CN113033723B - Annular mask, light field regulation and control method, single-pixel imaging method and system - Google Patents
Annular mask, light field regulation and control method, single-pixel imaging method and system Download PDFInfo
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Abstract
The invention belongs to the field of light field regulation and control, and provides an annular mask, a light field regulation and control method, a single-pixel imaging method and a system. The annular mask plate is annular in shape; the annular mask plate is covered with mask plate patterns, and the mask plate patterns consist of light-transmitting areas and light-non-transmitting areas. The annular mask plate has low manufacturing cost and a mark recognition area, and the orientation of the mask plate can be accurately determined by a mark bit mode, so that the modulation precision is improved.
Description
Technical Field
The invention belongs to the field of light field regulation and control, and particularly relates to an annular mask, a light field regulation and control method, a single-pixel imaging method and a single-pixel imaging system.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
Light field modulation techniques have important applications in many areas (e.g., computational imaging, etc.). The general light field regulation technology is performed by a spatial light modulator, and the amplitude or phase of light at different positions is modulated by an array modulation unit on the spatial light modulator. Different modulation patterns are realized by a program controlled modulator.
Single-pixel imaging, also called correlated imaging, computed ghost imaging and the like, is an imaging technology based on light field regulation and control and light intensity detection of a single-pixel detector. During imaging, a spatial light modulator is used to produce a modulating effect on the spatial distribution of light. Modulation is generally used to modulate the spatial distribution of light intensity, and can be classified into active light field modulation and passive light field modulation. Active light field modulation refers to the use of an active illumination source to illuminate light onto a spatial light modulator. The spatial light modulator modulates the spatial distribution of the intensity of the illumination light. The illumination pattern with the spatial structure is then projected onto the object through the projection lens. The above procedure can be understood as the working principle of the projector. At the detection end, the intensity of the object under structured light illumination is detected by a single-pixel detector that can only detect the intensity. Passive modulation refers to the imaging of an object onto an image plane by an imaging lens under background illumination. The spatial light modulator is placed on the image plane, i.e. the object and the spatial light modulator are located on the object and image planes of the imaging lens. The spatial light modulator spatially modulates the intensity of an image of the object. The modulated object image is detected by a single pixel detector which detects only the intensity.
With respect to spatial light modulators, liquid crystal spatial light modulators (lcslms), and digital metal micromirror arrays (DMDs) are currently mainly used. In addition, the mode of generating speckle by rotating ground glass is adopted for active light field modulation single-pixel imaging. However, single pixel imaging with speckle is generally considered to have poor signal-to-noise ratios. DMD performs best among all modulator schemes and is widely used. Specifically, speckle is a gray-scale pattern, whereas DMD modulation typically produces a binary black-and-white pattern (0, 1 pattern). The advantages of DMDs include: can produce black-and-white structured light illumination with higher contrast and has high modulation speed. The 22KHz binary modulation is most quickly achieved by a common commercial DMD.
However, a single-pixel imaging system using DMD modulation still has a serious problem that the imaging speed is slow. The reason for this problem can be understood as follows. The single-pixel imaging process is an iterative process, and image information acquisition is realized through light field regulation and control of a plurality of pairs of different structures and corresponding single-pixel detection signals, so that reconstruction is realized. The light field regulation of different structures is realized by refreshing the DMD. Let the reconstructed image resolution be N, taking full sampling as an example (i.e. the number of samples is equal to the image resolution). Image reconstruction requires N acquisitions. Taking the fastest DMD as an example, the imaging of a picture requires a sampling time of N/22 Ks. For a 32 pixel by 32 pixel image, imaging takes at least about 0.05 seconds. As the resolution of the image increases, the imaging speed decreases. For a 64 pixel by 64 pixel image, imaging takes at least about 0.2 seconds. In order to increase the imaging speed, people can reduce the sampling times to a certain extent by adopting compressed sensing, but the problem of mutual restriction between the imaging resolution and the imaging speed cannot be fundamentally solved. In addition, the DMD has another more outstanding technical problem. The operating spectrum of a DMD window is typically centered in the visible light band, with very low transmission in bands other than the visible light. Therefore, DMD-based single pixel imaging is limited in wide band imaging. Liquid crystal spatial light modulators (lcslms), as well as digital metal micromirror arrays (DMDs), are currently mainly used. The inventors have found that the following problems exist with the use of the above-described modulator: 1) The modulator is generally a narrow bandwidth response, i.e. only acts on light of a certain wavelength, thereby affecting the light field modulation effect; 2) Expensive and limited refresh rates.
Disclosure of Invention
In order to solve at least one technical problem in the background art, the invention provides an annular mask, a light field regulating method, a single-pixel imaging method and a system, which have wider spectral response capability and low manufacturing cost.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the first aspect of the invention provides a ring-shaped reticle.
An annular mask plate is annular in shape; the annular mask plate is covered with mask plate patterns, and the mask plate patterns consist of light-transmitting areas and light-non-transmitting areas.
Further, the mask pattern is provided with a mark recognition area.
Further, the mark recognition area is a full light transmission area or a full light non-transmission area.
Further, the annular mask pattern is converted from a rectangular mask pattern, and the rectangular mask pattern is also composed of a light-transmitting area and a light-non-transmitting area.
Further, the annular mask pattern is formed by buckling points at different positions on the annular mask material.
It will be appreciated that in other embodiments, the annular mask pattern may be converted in other forms, and those skilled in the art may specifically select any of the schemes for forming the annular mask pattern according to the actual situation, which will not be described here.
The second aspect of the invention provides a method for preparing the annular mask.
A preparation method of an annular mask plate comprises the following steps:
covering an opaque shading film on a substrate;
etching an annular mask pattern on the shading film;
and cutting out a substrate area covered by the annular mask pattern to manufacture the annular mask.
The third aspect of the invention provides a light field regulating method based on the annular mask.
A light field regulation and control method based on the annular mask plate comprises the following steps:
the sector ring of the annular mask plate is used as a modulation area at any moment to realize transient modulation of a target space;
and rotating the annular mask plate to change the modulation area of the annular mask plate so as to realize dynamic modulation of the target space.
Further, the light field regulation and control method comprises an active light field modulation mode and a passive light field modulation mode; in the active light field modulation mode, an active illumination light source is utilized to irradiate a local area of the annular mask plate, namely a modulation area at the moment; in the passive light field modulation mode, a target object is imaged on a certain local area, namely a modulation area, on the annular mask plate layout through an imaging lens under the condition of ambient illumination, and the modulation of a mask structure of the modulation area is completed through an image of the mask plate.
A fourth aspect of the invention provides a single pixel imaging method.
A single pixel imaging method comprising:
the light field regulation and control method of the annular mask plate is adopted to obtain a modulation area corresponding to a modulation target space in the annular mask plate of each period; the method comprises the steps of rotating an annular mask plate to realize periodic dynamic light field modulation of a target space;
detecting single-pixel detection values, the number of which is the same as that of the modulation areas of each period, through the annular mask plate;
and performing compressed sensing calculation reconstruction based on the modulation areas with set number of periods and the corresponding single pixel detection values, and realizing image information recovery of the target space.
A fifth aspect of the invention provides a single pixel imaging system.
The single-pixel imaging system is characterized by comprising an annular mask, a pixel detection device, a modulation region acquisition module and a processor;
the modulation region acquisition module is used for acquiring a modulation region corresponding to a modulation target space in the annular mask plate of each period by adopting the optical field regulation and control method of the annular mask plate; the method comprises the steps of rotating an annular mask plate to realize periodic dynamic light field modulation of a target space;
the pixel detection device is used for detecting single pixel detection values, the number of which is the same as that of the modulation areas of each period, through the annular mask plate;
the processor is used for performing compressed sensing calculation reconstruction based on the modulation areas with set number of periods and the corresponding single pixel detection values, and achieving image information recovery of the target space.
Compared with the prior art, the invention has the beneficial effects that:
the annular mask plate has low manufacturing cost and a mark recognition area, and the orientation of the mask plate can be accurately determined by a mark bit mode, so that the modulation precision is improved; the light field modulation based on the annular mask plate has wider spectral response capability, can realize modulation of a plurality of light wave bands, including modulation of visible light, infrared and ultraviolet wave bands, and can also realize a single-pixel associated imaging system by combining with a compressed sensing technology.
Advantages of the invention over conventional single pixel imaging: the single-pixel imaging based on annular single mask modulation can realize continuous and rapid light field modulation, so that continuous and rapid single-pixel imaging can be realized.
The optical field modulation based on the annular mask has wider spectral response capability. The modulation of a plurality of light wave bands including visible light, infrared and ultraviolet wave bands can be realized, and further, wide-spectrum imaging of a plurality of spectrum bands can be realized by adding a beam splitting light path and a plurality of spectrum band single-pixel detectors at the rear end of the beam splitting light path.
Additional aspects of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
FIG. 1 is a schematic structural diagram of an annular mask plate according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an embodiment 1 of a design ring reticle pattern of the present invention;
FIG. 3 is a schematic diagram of an embodiment 2 of the present invention for designing a ring reticle pattern;
FIG. 4 is a schematic diagram of an embodiment 3 of the present invention for designing a ring reticle pattern;
FIG. 5 (a) is a diagram of an active control response based on a ring mask according to an embodiment of the present invention;
FIG. 5 (b) is a schematic diagram of an active control principle based on a ring mask according to an embodiment of the present invention;
FIG. 6 (a) is a diagram of a corresponding object for passive regulation based on a ring mask according to an embodiment of the present invention;
FIG. 6 (b) is a schematic diagram of a passive regulation principle based on a ring mask according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of an active control entity based on a ring mask with a flag bit according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of a passive regulation object based on an annular mask with a flag bit according to an embodiment of the present invention;
FIG. 9 (a) is a schematic illustration of a single pixel imaging embodiment of the present invention;
FIG. 9 (b) is a single pixel imaging modulation schematic diagram of an embodiment of the present invention;
FIG. 10 (a) is a schematic diagram of modulation of an optical field by an elongated mask according to an embodiment of the present invention;
FIG. 10 (b) is a graph of the modulated intensity waveform of the light field of the strip mask according to an embodiment of the present invention;
FIG. 11 (a) is a real object image of an embodiment of the present invention;
FIG. 11 (b) is a graph of imaging results for an embodiment of the present invention;
fig. 11 (c) is a corrected diagram of the embodiment of the present invention.
Wherein, 1 projection lens, 2 annular mask, 3 drive arrangement, 4 illumination light source, 5 collecting lens, 6 barrel detector.
Detailed Description
The invention will be further described with reference to the drawings and examples.
It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present invention. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.
< annular mask >
The embodiment provides an annular mask, wherein the annular mask is annular in shape; the annular mask plate is covered with mask plate patterns, and the mask plate patterns consist of light-transmitting areas and light-non-transmitting areas.
In a specific implementation, the annular mask pattern can be represented by a 0-1 binary random matrix; wherein 1 corresponds to the light transmission area of the annular mask pattern and 0 corresponds to the light non-transmission area of the annular mask pattern. As shown in fig. 1, the white area corresponds to 1 and is a light transmitting area of the annular mask, and the black area corresponds to 0 and is a light non-transmitting area of the annular mask.
In another embodiment, the annular reticle pattern has a logo recognition area. The mark identification area is a full-light-transmission area or a full-light-non-transmission area.
It should be noted that, in other embodiments, the tag identification area may be other types of areas.
The annular mask pattern can be realized by adopting the following embodiments:
example 1
The annular mask pattern is formed by converting rectangular mask patterns. For example: the rectangular mask pattern is also represented by a 0-1 binary random matrix. The specific process is shown in fig. 2:
designing a rectangular mask pattern, wherein the rectangular mask pattern is represented by a 0-1 binary random matrix; wherein 1 corresponds to a light transmission area of the annular mask pattern, and 0 corresponds to a light non-transmission area of the annular mask pattern;
and converting the rectangular mask pattern into an annular mask pattern.
The specific process of converting the rectangular mask pattern into the annular mask pattern comprises the following steps:
and converting the pattern of the rectangular mask plate into narrow circular rings with gradually changed inner diameters according to rows, then splicing the narrow circular rings in sequence, and filling the narrow circular rings into a circular ring area of a preset annular mask plate to form the annular mask plate pattern.
Example 2
In the process of the annular mask pattern, a scheme shown in fig. 3 is adopted, and in fig. 3, a random (0, 1) binary matrix is generated, and an annular coding region is generated. The two are overlapped to form an annular random mask pattern.
Example 3
In the process of annular mask pattern, a scheme shown in fig. 4 is adopted, in fig. 4, an annular mask region is generated, dots are randomly buckled in the region, and each white dot represents a light transmission point.
It will be appreciated that in other embodiments, the annular mask pattern may be converted in other forms, and those skilled in the art may specifically select the design of the annular mask pattern according to the actual situation, which will not be described here.
< preparation method of annular mask >
The preparation method of the annular mask plate comprises the following specific processes:
covering an opaque shading film on a substrate;
etching an annular mask pattern on the shading film;
and cutting out a substrate area covered by the annular mask pattern to manufacture the annular mask.
In this embodiment, the substrate is made of a broad spectrum transmissive material. For example: a broad spectrum transmission material such as artificial quartz glass is selected as a substrate.
In some embodiments, in order to accurately grasp the precise angular position of the annular reticle, the precise position of the annular reticle may be monitored, or otherwise controlled, in real time, for example, by a controllable stepper motor. Here, a method for determining the orientation of a mask plate by means of a mark bit is designed. In the process of designing and manufacturing the mask, an all 0 area (such as a rectangular area or other shape areas) is added to be used as a mark recognition area. In this case, the "all 0 modulation" can identify the start position of each cycle.
It should be noted that, in other embodiments, the tag identification area may be other types of areas.
< method for controlling light field based on annular mask >
The following provides a light field regulation and control method based on the annular mask plate, which specifically comprises the following steps:
the sector ring of the annular mask plate is used as a modulation area at any moment to realize transient modulation of a target space;
and rotating the annular mask plate to change the modulation area of the annular mask plate so as to realize dynamic modulation of the target space.
The annular mask plate is rotated for a circle, and the modulation of a target space in one period is completed; the steps are repeated continuously, so that the periodic modulation of the target space is realized.
In a specific implementation, the optical field modulation process based on the annular mask plate is divided into active optical field modulation and passive optical field modulation.
Active light field modulation: as shown in fig. 5 (a) and 5 (b). A "local area" of the annular reticle 2, i.e. the "modulation area" at the moment, is illuminated by the active illumination source 4. The structured light formed by the local structure of this region is projected through the projection lens 1 onto a specific "target object" (or "target space") forming an active structured light field illumination of this "target object".
Wherein, rotation of the annular mask plate 2 is realized by adopting a driving device 3.
Here, the driving device 3 may be a motor, or may be implemented by other existing driving mechanisms.
Passive light field modulation: as shown in fig. 6 (a) and 6 (b). The target object is imaged on a certain local area, namely a modulation area, on the layout of the annular mask 2 through the projection lens 1 under the ambient light condition. The modulation of the mask structure in the modulation region is completed through the image of the mask plate.
Wherein, rotation of the annular mask plate 2 is realized by adopting a driving device 3.
Here, the driving device 3 may be a motor, or may be implemented by other existing driving mechanisms.
Whether actively modulated or passively modulated, the mask is rotated by a braking device, and the 'modulation structure' of the mask modulation area to the target space is continuously changed along with the time change. One rotation is completed to finish one cycle. And the method is repeated continuously, so that periodic modulation is realized.
In the corresponding embodiments of fig. 5 (a) -6 (b), in order to accurately grasp the accurate angular position of the annular mask, the accurate position of the annular mask may be monitored or controlled in real time by a controllable stepper motor.
Further, in order to accurately grasp the accurate angle position of the annular mask, the embodiment designs a method for determining the orientation of the mask by means of marking bits. In the process of designing and manufacturing the mask, a rectangular all-0 area is added and is used as a mark recognition area. In this case, the "all 0 modulation" allows us to discern the starting position of each cycle. The corresponding active and passive modulation is the same as described above, as shown in fig. 7-8.
< Single Pixel imaging method >
Encoding an object requires the generation of a varying structural light field, depending on the imaging mechanism of the associated imaging. In conventional single-pixel experiments, a spatial light modulator (e.g., a DMD) generates varying spatial structured light at a refresh frequency, which encodes objects in sequence. During the multiple modulations required to image a frame of picture we assume that the object is stationary. This process requires a relative change between the spatial light modulation pattern and the object.
The optical field modulation based on a single fixed optical mask is the same as the DMD modulation in that both modulation modes require relative change between the spatial light modulation pattern and the object; the difference is that the dynamic encoding of the object is not performed by the spatial light modulator refreshing the structured light that generates the changes, but rather by the relative movement of the moving object over the fixed reticle.
Taking passive light field modulation (imaging an object onto a modulation device) as an example. The object is imaged onto an image plane (i.e. the plane in which the detector target surface is located in a conventional camera) by an optical imaging system. On the image plane, a fixed optical reticle (typically a binary amplitude reticle) is placed. For ease of discussion, the mask used is a pair of elongated optical masks that produce a pair of stationary structured light illuminations on the object plane. The size of the image formed by the object is assumed to be far smaller than the area of the mask plate, and only occupies a part of the whole mask plate, namely a 'local area'.
The complete process of the correlation imaging based on the light field modulation of the single fixed optical mask consists of a coding and detection reconstruction process.
The principle of optical encoding is shown in fig. 10 (a) and 10 (b) by taking an elongated mask as an example. The long-strip checkerboard represents the fixed optical mask plate, and the smiling face represents the observation targetThe image is formed on the mask plate through an imaging system. The mask is binary (0, 1) transmissive, the object image is imaged onto the mask, and the transmitted light intensity is collected by a single pixel detector. The object image (with the motion of the object) translates from left to right along the horizontal direction. When the moving object image completely enters the mask region, it is considered that this time is the starting time of the modulation process. When the right end of the moving object starts to move out of the mask region, the right boundary coincides, and the moment is regarded as the end moment of the modulation process. We divide the modulation process into equally spaced K instants. t is t i Indicating the i-th moment, i=1, 2,..k is the index flag, t 1 To be the initial time of the modulation process, t K Which is the last moment of the modulation process. At any time t i The mask region corresponding to the object image is defined as a local light field modulation structure (abbreviated as a local structure, and is marked as P) i ). Here, the "partial structure" is set to be square, and the area is slightly larger than the actual size of the object. Because the spatial structure distribution of the optical mask is random, the local structure is continuously changed along with the relative motion between the object and the mask, thereby realizing the light field modulation of continuous change of the image.
At t i At a moment when the object image is in a local structural area, the detection value of the moment is y i . Every time an object image traverses K times on the mask, there are corresponding K "partial structures" that make up { P i } K The corresponding detection value sequence is { y } i } K 。
Let the resolution of the strip mask be AxB (B > A) (unit: pixel), and the resolution of the target space be AxA. Each time an object moves by one pixel, a new local structure is corresponding. Therefore, the object moves through the (B-A+1) sub-local structure along the long side of the mask in the whole process, so that the number K of the detection value sequences is= (B-A+1).
{P i } K And corresponding detection value { y } i } K And forming a group of structured light illumination-single pixel detection values, so that the spatial image of the object can be calculated through a compressed sensing and other reconstruction algorithms.
When an object moves, an image formed on the optical mask plate can be displaced. Because the structure of the reticle is random, the local light field modulation experienced by the image as it moves to different positions, i.e., the local structure of the reticle upon which the object image coincides, will change. This mechanism produces the "varying light field modulation" required for single pixel imaging. If a certain measure is adopted, the real-time position of the object on the illumination structure can be recorded, and meanwhile, the corresponding object light intensity is detected through the single-pixel detector, so that a group of illumination structure and single-pixel detection values can be constructed, and further single-pixel imaging can be realized.
In practice we need a "relative motion" between the object and the structured light illumination to achieve a continuously varying modulation. In order to achieve relative motion between the object and the structured light illumination of the stationary reticle, one effective implementation is to make the reticle annular in shape and place it on a rotatable wheel. When the rotating wheel rotates at a constant speed, continuous and periodic light field modulation of an imaging area can be realized.
Because the light field modulation is periodic, the annular mask plate corresponds to one period every time the annular mask plate rotates, and the position of the annular mask plate can be obtained by setting a zone bit or judging the gesture of the rotating wheel in other modes, so that the annular mask plate corresponds to and is associated with a single pixel detection value.
Based on the annular mask light field modulation technology, single-pixel imaging sampling based on light field regulation and control can be realized. The next step is to reconstruct the image based on the sampled data and the modulation scheme. In the scheme, a compressed sensing reconstruction algorithm is used, so that the spatial information of the object can be effectively extracted from the limited continuous modulation pattern.
In order to achieve real-time correlated imaging based on single fixed optical reticle light field modulation, continuous rapid changes in light field modulation need to be achieved. For this reason, the optical mask is designed to be annular, and continuous and rapid rotation can be realized through a braking device and the like.
As shown in fig. 9 (a) and 9 (b), the single-pixel imaging method of the present embodiment includes:
the light field regulation and control method of the annular mask plate is adopted to obtain a modulation area corresponding to a modulation target space in the annular mask plate of each period; the method comprises the steps of rotating an annular mask plate to realize periodic dynamic light field modulation of a target space;
detecting single-pixel detection values, the number of which is the same as that of the modulation areas of each period, through the annular mask plate;
and performing compressed sensing calculation reconstruction based on the modulation areas with set number of periods and the corresponding single pixel detection values, and realizing image information recovery of the target space.
In this embodiment, the modulation process of the annular mask plate on the target space is as follows:
the sector ring of the annular mask plate is used as a modulation area at any moment to realize transient modulation of a target space;
and rotating the annular mask plate to change the modulation area of the annular mask plate so as to realize dynamic modulation of the target space.
Specifically, the annular mask plate is rotated, so that the modulation area of the annular mask plate changes to the modulation area of the target space;
rotating the annular mask plate for a circle to finish the modulation of a target space in one period;
the steps are repeated continuously, so that the periodic modulation of the target space is realized.
The annular mask plate modulates the target space in an active light field modulation mode and a passive light field modulation mode; in the active light field modulation mode, an active illumination light source is utilized to irradiate a local area of the annular mask plate, namely a modulation area at the moment; in the passive light field modulation mode, a target space is imaged on a certain local area, namely a modulation area, on the annular mask plate layout through an imaging lens under the illumination condition of surrounding environment, and the modulation of the mask structure of the modulation area is completed through the image of the mask plate.
Single pixel detection process based on annular mask light field modulation:
(1) imaging the object onto the reticle. The imaging lens images the object onto the mask. And selecting a proper optical lens to enable the image of the target space to fall in the modulation area of the mask. The single-side size of the object image is not larger than the transverse width of the mask modulation area.
(2) And driving the mask plate to periodically rotate at a stable angular speed. When the mask is rotated at a constant speed, a single-pixel detector positioned in the transmission area continuously collects signals to generate periodic signals.
Synchronization of light field modulation and signal acquisition:
because the light field modulation and the signal acquisition based on the annular mask are periodic. Therefore, some measures are required to achieve its synchronicity. In order to do this, various measures can be taken, including obtaining the angular position of the reticle in real time by means of a controllable motor.
Here, a modulation, acquisition synchronization achieved by means of flag bits is proposed. For a rectangular coding structure with the size of A multiplied by B, introducing an all-zero matrix with the size of A multiplied by C to complement the coding matrix, and taking the all-zero matrix as a flag bit. Then, the strip binary mask pattern containing the marker bit is changed into a ring pattern. And (5) obtaining a mask distributed in a ring shape, and manufacturing the ring-shaped mask plate into a disc shape.
The reconstruction process comprises a data selection and image calculation reconstruction process.
Similar to the principle of datase:Sub>A selection based on correlated imaging of light field modulation of ase:Sub>A single fixed elongated optical reticle, for ase:Sub>A reticle with resolution A×B, B-A+1 "local structures" are obtained in total for each cycle, corresponding to the same number of single-pixel detection values.
And performing compressed sensing calculation reconstruction by using the local structure and the corresponding single pixel detection value. Compressed sensing achieves image information recovery by using undersampled data. In our experiments, ase:Sub>A total of B-A+1 sampled datase:Sub>A were obtained, and the resolution of the object was A 2 > (B-A+1), thus solving the object image as an undersampled problem.
In order to realize undersampling reconstruction, compressed sensing utilizes the ubiquitous data sparsity characteristic in images, and reconstruction is realized by solving the following optimization problem. If the light field modulation process is expressed as:
Y K×1 ＝M K×n X n×1
wherein M is m×n Is a two-dimensional matrix of sampling bases, i.e. representing a mask of A×B pixels, Y m×1 For sampling the obtained vector of detection values, X n×1 In the form of a target spatial column vector. K is the number of samples, n=a 2 Is the image resolution. Typically, K < n.
At this time, the corresponding optimization problem can be expressed as:
wherein the method comprises the steps of
Referring to the square of the Y-MX two norms, ψ (X) represents the sparse constraint regularization term of X, ++>
Representing the finally reconstructed image function, solved +.>
Should satisfy make->
Minimum. Alternative calculation schemes are as follows: the total variation is used as a sparse constraint regularization method.
The two-dimensional matrix is used in the calculation, and the actual annular mask plate and the two-dimensional matrix have certain deformation. Thus, the reconstructed object is also deformed. A transformation is required to obtain the correct image of the target. The process is the inverse process of converting the two-dimensional rectangular mask code into the annular mask. As shown in fig. 11 (a) -11 (c).
< Single Pixel imaging System >
As shown in fig. 9 (b), the single-pixel imaging system provided in this embodiment includes an annular mask, a pixel detection device, a modulation region acquisition module, and a processor. In fig. 9 (b), the pixel detection means is implemented using a barrel detector 6. A collection lens 5 is also provided before the drum detector for acquiring the modulation area.
The modulation region acquisition module is used for acquiring a modulation region corresponding to a modulation target space in the annular mask plate of each period by adopting the optical field regulation and control method of the annular mask plate; the method comprises the steps of rotating an annular mask plate to realize periodic dynamic light field modulation of a target space;
the pixel detection device is used for detecting single pixel detection values, the number of which is the same as that of the modulation areas of each period, through the annular mask plate;
the processor is used for performing compressed sensing calculation reconstruction based on the modulation areas with set number of periods and the corresponding single pixel detection values, and achieving image information recovery of the target space.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
1. An annular mask plate is characterized in that the annular mask plate is annular in shape; the annular mask plate is covered with mask plate patterns, and the mask plate patterns consist of light-transmitting areas and light-non-transmitting areas; the mask pattern is provided with a mark identification area, and the mark identification area is a full-light-transmission area or a full-light-non-transmission area; the annular mask pattern is formed by converting a rectangular mask pattern, and the rectangular mask pattern also comprises a light transmission area and a light-proof area; and converting the pattern of the rectangular mask plate into narrow circular rings with gradually changed inner diameters according to rows, then splicing the narrow circular rings in sequence, and filling the narrow circular rings into a circular ring area of a preset annular mask plate to form the annular mask plate pattern.
2. The annular reticle of claim 1, wherein the annular reticle pattern is formed from points on the annular mask material that snap to different locations.
3. A method of making an annular reticle as claimed in any one of claims 1 to 2, comprising:
covering an opaque shading film on a substrate;
etching an annular mask pattern on the shading film;
and cutting out a substrate area covered by the annular mask pattern to manufacture the annular mask.
4. A light field modulation method based on the annular mask plate according to any one of claims 1-2, comprising:
the sector ring of the annular mask plate is used as a modulation area at any moment to realize transient modulation of a target space;
and rotating the annular mask plate to change the modulation area of the annular mask plate so as to realize dynamic modulation of the target space.
5. The method for adjusting and controlling the light field of the annular mask plate according to claim 4, wherein the light field adjusting and controlling method comprises an active light field modulation mode and a passive light field modulation mode; in the active light field modulation mode, an active illumination light source is utilized to irradiate a local area of the annular mask plate, namely a modulation area at the moment; in the passive light field modulation mode, a target object is imaged on a certain local area, namely a modulation area, on the annular mask plate layout through an imaging lens under the condition of ambient illumination, and the modulation of a mask structure of the modulation area is completed through an image of the mask plate.
6. A single pixel imaging method, comprising
Acquiring a modulation region corresponding to a modulation target space in the annular mask plate of each period by adopting the light field regulation method of the annular mask plate according to any one of claims 4 to 5; the method comprises the steps of rotating an annular mask plate to realize periodic dynamic light field modulation of a target space;
detecting single-pixel detection values, the number of which is the same as that of the modulation areas of each period, through the annular mask plate;
and performing compressed sensing calculation reconstruction based on the modulation areas with set number of periods and the corresponding single pixel detection values, and realizing image information recovery of the target space.
7. The single-pixel imaging system is characterized by comprising an annular mask, a pixel detection device, a modulation region acquisition module and a processor;
the modulation region acquisition module is used for acquiring a modulation region corresponding to a modulation target space in the annular mask plate of each period by adopting the light field regulation method of the annular mask plate according to any one of claims 4 to 5; the method comprises the steps of rotating an annular mask plate to realize periodic dynamic light field modulation of a target space;
the pixel detection device is used for detecting single pixel detection values, the number of which is the same as that of the modulation areas of each period, through the annular mask plate;
the processor is used for performing compressed sensing calculation reconstruction based on the modulation areas with set number of periods and the corresponding single pixel detection values, and achieving image information recovery of the target space.
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