CN107844457B - Light source calculation method for specific light distribution in non-uniform medium - Google Patents

Light source calculation method for specific light distribution in non-uniform medium Download PDF

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CN107844457B
CN107844457B CN201710591627.2A CN201710591627A CN107844457B CN 107844457 B CN107844457 B CN 107844457B CN 201710591627 A CN201710591627 A CN 201710591627A CN 107844457 B CN107844457 B CN 107844457B
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light source
distribution
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CN107844457A (en
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赵会娟
闫盼盼
赵宽心
高峰
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Tianjin University
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    • G06F17/10—Complex mathematical operations
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Abstract

The invention relates to a light source calculation method for specific light distribution in a non-uniform medium, which comprises the following steps: (1) knowing the distribution of the optical parameters in the inhomogeneous medium and the distribution of the desired light intensity in the inhomogeneous medium; (2) partitioning the inhomogeneous medium according to the distribution of the optical parameters; (3) partitioning the light source array of the DMD; (4) utilizing Monte Carlo accelerated by a GPU to simulate MCX (micro control Unit) to carry out forward calculation, namely setting all incident lights of a non-uniform medium surface light source area corresponding to a light source array partition to be uniform surface light sources, and calculating the normalized distribution A of the light flow rate in the non-uniform medium by the MCX; (5) the linear equation set is listed, and the least square solution of the linear equation set is solved to obtain the light intensity of each light source area on the medium surface; (6) the light intensity distribution of each region of the light source array is obtained by the distance square inverse law, and quantitative and accurate light projection of the target non-uniform medium region is realized.

Description

Light source calculation method for specific light distribution in non-uniform medium
Technical Field
The invention belongs to the field of biomedical photonics, and relates to a light source calculation method for specific light distribution in a non-uniform medium and an implementation system thereof.
Background
In the field of biomedical photonics, when the incident condition of a light source and the distribution of optical parameters of a tissue volume, including absorption coefficient, scattering coefficient, refractive index, anisotropy factor, are known, monte carlo simulation (MC) or Diffusion Equation (DE) is widely used to obtain the statistical distribution of photons in the tissue volume.
In practical applications, when the optical parameter distribution of the tissue and a specific photon distribution in a certain region inside the tissue are known, the required light source distribution and the projection condition of the light source need to be inferred reversely, so-called inverse problem, for example: the application of light in photodynamic therapy, the application of laser medicine and the like. Such problems are not solved by MC simulation or DE.
Disclosure of Invention
The invention aims to provide a light source calculation method for specific light distribution in a non-uniform medium, which utilizes the comprehensive effect of light in the non-uniform medium to enable a light source to project light with different spatial distribution and light intensity distribution to project into the non-uniform medium, thereby realizing the distribution of specific light in the medium to be obtained. The technical scheme is as follows:
a light source calculation method for specific light distribution in non-uniform media adopts a device comprising a laser light source, a digital micro-mirror device DMD and a computer control system, wherein the computer control system realizes the control of the space distribution and the light intensity of emergent light of the laser light source and the digital micro-mirror device DMD, thereby realizing the quantitative and accurate light projection of a target non-uniform media area, and is characterized in that the method comprises the following steps:
(1) knowing the distribution of the optical parameters in the inhomogeneous medium and the distribution of the desired light intensity in the inhomogeneous medium;
(2) zoning q the inhomogeneous medium according to the distribution of optical parameters1、q2、q3…qnThe optical parameters in the same area are not changed greatly as much as possible;
(3) dividing the light source array of the DMD into areas p1、p2、p3…pm，m>n；
(4) Utilizing Monte Carlo accelerated by a GPU to simulate MCX (micro control Unit) to carry out forward calculation, namely setting all incident lights of a non-uniform medium surface light source area corresponding to a light source array partition to be uniform surface light sources, and calculating the normalized distribution A of the light flow rate in the non-uniform medium by the MCX;
(5) the linear equation set is listed, and the least square solution of the linear equation set is solved to obtain the light intensity of each light source area on the medium surface;
(6) the light intensity distribution of each region of the light source array is obtained by the distance square inverse law, and quantitative and accurate light projection of the target non-uniform medium region is realized.
The method of step 5) is as follows;
setting the light intensity to be projected by the light source in each area of the non-uniform medium surface corresponding to the DMD light source array partition as I1、I2、I3…ImKnowing the location of interest q in the inhomogeneous medium1The required light intensity distribution is
Figure BDA0001354886550000011
I1At position q1Has a contribution of11，I2At position q1Has a contribution of21By analogy, ImAt position q1Has a contribution ofm1(ii) a By analogy, position qnThe required light intensity distribution is
Figure BDA0001354886550000012
I1At position qnHas a contribution of1n，I2At position qnHas a contribution of2n，ImAt position qnHas a contribution ofmnThe linear system of equations:
Figure BDA0001354886550000021
aijrepresenting the luminous flux rate of the ith light source at position j, the above equation can be expressed as:
Figure BDA0001354886550000022
then
Figure BDA0001354886550000023
Obtaining the light intensity value I which should be projected by each area of the surface of the inhomogeneous medium by the least square solution of the linear equation systemi。
The invention has the following advantages: the method reversely deduces the distribution condition of the light source from the known optical parameter distribution of the inhomogeneous medium and the known light intensity distribution required to be obtained in the tissue body, and the system specifically realizes the light source distribution and the projection mode obtained by the method.
Drawings
Fig. 1 is a schematic structural diagram of a light source projecting system based on a digital micromirror device DMD according to the present invention;
FIG. 2 is a flow chart of a method for computing a light source projection for inhomogeneous media according to the present invention;
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail below with reference to the accompanying drawings by taking a Digital Micromirror Device (DMD) -based light source projection system as an example.
Referring to fig. 1, the structure schematic diagram of a light source projecting system based on a digital micromirror device DMD provided by the present invention includes: laser light source 1, coupling fiber 2, Digital Micromirror Device (DMD)3, computer control system 4 and non-uniform medium 5.
The realization method comprises the following steps: a laser light source with the center wavelength of 532nm is adopted, a Digital Micromirror Device (DMD) converts light beams into 1140 x 912 independently controllable micromirror light sources, and the rotation of each micromirror can be independently controlled by writing and burning gray level pictures of the DMD through a computer, so that the control of the output light intensity distribution of the DMD is realized, and the control of the output light intensity of the DMD can be realized by adjusting the output power of a laser. The specific process is as follows:
first, the distribution of absorption coefficient, scattering coefficient, refractive index, various anisotropy factors, and the desired intensity distribution in the inhomogeneous medium of interest are known as Ψ.
Dividing the inhomogeneous medium into regions q according to the difference of its optical parameters1、q2、q3…qn1140 x 912 micro mirror array in DMD is also divided into area p1、p2、p3…pm，m>n。
Monte carlo simulation (MCX) accelerated using a GPU forward simulates the distribution of photons within the medium. During simulation, light sources on the surface of the non-uniform medium corresponding to the DMD micro-mirror partitions are set as uniform surface light sources according to the diameter of the exit pupil of the DMD and the transmittance, and the normalized distribution of the light energy flow rate in the medium is A.
Is arranged in a DMD micro-mirror array partition pairThe light intensity of the light source projected by each area of the corresponding inhomogeneous medium surface is I1、I2、I3…ImKnowing the location of interest q in the inhomogeneous medium1The required light intensity distribution is
Figure BDA0001354886550000031
I1At position q1Has a contribution of11，I2At position q1Has a contribution of21. By analogy, ImAt position q1Has a contribution ofm1(ii) a By analogy, position qnThe required light intensity distribution is
Figure BDA0001354886550000032
I1At position qnHas a contribution of1n，I2At position qnHas a contribution of2n，ImAt position qnHas a contribution ofmn；
Since the light intensity in each region of interest is a common contribution of all source region illumination, a linear system of equations can be aligned:
Figure BDA0001354886550000033
aijrepresenting the luminous flux rate of the ith light source at position j, the above equation can be expressed as:
Figure BDA0001354886550000034
then
Figure BDA0001354886550000035
Solving for
Figure BDA0001354886550000036
The light intensity value I which is projected by each area of the surface of the inhomogeneous medium is obtainedi。
According to the inverse square law of illuminance
Figure BDA0001354886550000037
Calculating the illuminance E to be put in the DMD according to the light intensity distribution on the medium surfaceiWhere r represents the distance of the DMD stop to the target media.
According to EiThe gray value distribution of the control picture of controlling 1140 x 912 micromirror rotation frequency of the burning DMD is programmed, thereby controlling the distribution of the output light intensity of the DMD.
The power of the laser is set, the output light intensity of the DMD is controlled, and quantitative and accurate light projection of a target medium area is achieved.
A light source projection calculation method based on a Digital Micromirror Device (DMD) and an implementation system thereof are disclosed, referring to fig. 1 and 2, the method comprises the following steps:
101: knowing the optical parameter distribution of the target inhomogeneous medium and the required light intensity distribution in the medium;
102: partitioning the surface of the inhomogeneous medium;
103: partitioning the DMD micro-mirror array;
104: the method comprises the following steps that a GPU accelerated Monte Carlo simulation (MCX) forwardly simulates the distribution of photons in a non-uniform medium when a uniform area light source irradiates;
105: solving a least square solution of a linear equation set to obtain the light intensity distribution required to be put on the surface of the medium;
106: calculating to obtain the illuminance to be put in the DMD;
107: controlling the distribution of the output light intensity of the DMD; writing gray value distribution of control picture for controlling 1140-912 micromirror rotation frequency of burning DMD, thereby controlling distribution of DMD output light intensity
108: controlling the magnitude of the output light intensity of the DMD. The output power of the laser is adjusted, the output light intensity is controlled, and quantitative and accurate light projection of a target medium area is realized
In summary, the present invention provides a light source calculation method for specific light distribution in a non-uniform medium and an implementation system thereof, which realizes that the light source distribution and the projection mode are obtained by reversely deducing the optical parameter distribution of a tissue and the known light intensity distribution required in the tissue.

Claims (2)

1. A light source calculation method of specific light distribution in non-uniform media adopts a device comprising a laser light source, a digital micro-mirror device DMD and a computer control system, wherein the computer control system realizes the control of the space distribution and the light intensity of emergent light of the laser light source and the digital micro-mirror device DMD, thereby realizing the quantitative and accurate light projection of a target non-uniform media area;
(1) knowing the distribution of the optical parameters in the inhomogeneous medium and the distribution of the desired light intensity in the inhomogeneous medium;
(2) zoning q the inhomogeneous medium according to the distribution of optical parameters1、q2、q3…qnThe optical parameters in the same area are not changed greatly as much as possible;
(3) dividing the light source array of the DMD into areas p1、p2、p3…pm，m＞n；
(4) Utilizing Monte Carlo accelerated by a GPU to simulate MCX (micro control Unit) to carry out forward calculation, namely setting all incident lights of a non-uniform medium surface light source area corresponding to a light source array partition to be uniform surface light sources, and calculating the normalized distribution A of the light flow rate in the non-uniform medium by the MCX;
(5) the linear equation set is listed, and the least square solution of the linear equation set is solved to obtain the light intensity of each light source area on the medium surface;
(6) the light intensity distribution of each region of the light source array is obtained by the distance square inverse law, and quantitative and accurate light projection of the target non-uniform medium region is realized.
2. The calculation method according to claim 1, wherein the method of step 5) is as follows:
setting the light intensity to be projected by the light source in each area of the non-uniform medium surface corresponding to the DMD light source array partition as I1、I2、I3…ImKnowing the location of interest q in the inhomogeneous medium1As requiredThe light intensity distribution is
Figure FDA0001559193590000011
I1At position q1Has a contribution of11，I2At position q1Has a contribution of21By analogy, ImAt position q1Has a contribution ofm1: by analogy, position qnThe required light intensity distribution is
Figure FDA0001559193590000012
I1At position qnHas a contribution of1n，I2At position qnHas a contribution of2n，ImAt position qnHas a contribution ofmnThe linear system of equations:
Figure FDA0001559193590000013
aijrepresenting the luminous flux rate of the ith light source at position j, the above equation can be expressed as
Figure FDA0001559193590000014
Then
Figure FDA0001559193590000015
Solving the least square solution of the linear equation system to obtain the light intensity value I which should be projected by each area of the surface of the inhomogeneous mediumi。
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CN101485234A (en) * 2006-06-28 2009-07-15 皇家飞利浦电子股份有限公司 Method of controlling a lighting system based on a target light distribution
CN102216677A (en) * 2008-09-16 2011-10-12 马斯科公司 Method, system and apparatus for highly controlled light distribution from light fixture using multiple light sources (led's)
CN101896957A (en) * 2008-10-15 2010-11-24 松下电器产业株式会社 Light projection device
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