CN108366195B - High-speed spatial light modulation method based on LED array and imaging system thereof - Google Patents

Abstract

The invention discloses a high-speed spatial light modulation method based on an LED array and an imaging system thereof, belonging to the cross technical field of quantum physics, detection imaging and signal processing. The system comprises a computer, a control board card, an LED array, a beam modulation lens, an object, a beam collection lens and a single-pixel photoelectric detector, wherein the application method comprises the steps that firstly, the LED array generates Hadamard patterns and stores the Hadamard patterns in the control board card; then the control board controls the LED array to display Hadamard patterns in sequence through twice scanning, and acquires the voltage average value from the display of the first scanning pattern to the display of the second scanning pattern; and finally, the computer sums the products of the Hadamard patterns and the corresponding voltage average values to restore the image. The method and the device improve the speed of associated imaging and realize quick display of the Hadamard pattern, and have lower cost.

Description

A high-speed spatial light modulation method and imaging system based on LED array

technical field

The invention belongs to the cross technical field of quantum physics, detection imaging and signal processing, and in particular relates to a high-speed spatial light modulation method based on an LED array and an imaging system thereof.

Background technique

Correlation imaging originated from the concept of quantum entanglement. It is a new type of photoelectric imaging technology that records the total light intensity signal emitted/reflected by the target through one or several single-pixel detectors. Features. Single-pixel detection is the main feature of correlation imaging that is different from traditional area-array detection imaging. It means that correlation imaging uses one or several single-pixel detectors instead of area-array detectors (such as CCD, CMOS, etc.) to receive target signals and reconstruct its spatial information. The single-pixel detector technology is mature and reliable, with strong signal collection capability. There are no area array detectors, such as uneven response between pixels, dead pixels, and high requirements for imaging optical systems. Especially area array detectors in specific detection bands are particularly expensive and even When there is no need for multi-spectral composite imaging, single-pixel correlation imaging provides a technically feasible, cost-controllable, and low-volume imaging solution for corresponding target detection.

The single-pixel detection system of computational correlation imaging makes correlation imaging technology must rely on some kind of spatial light modulation device to realize imaging. At present, the conventional methods include using laser irradiation to rotate frosted glass to generate pseudothermal light source, prefabricated phase mask, transmissive liquid crystal modulation and reflective microlens array (Digital Micromirrors Device, DMD) modulation and so on. Due to the limited modulation speed of the spatial light modulator (the fastest DMD in the above methods currently reaches a modulation speed of 22KHz), the speed of obtaining target information in correlated imaging is greatly limited, which is the bottleneck of its technological development and is also a scientific worker in related fields. Difficulties to be overcome.

SUMMARY OF THE INVENTION

Aiming at the problem that the imaging speed of the existing correlation imaging is limited by the modulation speed of the spatial light modulator, the present invention proposes a high-speed spatial light modulation method based on an LED array and an imaging system thereof, which greatly improves the correlation imaging speed, and the space The light modulation speed reaches 2.5MHz, and the imaging speed reaches 5KHz.

The high-speed spatial light modulation imaging system based on the LED array provided by the present invention uses the LED array as the spatial light modulator, and the system includes a computer, a control board, an LED array, a beam modulation lens, an object, a beam collection lens and a single pixel Photodetector. The I/O of the control board outputs control signals to the LED array, and outputs the beam of the pattern corresponding to the Hadamard matrix through two scans. The light beam is focused on the receiving surface of the single-pixel photodetector. The control board collects the voltage value output by the single-pixel photodetector and transmits the data to the control computer for image restoration.

The LED array-based high-speed spatial light modulation method provided by the present invention includes:

Step 1, for an m×m LED array, generate m×m Hadamard patterns and store them in the control board; m is a positive integer, which is a power of 2;

Step 2, the control board controls the LED array to display the Hadamard pattern in sequence. A Hadamard pattern to be displayed is decomposed into two scanning patterns, the control board outputs a control signal to the LED array, and the display of a Hadamard pattern is completed through two scans; the LED array displays the light beam of the corresponding pattern according to the control signal, and the light beam passes through The beam modulating lens converges on the object, and then the light beam after the action of the object is collected by the beam collecting lens and converged on the receiving surface of the single-pixel photodetector;

Step 3, the control board collects the voltage value output by the single-pixel photodetector; for a Hadamard pattern, collects the voltage average value from the display of the first scan pattern to the end of the display of the second scan pattern; finally, the computer calculates the m× The product of the m Hadamard patterns and the corresponding voltage averages is summed to restore the image.

The advantages and positive effects of the present invention are: using the LED array as the spatial light modulator can greatly improve the speed of correlation imaging and realize the rapid display of the Hadamard pattern by means of two scans, which is 2 orders of magnitude higher than the traditional method. . In addition, the LED array has a lower price relative to the spatial light modulators used in existing correlated imaging schemes.

Description of drawings

Fig. 1 is the composition schematic diagram of the high-speed spatial light modulation imaging system based on LED array of the present invention;

2 is a schematic diagram of the generation of Hadamard patterns of different orders in the present invention;

Fig. 3 is the schematic diagram of generating 10th-order Hadamard pattern in the present invention;

4 is a schematic diagram of some data in the 10th-order Hadamard pattern generated in the present invention;

Figure 5 is a schematic diagram of the control mode of the LED array; (a) the control mode of the LED array, (b) the Hadamard pattern to be displayed, (c) the decomposition display pattern 1, (d) the decomposition display pattern 2;

Figure 6 is the experimental effect diagram.

Detailed ways

The technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

The imaging system of the high-speed spatial light modulation method based on the LED array provided by the present invention uses the LED array as the spatial light modulator, and the overall frame of the system is shown in FIG. 1 . The system includes a computer 1 , a control board 2 , an LED array 3 , a beam modulation lens 4 , an object 5 , a beam collection lens 6 and a single-pixel photodetector 7 .

The I/O of the control board 2 outputs a control signal to the LED array 3, and outputs the beam of the pattern corresponding to the Hadamard matrix through two scans. 6 collects the light beams acting on the object 5 and converges them on the receiving surface of the single-pixel photodetector 7 . The control board 2 collects the voltage value output by the single-pixel photodetector 7 and transmits the data to the computer 1 for image restoration.

The Hadamard pattern corresponding to the LED array is stored in the control board 2 . For an m×m LED array, m×m groups of Hadamard patterns are generated and stored in the control board 2 . m is a positive integer and is a power of 2. Since any Hadamard pattern can be decomposed into two separate patterns for display, the control board 2 controls the LED array 3 to display and output two scanning patterns of the Hadamard pattern. The control board 2 controls the LED array to display all Hadamard patterns in sequence, and for each Hadamard pattern, collects and calculates the average voltage from the display of the first scan pattern to the end of the display of the second scan pattern. Finally, the image is recovered by summing the products of the m × m Hadamard patterns and the corresponding voltage averages in the computer.

The LED array-based high-speed spatial light modulation method provided by the present invention includes the following steps 1 to 3, and each step is described in detail below.

Step 1: Calculate the Hadamard pattern.

Taking a 32x32 LED array as an example, 1024 groups of Hadamard patterns S _i (32, 32), i=1, 2, ...... 1024 are generated and stored in the control board 2 .

哈达玛矩阵生成规则如下：Among them, as shown in Figure 2, for the Hadamard matrix of order n

The Hadamard matrix generation rules are as follows:

其中

in

如图3所示。每次显示的图案S_i为矩阵

中的第i行对应的数据转换为32行32列所对应的图案，如图4所示。For a 32x32 LED array, it is necessary to generate a Hadamard matrix of order 10, and replace the -1 in the matrix H ₁₀₂₄ with 0, denoted as

As shown in Figure 3. The pattern Si _displayed each time is a matrix

The data corresponding to the i-th row in is converted into a pattern corresponding to 32 rows and 32 columns, as shown in Figure 4.

Step 2: The LED array is controlled by the control board 2 to display the Hadamard pattern in sequence, and 1024 groups of voltage values P _i collected by the photodetector 7 are collected synchronously, i=1, 2, ...... 1024.

As shown in Figure 5, the specific LED control method is as follows (displayed in rows and columns):

Traditional LED arrays usually use row and column scanning to display a pattern. For a pair of N*N LED lattices, N scans are required to complete the display of an image. However, through the analysis of the Hadamard pattern, the method proposed in the present invention can complete the display of a pair of Hadamard patterns through two scans. As shown in FIG. 5 , for any Hadamard pattern S _i to be displayed, it can be decomposed into two scanning patterns S _i,1 , S _i,2 to complete the display. S _i,1 and S _i,2 can be expressed as:

S _i,1 =row(S _i ,1)*colum(S _i ,1)

表示矩阵S_i取反。

表示矩阵

的第一行，

表示矩阵

的第一列。Among them, row(S _i ,1) represents the first row of the matrix S _i , and column(S _i ,1) represents the first column of the matrix S _i ,

_Represents the inversion of matrix Si.

representation matrix

the first line of

representation matrix

the first column of .

Therefore, regardless of the size of the array, the _Hadamard pattern can be displayed by decomposing each pattern Si into Si _,1 , Si _,2 for two scans. This method can greatly improve the LED array display Hadamard pattern speed.

The collected voltage value _Pi is the average voltage of the pattern _Si from the beginning of the display of Si _,1 to the end of the display of Si _,2 .

Step 3: Complete Hadamard pattern display and voltage acquisition and calculate imaging results. The calculation of the restored image is as follows:

Among them, Si represents the Hadamard pattern displayed in the _ith time, _Pi represents the average value of the detector voltage corresponding to the display Si collected in the _ith time, and I represents the recovered image.

The method for high-speed spatial light modulation based on an LED array and its imaging system of the present invention are verified by physical experiments. The experiment uses a 32x32 LED array to achieve an imaging speed of up to 1000fps. The experimental results are shown in Figure 6, and the imaging effects at the imaging speed of 250fps, 500fps and 1000fps, respectively.

Compared with the array used in the prior art, the LED array used in the present invention is inexpensive and has a fast modulation speed. For example, the DMD spatial light modulation array is expensive, and the modulation speed is slow. The fastest modulation speed is 22KHz. And the LED array used in the present invention is cheap, and the fastest modulation speed can reach 100MHz-1GHz.

In addition, according to the characteristics of the Hadamard pattern, the present invention proposes an LED array modulation method, which can decompose any Hadamard pattern into two separate patterns for display. The traditional LED displays an N*N pattern in a line scan display manner, and it will require N scans to complete the display of a pattern. However, the method proposed in the present invention only needs two scans to complete the display of a Hadamard pattern, so the speed of displaying the Hadamard pattern by the LED can be greatly improved.

Claims (6)

1. A high-speed spatial light modulation imaging system based on an LED array is characterized by comprising a computer, a control board card, the LED array, a light beam modulation lens, an object, a light beam collecting lens and a single-pixel photoelectric detector; wherein the LED array acts as a spatial light modulator;

hadamard patterns corresponding to the LED arrays are stored in the control board card; the I/O of the control board card outputs a control signal to the LED array, light beams of patterns corresponding to the Hadamard matrix are output in a mode of scanning twice, the light beams are converged on an object through the light beam modulation lens, and then the light beams which are collected by the light beam collection lens and acted by the object are converged on a receiving surface of the single-pixel photoelectric detector; the control board card collects the voltage value output by the single-pixel photoelectric detector and transmits the data to the computer for image recovery; outputting the light beam with the pattern corresponding to the Hadamard matrix by twice scanning is specifically to output the ith Hadamard pattern S_iDecomposed into two-pass scan pattern S_i,1And S_i,2As follows：

S_i,1＝row(S_i,1)*colum(S_i,1)

Wherein, row (S)_i1) represents a matrix S_iFirst row of (C), colum (S)_i1) represents a matrix S_iThe first column of (a) is,

representation matrix S_iThe process is carried out in a reverse manner,

representation matrix

The first row of (a) is,

representation matrix

The first column of (2).

2. The system of claim 1, wherein the control board stores m hadamard patterns corresponding to m LED arrays, m being a positive integer to the power of 2.

3. The system of claim 1 or 2, wherein the hadamard pattern is decomposed into two scanning patterns, and for each hadamard pattern, the control board card controls the LED array to display and output two scanning patterns of the hadamard pattern.

4. The system of claim 1 or 2, wherein the control board collects the average voltage value for each hadamard pattern from the display of the first scan pattern to the display of the second scan pattern.

5. The system of claim 4, wherein the computer sums the products of the m x m Hadamard patterns and the corresponding voltage averages to recover the image.

6. A high-speed spatial light modulation method based on an LED array is characterized by comprising the following steps:

step 1, for an m × m LED array, generating m × m Hadamard patterns and storing the m × m Hadamard patterns in a control board card; m is a positive integer to the power of 2;

step 2, the control panel card controls the LED array to display Hadamard patterns in sequence;

decomposing a Hadamard pattern to be displayed into two scanning patterns, controlling the board card to output a control signal to the LED array, and completing the display of the Hadamard pattern through two scanning patterns; the LED array displays light beams of corresponding patterns according to the control signals, the light beams are converged on an object through the light beam modulation lens, and then the light beams which are collected by the light beam collection lens and acted by the object are converged on a receiving surface of the single-pixel photoelectric detector; in the step 2, the ith Hadamard pattern S_iDecomposed into two-pass scan pattern S_i,1And S_i,2The following were used:

S_i,1＝row(S_i,1)*colum(S_i,1)

wherein, row (S)_i1) represents a matrix S_iFirst row of (C), colum (S)_i1) represents a matrix S_iThe first column of (a) is,

representation matrix S_iThe process is carried out in a reverse manner,

representation matrix

The first row of (a) is,

representation matrix

The first column of (1);

step 3, controlling the board card to collect the voltage value output by the single-pixel photoelectric detector; for a Hadamard pattern, collecting the average voltage value from the display of the first scanning pattern to the display of the second scanning pattern; and finally, the computer sums the products of the m multiplied by m Hadamard patterns and the corresponding voltage average value to restore the image.

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