Methods and systems for terahertz-based positioning

Patent metadata

Field	Value
Publication number	US-10795151-B2
Application number	US-201815951430-A
Country	US
Kind code	B2
Filing date	Apr 12, 2018
Priority date	Apr 12, 2018
Publication date	Oct 6, 2020
Grant date	Oct 6, 2020

Abstract

An encoder of a terahertz (THz)-based absolute positioning system used for decoding patterns from THz-band measurements. The encoder includes a scale with a multi-layer reflective/transmissive structure having a matrix with rows. Each row of the matrix corresponds to a plurality of patterns, such that each pattern is used to form a measurement. An emitter emits a THz waveform to the scale. A receiver is used to measure amplitudes of the THz waveform reflected from the scale. A memory stores data including predetermined positions of the emitter based on the patterns of the layers from the scale. Wherein one or more processors can determine a position of the emitter from the measurements of the amplitudes received by the receiver, based on the stored data. An output interface can be used to render the position of the emitter.

First claim

What is claimed is:

1. An encoder, comprising:
a scale with a multi-layer reflective/transmissive structure, wherein each layer includes a matrix having rows, such that each row of the matrix corresponds to a pattern used to form a measurement;
an emitter of a single THz transceiver of the encoder to emit a terahertz (THz) waveform to the scale according to a THz compressed scanning scheme while in relative motion with the scale;
a receiver of the single THz transceiver of the encoder to measure amplitudes of the THz waveform reflected from rows of each layer of the multi-layer reflective/transmissive structure through the scale;
a computer hardware memory to store data including patterns corresponding to predetermined positions of the emitter or a set of training amplitudes of reflected/transmitted THz waveforms, based on patterns of the multi-layer reflective/transmissive structure from the scale;
a processor to determine a position of the emitter from the measurements of the amplitudes received by the receiver based on the stored data; and
an output interface to render the position of the emitter.

2. The encoder of claim 1 , wherein the emitter with a focusing lens and a THz spatial light modulator is directed at a row of the matrix of each layer, such that the emitter emits the THz waveform to the scale via the collimating lens according to the THz compressed scanning scheme, wherein the THz waveform is collimated by the collimating lens and then modulated by the THz spatial light modulator with random patterns, the reflected THz waveform passes through the focusing lens and detected by the receiver of the single THz transceiver.

3. The encoder of claim 1 , wherein the emitter emits the THz waveform to the scale according to the THz compressed scanning scheme, with reflected measurements, to decode multi-row patterns of each layer of the multi-layer reflective/transmissive structure of the scale.

4. The encoder of claim 1 , wherein the emitter emits the THz waveform to the scale according to the THz compressed scanning scheme with reflected measurements, to decode multi-layer pseudo-random patterns for absolute positioning systems.

5. The encoder of claim 1 , wherein the emitter emits the THz waveform to the scale according to the THz compressed scanning scheme, such that the THz compressed scanning scheme uses l ∞ regularized least squared approach to decode the pseudo-random patterns with signal pre-processing steps.

6. The encoder of claim 1 , wherein the emitter emits the THz waveform to the scale according to the THz compressed scanning scheme, such that the THz compressed scanning scheme uses a box-constrained optimization approach to decode the pseudo-random patterns with signal pre-processing steps.

7. The encoder of claim 1 , wherein the emitter emits the THz waveform to the scale according to the THz compressed scanning scheme, such that the THz compressed scanning scheme uses prior distributions on the reflectance/transmission coefficients of patterns to identify signal features including positiveness and binary/multi-level values, with signal pre-processing steps.

8. The encoder of claim 7 , wherein the processor uses a variational Bayesian approach to recover the reflected/transmitted THz waveform or a binary/multi-level reflectance waveform of the scale.

9. The encoder of claim 8 , wherein the variational Bayesian approach used in the processor recovers an initial estimate of binary coded patterns by imposing a prior distribution on a solution and iteratively maximizes a posterior distribution likelihood function and a Q-function to update deterministic unknown parameters, so as to recover binary/multi-level patterns of the scale.

10. The encoder of claim 9 , wherein the Q-function is of an expectation-maximization (EM) algorithm that is an iterative variational EM algorithm, so as to recover binary/multi-level patterns of the scale.

11. An encoder, comprising:
a scale with a multi-layer reflective/transmissive structure, wherein each layer includes a matrix having rows, such that each row of the matrix corresponds to a pattern used to form a measurement;
an emitter of a single THz transceiver of the encoder to emit a terahertz (THz) waveform to the scale according to a THz compressed scanning scheme while in relative motion with the scale, such that the THz compressed scanning scheme uses prior distributions on reflectance/transmission coefficients of patterns to identify signal features including positiveness and binary/multi-level values, with signal pre-processing steps via a processor of the encoder;
a receiver of the single THz transceiver of the encoder to measure amplitudes of the THz waveform reflected from rows of each layer of the multi-layer reflective/transmissive structure through of the scale;
a computer hardware memory to store data including patterns corresponding to predetermined positions of the emitter or a set of training amplitudes of reflected THz waveforms, based on patterns of the multi-layer reflective/transmissive structure from the scale, wherein the processor determines a position of the emitter from the measurements of the amplitudes received by the receiver, based on the stored data; and
an output interface to render the position of the emitter.

12. The encoder of claim 11 , wherein the stored data includes a signal model of the reflected/transmissive waveform from each layer of the reflective/transmissive structure that forms a periodic pattern, such that the processor determines the position of the emitter from the measurements of the amplitudes based on the signal model.

13. The encoder of claim 11 , wherein the patterns of each layer of the reflective/transmissive structure from the scale form a non-periodic pattern to encode an absolute position of the emitter, wherein the stored data includes a mapping between sequences of amplitude values and a position of the emitter, such that the mapping is a function of the non-periodic pattern, and wherein the processor maps measurements of the sequences of the amplitudes to the position of the emitter according to the mapping.

14. The encoder of claim 13 , wherein each row of the matrix corresponds to a plurality of unit cells, such that the plurality of unit cells corresponds to a pattern, and wherein the data stored in the computer hardware memory include a pattern that defines one or combination of a predetermined position and an orientation of each plurality of unit cells in each row of the matrix.

15. The encoder of claim 14 , wherein the position of the unit cell defines at least one bit of data of the pattern.

16. An absolute positioning encoder method for an encoder, the method comprising:
emitting by an emitter of a single THz transceiver of the encoder a Terahertz (THz) waveform of the encoder according to a THz compressed scanning scheme while in relative motion with the scale, to a scale with a multi-layer reflective/transmissive structure, wherein each layer of the multi-layer reflective/transmissive structure includes a matrix having rows, such that each row of the matrix corresponds to a pattern used to form a measurement, wherein the THz compressed scanning scheme uses prior distributions on the reflectance/transmission coefficients of patterns to identify signal features including positiveness and binary/multi-level values, with signal pre-processing steps via a processor of the encoder, and the processor uses a variational Bayesian approach to recover the reflected/transmitted THz waveform or a binary/multi-level reflectance waveform of the scale;
measuring by a receiver of the single THz

Assignees

• Mitsubishi Electric Res Laboratories Inc

Inventors

• Wang Pu
• Fu Haoyu
• Orlik Philip
• Koike-Akino Toshiaki
• Ma Rui
• Wang Bingnan

Classifications

• B66B1/3492

  Position or motion detectors or driving means for the detector (B66B1/40, B66B1/50 take precedence; length measuring G01B; speed measuring G01P) · CPC title

• G01D5/34746 Primary

  Linear encoders · CPC title

• G01D5/34792

  with only digital scales or both digital and incremental scales · CPC title

• G02B26/101 Primary

  with both horizontal and vertical deflecting means, e.g. raster or XY scanners (colour television using laser beams scanning a display screen H04N9/3129) · CPC title

• G01B11/2518

  Projection by scanning of the object · CPC title