Abstract: A sensor circuit for detecting light hazards or bright light sources that will cause discomfort. The sensor and sensor electronics which provide a wide sensitivity range which is fully automatically adjustable, and which has the ability to detect point sources of light. The sensor further has the ability to distinguish low power stable light generated from a small welding arc from bright ambient light or even direct sunlight.

Abstract: This invention provides a photoelectric transceiver (10) for detecting the presence and absence of objects (16) in a selected region (12). The transceiver (10) includes a light source (18), a light sensor (22), and electronic circuitry (13). The transceiver (10) generates a timing signal (MDCLK) that synchronizes its operation. In synchrony with the timing signal, the transceiver emits pulses of light (14) into the selected region (12) and senses light (24) coming from the selected region. When an object (16) is present in the selected region (12), the emitted light pulses (14) are reflected back to the transceiver (20). Based upon the light sensed, the transceiver generates an output (OUTOD) indicating whether or not an object is present. The transceiver includes three features that reduce the effect of interfering noise on the output (OUTOD). First, the output (OUTOD) is generated by a digital count hysteresis process to reduce the effect of random noise.

Abstract: A method of positioning a light beam on a picture surface relative to a light sensor located on the picture surface includes the step of completely illuminating the sensor with the light beam while the sensor is exposed to ambient light and recording a first output signal. A second output signal is recorded when the sensor is exposed to only ambient light. The first and second output signals are provided to an evaluation circuit to calculate a positioning signal having a value equal to a selected percentage of the difference between the first and second output signals.

Abstract: The present invention provides a photodetection apparatus having such an arrangement that when signals from the light receiving means in the photodetection device are sampled at a frequency substantially equal to the lowest frequency at which the source of pulse rays is lighted on, one of the noise signal I.sub.nc due to the pulsed illumination as from the fluorescent lamp and the normal output signal I.sub.sc from the laser beam necessarily presents for each of the sampling periods. In the preferred forms, output signal values sampled in the number of cycles corresponding to at least three times the sampling period are compared with each other. If it is judged that one output signal is larger than the other two output signals which are substantially equal to each other, it is determined that the one output signal is a normal output signal I.sub.sc from the laser beam. The one output signal is then taken for the subsequent signal processing step.

Abstract: An improved electronic control system for controlling the reflective state of automatic rearview mirrors for automative vehicles, the system including an electrochromic variable reflectance mirror element the reflectivity of which varies over a reflectance range as a function of electrical signal levels applied thereto. The system also includes a first sensing means effective to sense the ambient light level and produce a first electrical signal which is at least in part logarithmically related to the sensed ambient light level. A second sensing means is also provided which is effective to sense the glare causing light level and produce a second electrical signal which is at least in part logarithmically related to the sensed glare causing light level.

Abstract: A photodetection method and apparatus a sampling time period selected for detection and processing of the output signals from light receiving means such that it is sufficiently larger than the pulse width P.sub.S of a normal output signal I.sub.sc but very smaller than the pulse width P.sub.A of a noise signal I.sub.AC. During each of such sampling time periods, it is judged whether an output signal from the light receiving means is "present" or "absent". If the row of results obtained by at least three successive sampling periods is "0-1-0", it will be judged that the output signal generated during a sampling time period in which the output signal from the light receiving means is "present" is a normal output signal I.sub.SC. If output signals are "present" during two of at least three sampling time periods as shown by "0-1-1", "1-1-1", "1-1-0" or "1-0-1", it will be judged that these output signals are due to any disturbance rays.

Abstract: A light receiving section of a photocoupler according to the present invention has, for example, a light receiving element, a converting circuit, an oscillator, an updown (U/D) counter, a decoder and a clock signal supply control circuit, and those devices are monolithically integrated therein. When the light receiving element receives light from a light generating section, an output of the converting circuit becomes High. At this time, an output of the decoder is delayed until the U/D counter has counted up to the preset number a clock signal supplied by the clock signal supply control circuit. On the other hand, upon having Low of the output of the converting circuit, the output of the decoder is delayed until the U/D counter has counted down to "0" the clock signal supplied by the clock signal supply control circuit.

Abstract: The invention relates to measurements of light, where light variations superimposed on a background amount of light, which is changing relatively slowly, are measured. To give the light sensitive element (3,3') used a stable operational point a light emitting element (5,5') is used for injecting extra light into the light sensitive element (3,3'). Thus, the amount of light injected by this light emitting element (5,5') is chosen in such a way that the sum of the ambient light and the injected light is substantially constant. To this amount of light are added the light variations, e.g. caused by a second light emitting element (9,9'). This process and device can be used in a device for measuring the eye movements of a person.

Abstract: A fast acting sensing circuit for use in a warning system to indicate relative movement between an object and a sensor when the movement exceeds a predetermined rate of speed. The circuit only provides an output if the rate of speed exceeds the predetermined level.

Abstract: A reflection densitometer includes a light source and a photodetector having an output which has a signal component characteristic of the amount of reflected light received from a surface to be measured and a noise component. The noise component of the output is isolated in time by switching the light source on and off so as to create alternating first and second time periods during which the output of the photodetector is characteristic of only the noise component and in which the output of the photodetector is characteristic of both the signal component plus the noise component, respectively. The output of the photodetector during the second time period is subtracted from the output during the first time period to obtain a signal characteristic of only the output of the photodetector characteristic of relected light received.

Abstract: A contact type image sensor comprises a transparent substrate, photoelectric conversion elements disposed on the substrate, and an opaque film disposed selectively over the first photoelectric conversion elements. The first photoelectric conversion element over which the opaque film is disposed indicates a reference quantity of received light. The second photoelectric conversion element connected with the first photoelectric conversion element in adjacent relationship and having no opaque film disposed thereover indicates a quantity of light from an original document. A signal free from a varying luminance of the light source is obtained from the junction point of the first and second photoelectric conversion elements.

Abstract: An asynchronous photodetector circuit is provided to interrogate incoming signals and determine whether the frequency of those incoming signal pulses is acceptable. The circuitry of the present invention permits a series of incoming pulses to be interrogated to determine whether the frequency of those pulses is acceptable and can be assumed with confidence to be emanating from an appropriate light source. Upon the receipt of a first input signal pulse, a time window is created by the present invention to define a period to time during which a subsequent input signal pulse is to be expected. Other than during the duration of the time window, the present invention will not accept an input signal pulse and will not count that pulse as having been received. Each properly received pulse creates a subsequent time window until a predetermined number of consecutive pulses is received during their time windows. When that predetermined number is received, a signal is provided.

Abstract: A portable laser detection device is disclosed. Optical pulses are sensed by a photodiode and if the pulse width is less than a predetermined value a laser occurred indicator will flash until reset by the user. A laser present indicator will flash and an intermittent audible tone will be generated as long as laser energy having certain characteristics is present. A delay circuit ensures error free detection if a pulse having a width greater than the predetermined value is received immediately after a pulse having a width less than the predetermined value is received. Further, a high energy pulse with a sufficiently fast rise time received by the detector will cause the laser occurred indicator to flash, the laser present indicator to be illuminated continuously, and an audible tone to be generated. The device is shielded against electromagnetic interference and adapts automatically to variations in background noise.

Abstract: A circuit arrangement for a sanitary fitting controlled in a non-contacting manner comprises a transmitter (3) as well as a receiver (4), at which radiation emitted by the transmitter (3) arrives after reflection on an object (7). In an initialization process, which takes place for the first time after the initial installation, thereafter at greater regular time intervals, the capacity of the transmitter (3) is increased until the reflection on a stationary object (7) in the monitoring range has the result that the evaluation circuit (5) following the receiver (4) is activated. Now the capacity of the transmitter (3) is once more reduced somewhat; the circuit arrangement changes to normal operation. It now has its optimum sensitivity, at which stationary objects (7) no longer cause faulty actuations, but the greatest possible monitoring range is provided for movable objects to be monitored.

Abstract: The invention relates to a circuitry for compensating the effect of external light on infrared-sensitive phototransistors in a contact display panel, the phototransistors being coupled via diodes to a common line. The compensation circuitry is a voltage-dependent resistor between the common line and the ground of the circuit, the resistance value of the resistor decreasing as the direct-voltage level of the line rises. The resistor is preferably a transistor circuit.

Abstract: A remote data transfer system, particularly an identification system for identifying objects such as livestock, pets and containers. An interrogator generates a directional light beam which the operator can direct at a selected animal or package up to 30-14 200 meters away; and a tag transponder carried by the object is activated only on receipt of the light beam, and transmits a coded RF signal. The signal is received by the interrogator which displays the identity of the animal derived from the coded RF signal. In its "receive" mode, the tag transponder requires minimal power, thereby prolonging battery life. A short rise time light pulse (or a pulse sequence) is identified and used to switch power to the transponder. After transmission of the coded RF signal, the transponder returns to a low power draw stand-by state. The tag is also able to transmit real time information, with or without the tag identity data.

Abstract: An electronic circuit for encoding the emission of radiation generating control systems such as opto-electronic switches to ensure that the radiation they detect, is that of the encoded signal they emit. This is done by testing the received signal at two time intervals; first when the output driver activates the emitter, and again when the emission ceases, to verify the coincidence of the detected signal. If first it proves true and then false, it is considered valid. Optionally, this condition must be met for many consecutive tests in order to enable a valid response. If the detector senses radiation when the emitter is inactive, an anti-coincidence signal is produced to cease further emissions until this condition ends.

Abstract: A photoelectrical sensor (10) provided with a multistaged, filtered amplifier circuit (16) for amplifying voltage pulses from a phototransducer (12) and a filtering I/V converter (14) includes three voltage amplifier stages (28, 30, 32) and three respectively associated band pass filters (34, 36 and 38) for cascade connecting the amplifier stages (28, 30, 32) between the phototransducer (12) and the detector circuit (18) and accumulating attenuation of response to signals at a frequency equal to the frequency of full wave rectified AC line voltage to maximize desensitization of the photoelectrical sensor (10) to AC powered ambient light fluctuations while broadening the pass band at the low frequency end for maximum response to the desired signal. A gain control circuit (40) is associated with the first stage amplifier (28), while a temperature compensation circuit (42) adjusts the gain of a second stage amplifier stage (30) to correct for temperature variations.

Abstract: A reflection-type photoelectric proximity detector and switch is capable of detecting the incremental and binary proximity of a finger through several layers of glass, cancelling out extraneous reflections and stray sources of radiation. The circuitry includes a modulated infrared emitter, an infrared detector, an optical barrier, an infrared filter, a bandpass filter, a signal rectifier, a biasing circuit to remove unwanted detected modulated signal, an amplifier, an incremental proximity output, a comparator, a detection reference, and a binary proximity detect output. In one embodiment a multitude of photoelectric proximity switches are installed on the inside of a store window, detect finger proximity from outside the window, and control electric appliances inside the store window. From outside the window, a user can select what is displayed inside the window.

Abstract: A photoelectrical switching circuit, which produces a pulse-modulated light for detecting presence of an object by light interruption or reflection, comprises a frequency divider circuit and a signal output circuit and may comprise a control circuit. The frequency divider circuit includes a counter formed by flip-flops and an operation stop circuit. The counter generates light emission pulse signals with variable period and read pulse signals to pick up light sensing signals and outputting the state of the final stage flip-flop as an operation signal. The operation stop circuit stops the operation of the final stage flip-flop after the operation signal is input. The signal output circuit, which provides output signals after the operation signal is input, includes a shift register for shifting the light sensing signals in step with clock pulses, a set output AND circuit, and a reset output AND circuit.

Abstract: An article detection device includes: a light emission unit for emitting a detection light for irradiation onto an article, and a light reception unit for receiving a light reflected from the article. The article detection device also includes; an analog-to-digital converter for converting the reflected light to a digital signal, a first register for storing the digital signal after being sampled using a first sampling signal having a first period, and a second register for storing the digital signal after being sampled using a second sampling signal having a second period shorter than the first period.

Abstract: An error preventive circuit for a photoelectric switch is formed of a logic circuit, and it is highly responsive, while preventing erroneous operations caused by noises, eliminates the need of capacitors, and is suitable for circuit integration. The circuit validates the incoming light reception pulse only when its base-of-N counter has advanced to N counts, and, if the light reception pulse deviates in time by a certain value in the range of synchronism, a base-of-M counter is preset so that the timing of light reception is re-established at the center of the allowable range of synchronism.

Abstract: The optical input detection apparatus is adapted to integrate the value of the light received corresponding to the sum of the value of the light received by the light receiving device during driving of the light emitting device and the external flood light, deduct from the integration value the value of the light received equivalent to the external flood light received by the photodetector during the non-driving period following the driving of the light emitting device, compensate the integration value to the signal corresponding to the light emitting output and output the compensated signal to the comparator for comparison. Consequently, the presence or absence of an interruption in the light beam may be detected without being affected by the external flood light.

Abstract: An optical disk apparatus comprises a light emission detection circuit which converts a light emission from a light source into an electric signal and releases it as a light emission signal, a photo detector which releases an output signal upon reception of a reflected light from a disk and/or stray lights, a correction signal generating circut which adjusts a prescribed gain in accordance with the amount of stray light, and generates a correction signal by attenuating the light emission signal based on this gain, a subtracter in which the correction signal is subtracted from the output signal of the photo detector, and disk discharging means for discharging the disk from the optical disk apparatus, when the disk is present in the optical disk apparatus during the adjustment of the above-mentioned gain.

Abstract: The invention relates to a circuit for a light-sensitive element (1), for example an infrared diode. The anode (a) of the light-sensitive element is coupled to a point of constant potential (earth). The cathode (c) of the light-sensitive element (1) is coupled to the collector of a pnp transistor (7) and, via a resistor (3), to the base of this transistor. The emitter of the transistor is coupled to a second point (6) of constant potential (+). The base is also coupled to this point (6) via a series arrangement of a resistor (5) and a capacitor (4). The desired sensitivity of the circuit is maintained even in the case of a high background light level.

Abstract: A discriminating apparatus for discriminating a radiant information signal from a background signal, the discriminating apparatus including a radiation sensing means sensitive to an incident signal comprising both an information signal and a background signal and operative to generate an output sensing signal of a level related to the level of the incident signal, and detector means responsive to the sensing signal to detect an information signal component of the sensing signal from a background signal level component of the sensing signal.

Abstract: A system and method are provided using a photodetector array for producing an output signal which is compensated for the effects of ambient light, photodetector bias, and the like, wherein the output signal contains information indicative of the position of the object. The preferred embodiment is useful for vehicular wheel alignment and includes left and right wheel units for coupling to respective left and right steerable wheels of a vehicle, and a central microcomputer and CRT display operably coupled with each wheel unit. Each preferred wheel unit includes a photodetector array operably connected to a wheel unit microcomputer and a laser beam source directing a laser beam toward the array of the other wheel unit.

Abstract: The system enables the lowering of the false alarm rate by eliminating, in particular, the spurious pulses created by the detectors themselves. To this effect, it has one or more juxtaposed optical channels to cover the total field. Each optical channel is associated with a pair of detecting elements to form two detecting channels. After amplification and threshold comparison in these channels, the correlation of the two channels is produced to eliminate the spurious signals and select only the useful signal which is simultaneously present on both channels.

Abstract: An input device which can be employed to input commands to a computer directly through a CRT display is disclosed. The input device employs a plurality of infrared light emitting diodes and phototransistors aligned in individual emitter-detector pairs. Infrared beams from the emitter cross the display field before striking the corresponding detector. Emitters and detectors are sequentially activated and each emitter is pulsed or modulated at a frequency different from the variation of ambient conditions during each emitter activation interval. The detection circuitry thus can distinguish the varying emitter signal from ambient or spurious variations. A number of pulses at the pulsed or modulated emitter frequency would be detected unless an opaque element were blocking the particular beam.

Abstract: A photodetecting circuit for detecting radiation emitted from a light emitting element in the presence of ambient radiation is disclosed. The circuit includes a first and a second synchronizing on/off input signal having a predetermined period, each signal being complementary to the other. When the first synchronizing signal is "on", the second synchronizing signal is "off" and the circuit can detect the amount of ambient radiation. When the first synchronizing signal is "off", the second synchronizing signal is turned "on" and the light emitting element is energized and the circuit detects the amount of radiation emitted therefrom. The circuit prevents erroneous readings of radiation emitted from the light emitting element when the amount of detected ambient radiation is high.

Abstract: A semiconductor light position detector for a rangefinder which projects a light beam onto an object and receives a reflected light beam from the object to measure a distance to the object. A portion of the light-receiving surface of the detector on which the reflected beam will not form a light spot is partially covered with a member that blocks unwanted light. Thus, the malfunctions caused by the flare component of the light from the light projector and the malfunctions due to increases in the shot noise under a high illuminance are reduced greatly.

Abstract: The output of a diode array undergoes A/D conversion. A constant digital value is added to the output when remote light sources remain de-energized to establish an ambient threshold level. The remote sources are then energized; and when a digital array output signal is sensed at a level exceeding the threshold, the positive existence of a sensed source is established. The invention has application in the measurement of aircraft wing vibration.

Abstract: A current injection compensation circuit for dynamically compensating for the effect of ambient conditions on phototransistor output is disclosed. An output voltage is maintained at a nominal reference voltage level independent of ambient light input to allow use of a large output for a detected signal. Phototransistor current is a function only of ambient conditions, especially incident ambient light and is unaffected by compensation current injection. The ambient compensation current injection network can be employed with interactive touch input devices, such as infrared touch entry systems used with video displays.

Abstract: The invention relates to an electric control arrangement intended for use with object detecting systems, which include, inter alia, a light source (2) intended for transmitting light beams in a direction in which an object (3) to be detected can be expected to appear, at least one receiver unit (4, 5) for receiving light beams reflected by a detected object, and electrical and/or electronic devices for evaluating and detecting the presence of the object in response to variations that occur in the received reflected light beams as a result of relative movement between the object (3) to be detected and light beams (2a) transmitted by the light source.

Abstract: A digital optical receiver circuit adapted to operate over a wide input dynamic range without distorting its output signal. The circuit includes a first circuit for receiving input signals in a selected pulse width range and converting them into output signals of extended pulse width. A second circuit will then convert the output signals into digital signals of the same pulse width.

Abstract: An optical motion sensor comprises first and second light emitting diodes that emit complementary pulsed beams of infrared energy within a sensing region. A photodiode sums the energies to produce a proportional sensing signal. An amplifier AC coupled to the photodiode blocks the constant portion of the sensing signal and passes a time varying signal portion produced by motion of an object to a sampling circuit. The sampling circuit samples the sensing signal synchronous with emission of the first pulsed beam and converts the time varying signal to a proportional detection signal. An integrator coupled to the sampling circuit responds to a detection signal by modulating the intensity of the second pulsed beam to null the earlier time varying portion of the sensing signal. The motion sensor can be configured as a presence sensor by changing the time constant of the integrator.

Abstract: A proximity detecting and warning system for use in collision avoidance, particularly with aircraft. The system responds to pulsed light sources within a selected frequency band and particularly the frequency of aircraft strobe and rotating beacon light sources while disregarding any other natural steady state light sources as well as man-made light sources such as street lighting and ground lighting sources. The system detects pulsed light sources on aircraft or vehicles within the proximity of the transmitter and provides a visual and audible alarm to a pilot or operator. The alarm occurs when another aircraft is within the detection envelope which typically extends in an elliptical pattern around the transmitter in all directions with a detection range of up to approximately three miles. The circuit is designed to detect the strobe or rotating beacons having frequencies standardized by Federal Regulations which also require that these sources be illuminated at all times during flight.

Abstract: A current injection compensation circuit for dynamically compensating for the effect of ambient conditions on phototransistor output is disclosed. An output voltage is maintained at a nominal reference voltage level independent of ambient light input to allow use of a large output for a detected signal. Phototransistor current is a function only of ambient conditions, especially incident ambient light and is unaffected by compensation current injection. The ambient compensation current injection network can be employed with interactive touch input devices, such as infrared touch entry systems used with video displays.

Abstract: A continuous wave laser light beam is directed at the refractory lining within a furnace vessel, and the displacement as measured by a self-scanned linear array of the scattered light beam from a nominal or reference position measured to provide an indication of lining wear or damage. The video signal received by the linear array receiver provides information for mapping the worn or damaged areas of the vessel lining so that such areas may be repaired by a gunning spray nozzle. The inspection apparatus includes an optical filter which is temperature controlled to prevent wavelength shifts away from the nominal laser wavelength. The electronic processing circuitry includes a voltage controlled oscillator responsive to the average background level for modifying the scan rate of the linear array to compensate for changes in background level. The threshold against which the reflected laser beam video signal is compared is also a function of background level.

Abstract: The sensitivity of an optically-based touch screen is substantially impro by adaptively establishing the detection threshold based on the peak trapped light measured over a number of frames on the screen being painted. In accordance with one feature of the invention, the peak trapped light from a target area painted on the screen is compared with a priorly established threshold as a way of determining that a target area is being touched by the user. In accordance with another feature of the invention, the threshold is modified in a way that compensates for possible erroneous touch indications due, for example, to bright spots on the screen.

Abstract: A hand held bar code reader employs a laser diode as its laser source, for an efficient and compact construction. The diode is modulated, and an associated bar code reading detector is timed accordingly, so that (1) the effects of strong ambient light which may be present on the bar code surface can be subtracted out, by alternating reflected light readings of the detector between laser beam plus ambient and ambient alone, and subtracting the readings electronically, and (2) peak power can be increased to obtain more dependable readings while staying within permissible power levels for such devices, since average power is reduced by the modulation of the laser.

Abstract: A photo-electric converting device includes storing parts which store electric charges obtained through a photo-electric conversion process respectively from reflected light received when light projection is performed by light emitting apparatus and another reflected light received when no light is projected by the light emitting apparatus. The device computes storage signals produced from the storing parts and detects an electric signal which corresponds solely to reflected light resulting from light projection performed by the light emitting apparatus.

Abstract: The disclosed device responds to pulsed light from a light source to produce electrical signals. A photo-electric transducer element uses a number of signal storage sites on which successive signals from the photo-electric transducer element are accumulated. A signal flow circuit transfers the stored signals from one of the signal storage sites to another in synchronism with the energization and de-energization of the light source. Simultaneously, those signals produced when the light source is energized are accumulated on a common storage site. The other signals produced when the light source is not energized are accumulated on another common storage site. When performing a computation on the basis of an electrical readout of one set of stored signals and another electrical readout of another set of stored signals, the different characteristics of the different storage site prevent inaccurate results.

Abstract: An improved photosensitive motion detector which detects abrupt changes within a field of view while ignoring gradual changes in ambient lighting therein. In addition, sensitivity to such changes is maintained without regard to the intensity level of the ambient light, and is not sensitive to the "flickering" of fluorescent lamps. Light from said field of view, which can contain an abrupt discontinuity therein, is focussed upon two substantially identical photocells, each of which is in parallel with one of two substantially identical photoresistors, each of which is closely optically coupled to one of two LEDs connected in parallel but in reverse polarity from a common junction to a common potential.

Abstract: In the disclosed photo-electric conversion device, a light source repetitiously emits light and a photo-electric converter receives reflected light originally generated by the source and ambient light. A first store stores the output of the photo-electric converter when the light source emits light and a second store stores data from the photo-electric converter when the source does not emit light. A gate transfers the output from the converter to the first and second stores. A pulse generator controls the gate for transferring the converter output to the first store and the second store during every light emitting cycle of the light source.

Abstract: A distance measuring apparatus for automatically measuring a distance from a reference point to a subject of interest, such as a subject to be photographed, is provided. The present apparatus includes a position sensitive detector having a photoelectric surface defined between two extreme points. Thus, when a light pulse emitted from the apparatus is reflected by the subject and impinges upon the photoelectric surrface, there is produced a pair of current signals, which are then processed to obtain a distance signal indicating the distance to be measured. Thus, the present apparatus can provide a highly accurate measurement.

Abstract: A control circuit for timing the duration of a flash of artificial illumination from an electronic flash maintains a substantially uniform amount of artificial illumination regardless of the ambient scene light intensity by detecting the ambient scene light intensity up to the instant that the flash is fired and thereafter subtracting the ambient scene light intensity so detected immediately prior to the flash being fired from the ambient and artificial scene light intensity detected during the flash of artificial illumination.

Abstract: A distance measurement system for measuring distance to an object by emitting light to the object and measuring the intensity of light reflected from the object.

Abstract: A laser rangefinder comprises a transmitter (19) controlled by sequence-controlled pulses emitted by a timer (16) following actuation of a switch (17) by an operator. The receiver of the rangefinder comprises an avalanche photodiode (APD) (10) the sensitivity of which is controlled in a time-programmed manner by a bias voltage controller (11) which receives timing pulses from the timer (16). The time-programmed control operates to render the APD 10 insensitive to protect the receiver against optical element backscatter and atmospheric backscatter prior to rendering the APD 10 sensitive to monitor return pulses from remote targets.

Abstract: An improved inside rearview mirror particularly adapted for use with automotive vehicles, the mirror incorporating improved means for detecting and comparing the relative brightness of light forwardly and rearwardly of the vehicle and improved means responding automatically to annoying glare from the rear of the vehicle to move a reflective element from a full reflective mode to a partial reflective mode and also automatically return the reflective element to a full reflective mode after the source of the annoying glare is removed.