Radiant energy analyzer feedback system

Claim 2

A radiant energy analyzer system comprising: a radiant energy detector having a bias electrode and a signal electrode, said radiant energy detector generating an electrical signal at said signal electrode in response to incident radiant energy; selective detector means having an input terminal and at least one output terminal, said input terminal being connected to said signal electrode of said radiant energy detector, said selective detector means generating an output electrical signal having a magnitude proportional to the amplitude of selected segments of the electrical signal from said radiant energy detector; oscillator means for generating an alternating signal having an amplitude inversely proportional to the magnitude of the output signal from said selective detector means, said oscillator means having a pair of output terminals between which the alternating signal is generated and an input control terminal connected to the output terminal of said selective detector means; rectifier means having a pair of input terminals connected to said pair of output terminals of said oscillator means and having an output terminal connected to said bias electrode of said radiant energy detector, said rectifier means producing a varying output DC bias having a magnitude proportional to the amplitude of the alternating signal from said oscillator means; and an overload circuit connected between the input terminal of said selective detector means and the input terminal of said oscillator means, said overload circuit providing a conducting path between the input terminals of said selective detector means and said oscillator means when the amplitude of the electrical signal at the input terminal of said selective detector means exceeds a predetermined threshold and said overload circuit providing a nonconducting path when the amplitude of the electrical signal is less than said predetermined threshold.

Claim 3

The radiant energy analyzer defined in claim 1 wherein said overload circuit comprises: a first resistor connected to the input terminal of said selective detector means; a second resistor connected to said first resistor for supplying a predetermined threshold voltage to the junction of said first and second resistors from a voltage applied to the other end of said second resistor; and a diode having an anode connected to the junction of said first and second resistors and a cathode connected to the input terminal of said oscillator means, said diode being normally biased nonconducting by the threshold voltage and rendered conducting by the magnitude of the electrical signal at the input to the selective detector exceeding the threshold voltage.

Claim 4

The radiant energy analyzer defined in claim 1 wherein said oscillator means comprises: a transformer having input, feedback, and output windings, the output windings being connected to said rectifier means and the input winding having a center tap connected to the selective detector means output terminal; and a pair of transistors having electrodes connected to the feedback and input windings of said transformer to form a free running multivibrator.

Claim 5

The radiant energy analyzer defined in claim 3 wherein said rectifier means comprises: at least one rectifier diode connected to the output winding of said transformer; and a resistance-capacitance network means having input and output terminals, the input terminals being connected to said diode and the output terminal being connected to the bias electrode of said radiant energy detector means, said resistance-capacitance network means transmitting only a slowly varying DC bias from the input to output terminals thereof.

Claim 6

The radiant energy analyzer defined in claim 4 further comprising a time constant compensation circuit connected between the output terminal of said selective detector means and the input terminal of said oscillator means for generating a first time constant in response to an increasing electrical signal from said selective detector means and generating a second time constant in response to a decreasing output electrical signal from said selective detector means, the first time constant being different from the second time constant whereby compensation is obtained for respective time constants inherent in said rectifier means.

Claim 7

The radiant energy analyzer defined in claim 5 wherein said time constant compensation circuit comprises; a resistor connected between the output terminal of said selective detector means and the input terminal of said oscillator means; a diode connected in parallel with said resistor and having its cathode connected to the input terminal of said oscillator means; and a capacitor connected from the input terminal of said oscillator means to an electrical ground.

Claim 8

In a radiant energy analyzer of the type having reference and sample beam paths and means for directing radiant energy passing said reference and sample beam paths alternately along a single beam path, the improvement comprising: detector means positioned to receive radiation passing said single beam path; variable bias means connected to said detector means, said detector generating an electrical output signal proportional to the instantaneous incident radiation and the magnitude of the biased on said detector; feedback means connected between the output of said detector means and said variable bias means, said feedback means including means for selecting the portion of said electrical output signal proportional to the energy in said reference beam path and controlling said variable bias means to maintain said portion of said electrical output signal substantially constant; overload protection means connected between the output of said detector means and saiD feedback means and bypassing at least a portion of said feedback means for reducing said bias on said detector means when the output of said detector means exceeds a predetermined value.

Claim 9

In a radiant energy analyzer of the type having reference and sample beam paths and means for directing radiant energy passing said reference and sample beam paths alternately along a single beam path, the improvement comprising: detector means positioned to receive radiation passing said single beam path; variable bias means connected to said detector means, said detector generating an electrical output signal proportional to the instantaneous incident radiation and the magnitude of the biased on said detector; feedback means connected between the output of said detector means and said variable bias means, said feedback means including means for selecting the portion of said electrical output signal proportional to the energy in said reference beam path and controlling said variable bias means to maintain said portion of said electrical output signal substantially constant; overload protection means connected between the output of said detector means and saiD feedback means and bypassing at least a portion of said feedback means for reducing said bias on said detector means when the output of said detector means exceeds a predetermined value.

Claim 10

In a radiant energy analyzer having a reference channel and a feedback loop wherein a voltage signal from the reference channel controls the magnitude of an electrical bias to a radiant energy detector, the improvement comprising; a voltage-controlled bias supply having an input voltage control terminal and an output bias terminal, said voltage controlled bias supply being included within the feedback loop, the output bias terminal of said voltage-controlled bias supply being connected to the radiant energy detector to provide an electrical bias thereto, said voltage bias supply inherently having a first time constant in response to an increasing voltage applied to the control terminal thereof and a second time constant in response to a decreasing voltage applied to the control terminal where the first and second time constants are different; a time constant compensating circuit connected within the feedback loop for compensating the difference between the first and second time constants of said voltage-controlled bias supply; and an overload protection circuit connected between the radiant energy detector and the control terminal of said bias supply for establishing an electrical conducting and nonconducting path between the radiant energy detector respectively exceed and falls below a predetermined threshold value.

Claim 11

In a radiant energy analyzer having a reference channel and a feedback loop wherein a voltage signal from the reference channel controls the magnitude of an electrical bias to a radiant energy detector, the improvement comprising; a voltage-controlled bias supply having an input voltage control terminal and an output bias terminal, said voltage controlled bias supply being included within the feedback loop, the output bias terminal of said voltage-controlled bias supply being connected to the radiant energy detector to provide an electrical bias thereto, said voltage bias supply inherently having a first time constant in response to an increasing voltage applied to the control terminal thereof and a second time constant in response to a decreasing voltage applied to the control terminal where the first and second time constants are different; a time constant compensating circuit connected within the feedback loop for compensating the difference between the first and second time constants of said voltage-controlled bias supply; and an overload protection circuit connected between the radiant energy detector and the control terminal of said bias supply for establishing an electrical conducting and nonconducting path between the radiant energy detector respectively exceed and falls below a predetermined threshold value.

Claim 12

The radiant energy analyzer defined in claim 8 wherein said compensation circuit comprises: a resistor connected in series with the feedback loop; a diode connected in parallel with said resistor; a capacitor connected to said resistor in a manner to form a low-pass filter therewith. 10 The radiant energy analyzer defined in claim 8 wherein said overload protection circuit comprises: a pair of resistors connected in series one end of which is connected to the radiant energy detector, the other end having a threshold voltage applied thereto; a diode having its cathode connected to the control terminal of said bias supply and its anode connected to the junction of said pair of resistors.

Claim 13

A radiant energy analyzer comprising: a photomultiplier having a bias electrode and a signal electrode, said photomultiplier generating an electrical signal at the signal electrode in response to incident radiant energy; amplifier means having an input terminal connected to said signal electrode of said photomultiplier and an output terminal, said amplifier means amplifying the electrical signal from said photomultiplier; a series resistor pair having one end connected to the output of said amplifier means and the other end having a predetermined threshold voltage applied thereto; a first diode having its anode connected to the junction of said series resistor pair; selective detector means having an input terminal and at least a first output terminal, said input terminal being connected to said amplifier means output terminal, said selective detector generating a signal at said first output terminal having a magnitude proportional to selected segments of the electrical signal from said photomultiplier; a resistor having one end connected to the first output terminal of said selective detector and the other end connected to the cathode of said first diode; a second diode connected in parallel with said resistor, the anode end of which is connected to the one end of said resistor; a capacitor connected between the junction of the other end of said resistor and the cathodes of said first and second diodes and a circuit ground; oscillator means for generating an alternating signal having an amplitude inversely proportional to the magnitude of a voltage appearing across said capacitor, said oscillator means having an input terminal connected to the junction of said capacitor and said resistor and a paIr of output terminals between which the alternating signal is generated; and rectifier means having a pair of input terminals connected to the pair of output terminals of said oscillator means and having an output terminal connected to the bias electrode of said photomultiplier, said rectifier means producing a varying output DC bias having a magnitude proportional to the amplitude of the alternating signal from said oscillator means.

Claim 14

A radiant energy analyzer comprising: a photomultiplier having a bias electrode and a signal electrode, said photomultiplier generating an electrical signal at the signal electrode in response to incident radiant energy; amplifier means having an input terminal connected to said signal electrode of said photomultiplier and an output terminal, said amplifier means amplifying the electrical signal from said photomultiplier; a series resistor pair having one end connected to the output of said amplifier means and the other end having a predetermined threshold voltage applied thereto; a first diode having its anode connected to the junction of said series resistor pair; selective detector means having an input terminal and at least a first output terminal, said input terminal being connected to said amplifier means output terminal, said selective detector generating a signal at said first output terminal having a magnitude proportional to selected segments of the electrical signal from said photomultiplier; a resistor having one end connected to the first output terminal of said selective detector and the other end connected to the cathode of said first diode; a second diode connected in parallel with said resistor, the anode end of which is connected to the one end of said resistor; a capacitor connected between the junction of the other end of said resistor and the cathodes of said first and second diodes and a circuit ground; oscillator means for generating an alternating signal having an amplitude inversely proportional to the magnitude of a voltage appearing across said capacitor, said oscillator means having an input terminal connected to the junction of said capacitor and said resistor and a paIr of output terminals between which the alternating signal is generated; and rectifier means having a pair of input terminals connected to the pair of output terminals of said oscillator means and having an output terminal connected to the bias electrode of said photomultiplier, said rectifier means producing a varying output DC bias having a magnitude proportional to the amplitude of the alternating signal from said oscillator means.

Claim 15

In a radiant energy analyzer of the type having an electrically controlled variable bias supply for supplying electrical bias to a radiant energy detector, the improvement comprising a threshold device having an input connected to receive an electrical signal from the radiant energy detector and having an output connected to the variable bias supply at which output an overload signal is generated in response to the electrical signal from the radiant energy detector exceeding a predetermined threshold, the electrical bias being controlled by the overload signal in a manner to reduce and maintain the magnitude of the electrical signal from the radiant energy detector essentially at the predetermined threshold level.

Claim 16

In a radiant energy analyzer of the type having an electrically controlled variable bias supply for supplying electrical bias to a radiant energy detector, the improvement comprising a threshold device having an input connected to receive an electrical signal from the radiant energy detector and having an output connected to the variable bias supply at which output an overload signal is generated in response to the electrical signal from the radiant energy detector exceeding a predetermined threshold, the electrical bias being controlled by the overload signal in a manner to reduce and maintain the magnitude of the electrical signal from the radiant energy detector essentially at the predetermined threshold level.

Claim 17

In a radiant energy analyzer having an electrically controlled variable bias supply for supplying electrical bias to a radiant energy detector, the improvement comprising: a series pair of resistors having an electrical signal from the radiant energy detector applied to one end and a predetermined threshold voltage applied to the other end thereof; and a diode connected between the junction of said series pair of resistors and the electrically controlled variable bias supply, said diode being conducting when the amplitude of the electrical signal from the radiant energy detector is less than a value proportional to the magnitude of the predetermined threshold voltage and conducting when the amplitude of the electrical signal exceeds the value proportional to the magnitude of the threshold voltage for applying a control signal to the variable bias supply to reduce the magnitude of bias in response to overload of the radiant energy detector.

Claim 18

In a radiant energy analyzer having an electrically controlled variable bias supply for supplying electrical bias to a radiant energy detector, the improvement comprising: a series pair of resistors having an electrical signal from the radiant energy detector applied to one end and a predetermined threshold voltage applied to the other end thereof; and a diode connected between the junction of said series pair of resistors and the electrically controlled variable bias supply, said diode being conducting when the amplitude of the electrical signal from the radiant energy detector is less than a value proportional to the magnitude of the predetermined threshold voltage and conducting when the amplitude of the electrical signal exceeds the value proportional to the magnitude of the threshold voltage for applying a control signal to the variable bias supply to reduce the magnitude of bias in response to overload of the radiant energy detector.