Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
  • G01S3/78—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using electromagnetic waves other than radio waves
  • G01S3/782—Systems for determining direction or deviation from predetermined direction
  • G01S3/783—Systems for determining direction or deviation from predetermined direction using amplitude comparison of signals derived from static detectors or detector systems
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B11/00—Measuring arrangements characterised by the use of optical techniques
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
  • G01C15/00—Surveying instruments or accessories not provided for in groups G01C1/00 - G01C13/00
  • G01C15/002—Active optical surveying means
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
  • G01S3/78—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using electromagnetic waves other than radio waves
  • G01S3/781—Details

Definitions

• the invention relates to a method for compensating for inhomogeneities in the refractive index of a dispersive medium when determining the direction of a target point by evaluating the propagation behavior of wave radiation emanating from the target point, according to the preamble of patent claim 1 of the procedure.
• This basic knowledge leads to the object of the present invention, which consists in developing a method and a device for detecting and compensating for such turbulence effects when determining the direction, so that even variable inhomogeneities for a short time in the refractive index of a dispersive medium when determining the direction of a target point by evaluating the propagation behavior of a wave radiation emanating from the target point.
• the measures according to the invention offer significant advantages in several respects: Even in the event of strong turbulence in the medium along the measuring path between the measuring point and the target point, e.g. perform very precise corrected angle measurements within seconds. The effects of turbulence are recorded briefly and also simultaneously with the actual measurement and processed to a corrected measured value. The reproducible accuracy of the measured values is a few hundred nanoradians when the measuring time of a few seconds is selected.
• Fig. 4 shows the example of a transmitter with a laser diode for generating two transmission frequencies
• Fig. 5 shows a receiver circuit for the invention
• FIG. 1 There is a direct geometric connection D between a transmitter 1 and a receiver 2. Light rays emanating from the transmitter 1 are deflected along the transmission path as a result of changes in refractive index, so that they are in the receiver at an angle ⁇ with respect to the straight line D arrive. Without a correction, the transmitter 1 would be a virtual transmitter l r appear on the connection D ', which can lead to incorrect measurements, in particular in the case of angle measurements and measurement methods based thereon.
• the dispersion effect is used, by means of which two different frequencies B and R are deflected to different extents along the transmission path.
• the difference in the angle of incidence caused by the dispersion is delta ⁇ . It has now been shown that, due to the dispersion, the angle difference delta ⁇ is, in a first approximation, directly proportional to the angle error ⁇ originating from the changes in the refractive index.
• the method described in more detail below takes this knowledge into account in that the angle deviations delta ⁇ caused by the dispersion are measured in very short time intervals as a series of individual measurements and are averaged over a period of seconds or minutes. The required correction for the actual measured value is then obtained from the mean value obtained. The time intervals mentioned for determining the correction values are matched to the actual changes in the refraction behavior of the transmission medium.
• n (x, y, z) is the refractive index of the medium (e.g. air)
• exp (ik (c + ax + by)] represents a plane wave propagating in the direction (a, b, l).
• the angles a and b are only dependent on the wavelength of the light via the refractive index n, such as this is necessary for the turbulence compensation.
• FIG. 4 shows the principle of obtaining two transmission frequencies from a single laser diode by frequency doubling.
• the deflected beam passes through a non-linear crystal 8, e.g. a potassium niobate or lithium niobate crystal.
• the frequency of the light wave is doubled, in the example to 860 nm.
• This frequency lies in the blue range and is designated B in FIG. 4, in contrast to the original frequency, which is in red -Range and is designated with R.
• an intensity filter 9 is provided in at least one of the beam paths.
• a rotating chopper disk 10 which carries out a different intensity modulation for both frequencies. This is achieved by slits S1 and S2 of different widths on the circumference of the chopper disk 10.
• the light rays R and B emanating from the transmitter 1 of different frequencies are collected jointly by a receiver optics 5 and directed onto the surface of a position-sensitive detector 6.
• the different frequencies are red and blue light beams which emanate from at least one laser diode in the transmitter.
• the detector is, for example, a dual photodiode, which has two adjacent light-sensitive areas E and F.
• an evaluation circuit on the receiver side has inputs E and F for the output signals of the photodiode regions and a reference input Ref.
• the input signals E and F are each fed to a sample and hold circuit 11 or 12.
• the outputs of these two circuits are sampled by a multiplex circuit 14, amplified in an amplifier 15 and fed to registers 17 via an analog / digital converter 16, where the signals for further processing in can be temporarily stored in a computer 18.
• Angular differences delta ß are obtained from the position signals at the inputs E and F.
• these values are related to other measured values in the sense of a correction in accordance with a predetermined program, so that corrected measured values can be output directly at the computer output, or these values are stored for later processing.
• two light frequencies of approximately 430 nm and approximately 860 nm were transmitted through an air atmosphere of approximately 24 degrees Celsius.
• the aperture of the receiver optics was 36 mm in one case and 46 mm in the second case.
• the individual measured values were averaged after 1 see and after 10 see. The results are as follows:

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Radar, Positioning & Navigation (AREA)
• Remote Sensing (AREA)
• Electromagnetism (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=4221623

Family Applications (1)

Country Status (3)

Families Citing this family (1)

Citations (3)

• 1987
  • 1987-05-19 CH CH191887A patent/CH674080A5/de not_active IP Right Cessation
  • 1987-09-08 DE DE19873730093 patent/DE3730093A1/de active Granted
• 1988
  • 1988-05-19 WO PCT/CH1988/000093 patent/WO1988009480A1/de unknown

Patent Citations (3)

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