US4488052A — Method and system to reduce low-frequency noise i…

Claim 1

Independent Claim 202 words

Method of suppression of additively superimposed noise in a semiconductor light sensor--amplifier combination having a semiconductor light sensor element (1); clock signal supplying means (4, 5) respectively energizing the light sensor in accordance with clock signals for transfer of read-out signals therefrom; output means (2, 3) coupled to the sensor and receiving output signals therefrom varying between a maximum level, in dependence on the intensity of incident light, and a minimum level; and amplifier means (6, 7) amplifying the output from said output means, and providing an amplified output signal, said amplifier means introducing noise signals (U N ), the noise from the output means being at a frequency which is low with respect to the frequency of the clock signal, comprising, in accordance with the invention, the steps of sensing the maximum value of the output signal from the amplifying means which includes the signal from the sensor and an additive component respresentative of the then instantaneous noise of the amplifying means (U S+N ), sensing the minimum value signal; detecting the sensed maximum value signal and the sensed minimum value signal; and subtracting the detected signals from each other to thereby eliminate low-frequency shifting effects due to said low-frequency noise.

Claim 2

Dependent Claim 202 words

Method of suppression of additively superimposed noise in a semiconductor light sensor--amplifier combination having a semiconductor light sensor element (1); clock signal supplying means (4, 5) respectively energizing the light sensor in accordance with clock signals for transfer of read-out signals therefrom; output means (2, 3) coupled to the sensor and receiving output signals therefrom varying between a maximum level, in dependence on the intensity of incident light, and a minimum level; and amplifier means (6, 7) amplifying the output from said output means, and providing an amplified output signal, said amplifier means introducing noise signals (U N ), the noise from the output means being at a frequency which is low with respect to the frequency of the clock signal, comprising, in accordance with the invention, the steps of sensing the maximum value of the output signal from the amplifying means which includes the signal from the sensor and an additive component respresentative of the then instantaneous noise of the amplifying means (U S+N ), sensing the minimum value signal; detecting the sensed maximum value signal and the sensed minimum value signal; and subtracting the detected signals from each other to thereby eliminate low-frequency shifting effects due to said low-frequency noise.

Claim 3

Dependent Claim 50 words

Method according to claim 1, including the step of clamping the minimum value signal to a fixed reference; and utilizing said fixed reference as a base level for the maximum value signal to thereby eliminate low-frequency shifting effects due to low-frequency noise affecting both the minimum and maximum value signals.

Claim 4

Dependent Claim 40 words

Method according to claim 1, including the step of determining a reference level comprising suppressing the base band of the output signals, due to said clock signals, and demodulating the carrier of the clock frequency, and the associated side bands.

Claim 5

Dependent Claim 39 words

Method according to claim 1, including the steps of determining a reference level comprising synchronously demodulating the signals derived from the amplifier means with the clock frequency of said clock signals; and band pass limiting the synchronously demodulated signal.

Claim 6

Dependent Claim 26 words

Method according to claim 4, wherein said band pass limiting step comprises limiting the output signals to a frequency of about half the demodulating clock frequency.

Claim 7

Dependent Claim 187 words

System for suppression of additively superimposed noise in a semiconductor light sensor--amplifier combination having a semiconductor light sensor element (1); clock signal supplying means (4, 5) respectively energizing the light sensor in accordance with clock signals for transfer of read-out signals therefrom, at a predetermined clock frequency; output means (2, 3) coupled to the sensor and receiving output signals therefrom varying between a maximum level, in dependence on the intensity of incident light, and a minimum level; and amplifier means (6, 7) amplifying the output from said output means and providing an amplified output signal, said amplifier means introducing noise signals (U N ), the noise from the output means being at a frequency which is low with respect to the frequency of the clock signal, comprising, in accordance with the invention, threshold circuit means connected, respectively, to said amplifier means (6, 7) to separate the minimum and maximum value signals; and subtraction circuit means (24) connected to said threshold circuit means and establishing a reference level value based on the subtraction of the minimum level, as sensed by said threshold circuit means, from the maximum value.

Claim 8

Dependent Claim 187 words

System for suppression of additively superimposed noise in a semiconductor light sensor--amplifier combination having a semiconductor light sensor element (1); clock signal supplying means (4, 5) respectively energizing the light sensor in accordance with clock signals for transfer of read-out signals therefrom, at a predetermined clock frequency; output means (2, 3) coupled to the sensor and receiving output signals therefrom varying between a maximum level, in dependence on the intensity of incident light, and a minimum level; and amplifier means (6, 7) amplifying the output from said output means and providing an amplified output signal, said amplifier means introducing noise signals (U N ), the noise from the output means being at a frequency which is low with respect to the frequency of the clock signal, comprising, in accordance with the invention, threshold circuit means connected, respectively, to said amplifier means (6, 7) to separate the minimum and maximum value signals; and subtraction circuit means (24) connected to said threshold circuit means and establishing a reference level value based on the subtraction of the minimum level, as sensed by said threshold circuit means, from the maximum value.

Claim 9

Dependent Claim 59 words

System according to claim 6, further including switching means (16, 17) operated in synchronism with said clock signals and switching the outputs from said amplifier means (6, 7) at the time of occurrence of the minimum value, as determined by said clock signals, to a reference level to thereby clamp the minimum value signal to a constant reference voltage.

Claim 10

Dependent Claim 32 words

System according to claim 6, wherein the threshold circuit means includes non-additive mixing circuit means connected, respectively, to said amplifier means (6, 7) to supply the minimum and maximum value level signals.

Claim 11

Dependent Claim 64 words

System according to claim 8, wherein the semiconductor light sensor (1) has two outputs supplying output signals, phase-shifted with respect to each other in regard to the maximum and minimum values at said output signals, wherein two non-additive mixing circuits are provided, one, each, having an input connected to a respective output signal from the sensor, said non-additive mixing circuit having relatively opposite polarity.

Claim 12

Dependent Claim 164 words

System according to claim 9, wherein a first one of said non-additive mixing circuits comprises two transistors (71, 72), the emitters of which are connected to a common emitter resistor (73), and the bases of which are connected, respectively, to the output signals from the respective amplifier means (6, 7) connected to the respective output terminals of the light sensor element (1); and wherein a second non-additive mixing circuit means comprises two further transistors (71', 72') of opposite conductivity type to the transistors of said first mixing circuit, the emitters of said further transistors being connected to a common emitter resistor (75) and to a source of constant reference voltage (-12 V), the bases of said further transistors being additionally connected to the respective output signals from said respective amplifier means and in parallel to the bases of the transistors of said first mixing circuit; the subtraction circuit means (24; 76, 77) being connected to the outputs from the respective pairs of said transistors.

Claim 13

Dependent Claim 42 words

System according to claim 9, further including low-pass filter means (25; 89) receiving the output from said subtraction circuit means (24; 76), said low-pass filter having a filtering limit frequency in the order of about half the frequency of the clock signal.

Claim 14

Dependent Claim 209 words

System for suppression of additively superimposed noise in a semiconductor light sensor--amplifier combination having a semiconductor light sensor element (1); clock signal supplying means (4, 5) respectively energizing the light sensor in accordance with clock signals for transfer of read-out signals therefrom, at a predetermined clock frequency; output means (2, 3) coupled to the sensor and receiving output signals therefrom varying between a maximum level, in dependence on the intensity of incident light, and a minimum level; and amplifier means (6, 7) amplifying the output from said output means and providing an amplified output signal, said amplifier means introducing noise signals (U N ), the noise from the output means being at a frequency which is low with respect to the frequency of the clock signal, comprising, in accordance with the invention, two band-pass filters having band-pass frequencies centered about the frequency of said clock signal and having a band-pass width such that the base band of the output signals is suppressed; an envelope demodulator (30) connected to said band-pass filters and demodulating the carrier corresponding to said clock frequency and the associated side bands; and a low-pass filter (32) connected to said amplitude demodulator and having a band pass of about half the frequency of said clock frequency.

Claim 15

Dependent Claim 209 words

System for suppression of additively superimposed noise in a semiconductor light sensor--amplifier combination having a semiconductor light sensor element (1); clock signal supplying means (4, 5) respectively energizing the light sensor in accordance with clock signals for transfer of read-out signals therefrom, at a predetermined clock frequency; output means (2, 3) coupled to the sensor and receiving output signals therefrom varying between a maximum level, in dependence on the intensity of incident light, and a minimum level; and amplifier means (6, 7) amplifying the output from said output means and providing an amplified output signal, said amplifier means introducing noise signals (U N ), the noise from the output means being at a frequency which is low with respect to the frequency of the clock signal, comprising, in accordance with the invention, two band-pass filters having band-pass frequencies centered about the frequency of said clock signal and having a band-pass width such that the base band of the output signals is suppressed; an envelope demodulator (30) connected to said band-pass filters and demodulating the carrier corresponding to said clock frequency and the associated side bands; and a low-pass filter (32) connected to said amplitude demodulator and having a band pass of about half the frequency of said clock frequency.

Claim 16

Dependent Claim 180 words

System for suppression of additively superimposed noise in a semiconductor light sensor--amplifier combination having a semiconductor light sensor element (1); clock signal supplying means (4, 5) respectively energizing the light sensor in accordance with clock signals for transfer of read-out signals therefrom, at a predetermined clock frequency; output means (2, 3) coupled to the sensor and receiving output signals therefrom varying between a maximum level, in dependence on the intensity of incident light, and a minimum level; and amplifer means (6, 7) amplifying the output from said output means and providing an amplified output signal, said amplifier means introducing noise signals (U N ), the noise from the output means being at a frequency which is low with respect to the frequency of the clock signal, comprising, in accordance with the invention, synchronous demodulator means (34, 35) having a synchronizing frequency corresponding to the clock frequency of said clock signals applied thereto; and a low-pass filter, connected to the output of said synchronous demodulator means, the low-pass filter having an upper limit frequency corresponding to approximately half the clock frequency.

Claim 17

Dependent Claim 180 words

System for suppression of additively superimposed noise in a semiconductor light sensor--amplifier combination having a semiconductor light sensor element (1); clock signal supplying means (4, 5) respectively energizing the light sensor in accordance with clock signals for transfer of read-out signals therefrom, at a predetermined clock frequency; output means (2, 3) coupled to the sensor and receiving output signals therefrom varying between a maximum level, in dependence on the intensity of incident light, and a minimum level; and amplifer means (6, 7) amplifying the output from said output means and providing an amplified output signal, said amplifier means introducing noise signals (U N ), the noise from the output means being at a frequency which is low with respect to the frequency of the clock signal, comprising, in accordance with the invention, synchronous demodulator means (34, 35) having a synchronizing frequency corresponding to the clock frequency of said clock signals applied thereto; and a low-pass filter, connected to the output of said synchronous demodulator means, the low-pass filter having an upper limit frequency corresponding to approximately half the clock frequency.

Claim 18

Dependent Claim 90 words

System according to claim 13, wherein the semiconductor light sensor has two outputs which provide maximum and minimum output values phase-shifted with respect to each other, and wherein said synchronous demodulator means comprises two synchronous demodulators (34, 35) having said clock signals applied thereto; the amplifier means (6, 7) comprise amplifiers, respectively connected to the respective outputs from the sensor (1) and supplying their outputs to the synchronous demodulator; an adder circuit (38) adding the outputs from said synchronous demodulators, and supplying the added output to the low-pass filter (39).

Claim 19

Dependent Claim 219 words

System for suppression of additively superimposed noise in a semiconductor light sensor--amplifier combination having a semiconductor light sensor element (1); clock signal supplying means (4, 5) respectively energizing the light sensor in accordance with clock signals for transfer of read-out signals therefrom, at a predetermined clock frequency; output means (2, 3) coupled to the sensor and receiving output signals therefrom varying between a maximum level, in dependence on the intensity of incident light, and a minimum level; an amplifier means (6, 7) amplifying the output from said output means and providing an amplified output signal, said amplifier means introducing noise signals (U N ), the noise from the output means being at a frequency which is low with respect to the frequency of the clock signal, comprising, in accordance with the invention, extreme value responsive circuit means (22, 23; 26, 27; 71, 72, 71', 72') respectively connected to the outputs of said amplifier means and detecting the maximum and minimum levels of said maximum and minimum value signals; and difference circuit means (24) connected to said extreme value detection circuit means, and determining the difference between said signals and providing an output signal representative of said difference to thereby eliminate low-frequency components shifting said signal levels at a rate low with respect to the clock frequency of said signal.

Claim 20

Dependent Claim 219 words

System for suppression of additively superimposed noise in a semiconductor light sensor--amplifier combination having a semiconductor light sensor element (1); clock signal supplying means (4, 5) respectively energizing the light sensor in accordance with clock signals for transfer of read-out signals therefrom, at a predetermined clock frequency; output means (2, 3) coupled to the sensor and receiving output signals therefrom varying between a maximum level, in dependence on the intensity of incident light, and a minimum level; an amplifier means (6, 7) amplifying the output from said output means and providing an amplified output signal, said amplifier means introducing noise signals (U N ), the noise from the output means being at a frequency which is low with respect to the frequency of the clock signal, comprising, in accordance with the invention, extreme value responsive circuit means (22, 23; 26, 27; 71, 72, 71', 72') respectively connected to the outputs of said amplifier means and detecting the maximum and minimum levels of said maximum and minimum value signals; and difference circuit means (24) connected to said extreme value detection circuit means, and determining the difference between said signals and providing an output signal representative of said difference to thereby eliminate low-frequency components shifting said signal levels at a rate low with respect to the clock frequency of said signal.

Claim 21

Dependent Claim 35 words

System according to claim 15, further including a low-pass filter (25) connected to the output of said difference circuit means (24) and having a pass band of about half the frequency of said clock frequency.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1987-12-11	1988-06-11	1988-12-11	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1991-12-11	1992-06-11	1992-12-11	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1995-12-11	1996-06-11	1996-12-11	$7700.00	Window Closed / Lapsed

Method and system to reduce low-frequency noise in semiconductor sensors

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