Photoelectric signal generating circuits

• US 4,074,128 A
• Filed: 04/22/1977
• Issued: 02/14/1978
• Est. Priority Date: 05/05/1976
• Status: Expired due to Term

• Current Assignee: Genicom Corp.
• Original Assignee: General Electric Company
• Inventors: Harris, Samuel C. Jr., Hanger, William A.
• Primary Examiner(s): Nelms, David C.
• Application Number:
  US05/789,854
• Time in Patent Office: 298 Days
• Field of Search: 250/231 R, 250/231 SE, 250/237 G, 250/237 R, 250/205, 250/209, 250/199, 250/214 C, 356/169, 356/170, 324/175
• US Class Current: 250/205
• CPC Class Codes: G01D 5/26 characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
• CPC Class Codes: G01D 5/363 Direction discrimination
• CPC Class Codes: G05B 19/231 the positional error is used to control continuously the servomotor according to its magnitude
• CPC Class Codes: G05B 2219/37151 Handling encoder signal, compensation for light variation, stray light
• CPC Class Codes: G06K 7/10851 Circuits for pulse shaping, amplifying, eliminating noise signals, checking the function of the sensing device basic electronic circuitry H03
• CPC Class Codes: H02P 23/22 Controlling the speed digitally using a reference oscillator, a speed proportional pulse rate feedback and a digital comparator
• CPC Class Codes: H03K 17/968 using opto-electronic devices

Abstract

A regulator for a two phase shaft encoder used in sensing irregular body movements which determines when the light transmission of a photocoupler is maximum and corrects the photocoupler output to agree with a reference value.

Claims

1. An arrangement wherein a shaft encoder comprises a first and second source of light, and means are provided for pulsing said sources of light with light opaque and light transparent segments provided on a rotating disc and representative of the angular position of the shaft, means for regulating the light intensity of said sources comprising a first and second sensor for sensing the light interrupted by said disc at separate predetermined points to provide a respective one of a pair of signals, wherein the amplitudes of said pair of signals are phase displaced by 90°

as light passed by the disc changes recurrently through a cycle of maximum to minimum to maximum intensity as the shaft and disc rotate, a respective reversible counter and a respective digital to analog converter associated with each of said first and second light sources, a source of a first and second reference signal for each sensor, means for comparing the voltage developed by each sensor with one of said first and one of said second reference signals to provide first and second control signals respectively, means responsive to the first control signal associated with one sensor to change the count of the reversible counter associated with the second sensor by a predetermined count, means responsive to the second control signal associated with said second sensor to control the direction of said predetermined count, each of said digital to analog converters responsive to the count of the reversible couner associated therewith to provide an analog signal, each source of light responsive to its associated analog signal to vary its light intensity to regulate the amplitude of the light pulses with respect to said given reference levels.

2. A photoelectric apparatus for sensing recorded information expressed in the form of the presence or absence of indicia born on a moving carrier and for expressing such information as sensed in the form of electrical signals comprising a first and second photocoupler, said couplers comprising a light source positioned adjacent said carrier for illuminating said carrier such that the illumination is propagated by said carrier according to the presence and absence of said indicia, said couplers further comprising a respective detection means positioned adjacent said carrier for detecting said illumination from said source as propagated by said carrier to provide a respective output signal, a source of a first reference signal, means coupled to one said detection means for determining when the illumination propagated by said carrier to the other of said detection means is a maximum, and for detecting the value of said maximum illumination to provide a first signal, means for comparing said first signal with said reference signal to produce an error signal and means for modifying the amplitude of illumination of said other detection means by said source in accordance with said error signal.

3. A photoelectric apparatus for sensing recorded information expressed in the form of the presence or absence of indicia born on a moving carrier and for expressing such information as sensed in the form of electrical signals comprising a first and a second light emitting diode positioned adjacent said carrier for illuminating said carrier such that the illumination is propagated by said carrier according to the presence and absence of said indicia, means positioned adjacent said carrier for detecting said illumination from said source as propagated by said carrier, said means comprising first and second detectors, a first aperture arrangement positioned between said carrier and said first detector, a second aperture arrangement positioned between said second detector and said carrier, means for positioning said aperture arrangements such that when light illumination propagated by said carrier and said first aperture arrangement reaches a maximum amplitude illumination passed by said carrier, said second aperture arrangement is at half the maximum amplitude, a first reversible counter associated with said first light emitting diode and a second reversible counter associated with said second light emitting diode, a half amplitude reference signal source and a maximum amplitude reference signal source associated with each of said first and second detectors, respective comparators for comparing the photodetector outputs with a respective half amplitude reference signal and respective maximum amplitude reference signal to provide respective logic level signals, means responsive when a photodetector output of one phase crosses the half amplitude reference value to provide a predetermined count pulse to the counter of the other phase, means responsive when the photodetector output of one phase reaches the maximum reference value to determine the direction of counting of the counter associated with the other phase, a digital to analog converter coupled between each of said counters and its associated photodetector for modifying the illumination provided by said associated photodetector in accordance with the count stored in the counter associated with such detector.

4. Apparatus for regulating output signals from a photosensor coupled with a light source by way of a first transmission path traversing a region recurrently varying the attenuation of energy propagated along said path comprising power control means coupled to said light source, means for developing a first signal wave from the output of said photosensor, means for developing a second signal wave having the same periodicity as said first signal wave and shifted in time with respect thereto, and means for acting on said power control means in accordance with the timing action of said second signal wave and controlled as to sense by said first signal wave.

5. Apparatus according to claim 4 wherein said time shift is of a magnitude placing said second signal wave substantially in quadrature with said first signal wave.

6. Apparatus according to claim 5 wherein said means for developing said second signal wave includes a second light source and photosensor coupled over a second transmission path of variable attenuation.

7. Apparatus according to claim 4 further comprising a counter, means for controlling the operation of said counter by said second signal wave and means for modifying the count content of said counter by said first signal wave.

8. Apparatus according to claim 7 further comprising a digital to analog converter coupled to an output of said counter for acting on the function of said power control means.

9. In combination, a first and second radiant energy sensor coupled with a respective first and second radiant energy source by way of a first and second transmission path traversing a region which recurrently varies the attenuation of energy propagated along said paths, first and second control means coupled to said first and second sources respectively, first means coupled to said first sensor for developing a first signal wave representative of the propagation of energy from said first source to said first sensor by way of said first transmission path, second means coupled to said second sensor for developing a second signal wave representative of the propagation of energy from said second source to said second sensor by way of said second transmission path, a first counter associated with said first source, a second counter associated with second source, the passage of said first wave through a reference level enabling said second counter, the passage of said second wave through a reference level enabling said first counter, the level of said first wave during first counter enablement operating said first counter, the level of said second wave during second counter enablement operating said second counter.

10. An arrangement according to claim 9 further comprising means for controlling the sense of each counter'"'"'s operation in response to the sense of the difference between the signal wave actuating the respective counters and a reference level for such last named signal wave.