CN103777376B - The multiple far field beam focal spot shapes of expection or position method for independently controlling based on optical phased array - Google Patents

Abstract

The invention belongs to Application Optics and diffraction optics interleaving techniques field, the multiple far field beam focal spot shapes of a kind of expection based on optical phased array or position method for independently controlling, on the multiple far field beam focal spot shapes of the expection based on optical phased array or position independent control device, expect different demands in far field according to the shape of multiple light beam focal spots or three-dimensional position, produce corresponding multiple PHASE DISTRIBUTION, multiple phase places divide formation composite phase to distribute for driving optical phased array, thereby the shape of the expection multiple beam far-field focus of realization based on optical phased array or three-dimensional position is any, independent, and machinery-free inertia programming Control.

Description

Shape or position-independent control of far-field focal spots of expected multiple beams based on optical phased array

technical field

The invention belongs to the field of applied optics and diffractive optics, and mainly relates to the technology of arbitrary and independent control of the shape or position of the far-field focal spots of expected multiple beams based on the optical phased array. The advantages of programming control, based on a new phase distribution formation method, according to the expected requirements of the shape or position of the multi-beam far-field focal spot, corresponding multiple phase distributions are generated, and multiple phases form a composite phase distribution for driving optics Phased array, so as to achieve arbitrary, independent, and no mechanical inertia programming control of the expected multi-beam far-field focal spot shape or three-dimensional position.

Background technique

In the fields of laser radar, laser weapons, laser tweezers, confocal microscope, laser engraving, laser processing, etc., traditional laser beam scanning control methods mostly use motor-controlled mechanical devices to scan, which has problems such as mechanical inertia, complex control, and large volume. The new beam scanning control technology based on optical phased array can overcome these shortcomings very well. My previous invention patent, the patent number is: 20101061377.2, and the name is: "A method for three-dimensional independent control of beam focus based on liquid crystal optical phased array 》It was invented in order to overcome the above shortcomings, but the phase distribution formation method used in it is a direct analytical solution method, and there are "unwanted spots" when controlling the expected multi-beam, and it cannot realize the control of the focal spot position of the controlled beam At the same time, arbitrary independent control of its shape.

Contents of the invention

The technical problem to be solved by the present invention is: how to realize arbitrary, independent, and no mechanical inertia programming control on the shape or three-dimensional position of the far-field focal spots of the expected multiple beams, and simultaneously eliminate "unwanted spots".

The technical scheme adopted in the present invention is: an independent control method for the shape or position of the far-field focal spot of multiple expected beams based on the optical phased array, and an independent control device for the shape or position of the expected multiple beams of the far-field focal spot based on the optical phased array On the basis of the shape or three-dimensional position of multiple beam focal spots, different requirements are expected in the far field, corresponding multiple phase distributions are generated, and multiple phase distributions form a composite phase distribution to drive the optical phased array, so as to realize the optical phase control based on Arbitrary, independent, and mechanical-inertia-free programming control of the shape or three-dimensional position of the desired multi-beam far-field focal spot of the array:

The expected multi-beam far-field focal spot shape or position independent control device based on optical phased array includes sequentially arranged lasers, apertures, collimating beam expanders, polarizers, optical phased arrays, lenses, and multiple far-field planes ;

According to the shape or three-dimensional position of multiple beam focal spots, different requirements are expected in the far field, and corresponding multiple phase distributions are generated:

Control the formation process of the phase distribution of the i-th beam focal spot: i is a natural number: the expected focal spot amplitude distribution on the far field plane is |D( _xi ', y _i ')|, and |D( _xi ' ,y _i ')|The intensity of some coordinate points in the far field plane is 1, and the other positions are all 0. It can be seen that the shape of |D( _xi ',y _i ')| (that is, the shape of the focal spot) can be arbitrary Expected shape distribution; the initial value of the phase distribution iteration is set to 0, and the phase distribution in subsequent iterations can be determined by the inverse Fourier transform of the far field through the following steps. Assume that this is the nth iteration, and n is a natural number greater than or equal to 1, then Have:

Step 1: Set the expected target complex amplitude distribution F _n ( _xi ', y _i ') of the far field plane can be expressed as:

Among them, x _i ', y _i ' are the coordinates of the far-field plane, F _n ' _-1 (x' _i , y' _i ) is the phase distribution of the n-1th iteration obtained in the far-field plane after Fourier transform The complex amplitude distribution of , is the phase distribution of the complex amplitude,

Step 2: The complex amplitude distribution T _n (x, y) of the plane where the phase distribution is located is obtained by the inverse Fourier transform of the complex amplitude distribution F _n ( _xi ', y' _i ) of the far field plane, which can be specifically expressed as follows:

Among them, x, y are the coordinates of the plane where the phase distribution is located, |T _n (x, y)| is the amplitude distribution of the light field on the plane where the phase distribution is located at this time, is the phase distribution of the light field in the plane where the phase distribution is located at this time, P _i (x,y) ^-1 is a negative lens phase distribution and Where j is the imaginary unit, λ is the wavelength of light, d is the distance from the objective lens to the plane where the phase distribution is located, f is the focal length of the objective lens, Δz _i is the distance from the moved plane to the reference plane, according to the distance between the moved plane and the reference plane Δz _i can be positive or negative;

Step 3: The phase distribution in the complex amplitude distribution T _n (x,y) of the plane where the phase distribution is located Retained, but the amplitude distribution is all set to 1, and a new complex amplitude distribution H _n (x, y) is obtained, which is expressed as:

Step 4: The complex amplitude F _n '(x' _i , y' _i ) of the far-field plane obtained after Fourier transform of the new complex amplitude distribution H _n (x, y) is:

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&infin;</span>}}{\overset{<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&infin;</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}\underset{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&infin;</span>}}{\overset{<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&infin;</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; \&lsqb;</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{<span\; class="notranslate">\; \&prime;</span>}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{<span\; class="notranslate">\; \&prime;</span>}\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span>\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; \&lsqb;</span>{\mathrm{<span\; class="notranslate">\; i\&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span>$

Among them, P _i (x,y) is the phase distribution of the positive lens, $P_i(x,\mathrm{the\; y})=\exp \&lsqb;-j\frac{{\mathrm{\&pi;\&Delta;z}}_i}{\mathrm{\&lambda;}({\mathrm{d\&Delta;z}}_i+{\mathrm{f\&Delta;z}}_i+f^2)}(x^2+{\mathrm{the\; y}}^2)\&rsqb;,$

The above four steps are iteratively calculated until F _n '(x' _i ,y' _i ) approaches and converges to the expected target complex amplitude distribution F _n ( _xi ',y _i ') of the set far-field plane, and the iteration is completed. at this time That is, corresponding to the phase distribution of the i-th beam focal spot that is solved, for more intuitive, it can be expressed as

Corresponding to i multiple beam control, it is necessary to generate i phase distributions There are two iteration methods for multiple phase distributions: serial iteration (Fig. 11) and parallel iteration (Fig. 12). The serial iteration is to iteratively calculate the phase distribution first. Then the phase distribution until the phase distribution Parallel iterations are phase-distributed Phase distribution Phase distribution Iterative calculations together in parallel.

As a preferred manner: the focal length of the lens is greater than zero.

As a preferred manner: the optical phased array is a transmissive optical phased array or a reflective optical phased array.

As a preferred manner: the composite phase distribution of the driving optical phased array is formed in the form of multiple phase distribution splicing or multiple phase distribution superposition.

As a preferred method: while the shapes of the far-field focal spots of multiple beams are arbitrary, independent, and programmed without mechanical inertia, the three-dimensional positions of the far-field focal spots of multiple beams can also be programmed arbitrarily, independently, and without mechanical inertia control.

The beneficial effects of the present invention are: no mechanical inertia and random programmable control of multiple beams can be realized; the focal spot of a single beam in multiple laser beams can be moved independently in three-dimensional space, and the shape distribution of the focal spot can also be arbitrarily Independent control; multiple laser beams can also be grouped for synchronous axial movement control; overcoming the "unwanted spot" problem.

Description of drawings

Fig. 1 is a schematic diagram of a transmissive optical phased array device without a lens of the present invention;

Fig. 2 is a schematic diagram of a transmissive optical phased array device with a lens of the present invention;

Fig. 3 is a schematic diagram of a reflective optical phased array device with a lens of the present invention;

Fig. 4 is a schematic diagram of a reflective optical phased array device without a lens of the present invention;

Fig. 5 is a schematic diagram of a composite phase distribution in which the composite phase distribution is formed by splicing according to the present invention;

Fig. 6 is a schematic diagram of a composite phase distribution in which the composite phase distribution is formed in the form of superposition in the present invention;

Fig. 7 is a schematic diagram of the principle model of the phase distribution of Fig. 1 and Fig. 4 of the present invention;

Fig. 8 is a schematic diagram of the principle model of the phase distribution in Fig. 2 and Fig. 3 of the present invention;

Fig. 9 is a schematic diagram of the axial movement of the far-field focal spot of a single beam expected by the present invention;

Fig. 10 is a schematic diagram of three-dimensional independent control of the far-field focal spot position of each beam in multiple beams;

Fig. 11 is a flowchart of serial iterative calculation;

Fig. 12 is a flowchart of parallel iterative calculation;

1. Laser, 2. Aperture, 3. Collimator beam expander, 4. Polarizer, 5. Optical phased array, 6. Lens, 7. Multiple planes in the far field, 8. Plane after movement, 9 , lens focal plane, 10, lens phase distribution i (i is a natural number), 11, moved plane i (i is a natural number), 12, moved plane 1,13, lens phase distribution 1,14, focal spot.

detailed description

The present invention is based on the advantages of the modulation and programmable control of the phase distribution of the optical phased array, based on a new phase distribution formation method, and generates corresponding multiple phase distributions according to the expected requirements of the shape or position of the multi-beam far-field focal spot. , a plurality of phase points form a composite phase distribution for driving the optical phased array, thereby realizing arbitrary, independent, and no mechanical inertia programming control of the expected multi-beam far-field focal spot shape or three-dimensional position. The phase control of the array achieves the object of the present invention.

The technology for controlling the shapes or positions of far-field focal spots of expected multiple beams based on optical phased arrays in the present invention mainly relates to the device and method for independently controlling the shapes or positions of multiple expected beams in far-field focal spots based on optical phased arrays.

Based on the optical phased array, it is expected that the shape or position of the far-field focal spot of multiple beams will be controlled independently: the schematic diagram of the specific implementation device depends on whether the type of the optical phased array is reflective or transmissive: it is divided into the following two types: based on the transmissive optical phase Figure 1 or Figure 2 shows the device for controlling the shape or position of multiple far-field focal spots of multiple beams expected by the array, and the device for controlling the shape or position of multiple beams independently based on the reflective optical phased array is shown in Figure 1. 3 or 4, without a lens can be regarded as a special case where the focal length of the lens is infinite.

An independent control method for the shape or position of the far-field focal spot of multiple beams based on the optical phased array: mainly includes the following aspects: (1) driving the formation method of the composite phase distribution of the optical phased array; (2) for the expected The phase distribution formation method of the two-dimensional scanning control of the shape or position of the far-field focal spot of a single beam; (3) the phase distribution formation method used to predict the axial scanning control of the far-field focal spot position of a single beam; The phase distribution formation method of the three-dimensional independent scanning control of the far-field focal spot shape or position of multiple beams.

(1) Formation method of complex phase distribution of driving optical phased array

For the control of multiple beams, multiple phase distributions are required, and multiple phases form a composite phase distribution to drive the optical phased array. Therefore, for an optical phased array with a certain aperture, the composite phase used to drive the optical phased array There are two ways to form the distribution: first, multiple phase distributions are spliced into a phase distribution of the aperture size of the optical phased array, that is, a composite phase distribution; second, multiple phase distributions are superimposed into a phase distribution of the aperture size of the optical phased array. distribution, that is, the composite phase distribution.

Fig. 5 is a schematic diagram of the composite phase distribution formed by splicing, and each sub-phase distribution corresponds to a focal spot of the far-field controlled beam.

Figure 6 is a schematic diagram of the composite phase distribution formed by superimposition. Each phase distribution corresponds to a far-field controlled beam spot, and the size of each phase distribution is equal to the aperture size of an optical phased array.

(2) The formation method of the phase distribution for the two-dimensional scanning control of the shape or position of the far-field focal spot of any expected single beam is easy to know according to Fourier optics theory. Under the irradiation of a coherent light source, a diffraction screen (phase distribution) and the corresponding The diffraction patterns of the fields (intended focal spots) are Fourier transforms of each other; the physical realization of this Fourier transform is equivalent to placing a lens between the diffractive screen (phase distribution) and the diffraction pattern of the corresponding far field (intended focal spot) of the diffractive screen , then the far field corresponds to the focal plane of the lens.

Figure 1 and Figure 4 show the principle model of the phase distribution formation based on the optical phased array to expect multiple beam far-field focal spot shapes or position independent control devices, as shown in Figure 7, and Figure 2 and Figure 3 show The principle model of the formation of the phase distribution of the independent control device for the shape or position of the far-field focal spot of multiple beams expected by the control array is shown in Figure 8, and the principle model shown in Figure 7 is equivalent to that of the lens with a very large focal length in the principle model shown in Figure 8 situation, so the principle model shown in Figure 8 is more general.

It is used to predict the shape of the far-field focal spot of a single beam or the phase distribution of the two-dimensional scanning control of the position: the expected amplitude distribution of the focal spot on a certain far-field plane (ie, the focal plane of the lens) is |D(x',y')| , and the intensity of |D(x', y')| in some coordinate points of the far field plane is 1, and the other positions are all 0. It can be seen that the shape of |D(x', y')| (that is, the shape of the focal spot ) can be any expected shape distribution; take a single light focus as an example: when |D(x',y')| the intensity of a certain (x',y') coordinate point in the far field plane is 1, and all other positions are 0, that is, a single point of light.

The initial value of the phase distribution iteration is set to 0, and the phase distribution in subsequent iterations can be determined by the inverse Fourier transform of the far field through the following four steps. Assuming that this is the nth iteration, then:

Step 1: Set the expected target complex amplitude distribution F _n (x',y') of the far field plane can be expressed as:

Among them, x', y' are the coordinates of the far-field plane, F _n ' _-1 (x', y') is the complex amplitude distribution actually obtained in the far-field plane after the phase distribution of the n-1 iteration is Fourier transformed , is the phase distribution of the complex amplitude.

Step 2: The complex amplitude distribution T _n (x, y) of the plane where the phase distribution is located is obtained by the inverse Fourier transform of the complex amplitude distribution F _n (x', y') of the far-field plane, which can be specifically expressed as follows:

Among them, x, y are the coordinates of the plane where the phase distribution is located, |T _n (x, y)| is the amplitude distribution of the light field on the plane where the phase distribution is located at this time, is the phase distribution of the light field in the plane where the phase distribution is located at this time.

Step 3: Phase distribution in the complex amplitude distribution T _n (x,y) of the plane in which the phase distribution is located Retained, but the amplitude distribution is all set to 1, and a new complex amplitude distribution H _n (x, y) is obtained, which is expressed as:

Step 4: The complex amplitude F _n '(x', y') of the far-field plane obtained after Fourier transform of the new complex amplitude distribution H _n (x, y) is:

The above four steps are iteratively calculated until F _n '(x', y') approaches and converges to the expected target complex amplitude distribution F _n (x', y') of the set far-field plane. It is the phase distribution to be solved, and the expected control can be achieved by loading the phase distribution into the optical phased array.

(3) The phase distribution formation method used for the axial synchronous scanning control of the position of the far-field focal spot of the expected single beam For the axial movement, the axial movement of the far-field focal spot of the expected single beam is realized, as shown in Figure 9, etc. The value is to realize the overall movement of the far-field plane including the focal spot. For convenience, the focal plane of the lens can be selected as the reference plane, that is, realizing the synchronous axial movement Δz of the far-field focal spot of the expected single or multiple beams is equivalent to realizing the overall movement Δz of the far-field plane including the focal spot, as shown in Figure 9 . In order to achieve this goal, it is necessary to introduce a lens phase distribution in step 4 (ie, formula 4) of the phase distribution formation calculation process of the aforementioned two-dimensional scanning control of the far-field focal spot position of the beam Where j is the imaginary unit, λ is the wavelength of light, and f _P is the focal length introduced into the lens phase distribution, which forms a combined focal length lens group similar to geometric optics with the objective lens to achieve the purpose of iterative plane movement. According to the combined focal length knowledge of geometric optics, the focal length of the lens phase distribution Where d is the distance from the objective lens to the plane where the phase distribution is located, and f is the focal length of the objective lens, as shown in Figure 9. Substituting f _P into the expression P(x,y) gives:

$\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; \&lsqb;</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}\frac{\mathrm{<span\; class="notranslate">\; \&pi;</span>}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; z</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; f</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span>$

Δz is the distance from the moved iteration plane to the reference plane as shown in Figure 9, and Δz can be positive or negative depending on whether the moved iteration plane is on the left or right of the reference plane.

After introducing the lens phase distribution P(x,y) in Equation 4, it is expressed as:

Correspondingly, it is necessary to introduce a negative lens phase distribution P(x,y) ^-1 into the formula 2 of the phase distribution formation calculation process of the aforementioned two-dimensional scanning control of the far-field focal spot position of the beam:

$\mathrm{<span\; class="notranslate">\; P</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; \&lsqb;</span>\mathrm{<span\; class="notranslate">\; j</span>}\frac{\mathrm{<span\; class="notranslate">\; \&pi;</span>}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; z</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; f</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span>$

After introducing the negative lens phase distribution P(x,y) ^-1 in Equation 2, it is expressed as:

(4) The phase distribution formation method for predicting the three-dimensional independent scanning control of the far-field focal spot shape or position of multiple beams.

The three-dimensional independent control of the shape or position of the far-field focal spot of the expected multi-beam based on the optical phased array in the present invention means that the shape or position of the far-field focal spot of each of the multiple beams can be independently controlled in three dimensions, as shown in Figure 10 Show.

In order to achieve three-dimensional independent control of the shape or position of the far-field focal spot of each of the multiple beams shown in Figure 10, there is one and only one beam focal spot on each moving plane, and each beam focal spot corresponds to a phase distribution , multiple beams correspond to multiple phase distributions, and multiple phase distributions form a composite phase distribution for driving an optical phased array, thereby achieving three-dimensional independent control of the far-field focal spot shape or position of each of the multiple beams, that is, the light The shape distribution of the focal spot itself can be controlled arbitrarily and independently. At the same time, the focal spot can move arbitrarily two-dimensionally in the plane, and the plane where it is located can move arbitrarily in the axial direction.

According to the shape or three-dimensional position of multiple beam focal spots, different requirements are expected in the far field, and corresponding multiple phase distributions are generated:

Control the formation process of the phase distribution of the i-th beam focal spot: the expected focal spot amplitude distribution on the far field plane is |D( _xi ',y _i ')|, and |D( _xi ',y _i ') |The intensity of some coordinate points in the far-field plane is 1, and the other positions are all 0. It can be seen that the shape of |D( _xi ', y _i ')| (that is, the shape of the focal spot) can be any expected shape distribution; Take a single light focus as an example: when |D(x', y')| the intensity of a certain (x', y') coordinate point in the far field plane is 1, and all other positions are 0, that is, a single light spot. The initial value of the phase distribution iteration is set to 0, and the phase distribution in subsequent iterations can be determined by the inverse Fourier transform of the far field through the following steps. Assuming that this is the nth iteration, then:

The method for independently controlling the shape or position of the far-field focal spot of multiple expected beams based on the optical phased array is characterized in that: on the device for controlling the shape or position of the far-field focal spot of multiple expected beams based on the optical phased array, according to multiple The shape or three-dimensional position of the focal spot of each beam is expected to be different in the far field, and corresponding multiple phase distributions are generated, and multiple phase points form a composite phase distribution to drive the optical phased array, so as to realize the expected multi-phased array based on the optical phased array. Arbitrary, independent, and no mechanical inertia programming control of the shape or three-dimensional position of the far-field focal spot of the beam:

The expected multi-beam far-field focal spot shape or position independent control device based on optical phased array includes sequentially arranged lasers, apertures, collimating beam expanders, polarizers, optical phased arrays, lenses, and multiple far-field planes ;

According to the shape or three-dimensional position of multiple beam focal spots, different requirements are expected in the far field, and corresponding multiple phase distributions are generated:

Control the formation process of the phase distribution of the i-th beam focal spot, i is a natural number: the expected focal spot amplitude distribution on the far field plane is |D( _xi ', y _i ')|, and |D( _xi ' ,y _i ')|The intensity of some coordinate points in the far field plane is 1, and the other positions are all 0. It can be seen that the shape of |D( _xi ',y _i ')| (that is, the shape of the focal spot) can be arbitrary Expected shape distribution; the initial value of the phase distribution iteration is set to 0, and the phase distribution in subsequent iterations can be determined by the inverse Fourier transform of the far field through the following steps. Assume that this is the nth iteration, and n is a natural number greater than or equal to 1, then Have:

Step 1: Set the expected target complex amplitude distribution F _n ( _xi ', y _i ') of the far field plane can be expressed as:

Among them, x _i ', y _i ' are the coordinates of the far-field plane, F _n ' _-1 (x' _i , y' _i ) is the phase distribution of the n-1th iteration obtained in the far-field plane after Fourier transform The complex amplitude distribution of , is the phase distribution of the complex amplitude,

Step 2: The complex amplitude distribution T _n (x, y) of the plane where the phase distribution is located is obtained by the inverse Fourier transform of the complex amplitude distribution F _n ( _xi ', y' _i ) of the far field plane, which can be specifically expressed as follows:

Among them, x, y are the coordinates of the plane where the phase distribution is located, |T _n (x, y)| is the amplitude distribution of the light field on the plane where the phase distribution is located at this time, is the phase distribution of the light field in the plane where the phase distribution is located at this time, P _i (x,y) ^-1 is a negative lens phase distribution and Where j is the imaginary unit, λ is the wavelength of light, d is the distance from the objective lens to the plane where the phase distribution is located, f is the focal length of the objective lens, Δz _i is the distance from the moved plane to the reference plane, according to the distance between the moved plane and the reference plane Δz _i can be positive or negative;

Step 3: The phase distribution in the complex amplitude distribution T _n (x,y) of the plane where the phase distribution is located Retained, but the amplitude distribution is all set to 1, and a new complex amplitude distribution H _n (x, y) is obtained, which is expressed as:

Step 4: The complex amplitude F _n '(x' _i , y' _i ) of the far-field plane obtained after Fourier transform of the new complex amplitude distribution H _n (x, y) is:

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&infin;</span>}}{\overset{<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&infin;</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}\underset{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&infin;</span>}}{\overset{<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&infin;</span>}}{<span\; class="notranslate">\; \&Integral;</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; \&lsqb;</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{<span\; class="notranslate">\; \&prime;</span>}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{<span\; class="notranslate">\; \&prime;</span>}\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span>\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; \&lsqb;</span>{\mathrm{<span\; class="notranslate">\; i\&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span>$

Among them, P _i (x,y) is the positive lens phase distribution $P_i(x,\mathrm{the\; y})=\exp \&lsqb;-j\frac{{\mathrm{\&pi;\&Delta;z}}_i}{\mathrm{\&lambda;}({\mathrm{d\&Delta;z}}_i+{\mathrm{f\&Delta;z}}_i+f^2)}(x^2+{\mathrm{the\; y}}^2)\&rsqb;,$

The above four steps are iteratively calculated until F _n '(x' _i ,y' _i ) approaches and converges to the expected target complex amplitude distribution F _n ( _xi ',y _i ') of the set far-field plane. when That is, corresponding to the phase distribution of the i-th beam focal spot that is solved, for more intuitive, it can be expressed as Corresponding to the control of multiple beams (for example, i multiple beams), it is necessary to iteratively generate i multiple phase distributions There are two iteration methods for multiple phase distributions: serial iteration as shown in Figure 11 and parallel iteration as shown in Figure 12. The serial iteration is to iteratively calculate the phase distribution first. Then the phase distribution …, until the phase distribution Parallel iterations are phase-distributed Phase distribution ..., phase distribution Iterative calculations together in parallel.

The advantages of the present invention are as follows:

1. It can realize multiple beams without mechanical inertia and random programmable control;

2. The focal spot of a single beam among multiple laser beams can be moved independently in three-dimensional space, and the shape distribution of the focal spot can also be independently controlled arbitrarily;

3. Multiple laser beams can also be grouped and synchronized for axial movement control;

4. Overcome the "unwanted spot" problem.

Claims (5)

1. the multiple far field beam focal spot shapes of the expection based on optical phased array or position method for independently controlling, is characterized in that:On the multiple far field beam focal spot shapes of the expection based on optical phased array or position independent control device, according to multiple light beam JiaoThe shape of spot or three-dimensional position expect in far field and different demands produce corresponding multiple PHASE DISTRIBUTION, and multiple PHASE DISTRIBUTION formComposite phase distributes and is used for driving optical phased array, thereby realizes the shape of the expection multiple beam far-field focus based on optical phased arrayAny, the independent and machinery-free inertia programming Control of shape or three-dimensional position:

The multiple far field beam focal spot shapes of expection or position independent control device based on optical phased array comprise tacticLaser instrument, aperture, collimator and extender device, polarizer, optical phased array, lens, the multiple planes in far field;

Expect in far field and produce different demands corresponding multiple phase place and divide according to the shape of multiple light beam focal spots or three-dimensional positionCloth:

Controlling the PHASE DISTRIBUTION forming process of certain i light beam focal spot: i is a natural number: the focal spot of expecting in the plane of far field shakesWidth is distributed as | D (x '_i,y′_i) |, and | D (x '_i,y′_i) | be 1 in the intensity of far field some coordinate points of plane, other positions are entirely0, visible | D (x '_i,y′_i) | shape, i.e. the shape of focal spot, can be that any anticipated shape distributes; PHASE DISTRIBUTION iterative initial valueBe made as 0, the PHASE DISTRIBUTION in successive iterations can be determined by following steps by the inverse fourier transform in far field, suppose to be nowThe n time iteration, n is more than or equal to 1 natural number, has:

Step 1: the set goal COMPLEX AMPLITUDE F that sets far field plane_n(x′_i,y′_i) can be expressed as:

，

Wherein, x '_i,y′_iFor the coordinate of far field plane, F '_n-1(x′_i,y′_i) be that the PHASE DISTRIBUTION of the n-1 time iteration becomes through FourierAfter changing in the COMPLEX AMPLITUDE of the actual acquisition of far field plane,For the PHASE DISTRIBUTION of this complex amplitude;

Step 2: the COMPLEX AMPLITUDE T of PHASE DISTRIBUTION place plane_n(x, y) is by the COMPLEX AMPLITUDE F of far field plane_n(x′_i,y′_i)Inverse fourier transform obtains, and specifically can be expressed as follows:

，

Wherein, x, y is the coordinate of PHASE DISTRIBUTION place plane, | T_n(x, y) | be the amplitude of PHASE DISTRIBUTION place planar lightfield nowDistribute,For the PHASE DISTRIBUTION of PHASE DISTRIBUTION place planar lightfield now, P_i(x,y)^-1Be that a negative lens phase place is dividedCloth and, wherein j is imaginary unit, λ is optical wavelength,D is the distances of thing lens to PHASE DISTRIBUTION place plane, and f is the thing focal length of lens, Δ z_iFor the plane after movement is to reference planesDistance, the Left or right according to the plane after mobile in reference planes, Δ z_iCan get positive sign or negative sign;

Step 3: the COMPLEX AMPLITUDE T of PHASE DISTRIBUTION place plane_nPHASE DISTRIBUTION in (x, y)Retain, but amplitude dividesCloth is all set to 1, obtains new COMPLEX AMPLITUDE H_n(x, y), it is expressed as:

；

Step 4: new COMPLEX AMPLITUDE H_nThe complex amplitude F ' of the far field plane that (x, y) obtains after Fourier transform_n(x′_i,y′_i) be:

，

Wherein, P_i(x, y) is positive lens PHASE DISTRIBUTION，

The calculating that iterates of above-mentioned four steps, until F '_n(x′_i,y′_i) convergence of approximation is in the set goal of setting far field planeCOMPLEX AMPLITUDE F_n(x′_i,y′_i), iteration completes, nowBe corresponding i light beam focal spot of control solvingPHASE DISTRIBUTION, for more directly perceived, it can be expressed as

Need to produce i PHASE DISTRIBUTION corresponding to many Beam Control of i。

2. the multiple far field beam focal spot shapes of the expection based on optical phased array according to claim 1 or position are independently controlledMethod processed, is characterized in that: the focal length of described lens is greater than 0.

3. the multiple far field beam focal spot shapes of the expection based on optical phased array according to claim 1 or position are independently controlledMethod processed, is characterized in that: described optical phased array is transmission-type optical phased array or reflective optic phased array.

4. the multiple far field beam focal spot shapes of the expection based on optical phased array according to claim 1 or position are independently controlledMethod processed, is characterized in that: drive the composite phase distribution generation type of optical phased array be multiple PHASE DISTRIBUTION splicings orMultiple PHASE DISTRIBUTION stacks.

5. the multiple far field beam focal spot shapes of the expection based on optical phased array according to claim 1 or position are independently controlledMethod processed, is characterized in that: the shape of multiple far field beam focal spots arbitrarily, when independent and machinery-free inertia programming Control,The three-dimensional position of multiple far field beam focal spots can also be by any, independent and machinery-free inertia programming Control.