CN111770244B - Non-modulation DMD spatial light modulator imaging method - Google Patents
Non-modulation DMD spatial light modulator imaging method Download PDFInfo
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- CN111770244B CN111770244B CN202010752565.0A CN202010752565A CN111770244B CN 111770244 B CN111770244 B CN 111770244B CN 202010752565 A CN202010752565 A CN 202010752565A CN 111770244 B CN111770244 B CN 111770244B
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Abstract
A non-modulation DMD spatial light modulator imaging method belongs to the infrared light imaging technology field; the method aims to solve the problem that the gray value imaged by the thermal response mode infrared detector by the existing DMD imaging method is inaccurate. The method converts a frame of 8-bit wide image into 255-bit wide data; taking a frame of 8-bit-width data as DMD external input, and performing data conversion on the frame of 8-bit-width data by a DMD control system to expand the frame of 8-bit-width data into a frame of 255-bit-width data; storing a frame of 255-bit-wide data into a high-speed DDR2 memory; the DMD reads a frame of 255-bit-wide data from the high-speed DDR2 memory according to the sequence that the high bit reads the low bit first and then reads the low bit, and sends the frame of 255-bit-wide data to an internal register of the DMD; executing a DMD overturning control instruction; wherein 0 is an off state; 1 is an open state; and converting the 255bit wide data into an image for displaying in a non-modulation mode. The thermal response mode infrared detector has the advantages that the thermal response mode infrared detector accurately receives all light energy reflected by the DMD, and the gray value is accurate after imaging.
Description
Technical Field
The invention belongs to the technical field of infrared light imaging.
Background
Thermal infrared imagers are widely used in astronomy, space science, night observation, infrared imaging guidance, searching, tracking, alarming and scientific experiments; in order to test the performance of the infrared imaging sensors of the satellite, the infrared imaging seeker, the infrared search and tracking system and the infrared alarm system, certain infrared scenes matched with the use conditions are required to be provided for the infrared imaging sensors in a laboratory as input images, so that the infrared imaging sensors generate certain output, and the simulation test of the thermal infrared imager is carried out; digital Micromirror array Devices (DMDs) can produce different wavelength band images by replacing the imaging window.
In the current stage, an 8421 modulation mode is adopted based on a DMD imaging mode, and 256 gray level images are displayed by turning a frame of image for 8 times; as is well known, DMD imaging adopts a modulation format, that is, an external image (generally an 8-bit-wide image, and a 256-gray level can be realized with an 8-bit-wide image) is received, and by means of the 8421-code format, the DMD images 1bit at a time, and 8-bit image inversion is completed by 8 times of inversion, wherein the lowest opening period is unit 1 when the image is displayed; the second bit is the square of the first bit open period, i.e., 2; the third bit is the second bit open period squared, i.e., 4; by analogy, 8-bit image display is completed, and finally, 256-level image display with 8bit width is realized in a modulation mode, as shown in fig. 1 specifically; in fig. 1, it can be seen from the graph that the DMD outputs 168 gray scales in the modulation mode, the maximum light energy output is 128 time units of light energy. Taking the gray scale 168 as an example, the above method display mode is: decimal 10 is converted into 10101010 in 2, and DMD presents 170 gray scale in the following way:
open 1 time (open time is 128 time units);
closed 1 time (closing time is 64 time units);
open 1 time (open time 32 time units);
closed 1 time (closing time is 16 time units);
open 1 time (open time is 8 time units);
closed 1 time (closing time is 7 time units);
through the calculation, the gray scale 168 is displayed in a gray scale modulation mode, 5 switching actions are required for opening and closing the DMD, and the total opening time is 168 time units (128 +32+ 8).
In the modulation type imaging mode, when an image is displayed, a frame of image needs to be turned 8 times, if an observation device adopts a detector in a thermal corresponding form, under the condition that the response time (the minimum time for collecting light energy is longer, and the light energy cannot be collected if the minimum time is longer), the light output of 8-time turning can generate a fault phenomenon, and the fault phenomenon can cause that the observation device can not accurately collect the energy reflected by the DMD.
Disclosure of Invention
The invention aims to solve the problem that the gray value imaged by a thermal response mode infrared detector by the existing DMD imaging method is inaccurate, and provides a non-modulation type DMD spatial light modulator imaging method.
The invention discloses a non-modulation DMD spatial light modulator imaging method, which comprises the following steps of:
converting a frame of image with the resolution of M multiplied by N and the bit width of 8 bits into a frame of data with the bit width of 8 bits; wherein M is the number of pixels of the image in the horizontal direction, and M is a positive integer; n is the number of pixels of the image in the vertical direction, and N is a positive integer;
step two, taking the frame of 8-bit-width data obtained in the step one as DMD external input, and performing data conversion on the frame of 8-bit-width data by the DMD to expand the frame of 8-bit-width data into a frame of 255-bit-width data;
step three, storing the frame 255bit wide data obtained in the step two into a high-speed DDR2 memory;
reading a frame of 255-bit-wide data from the high-speed DDR2 memory by the DMD according to the sequence that the high bit is read first and the low bit is read later, and sending the frame of 255-bit-wide data to an internal register of the DMD;
step five, executing a DMD overturning control instruction;
and step six, converting the 255bit wide data into an image for displaying in a non-modulation mode.
The invention has the advantages that according to the DMD imaging mechanism, within the range of one frame of image, the DMD lens is only overturned for 1 time to complete the display of gray scale images; under the condition, within the response time range of the observation equipment, the DMD is turned over only once, and light energy reading errors influenced by the closed state of the DMD caused by 8-time turning over of the modulation mode are avoided; in the response time of the observation equipment, all light energy reflected by the DMD can be accurately received, and the gray value is accurate after imaging.
Drawings
Fig. 1 is a graph of on-off state and light energy response of a DMD micromirror in a modulated imaging mode 186 with a default response slope of 1 in the background art; in the figure, an X axis represents the switching state and the switching time of the DMD, a thick line part of the X axis represents that the DMD is in an on state of '1', a thin line part of the X axis represents that the DMD is in an off state of '0', a binary value of '1010 1000' is obtained after the high bit is combined in the front of the low bit and then the gray value is 168; the Y-axis represents the reflected energy value; curve Z represents the light energy response curve in the case of DMD output gray scale 168 in the modulation mode;
fig. 2 is a flowchart illustrating an imaging method of a non-modulation DMD spatial light modulator according to a first embodiment;
fig. 3 is a graph of the on-off state and light energy response of a DMD micromirror in a modulated imaging mode 186 gray scale mode according to a first embodiment, wherein the default response slope is 1; in the figure, the X axis represents the switching state and the switching time of the DMD, the thick line part of the X axis represents that the DMD is in an on state of 1, the thin line part of the X axis represents that the DMD is in an off state of 0, the binary value obtained by combining the high bit, the front bit, the low bit and the rear bit is 11111, 8230, 82300000 (168 pieces of 1 and 87 pieces of 0), and the gray value is 168; the Y-axis represents the reflected energy value; curve Z represents the light energy response curve for the DMD output gray scale level 168 in modulation mode.
Detailed Description
The first specific implementation way is as follows: the present embodiment will be described with reference to fig. 2 and 3, in which a non-modulation DMD spatial light modulator imaging method according to the present embodiment is described; characterized in that the imaging method comprises the following steps:
step one, converting a frame of image with the resolution of M multiplied by N and the bit width of 8 bits into a frame of data with the bit width of 8 bits; wherein M is the number of pixels of the image in the horizontal direction, and M is a positive integer; n is the number of pixels of the image in the vertical direction, and N is a positive integer;
step two, taking the frame of 8-bit-width data obtained in the step one as DMD external input, and performing data conversion on the frame of 8-bit-width data by the DMD to expand the frame of 8-bit-width data into a frame of 255-bit-width data;
step three, storing the frame 255bit wide data obtained in the step two into a high-speed DDR2 memory;
reading a frame of 255-bit-wide data from the high-speed DDR2 memory by the DMD according to the sequence that the high bit is read first and the low bit is read later, and sending the frame of 255-bit-wide data to an internal register of the DMD;
step five, executing a DMD overturning control instruction;
and step six, converting the 255bit wide data into an image for displaying in a non-modulation mode.
In this embodiment, the specific data conversion manner of performing data conversion on a frame of 8-bit-wide data in the second step and expanding the frame of 8-bit-wide data into a frame of 255-bit-wide data is as follows:
corresponding ' 0 ' in a frame of 8-bit-width data to ' 255 ' 0 ' of a frame of 255-bit-width data;
corresponding ' 1 ' in a frame of 8-bit-wide data to ' 254 0's and 1's of a frame of 255-bit-wide data;
corresponding "2" in a frame of 8-bit-wide data to "253 0 s and 21 s" in a frame of 255-bit-wide data;
by analogy with that
Corresponding '254' in a frame of 8-bit-wide data to '1 0, 254 1' of a frame of 255-bit-wide data;
"255" in a frame of 8-bit-wide data corresponds to "255 1's" of a frame of 255-bit-wide data.
In the present embodiment, the number of 255-bit-wide data frames in the fourth step is M × N.
In this embodiment, the DMD inversion control command in step five is specifically: turning the DMD to an on state and an off state according to the 0 state or the 1 state of each frame of 255-bit-wide data; wherein 0 is an off state; 1 is in the on state.
In the embodiment, after receiving externally input 8-bit-width data, the DMD converts the 8-bit-width data into 255-bit-width data; as can be seen from the converted data, each 255-bit data is formed by combining 0 and 1, and all 0 and all 1 are arranged adjacently; by way of example: 00001111 can occur in the data after conversion, but the 0 and 1 interval condition of 01011010 can not occur; after data conversion, converting a frame of image with 1024 × 768 resolution and 8bit width into an image with 1024 × 768 resolution and 255bit width; because the DMD is turned over by taking a surface as a unit, 786432 micro lenses on one surface of a DMD turning instruction are turned over at a time, one frame of image data is stored in a high-speed DDR2 memory, when the DMD is read from DDR2, 255-bit data of the one frame of image data is read according to the sequence that a high bit is read first and then a low bit is read, and the image resolution is 1024 × 768, the read data is 786432 data which is 1024 × 768 data and is sent to an internal register of the DMD, after the 786432 data is sent to the internal register of the DMD, the DMD is turned over to an on state and an off state through a DMD control instruction according to the 0 or 1 state of each data, wherein 0 is an off state; 1 is an on state; the time for storing the data of one surface into the DMD is 30.72 microseconds (calculated according to the clock period written into the register of the DMD, a mode of improving the clock period can be adopted here to reduce the write period), the execution time of the control instruction is 4.5 microseconds, the DMD keeps the state unchanged during the execution of the control instruction, in order to facilitate the frame frequency calculation, the holding time of one surface is designed to be 35 microseconds (1 time unit), the total number of 255 surfaces is one frame of data, the time required by one complete frame of data is 8925 microseconds (255 time units), and the maximum displayable image frequency of 1024 × 768 resolution ratio 8bit width within one second is 112 frames.
Also taking the gray scale 168 as an example, decimal 10 is converted into 255 scale 00000000-11111111 (87 0 s and 168 1 s), and the DMD exhibits the gray scale 168 in the following manner:
open 1 time (open time is 168 time units);
closed 1 time (open time 170 time units);
through the above calculation, the gray scale 168 is displayed in a non-modulation manner, 1 (the gray scale is not affected by the closing state at the end) switching actions are required for opening and closing the DMD, the overall opening time is 168 time units, and the highest energy is 168 time units, as shown in fig. 3 specifically; as can be seen from the graph of fig. 3, when the DMD outputs 168 gray scales in the modulation mode, the maximum light energy output is 168 time units of light energy. Aiming at the thermal response mode observation equipment, the light energy of 168 time units is accurately output, so that the gray level of the original image 168 is accurately reproduced, and the problem of inaccurate maximum light energy output caused by DMD modulation is solved.
Also taking the gray scale 170 as an example, the highest total reflected energy in the modulation mode is 128-64+32-16+8-4+1 and is 85 time units of light energy in one frame range; in the non-modulation mode of the present embodiment, since there is no redundant flip modulation, the highest total reflected energy in a frame range is the light energy of 170 time units of the on time unit.
By the mode, aiming at the thermal response mode detector, the original gray level of the image can be completely restored by a non-modulation imaging mode, so that the thermal response mode detector can acquire the correct gray level of the original image; the modulation mode may output light energy incorrectly, and the thermal response mode detector may not acquire the correct gray value of the original image.
Claims (2)
1. A non-modulation DMD spatial light modulator imaging method; characterized in that the imaging method comprises the following steps:
step one, converting a frame of image with the resolution of M multiplied by N and the bit width of 8 bits into a frame of data with the bit width of 8 bits; wherein M is the number of pixels of the image in the horizontal direction, and M is a positive integer; n is the number of pixels of the image in the vertical direction, and N is a positive integer;
step two, taking the frame of 8-bit-width data obtained in the step one as DMD external input, and performing data conversion on the frame of 8-bit-width data by the DMD to expand the frame of 8-bit-width data into a frame of 255-bit-width data;
step three, storing the frame 255bit wide data obtained in the step two into a high-speed DDR2 memory;
reading a frame of 255-bit-wide data from the high-speed DDR2 memory by the DMD according to the sequence that the high bit is read first and the low bit is read later, and sending the frame of 255-bit-wide data to an internal register of the DMD;
step five, executing a DMD overturning control instruction;
sixthly, converting the 255bit wide data into an image for displaying in a non-modulation mode;
in the second step, a frame of 8-bit-width data is subjected to data conversion, and the specific data conversion mode for expanding the frame of 255-bit-width data is as follows:
corresponding ' 0 ' in a frame of 8-bit-width data to ' 255 ' 0 ' of a frame of 255-bit-width data;
corresponding ' 1 ' in a frame of 8-bit-wide data to ' 254 0's and 1's of a frame of 255-bit-wide data;
corresponding "2" in a frame of 8-bit-wide data to "253 0 s and 21 s" in a frame of 255-bit-wide data;
by analogy with that
Corresponding '254' in a frame of 8-bit-wide data to '1 0, 254 1' of a frame of 255-bit-wide data;
corresponding '255' in a frame of 8-bit-width data to '255 1' of a frame of 255-bit-width data;
in the fifth step, the DMD overturn control instruction is specifically: turning over the DMD to be in an on state and an off state according to the 0 or 1 state of each frame of 255-bit-wide data; wherein 0 is an off state; 1 is in the on state.
2. A non-modulating DMD spatial light modulator imaging method according to claim 1; the method is characterized in that the number of the 255-bit-wide data in one frame in the fourth step is M multiplied by N.
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