ULTRASTABLE CALIBRATED LIGHT SOURCE

• US 3,670,202 A
• Filed: 07/31/1970
• Issued: 06/13/1972
• Est. Priority Date: 07/31/1970
• Status: Expired due to Term

• Current Assignee: John E. Novotny, Michael F. Heidt, N/a,, Naranappa K. Shankar, Paine Thomas O Administrator of The National Aeronautics and Space
• Original Assignee: John E. Novotny, Michael F. Heidt, N/a,, Naranappa K. Shankar, Paine Thomas O Administrator of The National Aeronautics and Space
• Inventors: Shankar, Naranappa K., N/a,, Paine, Thomas O. Administrator of the National Aeronautics and Space, Heidt, Michael F., Novotny, John E.
• Primary Examiner(s): Kominski, John
• Application Number:
  US05/059,956
• Time in Patent Office: 683 Days
• Field of Search: 250/205 315/297,307,310,311,151,156,158 331/109,183
• US Class Current: 315/297
• CPC Class Codes: G01J 1/32 adapted for automatic variation of the measured or reference value regulation of light intensity G05D25/00
• CPC Class Codes: H05B 39/042 by measuring the incident light
• CPC Class Codes: H05B 39/081 by measuring the incident light H05B39/083 takes precedence
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

Light from an electrically powered light source is optically monitored by a transducer which converts the optical signal to an electrical error signal. The error signal is compared with a reference signal and a signal representing the difference between the reference and the error signals is generated. The difference signal is employed to control an electronic switching network which in turn regulates the electrical power input to the light source to maintain a constant light level at the optical monitor.

Claims

1. A system for producing a precisely calibrated energy output level and maintaining said output level for extended periods of time comprising:

radiant energy producing means for forming a detectable energy output;

power supply means connected with said energy producing means for supplying power to said energy producing means, said power supply means including rectifier means for converting alternating current to full wave rectified direct current power having amplitude fluctuations occurring at a frequency corresponding to the frequency of said alternating current power;

monitoring means for monitoring said detectable energy output and forming a first electrical signal representative of the value of said energy output;

ultrastable reference signal forming means for generating an ultrastable electrical reference signal;

comparing means for comparing said reference signal and said first electrical signal and forming a second electrical signal representing the difference between said reference signal and said first electrical signal;

control switching means operable by said second electrical signal to electrically connect or disconnect said power supply means and said light energy producing means to control the power supplied to said light energy producing means to control switching means comprising a silicon controlled rectifier for selectively conducting said full way rectified power to the radiant energy producing means and trigger circuit means to selectively trigger said silicon controlled rectifier into and out of the conduction state, said trigger circuit means comprising a unijunction transistor means and biasing circuit means for regulating conduction through said unijunction transistor means, said biasing circuit means including capacitive means for storing an electrical charge and a transistor switching means for regulating the leakage across said capacitive means and the charge storage by said capacitive means to regulate conduction through said unijunction transistor means;

means for phase locking said full wave rectified power and said unijunction transistor means, whereby said unijunction transistor means is rendered conductive during a portion of the power phase as controlled by said biasing circuit means to precisely regulate the amount of power supplied to said radiant energy producing means; and

filtering means for filtering the full wave rectified power conducted through said silicon controlled rectifier whereby a constant direct current voltage is delivered to said radiant energy producing means to maintain an ultrastable radiant energy output.

2. The system as defined in claim 1 wherein said ultrastable reference signal forming means includes a unity gain operational amplifier, a battery cell connected to the positive input terminal of the amplifier for applying a positive voltage thereto, and feedback means for coupling the output of the amplifier to the negative input terminal of the amplifier whereby an ultrastable electrical reference signal is generated.

3. The system as defined in claim 2 wherein said comparing means includes a second operational amplifier having a pair of input terminals with one input terminal coupled to the output of said first mentioned operational amplifier and the other input terminal coupled to said monitoring means to receive said first electrical signal rePresentative of the value of said radiant energy output.

4. The system as defined in claim 1 wherein said radiant energy producing means is a light producing means, said system further including light treating means included between said light energy producing means and said monitoring means for converting said optical output to processed light falling within a preselected wave length range;

collimator means exposed to said processed light for collimating said processed light; and

thermocouple means included with said monitoring means for converting said collimated light to an electrical signal.

5. The system as defined in claim 4 wherein said monitoring means is a photovoltaic device.

6. The system as defined in claim 1 wherein said switching means includes adjustable biasing means for adjusting the operating point of said transistor switching means whereby the energy value at which said energy producing means is to operate may be selectively determined.

7. The system as defined in claim 1 further including:

a. means for adjusting the value of said reference signal;

b. means for adjusting the output of said comparing means; and

c. means for altering the sensitivity of said control means.