Compound eye grating diffraction experimental device and experimental method

Abstract

An experimental device and method for fly-eye grating diffraction. The experimental device comprises a first laser, a second laser, a beam splitter lens, a fly-eye grating and its fixing mechanism, a Fourier transform lens, a receiving screen, a light attenuation sheet and a reflecting lens. The light emitted by the first laser passes through the beam splitter lens, the fly-eye grating and the Fourier transform lens in sequence and reaches the receiving screen. The light emitted by the second laser passes through the attenuation sheet, the reflecting lens, the beam splitter lens, the fly-eye grating and the Fourier transform lens in sequence and reaches the receiving screen. The experimental method comprises the following steps: fly-eye grating manufacturing, light path building and calibration, single-layer fly-eye grating diffraction pattern observation and data processing, and rotation regulation of the moire produced by double-layer fly-eye gratings. The application fills the gap of the plane grating diffraction exploration experiment in the university physics experiment, and solves the problem that the optical diffraction experiment content is single and it is difficult to stimulate students' interest in grating diffraction exploration experiment.

Description

TECHNICAL FIELD

[0001] The application relates to a grating diffraction experiment device and an experiment method. BACKGROUND

[0002] Optical diffraction experiment is one of the classic experiments in university physics experiment, and common ones are single-slit diffraction experiment, circular aperture diffraction experiment, Young's double-slit interference experiment and grating diffraction experiment.

[0003] However, the existing experimental devices are only limited to measuring fringe data and error analysis, and lack of functions in the aspects of overall experimental device construction, complex diffraction principle exploration and data processing. For example, the grating diffraction experiment often uses a one-dimensional grating as a diffraction device, and the fringe spacing and grating constant are easy to measure, and the overall experimental operation is simple, but it is difficult to stimulate the learning enthusiasm of students, and the abstract diffraction principle and concept lack in-depth exploration.

[0004] In 2008, Li Guijun et al. published “Dragonfly Eye Grating” (“Dragonfly Eye Grating”, Li Guijun, Lv Mengjiao, Liang Haidong et al. Physics Experiment, 2008 (5), pp. 44-46) disclosed a method for making a dragonfly eye grating using a 5% concentration of NaOH solution and a pig pen, which verified the periodic hexagonal structure of the plane grating from the aspects of experiment and simulation, but the simplicity and safety of the grating making method still need to be improved, and the description of the experimental device is not clear, and the wavelength of the laser and the type of the specimen are single.

[0005] In 2010, Huang Gaokun published “Theoretical and Experimental Research on Two-Dimensional Grid Talbot Effect” (Huang Gaokun. Theoretical and Experimental Research on Two-Dimensional Grid Talbot Effect [D]. Southwest University, 2019. Dissertation, which can be searched on China National Knowledge Network) gave a method for generating Moire fringes using two-dimensional plane gratings and a calculation formula for grating constant from theory and experiment, but it is limited to square configuration, and the Moire fringe pattern of regular hexagonal structure grating is not described, which still has room for further research.

[0006] CN 202010748978.1 discloses a diffraction experiment device and an experiment method thereof, which comprises a fixed track and a movable track connected by a folding type, and a light source assembly, a baffle assembly and a light screen assembly are sequentially arranged on the fixed track and the movable track and are in sliding fit with the track, the diffraction device and the experimental content are single, and it is difficult to deepen the understanding of students on the optical diffraction phenomenon, and there is still room for improvement in the structure of the optical diffraction experiment instrument and the selection of the grating.

[0007] Invention content:

[0008] The technical problem to be solved by the present application is to overcome the single function of the existing optical diffraction experiment instrument, and to provide a compound eye grating diffraction experiment device and an experiment method.

[0009] The technical solution adopted by the present application to solve the technical problem is a compound eye grating diffraction experiment device, which comprises a first laser, a second laser, a beam splitter lens, a fly compound eye grating and a fixing mechanism thereof, a Fourier transform lens, a receiving screen, an optical attenuation sheet, a reflecting lens, and a plurality of optical supports for fixing the device, a mirror frame and an aperture stop for calibrating the optical path; the light emitted by the first laser passes through the beam splitter lens, the fly compound eye grating and the Fourier transform lens in sequence to reach the receiving screen, which is referred to as optical path a; the light emitted by the second laser passes through the attenuation sheet, the reflecting lens, the beam splitter lens, the fly compound eye grating and the Fourier transform lens in sequence to reach the receiving screen, which is referred to as optical path b; the first laser is fixed and immovable, the beam splitter lens is placed in front of the first laser at an angle of 45°, the fly compound eye grating and the fixing mechanism thereof are located in front of the beam splitter lens and near the object plane focal plane of the Fourier transform lens, the Fourier transform lens is located in front of the fly compound eye grating and the fixing mechanism thereof and has a linear distance close to its own focal length, the receiving screen is located near the image plane focal plane of the Fourier transform lens, and the first laser, the beam splitter lens, the fly compound eye grating, the Fourier transform lens and the receiving screen are located on the same optical path a; the reflecting lens is located on the right side of the beam splitter lens and is placed at an angle of 45°, the attenuation sheet is located behind the reflecting lens, the second laser is located behind the attenuation sheet, and the beam splitter lens, the receiving screen, the attenuation sheet and the reflecting lens are located on the same optical path b.

[0010] Further, the wavelengths of the first laser and the second laser are within the visible light 400-700nm band (the light is visible to the naked eye), the beam splitter lens is a 1:1 beam splitter lens, the fly is a fly of the Muscidae family with a compound eye structure, such as Chrysomya megacephala, Musca domestica or Calliphora erythrocephala, and the focal length of the Fourier transform lens can be 150mm and 200mm, or other focal lengths.

[0011] Further, the compound eye grating is made of the compound eyes of Chrysomya megacephala, Musca domestica and Calliphora erythrocephala, which is simple to operate, can make the Gaussian beam of the laser pass through and produce obvious diffraction phenomenon.

[0012] Further, the power of the first laser is ≤500mW, and the power of the second laser is ≤35mW, so as not to damage the internal structure of the grating.

[0013] Further, the Gaussian beams generated by the first laser and the second laser have an intensity of 10-20 mW when passing through the compound eye grating.

[0014] During the experiment, the power can be reduced to 10-20 mW by using an attenuating sheet or adjusting the power supply voltage, so that the formed image is clear and the compound eye grating structure is not damaged, and the damage to the human eye is small.

[0015] Further, the compound eye grating is composed of a fly compound eye specimen and two clamping glass sheets, the distance between the two fly compound eye gratings is less than or equal to 5 mm, and the fly compound eye gratings are sequentially placed near the object focal plane of the Fourier transform lens and fixed on the light path of the light beam after the beam splitting lens.

[0016] Further, the glass sheet clamping the fly compound eye specimen is a glass sheet that does not have a dispersion effect on the Gaussian beam and does not have an additional influence on the diffraction effect.

[0017] Further, the positions of the beam splitting lens and the reflecting lens can be finely adjusted by an optical frame to ensure the collimation of the light path.

[0018] Further, the straight-line distance between the Fourier transform lens and the receiving screen is a distance for making the imaging pattern clear and sharp.

[0019] The method for performing a compound eye grating diffraction experiment by using the compound eye grating diffraction experiment device has the following operation steps:

[0020] (1) using a scalpel to tear off the frozen fly compound eye, rinsing with distilled water, and making a fly compound eye grating after removing the muscle tissue;

[0021] (2) turn on the first laser, first use two aperture diaphragms to complete the calibration of the light path a, then turn off the first laser, turn on the second laser, adjust the beam splitting lens and the reflecting lens, and complete the calibration of the light path b;

[0022] (3) adjust the positions of the Fourier transform lens and the receiving screen until a clear dot array diffraction pattern appears on the receiving screen;

[0023] (4) measure the average distance of the bright spots in the dot array pattern, and calculate the grating constant of the compound eye grating combined with the focal length of the Fourier transform lens; the calculation formula is as follows:

[0024] d= λf

[0025] Δx

[0026] In the formula, d is a grating constant, λ is a laser wavelength, f is a Fourier transform lens focal length, and Δx is an average interval between adjacent bright spots in a dot array pattern.

[0027] The calculation result is compared with the data obtained under a microscope.

[0028] (5) Two fly compound eye gratings are placed at a distance of ≤5 mm behind a beam splitter lens and in the vicinity of an object plane of a Fourier transform lens, and one of the fly compound eye gratings is rotated, and a period change of light intensity distribution of a Moire pattern on a receiving screen is observed.

[0029] Further, different dot array diffraction patterns and Moire patterns are obtained by using the first laser and the second laser respectively.

[0030] The present application fills the gap of the plane grating diffraction exploration experiment in the university physics experiment, solves the problem that the optical diffraction experiment content is single and it is difficult to stimulate the students' interest in grating diffraction exploration experiment, and has important significance for cultivating students' related practical ability and innovative spirit. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 It is a structure schematic view of the compound eye grating diffraction experiment device embodiment of the present application (not including a mirror frame, a support, an optical platform and the like fixing device or adjusting device).

[0032] Figure 2 It is a dot array diffraction pattern in the compound eye grating diffraction experiment method embodiment of the present application; wherein, Fig. a is a reference diagram, Fig. b is a dot array diffraction pattern after changing a wavelength, Fig. c is a dot array diffraction pattern after changing a Fourier lens focal length, and Fig. d is a dot array diffraction pattern after changing a compound eye specimen, that is, different dot array intervals.

[0033] Figure 3 It is data obtained under a microscope in the compound eye grating diffraction experiment method embodiment of the present application (grating constants of the three are different).

[0034] Figure 4 It is a Moire pattern change when the relative twist angle of the double-layer compound eye grating is changed in the compound eye grating diffraction experiment method embodiment of the present application. DETAILED DESCRIPTION

[0035] The present application is further described in detail below in combination with the drawings and embodiments.

[0036] REFERENCE Figure 1The fly (Musca vittata, Musca domestica or Calliphora erythrocephala) compound eye grating and its fixing mechanism 4, the Fourier transform lens 5, the receiving screen 6, the light attenuation sheet 7 and the reflecting lens 8 are located on the same light path b.

[0037] The specific operation method of the fly (Musca vittata, Musca domestica or Calliphora erythrocephala) compound eye grating diffraction experiment method embodiment of the application includes the following steps:

[0038] (1) Take out the flies (Musca vittata, Musca domestica and Calliphora erythrocephala) compound eyes which have been refrigerated in a refrigerator at 4-10 DEG C for more than 3 days, use a scalpel to cut off the compound eyes, rinse with distilled water, remove the muscle tissue and then make the fly compound eye grating 4;

[0039] The specific operation steps are as follows: first, rinse the surface of the Musca vittata, Musca domestica and Calliphora erythrocephala compound eyes with distilled water, then dry them, put them in a refrigerator and refrigerate for more than 3 days, take them out after the water in the fly body is lost, fix them on the experimental table, use a scalpel to gently draw along the outline of the compound eye, then use a pair of tweezers to hold one corner of the scratch and slowly tear it off, and clean the more obvious muscle tissue inside, then rinse with distilled water several times, place them on a glass slide, drop a little distilled water on the surface, cover another glass slide, dry the surface of the slide and seal the gap;

[0040] (2) After the instrument is built, turn on the first laser 1, first use two aperture diaphragms to complete the calibration of the light path a, then turn off the first laser 1, turn on the second laser 2, adjust the beam splitter 3 and the reflecting lens 8, and complete the calibration of the light path b;

[0041] The specific steps for optical path calibration are as follows: First, calibrate the straight optical path a. Keep the first laser 1 with a wavelength of 405nm fixed and adjust the 1:1 beam splitter lens 3, the two aperture stops, and the receiving screen 6 to be coaxial with the light source. Then, calibrate the optical path b. Keep the second laser 2 with a wavelength of 633nm fixed and adjust the reflective lens 8 to be at the same height as other components. Use the "half-adjustment method" to alternately adjust the reflective lens 8 and the beam splitter lens 3. When the optical path between the beam splitter lens 3 and the receiving screen 6 overlaps with the 405nm wavelength optical path, the calibration is complete.

[0042] (3) Adjust the position of the Fourier transform lens 5 and the receiving screen 6 until a clear dot matrix diffraction pattern appears on the receiving screen 6.

[0043] Different laser wavelengths, different Fourier transform lens focal lengths, and different compound eye specimens produce different lattice diffraction patterns (see [reference]). Figure 2 Figure a is a dot matrix pattern obtained using a compound eye grating of a big-headed golden fly, a 633nm wavelength laser, and a 150mm focal length Fourier transform lens. Figure a is used as a reference dot matrix pattern. Figure b is a dot matrix pattern with the laser wavelength changed to 405nm. Figure c is a dot matrix pattern with the focal length of the Fourier transform lens changed to 20cm. Figure d is a dot matrix pattern with the fly species changed to housefly.

[0044] (4) Measure the average spacing Δx of the bright spots in the dot matrix pattern, and calculate the grating constant d of the compound eye grating by combining the focal length f of the Fourier transform lens and the laser wavelength λ; the calculation formula is as follows:

[0045] d = λf

[0046] Δx

[0047] In the formula, d is the grating constant, λ is the laser wavelength, f is the focal length of the Fourier transform lens, and Δx is the dot matrix.

[0048] Compare the calculation results with the data obtained under a microscope (see...) Figure 3 ) for comparison;

[0049] (5) Place two fly compound eye gratings at a spacing of less than 5 mm near the object-side focal plane of the Fourier transform lens, behind the beam-splitting lens, and rotate one of the gratings to observe the changes in light intensity distribution of the moiré pattern on the receiving screen (see...). Figure 4 ).

[0050] Experimental phenomena: By adjusting the distance between the Fourier transform lens 5 and the fly compound eye grating 4 and the receiving screen 6, so that the receiving screen 6 is exactly near the image-side focal plane of the Fourier transform lens 5, spectral data reception can be achieved; after turning on the 633nm second laser 2 and fine-tuning, a clear dot matrix diffraction pattern can be seen (see...).Figure 2 a), the average distance between the bright spots was calculated by marking the bright spots on the coordinate paper; after replacing the first laser 1 with 405 nm, the diffraction pattern of the dot array was still observed (see Figure 2 b), but the distance between the dots became smaller, verifying the effect of wavelength on diffraction; after replacing the Fourier transform lens with different focal lengths, the diffraction pattern of the dot array was still observed (see Figure 2 c), but the distance became larger; after replacing the compound eye specimens of Chrysomyia megacephala, Musca domestica and Calliphora erythrocephala, the diffraction pattern of the dot array was still observed, but the distance between the dots was different (see Figure 2 d), verifying the effect of grating constant on diffraction; the average distance between the bright spots was calculated by marking the bright spots on the coordinate paper, and then the grating constant of the compound eye was calculated by combining the focal length of the Fourier transform lens 5, the experimental value was basically the same as the theoretical value within the allowable error range.

[0051] Referring to Figure 2 a, taking the combination of the compound eye grating of Chrysomyia megacephala, the first laser with a wavelength of 633 nm and the Fourier transform lens with a focal length of 150 mm as an example, Δx was 1.44 mm after 24 repeated measurements, and d was 65.9 μm after being brought into the grating constant calculation formula, and the relative error with the value of 66.0 μm observed under the microscope (see Figure 3 ) was 0.2%, Figure 2 the relative error of b was 3.5%, Figure 2 the relative error of c was 2.4%, Figure 2 and the relative error of d was 1.9%. This shows that the experimental data is basically the same as the theoretical calculation value.

[0052] Moire control: under the condition of fixing one fly compound eye grating, slowly rotating the other compound eye grating, the diffraction pattern moves obviously when the rotation angle is small (see Figure 4 , where a is the reference diffraction pattern, b is the bright spot distance of the image rotated by about 0.5°, c is the bright spot distance of the image rotated by about 2°, and the overall still presents a hexagonal distribution.

Claims

1. A compound eye grating diffraction experimental apparatus, characterized in that, The system includes a first laser, a second laser, a beam-splitting lens, a fly-eye grating and its fixing mechanism, a Fourier transform lens, a receiving screen, an optical attenuator, a reflecting lens, and several optical supports, frames, and aperture stops for calibrating the optical path for fixing the components. The light emitted from the first laser passes sequentially through the beam-splitting lens, the fly-eye grating, and the Fourier transform lens to reach the receiving screen; this is called optical path a. The light emitted from the second laser passes sequentially through the attenuator, the reflecting lens, the beam-splitting lens, the fly-eye grating, and the Fourier transform lens to reach the receiving screen; this is called optical path b. The first laser is fixed in place, and the beam-splitting lens is positioned in front of the first laser at a 45° angle. The fly compound eye grating and its fixing mechanism are located in front of the beam splitter lens and near the object-side focal plane of the Fourier transform lens. The Fourier transform lens is located in front of the fly compound eye grating and its fixing mechanism, and the straight-line distance is close to its own focal length. The receiving screen is located near the image-side focal plane of the Fourier transform lens. The first laser, the beam splitter lens, the fly compound eye grating, the Fourier transform lens, and the receiving screen are located on the same optical path a. The reflecting lens is located to the right of the beam splitter lens and is placed at a 45° angle. The attenuator is located behind the reflecting lens. The second laser is located behind the attenuator. The beam splitter lens, the receiving screen, the attenuator, and the reflecting lens are located on the same optical path b.

2. The compound eye grating diffraction experimental apparatus according to claim 1, characterized in that, The wavelengths of the first and second lasers are in the visible light band of 400-700nm, the beam splitter lens is a 1:1 beam splitter lens, the fly is a golden fly, a house fly, or a small white fly, and the focal lengths of the Fourier transform lens are 150mm and 200mm.

3. A compound eye grating diffraction experimental apparatus according to claim 1 or 2, characterized in that, The fly compound eye grating is made from the compound eyes of golden flies, houseflies, and small beech flies.

4. A compound eye grating diffraction experimental apparatus according to claim 1 or 2, characterized in that, The power of the first laser is ≤500mW and the power of the second laser is ≤35mW, so as not to damage the internal structure of the grating.

5. A compound eye grating diffraction experimental apparatus according to claim 1 or 2, characterized in that, The Gaussian beams generated by the first and second lasers have an intensity of 10-20 mW when passing through the compound eye grating.

6. A compound eye grating diffraction experimental apparatus according to claim 1 or 2, characterized in that, The fly compound eye grating consists of a fly compound eye specimen and two clamping glass slides; the glass slides are those that do not produce a dispersion effect on the Gaussian beam and do not have an additional effect on the diffraction effect.

7. A compound eye grating diffraction experimental apparatus according to claim 1 or 2, characterized in that, The distance between the two fly compound eye gratings is ≤5mm. They are placed near the object-side focal plane of the Fourier transform lens and fixed on the light path behind the beam splitter lens.

8. A compound eye grating diffraction experimental apparatus according to claim 1 or 2, characterized in that, The positions of the beam-splitting lens and the reflecting lens are finely adjusted using an optical frame to ensure optical path collimation.

9. A method for performing compound eye grating diffraction experiments using the compound eye grating diffraction experimental apparatus according to any one of claims 1-8, characterized in that, The fly compound eye specimen has a single hexagonal array structure with a spatially periodic refractive index distribution and minimal residual muscle tissue. It allows Gaussian light to pass through, thus functioning as a dispersive grating. The experimental method includes the following steps: (1) Use a scalpel to tear off the refrigerated fly compound eyes, rinse with distilled water, remove muscle tissue and then make fly compound eye gratings; (2) Turn on the first laser, first use two aperture stops to complete the calibration of optical path a, then turn off the first laser, turn on the second laser, adjust the beam splitter lens and the reflection lens to complete the calibration of optical path b; (3) Adjust the position of the Fourier transform lens and the receiving screen until a clear dot matrix diffraction pattern appears on the receiving screen; (4) Measure the average spacing between the bright spots in the dot matrix pattern, and calculate the grating constant of the compound eye grating by combining the focal length of the Fourier transform lens; the calculation formula is as follows: ， In the formula, The grating constant is The wavelength of the laser. The focal length of the Fourier transform lens. This represents the average spacing between adjacent dots in the dot matrix pattern. The calculation results were compared with data obtained under a microscope; (5) Place two fly compound eye gratings with a spacing of ≤5mm behind the beam splitter lens and near the object-side focal plane of the Fourier transform lens. Rotate one of the fly compound eye gratings and observe the periodic changes in the light intensity distribution of the moiré pattern on the receiving screen.

10. The experimental method according to claim 9, characterized in that, Different dot matrix diffraction patterns and moiré patterns were obtained by using a first laser and a second laser respectively.

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