GB2288703A

GB2288703A - Light shield for a luminous screen scanner

Info

Publication number: GB2288703A
Application number: GB9507893A
Authority: GB
Inventors: Rene Lazecki
Original assignee: Werner Tabarelli
Current assignee: Werner Tabarelli
Priority date: 1994-04-18
Filing date: 1995-04-18
Publication date: 1995-10-25
Also published as: AT193U1; GB9507893D0; DE19514060A1

Description

2288703 IMAGE CONVERSION DEVICE The invention relates to a device for

converting an image displayed on a luminous surface, particularly for example a screen of a microfilm- or microfiche reading apparatus into electrical signals. wherein a bar provided with image sensors is guided over the luminous surface.

With microfilm- and microfiche reading apparatus, it is often desirable to be able to print out the image displayed on the screen or to be able to process it further in other data processing apparatus. Thus, large microfilm reading apparatus is already in existence, which, behind the screen, in the apparatus itself, incorporates an optoelectronic reading apparatus with CCD-elements, for the purpose of converting optical image data into electrical signals which can then be further processed or printed out. With such microfilm reading apparatus, a tiltable mirror can be used to direct the display optionally on the screen for the user or optionally onto the optoelectronic reading apparatus. Apart from the large amount of space which such large microfilm reading apparatus requires, a further drawback is, above all, its high cost.

Also, the image is not visible on the screen during optoelectronic reading.

Furthermore, hand-held scanners are known for the electronic reading of sectors of a screen of a microfilm reading apparatus. These hand-held scanners have a small optoelectronic image sensor which is moved and only permits the reading in of a small sector of an image, usually a word or a line, but not a complete page.

Attempts made by the Applicant have shown that secondary light sources in the room cause disturbing reflections on the luminous. preferably matt surface (screen) and that therefore the quality of the scanned image is impaired. Particularly unfavourable is the fact that most light sources in the room are powered by an alternating current. e.g.

Hz or 60 Hz. As a result, the incidence of light on the luminous surface varies temporally, giving rise therefore to disturbing reflections which vary temporally. On the basis of this recognition, the invention now proposes that in order to obtain troublefree scanning 1 of a screen, or the like, in the presence of secondary light sources, a shielding be arranged on the bar between the image sensors and the luminous surface, which shielding prevents the incidence of secondary light from light sources other than the luminous surface, onto the 5 image sensors.

According to the present invention there is provided a device for converting an image displayed on a luminous surface, such as a screen of a microfilm reading apparatus or a microfiche reading apparatus, into electrical signals. wherein a bar provided with image sensors is guided over the luminous surface. characterised in that arranged on the bar between the image sensors and the luminous surface is a shielding which prevents incidence of secondary light, from light sources other than the luminous surface. onto the image sensors.

In embodiments of the invention. the shielding is moved together with the bar so as to prevent the incidence of secondary light on the screen from causing disturbing effects on the image sensors. By virtue of this relatively simple measure, a significant improvement is possible in the image quality of the scanned image.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which:

Figure 1 shows a schematic front view of a microfilm reading apparatus to which a device embodying the invention is secured for conversion of the image displayed on the screen; Figure 2 shows a schematic perspective view of an embodiment of the device according to the invention; Figure 3 is a cross-section through a bar embodying the invention; and Figure 4 shows an embodiment of a bar in the direction X of Figure 3 (as if viewed from the luminous surface) ("bottom view").

2 1 The microfilm reading apparatus 1 shown in Figure 1 is of the conventional design and has, for example, operating elements 2 and a screen (matt screen) 3. on which an image (graphics or text) is displayed. Particularly with smaller microfilm- or microfiche reading apparatus. it used to be necessary for the person looking at the image to write down important information by hand. Some devices were already able to print out the image. but otherwise these were further processed in electronic data processing apparatus. By way of the device embodying the invention, such apparatus can be added to. and it is possible to convert the image displayed on the screen into electrical signals which can then be further processed in any data processing apparatus. and, also printed out.

With the embodiment shown, the device embodying the invention comprises a bar 4 with a plurality of juxtaposed image sensors 5 which are distributed substantially over the entire longitudinal extent of the bar (cf. also Figure 3). The bar 4 is guided by a guide element (vertical guide rod 6), wherein a slide which is fixedly connected to the bar 4 slides along the guide 6. The image sensors 5 may. for example. be in the form of a line of a plurality of juxtaposed CCDimage sensors. as known in facsimile technology. and may be arranged on a ceramic substrate 5a.

The guide element 6 for the bar 4 is fixed by fastening means firmly relative to the screen which is in the form of a luminous surface 3.

These fastening means may be in the form of screws 8, for example, which are capable of firmly securing the guide rod 6 to the microfilm reading apparatus and thus firmly to the screen 3. If. as shown in Figures 1 and 2, a surrounding frame 9 is provided, then the guide rod 6 can also be fixed to the screen 3 by way of this frame 9, wherein the frame 9, as indicated in Figure 2, has fixing means 8' (e.g. screws, clamps, adherents, or the like) and the guide rod 6 is simply firmly connected to the frame 9. A frame 9 of this kind can also carry the drive motor 10 for the bar. With the embodiments shown in Figures 1 and 2, a pinion 11 of the motor drives a toothed belt 12 which is guided at the top around a direction- changing roller 13 and is connected to the slide 7. A toothed belt drive of this kind permits 3 1 fast. accurate and uniform movement of the beam over the entire surface of the screen. Clearly. different drives are quite conceivable and possible, e.g. toothed racks or ball screw drives. In addition, the frame 9 can perform a protective function by covering over the moving parts of the device embodying the invention and by carrying a covering pane 14 (Figure 2) at the front. A key pad 15. or other switching elements for operating elements of the device embodying the invention, can be arranged on the covering pane 14. A control device 16 for the drive motor 10 and/or a device for evaluating the electrical image signals can be provided inside the frame 9. The control device and the evaluation device can. of course. also be arranged in a suitable place outside the frame.

In order to map the image displayed on the screen onto the image sensors 5 juxtaposed in line form, a plurality of juxtaposed lenses can be provided upstream. Graded index lenses are particularly favourable (cf. Figure 3) which produce an upright image on a scale of 1:1.

Despite the fact that there are fewer lenses than image sensors 5. the lenses make it possible for a uniform image to be produced by way of the image sensors 5. The lenses 17 can. as known per se, be collected together to form a strip of lenses.

During operation, the bar 4 is movable perpendicularly to its longitudinal direction. by means of the electric drive 10 (two- directional arrow 18 in Figure 3). In order to have a properly defined spacing from the screen, despite the one-sided guidance of the bar 4, shown in Figures 1 and 2. a roller 24 is fixed to a spacer 23, which roller rolls down the screen 3 (luminous surface) or a separate rail, not shown.

Nowadays, most microfilm reading apparatus has matt screens of plastic material. For the image of the matt screen to be scanned, with the relatively small distance away from the camera. the depth of focus for imaging on the CCD-lines is less than one tenth of a millimetre.

However. plastic panes usually have a curvature of up to 1 - 2 mm. Therefore, together with the device embodying the invention, a glass pane is preferably supplied which can be very flat in design. A 4 plastics shatter protective film is stuck onto the rear side of the glass pane to prevent damage to the microfilm reading apparatus in the event of the pane being broken.

The device embodying the invention can. of course. also be fixed to the screen, having been rotated into different positions. e.g. through 90', wherein the bar then moves from left to right rather than from top to bottom.

With the embodiment shown in Figure 3. the image information received by the image sensors 5 with the method employing the bar 4 is converted into digitally coded grey scale signals in the housing 4a by an electronic switching device 19 arranged in the bar 4, and these grey scale signals are transmitted in parallel-bit manner by way of a grouping of junction lines, preferably a flat band cable (not shown in Figure 1 for the sake of clarity) to a stationary processing device. This digitizing can also take place in an evaluation switching device downstream of the flat strip cable. By way of example, 8 bits permit the transmission of 256 grey scales. In the simplest case, the data can be sent to a personal computer or a printer direct without any intermediate memory.

With the embodiment shown in Figure 3 a shielding 20 is now arranged. on the bar 4 between the image sensors 5 and the luminous surface 3, and this shielding prevents the incidence of secondary light. from sources of light other than the luminous surface itself. onto the image sensors 5. In order to obtain good shielding of incident secondary light. it is advantageous if the shielding 20 is arranged at a spacing of less than 1 mm from the luminous surf ace 3. Basically, it would also be conceivable, particularly with disturbing incidence of secondary light, for an elastic member or brush-like member to slide directly on the surface of the luminous surface 3, at the bottom of the shielding 20.

The shielding is black and/or matt on the inside, in order to absorb incident light and/or scatter it.

In terms of design, a shielding of this kind is most advantageous if it in the fgrm 9P walls Pixed to th6 hAP W 9UPP6Ufldifi& A goge@ disposed between the luminous surface 3 and the image sensors 5, preferably four flat walls are provided. which walls are disposed perpendicularly to each other and perpendicularly to the luminous surface 3. Figure 4 shows a view of the bar embodying the invention. as viewed from the luminous surface, of the underside of the four walls 21 of the shielding 20. Figure 4 also shows the strip of the graded index lenses 17. The graded index lenses are combined to form a strip 10 which are connected directly or by way of spacers 22 to the shielding. It is therefore possible for the shielding to carry the graded index lenses 17 and therefore to hold them at a defined spacing from the image sensors 5.

6

Claims

1.

A device for converting an image displayed on a luminous surf ace, such as a screen of a microfilm reading apparatus or a microfiche reading apparatus, into electrical signals, wherein a bar provided with image sensors is guided over the luminous surface, characterised in that arranged on the bar (4) between the image sensors (5) and the luminous surf ace (3) is a shielding (20) which prevents incidence of secondary light, from light sources other than the luminous surface (3), onto the image sensors (5).

2. A device according to Claim 1, characterised in that the shielding (20) is brought to within less than 1 mm from the luminous surface.

3. A device according to Claim 1 or Claim 2. characterised in that the inside of the shielding (20) is black.

4.

5.

A device according to one of Claims 1 to 3. characterised in that the shielding (20) has walls which are fixed to or formed on the bar (4) and which enclose a space disposed between the luminous surface (3) and the image sensors (5).

A device according to Claim 4, characterised in that four walls (21) of the shielding (20) are flat and are disposed perpendicularly to one another, and preferably are disposed so that they are perpendicular to the luminous surface (3).

6. A device according to one of Claims 1 to 5, characterised in that arranged between the image sensors (5) and the luminous surface (3) is at least one, preferably a series, of lenses (17).

A device according to Claim 6. characterised in that the lenses (17) are cylindrical graded index lenses which produce an upright image on a scale of 1: 1.

7

8. A device accordinf to Claim 6 or Claim 7, characterised in that the shielding (20) is connected to the lenses (17) or lens holders (22).

9.

A device for converting an image displayed on a luminous surface, the device being substantially as hereinbefore described with reference to the accompanying drawings.

8