Electrical system for use in optical densitometry

Claim 2

An electrical system for use in optical densitometry, said system having means for detecting incident light transmitted through or reflected from a specimen, and an electrical indicator for indicating the magnitude of said incident light, Means for converting said incident light to an electrical input signal of a given polarity, a summing network adapted to produce a resultant signal for amplification, said network including means for combining said input signal and a signal having an opposite polarity and a fixed intensity greater than that of said input signal, means for amplifying said resultant signal, and means for feeding said amplified resultant signal to said electrical indicator for display thereon of a reading which is inversely proportional to the intensity of said incident light.

Claim 3

An electrical system for use in optical densitometry and adapted to provide, on a single associated instrument, readings indicative of plural optical characteristics of specimens exposed to light and having light transmitted through or reflected from said specimens for detection and measurement, said system including a photometer for detecting incident light and for convering said incident light to an input electrical signal, the magnitude of said input electrical signal emitted from said photometer being proportional to both the intensity of said incident light and to a biasing potential applied to said photometer, a first amplifier having a first input terminal for receiving signals of a first polarity and a second input terminal for receiving signals of a second and opposite polarity, and providing at an output terminal amplified signals of said second polarity; means for controlling said photometer biasing potential, a source of unidirectional current of said first polarity, plural position selector means adapted to provide selected conductive paths through the elements of said system, said selector means being adapted, in a first position thereof, to provide an operative connection between said photometer and said second amplifier terminal for feeding said input signal to said second terminal and between the output of said amplifier and said instrument, whereby said instrument will display a reading directly proportional to the intensity of incident light received by said photometer, said selector means being adapted, in a second position thereof, to provide an operative connection between said photometer and said first amplifier terminal, between said means for supplying said unidirectional current and said first terminal and between said amplifier output and said instrument, whereby said instrument will display a reading which is inversely proportional to the intensity of light incident upon said photometer, and said selector means being adapted, in a third position thereof, to provide an operative connection between said photometer and said first amplifier terminal, between said means for supplying said unidirectional current and said first terminal, between said amplifier output and said instrument, and between said amplifier output and said means for controlling said photometer biasing potential, whereby said instrument will provide a reading which is inversely proportional to the logarithm of the intensity of the light incident upon said photometer.

Claim 4

An electrical system for use in optical densitometry and adapted to provide, on a single associated instrument, readings indicative of plural optical characteristics of specimens exposed to light and having light transmitted through or reflected from said specimens for detection and measurement, said system including a photometer for detecting incident light and for convering said incident light to an input electrical signal, the magnitude of said input electrical signal emitted from said photometer being proportional to both the intensity of said incident light and to a biasing potential applied to said photometer, a first amplifier having a first input terminal for receiving signals of a first polarity and a second input terminal for receiving signals of a second and opposite polarity, and providing at an output terminal amplified signals of said second polarity; means for controlling said photometer biasing potential, a source of unidirectional current of said first polarity, plural position selector means adapted to provide selected conductive paths through the elements of said system, said selector means being adapted, in a first position thereof, to provide an operative connection between said photometer and said second amplifier terminal for feeding said input signal to said second terminal and between the output of said amplifier and said instrument, whereby said instrument will display a reading directly proportional to the intensity of incident light received by said photometer, said selector means being adapted, in a second position thereof, to provide an operative connection between said photometer and said first amplifier terminal, between said means for supplying said unidirectional current and said first terminal and between said amplifier output and said instrument, whereby said instrument will display a reading which is inversely proportional to the intensity of light incident upon said photometer, and said selector means being adapted, in a third position thereof, to provide an operative connection between said photometer and said first amplifier terminal, between said means for supplying said unidirectional current and said first terminal, between said amplifier output and said instrument, and between said amplifier output and said means for controlling said photometer biasing potential, whereby said instrument will provide a reading which is inversely proportional to the logarithm of the intensity of the light incident upon said photometer.

Claim 5

A system as defined in claim 2 which further includes an impedance connected between said output terminal and said first input terminal, said impedance forming in conjunction with the impedance of said unidirectional current source a feedback loop for said amplifier.

Claim 6

An optical densitometry system including an electrical circuit adapted to produce for application to an associated electrical indicating instrument of the type directly responsive to the magnitude of an applied signal an output signal having a magnitude which is substantially inversely proportional to the magnitude of an input signal received by a portion of said system from an associated photometer, said system including an amplifier having an input terminal for receiving a signal of predetermined polarity, and an output terminal, and means for feeding the amplified output signal from said output terminal of said amplifier to said electrical indicating instrument, and means for feeding a sigNal of said predetermined polarity and of a predeterminable, variable magnitude to said input terminal, and means adapted to receive from said associated photometer an input signal of an opposite polarity to said predetermined polarity and of a magnitude which is directly proportional to the intensity of the incident light on said associated photometer, said magnitude being lesser than said predeterminable, variable magnitude, whereby said input terminal will receive a signal having a magnitude equal to the difference between said predeterminable, variable magnitude and said lesser magnitude, and whereby said output signal from said amplifier will bear an inversely proportional relation to the intensity of said input signal.

Claim 7

An optical densitometry system including an electrical circuit adapted to produce for application to an associated electrical indicating instrument of the type directly responsive to the magnitude of an applied signal an output signal having a magnitude which is substantially inversely proportional to the magnitude of an input signal received by a portion of said system from an associated photometer, said system including an amplifier having an input terminal for receiving a signal of predetermined polarity, and an output terminal, and means for feeding the amplified output signal from said output terminal of said amplifier to said electrical indicating instrument, and means for feeding a sigNal of said predetermined polarity and of a predeterminable, variable magnitude to said input terminal, and means adapted to receive from said associated photometer an input signal of an opposite polarity to said predetermined polarity and of a magnitude which is directly proportional to the intensity of the incident light on said associated photometer, said magnitude being lesser than said predeterminable, variable magnitude, whereby said input terminal will receive a signal having a magnitude equal to the difference between said predeterminable, variable magnitude and said lesser magnitude, and whereby said output signal from said amplifier will bear an inversely proportional relation to the intensity of said input signal.

Claim 8

An optical densitometer of the type providing an output indication inversely proportional to the intensity of an incident light, comprising: means comprising a photometer for producing an output signal of predetermined polarity and of an amplitude directly related up to a predetermined maximum level to the intensity of said incident light; an amplifier having an input terminal and an output terminal and adapted to provide polarity inversion between said terminals; means for applying said output signal from said photometer to said amplifier input terminal; a source of unidirectional current of opposite polarity to the predetermined polarity of said photometer output signal; means for applying said unidirectional current to said amplifier input terminal at an absolute voltage level greater than said predetermined maximum output voltage level of said photometer to develop on said output terminal an electrical signal inversely proportional to the output signal level of said photometer; an output indicator directly responsive to an applied electrical signal; and means for applying the output signal from said amplifier to said output indicator to provide an output indication inversely proportional to the intensity of said incident light.

Claim 9

An optical densitometer of the type providing an output indication inversely proportional to the intensity of an incident light, comprising: means comprising a photometer for producing an output signal of predetermined polarity and of an amplitude directly related up to a predetermined maximum level to the intensity of said incident light; an amplifier having an input terminal and an output terminal and adapted to provide polarity inversion between said terminals; means for applying said output signal from said photometer to said amplifier input terminal; a source of unidirectional current of opposite polarity to the predetermined polarity of said photometer output signal; means for applying said unidirectional current to said amplifier input terminal at an absolute voltage level greater than said predetermined maximum output voltage level of said photometer to develop on said output terminal an electrical signal inversely proportional to the output signal level of said photometer; an output indicator directly responsive to an applied electrical signal; and means for applying the output signal from said amplifier to said output indicator to provide an output indication inversely proportional to the intensity of said incident light.

Claim 10

An optical densitometer as described in claim 5, wherein said means for applying said unidirectional current to said input terminal comprise an adjustable voltage divider.

Claim 11

An optical densitometer as described in claim 6, wherein said densitometer further comprises an impedance element coupled between the input and output terminals of said amplifier, said element providing in conjunction with said voltage divider a feedback loop for determining the effective gain of said amplifier.

Claim 12

An optical densitometer for producing an output indication inversely proportional to the logarithm of the intensity of incident light comprising: a photometer for detecting said incident light and for producing an output electrical signal of a given polarity and of a magnitude proportional to both the intensity of said incident light and to the magnitude of an applied bias; a summing network for combining said output electrical signal from said photometer with a second signal of opposite polarity and of a fixed magnitude greater than that of said output signal to produce a resultant signal; an amplifier having input and output terminals; means for applying said resultant signal to said input terminal; an output indicator responsive to an applied electrical signal; means for applying a bias proportional to the amplified resultant signal on said amplifier output terminal to said photometer to achieve a logarithmic output characteristic therefrom; and means for applying the amplified resultant signal from said amplifier output terminal to said indicating instrument to provide an output indication inversely proportional to the logarithm of the intensity of said incident light.

Claim 13

An optical densitometer for producing an output indication inversely proportional to the logarithm of the intensity of incident light comprising: a photometer for detecting said incident light and for producing an output electrical signal of a given polarity and of a magnitude proportional to both the intensity of said incident light and to the magnitude of an applied bias; a summing network for combining said output electrical signal from said photometer with a second signal of opposite polarity and of a fixed magnitude greater than that of said output signal to produce a resultant signal; an amplifier having input and output terminals; means for applying said resultant signal to said input terminal; an output indicator responsive to an applied electrical signal; means for applying a bias proportional to the amplified resultant signal on said amplifier output terminal to said photometer to achieve a logarithmic output characteristic therefrom; and means for applying the amplified resultant signal from said amplifier output terminal to said indicating instrument to provide an output indication inversely proportional to the logarithm of the intensity of said incident light.