CN207502929U - A kind of stacking diffraction imaging device - Google Patents

Abstract

The utility model discloses a laminated diffraction imaging device, which belongs to the fields of diffraction imaging and holographic imaging. In this method, the incident light containing object information is divided into multiple outgoing beams by using a beam splitting prism group, an optical fiber and other light splitting devices, and each outgoing beam corresponds to a receiving device; before entering the receiving device, the spatial light modulator or a fixed template is used to pair The amplitude, phase, or only one of the two distributions of each outgoing beam is adjusted to obtain a set of related diffraction patterns, which are then reconstructed using the stacked diffraction algorithm to obtain the amplitude and phase information of the object, that is, the hologram. With this device, it is possible to obtain the diffraction patterns of multiple objects at the same time by taking a photo at the same time, which greatly reduces the time for pattern reception, and there is no need to separate the spot when reconstructing the sample image. After the device is assembled, its parameters can be fixed at a certain value, and there is no need to repeat it when it is used again. Adjustment is conducive to industrial applications.

Description

A stacked diffraction imaging device

technical field

The invention belongs to the fields of diffraction imaging and holographic imaging, and specifically relates to dividing incident light containing object information into multiple sub-beams by using a spectroscopic device, and then adjusting the amplitude, phase or one of the two sub-beams to obtain multiple correlations. The diffraction pattern of the object is reconstructed using the stacked diffraction algorithm to obtain a holographic image of the object.

Background technique

Ptychography is a new method of obtaining holograms of objects developed in the past ten years. Different from traditional holography, this method does not require reference light, but obtains holograms by changing the relative position of light waves and objects. A series of diffraction spots, the spot irradiated on the object overlaps with at least one other spot. Diffraction spots are recorded by CMOS, CCD and other devices, and then computer programs can be used to iteratively calculate the diffraction of these spots to obtain the phase and amplitude information of the object and realize the holographic imaging of the object (J. M. Rodenburg, Adv. Imag. Elect. Phys . 150, 87-184, 2008). If the light wave function is unknown, the light wave function information can also be obtained (P. Thibault et al, Ultramicroscopy, 109, 338-343, 2009). However, the traditional stacked diffraction method needs a micromechanical device to move the spot and the sample, which puts high demands on the mechanical device. In order to improve the measurement accuracy, this method needs to increase the overlapping area between each spot, which makes the time cost of iterative calculation Consumption is larger. G. Zheng et al. proposed a coherent diffraction imaging method in Fourier space in 2013 on the basis of the traditional stacked diffraction method. This method does not require mechanical devices, but uses high-energy light-emitting diodes to generate laser arrays, and uses CCDs to receive images from different diodes. Spot (G. Zheng et al, Nature Photonics, 7, 739-745, 2013); in order to improve the measurement accuracy, this method also needs to increase the number of diodes or change the shape of the light-emitting array, which also increases the complexity of the device to a certain extent. O. Cohen et al. proposed a single-exposure stacked diffraction technique, which uses a porous array to obtain a group of light spots containing object information on the back focal plane of the 4f system, which is equivalent to the diffraction spot group obtained by traditional stacked diffraction; since only One exposure, so the spot receiving time is greatly shortened; however, this method needs to separate each diffraction spot from the pattern of one exposure, which increases the difficulty of post-processing (O. Cohen et al, Optica, 3, 9-14, 2016 ). In the published patent document (application number 201610028448.3), Dong Zhao and others proposed a holographic method based on phase lamination diffraction, that is, using a spatial light modulator or a phase template to change the phase of incident light, thereby achieving lamination without mechanical movement Diffraction, thereby reducing the acquisition time; this method does not need to separate the spot during phase reconstruction, and the iteration time is shorter than the traditional stacked diffraction. However, this method still needs to adjust the phase template, which still requires a certain data acquisition time.

Contents of the invention

The purpose of the present invention is to propose a layered diffraction device capable of simultaneously receiving differently modulated incident light containing object information, so as to quickly reconstruct the object while reducing the receiving time. In this method, the incident light containing object information is divided into a plurality of outgoing light beams by using a light splitting device such as a beam splitting prism group and an optical fiber, and each outgoing light beam corresponds to a receiving device; before entering the receiving device, a spatial light modulator or a fixed template is used to pair The amplitude, phase, or only one of the distributions of each outgoing beam is adjusted to obtain a set of related diffraction patterns, which are then reconstructed using the stacked diffraction algorithm to obtain the amplitude and phase information of the object, that is, the hologram.

Technical scheme of the present invention is as follows:

A layered diffraction imaging device, which comprises in sequence according to the direction of incident light beam propagation:

(1) A spectroscopic device that divides the incident beam into several outgoing beams;

(2) A beam adjustment device corresponding to each outgoing beam, which can adjust the amplitude and phase distribution of the beam, or only adjust one of the two;

(3) The image receiving device corresponding to each outgoing beam.

As for the spectroscopic device, it can use a prism group, a half-reflecting mirror group or an optical fiber bundle to split the light, and the intensity of the split outgoing beams should be as equal as possible.

For the beam adjustment device, it is required that the device can adjust the beam amplitude or phase distribution, or adjust both distributions at the same time, instead of adjusting the light amplitude or phase as a whole; The adjustment of the device does not affect other beams; and each adjustment device adjusts the beams differently. The beam adjustment device can be a spatial light modulator or a fixed template, such as a phase plate, an amplitude adjustment plate with randomly distributed light transmittance, and the like.

For the image receiving device, it is also required that each outgoing light beam corresponds to an image receiving device. All image receiving devices should shoot at the same time. To achieve this purpose, a shutter can be placed at the entrance of incident light (that is, in front of the spectroscopic device). When the shutter is opened, all image receiving devices receive the pattern at the same time. In order to reconstruct the holographic image of the object more effectively, all image receiving devices should be perpendicular to the main axis of the corresponding light beam, and the incident point of the main axis should be at the center of the photosensitive surface of the image receiving device. The general image receiving device can be a complementary metal oxide semiconductor (CMOS) industrial camera, a charge-coupled device (CCD) camera, etc.

Due to the different light splitting of different beams in the spectroscopic device, the light intensity experienced by different outgoing beam receiving devices may be different. In order to improve the accuracy of reconstructing the holographic image of the object, a light attenuating device (such as a light attenuating sheet) is placed in front of part or all of the receiving devices. To ensure that the light intensity received by each receiver is basically the same.

Due to the inconsistency of the optical path difference from the object, the diffraction status of the pattern received by the receiver may also be inconsistent, which will bring some complexity to the later data processing; in order to improve the reconstruction efficiency of the holographic image of the later object, the device allows each image to receive The optical path difference from the device to the first split point of the incident beam is the same (in practice, the error should generally not exceed 0.5 microns), so as to ensure that the optical path difference between them and the object is consistent.

Technical effect of the present invention is as follows:

(1) When the present invention performs layered diffraction on an object, it can obtain the diffraction patterns of multiple objects at the same time by taking a photo, which greatly reduces the pattern receiving time. At this time, the pattern receiving time generally only depends on the exposure processing time of the receiving device.

(2) The present invention reconstructs the sample image without separating the spot.

(3) After the device of the present invention is assembled, its parameters can be fixed at a certain value, and there is no need for repeated adjustments when it is used again, which is conducive to industrial application.

Description of drawings

Fig. 1 A diagram of a stacked diffractive imaging device, 1 is the shutter, 2, 3, 4 are beam-splitting prisms, 6 is a spatial light modulator, 8 is a CMOS industrial camera, 9 is the device casing, and 10 is a beam-splitting prism fixture.

Fig. 2 Typical loading diagram of spatial light modulator 6.

Figure 3 (a) Amplitude type sample, (b) typical diffraction of the light loaded with its information after passing through the spatial light modulator, (c) pattern reconstruction intensity image; the scale bar in figure a is the smallest unit is millimeter, figure b, c The middle scale length is 2 mm.

Figure 4 Another layered diffraction imaging device diagram, 1 is the shutter, 2, 3, 4, 5 are beam splitters, 61-65 are checkerboard grid-like amplitude templates, 7 is the attenuation film, 81-85 are CMOS industrial cameras, 9 is the device shell.

Fig. 5 (a) A typical grid-like amplitude template, (b) the complementary template of this template.

Fig. 6 (a) The amplitude distribution of the simulated sample, (b) the reconstructed amplitude image, (c) the phase distribution of the simulated sample, (d) the reconstructed phase image.

Detailed ways

The present invention will be further described below by example. It should be noted that the purpose of the published embodiments is to help further understand the present invention, but those skilled in the art can understand that various replacements and modifications are possible without departing from the spirit and scope of the present invention and the appended claims . Therefore, the present invention should not be limited to the content disclosed in the embodiments, and the protection scope of the present invention is subject to the scope defined in the claims.

Embodiment 1: A stacked diffractive imaging device using a phase-type spatial light modulator

A laminated diffraction imaging device, the main structure of which is shown in Figure 1. The beam adjustment device uses a transmission-type spatial light modulator 6, which is fixed inside the device (the fixture is not shown), and the incident spatial light modulator 6 Both the light and exit light sections have their own angled polarizers (not shown) to ensure that they operate in phase-only mode.

The other parts of the device are described in detail below according to the propagating direction of the incident light beam. The device includes a shutter 1, and when the shutter 1 is pressed, all receiving devices charge-coupled device (CCD) industrial cameras 8 take pictures at the same time. The exposure time of the camera 8 is adjustable, and the minimum is 0.005 seconds.

The spectroscopic device of the device is composed of a prism group composed of 3 beam-splitting prisms. These beam-splitting prisms can divide the incident light into two beams of light with the same light intensity, that is, transmitted light and reflected light. They are fixed by corresponding fixtures 10 . The incident light beam is firstly split at the dichroic prism 2. As shown in Figure 1, the reflected light propagates upwards through the prism 2, and is divided into two beams of light again by the prism 3, one of which is reflected by the prism 3 and spreads horizontally to the right, and the other beam is transmitted and continues to propagate upward; these two beams The light passes through its corresponding spatial light modulator 6 and reaches the corresponding receiving device CCD industrial camera 8 . Another beam of light is transmitted through the prism 2, similar to the beam of light reflected by the prism 2, it is divided into two beams of light again by the prism 4, and then the two beams of light pass through the corresponding spatial light modulator 6 and reach the corresponding CCD Industrial camera8. , because each outgoing beam is equivalent to the product of light splitting twice, so the light intensity of these outgoing beams is the same, so this device does not use an optical attenuation device.

In specific applications, for the convenience of use, the internal components of the device are placed and fixed in the shell 9 . All CCD industrial cameras 8 have the same optical path difference to the central position of the beam splitter 2 (that is, where the incident light is split), and their distances to the corresponding spatial light modulators are also the same. In this example, the distances from prism 2 to prisms 3 and 4 are 50 millimeters respectively, the distances from prisms 3 and 4 to their corresponding industrial cameras 8 are also 50 millimeters, and the distances from the spatial light modulator to the photosensitive surface of corresponding industrial cameras 8 are all 50 millimeters. is 20mm. When applied, all spatial light modulators are loaded with different random phases, and a typical loading diagram is shown in Figure 2

An intermediate translucent amplitude-type sample (shown in Figure 3a) is employed to demonstrate the device application. The semi-transparent area in the center of the sample is roughly square, with a side length of 3 mm, and the surrounding area is opaque. The parallel laser beam with a wavelength of 532 nm passes through the sample and enters the stacked diffraction device. The light beam is adjusted so that it is vertically incident on the center of the splitter prism 2, so that all industrial cameras 8 can receive images of the sample in their central area. When the shutter is opened, these cameras simultaneously capture images of the sample, and these images are modulated by a spatial light modulator. The acquisition time depends on the exposure processing time, here 0.005 sec.

The CCD industrial camera transmits the received pattern to the computer for processing through a wired or wireless connection device (not shown in the figure). At this time, it can be directly processed according to the traditional stacked diffraction iterative algorithm without separating the spot. Figure 3b and c subfigures show the typical diffraction pattern and the intensity distribution obtained by the stacked diffraction algorithm, respectively, and the calculation time is 6 seconds. It can be seen that the device can perform fast lamination diffraction imaging of objects.

Embodiment 2: A stacked diffraction imaging device using a checkerboard grid-like amplitude template

A stacked diffraction imaging device, the main structure of which is shown in Figure 4. The beam adjustment device uses amplitude-type lattice templates 61-65, which are fixed inside the device (fixtures are not shown), and its working part consists of several grids Composition, the grid is divided into two types: fully transparent and translucent or opaque. The transmittance of the former is close to 1, and the transmittance of the latter is less than 0.8, or even 0. In this example, the transmittance of the latter is 0. These two grids are randomly distributed. In order to prevent the grid corresponding to a certain part of the beam from being 0 or 1, we use the templates of two adjacent outgoing beams as complementary, that is, the transmittance of a template is 0 The grid in another template corresponds to a grid with a light transmittance of 1. A typical template and its complementary template are shown in Figure 5. For the imaging device shown in FIG. 4 , the number of outgoing beams is 5, we set the templates 61 , 62 and 64 , 65 as complementary templates, and design all the grids of the template 63 to have a light transmittance of 1.

The other parts of the device are described in detail below according to the propagating direction of the incident light beam. The device includes a shutter 1, and when the shutter 1 is pressed, all receiving devices CMOS industrial cameras 81-85 take pictures simultaneously. The exposure time of the industrial camera 81-85 is adjustable, the minimum is 0.005 seconds.

The spectroscopic device of the device is composed of a prism group composed of 4 spectroscopic prisms. These spectroscopic prisms can divide the incident light into two beams of light with the same light intensity, that is, transmitted light and reflected light. They are fixed by corresponding fixtures 10 . The incident light beam is firstly split at the dichroic prism 2. As shown in Figure 4, the reflected light propagates upwards through the prism 2, and is divided into two beams of light again through the prism 3, wherein one beam is reflected by the prism 3 and propagates horizontally to the right, and reaches the industrial camera 83 through the template 63; The transmission continues to propagate upwards, and is divided into two beams of light by the prism 5 again, and the two beams of light both pass through their corresponding templates 61, 62 and reach the corresponding receiving devices CMOS industrial cameras 81, 82. Another beam of light is transmitted through the prism 2, which is divided into two beams of light again by the prism 4, and then the two beams of light pass through the corresponding 64, 65 and also reach the corresponding CMOS industrial cameras 84, 85. Note that the two outgoing beams obtained by the prism 5 are equivalent to the product of three times of light splitting, while the other outgoing beams are equivalent to the product of two times of light splitting, so if there is no influence of the template, the light corresponding to the industrial cameras 81 and 82 The intensity is 1/2 of the light intensity received by the industrial cameras 83, 84, and 85. In order to eliminate this effect, we install light attenuation devices in front of the templates 63, 64, and 65 (as shown in Figure 4). slit, and then insert the attenuation sheet 7 into the slit. By adjusting the attenuation sheet 7, the overall light intensity passing through it is reduced to 1/2 of the original.

In specific applications, for the convenience of use, the internal components of the device are placed and fixed in the shell 9 . All the CMOS industrial cameras 81-85 have the same optical path difference to the central position of the beam splitter 2 (that is, where the incident light is split), and their distances to the corresponding spatial light modulators are also the same. In this example, the distance from prism 2 to prism 3 is 25 millimeters, the distance to prism 4 is 50 millimeters, the distance from prism 3 to prism 5 is 25 millimeters, the distance from prism 3 to industrial camera 83 is 50 millimeters, prism 4, The distance from 5 to its corresponding industrial cameras 84, 85 and 81, 82 is also 50 millimeters, the distance from the template to the photosensitive surface of the corresponding industrial camera 8 is 20 millimeters, and the side length of each grid in the template is 0.025 millimeters.

The simulated sample is used to show its application, and the sub-figures a and c in Fig. 6 are the amplitude and phase distributions respectively. The sample is in the shape of a square, with a set side length of 3 millimeters and opaque surroundings. The parallel laser beam with a wavelength of 532 nanometers passes through the sample and then enters the stacked diffraction device. The light beam is adjusted so that it is vertically incident on the center of the splitter prism 2, so that all industrial cameras 81-85 can receive images of the sample in their central areas. When the shutter is opened, these cameras take images of the sample at the same time, and these images are all modulated by the template.

The CMOS industrial camera transmits the received pattern to the computer for processing through a wired or wireless connection device (not shown in the figure), and obtains its phase and intensity distribution according to the traditional stacked diffraction iterative algorithm without separating the spot. Figure 6b and d subgraphs show the intensity and phase distributions obtained by the stacked diffraction algorithm, respectively, which are very consistent with the original sample. The recovery calculation time is 4 seconds. It can be seen that the device can perform fast lamination diffraction imaging of objects.

Claims (8)

1. A stacked diffraction imaging device, comprising successively according to the direction of incident light beam propagation: (1) A spectroscopic device that divides the incident beam into several outgoing beams; (2) A beam adjustment device corresponding to each outgoing beam, which can adjust the beam amplitude or phase distribution, or adjust both distributions at the same time; (3) The image receiving device corresponding to each outgoing beam. 2. The lamination diffraction imaging device as claimed in claim 1, characterized in that the spectroscopic device is composed of a prism group including several spectroscopic prisms. 3. The stacked diffractive imaging device as claimed in claim 1, wherein the light beam adjustment device is a spatial light modulator. 4. The stacked diffraction imaging device as claimed in claim 1, characterized in that the light beam adjustment device is an amplitude-type lattice template. 5. The stacked diffractive imaging device as claimed in claim 1, wherein the optical path difference between each image receiving device and the first branch of the incident light beam is the same. 6. The laminated diffractive imaging device as claimed in claim 1, characterized in that a light attenuating device is placed in front of part or all of the image receiving device. 7. The lamination diffraction imaging device as claimed in claim 1, characterized in that there is a shutter device in front of the spectroscopic device, and after opening, each receiving device receives the pattern simultaneously. 8. The laminated diffractive imaging device as claimed in claim 6, characterized in that the light attenuating device in the device is a light attenuating sheet.