Character Viewing And Reproducing Apparatus For A Photocomposing Machine

Abstract

Light pulses in the form of selected character images are retained by a luminescent layer which is activated by the illuminated portion of a superimposed photoconductive layer onto which the character images are projected. Due to feedback from the luminescent layer to the photoconductive layer, the character image is retained for viewing as long as a voltage is applied to the superimposed layers. The character is also projected onto a record carrier which receives a light pulse only when a shutter is operated after the correctness of the selected character has been determined by viewing the character image, which is then erased.

Description

BACKGROUND OF THE INVENTION

The present invention relates to optical typewriters and photocomposing machines in which selector means, in the form of manually operated keys, effect the selection of characters which are projected onto a record carrier to produce recorded characters on the same.

In photocomposing typewriters it is desired that the recorded text can be simultaneously viewed so that errors can be detected, and the length of the lines determined before the characters are recorded on the record carrier.

Photocomposing machines are known which expose an electrostatically charged record carrier, for example a zinc oxide paper. Electrical charges are dissipated from illuminated portions of the record carrier so that only the unexposed portions remain electrically charged, and can be made legible in a developing and toning device which makes the characters appear on the record carrier. In accordance with the prior art, it is not possible to read the electrostatically recorded characters before the same are permanently fixed.

SUMMARY OF THE INVENTION

It is one object of the invention to overcome this disadvantage of known optical typewriters and photocomposing machines, and to provide a photoelectric storage and viewing device which retains character images projected onto the same for viewing by the operator, until the storage and viewing device is deenergized, and a character reproduced.

Another object of the invention is to provide a photoelectric storage and viewing device which consists of a plurality of photoamplifier elements arranged in crossing lines and being substantially smaller than the character images projected thereon.

Another object of the invention is to provide a storage and viewing device whose height corresponds to at least one character, and whose width corresponds to a plurality of characters, for example to the length of a line of characters.

Another object of the invention is to provide a storage and viewing device which retains a stored character image for an indefinite time, until it is erased by the operator.

Another object of the invention is to retain character images by feedback from luminescent elements to photoconductive elements of the photoelectric storage and viewing device.

With these objects in view, an apparatus according to the invention, which is particularly suited for photocomposing machines and optical typewriters, comprises an alpha-numerical series of selector means, such as typewriter keys; character reproducing means operated by the character keys to project first light pulses in the form of selected character images onto a record carrier through a shutter; a photoelectric storage and viewing device illuminated by successive second light pulses representing the same character images and retaining, while energized, the character images for viewing after termination of the respective light pulses; and control means, including circuit means and switches, for connecting terminals, preferably in the form of plates, with a voltage during successive operations of the character keys.

As a result, the retained character images can be viewed for a desired time until the shutter has been operated to reproduce the character on a record carrier, whereupon the voltage is disconnected from the terminals, and the storage and viewing device is deenergized and the stored character images erased.

The height of the viewing area of the storage and viewing device corresponds to at least one character, and its width to a plurality of characters, which may correspond to a word of average length, or to an entire line.

In the preferred embodiment of the invention, the storage and viewing device includes a plurality of photoamplifier elements arranged in crossing lines, and each photoamplifier element includes a photoconductive element and a luminescent element. The photoconductive elements form a first layer and the luminescent elements form a second layer superimposed on the first layer. When the character reproducing means under the control of the keys project successively different character images onto a plurality of the photoconductive elements, the electric resistance of the same is reduced, and consequently the respective luminescent elements are energized and emit light in the form of viewable character images. The light produced by each energized luminescent element again reduces the resistance of the respective photoconductive element after the light pulse representing a selected character has ended, so that the luminescent elements remain energized for an indefinite time period, and until the voltage is disconnected from the terminals of the device by opening a switch.

Preferably, a diaphragm sheet is located between the photoconductive layer and the luminescent layer which has an aperture for each photoamplifier element so that the amount of fed back light can be controlled. It is also possible to use a diaphragm which is translucent to a desired degree so that the amount of fed back light is also controlled.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view illustrating an optical typewriter provided with a character viewing apparatus in accordance with the invention;

FIG. 2 is a fragmentary perspective rear view of a photoelectric storage and viewing device in accordance with one embodiment of the invention, and also including a schematic circuit diagram;

FIG. 3 is a fragmentary perspective front view of the embodiment shown in FIG. 2;

FIG. 4 is partly a circuit diagram, and partly a fragmentary perspective view of a storage and viewing device in accordance with another embodiment of the invention;

FIG. 5 is a fragmentary cross sectional view of a storage and viewing device according to the invention shown on a larger scale;

FIG. 5a is a fragmentary cross-sectional view illustrating a modification of the diaphragm shown in FIG. 5, and

FIG. 6 is a fragmentary exploded perspective view illustrating another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1, an optical typewriter 2 has character selector means in the form of a keyboard 3 whose keys 3 a are respectively associated with alpha-numerical characters. A space bar 3b is also provided.

The typewriter 2 has transverse guide rails 2a on which a carriage 4 is mounted for movement along a record carrier sheet 5 and a platen, of which only the knob 2b is shown. Upon operation of any character key 3a, or of the space bar 3b, an escapement mechanism of conventional construction, not shown, effects stepwise movement of the carriage 4 across the record carrier sheet 5.

Carriage 4 is a closed casing in which character reproducing means as described in U.S. Pat. No. 3,228,313 are mounted, and such character reproducing means may include a lamp and templates having the outline of characters so that light pulses in the form of character images are produced. An optical guide means 12, which is preferably made of parallel light conductive glass fibers, guides and projects the character images onto the photoelectric storage and viewing device 10, while a corresponding light guiding and projecting means 12 a projects character images onto the record carrier sheet 5 which is made sensitive to light so that the character images can be permanently fixed on the record carrier sheet 5 in a well known manner which is not an object of the invention A photoelectric storage and viewing device 10 is shown in FIGS. 2, 3 and 5. The device has a transparent terminal plate 15 in the rear, and a transparent terminal plate 16 in front which are electrically connected by a switch 21 to a voltage source 20.

The photoelectric storage and viewing device 10 is composed of a great number of photoamplifier elements 11 arranged in crossing lines, each photoamplifier element 11 being substantially smaller than a character image 4a projected by light guiding means 12, and than a character image 4b projected by light guiding means 12 a onto the record carrier sheet 5. Each photoamplifier element 11 includes a photoconductive elements 13 a and a luminescent element 14 a. The photoconductive element 13 a form a photoconductive rear layer 13, and the luminescent elements 14 a form a luminescent front layer 14.*(*described in "Journal of the Optical Society of America" Volume 44, No. 4, Apr., 1954.) However, the photoamplifiers 11 are separated from each other in the two layers by crossing insulating strips 11a and 11b.

When the keys 3 a are operated, the character reproducing means in casing 4 project pulses representing character images through light guiding means 12 onto the transparent conductive terminal 15 through the same onto the photoconductive layer 13, illuminating a limited number of photoconductive elements 13 a forming the outline of the character 4 a, shown to be a E. If the intensity of the light is sufficient, the resistance of the photoconductive elements 13 a forming the character image 4 a is reduced so that the voltage 20 is applied through the closed switch 21 to the terminal plates 15 and 16 and the respective conductive elements 13 a whereby the luminescent elements 14 a forming the outline of the character image 4 a are energized and activated to produce light so that the character image 4 a is visible in front of the storage and viewing device 10. Since terminal 16 is transparent, viewing of the luminescent layer 14 is possible. A voltage of about 400 Hertz having 250 volts is suitable.

Only a short light pulse is produced when a key 3 a is operated and released, but the character image 4 a formed on the luminescent layer 14 is nevertheless retained since the activated luminescent elements 14 a illuminate the respective photoconductive elements 13 a also forming the outline of the character image 4 a , so that the resistance of the respective photoconductive elements remains low, and the voltage continues to pass through the respective luminescent elements 14 a to maintain the same in an active condition. Due to this feedback, which is indicated by arrows in FIG. 5, the character image 4 a is retained for viewing after termination of the light pulse produced by operation of a key 3 a and of the character reproducing means in casing 4.

The size of the photoamplifier elements 11a, and of the respective photoconductive elements 13 a and luminescent elements 14 a , is selected so that each photoconductive element 13 a is associated with a light guiding filament of the light guiding means 12. Due to the small size of the photoamplifier elements 11, a good resolution of the character images 4 a is obtained so that the same are easily legible.

Between the photoconductive layer 13 and the luminescent layer 14, a diaphragm plate 17 is disposed by which the amount of light fed back from luminescent elements 14 a to photoconductive elements 13 a is controlled. In one embodiment of the diaphragm, the same is translucent, and is constructed to be just thick enough to permit a suitable amount of light to pass therethrough from a luminescent element to a photoconductive element, as indicated by arrows in FIG. 5. It is also possible to use a colored translucent diaphragm. In another embodiment, a diaphragm 17' has an aperture between each pair of photoconductive and luminescent elements 13 a , 14 a forming a photoamplifier element 11, and the size of the aperture 17 a is selected to obtain the desired amount of feedback from the luminescent element 14 a .

When the keys 3 a are successively actuated for short time periods and then released, the escapement mechanism, not shown, causes stepwise movement of carriage 4 with the character reproducing means, not shown, along the storage and viewing device 10 so that character images are projected onto the same in adjacent positions to first form words, and then an entire line. Due to the above explained feedback, the character images 4 a are retained after termination of the light pulse produced under the control of a key 3 a , and all characters of a word or of a line appear visible on the storage and viewing device 10. In the embodiment of FIG. 1, the size of the character images 4 a is selected so that only a limited number corresponding to one or two words appears on the viewing device, but evidently it is possible to use smaller character images and to view an entire line of character images. When the operator is satisfied that the characters appearing on the storage and viewing device 10 contain no error, the switch 21 is operated, and the storage and viewing device is deenergized so that the luminescent elements 14 a no longer produce light, and the character images 4 a are erased.

As shown in FIG. 4, a character storage and viewing device 10' may consist of a plurality of storing and viewing means 10 a to 10 f , for example, each of which comprises a plurality of photoamplifiers 11, not shown in FIG. 4, but constructed and arranged as described with reference to FIGS. 2, 3 and 5. Each storage and viewing means 10 a to 10 f has a sufficient size for the viewing of several character images. The advantage of the embodiment of FIG. 4 is that small groups of character images can be erased by operation of switches 21 a to 21 f without requiring erasing of the entire line, or of the entire text. After erasing of the character image in one of the storage and viewing means 10 a to 10 f , the respective portion of the text is again typed in the proper position by operation of keys 3 a so that the character images appear on the respective storage and viewing means 10 a to 10 f .

FIG. 6 schematically illustrates another embodiment of the invention used with a typewriter as described with reference to FIG. 1. The light guiding means 12 consists of parallel light guiding glass filaments so that the selected character image is projected onto the storage and viewing device 10 and retained by the same for an indefinite period until a switch 21 is opened. FIG. 6 also shows other positions 12' of the stepwise moving light guiding means 12.

The character images appearing on the luminescent layer 14 and visible through the transparent terminal plate 16 are projected onto a semitransparent mirror 23 which directs the light partly to a reflecting surface 24 by which the character images are projected onto a frosted glass plate 25 for viewing. After the operator has checked the correctness of the character images appearing on the frosted glass plates 25, a shutter means 27 is opened to permit passage of the light passing through the semitransparent mirror 23 to the record carrier sheet 5 where the light produces character images. A shutter 27 may also be provided in the embodiment of FIG. 1 between the light guiding means 12 a and the record carrier sheet 5 so that permanent printing takes place only after the correctness of the text appearing on the storage and viewing device 10 has been determined by the operator.

The control of the recorded character images may also be effected by using a fully reflecting mirror substantially in the position of mirror 23 in FIG. 6. The reflecting mirror has a position in which the character images are projected onto the frosted glass plate 25 for viewing, as described with reference to FIG. 6. When the viewed text has been approved, the reflecting mirror is removed so that the character images on the storage and viewing device 10 directly act at the open shutter 27 to expose a corresponding portion of record carrier sheet 5.

A storage and viewing device 10 is preferably manufactured by superimposing on the transparent electrically conducting plate 15 the photoconductive layer 13, the transparent and conductive diaphragm 17, the luminescent layer 14, and finally the transparent and electrically conducting plate 16. During the application of the photoconductive layer and of the luminescent layer, grid-shaped screens are used for obtaining the division of the layers into photoconductive elements and luminescent elements.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of character viewing apparatus for photocomposing machines differing from the types described above.

While the invention has been illustrated and described as embodied in a photoelectric storage and viewing device having a luminescent layer and photoconductive layer composed of photoamplifying elements, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Claims

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

1. Character viewing and reproducing apparatus comprising a series of selector means representing a series of alpha-numerical characters; character reproducing means operated by said selector means to transmit light pulses in the shape of selected character images of said series along first and second paths; supporting means for supporting a photosensitive record carrier sheet in said first path between said supporting means with said record carrier sheet and said character reproducing means; a photoelectric storage and viewing device having terminals for being energized, and located in said second path so as to be illuminated by light pulses representing selected character images, said storage and viewing device retaining, while energized, said character images for viewing after termination of the respective light pulses; and control means for connecting said terminals with a voltage during successive operations of said selector means so that the character images can be viewed for a desired time whereby after said viewed character images have been found correct, said shutter can be operated to effect on said record carrier sheet, photographic reproduction of selected character images projected along said first path while said control means connects said terminals with said voltage; said control means being operable to disconnect said voltage from said terminals so that said storage and viewing device is deenergized and said retained characters are erased after reproduction on said record carrier sheet.

2. An apparatus as claimed in claim 1 wherein said control means include manually operated switch means.

3. An apparatus as claimed in claim 1 wherein said character reproducing means is located between said supporting means and said storage and viewing device, and projects said light pulses in opposite directions toward a record carrier sheet on said supporting means and toward said storage and viewing device.

4. An apparatus as claimed in claim 1 wherein said first and second paths are aligned.

5. An apparatus as claimed in claim 1 wherein said selector means include a keyboard with keys associated with the characters of said series; and wherein said storage and viewing device is located rearward of said keyboard.

6. An apparatus as claimed in claim 1 wherein said control means include manually operated switch means; wherein said character reproducing means is located between said supporting means and said storage and viewing device, and projects said light pulses in opposite directions toward a record carrier sheet on said supporting means and toward said storage and viewing device; wherein said first and second paths are aligned; wherein said selector means include a keyboard with keys associated with the characters of said series; and wherein said storage and viewing device is located rearward of said keyboard and forward of said character reproducing means.

7. Apparatus as claimed in claim 1 wherein said storage and viewing device has a height at least equal to the height of one character image, and a width at least equal to the width of a plurality of said character images.

8. Apparatus as claimed in claim 1 comprising a semitransparent mirror located between said storage and viewing device and said shutter; reflecting means; and a frosted glass plate disposed so that light reflected by said semitransparent mirror is deflected by said reflector means onto said frosted glass plate for observation of the character images retained by said photoelectric storage and viewing device.

9. Apparatus as claimed in claim 1 wherein said storage and viewing device includes a plurality of storage and viewing means arranged in a common viewing plane; wherein each storage and viewing means has a pair of terminals connected with said control means; and wherein said control means includes switches operable for selectively energizing and deenergizing each of said storage and viewing devices.

10. Apparatus as claimed in claim 1 wherein said character reproducing means include light guiding means consisting of parallel glass fibers; and wherein the resolution of said glass fibers corresponds substantially to the resolution of said storage and viewing device, each character image being composed of light points respectively associated with said glass fibers.

11. Apparatus as claimed in claim 1 wherein said storage and viewing device includes a photoconductive layer, a luminescent layer, and terminals in the form of light permeable terminal plates located on opposite sides of the superimposed photoconductive and luminescent layers.

12. Apparatus as claimed in claim 1 wherein said storage and viewing device includes a plurality of photoamplifier elements arranged in crossing lines, each photoamplifier element including a photoconductive element and a luminescent element, said photoconductive elements forming a first layer and said luminescent elements forming a second layer superimposed on said first layer; wherein said character reproducing means projects each character image onto a plurality of said photoconductive elements whereby the electric resistance of the same is reduced; and wherein said terminals are transparent terminal plates between which said first and second layers are located so that illuminated photoconductive elements cause energization of the respective luminescent elements which feed back light to the respective photoconductive elements after termination of said light pulses whereby viewable character images are retained by energized luminescent elements until said voltage is disconnected from said transparent terminal plates by said control means.

13. Apparatus as claimed in claim 12 wherein said character reproducing means include light guiding means having a plurality of parallel glass fibers disposed in crossing lines and having a size and position corresponding to the size and position of said photoconductive elements so that points of each character image are transmitted from said glass fibers to corresponding photoamplifier elements of said storage and viewing device.

14. Apparatus as claimed in claim 12 wherein said storage and viewing device includes a diaphragm sheet located between said first and second layers for limiting the amount of light fed back from said luminescent elements to said photoconductive elements.

15. Apparatus as claimed in claim 14 wherein said diaphragm sheet is translucent.

16. Apparatus as claimed in claim 14 wherein said diaphragm sheet has an aperture located between each pair of luminescent and photoconductive elements forming a photoamplifier element, the size of said aperture being selected to determine the amount of light fed back from said luminescent elements to said photoconductive elements.