LV15370B - A device for obtaining speckle-free images under diffused laser light - Google Patents

Description

DESCRIPTION OF THE INVENTION

TECHNICAL FIELD The present invention relates to imaging technologies, in particular to obtaining surface images of an object under multiple scattered laser beams with no speckle grains in the images.

BACKGROUND OF THE INVENTION Diffused laser beam illumination is used in several fields of technology, such as for obtaining monochromatic spectral images (WO 2013135311 AI, 2012), from which it is possible to calculate skin or other object absorbing chromophore distribution maps (D.Jakovels and J.Spīgulis, J. Biophoton, 3 (3), 125-129, 2010; J. Spigulis et al., Proc. SPIE, Vol. 7557, 75570M, 2010; J. Spigulis et al., Proc. SPIE, v. 8216, 82160L, 2012). Laser beam scattering is required to provide uniform illumination of the subject's surface. For this purpose, beam diffusers are used, which slightly change and “mix” the radiation directions (J.Spīgulis and l.Oshina, J. Biomed.Opt., 20 (5), 050503, 2015), as well as special design diffuse reflectors ( WO 2017/0126 75 AI, 2015). Although the above works have achieved a uniform distribution of laser light intensity, the quality of the obtained images is reduced by "grains" or so on. laser spectra - spots of light produced by coherent radiation interference (https://en.wikipedia.org/wiki/Specklejiattem). Spectrum formation is determined by the spectral width, angle of incidence, polarization, and wavelength of laser radiation (http://www.siliconlight.com/wp-content/themes/siliconlight/pdf/speckle-spie.pdf)- There are known methods for the effective use of laser spectra , for example, for imaging the subcutaneous circulation (D.Jakovel, I.Saknite and J.Spigulis, Proc.SPIE, 9129, 912931, 2014). More often, however, the effects of laser beams are negative - for example, in laser projectors, their effects are mitigated by the use of mutually non-coherent (randomized) lasers (https://www.eng.yale.edu/caoiab/papers/nphotonl 2.pdf), lasers with extended spectral lines, changes in the polarization state of the radiation, or moving diffusers in the beam (http://www.dyoptyka.com/publications/Dyoptyka-PW-8252-4-updated.pdf). Spectrum-free images are also required for back-scattered laser light illumination, which is used, for example, to map the distribution of chromophores on or near an object with digital RGB image sensors (https://www.osapublishing.org'abstract.cfm? Uri = Cancer -2016-JTu3A.46). Known devices cannot provide spectra-free imaging under diffused laser light.

Disclosure of the Invention The object of the present invention is to provide speckle-free digital images in lighting homogenized using a reflective laser beam scatterer (s).

To achieve this object, there is provided a device comprising a digital image sensor with a lens for use in displaying an object, a laser for illumination, a reflector with light scattering, a mechanical oscillating element and a generator for such oscillation. The light-scattered reflector is mounted on a mechanically oscillating element and their total oscillation frequency f satisfies the condition ft> 5, where t is the exposure time of the digital image, and / 1> 5 was chosen by calculation and experiment to obtain the camera exposure. at least five full fluctuations (resulting in movement of the spike peaks), but the more the better. The moving part of the acoustic speaker can be used as a mechanical vibrating element in the device. The reflector of the device with a light scattering coating may be designed in the form of a ring with a barrier against laser radiation from the image sensor and positioned so that the image sensor with the lens is located inside the object's reflective lens ring.

BRIEF DESCRIPTION OF THE DRAWINGS [006] FIG. A flowchart of the proposed device is shown.

Fig. 2 skin RGB images taken with a smartphone camera under laser (448-532-659 nm) simultaneous illumination are compared with: a - still and b with reflector-diffuser;

Fig. 3 shows the spatial solution of the device.

The proposed device (Fig. 1) comprises a digital image sensor (2) used for displaying an object (1) and equipped with a lens, a laser unit for illumination (3), a reflector (4) with a light-scattering coating (5), a mechanical oscillator. element (6), oscillator (7).

For uniform illumination of the surface of the object (1), laser radiation reflected from the reflector (4) and diffused in its coating (5) is applied, which is supplied from the illumination laser unit (3). This unit contains a number of suitably oriented lasers and their power supply units that ensure the operation of the lasers and their on and / or off. The laser beams are guided through the scattering cover (5) to a reflector (4) connected to a mechanically oscillating element (6), for example, to a moving surface of an acoustic speaker. The oscillator (7) provides an adjustable oscillation frequency / selected to satisfy the condition tf> 5, wherein t is the exposure time of the image sensor (2), providing at least five oscillations (5) of the reflector (4) per exposure. Even oscillations with a few microns amplitude change the interference conditions of the scattered laser radiation on the surface of the object (1), causing the laser spectra to move periodically over this surface. This results in the blurring of speckles in the subject's image during exposure, reducing or eliminating its graininess and thus improving image quality.

The optical part of the device may have very small dimensions - for example, when a small telephone speaker is used, the movable part of which is fitted with a lightweight aluminum foil covered with a diffusive scattering tape. The effectiveness of this device is illustrated in Figure 2, which compares skin RGB images (3) taken with a smartphone camera under simultaneous illumination of lasers (448-532-659 nm): a - with rigid and b - with reflector-diffuser at frequency f = 80 Hz and exposure time t = 0.1 s (tf = 8). Reflector-diffuser oscillations are shown to effectively eliminate laser-generated grains in the skin image.

[010] The reflector diffuser (4), (5) may have different geometrical positions with respect to the image sensor (2), and may also have different shapes. An annular shape that covers the image sensor and provides the most uniform illumination of the subject is considered optimal, provided that the lasers used radiate symmetrically across the surface of the reflector. Such a spatial solution of the device is illustrated in Figure 3. Ring oscillation can be provided by two or more synchronized oscillating elements, such as loudspeakers on opposite sides of the ring, the movable parts of which are in mechanical contact with the ring.

Claims (3)

Claims An apparatus for obtaining spurious-free digital images in diffused laser beam illumination, comprising a digital image sensor (2) for displaying an object (1) with an objective, a laser illuminator unit (3), a reflector (4) with a light scattering coating (5), a mechanical oscillating element (6) and a oscillating oscillator (7), characterized in that the reflector (4) with the light scattering coating (5) is fixed to the mechanically oscillating element (6), whose oscillation frequency f satisfies the condition ft> 5 , where t is the exposure time of the digital image. Device according to claim 1, in which the movable part of the acoustic speaker is used as the mechanically oscillating element (6). The device according to claim 1 or 2, wherein the reflector (4) with the light scattering coating (5) is formed in the form of a ring with a laser barrier shield and is positioned so that the image sensor (2) with the lens 1) inside the illuminating ring.