Laser detection system for observing particles or defects of transparent sample

Abstract

The invention relates to a laser detection system for observing particles or defects of a transparent sample, and belongs to the technical field of laser measuring instruments. The light receiving lens with a special structure is arranged between the excitation light source and the light collimation system, the sample is placed between the excitation light source and the S2 surface of the light receiving lens, particles or defects on the sample are excited by the excitation light source, and refracted light is generated; refracted light is reflected for four times in the light receiving lens through the light receiving lens of a special structure and then is emitted and converged, and the light collimation system is arranged for capturing, so that the length of the whole light path system is effectively shortened, the problems of large equipment size and complex structure are solved, and meanwhile, large-numerical-aperture light energy collection can be realized.

Description

Technical Field

[0001] The invention relates to a laser detection system for observing particles or defects of a transparent sample, belonging to the technical field of laser measuring instruments. Background Art

[0002] When a tiny object (such as a particle or defect on a sample surface) is illuminated by light, its scattered light is emitted in all directions. The smaller the object, the lower the scattered energy and the wider the angle of the scattered energy distribution. This is referred to as wide-channel scattered light. A scattered light collection system must collect as much wide-channel scattered light as possible to capture sufficient scattered signal from the tiny object, enabling measurement and identification of its features or other information of interest.

[0003] In the prior art, light energy collection devices with a large light collection range (i.e., large numerical aperture NA) are often used to collect scattered light energy, such as CN119804392A and CN110426326A, which use ellipsoidal reflectors to collect light energy. However, the amount of light energy collected by the ellipsoidal reflector is closely related to the distance between the two focal points of the ellipsoid. The longer the distance, the larger the collection angle. The structural size of such a design is bound to be large, making the equipment structure complicated, which is not conducive to the installation and debugging of the equipment, stability, and cost control.

[0004] In addition, for example, CN118732248A and CN119620341A use a double-folded optical path to shorten the overall length, and the return mirror group used to collect the light energy is composed of three separate optical elements, which also makes the device structure complicated and is not conducive to the installation and debugging of the device, stability, and cost control.

[0005] Therefore, in order to solve the above problems, there is an urgent need to find a laser measurement and detection device that can collect as much excitation light energy as possible and simplify the volume structure of the device. Summary of the Invention

[0006] In response to the above problems, the present invention proposes a laser detection system for observing particles or defects in transparent samples. The laser detection system constructed with a single lens structure can realize large numerical aperture light energy collection and significantly shorten the overall length of the optical system. The structure is simple, compact and reliable.

[0007] The present invention provides a laser detection system for observing particles or defects in a transparent sample, comprising:

[0008] an excitation light source capable of emitting an excitation light beam;

[0009] a light collimation system having positive optical power and disposed in the path of the excitation light beam;

[0010] The light-collecting lens has two optical surfaces arranged opposite to each other, namely surface S1 and surface S2; surface S1 has a curvature and has a first light-transmitting hole at its center, the exterior of which is coated with a reflective film; surface S2 is a plane and has a second light-transmitting hole at its center, the exterior of which is also coated with a reflective film;

[0011] A sample is set on the side of the light-collecting lens where the S2 surface is located, and the sample is irradiated with an excitation light beam so that the particles or defects on the sample are excited to generate scattered light. The scattered light can enter the light-collecting lens through the second light-transmitting hole and be reflected four times between the two optical surfaces of the light-collecting lens before being emitted from the first light-transmitting hole. The emitted light will converge at a convergence point on the outer optical axis of the light-collecting lens, and the convergence point coincides with the focus of the light collimation system. After passing through the light collimation system, the emitted light will emit parallel light.

[0012] Furthermore, a reflector with an inclination angle of 45 degrees is arranged between the light-collecting lens and the light collimation system, and a light-blocking element is arranged on one side of the outgoing light. The reflector can convert the excess excitation light beam after passing through the light-collecting lens into a vertical light beam and direct it toward the light-blocking element for collection.

[0013] Furthermore, a relationship between the diameter D1 of the first light-transmitting hole and the diameter D2 of the second light-transmitting hole is 0.8≤D1 / D2≤1.2.

[0014] Furthermore, the relationship between the diameter D3 of the light-collecting lens, the diameter D1 of the first light-transmitting hole, and the diameter D2 of the second light-transmitting hole is D1 / D3≤1 / 3, and D2 / D3≤1 / 3.

[0015] Furthermore, the scattered light can enter the light-collecting lens through the second light-transmitting hole at a scattering angle of α to β, wherein the minimum scattering angle α=5° and the maximum scattering angle β=64°.

[0016] Furthermore, the scattered light is reflected sequentially on the S1 and S2 surfaces in the light-collecting lens through r1, r2, r3, and r4, wherein r1 and r3 are on the S1 surface, and r2 and r4 are on the S2 surface. That is, the scattered light is reflected four times in the light-collecting lens and then emitted from the first light-transmitting hole.

[0017] Furthermore, among the four reflections entering the light-collecting lens from the surface S2 at the minimum scattering angle α, the distance L2 between the fourth reflection point r4b and the optical axis O of the light-collecting lens is greater than 0.5*D2.

[0018] Furthermore, when the light enters the light-collecting lens from the S2 surface at the maximum scattering angle β, the distance L1 between the transmission position from the S1 surface after the fourth reflection and the optical axis O of the light-collecting lens is less than 0.5*D1.

[0019] Furthermore, the emitted light rays converge at a convergence point F1 on the outer optical axis of the light-collecting lens.

[0020] Beneficial effects of the present invention:

[0021] The present invention arranges a light-collecting lens with a special structure between the excitation light source and the light collimation system, places the sample between the excitation light source and the S2 surface of the light-collecting lens, and uses the excitation light source to excite particles or defects on the sample and generate refracted light. The refracted light is reflected four times in the light-collecting lens through the special structure and then emitted and converged. The light collimation system is provided to capture the refracted light, thereby effectively shortening the length of the overall optical path system, solving the problems of large equipment size and complex structure, and at the same time enabling large numerical aperture light energy collection. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention.

[0023] Figure 2 Schematic diagram of the structure of a light-collecting lens in one embodiment of the present invention.

[0024] Figure 3 This is a point diagram after light is converged by a light-collecting lens in one embodiment of the present invention.

[0025] In the figure, 1. excitation light source; 2. light-collecting lens; 3. light collimation system; 4. reflector; 5. sample; 6. light-blocking element. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0027] In the present invention, unless otherwise expressly specified or limited, the terms "connected," "connect," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0028] In the present invention, the terms "first" and "second" are only used to distinguish similar components / parts in different positions or with different characteristics, and have no other limiting meanings; the term "upper" refers to the direction in which each component is away from the ground, and the term "lower" refers to the direction in which each component is away from the ground.

[0029] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0030] The present invention proposes a laser detection system for observing particles or defects in transparent samples. The laser detection system constructed with a single lens structure can achieve large numerical aperture light energy collection and significantly shorten the overall length of the optical system. The structure is simple, compact and reliable.

[0031] The present invention provides a laser detection system for observing particles or defects in transparent samples, such as Figure 1 As shown, it includes an excitation light source 1, a sample 5, a light-collecting lens 2, a reflector 4, and a light collimation system 3 arranged from left to right. Among them:

[0032] The excitation light source 1 is a light source component capable of emitting an excitation light beam, and the excitation light beam is emitted horizontally from left to right;

[0033] The light collimation system 3 has positive optical power and is arranged on the path of the excitation light beam. It can collect and converge light from the left end and emit parallel light from the right end to achieve a light collimation effect, so that various optical elements can be used to process and analyze the collected signals later.

[0034] like Figure 2 As shown, the light-collecting lens 2 has two optical surfaces arranged opposite each other, the left and right optical surfaces being S1 and S2, respectively. Surface S1 is curvature (aspheric) and has a first light-transmitting hole at its center, which is coated with a reflective film. Surface S2 is flat and has a second light-transmitting hole at its center, which is also coated with a reflective film. Preferably, the diameter of the first light-transmitting hole is D1 = 10 mm, and the diameter of the second light-transmitting hole is D2 = 11 mm. The light-collecting lens has a diameter of D3 = 42 mm, a thickness of 17.723 mm, and an operating wavelength of 0.266 μm.

[0035] The specific parameters of the light-collecting lens 2 are shown in Table 1:

[0036] Table 1

[0037]

[0038] A sample is set on the side of the light-collecting lens 2 where the S2 surface is located. If there are tiny objects (particles or defects) at the light spot, the sample is irradiated with an excitation light beam so that the particles or defects on the sample are excited to generate scattered light. The scattered light can enter the light-collecting lens 2 through the second light-transmitting hole and be reflected four times between the two optical surfaces of the light-collecting lens before being emitted from the first light-transmitting hole. The emitted light will converge at a convergence point on the outer optical axis of the light-collecting lens 2 and the convergence point coincides with the focus of the light collimation system 3. After passing through the light collimation system 3, the emitted light will emit parallel light. Furthermore, the scattered light can enter the light-collecting lens through the second light-transmitting hole at a scattering angle of α to β, wherein the minimum scattering angle α is 30° and the maximum scattering angle β is 64°. The light between α and β is collected by the light-collecting lens 2. After the light is refracted from the light-collecting lens 2, the emitted light will converge at a convergence point F1 on the outer optical axis of the light-collecting lens. The RMS radius of the convergent spot is 0.112, which is close to the diffraction limit, and the focusing effect is good. Figure 3 shown.

[0039] Preferably, further, of the four reflections from the S2 surface entering the light-collecting lens 2 at the minimum scattering angle α, the fourth reflection point r4b is at a distance L2 = 6.3 mm from the light-collecting lens optical axis O. When the light enters the light-collecting lens from the S2 surface at the maximum scattering angle β, the distance L1 = 6 mm from the transmission position from the S1 surface after the fourth reflection to the light-collecting lens optical axis O is at a distance L1 = 6 mm.

[0040] Furthermore, in order to prevent the excitation light from entering the light collimation system, a reflector 4 with an inclination angle of 45 degrees is provided in the area between the light-collecting lens and the light collimation system where no collected light passes. The reflector 4 can reflect the excess laser light emitted from the light-collecting lens 2 on the left side downward in a direction perpendicular to the optical axis. A light-blocking element 6 is provided at a position away from the optical axis below one side of the emitted light. The reflected excess laser light can just be collected by the light-blocking element 6, thereby avoiding interference with the detection signal.

[0041] Furthermore, the scattered light is reflected in sequence by r1, r2, r3, and r4 on the S1 surface and S2 surface in the light-collecting lens 2, wherein r1 and r3 are on the S1 surface, and r2 and r4 are on the S2 surface. That is, the scattered light is reflected four times in the light-collecting lens 2 and then emitted from the first light-transmitting hole, which is equivalent to the scattered light being reflected four times between the S1 and S2 surfaces of the light-collecting lens 2. The length of the overall optical path system is effectively shortened.

[0042] The present invention uses laser to detect and measure sample defects:

[0043] Step 1: Place the surface of the transparent sample 5 to be tested at the focal point of one side of the light-collecting lens 2, and use the excitation light source 1 to emit laser light and focus it on the surface of the sample to be tested;

[0044] Step 2: Move the sample 5 along a certain path, such as moving it in a spiral outward from the center of the sample for a circular sample, or in a "bow" path for a square sample;

[0045] Step 3: During the movement process, if there are particles or defects on the sample surface, the incident laser will be scattered. The smaller the particle or defect, the wider the angle of the scattered light energy distribution. This scattered light energy enters the light-collecting lens with a large numerical aperture through the second light-transmitting hole and is collected into the lens. After being reflected four times between the S1 and S2 surfaces before and after the lens, it is transmitted through the first light-transmitting hole out of the light-collecting lens 2 and converges at a convergence point F1 on the outer optical axis of the light-collecting lens.

[0046] Step 4: After passing through point F1, the light enters the light collimation system 3 and is emitted in a collimated state;

[0047] Step 5: After being collimated by the light collimation system 3, the light beam is parallel, so there is ample space for placing various optical devices and performing various processing. For example, filters are used to obtain wavelengths of interest, polarizers are used to obtain polarization states of interest, etc. Finally, these light beams are incident on the photoelectric conversion device and converted into electrical signals. The presence, strength, corresponding wavelength, and time of appearance of the electrical signals are used to characterize the presence, size, composition, and location of particles, thereby realizing the detection of particles or defects by laser.

[0048] Although the present invention has been disclosed above in terms of preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A laser detection system for observing particles or defects in transparent samples, characterized in that: include: an excitation light source capable of emitting an excitation light beam; a light collimation system having positive optical power and disposed in the path of the excitation light beam; The light-collecting lens has two optical surfaces arranged opposite to each other, namely surface S1 and surface S2; surface S1 has a curvature and has a first light-transmitting hole at its center, the exterior of which is coated with a reflective film; surface S2 is a plane and has a second light-transmitting hole at its center, the exterior of which is also coated with a reflective film; A sample is set on the side of the light-collecting lens where the S2 surface is located, and the sample is irradiated with an excitation light beam so that the particles or defects on the sample are excited to generate scattered light. The scattered light can enter the light-collecting lens through the second light-transmitting hole and be reflected four times between the two optical surfaces of the light-collecting lens before being emitted from the first light-transmitting hole. The emitted light will converge at a convergence point on the outer optical axis of the light-collecting lens, and the convergence point coincides with the focus of the light collimation system. After passing through the light collimation system, the emitted light will emit parallel light.

2. The laser detection system according to claim 1, characterized in that A reflector with an inclination angle of 45 degrees is arranged between the light-collecting lens and the light collimation system, and a light-blocking element is arranged on one side of the outgoing light. The reflector can convert the excess excitation light beam after passing through the light-collecting lens into a vertical light beam and direct it toward the light-blocking element for collection.

3. The laser detection system according to claim 2, characterized in that: The relationship between the diameter D1 of the first light-transmitting hole and the diameter D2 of the second light-transmitting hole is 0.8≤D1 / D2≤1.

2.

4. The laser detection system according to claim 3, characterized in that: The relationship between the diameter D3 of the light-collecting lens, the diameter D1 of the first light-transmitting hole, and the diameter D2 of the second light-transmitting hole is D1 / D3≤1 / 3, and D2 / D3≤1 / 3.

5. The laser detection system according to claim 4, characterized in that: The scattered light can enter the light-collecting lens through the second light-transmitting hole at a scattering angle of α to β, wherein the minimum scattering angle α=5° and the maximum scattering angle β=64°.

6. The laser detection system according to claim 5, characterized in that: The scattered light is reflected in sequence by r1, r2, r3, and r4 on the S1 and S2 surfaces in the light-collecting lens, wherein r1 and r3 are on the S1 surface, and r2 and r4 are on the S2 surface. That is, the scattered light is reflected four times in the light-collecting lens and then emitted from the first light-transmitting hole.

7. The laser detection system according to claim 6, characterized in that: Among the four reflections entering the light-collecting lens from the surface S2 at the minimum scattering angle α, the distance L2 between the fourth reflection point r4b and the optical axis O of the light-collecting lens is greater than 0.5*D2.

8. The laser detection system according to claim 6, characterized in that: When the light enters the light-collecting lens from the S2 surface with the maximum scattering angle β, the distance L1 between the transmission position from the S1 surface after the fourth reflection and the optical axis O of the light-collecting lens is less than 0.5*D1.

9. The laser detection system according to claim 6, characterized in that: The outgoing light rays converge at a convergence point F1 on the outer optical axis of the light-collecting lens.

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