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Publication numberUS3719849 A
Publication typeGrant
Publication dateMar 6, 1973
Filing dateSep 24, 1971
Priority dateSep 24, 1971
Also published asDE2243357A1
Publication numberUS 3719849 A, US 3719849A, US-A-3719849, US3719849 A, US3719849A
InventorsR Steward
Original AssigneeHewlett Packard Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Solid state displays
US 3719849 A
Abstract  available in
Images(1)
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Claims  available in
Description  (OCR text may contain errors)

United States Patent [191 Steward [4 1 March 6, 1973 SOLID STATE DISPLAYS [75] Inventor: Robert L. Steward, San Jose, Calif.

[73] Assignee: Hewlett-Packard Company, Palo Alto,Calif.

[58] Field of Search ..313/l09.5, I08 D; 340/324, 340/336, 343; 235/643, 60.15; 315/169 [56] References Cited UNITED STATES PATENTS 3,573,532 4/1971 Boucher ..3l5/l69 Light Emitting Segments 9 Decimal Point Light Emitting Material 3/1970 Lake eta] ..3l5/l09.5 4/1972 Kegelman ..3l3/l09.5

Primary ExaminerJohn Kominski Attorney-A. C. Smith [57] ABSTRACT A decimal point element is located within the boundaries of the charaCter element on a monolithic solid state character chip. When a character string is displayed, only the decimal point is energized on one character chip. This results in wide separation between the decimal point and its nearby characters Hence readability of the decimal point in improved in long character strings.

2 Claims, 6 Drawing Figures Substrate Diffused Regions ll PATENTED 61915 3.719.849

Diffused Region Contact i r J A T Light Emitting Substrate R Material 1 3 7 Contact igure 1 4 Light Emitting Segments 9 Decimal Point 5 Light Emitting w Material igure 2 i9ure 4 iure3 INVENTOR ROBERT L. STEWARD SOLID STATE DISPLAYS BACKGROUND AND SUMMARY OF THE INVENTION The readability of a decimal point in a string of characters depends on the relative position of the decimal point to its nearby characters. In long character strings, for example, it may be difficult to quickly determine the exact location of the decimal point because it blends into the character string and becomes lost in the maze of characters. To remedy this, a decimal point is usually displayed well below the lowest portion of the characters. This distance below the character is often onefifth the character height.

Positioning the decimal point below the characters sometimes increases the manufacturing cost of a display. If a character is formed from a single piece or chip of material, as in monolithic displays, either the chip size must be increased to accommodate both the character and the decimal point, or a special process must be used to provide a separate smaller decimal point chip. Either method increases the product cost.

The present invention locates the decimal point in the lower half of the character font. When a character string is displayed, one character position is dedicated to the decimal point. Thus, readability of long character strings is improved because the decimal point is well separated from its nearby characters.

The solid state displays using the monolithic process, this invention locates both a character and a decimal point in some or all of the display chips. When a character string is displayed, either the decimal point or a selected character is energized in each chip. Thus the same size chip is used to display a character or a decimal point. This eliminates the extra process needed to make a special decimal point chip. Since the decimal point is located within the character boundaries in a chip, a larger chip is not needed to accommodate the decimal point. As a result of this invention, the product cost of solid state displays for medium to long character strings can be decreased.

DESCRIPTION OF THE DRAWINGS FIG. 1 shows a side view of a light-emitting diode made according to the art.

FIGS. 2 and 3 show conventional methods of incorporating a decimal point in monolithic displays.

FIG. 4 shows a perspective view of an improved monolithic character chip made according to the preferred embodiment of this invention.

FIG. 5 shows a character string using conventional decimal point placement.

FIG. 6 shows the same character string as shown in FIG. 5, but with the improved decimal point placement of this invention instead of the conventional placement.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a light-emitting diode, wellknown in the art, is made from a material that emits photons when minority and majority carriers recombine. Such a material is gallium arsenide phosphide. To make a light-emitting diode, an n-type alloy of gallium arsenide phosphide 7 is grown epitaxially on a gallium arsenide sustrate 3. A p region 5 is then created by diffusing a charged material, such as p-type zinc, into the chip. This region is capped with a metal contact 1. The contact provides the anode terminal for the diode while the substrate contact 4 acts as the cathode terminal.

When a forward bias is applied to the diode, the potential barrier at the p-n junction is reduced so current can flow. Just as in the operation of a standard diode, electrons are injected into the p region and holes are injected into the n region. However, when these minority carriers recombine with the majority carriers, energy is given off as photons. Some of these photons are emitted from the surface of the doped gallium arsenide phosphide. Thus the diode emits light in response to forward bias voltage.

The light-emitting regions can be selectively arranged in a monolithic chip by the positioning of the diffused p regions. In this manner, chips can be constructed to provide numeric and alphanumeric displays. To provide a numeric display chip, a plurality of light-emitting regions are sometimes arranged in the shape of a rectangular or rhomboidal figure eight. (See FIGS. 2-6.) By forward biasing only selected regions, any digit from 0 to 9 can be displayed. This type of display is commonly called a seven-segment font because the figure eight is usually made by seven linear regions. Sometimes small dot-like light-emitting regions are aligned to form the seven segment font.

A problem with this type of font is decimal point location. To maintain readability of a decimal point in a string of characters, the decimal point is often located below the bottom of the character string. In conventional monolithic displays, either the chip size must be increased to accommodate both the character and the decimal point, as shown in FIG. 2, or a separate smaller chip must be made for the decimal point, FIG. 3. Either process increases the cost of a display.

Referring now to FIG. 4, eight diffused regions 11 are positioned to form a seven-segment display and a decimal point. The decimal point is located within the lower half of the character font to keep the chip the same size as a conventional seven-segment display chip without a decimal point. Since the decimal point is contained in the character chip, no additional process is needed to manufacture a special decimal point chip.

This improved decimal point placement improves I the readability of long character strings. As shown in FIG. 5, the readability of a decimal point in a character string using conventional decimal point positioning depends primarily on the vertical separation between the decimal point and the character string. In the improved positioning, as shown in FIG. 6, the readability is increased by greater horizontal spacing between the decimal point and its nearby characters. One character position is dedicated to the decimal point in a string of characters. This invention does require an extra character position to display the decimal point, but the cost of this extra position is less than the extra chip area or assembly time required by conventional displays when used in displays of more than seven characters.

I claim: 1. Visual display apparatus comprising: a plurality of numeric display means disposed in lineal array to display a plurality of adjacent digits; the display means being substantially similar and each including regions which emit light in response to applied excitation and which are arranged in a seven-segment font; and

in each of said display means, an additional region which emits light in response to applied excitation when excited in lieu of a digit in the digit place occupied by the associated display means.

2. A display chip as in claim 1 wherein the decimal point is located within the lower area of the font and which is located within the periphery of the bounded y Said regions-

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4019196 *Oct 24, 1975Apr 19, 1977Stanley Electric Co., Ltd.Indicating element and method of manufacturing same
US4092638 *Mar 11, 1977May 30, 1978Textron Inc.Display device employing special purpose monograms
US4163230 *Jun 27, 1977Jul 31, 1979Citizen Watch Co. Ltd.Display device for electronic timepieces
US4165474 *Dec 27, 1977Aug 21, 1979Texas Instruments IncorporatedOptoelectronic displays using uniformly spaced arrays of semi-sphere light-emitting diodes
US4176318 *Mar 28, 1977Nov 27, 1979Motorola, Inc.Radio transmitter display indicator
US4227201 *Jan 22, 1979Oct 7, 1980Hughes Aircraft CompanyCCD Readout structure for display applications
US5003298 *Jul 14, 1989Mar 26, 1991Karel HavelVariable color digital display for emphasizing position of decimal point
US6119073 *Jun 17, 1999Sep 12, 2000Texas Digital Systems, Inc.Variable color digital measuring instrument for sequentially exhibiting measured values
US6121944 *Jun 8, 1998Sep 19, 2000Texas Digital Systems, Inc.Method of indicating and evaluating measured value
US6147483 *Jun 18, 1999Nov 14, 2000Texas Digital Systems, Inc.Variable color digital voltmeter with analog comparator
US6166710 *Jun 18, 1999Dec 26, 2000Texas Digital Systems, Inc.Variable color display system for sequentially exhibiting digital values
US6208322Apr 23, 1998Mar 27, 2001Texas Digital Systems, Inc.Color control signal converter
US6219014Aug 18, 1998Apr 17, 2001Texas Digital Systems, Inc.Variable color display device having display area and background area
US6239776May 5, 1998May 29, 2001Texas Digital Systems, Inc.Multicolor multi-element display system
US6281864Mar 15, 1999Aug 28, 2001Texas Digital Systems, Inc.Digital display system for variable color decimal point indication
US6300923Jul 6, 1998Oct 9, 2001Texas Digital Systems, Inc.Continuously variable color optical device
US6310590Aug 11, 1999Oct 30, 2001Texas Digital Systems, Inc.Method for continuously controlling color of display device
US6414662Oct 12, 1999Jul 2, 2002Texas Digital Systems, Inc.Variable color complementary display device using anti-parallel light emitting diodes
US6424327Aug 11, 1999Jul 23, 2002Texas Digital Systems, Inc.Multicolor display element with enable input
US6535186Mar 16, 1998Mar 18, 2003Texas Digital Systems, Inc.Multicolor display element
US6577287Feb 20, 2001Jun 10, 2003Texas Digital Systems, Inc.Dual variable color display device
US6690343Mar 20, 2001Feb 10, 2004Texas Digital Systems, Inc.Display device with variable color background for evaluating displayed value
US6734837Jun 16, 1999May 11, 2004Texas Digital Systems, Inc.Variable color display system for comparing exhibited value with limit
USRE30556 *Jan 26, 1979Mar 24, 1981Stanley Electric Co., Ltd.Indicating element and method of manufacturing same
Classifications
U.S. Classification313/500, 345/34, 257/92
International ClassificationG09F9/33, H01L27/15, H01L33/00
Cooperative ClassificationH01L33/00, G09F9/33, H01L27/15
European ClassificationG09F9/33, H01L33/00, H01L27/15