Achromatic collimated light source and optical detection system for optical detection

Abstract

The application relates to the field of optical detection equipment and discloses an achromatic collimating light source for optical detection and an optical detection system, the achromatic collimating light source comprises, in sequence along the light path direction, a white light LED lamp bead, an aspheric lens (1), a first achromatic lens (2), a first slit (3), a second achromatic lens (4) and a second slit (5), the convex surface of the aspheric lens faces the white light LED lamp bead, the focal length of the first achromatic lens is greater than that of the second achromatic lens, the interval between the first achromatic lens and the first slit is greater than that between the second achromatic lens and the second slit, and the slit width of the first slit is greater than that of the second slit. The achromatic lenses in the light path are designed and combined, the dispersion effect is reduced, the energy density and the color quality of the white light LED are ensured, and the measurement range of the system can be increased under the premise of maintaining a small volume.

Description

Technical Field

[0001] This invention relates to optical inspection equipment, and more specifically to an achromatic collimating light source for optical inspection. Furthermore, this invention also relates to an optical inspection system comprising the aforementioned achromatic collimating light source. Background Technology

[0002] This method, which uses specific reagents to react with target substances in water to form a solution of a specific color, and quantifies the specific target substances in the water by measuring the absorption (absorbance) of the solution at a specific wavelength, is a commonly used analytical technique in water quality testing. During this measurement process, it is essential to ensure the collimation of the light source and optical path to avoid light loss during propagation affecting the accuracy of the measurement results.

[0003] In recent years, with the trend of miniaturization in testing equipment, higher requirements have been placed on the size and power consumption of optical paths in optical detection. Halogen lamps and direct-through optical paths are large in size, have high power consumption, and generate a lot of heat, which is not conducive to the miniaturization of equipment. Using single-wavelength lamps as light sources cannot meet the needs of multi-wavelength measurement, while multi-wavelength lamp bead fitting is bulky and difficult.

[0004] LEDs have a wide wavelength range and, as a low-power, high-brightness, and small-size light source, have great potential in small optical systems. However, because the blue and red light in white LEDs are relatively strong, and the wavelengths of blue and red light differ significantly, dispersion is easily generated during coupling, collimation, and shaping. This has a very negative impact on the color quality and energy density of white LEDs, limiting the performance of optical testing systems. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem of dispersion that easily occurs during coupling, collimation, and shaping in the existing technology due to the strong energy of blue and red light in white LED chips and the large difference between the wavelengths of blue and red light. This invention provides an achromatic collimating light source for optical detection. This achromatic collimating light source can reduce the dispersion effect of white LED chips, ensure the energy density and color quality of white LEDs, and facilitate increasing the measurement range of the system while maintaining a small size.

[0006] To achieve the above objectives, the present invention provides an achromatic collimated light source for optical detection, comprising a white LED bead, an aspherical lens, a first achromatic lens, a first slit, a second achromatic lens, and a second slit arranged sequentially along the optical path. The convex surface of the aspherical lens faces the white LED bead. The focal length of the first achromatic lens is greater than that of the second achromatic lens, and the distance between the first achromatic lens and the first slit is greater than the distance between the second achromatic lens and the second slit. The slit width of the first slit is greater than that of the second slit.

[0007] Preferably, the aspherical lens, the first achromatic lens, and the second achromatic lens are each a rotating body, and their centers are arranged so that their centers are collinear with the centers of the first slit and the second slit.

[0008] Preferably, the white LED lamp bead, aspherical lens, first achromatic lens, first slit, second achromatic lens and second slit are coaxially fixed in the same lens sleeve.

[0009] Preferably, the white LED bead is a full-spectrum LED with a color temperature of 3500K-4500K and a divergence angle of less than 7.5°.

[0010] Preferably, the distance between the white LED bead and the aspherical lens is not greater than the focal length of the aspherical lens, and / or, the distance between the second achromatic lens and the second slit is equal to the focal length of the second achromatic lens.

[0011] Preferably, the distance between the aspherical lens and the first achromatic lens is less than 1 mm.

[0012] Preferably, the first slit and the second slit are both circular holes, wherein the diameter of the second slit is 1mm-2mm.

[0013] A second aspect of the present invention provides an optical detection system including the above-described achromatic collimating light source.

[0014] Preferably, the optical detection system further includes a microfluidic chip with a detection cell and a spectrometer. A first reflector and a second reflector are respectively provided on both sides of the detection cell. The mirror surfaces of the first reflector and the second reflector are perpendicular to each other and are configured such that the collimated light emitted from the achromatic collimating light source enters the first reflector at an incident angle of 45°, so that after passing through the detection cell, it is reflected by the second reflector to the spectrometer.

[0015] Preferably, a beam-shrinking lens is provided between the second reflector and the spectrometer, and the spectrometer is connected to an optical fiber jumper extending toward the beam-shrinking lens. The reflected light reflected by the second reflector passes through the beam-shrinking lens and the optical fiber jumper in sequence and enters the spectrometer.

[0016] Through the above technical solution, the achromatic collimating light source of the present invention utilizes achromatic technology. In the process of optical path coupling, collimation, shaping, and beam contraction, multiple achromatic lenses are designed and combined to reduce the dispersion effect of white LED beads, ensuring the energy density and color quality of white LEDs. It is used for absorption and transmission light signal measurement in a broadband wavelength range of 400nm-700nm, and the measurement range of the system can be increased while maintaining a small volume. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the composition structure of an achromatic collimating light source for optical detection according to a preferred embodiment of the present invention.

[0018] Figure 2 This is an optical path layout diagram of an optical detection system according to a preferred embodiment of the present invention;

[0019] Figure 3 This is the original light intensity distribution diagram of the white LED lamp beads in an embodiment of the present invention;

[0020] Figure 4 This is a light intensity distribution diagram of white LED beads after color difference collimation according to an embodiment of the present invention.

[0021] Explanation of reference numerals in the attached figures

[0022] 1-Aspherical lens; 2-First achromatic lens; 3-First slit; 4-Second achromatic lens; 5-Second slit; 10-Achromatic collimating light source; 20-First reflecting mirror; 30-Detection cell; 40-Second reflecting mirror; 50-Beam-contracting lens; 60-Spectrometer. Detailed Implementation

[0023] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0024] In this invention, unless otherwise stated, directional terms such as "upper," "lower," "left," and "right" generally refer to the upper, lower, left, and right as shown in the accompanying drawings; "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0025] Reference Figure 1As shown, an achromatic collimating light source for optical detection according to a preferred embodiment of the present invention includes white LED beads (not shown), an aspherical lens 1, a first achromatic lens 2, a first slit 3, a second achromatic lens 4, and a second slit 5 arranged sequentially along the optical path direction. The convex surface of the aspherical lens 1 faces the white LED beads. The focal length of the first achromatic lens 2 is greater than the focal length of the second achromatic lens 4, and the distance between the first achromatic lens 2 and the first slit 3 is greater than the distance between the second achromatic lens 4 and the second slit 5. The slit width of the first slit 3 is greater than the slit width of the second slit 5.

[0026] Thus, the white light emitted from the white LED is collimated into collimated light of a predetermined size after passing through the aspherical lens 1. This collimated light then undergoes beam contraction and collimation through the first achromatic lens 2, the second achromatic lens 4, and the first slit 3, forming light of the predetermined size. Furthermore, this light is partially filtered out by the second slit 4, resulting in the desired collimated light. The achromatic collimated light source of this invention utilizes achromatic technology, designing and combining multiple achromatic lenses during the coupling, collimation, shaping, and beam contraction processes of the optical path. This reduces the dispersion effect of the white LED, ensuring the energy density and color quality of the white LED. It is used for measuring absorption and transmission light signals in a broadband wavelength range of 400nm-700nm, increasing the system's measurement range while maintaining a small size.

[0027] As described above, the light emitted by the white LED beads passes sequentially through the aspherical lens 1, the first achromatic lens 2, the first slit 3, the second achromatic lens 4, and the second slit 5 to obtain the desired collimated light. Therefore, these components can be arranged on the same straight line. Typically, the aspherical lens 1, the first achromatic lens 2, and the second achromatic lens 4 are each a body of revolution (with a circular cross-section), and their centers are arranged collinear with the centers of the first slit 3 and the second slit 5. Depending on the testing requirements, the first slit 3 and the second slit 5 can be circular holes (small holes) or slits in the conventional sense. In the preferred embodiment illustrated, the first slit 3 and the second slit 5 are slits with diameters of 2 mm and 1.5 mm (i.e., the aforementioned slit widths), respectively.

[0028] To ensure coaxiality and facilitate optical testing, the aforementioned white LED beads, aspherical lens 1, first achromatic lens 2, first slit 3, second achromatic lens 4, and second slit 5 can be coaxially fixed within the same lens sleeve.

[0029] In this invention, the white LED beads used are preferably cap-type LED beads with a divergence angle of less than 7.5°. Furthermore, full-spectrum LEDs with a color temperature of around 4000K are easier to collimate than pure white LEDs with higher color temperatures. Therefore, the white LED beads can be selected as full-spectrum LEDs with a color temperature between 3500K and 4500K.

[0030] In the preferred embodiment illustrated, the aspherical lens 1 is a circular aspherical lens with a focal length of 7.5 mm and a diameter of 12 mm, placed approximately 6 mm behind the white LED. The convex surface of the aspherical lens 1 faces the white LED, and light is emitted from the lens, thereby collimating the light source into a collimated beam with a diameter of approximately 10 mm.

[0031] The first achromatic lens 2 has a focal length of 8mm and a diameter of 12mm. It is placed close to the aspherical lens 1, at a distance of ≤1mm. A first slit 3 with a diameter of 2mm is placed approximately 8.5mm away from the first achromatic lens 2 to filter out some stray light. A second achromatic lens 4 with a focal length of 4mm and a diameter of 12mm is placed approximately 4mm away from the first slit 3. A second slit 5 with a diameter of 1.5mm is placed 4mm behind the second achromatic lens 4. The first achromatic lens 2, the second achromatic lens 4, and the first slit 3 collimate and focus the light source, resulting in a light spot size of approximately 4mm. The second slit 5 filters out some divergent light, producing a collimated light spot size of 2mm.

[0032] Based on this, the present invention also provides an optical detection system having the above-mentioned achromatic collimated light source, such as... Figure 2 As shown. In this preferred embodiment of the optical detection system, in addition to the achromatic collimating light source 10, it may also include a microfluidic chip with a detection cell 30 and a spectrometer 60. A first reflecting mirror 20 and a second reflecting mirror 40 are respectively provided on both sides of the detection cell 30. The mirror surfaces of the first reflecting mirror 20 and the second reflecting mirror 40 are perpendicular to each other. The collimated light emitted from the achromatic collimating light source 10 is positioned so that it enters the first reflecting mirror 20 at a 45° incident angle, and after passing through the detection cell 30, is reflected by the second reflecting mirror 40 to the spectrometer 60. Thus, this optical detection system adopts a folding optical path design, which is beneficial for the portable development of optical signal analysis equipment. The light output from the achromatic collimating light source 10 is collimated and beam-contracted before entering the first reflecting mirror 20. The first reflecting mirror 20 reflects the light 90°, then it passes through the small-sized detection cell 30 (such as the detection cell of the microfluidic chip) directly below it, and then enters the second reflecting mirror 40. The light is then reflected 90° again, refocused, and enters the spectrometer 60. It is understood that the above is only a preferred but not the only application scenario of the present invention, which is to be used in conjunction with a microfluidic chip to measure the absorbance of the liquid in the detection cell of the microfluidic chip.

[0033] The achromatic technology in this invention is applied throughout the entire optical path. That is, the reflected optical path must include a white LED light source processed using achromatic technology and a beam-shrinking and focusing process before entering the spectrometer to ensure the collimation and intensity of the light source. The light emitted from the light source, after collimation and beam shrinking, has a spot diameter of approximately 2mm. After passing through two reflectors, the exit spot is slightly larger than the incident spot (approximately 3mm). At this point, the light needs to be focused (approximately 2mm) by a beam-shrinking lens 50 (aspherical lens) before entering the spectrometer 60.

[0034] The distance between the achromatic collimating light source 10 and the first reflecting mirror 20 should be maintained between 5mm and 8mm, and they need to be coaxially mounted to ensure that the light enters the detection cell 30 perpendicularly. The first reflecting mirror 20 and the second reflecting mirror 40 need to be coaxially mounted, with a distance of 10mm-15mm between them. The second reflecting mirror 40, the beam shrinking lens 50, and the fiber optic jumper described later should all be placed coaxially, with a distance of 5mm-8mm between the second reflecting mirror 40 and the beam shrinking lens 50. The entire optical path length from the achromatic collimating light source 10 to entering the spectrometer 60 should be less than 30mm.

[0035] exist Figure 2 In the optical detection system shown, the spectrometer 60 can receive reflected light signals via a short fiber optic jumper. This involves coupling the light focused by the beam-shrinking lens 50 into a 30mm long optical fiber, allowing the light to undergo uniform total internal reflection within the fiber. The fiber is then inserted into the port of the spectrometer 60, allowing the light to enter the spectrometer 60. Using a short fiber optic cable simplifies the interface for light entering the spectrometer and reduces light loss.

[0036] The aforementioned small-sized detection cells are made of transparent media, such as quartz, glass, polymethyl methacrylate (PMMA), polycarbonate (PC), and polystyrene (PS), which do not absorb light in the wavelength range of 400nm-700nm. The size of the detection cell in the direction perpendicular to the light can be 2mm-10mm.

[0037] The achromatic collimating light source and optical detection system of this invention enable achromatic and focusing of higher-brightness LED light sources while maintaining a miniaturized optical path design and increasing light source power. This solves the problem of not being able to use high-power light sources in current small optical paths. This invention also addresses the issue of insufficient power supply in miniature optical paths, enabling its widespread application in portable instruments and demonstrating promising application and market prospects.

[0038] Example 1 This example illustrates the implementation method of the achromatic collimated light source of the present invention.

[0039] like Figure 1 and Figure 2As shown, a T-1 3 / 4 packaged white LED, a circular aspherical lens 1 with a focal length of 7.5mm and a diameter of 12mm, a first achromatic lens 2 with a focal length of 8mm and a diameter of 12mm, a first slit 3 with an aperture diameter of 2mm, a second achromatic lens 4 with a focal length of 4mm and a diameter of 12mm, and a second slit 5 with an aperture diameter of 1.5mm are placed coaxially and connected and fixed with a lens sleeve. The white LED lamp bead and aspherical lens 1 are 6mm apart, with the convex surface of aspherical lens 1 facing the white LED lamp bead. The first achromatic lens 2 is placed close to the aspherical lens 1, less than 1mm apart. The distance between the first slit 3 and the first achromatic lens 2 is 8.5mm. The distance between the second achromatic lens 4 and the second slit 5 is 4mm. The first reflector 20 is placed 20mm behind the second achromatic lens 4, and the second slit 5 is placed 4mm behind the second achromatic lens 4. The first reflector 20 faces the achromatic collimated light source 10 and forms a 45° angle with the axis. The second reflector 40 is placed 12mm vertically below the first reflector 20, mirroring it. Both the first reflector 20 and the second reflector 40 are RAP110-A type and 10mm in length.

[0040] The light emitted by the achromatic collimated light source 10 is reflected by two mirrors and then refracted back in parallel. On the returning light path, an aspherical lens (beam-shrinking lens 50) is placed 15mm from the second mirror. Along the direction of the light path, a 30mm short fiber optic jumper is fixed 6mm after the beam-shrinking lens 50, with the convex surface of the beam-shrinking lens 50 facing the jumper. The other end of the jumper is connected to the spectrometer 60. In this embodiment, a Marine Optics STS spectrometer is used. The beam-shrinking lens 50 is fixed with a lens sleeve, which is connected to an SMA905 threaded fiber optic cable. The other end of the jumper is then connected to the spectrometer 60 via an SMA905 thread, and the spectrometer is then fixed by the main body structure.

[0041] After the optical path is arranged, the white LED beads and the spectrometer are powered by power lines at 5V and currents of 100mA and 300mA, respectively. The original light intensity distribution of the white LED beads and the light intensity distribution at different wavelengths after achromatic collimation as described in this embodiment are as follows: Figure 3 and Figure 4 As shown, after the white LED beads are collimated by the color difference correction method in this embodiment, the wavelength and light intensity distribution are the same as the original wavelength distribution.

[0042] Based on the achromatic collimating optical path design in this embodiment, the absorbance of the red and blue solutions with an optical path of 3 mm at 550 nm and 650 nm, respectively, was detected. The results of 6 repeated detections are shown in Table 1 and Table 2.

[0043] Table 1. Repeatability test results of the red solution at 550 nm wavelength.

[0044]

[0045] Table 2. Repeatability test results of the blue solution at 650 nm wavelength.

[0046]

[0047]

[0048] The results show that the repeatability of the absorbance measurement of the solution in this embodiment is good.

[0049] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. However, these simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An achromatic collimating light source for optical detection, characterized in that, The system includes white LED beads, an aspherical lens (1), a first achromatic lens (2), a first slit (3), a second achromatic lens (4), and a second slit (5) arranged sequentially along the optical path. The convex surface of the aspherical lens (1) faces the white LED beads. The focal length of the first achromatic lens (2) is greater than the focal length of the second achromatic lens (4), and the distance between the first achromatic lens (2) and the first slit (3) is greater than the distance between the second achromatic lens (4) and the second slit. The spacing between (5) is such that the slit width of the first slit (3) is greater than the slit width of the second slit (5); the white LED is a full-spectrum LED with a color temperature of 3500K-4500K and a divergence angle of less than 7.5°; the spacing between the white LED and the aspherical lens (1) is not greater than the focal length of the aspherical lens (1), and / or the spacing between the second achromatic lens (4) and the second slit (5) is equal to the focal length of the second achromatic lens (4).

2. The achromatic collimating light source for optical detection according to claim 1, characterized in that, The aspherical lens (1), the first achromatic lens (2), and the second achromatic lens (4) are each a rotating body, and their centers are arranged so that their centers are collinear with the centers of the first slit (3) and the second slit (5).

3. The achromatic collimating light source for optical detection according to claim 2, characterized in that, The white LED beads, aspherical lens (1), first achromatic lens (2), first slit (3), second achromatic lens (4), and second slit (5) are coaxially fixed in the same lens sleeve.

4. The achromatic collimating light source for optical detection according to claim 1, characterized in that, The distance between the aspherical lens (1) and the first achromatic lens (2) is less than 1 mm.

5. The achromatic collimating light source for optical detection according to claim 1, characterized in that, The first slit (3) and the second slit (5) are circular holes, wherein the diameter of the second slit (5) is 1mm-2mm.

6. An optical detection system, characterized in that, The optical inspection system includes an achromatic collimating light source (10) according to any one of claims 1 to 5.

7. The optical detection system according to claim 6, characterized in that, It also includes a microfluidic chip with a detection cell (30) and a spectrometer (60). The detection cell (30) has a first reflector (20) and a second reflector (40) on its two sides respectively. The mirror surfaces of the first reflector (20) and the second reflector (40) are perpendicular to each other and are configured such that the collimated light emitted from the achromatic collimating light source (10) enters the first reflector (20) at an incident angle of 45°, so that after passing through the detection cell (30), it is reflected by the second reflector (40) to the spectrometer (60).

8. The optical detection system according to claim 7, characterized in that, A beam-shrinking lens (50) is provided between the second reflector (40) and the spectrometer (60). The spectrometer (60) is connected to an optical fiber jumper extending toward the beam-shrinking lens (50). The reflected light reflected by the second reflector (40) passes through the beam-shrinking lens (50) and the optical fiber jumper in sequence and enters the spectrometer (60).

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