US3498722A - Optical alignment apparatus - Google Patents

Description

2 Sheets-Sheet 1 Filed Sept. 29, 1966 INVENTOR. Nat/700D. Lev/n iusw 6m March 3, 1970 N. D. LEVIN 3,498,722

' OPTICAL ALIGNMENT APPARATUS Filed Sept. 29, 1966 2 Sheets-Sheet 2 INVENTOR.

Na/h on D. Lev/n United States Patent 3,498,722 OPTICAL ALIGNMENT APPARATUS Nathan D. Levin, Highland Park, Ill., assignor to Admiral Corporation, Chicago, Ill., a corporation of Delaware Filed Sept. 29, 1966, Ser. No. 583,018 Int. Cl. G01b 11/26; G02b 21/18 U.S. Cl. 356138 8 Claims ABSTRACT OF THE DISCLOSURE A device for accurately and quickly aligning a color picture tube lighthouse lens assembly including an accurately locatable baseplate carrying a plurality of microscopes vertically oriented with respect to a corresponding plurality of reference marks on the lens assembly. The microscopes are precisely focused on the reference marks of a lens assembly in a lighthouse known to be in prop r alignment, whereafter the baseplate with microscopes affixed may be moved to another lighthouse for quickly and accurately aligning the lens assembly thereof.

This invention relates in general to alignment apparatus and in particular to optical alignment apparatus for picture tube lighthouses.

Picture tubes of the shadow mask variety are in widespread use in todays color television receivers. Typically, picture tubes of this type comprise a glass envelope consisting of a funnel and a face panel secured together, an electron-sensitive phosphor screen on the inside of the face panel, an aperture mask fixed close behind the phosphor screen, and an electron gun assembly mounted in the neck of the picture tube funnel. The electron sensitive phosphor screen usually comprises a large number of individual phosphor dots grouped in triads. Each of the triads includes phosphor dots of three primary colors, e.g., red, blue, and green. Corresponding to each of these phosphor dot triads is a single aperture in the shadow mask. The electron gun assembly usually comprises three individual electron guns arranged in a delta fashion for producing three separate electron beams.

In operation the three electron beams are scanned across the screen. The beams pass through the apertures in the shadow mask and strike the phosphor dots on the screen. In Order to produce a picture with color purity, it is necessary to have the electron beam from each one of the three electron guns strike only its associated color phosphor dot in each triad. In other words, the electrons from the blue gun should strike only the blue phosphor dots, and so on. Thus it is apparent that the accu-,

rate positioning of each phosphor dot with respect to the shadow mask aperture associated with it and also with respect to the source of its associated electron beam is very critical.

The phosphor dots on the face panel are produced on a one-color-at-a-time basis. This can be accomplished by slurrying a light-sensitive emulsion containing phosphor powder of a particular color, blue, for example, on the inside surface of the face panel and then exposing the emulsion to a light source using the apertured shadow mask as a negative. The light beams passing through the individual apertures strike the light-sensitive emulsion, thereby causing the emulsion and blue phosphor powder to adhere to the face panel. The unexposed portion of the emulsion is then washed off, leaving blue phosphor dots only in the areas exposed to the light. This process can then be repeated two additional times to produce red and green phosphor dots.

Each operation of exposing the light-sensitive emulsion is usually carried out by employing a lighthouse ar- 3,498,722 Patented Mar. 3, 1970 rangement which includes a collimator assembly, a lens assembly, and a panel support assembly. The collimator assembly includes a source of light and a collimator having a small tip to simulate a point light source. The lens assembly includes a lens and a lens holder to support the lens above the collimator tip. The panel support assembly supports the picture tube face panel above the lens assembly and collimator assembly. The lighthouse arrangement, particularly the lens, is designed so that when the collimator assembly, the lens assembly, and the panel support assembly are properly positioned with re spect to each other the paths of the light beams from the lens to the face panel on the panel support assembly simulate the paths of the electron beam from one of the electron guns during operation of the picture tube. It is well-known that many ditferent lens designs can be employed in a lighthouse arrangement to accomplish the required light-optical analogy to electorn beam travel, but n every case it is vital that the collimator assembly, the lens assembly, and the panel support assembly be accurately aligned.

Since it is necessary to produce picture tubes on a mass production basis, it is most common to employ a group of lighthouse arrangements to expose the same set of phosphor d ts on numreous picture tube panels. Furthermore, since it is also common to employ a separate lighthouse arrangement for each of the three sets of color phosphor dots on a particular picture tube panel, three groups of lighthouse arrangements are required. Each of the lighthouse arrangements Within a particular group must have its alignment of collimator assembly, lens assembly, and panel support assembly as nearly identical as possible to the alignment of the corresponding assemblies in other lighthouses in order that an interchangeable product will result. Moreover, this requirement of interchangeability is even more stringent with three groups of lighthouse arrangements since interchangeability must ex st among all lighthouses in a particular group with respect to all lighthouses in the other groups.

In the past it has been necessary to align each of the lighthouses on an individual basis. This involved manipulating the assemblies and checking the light beam landings on a reference face panel to determine whether the light beams are striking the face plate at points which would produce correctly positioned phosphor dots. Obviously this procedure is extremely time consuming and highly unlikely to result in corresponding alignment from lighthouse to lighthouse with the degree of accuracy required for a completely interchangeable product.

Therefore, it is the principal object of this invention to provide alignment apparatus for use in accurately reproducing the alignment of a plurality of individual elements.

It is a further object of this invention to provide alignment apparatus for accurately recording the alignment of a reference lighthouse arrangement in an optical manner.

This invention features alignment apparatus which can be used to reproduce the alignment of a plurality of individual elements or assemblies where each of the elements has at least one accurately positioned reference point associated therewith.

In a preferred embodiment thereof this invention features an optical alignment apparatus for picture tube lighthouse arrangements which enables the accurate reproduction of the alignment of the collimator assembly, lens assembly, and panel support assembly in a reference picture tube lighthouse arrangement.

The optical alignment apparatus of this invention generally comprises a flat plate having a configuration that simulates the dimensions of a picture tube face panel and a plurality of individual microscope assemblies mounted on the plate. The flat plate is adapted to be mounted on the panel support assembly of the reference picture tube lighthouse arrangement and the individual microscope assemblies are positioned on the fiat plate so that they can be focused on individual reference points associated with the collimator assembly and lens assembly. In this manner the alignment apparatus records the alignment of the collimator assembly, lens assembly, and panel support assembly in the reference picture tube lighthouse arrangement with microscopic accuracy and can be used to duplicate this alignment in other lighthouse arrangements having corresponding assemblies.

The advantage of using the optical alignment apparatus of this invention is apparent since it facilitates the duplication of the alignment in a reference lighthouse arrangement with minimum time and effort and maximum accuracy.

Other objects, features, and advantages of this invention and a complete understanding thereof will be gained from a consideration of the following description in conjunction with the accompanying drawings in which:

FIG. 1 is an exploded perspective view of a lighthouse arrangement with an alignment device in accordance with this invention.

FIG. 2 is a perspective assembly view of a lighthouse arrangement with an alignment device according to this invention.

FIG. 3 is a view of the alignment apparatus taken along the lines 33 in FIG. 2.

FIG. 4 is a view taken along the lines 4-4 in FIG. 2, looking into the eyepiece of one of the microscopes.

In FIG. 1 a lighthouse arrangement including a collimator assembly 20, a lens assembly 30, and a panel support assembly 40, is shown in conjunction with an alignment device 50 constructed in accordance with this invention. A structure composed of plate 10, four columns 12, and table 11 with a rectangular opening 14 therein provides support for collimator assembly 20, lens assembly 30, and panel support assembly 40.

Collimator assembly includes a light source 21 and a light collimator 22 which has a tip 23 projecting through aperture 25 in plate 24 at the top of collimator assembly 20. As shown collimator assembly 20 is mounted in hole 15 in plate 10.

Lens assembly includes a lens holder 31 and a lens 32. Lens 32 fits into an aperture 37 in lens holder 31 and rests on a lip 38. Two lens holder pins 39 can be inserted through holes 36 in lens holder 31 and through holes 17 in plate 10 to fix the position of the assembly 30 on plate 10. Two cross marks 34 provide reference points for lens assembly 30, the function of which will be described later.

Panel support assembly 40 comprises a support table 41, three panel locating blocks 42 mounted on support table 41, and three panel support blocks 44 also mounted on support table 41. Two mounting pins 47 may be inserted through holes 46 in support table 41 and through holes 18 in table 11 to secure panel support assembly 40 in a particular position on table 11.

Alignment apparatus 50 consists essentially of a support means, shown as a flat plate 51, and an optical means comprising three individual microscope assemblies 52, 53, and 54. Mounting blocks are fastened on the underside of flat plate 51 in positions corresponding to panel supporting blocks 44 on support table '41. Microscope assemblies 52, 53, and 54 are mounted on fiat plate 51 in three apertures 56. Each individual microscope assembly is secured in apertures 56 by a pair of mounting fingers 57. Apertures 56 are large enough to accommodate the microscope assemblies in various positions. Each microscope assembly has an eyepiece 60, a focus adjustment mechanism 59, and an auxiliary lens system 58 to increase the focal length.

Lens 32 is shown inserted in lens holder 31. Panel support assembly 40 is secured in position on table 11 by mounting pins 47. Flat plate 51 is indexed on panel support assembly 40 by panel locating blocks 42 with blocks 55 mounted on panel supporting blocks 44. Microscope assemblies 52, 53, and 54 are positioned in apertures 56 so that microscope assemblies 52 and 54 can be focused on cross marks 34 on lens assembly 31 and microscope assembly 153 can be focused on collimator tip 23 in collimator assembly 20. This is shown by the center lines drawn through the individual microscope assemblies to the particular reference points on which they are focused. The reasons for this focusing on reference points associated with the collimator assembly 20 and lens assembly 30 will be discussed in greater detail below.

In FIG. 3 a top view of alignment apparatus 50 in position on panel support assembly 40 is shown. In this view the indexing of fiat plate 51 on panel support assembly 40 by panel locating blocks 42 is clearly shown. Plate 51 simulates in configuration a picture tube face panel, the perimeter of which is shown by dotted lines 80. In this view it is also clearly shown that microscope assemblies 52, 53, and 54 can be located in various positions within apertures 56. Of course, apertures 56 are located on plate 51 with general reference to the positions of the reference marks associated with collimator assembly 20 and lens assembly 30 which are shown in FIGURES 1 and 2.

In FIG. 4 a view of the top of microscope assembly 53 is shown. One of the lenses 62 in microscope assembly 53 is shown with an appropriate reticle such as crosshair 63 thereon. It is to be understood that each of the other microscope assemblies 52 and 54 have corresponding lenses with appropriate rectiles thereon.

Referring back to FIG. 2 in combination with FIG. 3, it is apparent that alignment apparatus 50 can be used to record in a very accurate manner the relative alignment of panel support assembly 40, lens assembly 30, and collimator assembly 20. By positioning microscope assemblies 52 and 54 so that the reticle in each is accurately focused on one of the cross marks 34 on lens assembly 31, the position of panel support assembly 40 with respect to lens assembly 30 is accurately recorded. By positioning microscope assembly 53 so that its reticle focuses exactly on collimator tip 23, the position of panel support assembly 40 with respect to collimator assembly 20 is accurately recorded.

At this point it is to be understood that alignment apparatus 50 must be first set up with respect to a reference lighthouse arrangement, that is to say, with respect to a lighthouse arrangement in which the alignment of collimator assembly 20, lens assembly 30, and panel support assembly 40 has been previously determined by a trial and error method. This method usually involves placing a reference face panel on support assembly 40 and manipulating the position of lens assembly 30 and panel support assembly 40 until the light beam landings on the reference face panel are correctly positioned. This is a timeconsuming procedure and must be done very carefully to insure that properly positioned phosphor dots will be produced on subsequently exposed face panels. Once the proper position of lens assembly 30 is determined, lens holder 31 is fixed in position on plate 10 by lens holder pins 39. Panel support assembly 40 is also secured in its correct position on table 11 by mounting pins 47.

Since a separate lighthouse arrangement is used for each set of phosphor dots to be developed on a particular face panel, two other reference lighthouses would also have to be set up by the same trial and error method. Having now a reference lighthouse arrangement for each set of phosphor dots, alignment apparatus 50 can be used to record in a microscopically accurate manner the alignment of collimator assembly 20, lens assembly 30, and panel support assembly 40 in the reference lighthouse arrangement in the manner described above. Oncethe alignment of the three constituent-assemblies in a reference lighthouse arrangement has been .recordediby'alignment apparatus 50, the apparatus "can be transferred to a panel support assembly 40 of a second lighthouse arrangement which has not yet been aligned and can be used as an aid in reproducing the reference alignment. Obviously, collimator assembly 20, lens assembly 30, and panel support assembly 40 in the second lighthouse arrangement must be very nearly identical in construction to the corresponding assemblies in the reference lighthouse arrangement, and reference marks 34 on lens holder 31 must be located in the same position relative to lens 34 as they were on the corresponding lens "holder in the reference lighthouse arrangementT hen, with flat plate 51 of alignment apparatus 50 indexed by panel cating blocks 42 on panel support assembly 40 of the second lighthouse arrangement, support table 41 can be manipulated on table 11 until, looking into microscope assembly 53, collimator tip 23 is accurately centered in the cross-hairs. Panel support table 41 can then be. secured on table 11 by drilling the holes 46 and 18 shown in FIG. 1 and inserting mounting pins 47 therein. This fixes panel support assembly 40 with respect to collimator assembly 20 in the same relative position as in the reference lighthouse arrangement. Lens holder 31 may then be moved around on plate 10 until the cross-hairs in microscope assemblies 52 and 54 are accurately centered on cross marks 34. Panel support assembly 30 is then in proper position with respect to both collimator assembly 20 and .panel support assembly 40 and can be fixed in that position by drilling the holes 36 and 17 shown in FIG. 1 and inserting lens holder pins 39 therein. It is obvious that this same alignment procedure, using alignment apparatus 50, can be utilized to align as many other corresponding lighthouse arrangements as are desired.

From the above description of an alignment apparatus in accordance with this invention it is apparent that such an alignment apparatus facilitates the microscopically accurate recording of the alignment of a reference lighthouse arrangement and the duplicating in an exact manner of the reference alignment in any number of corresponding lighthouse arrangements. The resulting set of lighthouse arrangements meets the requirement of interchangeability to a degree which could not be attained by any alignment procedure used in the past. Moreover, the use of an alignment apparatus constructed in accordance with this invention results in improved exposure of phosphor dot triads on mass produced picture tube face panels and, as a result, the overall quality of picture tubes which incorporate face panels exposed on lighthouse arrange merits which are aligned by using as an aid an alignment device constructed in accordance with this invention is enhanced.

Successful utilization of alignment apparatus 50 requires that collimator assembly 20, lens assembly 30, and panel support assembly 40, each have at least one reference point associated therewith. In the preferred embodiment described above panel support assembly 40 has, effectively, three associated reference points namely the three panel locating blocks, and the lens assembly has two associated reference points-cross marks 34. Collimator assembly 20 has only one reference point. The provision of more than one reference point for lens assembly 30 increases the accuracy of the alignment procedure, as does the provision of three reference points for panel support assembly 40. Various other ways of providing associated reference points for collimator assembly 20, lens assembly 30, and panel support assembly 40 would suggest themselves to those skilled in the art. Moreover, with a proper adaptation of microscope assemblies 52, 53, and 54, lighthouse alignment device 50 :ould also be used to record and reproduce the required 6 separations between collimator tip 23, lens 32 and support table 41.

It is to be understood that the foregoing description of a particular embodiment of this invention is given for the purpose of illustration and that numerous modifications could be made without departing from the spirit and scope of this invention as claimed in the following claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Apparatus for use as an aid in reproducing the alignment of a plurality of individual elements, each of said elements having at least one accurately positioned reference point associated therewith, said apparatus comprising: support means adapted to be fixed in a particular position with respect to one of said reference points associated with a predetermined one of said elements; and a "plurality of microscope means mounted on said support means operable to focus accurately on corresponding ones of said reference points associated with the others of said elements when said support means is in said particular position.

2. Apparatus as claimed in claim 1, wherein said plurality of microscope means comprises a number of individual microscope assemblies, said number being equal to the total number of said reference points to be focused 3. Apparatus as claimed in claim 2, wherein each of said microscope assemblies includes a lens having a reticle thereon, said microscope assemblies being positioned on said support means so that individual ones of said reticles are aligned to focus accurately on corresponding individual ones of said reference points when said support means is in said particular position, said apparatus thereby recording accurately the alignment of said elements.

4. Apparatus for use in conjunction with a reference picture tube lighthouse arrangement having a collimator assembly, a lens assembly, and a panel support assembly aligned in a predetermined manner, said collimator assembly and said lens assembly each having at least one accurately positioned reference point associated therewith, said apparatus comprising: support means adapted to be mounted in a particular position on said panel support assembly; and a plurality of microscope means mounted on said support means Operable to focus accurately on each of said reference points when said support means is mounted in said particular position on said panel support assembly, whereby said apparatus may be used to duplicate the alignment of said reference lighthouse arrangement in lighthouse arrangements having corresponding collimator, lens, and panel support assemblies.

5. Apparatus as claimed in claim 4, wherein said support means is a flat plate having a particular configuration simulating the dimensions of a picture tube panel; and said plurality of microscope means comprises a number of individual microscope assemblies, said number being equal to the total number of said reference points.

6. Apparatus as claimed in claim 5, wherein said fiat plate has a plurality of apertures therein, each of said microscope assemblies being mounted in an individual one of said apertures with the longitudinal axes of said microscope assemblies substantially perpendicular to the plane of said flat plate.

7. Apparatus as claimed in claim 6, wherein said apertures in said flat plate are sufficiently large to permit said microscope assemblies to be mounted in various positions therein.

8. Apparatus as claimed in claim 7, wherein each of said microscope assemblies includes a lens having a reticle thereon, said microscope assemblies being positioned within their associated apertures so that individual ones of said reticles are aligned to focus accurately on corresponding individual ones of said reference points when said flat plate is mounted in said particular position on said panel support assembly, said apparatus thereby re 3,498,722 7 8 cording accurately the alignment of said collimator, lens, OTHER REFERENCES and panel support assemblies in said reference lighthouse Fortune, October 1951,

arrangement.

References Cited RONALD L. WIBERT, Primary Examiner UNITED STATES A S 5 T. R. MOHR, Assistant Examiner 749,754 1/1904 Spear 1 US. Cl. X.R. 3,081,521 3/1963 Smart et al. 2925.19 350-31

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