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KR-20260065957-A - A system, subsystem, and method for speckle suppression in an imaging system, and an imaging system using a transmission subsystem having speckle suppression capabilities.

KR20260065957AKR 20260065957 AKR20260065957 AKR 20260065957AKR-20260065957-A

Abstract

Systems, subsystems, and methods for speckle suppression for an imaging system include: an illumination setup configured to emit light of a narrow wavelength bandwidth; a plurality of wavelength (WL) converters configured to receive at least a portion of the light emitted by the illumination setup and convert the spectral characteristics of at least a portion of the received light to form 'n' spectrally separated incident beam arrays; and a spectral beam combining (SBC) setup configured for beam-combining the spectrally separated incident beam arrays from the illumination setup and outputting a multispectral combined beam. The system(s), subsystem(s), and/or method(s) are configured to emit output light to illuminate at least one surface of an area of interest (AOI) in a manner that induces speckle suppression and also mitigates spatial intensity distribution broadening effects resulting from speckle suppression.

Inventors

  • 촘스키 도론
  • 가이어 오페르

Assignees

  • 엘비트 시스템즈 일렉트로-옵틱스 엘롭 리미티드

Dates

Publication Date
20260511
Application Date
20240516
Priority Date
20230921

Claims (20)

  1. A suppression subsystem for reducing speckle in an imaging system, wherein the suppression subsystem Lighting setup, the above lighting setup is: At least one light source, each of which is configured to emit light with a narrow wavelength bandwidth; and It includes a plurality of wavelength (WL) converters, wherein each of the plurality of wavelength converters is configured to receive at least a portion of light emitted by at least one of the at least one light source and to convert the spectral characteristics of the received portion of light, wherein the WL converters are configured to form an incident beam array divided into 'n' spectral sections, and A spectrum beam combining (SBC) setup configured to beam-combine the spectrum-separated incident beam arrays coming from the illumination setup and to output a multispectral combined beam comprising spectrum-separated multiple output beams propagating in parallel trajectories, The suppression subsystem is configured to emit output light from the same in order to illuminate at least one surface of an area of interest (AOI) in a manner that induces speckle suppression and mitigates the spatial intensity distribution expansion effect caused by the speckle suppression.
  2. In paragraph 1, The above SBC setup is, Array of 'n'collimators; An optical setup comprising at least one element having at least one diffraction surface, configured such that each of the received 'n' spectrally separated incident beams is diffracted at least twice to combine the spectrally separated incident beams; or A suppression subsystem comprising a plurality of dichroic mirrors, wherein each of the dichroic mirrors receives an input beam of incident beams separated by spectrum, each of the incident beams is a different WL 'λ k ', where 'k' is an index number between 1 and n, reflects a specific receivable input beam of WL λ k , is positioned and configured to transmit at least all previously transmitted and reflected beams of WL λ 1 to λ k-1 through it, and outputs a multispectral (MS) combined beam comprising WL λ 1 to λ n .
  3. In any one of paragraphs 1 to 2, Each of the above wavelength (WL) converters is a suppression subsystem comprising an optical parametric oscillator (OPO) and/or a Raman parametric wavelength (WL) converter.
  4. In paragraph 3, The above OPO is a suppression subsystem configured to variably control the WL of the light output by the OPO based on temperature control.
  5. In any one of paragraphs 1 through 4, Including more angle variety setups, The above angle diversity setup is configured and positioned to receive the multispectral combined beam formed by the above SBC setup and to form a plurality of virtual multispectral output sources formed on a virtual output surface, and is characterized by causing light emitted from the plurality of virtual multispectral output sources to collide with at least one surface of the AOI at different angles and different wavelengths.
  6. In paragraph 5, The above angle variety setup includes a guide optical setup, and A suppression subsystem characterized in that the guide optical setup is configured to receive the multispectral combined beam directly or indirectly from the SBC setup and to form a plurality of virtual multispectral output light sources, and each of the virtual light sources is steered to have a different angular propagation direction to output light having spectral and angular diversity.
  7. In paragraph 6, The above angle variety setup is A projection optical setup configured and positioned to reduce the spatial expansion of light emanating from the guide optical setup; and/or A suppression subsystem characterized by further comprising one or more incident optical setups configured and positioned to receive the multispectral combined beam from the above SBC setup and induce the received multispectral combined beam to pass through the guide optical setup.
  8. In Paragraph 7, The above guide optical setup is Bar-type homogenization guide element; or A suppression subsystem characterized by including one of two lenticular arrays arranged in parallel and having mutual focal lengths with a spacing 'd' from each other.
  9. In paragraph 8, The above bar-type homogenization guide element is a restraint subsystem having a rectangular or trapezoidal shape.
  10. In paragraph 8, The spacing 'd' between the two lenslet arrays above corresponds to the mutual focal distance of the lenslet arrays, forming a suppression subsystem.
  11. In any one of paragraphs 7 through 10, The projection optical setup and/or the incident optical setup comprises one or more focusing and/or collimation lenses, forming a suppression subsystem.
  12. In any one of paragraphs 1 through 11, A suppression subsystem further comprising an optical path length (OPL) adjustment setup configured and positioned to reduce mutual coherence by inducing a change between the optical path lengths (OPLs) of each beam portion of the multispectral combined beam formed by the above SBC setup.
  13. In any one of paragraphs 1 through 12, The at least one light source of the above lighting setup is a suppression subsystem comprising at least one of a laser device, a light-emitting diode, and a laser element.
  14. In Paragraph 13, The above at least one light source is a resonator-internal or external second harmonic generating type laser device, and is a suppression subsystem that outputs pulsed laser light within a narrow wavelength band.
  15. In Paragraph 14, The above laser device is a suppression subsystem configured to output light within the visible light wavelength band.
  16. In any one of paragraphs 14 to 15, The laser device above is a suppression subsystem that outputs pulsed light having a pulse duration greater than 50 nanoseconds (ns).
  17. A method for reducing speckle in an imaging system using a suppression subsystem, wherein the method is: A step of providing at least one light source configured to emit light with a narrow wavelength bandwidth; A step of providing a plurality of wavelength (WL) converters configured to convert the spectral characteristics of the received light; In each WL converter: A step of receiving at least a portion of the light emitted by at least one of the at least one light source and converting the spectral characteristics of at least a portion of the received light, wherein the WL converters are configured to form an incident beam array separated by 'n'spectra; A step of receiving and beam-combining the spectrum-separated incident beam arrays from the WL converters using a spectrum beam combining (SBC) setup; and The method includes the step of outputting a multispectral combined beam comprising multiple output beams separated by spectrum that propagate in parallel trajectories, and A method in which the above-mentioned suppression subsystem is configured to emit output light from the same to illuminate at least one surface of an area of interest (AOI) in a manner that induces speckle suppression and also mitigates spatial intensity distribution expansion effects resulting from speckle suppression.
  18. In Paragraph 17, The above SBC setup is Array of 'n'collimators; An optical setup comprising at least one element having at least one diffraction surface, configured such that each of the received 'n' spectrum-separated incident beam arrays is diffracted at least twice to combine the spectrum-separated incident beams; or A method comprising a plurality of dichroic mirrors, wherein each of the dichroic mirrors receives an input beam from incident beams separated by spectrum, wherein each of the input beams is a different WL 'λ k ', where 'k' is an index number between 1 and n, and is positioned and configured to reflect a specific WL 'λ k' of the received input beam and transmit at least all previously transmitted and reflected WL 'λ 1' to λ k -1 through it, and outputs a combined MS beam comprising WL 'λ 1' to λ n .
  19. In any one of paragraphs 17 to 18, A method in which each of the above wavelength (WL) converters comprises an optical parametric oscillator (OPO) and/or a Raman parametric wavelength (WL) converter.
  20. In Paragraph 19, A method for each of the above OPOs to variably control the WL of the light output by the same based on temperature control.

Description

A system, subsystem, and method for speckle suppression in an imaging system, and an imaging system using a transmission subsystem having speckle suppression capabilities. The present invention relates to the field of speckle suppression, and more specifically to systems and methods having speckle suppression capabilities for improved imaging of one or more objects/surfaces. Optical speckle noise can be defined as a grainy (noisy) texture appearing in an image of one or more imaged objects/surfaces, which generally degrades image quality-related characteristics such as contrast and/or depth accuracy. Speckle is often caused by uneven or rough surface texture(s) or varying roughness/reflectance values between different surfaces of the object(s) to be imaged. Speckle is known to increase when object(s) are irradiated with coherent light, such as a laser beam. One possible solution to reduce speckle formed by imaging systems using coherent laser light sources, which involves using spatial diversity techniques to generate multiple virtual light sources with similar spectral characteristics and varying optical path lengths, can be learned through the following: Martine Laurenzis et al., Franco-German Saint Louis Institute, Optical Engineering 51(6), 061302, June 2012, 'Homogeneous and Speckle Free Laser Illumination for Range-Gated Imaging and Active Polarimetry'; and Yves Lutz et al., February 15, 2016 http://proceedings.spiedigitallibrary.org/ Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx, 'Methodology for Conception of Speckle Reduction Elements in the Case of Short Pulse Illumination'. These papers/publications teach the use of optical devices that enable speckle reduction by inducing spatial diversity among multiple light sources of similar spectral characteristics using a single laser light source of a single emission wavelength (WL) or a narrow wavelength (WL) bandwidth, primarily by degrading beam coherency by forming multiple beams or beam portions having varying optical path lengths (OPLs) relative to one another. According to the methods described above and based on Goodman's speckle theory, when using 'M' (integer) light sources that have spectral coherency but OPL incoherence, the image contrast (Cim) is maximum It can be improved by a factor of ('m' square root), which is as follows: Assuming 'M' light sources with identical optical characteristics such as identical emission WL and intensity, where SC is the image speckles contrast (Csc) and SC0 is the initial image speckles contrast before speckle reduction/suppression. However, the number 'M' may be limited by one or more system limitations, such as the laser cavity length (Lc), and consequently limit the system's speckle reduction/suppression capability. Another technique for speckle suppression is to use spectral diversity by illuminating the target or region of interest (AOI) with a light source of a wide spectral range or by generating multiple beams with different spectral characteristics (emission WL). This technique is taught in '3D Imaging with Range Gated Laser Systems using Speckle Reduction Techniques to Improve the Depth Accuracy' by B. Johler et al., Optics and Pattern Recognition Laboratory, published in 'Electro-Optical and Infrared Systems: Technology and Applications V' of SPIE, edited by David A. Huckridge and Reinhard R. Ebert. ©2008 To understand the subject of the present invention and to see how to implement it in practice, the present invention will be described through non-limiting embodiments with reference to the accompanying drawings. FIG. 1 is a block diagram schematically illustrating a transmission subsystem comprising a suppression subsystem based on a combination of spectral and angular diversity for enhanced speckle suppression according to some disclosed embodiments. FIG. 2 is a block diagram schematically illustrating an imaging system using the transmission subsystem of FIG. 1. FIG. 3 schematically illustrates the main components of an illumination subsystem of a transmission subsystem that uses a single light source and multiple oscillators to generate an array of spectrally separated optical beams for spectral diversity-based speckle suppression according to some embodiments. FIG. 4 schematically illustrates the key components of an SBC setup used in a speckle suppression subsystem of a transmission subsystem of an imaging system based on spectral beam coupling (SBC), according to some embodiments. FIG. 5 schematically illustrates the main components of an SBC setup used in a speckle suppression subsystem that uses a plurality of dichroic mirrors to generate a multispectral beam used to illuminate a region of interest, according to other embodiments. FIGS. 6a and 6b illustrate an angular variation setup for speckle suppression according to some embodiments: FIG. 6a illustrates the main components of the angular variation setup; FIG. 6b illustrates a schematic example of beam paths as they pas