Optical digitizer/position measuring device

• US 4,531,230 A
• Filed: 06/14/1982
• Issued: 07/23/1985
• Est. Priority Date: 06/16/1981
• Status: Expired due to Fees

• Current Assignee: ASEA AB Vasteras Sweden
• Original Assignee: Asea Aktiebolag (ABB Limited)
• Inventors: Brogardh, Torgny
• Primary Examiner(s): Boudreau, Leo H.
• Application Number:
  US06/388,439
• Time in Patent Office: 1,135 Days
• Field of Search: 250/555-559, 250/561, 250/566, 250/568, 250/571, 250/578, 250/208, 250/227, 250/231 SE, 178/18-20, 382/44, 382/48, 382/59-61, 382/13, 382/65, 356/375, 356/373, 340/347 P, 235/462-465, 235/469
• US Class Current: 382/187
• CPC Class Codes: G06V 10/12 Details of acquisition arrangements; Constructional details thereof

Abstract

The invention relates to an optical transducer for measuring position, angle, and the time dependence of these quantities in one, two or three dimensions, with at least one fiber optical transducer having light-emitting means which feeds incident light to an object on which the measurement is to be effected, a photo-detector which senses light emanating from the object after said incident light has been influenced by the object and an electronic unit partly for controlling the light-emitting means, and partly for evaluating the output of the photo-detector, the output signal being dependent on the variations in light transmission, light absorption, light reflection and/or photo-luminescence of a pattern on the object. The variations of one or more of the optical properties of the pattern in at least one direction have at least three different amplitude values which occur in a specific order, and that the relative amplitude values between variations of the optical properties, which variations are consecutive in space, are detected and evaluated by the electronic unit for determining the direction of movement and the position of the transducer relative to the object.

Claims

1. An optical measuring system comprising at least one optical fiber transducer and an object having a surface, the measuring system being adapted to measure position, angle, and the time dependence of these quantities in at least one dimension between said transducer and said surface of the object,

said measuring system further comprising at least one light-emitting means and said at least one optical fiber transducer to illuminate said surface, at least one photo-detector means to sense light from said light-emitting means emanating from said surface, and

at least one electronic unit for controlling the light emitted by said light-emitting means and evaluating the signal variations from said photo-detector means,

said surface being provided with an optically detectable pattern defined by variations of an optical property

said variations of at least one of said optical properties of said surface are arranged to have at least three different amplitude values in at least one direction across said surface, said amplitude values being defined by the difference between a local maximum and a local minimum of said at least one optical property of said optically detectable pattern, said local minimum lying to one side of said local maximum in said at least one direction,

said at least three different amplitude values are arranged to occur in a predetermined order in said at least one direction,

said amplitude values, which are obtained when said at least one optical fiber transducer is displaced relative to said surface, are arranged, through the opto-electronic arrangement of said light-emitting means, said at least one optical fiber transducer and said photo-detector means, to be transformed into electric signal amplitudes by said photo-detector means, and

said signal amplitudes being evaluated by said electronic unit to determine the position, the angle and/or the direction of movement of said at least one optical fiber transducer relative to said surface of the object.

2. An optical measuring system according to claim 1, in which said signal amplitudes are modulated in space to represent binary numbers and maintaining the detectability of the sequence of said signal amplitudes in space and thus the direction of movement of said at least one optical fiber transducer.

3. An optical measuring system according to claim 2, in which binary numbers of consecutive amplitude values are utilized for determining the absolute position of said at last one optical fiber transducer relative to said surface of the object.

4. An optical measuring system according to claim 3, in which an additional amplitude value is used for marking the absolute position represented in said binary numbers.

5. An optical measuring system according to claim 1, in which said optical properties vary within at least one wavelength range in one direction and within a second non-identical wavelength range in another, non-parallel direction, said light-emitting means emitting light in both wavelength ranges, said detector means receiving light in both wavelength ranges, and the detector signal variations in the two wavelength ranges being input to the electronic unit to determine the position of said at least one optical fiber transducer relative to said surface of the object in two dimensions.

6. An optical measuring system according to claim 5, in which light in a third different wavelength range is used for generating a reference signal, whereby the entire surface of the object is coated with an optical medium to generate across the entire surface a constant optical signal for compensation of instability in the optic system and variations in distance between the transducer and the object.

7. An optical measuring system according to any one of claims 1, 5 or 6, in which said at least three different amplitude values are arranged to be obtained by varying at least one of color strength and color spectrum when printing on cellulose or plastics material.

8. An optical measuring system according to any one of claims 1, 5 or 6, in which two of said fiber optical transducers are mounted on a printer, movable over said surface, for positioning the printer when marking a mark on said surface.

9. An optical measuring system according to any one of claims 1, 5 or 6, in which said at least one fiber optical transducer forms part of a pen for digitalizing graphic information marked on said surface.

10. An optical measuring system according to any one of claims 1, 2 or 3, in which said at least three different amplitude values are arranged to be generated by means of varying light properties in three different spectral bands and said varying optical properties at said different three spectral bands are respectively detected by means of at least three multiplexed light sources with different emission spectra, and each of these emission spectra respectively coincides at least partially with a different one of said spectral bands.

11. An optical measuring system according to claim 10, in which binary numbers are generated by the fact that said variations of at least one of said optical properties are binary-coded at a spectral band different from the spectral band(s) at which said direction of movement is determined, and at least one light-emitting means has an emission spectrum which at least partially coincides with said spectral band.

12. A method of optically sensing the movement of at least one fiber optical transducer means relative to a surface of an object in two non-parallel directions, comprising providing said surface with a pattern formed from discrete bands extending in each said direction and uniformly spaced apart in the other said direction, modifying incident light in a first wavelength range by the bands in one direction and modifying incident light in a second wavelength range by the bands in the other direction, modifying differently the incident light in the respective wavelength band by the adjacent bands in each said direction, receiving modified incident light from said bands in said at least one fiber optical transducer as the latter is moved over the surface, and determining from the received modified light in the respective two wavelength ranges the precise movement of said at least one optical transducer across the bands in the respective two directions.