture 6 in the wall of the reflector 5. The full-rate reflector 3 is inclined at an angle such that it reflects light along path 7 substantially parallel with the platen 2.

The half-rate reflector 4 is a roof element, which may be a roof mirror or a roof prism, and is mounted on a second carriage, not shown, which is arranged to be driven in synchronism with the carriage of the full-rate reflector, and in the same direction, but at half the speed. By the use of a roof element, the light is reflected back substantially parallel with the platen 2, and between the light path 7 and the platen 2.

Light returning from the half-rate reflector 4 travels along path 8 and passes through two further slit-like apertures 9 and 10 in the reflector 5 after which it is focussed by a lens 11 onto a photosensitive member 12 which may be a linear array of charge coupled devices. The apertures 9 and 10 are, of course, of sufficient width to let the light cone pass through the reflector and to be focussed by the lens.

The reflectors used in the apparatus of the invention may be of small size compared with those used in previous full- and half-rate scanning systems, since, due to the substantially parallel optical paths, no allowance needs to be made for shift in the light path as the scan progresses. The use of a roof element as the half-rate reflector has the added advantage that even if it is rotated, it always returns the light along the required path. This makes for ease of assembly, and makes the apparatus less susceptible to the effects of vibration in use. These features and advantages to gether make it possible to construct a scanning apparatus, for use with documents of standard sizes, with a height of less than 5cm. This in turn allows the apparatus to be used in a platen cover for the face-up copying of documents, as will now be described with reference to Figure 2.

Referring to Figure 2, the apparatus shown is an inverted version of that shown in Figure 1, mounted in a housing 20 which is hinged by a hinge 21 to a suitable point on à machine casing next to a platen 22.

Whereas in Figure 1 the platen 2 is a transparent platen, with documents placed facedown on top of it, in the Figure 2 embodiment, the platen 22 may be opaque, the document being placed on it in a face-up position. The lower surface 23 of the housing 20 is a transparent plate, such as a glass plate, through which the scanning apparatus of the invention can operate. In the Figure 2 arrangement, the lens 11 and photosensitive element 12 may be placed within the machine housing, as shown, in which case an additional reflector 24 is needed in the housing 20. Alternatively, as indicated at 25 and 26, the lens and photosensitive member may be provided within the housing 20, the output of the photosensitive member 26 being provided by electrical means, (not shown). Apart from the items just discussed, the remaining items in the Figure 2 embodiment are the same as those described with reference to Figure 1, and corresponding reference numerals are used.

The Figure 2 embodiment has the added advantage, common to any face-up copying system, that it is easy to align the document to be copied on the platen, and that montages are very easy to prepare.

WHAT WE CLAIM IS: - 1. A full- and half-rate reflector scanmng apparatus in which a light source is contained in a reflective housing and is arranged for movement with the full-rate reflector to scan an object plane, the full-rate reflector being mounted so as to receive light reflected from the object plane through an aperture in said housing and so as to reflect said light along a path substantially parallel with said object plane, and the half rate reflector comprising a roof type reflector arranged to return the light substantially parallel with the object plane, and between the object plane and said path, through further apertures in said housing to an imaging position.

2. The apparatus of Claim 1 wherein the reflective housing is of elongate form with a part elliptical cross-section.

3. The apparatus of Claim 1 or Claim 2 including at said imaging position a lens and a photosensitive element.

4. The apparatus of Claim 3 wherein said photosensitive element is a linear array of charge coupled devices.

5. The apparatus of any one of Claims 1 to 4 including a transparent platen for supporting an object to be scanned in the object plane.

6. The apparatus of any one of Claims 1 to 4, contained within a housing adapted to

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. flector 5. The reflector 5, which is of elongate form with a part elliptical cross-section, is mounted on a carriage (not shown) so that the mouth of the reflector is just below the lower surface of the platen 2. The carriage is arranged for linear motion across the apparatus from right to left as shown. This causes any document placed on the platen to be illuminated in a scanning or line-by-line fashion. The full rate reflector 3 is mounted on the same carriage as the reflector 5 and is arranged to receive light reflected from the platen 2 through a slitlike aperture 6 in the wall of the reflector 5. The full-rate reflector 3 is inclined at an angle such that it reflects light along path 7 substantially parallel with the platen 2. The half-rate reflector 4 is a roof element, which may be a roof mirror or a roof prism, and is mounted on a second carriage, not shown, which is arranged to be driven in synchronism with the carriage of the full-rate reflector, and in the same direction, but at half the speed. By the use of a roof element, the light is reflected back substantially parallel with the platen 2, and between the light path 7 and the platen 2. Light returning from the half-rate reflector 4 travels along path 8 and passes through two further slit-like apertures 9 and 10 in the reflector 5 after which it is focussed by a lens 11 onto a photosensitive member 12 which may be a linear array of charge coupled devices. The apertures 9 and 10 are, of course, of sufficient width to let the light cone pass through the reflector and to be focussed by the lens. The reflectors used in the apparatus of the invention may be of small size compared with those used in previous full- and half-rate scanning systems, since, due to the substantially parallel optical paths, no allowance needs to be made for shift in the light path as the scan progresses. The use of a roof element as the half-rate reflector has the added advantage that even if it is rotated, it always returns the light along the required path. This makes for ease of assembly, and makes the apparatus less susceptible to the effects of vibration in use. These features and advantages to gether make it possible to construct a scanning apparatus, for use with documents of standard sizes, with a height of less than 5cm. This in turn allows the apparatus to be used in a platen cover for the face-up copying of documents, as will now be described with reference to Figure 2. Referring to Figure 2, the apparatus shown is an inverted version of that shown in Figure 1, mounted in a housing 20 which is hinged by a hinge 21 to a suitable point on à machine casing next to a platen 22. Whereas in Figure 1 the platen 2 is a transparent platen, with documents placed facedown on top of it, in the Figure 2 embodiment, the platen 22 may be opaque, the document being placed on it in a face-up position. The lower surface 23 of the housing 20 is a transparent plate, such as a glass plate, through which the scanning apparatus of the invention can operate. In the Figure 2 arrangement, the lens 11 and photosensitive element 12 may be placed within the machine housing, as shown, in which case an additional reflector 24 is needed in the housing 20. Alternatively, as indicated at 25 and 26, the lens and photosensitive member may be provided within the housing 20, the output of the photosensitive member 26 being provided by electrical means, (not shown). Apart from the items just discussed, the remaining items in the Figure 2 embodiment are the same as those described with reference to Figure 1, and corresponding reference numerals are used. The Figure 2 embodiment has the added advantage, common to any face-up copying system, that it is easy to align the document to be copied on the platen, and that montages are very easy to prepare. WHAT WE CLAIM IS: -

1. A full- and half-rate reflector scanmng apparatus in which a light source is contained in a reflective housing and is arranged for movement with the full-rate reflector to scan an object plane, the full-rate reflector being mounted so as to receive light reflected from the object plane through an aperture in said housing and so as to reflect said light along a path substantially parallel with said object plane, and the half rate reflector comprising a roof type reflector arranged to return the light substantially parallel with the object plane, and between the object plane and said path, through further apertures in said housing to an imaging position.

2. The apparatus of Claim 1 wherein the reflective housing is of elongate form with a part elliptical cross-section.

3. The apparatus of Claim 1 or Claim 2 including at said imaging position a lens and a photosensitive element.

4. The apparatus of Claim 3 wherein said photosensitive element is a linear array of charge coupled devices.

5. The apparatus of any one of Claims 1 to 4 including a transparent platen for supporting an object to be scanned in the object plane.

6. The apparatus of any one of Claims 1 to 4, contained within a housing adapted to

be placed over a document lying in a face-up position, the apparatus being arranged for scanning such a document.

7. A full- and half-rate scanning apparatus substantially as hereinbefore described with reference to either of Figures 1 or 2 of the accompanying drawing.