GB1574839A

GB1574839A - Stereoscopic projecting device

Info

Publication number: GB1574839A
Application number: GB435077A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-04-13
Filing date: 1978-04-13
Publication date: 1980-09-10

Description

(54) STEREOSCOPIC PROJECTING DEVICE (71) I, DAVID HODGE BROWN, a British subject of Lindisfarne, Francis Green Lane, Penkridge, Stafford, England, do hereby declare the invention, for which I pray that a patent may be granted to me and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to projection devices of the type including a back projection screen for slides, strip films and the like. In particular the invention relates to projectors for use as optical teaching aids.

There is a need for a teaching machine which can provide a system of programmed learning which a student can use in the absence of a teacher. Such a system should preferably give continuous feed-back to the student, enabling him to correct his own work as he goes along.

There is also a need for a teaching machine which can project stereoscopic pictures, since this greatly facilitates visual learning in fields such as anatomy and mechanical engineering in which the student has to familiarise himself with objects in three dimensions, which cannot always be satisfactorily represented in two dimensions.

A stereoscopic projector wherein two superimposed images, respectively polarize horizontally and vertically, where viewed through polarising glasses was also unsatisfactory since the images in polarised light had insufficient brilliance.

The present invention provides in one aspect apparatus for viewing pairs of stereoscopic pictures comprising a back projecting screen or a pair of such screens arranged side by side, a projector arranged so as to be able to project images of a pair of stereoscopic pictures on to respective adjacent areas of the screen or to project one said image onto each of said pairs of screens and a stereoscope arranged to enable a respective image to be viewed with each eye.

Such devices could be particularly useful in visual learning programmes wherein stereoscopic pairs of slides are used to illustrate a written text.

A particular advantage of this arrangement as regards learning programmes is that stereoscopic pictures can be presented in the plane of a writing surface to be used by a student. Thus, a sheet or roll of transparent material can be laid over one of the projected images to allow a student to mark parts of the image in response to questions in the text. In addition, marked acetate sheets can be provided, the markings on which, when a sheet is laid over an image projected on the screen, indicate parts of the image referred to in the text. In a convention stereoscopic viewer in which the image is deep inside the body of the viewer, a writing surface cannot be provided in the plane of the image.

Thus in another aspect of the invention provides a projector, a back projection screen for images from the projector and means for positioning sheets or strips of transparent material over the back projection screen. A preferred device embodying the invention has a back projection screen, one area of which is provided with guides on opposite sides thereof to enable a strip of transparent material such as polyvinyl acetate to be passed across the screen. The strip may for example be wound onto spools at each end. A student can use this strip for marking various parts of the image projected on the screen in response to questions forming part of a visual learning programme.

Separate correcting sheets or another strip of transparent material already carrying appropriate marking can then be placed over the first one to check the accuracy of the student's responses.

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings wherein: Figure I is a perspective view of a visual teaching device embodying the invention; Figure 2 is a part-sectional view along the line II-II in Figure 1; Figure 3 shows the paths of light projected from the stereoscopic projector of Figure 1; and Figure 4 shows how light is reflected onto the back projection screen of the device.

Referring to Figure 1, a visual teaching device has a casing 1 in which is mounted a stereoscopic slide projector 4. A slide carrier 5 is provided whereby stereoscopic pairs of slides may be inserted into the projector.

At the front of the device is arranged a pair of back projection screens 2 and 3 onto which the projector 4 projects images from the pairs of stereoscopic slides, one slide being projected onto each screen. Levers 25 and 26 are provided for positioning the images respectively horizontally and vertically and a lever 27 is provided for focussing the images.

To enable a student to view the pairs of images projected onto the screens 2 and 3 as a single three-dimensional image, a mirror stereoscope 14, which may be of any suitable commercially available type, is mounted over the screens on an arm 13 which is secured to the housing 1 by a plate 12 to which the arm 13 is securely fixed.

The screens 2 and 3 are spaced slightly apart so that the images projected thereon do not interfere with one another, and one image can be viewed with each eye. The images are however close enough to be viewed together through the mirror stereoscope with the eyes focussed on infinity, and for the screens to be incorporated into a compact machine.

As can be seen in Figure 2, the projector 4 projects the slides downwardly through a reflecting system 18 on to a mirror 19 adjacent the bottom of the housing 1, the images then being reflected back onto the screens 2 and 3.

Above and below the screen 3 are provided spools 6 and 7 which can be rotated by means of handles 10 and 11 to carry a strip of acetate sheet or similar transparent material 15. This sheet passes over the screen 3, by way of guide rollers 8 and 9. Using a felt or fibre tipped pen or other means, a student can mark on the acetate sheet 15, through which an image on the screen 3 is visible, his answers to questions provided in a programmed learning text. He may for example be required to indicate certain articles appearing in the projected scene to identify them or to indicate directions of flow or rotation in pictures of machinery or the like.

The slides and the screen are provided with small marks in their respective corners to ensure that the two images are correctly aligned in relation to one another. The acetate roll passes through guides on either side to align it correctly with the image on screen 3.

Supports 16 and 17 are provided for placing over the screen and the acetate sheet a correcting sheet 22, also of polyvinyl acetate or similar transparent material on which the correct ansers are written or marked for that particular image or question so that, if the student has answered the questions correctly, the marks on the acetate sheet 15 will coincide with those on the sheet 22.

The sheet 22 can then be removed and the strip 15 of acetate sheet can then be wound onto one of the spools 6 and 7 and another pair of slides projected. The strip 15 can be divided into numbered frames, the numbers on the frames corresponding with the numbers on the pairs of slides to be projected and to numbered questions or sets of questions in the learning programme, and to the correcting sheets 22 for ease of correlation of slides, frames and correcting sheets. A tutor can also use these correcting sheets when later checking the students answers to validate part of the learning programme.

Figures 3 and 4 show schematically the paths of light from the projector 4 to the screens 2 and 3. As can be seen in Figure 3, the projector 4 has two lenses 23 and 24 one for each of the projected slides. The reflector system 18 comprises two pairs of mirrors 20 and 21 which are used further to separate the images projected from the lenses 23 and 24 so that they can be projected respectively onto the separate screens 2 and 3. Each projected image is reflected first from a mirror 20 and then from a mirror 21 before passing to a mirror 19 (see Figure, 4) and then to one of the screens 2 and 3. Lens systems may be included in paths of light to adjust the image size as necessary. This mirror system enables the images from pairs of small slides mounted relatively close together on a card to be separated from one another, and enlarged to a suitable size for viewing, within a relatively confined space.

This is achieved by making full use of the relatively small volume inside the projecting device to enclose a light path considerably longer than the device itself.

Instead of the mirror system described, glass prisms with or without lenses may be used to produce the same results or coherent bundles of glass fibres could be used along with lenses.

Thus the device described can provide a system of programmed learning involving a number of stereoscopic slides projected in three dimensions (1,000 to 2,000 pairs of slides would be a typical number for one learning programme). The slides can be viewed in conjunction with a written text or the text may be in the form of a recording on a tape-recorder and answers to questions in the text can be retained on the acetate strip 15 to be inspected subsequently by a tutor.

The device also enables a student to check his own answers, thus providing continuous feed-back as the learning programme progresses.

Thus in a further aspect the invention provides a programmed visual learning system comprising a set of stereoscopic pairs of slides, a written or spoken (tape recorded) text relating to the images on the slides and including questions relating to those images and a set of transparent sheets having marked thereon answers to the questions in the text.

A teaching programme as described may also be provided using single slides instead of stereoscopic pairs, if it is not necessary for the purpose of the programme to project images in three dimensions.

WHAT I CLAIM IS: 1. Apparatus for viewing pairs of stereoscopic pictures, said apparatus comprising a back projection screen or a pair of such screens arranged side by side, a proJector arranged so as to be able to project images of a pair of stereoscopic pictures on to respective adjacent areas of the screen or to project one said image onto each of said pair of screens and a stereoscope arranged to enable one respective projected image to be viewed with each eye.

2. Apparatus according to claim 1 wherein the screen arrangement comprises two individual back projection screens arranged side by side.

3. Apparatus according to claim 1 wherein the screen arrangement comprises a single back projection screen, the projector being arranged to project the said images onto separate but adjacent areas of the screen.

4. Apparatus according to any preceding claim also including means for supporting sheets and/or rolls of transparent material over one of the two said areas of the screen arrangement so that images projected thereon are substantially coplanar with the transparent material.

5. Apparatus according to claim 4 which includes a pair of parallel rollers positioned on opposite sides of one said area of the screen arrangement whereby an elongate strip of transparent material can be passed across the said screen area while being wound from one roller on to the other.

6. Apparatus according to claim 4 or claim 5 which includes, at the periphery of one said area of the screen arrangement, support means for individual sheets of transparent material.

7. Apparatus according to any preceding claim wherein the stereoscope is located above the screen arrangement and is supported on a bracket projecting from the body of the apparatus.

8. Apparatus according to any preceding claim wherein the projector is adapted to receive and project a pair of stereoscopic slides mounted side by side in a support.

9. Apparatus according to any preceding claim which includes a system of mirrors to project each image on to its respective area of the screen arrangement for viewing by the stereoscope.

10. Apparatus for viewing pairs of stereoscopic pictures, substantially as herein described with reference to, or as illustrated in, the accompanying drawings.

11. A teaching system comprising apparatus according to any preceding claim, one or more pairs of stereoscopic slides adapted to be received and projected by the viewing apparatus and a written or tape recorded text relating to the images in the slides.

12. A teaching system according to claim 11 further comprising at least a first sheet or roll of transparent material superposable over one of the said areas of the screen arrangement and having markings thereon which, when the sheet or roll is in position, indicate a part of an image referred to in the text.

13. A teaching system according to claim 12 comprising a blank second sheet or roll of transparent material superposable over one of the said areas of the screen arrangement to be marked by a student in response to questions in the text, the said first sheet or roll being superposable on the first sheet or roll whereby the markings on the first sheet or roll coincide with correctly positioned markings by the student.

14. A teaching system according to any one of claims 11 to 13 wherein the text is a programmed learning text.

15. A teaching system according to claim 11 substantially as herein described.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. three dimensions (1,000 to 2,000 pairs of slides would be a typical number for one learning programme). The slides can be viewed in conjunction with a written text or the text may be in the form of a recording on a tape-recorder and answers to questions in the text can be retained on the acetate strip 15 to be inspected subsequently by a tutor. The device also enables a student to check his own answers, thus providing continuous feed-back as the learning programme progresses. Thus in a further aspect the invention provides a programmed visual learning system comprising a set of stereoscopic pairs of slides, a written or spoken (tape recorded) text relating to the images on the slides and including questions relating to those images and a set of transparent sheets having marked thereon answers to the questions in the text. A teaching programme as described may also be provided using single slides instead of stereoscopic pairs, if it is not necessary for the purpose of the programme to project images in three dimensions. WHAT I CLAIM IS:

1. Apparatus for viewing pairs of stereoscopic pictures, said apparatus comprising a back projection screen or a pair of such screens arranged side by side, a proJector arranged so as to be able to project images of a pair of stereoscopic pictures on to respective adjacent areas of the screen or to project one said image onto each of said pair of screens and a stereoscope arranged to enable one respective projected image to be viewed with each eye.

15. A teaching system according to claim 11 substantially as herein described.