A method for assembling and adjusting a holographic concave grating monochromator

Abstract

This invention relates to a method for assembling and adjusting a holographic concave grating monochromator, belonging to the field of optical instrument assembly and adjustment technology. It solves the problems of existing monochromator assembly and adjustment methods being cumbersome, time-consuming, labor-intensive, or having high theoretical requirements and low efficiency. The method involves leveling the holographic concave grating monochromator and laser; recording the initial spot height of the laser; directing the laser perpendicularly to the entrance slit of the monochromator to the center of the grating; measuring and recording the heights of the 0th and ±1st order diffraction spots; plotting the trajectories of the multi-order spectral spots; adjusting the pitch and / or tilt angle of the grating according to the trajectory until the center of each diffraction spot is collinear with the initial spot height; rotating the grating to allow the 0th order light to exit from the exit slit; using a right-angle fixture to adjust the grating shaft lever to be perpendicular to the drive screw and locking it; placing an external light source at the entrance slit; observing the clarity of the spectral lines at the exit slit using a microscope; and adjusting the thickness of the shim at the exit slit to achieve precise conjugate matching between the entrance and exit slits. This invention is simple to operate, quick to assemble and adjust, and highly accurate.

Description

Technical Field

[0001] This invention relates to the field of optical instrument assembly and adjustment technology, and in particular to an assembly and adjustment method for a holographic concave grating monochromator. Background Technology

[0002] With the development of aerospace and semiconductor processes, the demand for accurate measurement of photoelectron emission yield in materials places extremely high demands on the performance of analytical instruments. In photoelectron emission yield spectroscopy testing of materials, tunable ultraviolet monochromatic light (115-400nm band) is typically used to irradiate the material surface, exciting photoelectrons. A photon counter and microchannel plate are used to measure the voltage signal of the photoelectrons, followed by a photomultiplier tube to measure the photocurrent signal. Finally, the emission yield spectrum curve of the material is calculated. The ultraviolet monochromator, as the core component of the analytical instrument, can convert the polychromatic light from the light source into continuously tunable high-resolution monochromatic light. To ensure the accuracy of the monochromator's wavelength, it requires precise assembly and adjustment. However, since ultraviolet light is invisible in the atmosphere, this significantly increases the difficulty of assembling and adjusting the monochromator.

[0003] Because ultraviolet (UV) band coatings have low reflectivity, fewer optical components mean higher energy efficiency. Typically, UV monochromators employ a Seya-Namioka structure, using a type IV holographic concave grating to disperse and focus the incident light. To ensure wavelength accuracy, precise conjugation of the grating's entrance and exit slits, precise control of the grating's pitch angle, and the perpendicularity of the lead screw and grating axis lever are crucial. Existing monochromator setup and adjustment methods mainly fall into two categories: one uses reference cubic prisms for setup and adjustment, but requires individual calibration of each prism, making the operation cumbersome, time-consuming, and labor-intensive; the other uses computer-aided setup and adjustment, which requires operators to have comprehensive knowledge of aberration theory and algorithm design capabilities, making implementation difficult, time-consuming, and inefficient.

[0004] Therefore, designing a simple, fast, efficient, and reliable assembly and adjustment method is of great significance for the popularization and application of ultraviolet monochromators. Summary of the Invention

[0005] In view of the problems of the cumbersome and time-consuming operation of the reference cubic prism method and the high theoretical requirements and low efficiency of the computer-aided method in the existing technology, the present invention provides a simple, fast and precise method for assembling and adjusting a holographic concave grating monochromator.

[0006] To solve the above problems, the present invention adopts the following technical solution:

[0007] A method for assembling and adjusting a holographic concave grating monochromator includes the following steps:

[0008] Step 1: Place the holographic concave grating monochromator and the laser whose wavelength is within the working band of the holographic concave grating monochromator on the optical platform and level them;

[0009] Step 2: Record the initial spot height of the laser using a height gauge;

[0010] Step 3: The laser emitted by the laser is incident perpendicularly to the entrance slit of the holographic concave grating monochromator and directed to the center of the holographic concave grating. The heights of the 0th and ±1st order diffraction spots are measured and recorded at the exit slit of the holographic concave grating monochromator using a height ruler. The trajectories of the multi-order spectral spots are plotted. The pitch angle and / or tilt angle of the holographic concave grating are then adjusted according to the trajectories of the multi-order spectral spots until the centers of the 0th and ±1st order diffraction spots are collinear with the position where the initial spot height is located.

[0011] Step 4: Keeping the laser unchanged as described in Step 3, rotate the holographic concave grating through the drive mechanism to make the 0th order light exit from the slit. At this time, use a right-angle tool to adjust the perpendicularity of the grating axis swing rod to the drive screw in the drive mechanism. After the grating axis swing rod is perpendicular to the drive screw, lock and fix the grating axis swing rod.

[0012] Step 5: Place the external light source at the entrance slit, align the microscope vertically with the exit slit, rotate the holographic concave grating to make the characteristic spectral lines of the external light source emerge from the exit slit, observe the clarity of the characteristic spectral lines through the microscope, and adjust the thickness of the shim at the exit slit until the image of the characteristic spectral lines and the slit shim at the exit slit are both clear, thus completing the precise conjugate matching of the entrance and exit slits of the holographic concave grating.

[0013] To achieve precise assembly and adjustment of a holographic concave grating monochromator more simply and quickly, this invention proposes a rapid assembly and adjustment method based on a laser, microscope, and right-angle fixture. The method adjusts the grating's pitch and tilt angles by tracking the trajectory of the laser's multi-level spectrum; it achieves precise conjugate matching of the entry and exit slits by observing the clarity of the entry slit image at the exit slit using the microscope; and it uses the right-angle fixture to adjust the perpendicularity of the lead screw and the grating axis swing arm, ultimately completing the assembly and adjustment of the holographic concave grating monochromator. The beneficial effects of this invention include:

[0014] The assembly and adjustment method proposed in this invention is simple to operate and easy to understand, and requires low optical expertise from the operator. Even non-professionals can successfully carry out the assembly and adjustment.

[0015] This method can significantly shorten the assembly and adjustment time while ensuring high assembly accuracy;

[0016] By organically combining lasers, microscopes, and right-angle fixtures, rapid and precise assembly and adjustment of the pitch and tilt angles of holographic concave gratings, the perpendicularity of the lead screw and the grating axis swing arm, and the conjugate matching of the inlet and outlet of the slits are achieved. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the assembly and adjustment method of a holographic concave grating monochromator according to an embodiment of the present invention;

[0018] Figure 2 This is a schematic diagram illustrating the principle of adjusting the pitch and tilt angles of a holographic concave grating based on a laser.

[0019] Figure 3 A schematic diagram of the trajectory of a multi-level spectral spot;

[0020] Figure 4 This is a schematic diagram showing the position of the glue head on the grating box;

[0021] Figure 5 This is a schematic diagram of the perpendicularity adjustment between the lead screw and the grating axis lever based on a right-angle fixture;

[0022] Figure 6 This is a schematic diagram of precise conjugate matching of the grating entrance and exit slits based on a microscope.

[0023] Figure 7 This is a spectrum of characteristic wavelengths of a mercury lamp.

[0024] Explanation of reference numerals in the attached figures: 1. Holographic concave grating monochromator; 1-1. Entrance slit; 1-2. Exit slit; 1-3. Holographic concave grating; 1-3-1. Grating axis lever; 1-3-2. Drive screw; 1-3-3. Slider; 2. Laser; 3. Height gauge; 4. Right-angle fixture; 5. External light source; 6. Microscope; 7. Gasket; 8. Grating box; 9. Glue head measuring device. Detailed Implementation

[0025] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and preferred embodiments.

[0026] like Figure 1 As shown, this embodiment provides a method for assembling and adjusting a holographic concave grating monochromator, which mainly includes the following processes: grating pitch and tilt angle adjustment based on a laser, verticality adjustment of the lead screw and grating axis lever based on a right-angle tooling, and precise conjugate matching of the grating entry and exit slits based on a microscope.

[0027] Step 1: Place the holographic concave grating monochromator 1 and the laser 2 to be assembled on the optical platform and level them. The wavelength of the laser 2 is within the working band of the holographic concave grating monochromator 1, for example, the wavelength of the laser 2 is 360nm.

[0028] In this step, the holographic concave grating monochromator 1 to be assembled and adjusted and a laser 2 with a wavelength within the working band of the holographic concave grating monochromator 1 are placed together on the optical platform, and the horizontal state of the holographic concave grating monochromator 1 and the laser 2 are adjusted respectively to provide a basis for subsequent precision adjustment.

[0029] Step 2: Record the initial spot height of laser 2 using height ruler 3.

[0030] Turn on laser 2, place height ruler 3 along its light output path, measure and record the height of the laser spot center, denoted as . This height provides a reference for subsequent mapping of the multi-level spectral spot trajectory.

[0031] Step 3: Adjusting the grating pitch and tilt angles based on the laser: The laser emitted from laser 2 is incident perpendicularly to the entrance slit 1-1 of the holographic concave grating monochromator 1 onto the center of the holographic concave grating 1-3. At the exit slit 1-2 of the holographic concave grating monochromator 1, the heights of the 0th and ±1st order diffraction spots are measured and recorded using a height ruler 3, and the trajectories of the multi-order spectral spots are plotted. Then, the pitch and / or tilt angles of the holographic concave grating 1-3 are adjusted according to the trajectories of the multi-order spectral spots until the center of the 0th and ±1st order diffraction spots matches the initial spot height. The locations are collinear. In this embodiment, the holographic concave gratings 1-3 can be type IV holographic concave gratings.

[0032] Specifically, such as Figure 2 As shown, the laser emitted by laser 2 is incident perpendicularly to the entrance slit 1-1 of the holographic concave grating monochromator 1 onto the center of the holographic concave grating 1-3. A height ruler 3 is placed at the exit slit 1-2 of the holographic concave grating monochromator 1. The center heights of the 0th, +1st, and -1st order diffraction spots are measured and recorded using the height ruler 3. The trajectories of the multi-order spectral spots are plotted based on the recorded center heights of each spot.

[0033] Adjust the pitch and / or tilt angles of the holographic concave gratings 1-3 according to the trajectory of the multi-level spectral spot. The specific method is as follows:

[0034] When the centers of the 0th and ±1st order diffraction spots are collinear but at the same height as the initial spot of laser 2 When the locations are different, such as Figure 3 Trajectory in trajectory As shown, adjust the pitch angle of the holographic concave grating 1-3 at this time;

[0035] When the centers of the 0th and ±1st order diffraction spots are not collinear, such as Figure 3 Trajectory in trajectory As shown, adjust the tilt angle of the holographic concave grating 1-3 at this time.

[0036] In this embodiment, the holographic concave grating 1-3 is installed inside the grating box 8, which is fixed to the grating shaft. Multiple glue-heading devices 9 are arranged on the grating box 8, which can change the tilt angle of the holographic concave grating 1-3 relative to the grating box 8, thereby achieving precise adjustment of the pitch and tilt angles of the holographic concave grating 1-3. Optionally, as... Figure 4 As shown, three glue head actuators 9 are provided on the front surface of the grating box 8 for adjusting the pitch angle of the holographic concave grating 1-3; two glue head actuators 9 are provided on each of the four sides (top, bottom, left, and right) of the grating box 8 for adjusting the tilt angle of the holographic concave grating 1-3. By rotating the glue head actuators 9 in different positions, the spatial orientation of the holographic concave grating 1-3 can be changed. After repeated measurements and adjustments, the center of the 0th order and ±1st order diffraction spots and the initial spot height are adjusted. The locations are collinear (e.g.) Figure 3 Trajectory in (As shown).

[0037] Step 4: Adjusting the perpendicularity of the lead screw and the grating axis lever based on the right-angle fixture: Keeping the laser 2 unchanged in step 3, rotate the holographic concave grating 1-3 through the drive mechanism so that the 0th order light is emitted from the exit slit 1-2. At this time, use the right-angle fixture 4 to adjust the perpendicularity of the grating axis lever 1-3-1 and the drive lead screw 1-3-2 in the drive mechanism. After the grating axis lever 1-3-1 is perpendicular to the drive lead screw 1-3-2, lock and fix the grating axis lever 1-3-1.

[0038] According to the dispersion formula of the grating, the output wavelength of the holographic concave grating monochromator 1 satisfies the following equation:

[0039]

[0040] in, Indicates the output wavelength. This represents the period of holographic concave gratings 1-3. Indicates the diffraction order of the grating. This indicates the angle between the incident arm and the exit arm of the grating. This indicates the angle between the grating normal and the angle bisectors of the incident and exit arms.

[0041] The holographic concave grating 1-3 is rotated by a driving mechanism to switch between different monochromatic lights. The driving mechanism includes a drive screw 1-3-2 and a slider 1-3-3 threadedly engaged with the drive screw 1-3-2. The slider 1-3-3 is connected to one end of the grating axis lever 1-3-1, and the other end of the grating axis lever 1-3-1 is fixedly connected to the grating axis of the holographic concave grating 1-3. During movement, as... Figure 5As shown, the displacement of slider 1-3-3 is At this time, the rotation angle of the grating axis lever 1-3-1 around the center line of the grating is . Assuming the length of the grating axis lever 1-3-1 is... The relationship between the rotation angle of the grating axis lever 1-3-1 and the displacement of the drive screw 1-3-2 is as follows:

[0042]

[0043] when At this time, it can be ensured that the output wavelength of the monochromator is linearly related to the displacement of slider 1-3-3, that is:

[0044]

[0045] Therefore, in order to achieve linear output, it is necessary to ensure that when the 0th order light passes through the exit slit 1-2, the grating axis lever 1-3-1 is perpendicular to the drive screw 1-3-2.

[0046] Specifically, keeping the laser 2 and the holographic concave grating monochromator 1 in their current states, the grating is rotated via a drive mechanism to allow the 0th-order diffracted light to exit from the exit slit 1-2. At this time, the perpendicularity is adjusted using a right-angle fixture 4, adjusting the perpendicularity between the grating axis swing arm 1-3-1 and the drive screw 1-3-2. The specific method is as follows:

[0047] Place one right-angled edge of the right-angle fixture 4 against the reference surface of the drive screw 1-3-2, and bring the other right-angled edge of the right-angle fixture 4 towards the side of the grating axis rocker arm 1-3-1. Adjust the angle of the grating axis rocker arm 1-3-1 until the side of the grating axis rocker arm 1-3-1 is tightly fitted with the corresponding right-angled edge. After the fit is complete, it indicates that the grating axis rocker arm 1-3-1 is perpendicular to the drive screw 1-3-2. Then lock and fix the grating axis rocker arm 1-3-1 to complete the perpendicularity adjustment.

[0048] The right-angle fixture 4 in this embodiment can be of various types, such as a right-angle block, a wide-seat angle ruler, or an L-shaped right-angle ruler.

[0049] Step 5: Precise conjugate matching of the grating entrance and exit slits based on the microscope: Place the external light source 5 at the entrance slit 1-1, align the microscope 6 vertically with the exit slit 1-2, rotate the holographic concave grating 1-3 to make the characteristic spectral lines of the external light source 5 exit from the exit slit 1-2, observe the clarity of the characteristic spectral lines through the microscope 6, and adjust the thickness of the shim 7 of the exit slit 1-2 until the image of the characteristic spectral lines and the slit of the exit slit 1-2 are both clear, thus completing the precise conjugate matching of the entrance slit 1-1 and the exit slit 1-2 of the holographic concave grating 1-3.

[0050] In this embodiment, the external light source 5 is preferably a mercury lamp. For example... Figure 6As shown, the mercury lamp is placed at the entrance slit 1-1 of the holographic concave grating monochromator 1, and the microscope 6 is vertically aligned with the exit slit 1-2. The holographic concave grating 1-3 is rotated so that a characteristic spectral line of the mercury lamp (e.g., 253.7 nm or 365.0 nm) exits from the exit slit 1-2. The image clarity of the spectral line at the exit slit 1-2 is observed through the microscope 6, and the thickness of the shim 7 at the exit slit 1-2 is adjusted to change the position of the slit plate. When the image of the spectral line and the edge of the slit plate at the exit slit 1-2 are both clearly visible under the microscope 6, it indicates that the entrance slit 1-1 and the exit slit 1-2 have achieved a precise conjugate match. At this point, the assembly and adjustment of the holographic concave grating monochromator 1 are complete.

[0051] The assembly and adjustment method of the holographic concave grating monochromator 1 proposed in this invention is applicable to monochromator systems with different spectral ranges and spectral resolution levels. It is simple to operate and easy to understand, and requires less optical expertise from the operator. Even non-professionals can successfully carry out the assembly and adjustment. At the same time, the method can significantly shorten the assembly and adjustment time and ensure high assembly accuracy. Through the organic combination of laser 2, microscope 6 and right-angle tooling 4, rapid and precise assembly and adjustment of the pitch and tilt angles of the holographic concave grating 1-3, the perpendicularity of the lead screw and the grating axis swing arm, and the conjugate matching of the inlet slit 1-1 and the outlet slit 1-2 are achieved.

[0052] To verify the effectiveness of this invention, the above assembly and adjustment method was applied to the assembly and adjustment of a prototype vacuum ultraviolet monochromator. After assembly and adjustment, a mercury lamp was used for spectral testing. Since the grating of the vacuum ultraviolet monochromator is driven by a motor-driven lead screw, the number of motor steps corresponding to multiple characteristic wavelengths can be measured. Because the number of motor steps is linearly related to the output wavelength, a linear fitting function relationship between the characteristic wavelength and the number of motor steps is obtained, and the fitted value of each characteristic wavelength is then calculated, such as... Figure 7 As shown. The actual value of the characteristic wavelength is used as the calibration value, and the absolute value of the difference between the fitted value and the calibration value is the wavelength accuracy. Test results show that after assembly and adjustment using the method of this invention, the accuracy of each wavelength of the vacuum ultraviolet monochromator is better than 0.1 nm, proving the practicality and effectiveness of this assembly and adjustment method.

[0053] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0054] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for assembling and adjusting a holographic concave grating monochromator, characterized in that, Includes the following steps: Step 1: Place the holographic concave grating monochromator (1) and the laser (2) whose wavelength is within the working band of the holographic concave grating monochromator (1) on the optical platform and level them; Step 2: Record the initial spot height of the laser (2) using a height ruler (3); Step 3: The laser emitted by the laser (2) is incident perpendicularly to the entrance slit (1-1) of the holographic concave grating monochromator (1) onto the center of the holographic concave grating (1-3). The height of the 0th order and ±1st order diffraction spots is measured and recorded at the exit slit (1-2) of the holographic concave grating monochromator (1) using a height ruler (3). The trajectory of the multi-order spectral spots is plotted. The pitch angle and / or tilt angle of the holographic concave grating (1-3) are adjusted according to the trajectory of the multi-order spectral spots until the center of the 0th order and ±1st order diffraction spots is collinear with the position where the initial spot height is located. Step 4: Keep the laser (2) from Step 3 unchanged, rotate the holographic concave grating (1-3) through the drive mechanism so that the 0th order light is emitted from the exit slit (1-2). At this time, use the right angle fixture (4) to adjust the perpendicularity of the grating axis swing rod (1-3-1) and the drive screw (1-3-2) in the drive mechanism. After the grating axis swing rod (1-3-1) is perpendicular to the drive screw (1-3-2), lock and fix the grating axis swing rod (1-3-1). Step 5: Place the external light source (5) at the entrance slit (1-1), align the microscope (6) vertically with the exit slit (1-2), rotate the holographic concave grating (1-3) to make the characteristic spectral lines of the external light source (5) emerge from the exit slit (1-2), observe the clarity of the characteristic spectral lines through the microscope (6), and adjust the thickness of the shim (7) of the exit slit (1-2) until the image of the characteristic spectral lines and the slit of the exit slit (1-2) are clear at the same time, thus completing the precise conjugate matching of the entrance slit (1-1) and the exit slit (1-2) of the holographic concave grating (1-3).

2. The assembly and adjustment method of a holographic concave grating monochromator according to claim 1, characterized in that, In step 3, the pitch and tilt angles of the holographic concave grating (1-3) are adjusted by multiple glue head machines (9) set on the grating box (8).

3. The assembly and adjustment method of a holographic concave grating monochromator according to claim 2, characterized in that, The front surface of the grating box (8) is provided with three glue head machines (9) for adjusting the pitch angle of the holographic concave grating (1-3); the four sides of the grating box (8) are provided with two glue head machines (9) for adjusting the tilt angle of the holographic concave grating (1-3).

4. The assembly and adjustment method of a holographic concave grating monochromator according to any one of claims 1 to 3, characterized in that, The method for adjusting the pitch and / or tilt angle of the holographic concave grating (1-3) based on the trajectory of the multi-level spectral spot is as follows: When the centers of the 0th and ±1st order diffraction spots are collinear but at different positions from the initial spot height, adjust the pitch angle of the holographic concave grating (1-3). When the centers of the 0th and ±1st order diffraction spots are not collinear, adjust the tilt angle of the holographic concave grating (1-3).

5. The assembly and adjustment method of a holographic concave grating monochromator according to any one of claims 1 to 3, characterized in that, The driving mechanism includes the driving screw (1-3-2) and the slider (1-3-3) that is threadedly engaged with the driving screw (1-3-2). The slider (1-3-3) is connected to one end of the grating axis lever (1-3-1), and the other end of the grating axis lever (1-3-1) is fixedly connected to the grating axis of the holographic concave grating (1-3).

6. The assembly and adjustment method of a holographic concave grating monochromator according to claim 5, characterized in that, The specific method for adjusting the perpendicularity of the grating axis rocker arm (1-3-1) and the drive screw (1-3-2) in the drive mechanism using the right-angle fixture (4) is as follows: Place one right-angled side of the right-angled fixture (4) against the reference surface of the drive screw (1-3-2), and move the other right-angled side of the right-angled fixture (4) towards the side of the grating axis swing rod (1-3-1). Adjust the angle of the grating axis swing rod (1-3-1) until the side of the grating axis swing rod (1-3-1) is in close contact with the corresponding right-angled side.

7. The assembly and adjustment method of a holographic concave grating monochromator according to any one of claims 1 to 3, characterized in that, The right-angle fixture (4) is one of a right-angle block, a wide-seat angle ruler, or an L-shaped right-angle ruler.

8. A method for assembling and adjusting a holographic concave grating monochromator according to any one of claims 1 to 3, characterized in that, The holographic concave grating (1-3) is a type IV holographic concave grating.

9. A method for assembling and adjusting a holographic concave grating monochromator according to any one of claims 1 to 3, characterized in that, The external light source (5) is a mercury lamp.

10. A method for assembling and adjusting a holographic concave grating monochromator according to any one of claims 1 to 3, characterized in that, The wavelength of the laser (2) is 360nm.

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