Large-image-field imaging spectrometer suitable for line spectral measurement

Abstract

The utility model relates to a large-image-field imaging spectrometer suitable for line spectrum measurement. The large-image-field imaging spectrometer comprises an entrance slit, a collimating lens group, a diffraction grating, a focusing lens group and a detector which are sequentially arranged along the light propagation direction, a multi-color line light source is introduced into the entrance slit, the collimating lens group collimates multi-color light into parallel light beams, the parallel light beams enter the diffraction grating, light with different wavelengths is emitted from the grating at different diffraction angles, and after the emitted parallel light beams pass through the focusing lens group, the light with different wavelengths is focused at different positions in the horizontal direction of the detector and is sequentially distributed along with increasing of the wavelengths. And the light sources at different positions in the slit direction are sequentially focused at different positions in the vertical direction of the detector after passing through the spectrograph. The linear spectrum confocal displacement sensor is suitable for being used as a built-in spectrograph of the linear spectrum confocal displacement sensor, and has the advantages of large linear field of view, low cost, high spatial resolution capability and high spectral resolution capability.

Description

Technical Field

[0001] This utility model relates to the field of spectral measurement instrument technology, specifically to a large image field imaging spectrometer suitable for line spectrum measurement. Background Technology

[0002] Spectral confocal displacement measurement technology is widely used in intelligent manufacturing due to its high precision, non-contact nature, and adaptability to materials with varying reflectivity. Applications include wafer surface inspection, glass thickness measurement, roughness measurement, and lens contour inspection. A line-scanning spectral confocal displacement sensor can obtain relative distance information across a single line field of view; the larger the line field of view, the higher the measurement efficiency. Line scanning is more suitable than point-scanning spectral confocal measurement for rapid, precise 3D measurements, such as PCB key height measurement, mobile phone screen curvature and defect measurement, and MEMS structure measurement.

[0003] Compared to the spectrometer in point spectral confocal measurement sensors, the spectrometer built into line spectral confocal sensors requires not only spectral resolution but also spatial resolution, falling under the category of imaging spectrometers. Imaging spectrometers can be categorized by their dispersive method: dispersive imaging spectrometers, filter-type imaging spectrometers, interferometric imaging spectrometers, and computational imaging spectrometers. Considering technical challenges, spectral resolution, and spatial resolution, the grating-based dispersive method is the optimal choice for line spectral confocal displacement measurement applications. Common grating-based imaging spectrometers, such as the Offner structure, employ a convex grating combined with an off-axis aspherical reflective optical path. The high fabrication cost of the grating and the difficulty in assembling and adjusting the off-axis reflective optical path make them unsuitable for commercial applications. Furthermore, to reduce design complexity, the collimating and focusing optical paths in common imaging spectrometers have focal lengths equal to or close to each other. This results in the detector's spatial length being equal to or close to the object-side field of view. For larger field-of-view requirements, this necessitates a larger detector size, increasing costs. Utility Model Content

[0004] The purpose of this invention is to overcome the problems existing in the prior art and provide a large image field imaging spectrometer suitable for line spectrum measurement. It uses a planar grating as the beam splitting element, and both the collimating optical path and the focusing optical path adopt a coaxial transmission system. At the same time, the ratio of the focal length of the collimating lens to the focal length of the focusing lens is much greater than 1, so that a small-sized detector can complete a large line field of view detection.

[0005] To achieve the above-mentioned technical objectives and effects, this utility model is implemented through the following technical solution:

[0006] A large-field imaging spectrometer suitable for line spectral measurements includes an entrance slit, a collimating lens group, a diffraction grating, a focusing lens group, and a detector arranged sequentially along the direction of light propagation; wherein:

[0007] The entrance slit is located on the object-side focal plane of the collimating lens group and is used to introduce a linear polychromatic light source.

[0008] The collimating lens group is used to collimate the incident light from the slit into a parallel beam and incident it onto the diffraction grating.

[0009] The diffraction grating is used to separate the incident parallel light according to wavelength, and light of different wavelengths exits at different angles toward the focusing lens group.

[0010] The focusing lens group is used to receive the diffracted beam of the diffraction grating and focuses it on different positions of the detector according to the wavelength and the position of the slit where the light source is located, and is distributed sequentially as the wavelength increases.

[0011] The detector is positioned on the image-side focal plane of the focusing lens group to receive the light signal focused by the focusing lens group. Light emitted from different positions of the slit will be distributed at different positions in the vertical direction of the detector, serving as the spatial resolution dimension of the spectrometer. Light of different wavelengths at the same position on the slit will be distributed at different positions in the horizontal direction of the detector, serving as the spectral resolution dimension of the spectrometer.

[0012] Furthermore, the entrance slit is a rectangular linear light-transmitting aperture.

[0013] Furthermore, the collimating lens group is an object-side telecentric lens group, composed of multiple single lenses.

[0014] Furthermore, the diffraction grating is a planar reflective grating or a transmissive grating, and the grating scribe line direction is consistent with the direction of the incident slit.

[0015] Furthermore, the focusing lens group is composed of multiple single lenses.

[0016] Furthermore, the detector is a planar array detector.

[0017] The beneficial effects of this utility model are:

[0018] This invention employs a common planar grating, a coaxial transmission collimating optical path, a coaxial transmission focusing optical path, and a small-size area array detector to realize a large image field imaging spectrometer suitable for line spectrum measurement. It is suitable as a built-in spectrometer for use as a line spectrum confocal displacement sensor, featuring a large line field of view, low cost, high spatial resolution, and high spectral resolution. The spectrometer's image magnification is less than 1 / 2.9. Under the requirement of a large line field of view, the required detector height is small, and small-size area array detectors are easier to obtain and have lower costs. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the grating spectrometer of this utility model - spectral dimension;

[0020] Figure 2 This is a schematic diagram of the grating spectrometer of this utility model - spatial dimension.

[0021] The labels in the diagram are as follows: 1. Entrance slit, 2. Collimating lens group, 3. Diffraction grating, 4. Focusing lens group, 5. Detector. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] A large-field imaging spectrometer suitable for line spectrum measurement includes an entrance slit 1, a collimating lens group 2, a diffraction grating 3, a focusing lens group 4, and a detector 5 arranged sequentially along the direction of light propagation; wherein:

[0024] The entrance slit 1 is disposed on the object-side focal plane of the collimating lens group 2 and is used to introduce a linear polychromatic light source;

[0025] The collimating lens group 2 is used to collimate the incident light from the slit into a parallel beam and incident it onto the diffraction grating 3;

[0026] The diffraction grating 3 is used to separate the incident parallel light according to wavelength, and light of different wavelengths is emitted at different angles toward the focusing lens group 4.

[0027] The focusing lens group 4 is used to receive the diffraction beam of the diffraction grating 3 and focus it on different positions of the detector 5 according to the wavelength and the position of the slit where the light source is located, and distributes them sequentially as the wavelength increases.

[0028] The detector 5 is positioned on the image-side focal plane of the focusing lens group 4 to receive the light signal focused by the focusing lens group 4. Light emitted from different positions of the slit will be distributed at different positions in the vertical direction of the detector 5, such as... Figure 2 As shown, representing the spatial resolution dimension of the spectrometer, light of different wavelengths at the same location on the slit will be distributed at different positions in the horizontal direction of detector 5, such as... Figure 1 As shown, this represents the spectral resolution dimension of the spectrometer.

[0029] The entrance slit 1 is a rectangular linear light-transmitting aperture.

[0030] The collimating lens group 2 is an object-side telecentric lens group, which consists of multiple single lenses.

[0031] The diffraction grating 3 is a planar reflective grating or a transmissive grating, which has mature manufacturing technology and is suitable for commercial applications. The direction of the grating lines is consistent with the direction of the incident slit 1.

[0032] The focusing lens group 4 is composed of multiple single lenses. The collimating lens group 2 and the focusing lens group 4 adopt a coaxial transmission optical path with multiple lenses. Under the requirement of a large linear field of view, the system has good imaging quality, high spatial resolution, and low installation and adjustment difficulty.

[0033] The detector 5 is a planar array detector.

[0034] In this embodiment, the design parameters of the spectrometer are as follows:

[0035] Operating wavelength: 0.45–0.7 μm;

[0036] Object space NA: 0.2;

[0037] Slit length range: 35–37 mm;

[0038] Planar image size: 12.5mm (spatial dimension) × 9mm (spectral dimension);

[0039] Collimating lens group 2 has a positive focal length, contains 12 individual lenses, and has a focal length of f1. Focusing lens group 4 has a positive focal length, contains 10 individual lenses, and has a focal length of f2.9. <f1 / f2<3.1;

[0040] Diffraction gratings 3 are not limited to planar reflective gratings; they are also applicable to planar transmissive gratings.

[0041] The optimal order and incident angle of the grating diffraction order and the angle between the optical axis of the collimating lens group and the grating normal are selected based on the diffraction efficiency characteristics of the chosen grating.

[0042] The angle between the optical axis of the focusing lens group 4 and the grating normal is determined by a combination of the selected grating parameters, the working diffraction order, the incident angle, and the working wavelength range.

[0043] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A large-field imaging spectrometer suitable for line spectral measurements, characterized in that, It includes an entrance slit (1), a collimating lens group (2), a diffraction grating (3), a focusing lens group (4), and a detector (5) arranged sequentially along the direction of light propagation; wherein: The entrance slit (1) is located on the object-side focal plane of the collimating lens group (2) and is used to introduce a linear polychromatic light source; The collimating lens group (2) is used to collimate the incident light from the slit into a parallel beam and incident it onto the diffraction grating (3); The diffraction grating (3) is used to separate the incident parallel light according to wavelength, and the light of different wavelengths is emitted at different angles to the focusing lens group (4); The focusing lens group (4) is used to receive the diffraction beam of the diffraction grating (3) and focus it on different positions of the detector (5) according to the wavelength and the position of the slit where the light source is located, and distribute them sequentially as the wavelength increases. The detector (5) is set on the image-side focal plane of the focusing lens group (4) to receive the light signal focused by the focusing lens group (4). The light emitted from different positions of the slit will be distributed at different positions in the vertical direction of the detector (5), which serves as the spatial resolution dimension of the spectrometer. The light of different wavelengths at the same position on the slit will be distributed at different positions in the horizontal direction of the detector (5), which serves as the spectral resolution dimension of the spectrometer.

2. The large image field imaging spectrometer suitable for line spectral measurement according to claim 1, characterized in that, The entrance slit (1) is a rectangular linear light-transmitting hole.

3. The large image field imaging spectrometer suitable for line spectral measurement according to claim 1, characterized in that, The collimating lens group (2) is an object-side telecentric lens group, which consists of multiple single lenses.

4. The large image field imaging spectrometer suitable for line spectral measurement according to claim 1 or 2, characterized in that, The diffraction grating (3) is a planar reflective grating or a transmissive grating, and the direction of the grating lines is consistent with the direction of the incident slit (1).

5. The large image field imaging spectrometer suitable for line spectral measurement according to claim 1 or 3, characterized in that, The focusing lens group (4) is composed of multiple single lenses.

6. The large image field imaging spectrometer for line spectral measurement according to claim 1, characterized in that, The detector (5) is a planar array detector.

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