US3251940A

US3251940A - Light valve apparatus

Info

Publication number: US3251940A
Application number: US337260A
Authority: US
Inventors: Alfred G Roussin
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1964-01-13
Filing date: 1964-01-13
Publication date: 1966-05-17
Anticipated expiration: 1983-05-17
Also published as: FR1420308A

Description

May 17, 1966 A. c5. ROUSSIN LIGHT VALVE APPARATUS Filed Jan. 15, 1964 FIG! 3 3 \J 3 3 $1 5| 1 2 mi ml 1 3 2 3 A INVENTOR W. Y U/ W O R G T flT E A m S L H Y B United States Patent ()fiice 3,2513% Patented May 17, 1966 3,251,940 LIGHT VALVE APPARATUS Alfred G. Ronssin, Morrisviile, N.Y., assignor to General Eieetric Uompany, a corporation of New York Filed Jan. 13, 1964, Ser. No. 337,269 6 Qlaims. (Ci. 178-737) The present invention relates to a light valve apparatus and, more specifically, to a light valve tube suitable for the projection of a television image.

One form of a light valvetube suitable for the projection of a television image comprises an evacuated envelope in which is positioned an electron gun in alignment with a rotatable disk bearing a light-modulating fluid. An elec- -tron beam generated by the electron gun is directed through electrostatic beam deflecting and focusing means and is scanned across a portion of the light-modulating fluid, the beam being controlled to selectively deform the surface of the fluid. The deformations formed in the fluid by the electron beam constitute diffraction gratings which, in conjunction with a light source and a Schlieren optical system, serve to selectively control the passage of light from the source to a screen in accordance with the image being projected.

Such a light valve tube is sensitive to spurious magnetic fields which exist in the vicinity of the tube. Thus, magnetic shielding is required to minimize ambient magnetic fields developed by transformers, motors, etc. which cause erratic operation of the electron beam.

Generally, prior art approaches toward providing magnetic shielding of cathode ray tube devices have been to utilize external magnetic shielding supported by the envelope of the tube. However, in the light valve tube of the present invention the cross-sectional area of the tube in the area where the electrostatic beam focus and deflection system is located is necessarily large to allow the unimpeded passage of light through the electrode system from the light source which is located directly behind the cathode. In such a configuration external magnetic shielding is necessarily both bulky and expensive.

The present invention obviates the necessity of external magnetic shielding while still maintaining the tube free from the adverse effects of spurious magnetic fields.

Accordingly, an object of the invention is to provide an improved light valve tube suitable for the projection of a television image.

Another object is to provide a light valve tube wherein adverse effects due to the presence of spurious magnetic fields are minimized.

Still another object is to provide a light valve tube wherein external magnetic shielding is obviated.

These and other objects are achieved in one embodiment of the invention through the use of electrostatic focus and deflection plates formed from a magnetic shielding material (i.e. a material having a high permeability). The plates are grouped into at least first and second electrode units, the plates of the first unit being provided with offset portions to allow positioning of the first unit in spaced overlapping relationship with respect to the second electrode unit. Similarly, a shield positioned between the second electrode unit and the light-modulating fluid is provided with offset portions arranged to allow placement of the shield in spaced overlapping relationship with the second electrode unit.

The novel and distinct features of the invention are set forth in the appended claims. The invention itself, together with further objects and advantages thereof, may best be understood by reference to the following description and accompanying drawings in which:

FIGURE 1 is a simplified cross-sectional view of a representative light valve tube employing an electrostatic focus-deflection system in accordance with the present invention.

FIGURE 2 is a cross-sectional view taken along the line 22 in FIGURE 1.

FIGURE 3 is a cross-sectional view taken along line 3-3 in FIGURE 1.

FIGURE 4 is a three-dimensional view of one embodiment of the electrostatic focus-deflection system of the present invention.

Referring to FIGURE 1, there is shown a light valve tube 1 located between a light source 2 and a screen (not shown) for the projection of a television image to the screen, the light source 2 being provided with a suitable reflector 3. p

The light valve tube 1 comprises an evacuated envelope 4 in which is located a rotatable disk 5 having a transparent conductive layer 6 positioned on one surface thereof. The disk 5 is rotated in its own plane about its center through a reservoir 7 of the light-modulating fluid by any suitable means. Rotation of the disk 5 through the reservoir 7 causes a continuously replenished layer of modulating fluid 8 to form on the conductive layer 6.

An electron gun 9 is positioned in a necked-down portion 10 of the envelope opposite the layer of modulating fluid 8. The electron gun 9 comprises an electronemitting cathode electrode 11 in conjunction with an electron lens comprising first electrode 12 and second electrode 13. An apertured plate 14 is positioned in the path of the electron beam 15 generated by the cathode 11, the aperture in the plate defining the size and shape of the electron beam. The electron beam 15 impinges upon the layer of light-modulating fluid 8 and deposits charges thereon. The charges are attracted to the conductive layer 6 to cause deformations 16 in the layer of modulating fluid 8. The electron beam 15 is swept across the layer of modulating fluid 8 by electrostatic focus and deection means comprising a first electrode unit 17, a second electrode unit 18 and a shield 19, the beam being controlled to selectively deform the light-modulating fluid to form a diffraction grating thereon.

Light rays from the source 2 as reflected by the reflector 3 are directed by a lenticular lens system 20 formed on the rear wall of the envelope 4 to the raster area. The lenticular lens.system 20 is employed to increase the optical eificiency of the system by dividing the light from the source 2 into a number of discrete sources.

By modulating the electron beam 15 through the application of suitable potentials to the electrostatic focus and deflection electrodes of

electrode units

17 and 18, the diffraction grating formed by the deformations 16 in the layer of modulating fluid 8 is selectively controlled. Through the use of a Schlieren optical system, an image representative of the electron beam modulating intelligerice is projected to the screen.

In accordance with the present invention, the

electrode units

17 and 18 and shield 19 are formed of magnetic shielding material (i.e. material exhibiting a high permeability) and are arranged in spaced, overlapping relationship with the adjacent units to preclude the presence of spurious fields in the region within the electrode units. The electrode unit 17 comprises four

electrodes

21, 22, 23 and 24, the electrodes being provided with offset portions 25, '26, 27 and 28, respectively. The electrodes 21-24 are arranged in an open-ended box structure, each electrode being arranged in spaced overlapping relationship with respect to adjacent electrodes.

The inter-relationship of the electrodes 21-24 is more clearly shown in FIGURE 2. As depicted, the

electrodes

21 and 23 are provided with angled side portions 21a and 23a, respectively, so as to allow the electrodes to be placed in spaced overlapping relationship with the

electrodes

22 and 24.

69 The electrode unit 18 comprises electrodes 29, 3t), 31 and 32. The electrodes 29-62 are arranged in an openended box structure. Each of the electrodes 29-32 is arranged in spaced overlapping relationship with adjacent electrodes to provide substantially complete shielding. The electrodes of the

electrode units

17 and 18 are provided with electrical leads 33 to allow the application of suitable sweep and focus voltages to the electrodes.

The shield 19 comprises a flat box-like structure having one completely open end and one partially closed end having an aperture thereon. The shield is provided with offset portions 36.

The

electrode units

17 and 18 and the shield H are arranged so that the offset portions 28 of the electrode 21-24, respectively, are positioned in spaced overlapping relationship with the electrodes 29-32. Similarly, the offset portions 36 of the shield 19 are positioned in spaced overlapping relationship with respect to the electrodes 2942.

In FIGURE 3 it is more clearly shown how the offset portions 36 of the shield 19 overlap the electrodes 2-32. As depicted, the electrodes 29-32 are also provided with angled side portions 29a and 32a respectively to allow placement of the electrodes in spaced overlapping relationship with each other.

The assembled relationship of the

electrode units

17 and 18 and shield 19 can be more clearly appreciated by reference to the perspective drawing of FIGURE 4 wherein it is shown 'how adjacent units are arranged in spaced, overlapping relationship to provide substantially complete shielding.

In accordance with the present invention the area within the electrode units is completely shielded from spurious fields and erratic operation of the electron beam is prevented. By positioning the elements in spaced, overlapping relationship substantially complete shielding is achieved since gaps between the electrodes are eliminated while still maintaining the necessary electrical isolation between the various elements.

It will be appreciated that although the invention has been specifically directed toward an eight electrode focus and deflection system, other electrode configurations might also be utilized.

Although the invention has been described with respect to certain specific embodiments, it will be appreciated that modifications and changes may be made by those skilled in the art Without departing from the spirit and scope of the invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A light valve apparatus for positioning between a light source and a screen for the projection of an image on the screen, said apparatus comprising:

(a) an evacuated envelope,

(b) a light-modulating fluid positioned in said envelope and arranged to control the passage of light from the source to the screen,

(c) cathode means positioned in said envelope and arranged to emit a beam of electrons impingent upon said light-modulating fluid to form a diffraction grating thereon for selectively controlling the passage of light from the source to the screen in accordance with the image being projected,

(d) electrostatic focusing and deflecting means positioned between said cathode means and said lightmodulating fluid in the path of said electron beam,

(e) said last-mentioned means including a plurality of electrode units axially disposed along said electron beam,

(f) each of said electrode units being formed from material exhibiting a high permeability, and

(g) adjacent ones of said electrode units being arranged in spaced overlapping relationship.

2. The apparatus as defined in claim 1 wherein each of said electrode units comprise four electrodes arranged to define an open-ended box structure axially aligned with said electron beam, adjacent ones of said electrodes being arranged in spaced, overlapping relationship.

3. The apparatus defined in claim 1 wherein said electrostatic focusing and deflecting means further includes an apertured shield positioned between the electrode unit closest to the light-modulating fluid and the light-modulating fluid, said shield bein arranged in spaced overlapping relationship with said last-mentioned electrode unit.

4. An electrostatic focusing and deflecting system for an electron beam device, said system comprising:

(a) a plurality of electrode units axially disposed along the electron beam,

(h) each of said electrode units being formed from material exhibiting a high permeability, and

(0) adjacent ones of said electrode units being arranged in spaced overlapping relationship.

5. The system as defined in claim 4 wherein each of said electrode units comprises four electrodes arranged to define an open-ended box structure axially aligned with said electron beam, adjacent ones of said electrodes being positioned in spaced overlapping relationship.

6. A light valve apparatus for positioning between a light source and a screen for the projection of an image on the screen, said apparatus comprising:

(a) an evacuated envelope,

(b) a light modulating fluid positioned in said envelope and arranged to control the passage of light from the source to the screen,

(e) said last-mentioned means including at least first and second electrode units axially disposed along said electron beam, each of said electrode units being formed from material exhibiting a high permeability,

(f) said first electrode unit comprising four electrodes provided with offset portions, said electrodes being arranged to define an open-ended box structure axially aligned with said electron beam,

g) said second electrode unit comprising four electrodes arranged to define an open-ended box structure axially aligned with said electron beam,

(h) said offset portion of said electrodes of said first electrode unit being arranged in spaced overlapping relationship with said electrodes of said second electrode unit.

No references cited.

DAVID G. REDINBAUGH, Primary Examiner.

ROBERT RICHARDSON, Assistant Examiner.

Claims

1. A LIGHT VALVE APPARATUS FOR POSITIONING BETWEEN A LIGHT SOURCE AND A SCREEN FOR THE PROJECTION OF AN IMAGE ON THE SCREEN, SAID APPARATUS COMPRISING: (A) AN EVACUATED ENVELOPE, (B) A LIGHT-MODULATING FLUID POSITIONED IN SAID ENVELOPE AND ARRANGED TO CONTROL THE PASSAGE OF LIGHT FROM THE SOURCE TO THE SCREEN, (C) CATHODE MEANS POSITIONED IN SAID ENVELOPE AND ARRANGED TO EMIT A BEAM OF ELECTRONS IMPINGENT UPON SAID LIGHT-MODULATING FLUID TO FORM A DIFFRACTION GRATING THEREON FOR SELECTIVELY CONTROLLING THE PASSAGE OF LIGHT FROM THE SOURCE TO THE SCREEN IN ACCORDANCE WITH THE IMAGE BEING PROJECTED, (D) ELECTROSTATIC FOCUSING AND DEFLECTING MEANS POSITIONED BETWEEN SAID CATHODE MEANS AND SAID LIGHTMODULATING FLUID IN THE PATH OF SAID ELECTRON BEAM, (E) SAID LAST-MENTIONED MEANS INCLUDING A PLURALITY OF ELECTRODE UNITS AXIALLY DISPOSED ALONG SAID ELECTRON BEAM, (F) EACH OF SAID ELECTRON UNITS BEING FORMED FROM MATERIAL EXHIBITING A HIGH PERMEABILITY, AND (G) ADJACENT ONES OF SAID ELECTRODE UNITS BEING ARRANGED IN SPACED OVERLAPPING RELATIONSHIP. 4 AN ELECTROSTATIC FOCUSING AND DEFLECTING SYSTEM FOR AN ELECTRON BEAM DEVICE, SAID SYSTEM COMPRISING: (A) A PLURALITY OF ELECTRODE UNITS AXIALLY DISPOSED ALONG THE ELECTRON BEAM, (B) EACH OF SAID ELECTRODE UNITS BEING FORMED FROM MATERIAL EXHIBITING A HIGH PERMEABILITY, AND (C) ADJACENT ONES OF SAID ELECTRODES UNITS BEING ARRANGED IN SPACED OVERLAPPING RELATIONSHIP.