Abstract: A depth camera assembly (DCA) includes a direct time of flight system for determining depth information for a local area. The DCA includes an illumination source, a camera, and a controller. The illumination source projects light (e.g., pulse of light) into the local area. The camera detects reflections of the projected light from objects in the local area. Using an internal gating selection procedure, the controller selects a gate window that is likely to be associated with reflection of a pulse of light from an object. The selected gate may be used for depth determination. The internal gating selection procedures may be achieved through external target location and selection or through internal self-selection.

Abstract: A laser controller with backscatter detection includes an electromagnetic radiation source operable to transmit radiation into the environment, a backscatter detector operable to detect backscattered radiation from the environment, and a processor operable to generate a laser control signal based on characteristics of the detected backscattered radiation.

Abstract: Various embodiments of the present technology may provide methods and apparatus for a time-to-digital converter. The time-to-digital converter may include a state machine that increments/decrements according to an input signal and a count value. The time-to-digital converter may further include a register to store the count value according to the input signal.

Abstract: A depth camera assembly (DCA) includes a direct time of flight system for determining depth information for a local area. The DCA includes an illumination source, a camera, and a controller. The illumination source projects light (e.g., pulse of light) into the local area. The camera detects reflections of the projected light from objects in the local area. Using an internal gating selection procedure, the controller selects a gate window that is likely to be associated with reflection of a pulse of light from an object. The selected gate may be used for depth determination. The internal gating selection procedures may be achieved through external target location and selection or through internal self-selection.

Abstract: An image recognition device includes a light source that emits lighting pulses to a measurement space, a image generator that generates a distance image based on reflected light acquired by a light receiving element, a reflectivity calculator that calculates a correction coefficient corresponding to a reflectivity for each measurement section, and a lighting pulse controller that controls a number of lighting pulses emitted from the light source according to the correction coefficient for each measurement section.

Abstract: A lidar and optical rangefinder receiver improves signal detection in the presence of varying levels of environmental light and other noise sources. The occurrence of false triggers, due to noise, during periods when no optical pulse is emitted is used to adjust the pulse detection threshold level and simultaneously calibrate the time-of-flight timer. The photodetector's response to ambient light is also used to adjust the threshold level. Example systems include signal detection electronics with dynamic thresholding and real-time calibration of timing electronics, in which the threshold level for signal detection is adjusted in response to both information acquired during calibration cycles and ambient light measured between active rangefinding cycles.

Abstract: A method for determining a maximum speed for a vehicle, including: receiving items of state information concerning a state of at least one vehicle component of the vehicle; and determining a maximum speed of the vehicle on the basis of the state information, such that a stopping path of the vehicle from a recognition of a dangerous state until the vehicle is at a standstill is less than or equal to a specified value.

Abstract: A system and method may include receiving, by multiple vessel nodes, RF signals communicated from a target node coupled to a target object. A range measurement between respective vessel nodes and the target node may be determined. A range measurement from at least two of the vessel nodes may be received. Relative geographic coordinates of the vessel and the target node using the range measurements received from the at least two vessel nodes may be determined. The relative geographic coordinates of the vessel and target object may be determined.

Abstract: A semiconductor apparatus is used together with a processor. An A/D converter is configured to be calibratable. A logic circuit periodically supplies a calibration trigger to the A/D converter by means of a count operation using the output of an oscillator.

Abstract: A lidar system can be used to measure a distance to one or more objects in a target region, such as by transmitting light towards the target and then receiving light reflected or scattered from the target. Received light can be stored as charge on storage elements such as capacitors, where received light can be stored on different storage elements depending on a time of arrival of the received light. A reduction in the number of storage elements can be achieved by providing one or more groups of storage elements, where each group of storage elements can correspond to a digit of a time of flight, where the time of flight can be round trip travel time of a light beam travelling from the lidar system to the target region and then back to the lidar system. Each group of storage elements can be arranged in a binary tree of a decimal tree configuration.

Abstract: An analog-to-digital converter includes a ring oscillator having an input for receiving an analog signal, a coarse counter including a maximum length sequence generator having an input coupled to the output of the ring oscillator, a fine counter including a Johnson counter having an input coupled to the output of the ring oscillator, and a difference generator having a first input coupled to the output of the coarse counter, a second input coupled to the output of the fine counter, and an output for providing a digital signal corresponding to the analog signal.

Abstract: A testing device for monitoring a defined profile of a train of vehicles, in particular rail vehicles, including at least one sensor device which is configured to detect compliance or non-compliance with the profile. The sensor device is configured to detect the train in order to improve monitoring of the clearance profile of the train. A vehicle, in particular a rail vehicle, in the form of a train including the testing device and a method for checking a defined profile of a train of vehicles, in particular rail vehicles, are also provided.

Abstract: A count processor counts a zero crossing detection count C. A fraction processor for calculating a fraction Fj (j=1 to L) of the zero crossing detection count on the basis of the digital signal at sampling timings immediately before a zero crossing specifying and when the zero crossing specifying, and computing a fraction processing parameter Gj=Nj?Fj using a zero crossing detection number Nj(0?Nj?N?1) in a period corresponding to a sampling count N necessary for averaging determined in advance. The averaging is performed according to the following formula, where C is the output of the count processor at the end of an averaging period and Gj (j=1 to L) is L fraction processing parameters (L indicates the number of Gj included between the averaging counts N) computed by the fraction processor, and the phase of the digital signal is computed, whereby the phase is calculated on the basis of an input signal digital value obtained by an AD converter.

Abstract: An apparatus for recording distance profiles respectively having a plurality of distance image points comprises: (i) a plurality of transmitters arranged in an array respectively for the transmission of electromagnetic radiation into a recording region; (ii) at least one reception unit for the detection of radiation reflected from the recording region; (iii) an evaluation unit for determining distances of objects at which transmitted radiation is reflected, with the distances each forming a distance image point; and (iv) a deflection unit which deflects the transmitted radiation within a scanning angle region into a scanning direction in order to consecutively generate, per distance profile, a plurality of scanning patterns of distance image points that are displaced against one another in the scanning direction and that each image the transmitter array, wherein at least a few of the distance image points are spaced apart from one another in the scanning direction.

Abstract: The invention relates to installations for fiber optic monitoring of articles, and apparatus and methods for forming such installations, including a modular system and components for forming a fiber optic monitoring installation. Applications of the invention include the monitoring of vessels, chambers, and fluid conduits in industrial processing plants, and the invention has particular application to monitoring large vessels, for example temperature monitoring of vessels used in catalytic reforming processes. Convenient installation on or removal from the article being monitored is achieved by providing a support structure for the fiber optic length, which presents the fiber optic length in a preconfigured orientation suitable for monitoring the article. In a particular embodiment of the invention, the fiber optic length is disposed on a panel in a plurality of dense spiral patterns.

Abstract: In accordance with certain embodiments of the present technology, edges of light drive pulses, which are produced by a light source driver and are used to drive a light source, are aligned with edges of light reference pulses that have a predetermined fixed delay relative to light timing pulses. This way, light pulses are emitted by the light source at precisely known times, so that accurate time-of-flight (TOF) measurements can be made. Additionally, edges of shutter drive pulses, which are produced by a shutter driver and are used to drive a gated light detector, are aligned with edges of shutter reference pulses that have a predetermined fixed delay relative to shutter timing pulses. This way, the gated light detector is shuttered on at precisely known times, so that accurate TOF measurements can be made.

Abstract: A distance measurement apparatus comprises an acquisition section which counts time between a first timing when an output of a photodiode built in a semiconductor laser exceeds a first threshold value because a laser element of the semiconductor laser starts to output laser light and a second timing when the output of the photodiode exceeds a second threshold value higher than the first threshold value because the laser light is reflected by a measurement object and returns to the laser element, and acquires the counted time as flight time of the laser light from a moment when the laser light is output to a moment when the laser light is reflected by the measurement object and returns to calculate a distance from the laser element to the measurement object or displacement of the distance.

Abstract: Methods and devices are provided for determining an operating bias voltage of a photodiode. One example method includes (i) varying a bias voltage of a photodiode; (ii) detecting spurious signals generated by the photodiode while varying the bias voltage of the photodiode; (iii) determining a threshold bias voltage at which a frequency of occurrence of the spurious signals reaches a threshold frequency; (iv) determining an operating bias voltage for the photodiode based on at least the threshold bias voltage; and (v) operating the photodiode with the operating bias voltage in a light-detection and ranging (LIDAR) system.

Abstract: A device for measuring the position of at least one moving object in a three-dimensional grid. The device comprises: at least one optical head comprising an independent laser sources array outputting collimated laser beams, arranged about a central photodetector with a single sensitive cell; at least one movable base with two rotational degrees of freedom whereto said array is secured; and control electronics.

Abstract: A method of and apparatus for generating a depth image are provided. The method of generating a depth image includes: emitting light to an object for a first predetermined time period; detecting first light information of the object for the first predetermined time period from the time when the light is emitted; detecting second light information of the object for the first predetermined time period a second predetermined time period after the time when the light is emitted; and by using the detected first and second light information, generating a depth image of the object. In this way, the method can generate a depth image more quickly.

Abstract: A method of identifying and imaging a high risk collision object relative to a host vehicle includes arranging a plurality of N sensors for imaging a three-hundred and sixty degree horizontal field of view (hFOV) around the host vehicle. The sensors are mounted to a vehicle in a circular arrangement so that the sensors are radially equiangular from each other. For each sensor, contrast differences in the hFOV are used to identify a unique source of motion (hot spot) that is indicative of a remote object in the sensor hFOV. A first hot spot in one sensor hFOV is correlated to a second hot spot in another hFOV of at least one other N sensor to yield range, azimuth and trajectory data for said object. The processor then assesses a collision risk with the object according to the object's trajectory data relative to the host vehicle.

Abstract: A distance measurement method, medium, and apparatus for measuring a distance between the distance measurement apparatus and a target object are provided. The distance measurement method comprises counting pulses of a clock pulse signal having a low frequency during a period from when an optical pulse signal is applied to a target object by a distance measurement apparatus to when the optical pulse signal reflected from the target object is received by the distance measurement apparatus, counting pulses of the clock pulse signal during a period from when the optical pulse signal is received by the distance measurement apparatus to when the received optical pulse signal and the clock pulse signal correspond to each other, and calculating a distance between the distance measurement apparatus and the target object using the counting results. Accordingly, the distance can be measured with high accuracy using the optical pulse signal and the clock pulse signal, thereby reducing costs and power consumption.

Abstract: A pulse data recorder system and method are provided. Upon the arrival or occurrence of an event or signal, the state of a digital switch is set. Upon receiving a pulse from a readout clock, the state of the switch is stored in a buffer memory, and the state of the switch is reset. As the readout clock is run, a time history of the state of the switch is obtained. The pulse data recorder can feature a plurality of unit cells, for use in imaging or other multiple pixel applications.

Abstract: Structures and methods are provided for obtaining depth information regarding a scene being imaged. The scene is illuminated with light having a time varying parameter. Light reflected from the scene is received and values for the time varying parameter associated with different portions of the scene are determined.

Abstract: A distance measurement method, medium, and apparatus for measuring a distance between the distance measurement apparatus and a target object are provided. The distance measurement method comprises counting pulses of a clock pulse signal having a low frequency during a period from when an optical pulse signal is applied to a target object by a distance measurement apparatus to when the optical pulse signal reflected from the target object is received by the distance measurement apparatus, counting pulses of the clock pulse signal during a period from when the optical pulse signal is received by the distance measurement apparatus to when the received optical pulse signal and the clock pulse signal correspond to each other, and calculating a distance between the distance measurement apparatus and the target object using the counting results. Accordingly, the distance can be measured with high accuracy using the optical pulse signal and the clock pulse signal, thereby reducing costs and power consumption.

Abstract: A camera includes a light transmitter configured to transmit light pulses at a first rate, a light receiver configured to receive return signals corresponding to the light pulses transmitted by the light transmitter, and a sampler configured to sample electrical signals corresponding to the return signals received by the light receiver, wherein the sampler is configured to sample the electrical signals at a second rate that is lower than the first rate.

Abstract: An electro-optical distance measuring method for measuring a distance to an object to be measured by receiving a reflected light from the object to be measured, comprising a step of projecting a pulsed laser beam with a predetermined spreading angle from each of two or more known positions so that two or more objects to be measured are commonly included, a step of detecting reflected lights from the two or more objects to be measured for each pulsed laser beam by discriminating the reflected lights for each emitted pulse, a step of measuring distances to the two or more objects to be measured from each of the known points based on the results of detection of the discriminated reflected lights, and a step of measuring coordinate positions of the two or more objects to be measured based on the measured distances.

Abstract: The invention relates to a method for the taking of a large number of distance images comprising distance picture elements, wherein electromagnetic radiation is transmitted in each case in the form of transmission pulses using a plurality of transmitters arranged in an array for each distance image to be taken and reflected echo pulses are detected using a plurality of receivers arranged in an array, with the respective distances of objects at which the transmission pulses are reflected and forming a distance picture element being measured by determining the pulse time of flight, wherein a plurality of individual measurements are carried out using a time measuring device connected after the receiver array for each distance image to be taken, in which individual measurements a respective pulse chain is processed which includes a logical start pulse derived from the respective transmission pulse and at least one logical receiver pulse formed from an echo pulse or a noise pulse, wherein the logical receiver puls

Abstract: A method of determining a distance to an object is presented. A first photon and a second photon are simultaneously generated. The first photon is reflected off an object. The second photon is directed to an optical cavity. An arrival of the first photon is correlated with an arrival of the second photon, and the distance to the object is at least partially determined using the correlation.

Abstract: A laser range finder, including a transmitter, a receiver, a timing-counting module, and a processor is provided. The transmitter transmits a laser signal toward a target, and a reflected signal is reflected from the target, whereby a real fly time is defined. The time-counting module generates a plurality of timing units to measures the real fly time to obtain a measured fly time. The processor generates a distance value based on the measured fly time.

Abstract: An apparatus for detection and analysis of optical systems. Prior art systems exploit the phenomenon of photon scattering in order to range the distance of objects from the ranging apparatus. However, no information other than the distance of the target object is obtained from such systems. There is therefore provided an apparatus that exploits the technique of single photon counting and the phenomenon of retro reflection to provide information about a target optical system. Such information can be analysed and compared against known optical systems to provide a means of identification. Alternatively such information can be used as a method of quality control when constructing precision optical instruments such as telescopes or microscopes.

Abstract: A method and apparatus for generating charge from a light pulse. In one example, a light sensor includes an active region for generating an electric charge in response to a light pulse. A drift region is formed within a substrate and receives the electric charge from the light sensor. A spatial charge distribution is produced within the drift region in response to an electric field. The drift region includes an outer edge and an inner edge. The volume of the drift region decreases from the outer edge to the inner edge.

Abstract: A method and apparatus for the characterization of optical pulses and modulators includes modulating, using a modulator, a train of optical pulses, measuring a spectrum of the modulated train of optical pulses, recording the measured spectrum as an entry in a spectrogram at a position in the spectrogram corresponding to a relative delay between the modulation and the train of optical pulses, incrementing the relative delay, and repeating the above steps until the accumulated relative delay is equal to the period of the spectrogram. The train of optical pulses and the modulator are then characterized using the measured spectra recorded in the spectrogram.

Abstract: The invention relates to a method of measuring the distance between a fixed point and an object, by the steps of: a) transmitting a light pulse (11) from the fixed point at a selected instant of transmission; b) periodically scanning of light intensity received at the fixed point and continuously storing, as a set of received scanned signal values, the scanned values at the scanning rate during a predetermined measuring time window (13) embracing the instant of reception of the light pulse reflected from the object; c) repeating steps a) and b) N number of times in order to obtain N number of sets of received signal values; d) summing the individual stored sets of received scanned signal values, set by set, to a summed scanned value set during a calculating window (14) following the N measuring time windows (13); e) repeating steps a) through d) in order to obtain a further summed scanning value set, whereby during or following step d) the further summed scanned value set is added, scanned value set by s

Abstract: Technology is disclosed for measuring distances. A measurement device emits a beam that reflects on the surface of an object. The measurement device determines the distance to the object, based on the time of flight of the beam from transmission to capture by the measurement device. The measurement device derives feedback reference pulses from pulses in the emitted beam and injects them into the device's receive path—creating a receive waveform that includes one or more feedback reference pulses and corresponding pulses in the return beam. The device uses the pulses in the waveform to measure time of flight. The measurement device can attenuate the feedback reference pulses to intensities similar or equal to the intensities of the return pulses. The measurement device can include a histogram processor that collects waveform samples at varying comparison thresholds.

Abstract: FIG 1 of the drawings has been amended to include arrows 12a and 12b. The word “laser”, the arrow symbol underneath the word “laser” and the partial sinusoidal symbol adjacent the word “laser”have all been deleted. In addition, the word “photodetector” deleted and a dashed line circumscribing the photodetector componants has been added along with reference numeral 25. Reference numeral 24 has been added to denote the photodiode. Finally, the photodiode symbol associated with oscillator apparatus 12 has been changed to simply indicate a “Gain Cavity” box. The attached “Replacement Sheet(s)”of drawings include changes to FIG. 1. The attached “Replacement Sheet(s),”which include(s) FIG(S.) 1 and 2, replace the original sheet(s) including FIG(S.) 1 and 2.

Abstract: The present invention is a method and an apparatus of a laser range detector, a delay circuit is comprised for generating a plurality of delay signals. With the delay signal, the precision of detecting could be improved without faster clock signals or higher power consumption.

Abstract: High dynamic range brightness information is acquired by inputting detection current to a high (adjustable) gain resettable integrator whose output V(t) is compared to a Vth threshold by a comparator whose output is counted by a reset counter as V(t)≧Vth. When a desired count is attained, data acquisition ends, the counter is read, and the entire circuit is reset. A TOF data acquisition circuit includes first and second sequences of series-coupled delay units, and a like number of latch units coupled between respective delay units. A phase discriminator compares output from each chain and feedback a signal to one of the chains and to a comparator and can equalize delay through each chain. A control voltage is coupled to the remaining chain to affect through-propagation delay time. The latch units can capture the precise time when V(t)≧Vth. Successive measurement approximation can enhance TOF resolution.

Abstract: A method and apparatus for resolving relative times-of-arrival of a plurality of light pulses includes a plurality of drift-field detectors. Each drift-field detector includes a light sensor and a semiconductor drift region. Each light sensor generates an electrical charge from at least one of the plurality of light pulses. Each semiconductor drift region receives the electrical charge from its respective light sensor and, pursuant to an electric field therein, produces a spatial charge distribution. The spatial charge distribution for each of the semiconductor drift regions is stored in an analog storage device associated therewith. The relative positions of the charge distributions in the semiconductor drift regions are used to calculate the relative times-of-arrival of the light pulses.

Abstract: In a laser rangefinder receiver, a return signal from a light-sensitive detector is passed through a high-pass filter, and is then processed in two separate circuit paths, a “signal” path and a “noise” path. The “signal” path employs a time-variable offset scheme to control receiver sensitivity. The “noise” path measures noise in the return signal, and maintain a noise-based threshold independent of the time-variable sensitivity of the “signal” path. No interstage coupling capacitors are employed, which contributes greatly to the receiver's quick saturation recovery.

Abstract: In a distance measuring device, reflected pulsed light beams with respect to one transmitted light beam are amplified by plural amplifiers (22a, 22b) of different gains. The retroreflection times of the reflected pulsed light beams are detected by retroreflection time detectors (30a, 30b) respectively connected to the amplifiers. Based on outputs of the retroreflection time detectors, distance calculator (40) judges the overlapping state of the reflected pulses and the power of reflection from first pulse widths of the reflected pulsed light beams, selects a distance calculating method in accordance with the state, and outputs distance measurement data of high reliability.

Abstract: A three-dimensional time-of-flight (TOF) system includes a low power optical emitter whose idealized output S1=cos(&ohgr;·t) is reflected by a target distance z away as S2=A·cos(&ohgr;·t+&PHgr;), for detection by a two-dimensional array of pixel detectors and associated narrow bandwidth detector electronics and processing circuitry preferably fabricated on a common CMOS IC. Phase shift &PHgr; is proportional to TOF or z, z=&PHgr;·C/2·&ohgr;=&PHgr;·C/{2·(2·&pgr;·f)}, and A is brightness. &PHgr;, z, and A are determined by homodyne-mixing S2 with an internally generated phase-delayed version of S1, whose phase is dynamically forced to match the phase of S2 by closed-loop feedback. Idealized mixer output per each pixel detector is 0.5·A·{cos(2&ohgr;·t+&PHgr;)+cos(&PHgr;)}.

Abstract: A method and system are provided for measuring water current direction and magnitude. A plurality of beams of radiation are transmitted radially outward from a location above a body of water. Each beam is incident on the water's surface at an angle with respect thereto. Each beam experiences a Doppler shift as a result of being incident on the water's surface such that a plurality of Doppler shifts are generated. Each Doppler shift is measured with the largest one thereof being indicative of water current direction and magnitude.

Abstract: A three-dimensional imaging range finder is disclosed using a transmitted pulse reflected from a target. The range finder includes a pixel sensor for receiving light from the target and the reflected pulse. A global counter is provided for determining a time-of-flight value of the transmitted pulse by providing accurate count data to pixel memories. A processing circuit, which is coupled to the pixel sensor and the global counter, extracts the reflected pulse received by the pixel sensor, and stores the time-of-flight value upon extracting the reflected pulse. The pixel sensor provides a luminance signal and the processing circuit includes a high pass filter to extract the reflected pulse from the luminance signal.

Abstract: A three-dimensional imaging system is fabricated on a single IC. The system includes a two-dimensional array of pixel light sensing detectors and dedicated electronics and associated processing circuitry, all preferably fabricated on a single IC using CMOS fabrication techniques. The system includes a detector array comprising a plurality of pixel photodiodes and photodiode circuits, wherein each pixel photodiode acquires delay time data and pulse brightness data simultaneously. The system emits an energy pulse at time t0 and a fraction of the energy is returned to the array by a target object. Photodiodes in the array output a brightness signal B(t) that is integrated. An elapsed time ET from t0 to when said B(t) attains a predetermined threshold value is determined, where the slope of B(t) is B/PW, where B is B(t) after integrating over a time equal to the emitted pulse width PW.

Abstract: A method of calibrating a timebase in a digitizing instrument estimates the frequency of the clock signal from the clock generator that clocks a coarse delay counter in a strobe generator. The dynamic range of the interpolator in the strobe generator is defined in digital-to-analog converter code values as a function of the clock signal period. A linear horizontal look-up table of equally spaced digital-to-analog converter code values is generated over the defined dynamic range of the interpolator. Residual nonlinearities of the interpolator over the defined dynamic range of the interpolator are characterized and scaled to digital-to-analog converter code values. The digital-to-analog converter code values of the characterized residual anomalies are combined with the digital-to-analog converter code values of the linear horizontal look-up table to generate a horizontal look-up table having DAC code value compensating for the nonlinearities of the interpolator.

Abstract: A high precision laser range finder comprises an APC loop for eliminating a timing jitter problem due to different reflections on a target. The APC loop comprises a laser receiver, a peak holding circuit, an integrator and a high voltage generator. The peak holding circuit is connected with the laser receiver for detecting a signal strength outputted from the laser receiver. The high voltage generator provides the laser driver and laser receiver with voltage so as to control the strength of the emitted laser pulse signal of the laser driver and the gain of the avalanche photo-detector. The integrator is used to eliminate the steady error in the APC loop. Furthermore, a time to amplitude converting circuit comprises an AJD converter for obtaining a distance data and then filtering in a microprocessor to increase the measurement accuracy.

Abstract: A highly precise range measurement instrument is made possible through the use of a novel and efficient precision timing circuit which makes use of the instruments internal central processing unit crystal oscillator. A multi-point calibration function includes the determination of a “zero” value and a “cal” value through the addition of a known calibrated pulse width thereby providing the origin and scale for determining distance with the constant linear discharge of capacitor.

Abstract: A three-dimensional imaging range finder is disclosed using a transmitted pulse reflected from a target. The range finder includes a pixel sensor for receiving light from the target and the reflected pulse. A global counter is provided for determining a time-of-flight value of the transmitted pulse. A processing circuit, which is coupled to the pixel sensor and the global counter, extracts the reflected pulse received by the pixel sensor, and stores the time-of-flight value upon extracting the reflected pulse. The pixel sensor provides a luminance signal and the processing circuit includes a high pass filter to extract the reflected pulse from the luminance signal.

Abstract: A three-dimensional imaging system includes a two-dimensional array of pixel light sensing detectors and dedicated electronics and associated processing circuitry fabricated on a common IC using CMOS fabrication techniques. In one embodiment, each detector has an associated high speed counter that accumulates clock pulses in number directly proportional to time of flight (TOF) for a system-emitted pulse to reflect from an object point and be detected by a pixel detector focused upon that point. The TOF data provides a direct digital measure of distance from the particular pixel to a point on the object reflecting the emitted light pulse. In a second embodiment, the counters and high speed clock circuits are eliminated, and instead each pixel detector is provided with a charge accumulator and an electronic shutter.