101results about How to "Long measuring distance" patented technology

The invention discloses a distributed optical fiber sensing device based on a chaotic laser coherence method, and a measurement method of the distributed optical fiber sensing device. Chaotic laser light which is emitted from a chaotic laser is divided into detection light and reference light; the detection light is amplified by a light amplifier and then emitted into a sending optical fiber through an optical circulator, and a backward Brillouin scattering light signal is generated in the optical fiber; the Brillouin scattering light signal is amplified by the light amplifier, de-noised by a tunable light filter and then emitted into an optical fiber coupler; the optical length of the reference light is regulated by a variable light delay line, and interferes with the backward Brillouin scattering light signal which is generated by the detection light at different positions in the sensing optical fiber in the optical fiber coupler; an interference beat frequency signal is detected by a photoelectrical detector; and Brillouin gain spectra at different lengths are obtained through a data acquisition device and a signal processing device and then output to a display device, so strain or temperature sensing detection is realized.

The invention relates to monitoring technology of power transmission lines, in particular to technology for monitoring ice coating and waving states of the power transmission lines. The invention discloses a method and a device for monitoring the power transmission line by using fiber sensors in real time. The method for monitoring the power transmission line is characterized by comprising the following steps: arranging the fiber sensors along the power transmission line to detect characteristic parameters of different positions of a lead; and judging the state of the power transmission line according to the analysis of the characteristic parameters. The device for monitoring the power transmission line comprises the fiber sensors and a signal transmitting and processing system, and is characterized in that the fiber sensors are arranged along the length direction of the power transmission line and used for detecting and transmitting the characteristic parameters of the different positions of the power transmission line. The method and the device are used for monitoring the ice coating and waving states of the power transmission lines, can fully exert the advantages of the fiber sensors to carry out multi-parameter real-time on-line detection, and have the characteristics that the device has long service life and can work for long time reliably under on-site severe environment conditions.

A radar level gauge system for determining the filling level of a filling material in a tank is disclosed. The system comprises an antenna device for emitting measuring signals towards the surface of the filling material and a receiver device for receiving echo signals from the tank. Further, the system comprises processing circuitry for determining the filling level of the tank based on said echo signal, wherein said processing circuitry is adapted to amplify the received echo signals in dependence of the distance from which the echo signals originates, in such a way that an echo signal from a lower filling level is more amplified than an echo signal from a higher filling level. The processing circuitry is adjustable to optimize the amplification of the echo signal based on the height of the tank. A corresponding processing circuitry and method of operation is also disclosed.

A laser range finder 100 includes: a light source 10 emitting light from a linear light-emitting portion 10a with making a divergent angle of the light larger in a transversal direction of the light-emitting portion 10a than in a longitudinal direction thereof; an objective lens 30 projecting the light onto a target object and converging reflection light; a partial reflection member 20 disposed between the light source and the objective lens and having a partial reflection surface 21 composed of a transmitting area 21a transmitting light emitted from the light source and receiving areas 21b reflecting reflection light; and a photodetector 40 detecting the reflection light reflected by the receiving areas; wherein the light source and the partial reflection member are disposed with making the longitudinal direction of the light-emitting portion 10a disposed substantially perpendicular to a longitudinal direction of the transmitting area 21a as seen along an optical axis.

The invention discloses an optical fiber distributed train monitoring system. The system comprises a rail roadbed and a main railway track arranged at the top of the rail roadbed, wherein a first branch railway track and a second branch railway track are connected with two sides of the main railway track respectively, the main railway track is provided with an interval detecting optical cable outside a station, a station area detecting optical cable with one end connected with the interval detecting optical cable is arranged between the first branch railway track and the second branch railway track, station area annular detecting optical cables are arranged on the station area detecting optical cable and located at the main railway track, the first branch railway track and the second branch railway track, and an interval running train runs on the main railway track. The system has the advantages that a detection front-end device is passive and resists electromagnetic interference, so that the system can still work normally and guarantee running safety of the train under the condition that other electric train control systems cannot work due to outage faults.

A radar position selection method based on a three dimensional laser scanner and a GIS (Geographic Information System) is characterized in that the three dimensional laser scanner and a portable lifting platform are adopted, auxiliary devices such as an RTK and a target are matched for use, position three dimensional point cloud data can be quickly and accurately got, and high-precision DEM data are generated after data processing; on this basis, a skyline tool with a three dimensional space analysis function of the GIS is used to generate a skyline, then heights of various points of the skyline are extracted according to the skyline and imported topographic data, shielding angle data are generated, and a radar shielding angle figure and a radar plane detection range figure are generated according to the shielding angle data and radar parameters; a sight line analysis tool of the GIS is used to generate a visible line in a certain direction at an observation point, heights of various points of the visible line are extracted according to the visible line and the imported topographic data, so as to generate a cross-section diagram, undulation of a radar reflection area is analyzed, quantified undulation data are obtained, and a proper radar position erection location is favorably selected on this basis.

A radar level gauge system for determining the filling level of a filling material in a tank is disclosed. The system comprises an antenna device for emitting measuring signals towards the surface of the filling material and a receiver device for receiving echo signals from the tank. Further, the system comprises processing circuitry for determining the filling level of the tank based on said echo signal, wherein said processing circuitry is adapted to amplify the received echo signals in dependence of the distance from which the echo signals originates, in such a way that an echo signal from a lower filling level is more amplified than an echo signal from a higher filling level. The processing circuitry is adjustable to optimize the amplification of the echo signal based on the height of the tank.A corresponding processing circuitry and method of operation is also disclosed.

The invention relates to a vortex-induced vibration test, measurement and analysis system for a deep-sea flexible riser model in the technical field of oceanographic engineering, which is characterized in that the system consists of an optical fiber grating sensor module, an optical fiber expanding slot, an optical fiber demodulator, a wireless transmission module and an optical signal data acquisition device which are sequentially cascaded with each other, wherein the optical fiber grating sensor module is connected with the riser module, the optical fiber expanding slot, the optical fiber demodulator, the wireless transmission module and the optical signal data acquisition device are arranged on a trailer, the optical fiber grating sensor module generates optical signals, the optical signals enter the optical fiber demodulator through the optical fiber expanding slot, the optical fiber demodulator demodulates the optical signals into digital signals, and the optical signal data acquisition device records, analyzes and stores the digital signals. The vortex-induced vibration test, measurement and analysis system for the deep-sea flexible riser model can realize the remote control acquisition of strain and stress situation generated by riser vortex-inducted vibration and can analyze and store the data in real time.

The invention relates to a liquid flow non-magnetic detector and a detection method thereof. The detector comprises a microprocessor unit, a power supply control circuit and an excitation control circuit which are connected with the microprocessor unit, and an LC oscillating circuit, an LC oscillating detection circuit, an envelope detection circuit and a trigger circuit which are connected in sequence, wherein the output ends of the power supply control circuit and the excitation control circuit are respectively connected with two ends of the LC oscillating circuit, and the trigger circuit is connected with a timer capture input end of the microprocessor unit. The LC oscillating circuit is located above an impeller comprising an insulating area and a conducting area. The detection method comprises the steps that an oscillating wave output by the LC oscillating circuit is processed by the LC oscillating detection circuit, the envelope detection circuit and the trigger circuit and then is subjected to timer capture by the microprocessor unit, the position changes of the conducting area and the insulating area of the impeller are judged, and finally liquid flow is calculated. The measuring distance is larger, the application range is wide, the singlechip microcomputer selection limitation is less, the cost is reduced, and the universality is good.

The invention relates to the field of automobile collision experiment equipment, and in particular relates to a measurement device used for obtaining dummy location information in an automobile collision experiment. The dummy location measurement device comprises a measuring instrument which is used for measuring the location of a dummy placed in the automobile, and a fixing seat which is respectively connected with the automobile and the measuring instrument. The fixing seat of the dummy location measurement device is respectively connected with the automobile and the measuring instrument, so as to provide a datum mark for operation of the measuring instrument, reduce the error generated by different measuring operators, and prevent the measuring error due to shake of the measuring instrument. A measuring instrument connecting part comprises a fixture block with a measuring instrument insert hole; the measuring instrument can be inserted into the measuring instrument insert hole and turn in the hole; a bolt hole is formed at the side wall of the fixture block; and a bolt is inserted into the bolt hole to compact the measuring instrument which is inserted into the measuring instrument insert hole, so as to firmly fix the measuring instrument with the fixing seat.

There are provided a small distance measuring device which enables an accurate distance measurement and has a wide range of measurable distances and a projector which is provided with the distance measuring device.A projector includes a light source unit, a light source side optical system for guiding light from the light source unit to a display device, the display device, a projection side optical system for projecting an image emitted from the display device on to a screen, and a distance measuring device and has a projector control unit for controlling the light source unit and the display device, and the distance measuring device includes a distance calculating part for calculating distances to a plurality of point on the screen and a mean distance thereof, and the projector control means includes an inclination angle calculating part for calculating an inclination angle of the screen based on the distances to the plurality of points on the screen calculated by the distance calculating part and a distortion correcting part for preparing image data of a projected image which has been corrected for distortion from information calculated by the distance calculating part 45 and the inclination calculating part.

The invention discloses a radio frequency identification device (RFID)-based device and a method for measuring rotation speed. The RFID-based device and the method for measuring rotation speed comprises a RFID reader, a linear polarized tag which is used with the RFID reader and a reader antenna, wherein the linear polarized tag is attached to an object to be measured and synchronously rotates with the object to be measured. The RFID reader sends out signals through the reader antenna, the linear polarized tag returns the signals, the RFID reader does the operation after receiving the signals, and the rotation speed is obtained. By means of the RFID-based device and the method for measuring the rotation speed, the rotation speed measurement in contact-less closed environment is achieved, the transmitting power of a card reader is improved, long-distance rotation speed measurement can be achieved, the implementation is easy, and the previous protocol not need to be changed.

The invention discloses a method for measuring by means of an intelligent terminal and the intelligent terminal. The method includes the following steps of drawing scales on a screen and displaying original scale values ranging from 0 to L, aligning a certain scale to a measurement starting point, moving the intelligent terminal to the direction of a measurement end point if the total length needing to be measured is larger than L, obtaining the total displacement S of the intelligent terminal in the horizontal direction in real time, displaying the scale values ranging from S to S+L on the screen dynamically in real time, and obtaining a measurement value according to the scale value aligned to the measurement end point when the intelligent terminal moves to the measurement end point. Therefore, when the intelligent terminal measures, the length limit of the intelligent terminal itself can be eliminated, a larger length distance can be measured, a user can flexibly, easily and conveniently measure lengths, heights and widths of different objects and the distance between two points by means of the intelligent terminal, the function of the intelligent terminal is enriched, use convenience of the intelligent terminal is improved, and use experience of the user is optimized.

The invention discloses a remote displacement measurement device, system and method having a clutter inhibition function. The system comprises a central controller, at least one main measurement device and at least one secondary measurement device, wherein the main measurement device is used for sending an emission signal to the secondary measurement device, receiving a forwarding signal emitted by the secondary measurement device and calculating relative displacement according to the received forwarding signal, the secondary measurement device is used for receiving the emission signal of the main measurement device and emitting the forwarding signal, and the main measurement device and the secondary measurement device both have two sets of polarized orthogonal antennas. When the main measurement device emits the signal, natural landform scattered strong clutter signals and a polarized direction of an emission antenna are consistent, polarized characteristics of a reception antenna and the emission antenna are in polarized orthogonal, so the reception antenna has the quite strong inhibition effect on background clutter, so system precision is improved; during cofrequency transmit-receiving, an acquired transmit-receiving isolation degree can be greater compared with a single antenna and the double polarized antennas, a large measurement distance is acquired through enhancing emission power.

The invention provides a fiber bragg grating vibration measurement system based on a pulse coding and edge filtering method and belongs to the technical field of fiber bragg grating sensors. The system comprises a narrow linewidth laser, a pulse signal generator, an electrooptical modulator, a circulator, a single mode fiber, a fiber bragg grating, a photoelectric detector and a digital signal processing unit, wherein an output end of the narrow linewidth laser is connected with an optical input end of the electrooptical modulator, an output end of the pulse signal generator is connected witha radio frequency input end of the electrooptical modulator, an output end of the electrooptical modulator is connected with a first port of the circulator, a second port of the circulator is sequentially connected with the single mode fiber and the fiber bragg grating, the photoelectric detector is connected with a third port of the circulator, and the digital signal processing unit is connectedwith the photoelectric detector. The fiber bragg grating vibration measurement system prepared according to pulse coding principles and edge filtering principles has monitoring and measurement functions of an OTDR (optical time domain reflectometer), and the conflict that the sensing distance and the spatial resolution in an OTDR system cannot be improved simultaneously is eradicated.

The invention relates to a laser positioning distance measuring tool. The laser positioning distance measuring tool comprises a precise sliding guide rail, a left sliding seat and a right sliding seatwhich are transversely arranged, wherein the left sliding seat and the right sliding seat are respectively in sliding connection with left and right ends of the precise sliding guide rail, a right end of a top surface of the left sliding seat is provided with a laser distance measuring instrument, one side of the left sliding seat is provided with a vertical left laser lamp, a left end of the topsurface of the left sliding seat is provided with a left power supply module, the left laser lamp is connected with the left power supply module, a left end of a top surface of the right sliding seatis provided with a right power supply module, one side surface of the right power supply module opposite to the laser distance measuring instrument is provided with a laser reflection board, one sideof the right sliding seat is provided with a vertical right laser lamp, the right laser lamp is connected with the right power supply module, laser emission ends of the left laser lamp and the rightlaser lamp are arranged in the same direction, and an interval between the left laser lamp and the right laser lamp is equal to an interval between the laser distance measuring instrument and the laser reflection board. The laser positioning distance measuring tool has advantages of simple structure, convenient operation, low production cost and high measurement precision.

The invention relates to an oil-gas pipeline monitoring system based on optical fiber. The oil-gas pipeline monitoring system is characterized by comprising a monitoring center, a plurality of monitoring substations, an optical fiber sensing analyzer, a laser device, a sensing optical cable, an fiber bragg grating sensor and an optical signal processor, wherein the monitoring center is provided with a master control server and a display screen; a controller monitoring camera, an alarm device, a sound pickup device and a sound amplification device are arranged in each monitoring substation; the controllers are connected with the monitoring cameras, the alarm devices, the sound pickup devices, the sound amplification devices and the optical signal processor in sequence; the optical signal processor is connected with the fiber bragg grating sensor through optical fiber. Through the oil-gas pipeline monitoring system, the fiber bragg grating sensor is arranged on an oil-gas conveying pipeline; the stress state of the pipeline is analyzed by monitoring the stress change of the pipeline and is warned in advance, so that operators can maintain the pipeline in time, so that the danger caused by damage to the pipeline and the leakage of the oil and the gas can be reduced.

The invention provides an ultrasonic distance measuring device. The ultrasonic distance measuring device comprises a control unit for outputting recurrent pulse strings, an ultrasonic wave transmitting and driving circuit for converting the recurrent pulse strings into recurrent sine wave signals, an intermediate frequency transformer for performing boosting processing on the recurrent sine wave signals, an ultrasonic transmitting-receiving integrated probe for transmitting ultrasonic signals to obstacles after being excited by the signals, receiving ultrasonic signals reflected by the obstacle and producing voltage signals corresponding to the reflected ultrasonic signals, a signal amplification circuit, a band-pass filtering circuit, a signal comparison circuit for converting filtered voltage signals into recurrent pulse signals, wherein the signal amplification circuit and the band-pass filtering circuit are respectively used for amplifying and filtering the voltage signal, and the control unit is further used for obtaining a measured distance according to output recurrent pulse strings and the recurrent pulse signals output by the signal comparison circuit. Compared with the prior art, the distance measured by the ultrasonic distance measuring device is large.

The invention provides a precise synchronization-unrequired coal mine underground spread spectrum accurate ranging method and a device. According to the precise synchronization-unrequired coal mine underground spread spectrum accurate ranging method, a parallel and tracking loop-free pseudo-noise code synchronization accurate measurement algorithm is adopted, such that higher time resolution can be obtained based on rough synchronization without precise synchronization process required, and therefore, ranging pseudo code speed can be decreased, and bandwidth occupied by ranging pseudo codes is limited below 100MHZ, and thus, meter-level positioning accuracy can be achieved. The device for realizing the method comprises a communication control module and a wireless response module; the communication control module, adopting a high-performance FPGA as a core processor, mainly comprises a transmitter and a receiver; and the wireless response module de-spreads received signals through adopting a search-track-free synchronization mode without a separate processor required. The precise synchronization-unrequired coal mine underground spread spectrum accurate ranging method and the device of the invention can inhibit serious electromagnetic interference under a coal mine, and are advantageous in robust hardware designs, redundant algorithms, high-accurate ranging and strong real-time property, are suitable for a coal mine underground personnel precise positioning system.

The invention provides an underground pipeline monitoring system and method based on distributed optical fiber sensing. An armored photoelectric composite cable arranged on the outer side of an underground pipeline , a high-resolution optical camera with a night vision function and mounted along an underground pipeline, and an automatic monitoring and early warning system and a DSS / DTS / DAS composite distributed optical fiber sensing modulation and demodulation instrument which are arranged in a monitoring station along the line are used to construct a long-term real-time monitoring system forthe temperature, vibration and strain distribution change along the underground pipeline based on distributed optical fiber sensing. Real-time effective anti-theft, anti-excavation damage, fireproof,anti-natural and geological disaster early warning monitoring is carried out on underground pipelines and oil and gas conveying pipelines; loss can be effectively avoided or reduced; long-term stable,safe and reliable work of the underground pipelines is guaranteed; and indispensable means, systems and methods are provided for scientific management of the underground pipelines and improvement ofthe use efficiency.

The invention discloses a laser nonlinear tuning effect compensation system for an optical frequency domain reflectometer (OFDR). The method comprises: firstly, connecting an acousto-optic frequency shifter (AOM) into an interference arm of an OFDR auxiliary interferometer to shift the frequency of light waves, and increasing the beat frequency signal frequency of the auxiliary interferometer; converting the beat frequency signal into an alternating current signal through a photoelectric detector, and correcting a measurement signal of the main interferometer by taking a zero crossing point ofthe signal as a reference point. The correction process comprises five steps of solving zero-crossing points, calculating a frequency interval between every two zero-crossing points, eliminating additional frequency introduced by AOM, solving a correction coefficient and correcting abscissa. The correction signal obtained in the process is used for OFDR detection, the influence of the nonlinear tuning effect of a light source can be effectively overcome, and the spatial resolution of the OFDR is improved.

The invention discloses a Brillouin distributed optical fiber sensing system which comprises Brillouin scattering light (1), a photoelectric detector (2), a signal preprocessing circuit (3), a high speed AD collecting circuit (4), an arbitrary coded pulse circuit (5), an acousto-optic driver (6), a data storage circuit (7), a microwave source (8), a microwave frequency sweeping control circuit (9), an FPGA logic control circuit (10), an ARM and upper computer interface circuit (11) and an upper computer (12). The Brillouin distributed optical fiber sensing system provides coded pulse drive signals needed by a Brillouin optical time domain analysis meter, and carries out collection and processing on the Brillouin scattering optical signals generated by an optical subsystem, temperature and strain information is demodulated from the Brillouin scattering optical signals, and the Brillouin distributed optical fiber sensing system is strong in pertinence, high in integration level and low in cost, and achieves high measuring accuracy and long measuring distance.

The invention relates to a distributed optical fiber Raman temperature monitor for a granary based on the pulse coding technology for granary safety detection, and belongs to the field of grain reserve. The temperature monitor is characterized in that the temperature monitor comprises a temperature measurement optical cable in the granary; a temperature measurement demodulating module which consists of a laser light source, an acousto-optic pulse modulator, an optical fiber bidirectional coupler, an optical wavelength division multiplexer, an avalanche diode, an amplifier, a signal processor and a PC host; a communication module, an alarm module and a remote client for monitoring. When the laser light source injects optical pulses into the optical fiber, a part of Raman scattering light closely related to the temperature can be generated and positioned through the optical time domain reflection technology, the signal-to-noise ratio is improved through the simplex cyclic encoding and decoding technology, and the temperature of a point to be measured can be obtained. The invention provides a safe, practical and high-sensitivity granary temperature measurement monitor, aiming at solving the problems of time and labor waste, low accuracy, electronic monitoring short circuit, limited sensing points, easiness in causing a fire and the like of manual inspection in the granary at present.

A non-invasive method for determining a concentration of a gas component in a gas mixture contained in a spacing of a glass unit having at least two glass sheets spaced apart from each other and forming the spacing. One or more light beams is applied at an angle to the surface of the glass unit, wherein the wavelength of the emitted light beam is varied around or over the at least one absorption line of the interest gas component. The light beams transmitted through or reflected from at least one surface or interface locating at the opposite side of the spacing are collected by a detector and non-linear variations in the intensity of the transmitted or reflected light beams over an absorption line of the interest gas is then component determined. The concentration of the gas component to be measured is determined based on the non-linear variations in the intensity.

The invention discloses an acoustic wave ranging method and device, and relates to the technical field of measurement. The problems of poor measurement reliability and wind speed influence, which arecaused by echo loss and channel interference and the problem of ranging error caused by trigger phase shift caused by echo fluctuations in the existing acoustic wave ranging technology are overcome. According to the technology, a transmitting end sends encoded acoustic waves in a detection frame encoding format and starts effective measuring wave counting; a receiving end is in an acoustic wave receiving state after receiving a pilot code; after a frame start delimiter is detected, effective measuring wave counting is started; when a first effective measuring wave is received, a level handshake signal is sent to the transmitting end; after receiving the level handshake signal, the transmitting end sends a frame end delimiter, stops counting, and counts and transmits the number of the effective measuring waves; after receiving the frame end delimiter, the receiving end counts the number of actually received effective measuring waves; and if two numbers are equal, distance is calculatedbased on the relationship between the counted number of the effective measuring waves and the wavelength.

The invention belongs to the technical field of sensors and especially relates to a TOF (Time of Flight) three-dimensional distance measuring sensor. The sensor includes a TOF processing chip composed of a distance calculating unit, a transmission driver and a receiving and processing circuit. The transmission driver is connected with an LED array light source. The receiving and processing circuit is connected with a CMOS light sensing chip. A transmitting lens is arranged in the transmitting direction of the LED array light source. A receiving lens is arranged in the receiving direction of the CMOS light sensing chip. The sensor provided by the invention is small in size, high in measurement precision, large in measurement distance; the actual measurement distance can reach 15 to 25 m. Besides, measurement results of the sensor provided by the invention are insusceptible to interference of vibration signals, sound signals and the like, so that product stability is improved substantially. Also, through effective control of frequency, power and divergence angle of the light source, the measurement results are insusceptible to influence of environmental light environments. The sensor provided by the invention can work stably in scenes of snowfield, desert and the like no matter in night or day, summer or winter. Therefore, requirements of automobile application scenes can be met.

The invention relates to the technical field of sensors, particularly to a Mach-Zehnder interference bending sensor. The Mach-Zehnder interference bending sensor includes a signal source module, an interference sensing module and a spectrum display module, one end of the interference sensing module is connected to the signal source module, the other end of the interference sensing module is connected to the spectrum display module, the signal source module comprises a semiconductor laser amplifier unit and a drive circuit unit, the interference sensing module includes a single-mode fiber and athree-core fiber, and fiber cores in the single-mode fiber and the three-core fiber are connected together in a staggered welding mode through a fiber fusion splicer. By adoption of such structural setting, the Mach-Zehnder interference bending sensor can realize measurement of a high-sensitivity bending direction when used for measuring target bending, since a transmitted optical signal is not affected by electromagnetic interference, the stability of the sensor is better than that of a sensor of the same kind which performs monitoring by electric signals at present, and due to adoption of afiber structure, the sensor has a small size and long measuring distance, and can monitor multiple parts of a target at the same time.

The invention provides a downhole strain distribution monitoring system based on distributed optical fiber sensing and a monitoring method of the downhole strain distribution monitoring system based on distributed optical fiber sensing. Armored optical cables are bound to the outside of sleeves of vertical wells, inclined wells or horizontal wells and are permanently fixed with cementing cement, the armored optical cables are bound and fixed to the outside of a coiled tubing by a metal clip, a long-term strain monitoring and sensing unit for oil and gas production wells, water injection wellsand monitoring or observation wells is constructed, the long-term strain monitoring and sensing unit and a distributed strain sensing and distributed temperature sensing (DSS / DTS) composite modulationand demodulation instrument near a wellhead together form the downhole strain distribution change dynamic monitoring system based on distributed optical fiber sensing and the monitoring method, the long-term stable, safe and reliable work of the oil and gas production wells, the water injection wells and the monitoring or observation wells can be effectively ensured, and the indispensable means,system and method are provided for scientific management of oil and gas reservoirs and enhanced recovery efficiency.

Provided are a spiral spring wire pulling liquid level measurement instrument and a measurement method thereof. A wave detecting tube higher than the highest liquid level is installed in a detected liquid medium, a floater is installed in the wave detecting tube, a spiral spring is installed in a spring box installed in an observation place, a wire wheel at the end of a spiral spring shaft is connected with the floater through a pulling wire, and when the liquid level of the detected liquid medium descends, the floater descends to drive the wire wheel to rotate through the pulling wire, and the spiral spring is tightened. An encoder or a gear transmission device is installed at the end of the spiral spring shaft, an encoder output is connected with an electronic display through an electric signal, and an output of the gear transmission device is connected with a mechanical reading table. On the contrary, when the liquid level of the detected liquid medium ascends, the floater ascends, the spiral spring takes up and tightens the pulling wire through the wire wheel, and the spiral spring shaft rotates to perform displaying of the electronic display or reading of the mechanical reading table through the output of the encoder or the gear transmission device as well. The spiral spring wire pulling liquid level measurement instrument is simple in structure, convenient to install, long in measurement distance, wide in application range and good in safety performance.

A laser range finder includes: a light source emitting light from a linear light-emitting portion with making a divergent angle of the light larger in a transversal direction of the light-emitting portion than in a longitudinal direction thereof; an objective lens projecting the light onto a target object and converging reflection light; a partial reflection member disposed between the light source and the objective lens and having a partial reflection surface composed of a transmitting area transmitting light emitted from the light source and receiving areas reflecting reflection light; and a photodetector detecting the reflection light reflected by the receiving areas; wherein the light source and the partial reflection member are disposed with making the longitudinal direction of the light-emitting portion disposed substantially perpendicular to a longitudinal direction of the transmitting area as seen along an optical axis.