Single-pixel microscopic detection system and method based on modulus and qualitative phase detection

Abstract

The application provides a single-pixel microscopic detection system and method based on modulus and qualitative phase detection. The system comprises a laser, a mirror, a microscopic objective, a tube lens, a spatial light modulator, an attenuating sheet, a collection lens, a photodetector, a pinhole, a data acquisition card and a computer. The single-pixel microscopic detection system and method based on modulus and qualitative phase detection (SPDM) utilizes a spatial light modulator, a digital micromirror device (DMD), to modulate object light, and then performs bucket detection and zero-frequency detection on two reflected light paths of the DMD, so as to simultaneously obtain modulus images and real part images. Since the real part images qualitatively reflect phase distribution, the SPDM is suitable for observing various samples, including transparent samples. The SPDM can be realized as an additional module of an ordinary microscope, which facilitates its application in optical microscopes.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical detection technology, in particular to a single-pixel microscopic detection system and method based on modulus and qualitative phase detection. BACKGROUND

[0002] In recent years, a new type of microscopic technology named single-pixel microscopy (SPM) has emerged. This technology aims to enhance the ability to acquire microscopic information by means of computational imaging principles. Unlike the traditional way of recording images by relying on array image sensors, SPM only uses a single detector to acquire microscopic information. This method not only expands the spectral range, improves the time resolution, and enhances the flexibility, but also realizes phase imaging. However, quantitative phase imaging through a digital micromirror device (DMD) is not ideal because it not only sacrifices the spatial resolution of imaging, but also greatly increases the complexity of the SPM system. This is quite unfavorable for SPM to move towards practical applications. In many applications (such as measuring blood cell concentration), accurate phase is not critical, and in such cases, qualitative phase imaging is sufficient. SUMMARY

[0003] The purpose of the present application is to provide a single-pixel microscopic detection system and method based on modulus and qualitative phase detection, in order to solve the problems of insufficient spatial resolution, slow imaging speed, and high system complexity of current detection methods, and to practically promote its transition from the laboratory to the field of practical applications.

[0004] The present application is implemented as follows:

[0005] A single-pixel microscopic detection system based on modulus and qualitative phase detection, comprising:

[0006] A laser for emitting laser light to form a coherent illumination light field;

[0007] A first mirror arranged on the laser light path of the laser, which functions to change the direction of the light path, converting the horizontal light path to the vertical direction, thereby facilitating the placement of the sample in a horizontal state;

[0008] A microscopic objective lens arranged behind the target object and on the laser light path behind the first mirror, for magnifying the image of the object;

[0009] A second mirror arranged on the laser light path behind the microscopic objective lens, which functions to change the direction of the light path, converting the vertical light path back to the horizontal direction, thereby facilitating the construction of the light path;

[0010] A tube lens arranged on the laser light path behind the second mirror, which clearly images the object light from the microscopic objective lens onto a spatial light modulator;

[0011] A spatial light modulator is arranged on the laser light path behind the tube lens and is placed at a position where the object image is clear, and is used for modulating the amplified object light.

[0012] An attenuation piece is arranged on the first reflected light path reflected by the spatial light modulator, and is used for attenuating the laser light to the working range of the first photodetector.

[0013] A first collection lens is arranged behind the attenuation piece and is placed on the first reflected light path reflected by the spatial light modulator, so as to converge the modulated and attenuated object light.

[0014] A first photodetector is arranged on the first reflected light path reflected by the spatial light modulator and is placed near the back focal plane of the first collection lens, and is used for collecting the total intensity of the modulated object light.

[0015] A second collection lens is arranged on the second reflected light path reflected by the spatial light modulator, so as to converge the modulated object light.

[0016] A pinhole is arranged on the second reflected light path reflected by the spatial light modulator and is placed at the back focal plane of the second collection lens, and is used for coupling the zero-frequency component of the modulated object light into the pinhole.

[0017] A second photodetector is arranged on the second reflected light path reflected by the spatial light modulator and is placed behind the pinhole, and is used for collecting the light passing through the pinhole and detecting the intensity of the zero-frequency component of the object light.

[0018] A data acquisition card is connected with the spatial light modulator, the first photodetector and the second photodetector respectively, and is used for performing analog-digital conversion and data acquisition on the synchronization information of the spatial light modulator, the total intensity information of the object light collected by the first photodetector and the intensity information of the zero-frequency component of the object light collected by the second photodetector.

[0019] A computer is electrically connected with the spatial light modulator and the data acquisition card respectively, and is used for controlling the spatial light modulator to load the base pattern, and processing, storing and displaying the measurement data collected by the data acquisition card.

[0020] Further, the present application can be realized according to the following technical scheme:

[0021] The wavelength of the laser emitted by the laser and the photodetector is selected according to the target object, that is, the detection wavelength suitable in the spectral range from ultraviolet to near infrared can be selected according to the target object, and the appropriate laser and photodetector are selected according to the detection wavelength.

[0022] The magnification of the microscope objective is 4X, the focal length is 45mm, and the numerical aperture is 0.1.

[0023] The focal length of the tube lens is 200mm, and the diameter is 50mm.

[0024] The spatial light modulator is a micromirror array composed of a plurality of micro mirrors, and the array size is 1024*768, and the size of each micro mirror is 13.6*13.6um 2 Each micro mirror corresponds to a storage unit, and can load a value of 0 or 1, thereby controlling the micro mirror to flip in two directions of ±12°.

[0025] The focal length of the first collection lens is 100mm, and the diameter is 40mm.

[0026] The focal length of the second collection lens is 150mm, and the diameter is 50mm.

[0027] The diameter of the pinhole is 15um.

[0028] The single-pixel microscopic detection method based on modulus and qualitative phase detection provided by the application comprises the following steps:

[0029] (1) building the single-pixel microscopic detection system described above;

[0030] (2) the laser emits laser and irradiates the target object to be detected;

[0031] (3) the laser after the target object to be detected passes through the microscope objective and the tube lens, and irradiates the spatial light modulator;

[0032] (4) under the control of the computer, the spatial light modulator loads the base pattern, and forms two reflected light paths, one of which performs object light total intensity signal detection, and the other of which performs object light zero-frequency component intensity signal detection;

[0033] (5) the data acquisition card collects the synchronous information, the object light total intensity signal and the object light zero-frequency component intensity signal after the spatial light modulator loads the base pattern;

[0034] (6) the computer processes the data collected by the data acquisition card to obtain the modulus image and the real part image of the target object to be detected.

[0035] The application can detect the static image of cells, crystals or silicon wafers, and can also detect dynamic imaging.

[0036] Compared with the prior art, the application has the following advantages:

[0037] The application is based on a single-pixel microscopic detection system and method (SPDM, here D represents two imaging modes of modulus and qualitative phase) of modulus and qualitative phase detection, which modulates object light by means of a spatial light modulator, then performs bucket detection and zero-frequency detection on two reflected light paths of the spatial light modulator respectively, so as to simultaneously obtain modulus images and real part images without complicated super-pixel phase shift and chessboard reference technology. Since the real part image can qualitatively reflect the phase distribution, the application is suitable for observation of various samples, including transparent samples. The single-pixel microscopic detection system has high sensitivity, so it can be applied to the field of weak light, and the sample can be detected by weak light, which greatly reduces the damage degree of the sample.

[0038] The application is based on the perfect combination of Hadamard base pattern and spatial light modulator, so that the structure of the device is simple and compact. By using a microscope objective, phase detection of smaller objects such as tissues and cells can be performed, and a spatial resolution of up to 1.95 μm (spatial frequency of 512 lp / mm) can be provided. By using a pinhole with a diameter of only 15 μm, the zero-frequency component of the modulated object light can be filtered more pure, so that the reconstructed object real part image is also more clear and accurate. The detection speed of the application is fast, and a pair of real-time video streams can be generated at a frame rate of 0.51 FPS, so that the processes such as dissolution and precipitation of crystals can be observed in real time. The spatial light modulator DMD can modulate any wavelength, and has high flip speed, which can greatly improve the imaging speed. The application can simultaneously obtain modulus and real part images, to a certain extent, optimizing the imaging operation process, and all types of objects can be imaged and detected, greatly widening the detection range of samples.

[0039] The single-pixel microscopic detection system provided by the application can be used as an additional module of an ordinary microscope, which provides convenience for its application in an optical microscope. And as a typical single-pixel detection mode, it can be applied to non-visible wavelengths such as terahertz, providing new possibilities for biomedical diagnosis, target recognition and industrial detection. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 Fig. 1 is a structural schematic diagram of a single-pixel microscopic detection system based on modulus and qualitative phase detection according to the application.

[0041] Figure 2 Fig. 2 is a detection result of oral epithelial cells as target objects after the system; Figure 2 (a) is a modulus detection result, Figure 2 (b) is a real part detection result.

[0042] Figure 3 Fig. 3 is an experimental result of sugar dissolution in water; Figure 3 (a) is a modulus detection result of sugar dissolution, Figure 3(b) is the result of the real part detection of sugar dissolution.

[0043] Figure 4 It refers to the detection results after the crystal is processed by the system, with the crystal as the target object. Figure 4 (a) is a photograph of the crystal taken with a mobile phone. Figure 4 (b) is the result of the real part test. Figure 4 (c) is the result of the modulus detection.

[0044] Figure 5 It is the detection result after the silicon wafer has passed through the system; Figure 5 (a) shows the results of real part detection on a silicon-based chip. Figure 5 (b) shows the results of silicon-based chip module value testing. Figure 5 (c) shows the results of the real part detection of the deep silicon etched wafer. Figure 5 (d) is the result of the deep silicon etched wafer modulus test.

[0045] In the diagram: 1. He-Ne laser; 2. First reflecting mirror; 3. Target object; 4. Microscope objective; 5. Second reflecting mirror; 6. Tube mirror; 7. Spatial light modulator; 8. Attenuator; 9. First collecting lens; 10. First photodetector; 11. Second collecting lens; 12. Pinhole; 13. Second photodetector; 14. Data acquisition card; 15. Computer. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings.

[0047] like Figure 1 As shown, the single-pixel microscopic detection system based on modulus and qualitative phase detection of the present invention includes: a He-Ne laser 1, a first reflecting mirror 2, a microscope objective 4, a second reflecting mirror 5, a tube mirror 6, a spatial light modulator 7, an attenuator 8, a first collecting lens 9, a first photodetector 10, a second collecting lens 11, a pinhole 12, a second photodetector 13, a data acquisition card 14, and a computer 15.

[0048] Among them, He-Ne laser 1 is used to emit laser light to form a coherent illumination field. He-Ne laser 1 adopts a helium-neon gas laser (Shanghai Hongyang, HN-1200) and emits laser light with a wavelength of 632.8nm.

[0049] The first reflecting mirror 2 is a 45° reflecting mirror, which is placed in the laser beam path of the He-Ne laser 1. Its function is to change the direction of the light path, transforming the horizontal light path emitted by the He-Ne laser 1 into a vertical one, thus facilitating the horizontal placement of the target object 3. The target object 3 is placed in the laser beam path reflected by the first reflecting mirror 2, and the laser light reflected by the first reflecting mirror 2 illuminates the target object 3.

[0050] The microscope objective 4 is positioned behind the target object 3 and on the laser path reflected by the first reflecting mirror 2. It is used to magnify the image of the target object so that it can detect tiny objects. The microscope objective 4 (Olympus, PLN 4X) has a magnification of 4X, a focal length of 45mm, and a numerical aperture of 0.1.

[0051] The second reflecting mirror 5 is a 45° reflecting mirror, which is set behind the microscope objective 4 in the laser light path. Its function is to change the direction of the light path, turning the vertical light path after passing through the microscope objective 4 back to the horizontal direction, thereby facilitating the construction of the light path.

[0052] The tube mirror 6 is positioned on the laser beam path after reflection from the second reflector 5. The tube mirror 6 has a focal length of 200mm and a diameter of 50mm. The spatial light modulator 7 is positioned behind the tube mirror 6 on the laser beam path, at a point where the object image is clear, and is used to modulate the magnified object light. The spatial light modulator 7 is a digital micromirror device (DMD) (V-7000, VIALUX). The DMD consists of many tiny aluminum alloy mirrors arranged in an array of 1024×768 pixels, with each micromirror measuring 13.6×13.6μm. 2 The object light from the microscope objective 4 passes through the second reflecting mirror 5, and then through the tube lens 6 to clearly image the target object onto the spatial light modulator 7.

[0053] The spatial light modulator 7 has two reflected light paths, named the first reflected light path and the second reflected light path. These two reflected light paths are used for barrel signal detection and zero-frequency signal detection, respectively. An attenuator 8, a first collecting lens 9, and a first photodetector 10 are sequentially arranged on the first reflected light path. A second collecting lens 11, a pinhole 12, and a second photodetector 13 are sequentially arranged on the second reflected light path.

[0054] The attenuator 8 is placed on the first reflected light path after the spatial light modulator 7 to attenuate the laser to within the allowable operating range of the first photodetector 10.

[0055] The first collecting lens 9 is positioned behind the attenuator 8 and on the first reflected light path after reflection from the spatial light modulator 7, used to converge the modulated and attenuated object light to the first photodetector 10. The focal length of the first collecting lens 9 is 100mm and the diameter is 40mm.

[0056] The first photodetector 10 is disposed on the first reflected light path after reflection from the spatial light modulator 7 and is placed near the rear focal plane of the first collecting lens 9 to collect the total intensity of the modulated light. The first photodetector 10 is a silicon-based single-pixel detector (PDAPC2, THORLABS) with advantages such as spectral response of 320nm to 1100nm and high sensitivity.

[0057] The second collecting lens 11 is disposed on the second reflected light path after reflection from the spatial light modulator 7, and is used to converge the modulated object light to the pinhole 12. The focal length of the second collecting lens 11 is 150mm and the diameter is 50mm.

[0058] The pinhole 12 is set in the second reflected light path after the spatial light modulator 7 and is placed at the rear focal plane of the second collecting lens 11. It is used to couple the zero-frequency component of the modulated object light into the pinhole 12. The core diameter of the pinhole 12 is only 15μm, which can filter the zero-frequency component of the modulated object light more purely, so that the reconstructed real image of the object is clearer and more accurate.

[0059] The second photodetector 13 is disposed on the second reflected light path after the spatial light modulator 7 and is positioned behind the pinhole 12. It is used to collect the light transmitted through the pinhole 12 and to detect the intensity of the zero-frequency component of the object light. The model of the second photodetector 13 is the same as that of the first photodetector 10.

[0060] Data acquisition card 14 is connected to spatial light modulator 7, first photodetector 10, and second photodetector 13, respectively, and is used to acquire synchronization information after the spatial light modulator 7 is loaded with a substrate pattern, total intensity information of the object light acquired by the first photodetector 10, and intensity information of the zero-frequency component of the object light acquired by the second photodetector 13. Data acquisition card 14 (USB-2020, MEASUREMENT COMPUTING) provides high-speed synchronous analog output channels, with each channel reaching a maximum speed of 20MS / s.

[0061] Computer 15 is electrically connected to spatial light modulator 7 and data acquisition card 14 respectively, and is used to control spatial light modulator 7 to load Hadamard substrate pattern, and to process, store and display measurement data acquired by data acquisition card 14.

[0062] The engineering principle of the single-pixel microscopic detection system of this invention is as follows: The light source is a He-Ne laser 1 with a wavelength of 632.8 nm. A first reflecting mirror 2 and a second reflecting mirror 5 are used to change the direction of the beam, thus facilitating the horizontal placement of the target object 3 and the subsequent construction of the optical path. A microscope objective 4 and a tube mirror 6 form a conventional microscope. The target object 3 and the spatial light modulator 7 are located on the object-image plane and the image plane, respectively. The spatial light modulator 7 (DMD) is composed of a micromirror array. The tilt angle of the micromirrors is ±12° with the normal direction of the DMD surface, thus the incident object light modulated by the DMD forms a pair of complementary structured beams in the two reflected optical paths. An attenuator 8 attenuates the laser in the inner reflected optical path. A first collecting lens 9 and a first photodetector 10 form a barrel detector to record the total intensity of the modulated object light. The modulated object light is focused onto a pinhole 12 by a second collecting lens 11 to obtain its Fourier spectrum. The pinhole 12 only allows the zero-frequency component to pass through and eventually reaches the second photodetector 13. This detection method is called zero-frequency detection. Based on the frame synchronization pulse of the spatial light modulator 7, the data acquisition card 14 acquires the barrel detection signal and the zero-frequency detection signal from the first photodetector 10 and the second photodetector 13, respectively. The computer 15 is electrically connected to the spatial light modulator 7 and the data acquisition card 14, respectively, and is used to control the spatial light modulator 7 to load the Hadamard substrate pattern, and to process, store and display the measurement data acquired by the data acquisition card 14.

[0063] The working process of this invention is as follows:

[0064] The Hadamard basis matrix sequence is generated using the Hadamard basis matrix, and is represented as follows:

[0065]

[0066] in H u and H v These are the u-th and v-th row vectors of the Walsh-Hadamard matrix H of order N. H represents u The transpose of. Due to It contains only 0s and 1s, making it ideal for binary on or off modulation of spatial light modulator 7.

[0067] For an object beam with a complex amplitude f, the modulated light in a reflected optical path is: The modulated light in the other reflected light path is in This represents the product of elements. In the first reflected light path, the barrel detection signal is proportional to the total intensity of the modulated light:

[0068]

[0069] Here, the summation is the summation of all matrix elements, η represents the detection efficiency, and takes into account... Hadama spectral components The difference between two signals, M(u,v) = α[B], can be used to determine this. (+) (u,v)-B (-) [u,v] is obtained, where α = 1 / η. From the entire set of base patterns... Based on all the bucket detection signals, the Hadamard spectrum matrix can be obtained:

[0070] M = α[B (+) -B (-) [ (3)

[0071] Performing an inverse Hadamard transform on the spectrum matrix M yields the magnitude image of the object:

[0072]

[0073] In the second reflected optical path, the zero-frequency detection signal is proportional to the intensity of the zero-frequency component of the modulated light:

[0074]

[0075] Substituting formula (1) into formula (5), then

[0076]

[0077] Where R = Σf can be regarded as a reference term. It is the Hadamard spectrum component of f. This represents the real part of the complex number. It can be seen that both the reference term R and the spectral component F(u,v) originate from the modulated object light, and the interference term obtained from the positive and negative basis patterns has a π phase shift. By differentiating the two signals, we obtain... Based on all the zero-frequency signals of the entire set of substrate patterns, we can obtain:

[0078]

[0079] For clarity, the reference term is represented in exponential form. Then, performing the inverse Hadamard transform on both sides of equation (7), we obtain:

[0080]

[0081] Where β = α / r, and considering that H is a real matrix, zero-frequency detection obtains the phase shift φ. r The real part image of the object. It can be seen from equations (4) and (8) that the modulus image and the real part image can be directly reconstructed from the difference between the barrel detection signal and the difference between the zero-frequency detection signal, respectively.

[0082] This invention targets oral epithelial cells, and the detection results after system processing are as follows: Figure 2 As shown. Figure 2 (a) is the modulus detection result. Figure 2 (b) shows the real part detection results. It can be seen that the modulus image can obtain the edge of the object, while the real part image can reflect the structural information contained in the phase.

[0083] Subsequently, to test dynamic imaging performance, the invention recorded the process of sugar dissolution in droplets. A pair of real-time video streams were generated at a frame rate of approximately 0.51 FPS. Figure 3 Rows (a) and (b) show the modulus and real part frames sampled from the slide, respectively. Note that the object within the box is not a sugar granule, but a speck of dust on the slide, which serves as a reference. It can be seen that this invention can not only capture changes in the sugar itself, but also detect the changes it causes in the surrounding solution.

[0084] Furthermore, this invention can detect grating structures formed by defects inside a crystal, and the detection results are as follows: Figure 4 As shown. Figure 4 (a) is a photograph of the crystal taken with a mobile phone. Figure 4 (b) is the result of the real part test. Figure 4 (c) shows the results of the modulus detection. The diffraction pattern of the internal grating of the crystal can be seen from this.

[0085] Finally, given the significant ease of switching to other wavelengths in this invention, we replaced the He-Ne laser 1 with a near-infrared 1550nm laser (PL-DFB-1550-C-1-SA-14BF, Xiaoxiao Photonics), and simultaneously replaced the corresponding silicon-based photodetector with an indium gallium arsenide photodetector (PDAPC4, THORLABS) with a detection wavelength of 800nm-2600nm. The silicon was then tested, and the results are as follows... Figure 5 As shown. Among them, Figure 5 (a) shows the results of real part detection on a silicon-based chip. Figure 5 (b) shows the results of silicon-based chip module value testing. Figure 5 (c) shows the results of the real part detection of the deep silicon etched wafer. Figure 5 (d) shows the results of modulus measurement on a deep silicon etched wafer. The structural characteristics of silicon are clearly visible in these results. This demonstrates that the system can be easily extended to non-visible wavelengths such as ultraviolet and near-infrared.

Claims

1. A single-pixel microscopy detection system based on modulus and qualitative phase probing, characterized in that, The system comprises a laser, a microscope objective, a tube lens, a spatial light modulator, a data acquisition card and a computer; the laser, the microscope objective, the tube lens and the spatial light modulator are sequentially arranged along a laser light path; and the target object to be detected is arranged on the light path between the laser and the microscope objective. The spatial light modulator is a digital micromirror device, and the spatial light modulator has two reflection light paths, one of which is sequentially provided with an attenuating sheet, a first collection lens and a first photodetector, and the other of which is sequentially provided with a second collection lens, a pinhole and a second photodetector; the former reflection light path is used for detecting a total intensity signal of object light, and the latter reflection light path is used for detecting an intensity signal of a zero-frequency component of the object light. The data acquisition card is connected with the spatial light modulator, the first photodetector and the second photodetector respectively, and is used for collecting synchronous information after the spatial light modulator loads a base pattern, the total intensity signal of the object light collected by the first photodetector and the intensity signal of the zero-frequency component of the object light collected by the second photodetector. The computer is connected with the spatial light modulator and the data acquisition card respectively, and is used for controlling the spatial light modulator to load the base pattern, and processing, storing and displaying the data collected by the data acquisition card.

2. The single-pixel microscopy detection system based on modulus and qualitative phase probing of claim 1, wherein, The digital micro-mirror device is a micro-mirror array composed of a plurality of micro mirrors, the micro-mirror array has a size of 1024x768, and each micro mirror has a size of 13.6x13.6 μm 2 .

3. The single-pixel microscopy detection system based on modulus and qualitative phase probing of claim 2, wherein, Each micro-mirror can be flipped to +12° or -12° under the control of the computer.

4. The single-pixel microscopy detection system based on modulus and qualitative phase probing of claim 1, wherein, A first mirror is arranged on the light path between the laser and the microscope objective, and a second mirror is arranged on the light path between the microscope objective and the tube lens; the first mirror is used for converting the horizontal light path emitted by the laser into a vertical direction, the second mirror is used for converting the vertical light path after passing through the microscope objective into a horizontal direction; and the target object to be detected is arranged on the light path between the first mirror and the microscope objective.

5. The single-pixel microscopy detection system based on modulus and qualitative phase probing of claim 1, wherein, The laser emits a monochromatic coherent light beam.

6. The single-pixel microscopy detection system based on modulus and qualitative phase probing of claim 1, wherein, The focal length of the first collection lens is 100 mm, and the diameter is 40 mm; the focal length of the second collection lens is 150 mm, and the diameter is 50 mm; and the diameter of the pinhole is 15 μm.

7. A single-pixel microscopy detection method based on modulus and qualitative phase detection, characterized in that, The method comprises the following steps: (1) building the single-pixel microscopic detection system according to claim 1; (2) the laser emits laser and irradiates the target object to be detected; (3) the laser after passing through the target object to be detected irradiates the spatial light modulator after passing through the microscope objective and the tube lens; (4) under the control of the computer, the spatial light modulator loads the base pattern and forms two reflection light paths, one of which is used for detecting the total intensity signal of the object light, and the other of which is used for detecting the intensity signal of the zero-frequency component of the object light; (5) the data acquisition card collects the synchronous information after the spatial light modulator loads the base pattern, the total intensity signal of the object light and the intensity signal of the zero-frequency component of the object light; (6) the computer processes the data collected by the data acquisition card to obtain the modulus image and the real part image of the target object to be detected.

8. The single-pixel microscopy detection method based on modulus and qualitative phase probing according to claim 7, characterized in that, The model and brand of the digital micromirror device are V-7000 and VIALUX respectively.

9. The single-pixel microscopy detection method based on modulus and qualitative phase probing of claim 7, wherein, The target object to be detected is a cell, a crystal or a silicon wafer.

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