Super-resolution digital holographic imaging system based on multiple gratings

Abstract

The utility model discloses a multi-grating-based super-resolution digital holographic imaging system, which is characterized in that a window integrated by a plurality of gratings is added in an object light path of a traditional Mach-Zehnder holographic light path, and light with different inclination angles is generated by moving the window to irradiate a sample to be measured and interfere with reference light, so as to realize the imaging of the multi-grating-based super-resolution digital holographic imaging system. Therefore, a plurality of digital holograms are acquired at the image sensor. Object light with different inclination angles is realized by adopting a multi-grating diffraction mode, the system is low in cost, convenient and stable, has no fixed requirements on parameters of core devices in the system, such as a microscope objective and an image sensor, can be flexibly applied to the existing system according to the imaging method to realize super-resolution imaging, and has very high commercial value.

Description

Technical Field

[0001] The utility model relates to the field of digital holographic imaging, in particular to a super-resolution digital holographic imaging system based on multiple gratings. Background Art

[0002] With the rapid development of biomedicine, materials science and other related fields, the resolution requirements for microscopic imaging systems are getting higher and higher. However, due to the diffraction effect of light, the resolution of conventional optical microscopic imaging systems is diffraction-limited. Super-resolution imaging, which increases the resolution beyond the optical diffraction limit, has long attracted attention.

[0003] Digital holographic imaging is to record the digital hologram between the object light and the reference light that carry the information of the sample to be tested, and reconstruct it through an algorithm to obtain the entire wavefront information of the light passing through the sample to be tested, thereby achieving quantitative phase imaging. At the same time, the tilt angle of the object light can be changed to collect multiple digital holograms, and the frequency domain of a single image can be expanded by synthesizing the spectrum of multiple digital holograms to achieve super-resolution imaging. Compared with traditional microscopic imaging, digital holographic imaging does not require staining and can be measured non-destructively for a long time, which has great advantages in the field of biological research.

[0004] At present, there are two main ways to adjust the tilt angle of the object light: one is to use mechanical methods to adjust, such as galvanometers, which have high precision and can achieve continuous angle change, but galvanometers are expensive, and because galvanometers adjust the angles of two dimensions by controlling two reflectors respectively, some angles cannot be adjusted [Youhua Chen et al. Widefield and total internal reflection fluorescent structured illumination microscopy with scanning galvo mirrors. [J]. Journal of biomedical optics, 2018, 23 (4): 1-9.]; the other is to use spatial light modulators for adjustment, such as liquid crystal spatial light modulators, which change the angle by regulating multiple liquid crystals through electric fields. The operation is complicated and expensive, or a digital micro-reflection device is used, but the device is not perpendicular to the optical axis of the system, and an additional lens is required to correct it, and the adjustment angle range is limited [Wenjing Zhou, Qiangsheng Xu, Yingjie Yu, Anand Asundi, Phase-shifting in-line digital holography on a digital micro-mirror device, Optics and Lasers in Engineering, Volume 47,Issue 9,2009].

[0005] Based on the above background, it is of great engineering significance to design a stable and easy-to-promote optical system that uses mechanically movable multi-grating windows to form a fixed angle to achieve super-resolution imaging. Utility Model Content

[0006] In order to solve the problems in the prior art, the utility model provides a super-resolution digital holographic imaging system based on multi-gratings. In the utility model, the angle required by the system is limited and fixed, and no dynamic adjustment function is required.

[0007] In order to achieve one of the purposes of the utility model, the utility model provides a super-resolution digital holographic imaging system based on a multi-grating, which includes a laser for emitting light, a first lens, a second lens, a pinhole for filtering, and a first non-polarizing beam splitter prism. The light emitted by the laser is focused by the first lens and sequentially passes through the pinhole and the second lens to enter the first non-polarizing beam splitter prism. A multi-grating window and a fifth lens are arranged behind the first non-polarizing beam splitter prism.

[0008] The multi-grating window includes a rectangular hole window and a plurality of grating windows arranged in sequence transversely. The multi-grating window is moved and switched to different windows by a stepping motor. A third lens, an aperture, a fourth lens, a sample area for placing a sample to be tested, an objective lens, a first reflector, an imaging lens, a second non-polarizing beam splitter prism and an image sensor are sequentially arranged behind the multi-grating window.

[0009] A second reflector, a sixth lens, a second non-polarizing beam splitter prism and the image sensor are sequentially arranged behind the fifth lens;

[0010] The multi-grating window is arranged on the object focal plane of the third lens, and the aperture is arranged on the image focal plane of the third lens and the object focal plane of the fourth lens.

[0011] Preferably, the multi-grating window includes a rectangular hole window and a plurality of grating windows arranged in sequence transversely.

[0012] Preferably, the gratings in the multi-grating window include sinusoidal phase gratings.

[0013] Preferably, the multi-grating window is moved by a stepping motor and different windows are switched so as to be located in the light path.

[0014] Preferably, the aperture is provided with small holes, the positions of which correspond to the focusing points of the transmitted light or +1-order diffracted light generated by different windows in the multi-grating window passing through the third lens at the aperture.

[0015] Preferably, a movable light shield is attached in front of each small hole in the diaphragm, and is adjusted according to the window in the light path of the multi-grating window.

[0016] Preferably, the sample area to be tested is arranged on the image-side focal plane of the fourth lens and the object-side focal plane of the objective lens.

[0017] Preferably, the image sensor is placed on the image-side focal plane of the imaging lens.

[0018] The beneficial effects of the utility model are as follows:

[0019] The utility model integrates multiple gratings laterally on a window, which is moved by a stepper motor to obtain object light with different tilt angles. The device is simple, stable and low-cost. The utility model has no fixed requirements on the parameters of core components in the system, such as microscope objective lenses and image sensors. The existing system can be flexibly used according to different components, and has strong commercial value. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of a super-resolution digital holographic imaging system based on multiple grating windows.

[0021] Figure 2 Schematic diagram of the structure of the multi-grating window in Example 1.

[0022] Figure 3 It is a schematic diagram of the structure of the aperture in Example 1.

[0023] Figure numerals: 1. laser, 2. first lens, 3. pinhole, 4. second lens, 5. first non-polarizing prism, 6. multi-grating window, 7. third lens, 8. aperture, 9. fourth lens, 10. sample area to be measured, 11. objective lens, 12. first reflector, 13. imaging lens, 14. fifth lens, 15. second reflector, 16. sixth lens, 17. second non-polarizing beam splitter prism, 18. image sensor. DETAILED DESCRIPTION

[0024] A typical embodiment of a super-resolution digital holographic imaging system based on multi-gratings of the present invention is described in detail below in conjunction with the accompanying drawings. It should be noted that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] Example 1

[0026] The utility model is a super-resolution digital holographic imaging system based on multi-grating, such as Figure 1 As shown, the light emitted by the laser 1 is focused by the first lens 2, filtered by the pinhole 3, collimated into parallel light by the second lens 4, and divided into two beams of light with the same energy by the first non-polarizing beam splitter prism 5.

[0027] A beam of light is incident on different windows in the multi-grating window 6, and is transmitted or diffracted. After being focused by the third lens 7, it enters the aperture 8. Only light at a specific angle can pass through the aperture 8, and the rest of the light is blocked. The light passing through the aperture 8 is collimated by the fourth lens 9 as parallel light and incident on the sample area 10 to be tested. After passing through the sample, the light beam carries the information of the sample to be tested, passes through the objective lens 11, is reflected by the first reflector 12 to the imaging lens 13, and then passes through the second non-polarizing beam splitter prism 17 to reach the image sensor 18 as the object light; another beam of light passes through the fifth lens 14, is reflected by the second reflector 15, passes through the sixth lens 16 to form a parallel beam, passes through the second non-polarizing beam splitter prism 17, and reaches the image sensor 18 as the reference light. The reference light and the object light interfere to generate interference fringes containing the information of the sample to be tested 10, which are received by the image sensor 18.

[0028] The multi-grating window 6 is moved by a stepping motor to switch different windows, generating light beams of different angles to enter the sample area 10 to be tested, and 6 digital holograms are collected on the image sensor 18.

[0029] Multi-grating window 6 Figure 2As shown, it consists of a rectangular hole and five sinusoidal phase gratings, which are numbered A0, A1, A2, A3, A4, and A5 for distinction. The diffraction angles corresponding to different diffraction orders satisfy:

[0030] Dsinα=kλ

[0031] Wherein, D is the period of the sinusoidal phase grating, k is the diffraction order, α is the diffraction angle corresponding to the k-order diffracted light, and λ is the wavelength of the laser beam.

[0032] In this embodiment, 6 small holes are opened on the aperture 8, and the structure is as follows: Figure 3 As shown. Among them, the small holes p0, p1, p2, p3, p4, p5 correspond to the windows A0, A1, A2, A3, A4, A5 in the multi-grating window 6 respectively. A movable shading plate is attached in front of each hole. The shading plate of the corresponding small hole is opened according to the window located in the light path of the multi-grating window 6, and the shading plates of the remaining small holes are closed.

[0033] In this embodiment, the laser 1 is a solid laser with a wavelength of 632.8 nm (including but not limited to solid lasers, and can be gas lasers, semiconductor lasers, etc., and the wavelength is not limited to 632.8 nm); the objective lens 11 has a magnification of 40 times and a numerical aperture of 0.65 (this embodiment adopts a magnification of 40 times and a numerical aperture of 0.65, but is not limited to a magnification of 40 times and a numerical aperture of 0.65); the image sensor 18 is a CCD (this embodiment adopts CCD, but is not limited to CCD), and the pixel size is 4.3 μm (this experiment adopts 4.3 μm, but is not limited to 4.3 μm).

[0034] Although the present invention is described in detail with reference to specific examples, the examples of the present invention described herein are not intended to be exhaustive or limited to the specific forms disclosed. Instead, the embodiments selected for illustrating the problem are selected to enable those skilled in the art to implement the present invention. There are variations and modifications without departing from the essential scope of the present invention as described and defined in the following claims.

Claims

1. A super-resolution digital holographic imaging system based on multi-gratings, characterized in that: The invention comprises a laser (1) for emitting light, a first lens (2), a second lens (4), a pinhole (3) for filtering and a first non-polarizing beam splitter prism (5); the light emitted by the laser is focused by the first lens (2) and then passes through the pinhole (3) and the second lens (4) in sequence to enter the first non-polarizing beam splitter prism (5); a multi-grating window (6) and a fifth lens (14) are arranged behind the first non-polarizing beam splitter prism (5); The multi-grating window (6) comprises a rectangular hole window and a plurality of grating windows arranged in sequence transversely. The multi-grating window (6) is moved by a stepping motor and different windows are switched. A third lens (7), an aperture (8), a fourth lens (9), a sample area (10) for placing a sample to be tested, an objective lens (11), a first reflector (12), an imaging lens (13), a second non-polarizing beam splitting prism (17) and an image sensor (18) are sequentially arranged behind the multi-grating window (6); A second reflector (15), a sixth lens (16), a second non-polarizing beam splitter prism (17) and the image sensor (18) are sequentially arranged behind the fifth lens (14); The multi-grating window (6) is arranged on the object focal plane of the third lens (7), and the diaphragm (8) is arranged on the image focal plane of the third lens (7) and the object focal plane of the fourth lens (9).

2. The multi-grating based super-resolution digital holographic imaging system according to claim 1, characterized in that: The multi-grating window (6) comprises a rectangular hole window and a plurality of grating windows which are arranged in sequence transversely.

3. The multi-grating based super-resolution digital holographic imaging system according to claim 1, characterized in that: The gratings in the multi-grating window (6) include sinusoidal phase gratings.

4. The multi-grating based super-resolution digital holographic imaging system according to claim 1, characterized in that: The multi-grating window (6) is moved by a stepping motor and different windows are switched so as to be located in the optical path.

5. The multi-grating based super-resolution digital holographic imaging system according to claim 1, characterized in that: The aperture (8) is provided with a small hole, the position of which corresponds to the focus of the transmitted light or +1st order diffracted light generated by different windows in the multi-grating window (6) passing through the third lens (7) at the aperture (8).

6. The multi-grating based super-resolution digital holographic imaging system according to claim 1, characterized in that: A movable light shielding plate is attached in front of each small hole in the diaphragm (8), and is adjusted according to the window in the light path of the multi-grating window (6).

7. The multi-grating based super-resolution digital holographic imaging system according to claim 1, characterized in that: The sample area (10) to be tested is arranged on the image-side focal plane of the fourth lens (9) and the object-side focal plane of the objective lens (11).

8. The multi-grating based super-resolution digital holographic imaging system according to claim 1, characterized in that: The image sensor (18) is placed on the image focal plane of the imaging lens (13).

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