Title:
ALPHA-NUMERIC DISPLAY PACKAGE
United States Patent 3786499


Abstract:
A package for displaying alpha-numeric characters using a plurality of discrete, light-emitting diodes, each diode providing a point source of light corresponding to one of the segments of the characters when electrically activated, including a substrate having the light-emitting diodes mounted upon it; a block of material adjacent the substrate containing a plurality of light pipes in the shape of the segments; and a composite fly's eye lens on top of the light pipes for displaying the selected character by the selective activation of the light-emitting diodes.



Inventors:
Jankowski, Alfred S. (San Jose, CA)
Moll, John L. (Stanford, CA)
Funk, Ernest J. (Cupertino, CA)
Application Number:
05/307280
Publication Date:
01/15/1974
Filing Date:
11/16/1972
Assignee:
FAIRCHILD CAMERA INSTRUMENT CORP,US
Primary Class:
Other Classes:
313/500, 313/512, 340/815.45, 340/815.54, 345/46
International Classes:
G09F9/33; H01L33/00; H05B33/02; H05B33/12; (IPC1-7): G08B5/36
Field of Search:
340/380,381,366R,378R 313
View Patent Images:
US Patent References:
3744048DISPLAY APPARATUS EMPLOYING FIBER OPTICS1973-07-03Treichel
3631478LIGHT GUIDE SUPPORT MEANS AND DISPLAY DEVICE UTILIZING SAME1971-12-28McNaney
3573814LIGHTED DISPLAY UNITS1971-04-06Lang
3570157N/A1971-03-16Ohlsson
3420949LIGHT GUIDE MESSAGE CHARACTER DISPLAY APPARATUS1969-01-07McNaney
3252158Character display device1966-05-17Naylor
0027003N/A1860-01-31



Primary Examiner:
Trafton, David L.
Attorney, Agent or Firm:
Borovoy, Roger Macpherson Alan S. H.
Claims:
We claim

1. A package for selectively displaying one of a plurality of alpha-numeric characters using a plurality of discrete, light-emitting diodes, each diode providing a point source of light corresponding to a segment of said characters when electrically activated, comprising:

2. The package of claim 1 further characterized by said block being plastic.

3. The package of claim 2 further characterized by the walls of said light pipes being covered with a reflective metal.

4. The package of claim 1 further characterized by the surface of said substrate adjacent said block having a non-reflective, insulating layer surrounding said light emitting diodes.

5. The package of claim 3 further characterized by said non-reflective coating being an insulating material.

6. The package of claim 1 further characterized by the segments of said characters being arranged in the shape of a composite digit.

7. The package of claim 6 further characterized by said composite digit including a decimal point.

8. The package of claim 1 further characterized by said second opposite face of said block having a non-reflective coating.

Description:
FIELD OF THE INVENTION

This invention is in the field of packages for solid state displays. More specifically, the packages of this invention are the form of hybrid circuits having a plurality of light-emitting diodes mounted on a base, along with a self-contained packaging system to display the emitted light in the form of an alpha-numeric character.

PRIOR ART

Packages used for displaying alpha-numeric characters from a plurality of light-emitting diodes mounted on a substrate are known in the art. These packages generally employ a plurality of translucent, plastic plugs in the shape desired for each segment of the alpha-numeric character. The light from an activated diode is passed through the plastic segment, lighting up the translucent material of the plastic and creating the luminescent display of that digit segment. Because of the translucent character of the plastic, no lensing system is required. The combination of all the lighted segments makes up the desired character. The primary difficulty with these prior art packages is the inefficiency of the transmission of the tiny amount of light from each light-emitting diode through the translucent plastic. Accordingly, a more efficient system had to be developed.

BRIEF DESCRIPTION OF THE INVENTION

This invention is a package for selectively displaying one of a plurality of alpha-numeric characters using a plurality of discrete, light-emitting diodes, each diode providing a point source of light corresponding to a segment of the characters when electrically activated. The invention includes a substrate having arranged laterally thereupon a plurality of light-emitting diodes in the general shape of the necessary segments of all the alpha-numeric characters to be displayed; a single block of material adjacent to the substrate having two opposed parallel faces, the first face lying adjacent to the substrate; a plurality of light pipes in the shape of the character segments extending completely through the block from the first face to the opposite one, a different one of the light pipes being aligned with a corresponding one of the diodes, the walls of each light pipe being reflective, whereby the light emitted from each electrically activated diode is passed through its corresponding light pipe; and a composite lens covering the second opposite face of the block, the lens comprising a plurality of fly's eye lenses in close proximity with each other, the composite lens at least covering the ends of all the light pipes where they extend to the second opposite face, whereby the light from each electrically activated light-emitting diode is passed through its corresponding light pipe and then through the composite lens, thereby optically displaying on the lens all the segments of the alpha-numeric characters selected by the electrical activation of one or a plurality of the light-emitting diodes.

While light pipes have been used in the past for light transmission of bright incandescent lamps, a system has not been found for using light pipes with sufficient light transmission efficiency for the tiny amount of emitted light from a light-emitting diode. In this invention, it was unexpectedly found that the combination of a light pipe having reflective walls and which is covered at the display end of the pipe with a fly's eye lens provides a very efficient means of displaying light from these tiny, light-emitting diodes. This unique combination of the invention provides a vast improvement over the prior art light-emitting diode packages using translucent plastic. Moreover, it is inexpensive and simple to mass produce.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of the substrate of the invention;

FIG. 2 is a top view of the block which contains the light pipes of the invention;

FIG. 3 is an end, interior view (with the end of the package removed) of the package of the invention; and

FIG. 4 is a cross-sectional view through the lines 4--4 of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, and in particular to FIG. 1, each of the light-emitting diodes 11, 12, 13, 14, 15, 16 and 17 are mounted with their light-emitting side up on a conductive metal plate 18. These diodes are arranged laterally upon the substrate in the general shape of the necessary segments of all the alpha-numeric characters to be displayed. In the selected embodiment of the invention, diodes 11, 12, 14, 15, 16 and 17 are arranged to correspond with the segments of a figure eight (as shown in FIG. 2). As is well known in the art, a seven-segment figure eight, by the selective activation of two or more diodes, is sufficient to display all of the digits zero through nine. Diode 13 is used to display the decimal point. This segment arrangement is conventional in the art, and needs no further explanation here.

The first electrical connection to each diode is a common connection which results from the soldering of each diode to the common metal plate 18 on substrate 10, as shown in FIG. 1. The other electrical connection is a separate connection for each diode (for selective electrical activation) in the form of a wire 19 from the top surface of each diode to a conductive post 20. Posts 20 extend, as shown in FIG. 3, out from the bottom of the package for plug-in electrical connection to a conventional printed circuit board. Preferably, the surface of the metal plate 18 is covered, surrounding the diodes, with an opaque, insulating layer, such as black paper, to prevent shorting of wires 19 against the metal. The opaqueness prevents unwanted light reflections.

The single block of material containing the light pipes of this invention is shown in FIGS. 2 and 4. Block 21, preferably made of plastic, has a first lower face 22 which is located adjacent to the top surface of substrate 10 atop the light-emitting diodes, as shown in FIG. 3. Block 21 has a second opposed parallel face 23, shown in FIG. 2, upon which the light passing through light pipes 24 is displayed. Block 21 contains a plurality of light pipes 24 in the shape of the desired character segments. Referring to FIGS. 2 and 4, these segments extend completely through block 21 from the first face 22 to the opposite face 23. A different one of the light pipes 24 is aligned with each of the light-emitting diodes 11-17 shown in FIG. 1. The interior walls of each light pipe 24 are reflective. This reflectivity is preferably achieved by coating the interior walls of each light pipe with a reflective material, preferably a reflective metal such as gold. Although gold is expensive, it is one of the most highly reflective metals available. With the construction of block 21 shown in FIGS. 2 and 4, the light emitted from each electrically activated diode is efficiently passed through its corresponding light pipe 24 and displayed as a lighted segment on surface 23 of block 21. For optimum efficiency, it has been found advantageous to coat the surface 23 with a non-reflective coating surrounding the exposed segments 24.

However, without the lens cap 25 shown in FIG. 3, the amount of light displayed at the surface 23 of block 21 does not appear as individual segments, but as a "hot spot" in the center of each light pipe. Accordingly, a composite lens cap 25 is employed covering the second face 23 of block 21. This lens cap comprises a plurality of fly's eye lenses 26 in close proximity with each other. The effect of the lens cap is to spread out the displayed light so that the segments are entirely illuminated. The composite lens 25 at least covers the ends of light pipes 24 where they extend to the second face 23 as shown in FIG. 2. In other words, lens cap 25 must contain a sufficient area of fly's eye lenses 24 to at least cover the entire figure eight and the decimal point 27 shown in FIG. 2. In the embodiment of the invention shown, the fly's eye lenses 26 are directly molded into cap 25 which is made of translucent plastic. The plastic material can be white, red, clear, frosted, or any color desired in the application of the display. Lens cap 25 fits tightly over the sides of substrate 10 as shown in FIG. 3, to form a complete enclosure.

The light from each electrically activated light-emitting diode 11-17 shown in FIG. 1, is passed through its corresponding light pipe 24, shown in FIGS. 2 and 4, and then through the composite lens 25, shown in FIG. 3, thereby optically displaying on the lens cap 25 all the segments of the alpha-numeric character selected by the electrical activation of one or a plurality of light-emitting diodes. For example, if all of the light-emitting diodes 11-17 are electrically activated, all of the segments 24 shown in FIG. 2 and the decimal point 27 will be lighted, displaying the figure "eight" followed by a decimal point. If all the diodes except diodes 11 and 12, corresponding to the two lower left ones of segments 24 in FIG. 2 (one vertical and one horizontal) are lighted, the character displayed will be a figure nine followed by a decimal point. Obviously, if diode 13 (FIG. 1) is not activated, the decimal point 27 (FIG. 2) will not be displayed.

Obviously the invention is applicable to the display of characters denoting letters of the alphabet, numbers, Chinese or Japanese characters, or any other lateral configuration of segments 24 (and corresponding lateral arrangement of the light-emitting diodes on the substrate 10), using the proper selective activation of the diodes to activate the designated character for display. These techniques are well known in the art.