US3752980A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus for measuring electroluminescent device parameters
Assignee: AT&T Inc
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Filing: 1972-05-30
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Granted: 1973-08-14
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Expires: 1992-05-30
Abstract
Abstract Apparatus and method for measuring output characteristics of an electroluminescent device as a function of the amplitude of an input current pulse. The pulse duty factor and pulse amplitude of the input current to the electroluminescent device are varied to maintain a constant time-averaged input current such that the magnitude of the time-averaged light output radiant flux is a function essentially only of the input current pulse amplitude.
Inventors
- 👤 R Dixon
- 👤 J Ralston
- 👤 W Rosenzweig
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 16:05
CPC Classifications
G; G01; G01R; G01R31/00; G01R31/26
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
107 words
In apparatus for measuring, at a plurality of input current amplitudes, output characteristics of an electroluminescent device comprising: means for applying successively a plurality of differing amplitude input current pulses to an electroluminescent device, and means for detecting the light output of the electroluminescent device; the improvement being: means included in the input current means for adjusting the amplitude of the input pulses and adjusting the duty cycle of the input pulses with respect to the amplitude thereof such that on a time-averaged basis the input current is constant; and means included in the detection means for providing a timeaveraged output current proportional to the light output.
Claim 2
Dependent Claim
107 words
In apparatus for measuring, at a plurality of input current amplitudes, output characteristics of an electroluminescent device comprising: means for applying successively a plurality of differing amplitude input current pulses to an electroluminescent device, and means for detecting the light output of the electroluminescent device; the improvement being: means included in the input current means for adjusting the amplitude of the input pulses and adjusting the duty cycle of the input pulses with respect to the amplitude thereof such that on a time-averaged basis the input current is constant; and means included in the detection means for providing a timeaveraged output current proportional to the light output.
Claim 3
Dependent Claim
26 words
Apparatus as recited in claim 1 wherein the means for adjusting the duty cycle comprises means for adjusting the repetition rate of the input current pulses.
Claim 4
Dependent Claim
71 words
Apparatus as recited in claim 1 wherein the means for providing the time-averaged output current comprises: a photodetecting device having a current output proportional to the light output of the electroluminescent device, a time-averaging circuit having an input and output node, the input node being connected to the output of the photodetector, and a voltage detector having an input node which is connected to the output node of the time-averaging circuit.
Claim 5
Dependent Claim
125 words
Apparatus as recited in claim 1 wherein the means for providing the input current pulses comprises: a first series circuit branch including a current source and a capacitor, a second series circuit, in parallel with the capacitor of the first circuit branch, comprising a resistor, the electroluminescent device and the output branch of a transistor, a triggered pulse generator for generating approximately rectangular output pulses and having an input and an output node, the output node being connected to the input branch of the transistor, an oscillator having an output node connected to the input node of the triggered pulse generator, and means for varying the frequency of the oscillator to vary the duty cycle and amplitude of the input current to the electroluminescent device.
Claim 6
Dependent Claim
45 words
Apparatus as recited in claim 4 wherein the means for varying the frequency of the oscillator comprises: a variable resistance connected within the oscillator to determine the frequency of oscillation, and means for varying only said variable resistance to vary the frequency of the oscillator.
Claim 7
Dependent Claim
90 words
In a method for measuring output characteristics of an electroluminescent device at a plurality oF input current amplitudes comprising applying successively a plurality of differing amplitude input current pulses to an electroluminescent device, and detecting the light output, the improvement being the steps of: adjusting the amplitude of the input pulses and adjusting the duty cycle of the input pulses with respect to the amplitude thereof such that on a time-averaged basis the input current is constant, and detecting the light output and generating a time-averaged output current proportional thereto.
Claim 8
Dependent Claim
90 words
In a method for measuring output characteristics of an electroluminescent device at a plurality oF input current amplitudes comprising applying successively a plurality of differing amplitude input current pulses to an electroluminescent device, and detecting the light output, the improvement being the steps of: adjusting the amplitude of the input pulses and adjusting the duty cycle of the input pulses with respect to the amplitude thereof such that on a time-averaged basis the input current is constant, and detecting the light output and generating a time-averaged output current proportional thereto.
Claim 9
Dependent Claim
26 words
A method as recited in claim 6 wherein the adjustment of the duty cycle is provided by adjusting the repetition rate of the input current pulses.
Claim 10
Dependent Claim
43 words
A method as recited in claim 6 wherein the time-averaged output current is provided by the steps of: directing the light output of the electroluminescent device upon a photodetecting device, and applying the current output of the photodetecting device to a time-averaging circuit.
Claim 11
Dependent Claim
109 words
A method as recited in claim 6 wherein the input current pulses are provided by: applying a current from a constant current source to a capacitor, deriving a current from the capacitor, applying the current from the capacitor to a series circuit comprising a resistor, the electroluminescent device and the output branch of a transistor, and applying to the input branch of the transistor the output of a triggered pulse generator adapted for generating approximately rectangular output pulses sufficient that in the presence of a pulse generator output pulse the transistor is saturated, and in the absence of said pulse generator output pulse the transistor does not conduct current.
Claim 12
Dependent Claim
54 words
A method as recited in claim 9 wherein the variation in duty cycle of the pulse generator pulse is provided by: applying the output of an oscillator to the input of the pulse generator; and varying the frequency of oscillation of the oscillator so that the duty cycle of the pulse generator varies accordingly.
Claim 13
Dependent Claim
61 words
A method as recited in claim 6 wherein the output characteristics are provided by: applying the time-averaged output current to a voltage detector, and calibrating the voltage detector for each output characteristic so that the indicated voltage corresponds to at least one of the following device output characteristics: quantum efficiency, output watts per input amperes, and output lumens per input amperes.
Claim 14
Dependent Claim
59 words
A method as recited in claim 11, wherein the calibration of the voltage detector to read an output characteristic is provided by: connecting an electroluminescent device of a known output charcteristic in place of the test electroluminescent device, and adjusting the output of the time-averaging circuit so that the voltage detector reads the value of the known output characteristic.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-08-13 | 1977-02-12 | 1977-08-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-08-13 | 1981-02-12 | 1981-08-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-08-13 | 1985-02-12 | 1985-08-14 | $7700.00 | Window Closed / Lapsed |