Light path switching device for optical detection system

Abstract

A light path switching device for an optical detection system comprises a first off-axis reflector configured to be installed on a light emitting path of a light source, and a second off-axis reflector configured to be installed on the light emitting path of the light source and not overlapped with the light emitting path, covered by the first off-axis reflector, of the light source. By means of the two off-axis reflectors with the two non-overlapped light emitting paths, the same light source can reflect two light beams with different purposes, and the utilization rate of the light source is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of optical detection, and in particular to an optical path switching device for an optical detection system. Background Art

[0002] In optical inspection systems, it is often necessary to perform various types of inspections or inspections for different purposes on the inspection object. For example, in the semiconductor production process, in order to ensure the quality of semiconductor devices, it is necessary to inspect the film thickness, critical dimension (CD), surface defects, alignment errors, etc. Different types of inspection units may also be used, such as a wide spectrum ellipsometer (SE, Spectroscopic Ellipsometer), a reflectance spectrometer (SR, SpectroReflectometer), etc. Sometimes it is also necessary to image the inspection object.

[0003] In this case, it would be a more economical choice if the same light source could be used to provide light beams for multiple light paths with different purposes. However, the detection system in the prior art has the problems of high cost and low light source utilization. Summary of the invention

[0004] The main technical problem solved by the present invention is that the existing detection system cannot conveniently switch the optical path and improve the utilization rate, and a more economical optical path switching device is needed.

[0005] According to the first aspect, an embodiment provides an optical path switching device for an optical detection system, comprising:

[0006] The first off-axis reflector is configured to be installed on the light path of the light source.

[0007] The second off-axis reflector is configured to be installed on the light output path of the light source and not overlap with the light output path of the light source covered by the first off-axis reflector.

[0008] In one embodiment, it further includes:

[0009] The first movable reflector is configured to be movably mounted on the light output path of the first off-axis reflector, and can cut in or out of the light output path of the first off-axis reflector, so that the subsequent light path changes between a first cut-in state and a first cut-out state.

[0010] In one embodiment, it further includes:

[0011] a third reflector and / or a fourth reflector,

[0012] The third reflector is configured to be installed on the light output path of the first off-axis reflector in the first cut-out state,

[0013] The fourth reflector is configured to be installed on the light output path of the second off-axis reflector.

[0014] In one embodiment,

[0015] In the first cutting state, the light output path of the first movable reflector, the light output path of the third reflector, and the light output path of the fourth reflector are each selectively connected to subsequent light paths providing different purposes, and the purposes can be selected from: imaging, wide spectrum ellipsometer detection, and reflection spectrometer detection.

[0016] In one embodiment, the light source is a wide wavelength light source, and the device further comprises:

[0017] At least one filter wheel is configured to filter and provide light of different wavelength ranges, and is arranged on the light output path of the first off-axis reflector and / or the second off-axis reflector.

[0018] In one embodiment, it further includes:

[0019] The aperture assembly is configured to be arranged in the light path to reduce the divergence angle of the light beam.

[0020] In one embodiment, the first off-axis reflector and / or the second off-axis reflector is an off-axis parabolic reflector.

[0021] In one embodiment, the first off-axis reflector and the second off-axis reflector have a common focus, and the light source is arranged at the common focus. Preferably, the first off-axis reflector and the second off-axis reflector have the same focal length.

[0022] In one embodiment, the offset angle range between the central optical axis of the incident light path of the first off-axis reflector and the central optical axis of the light beam of the light source is 10° to 30°, preferably 15°; the offset angle range between the central optical axis of the incident light path of the second off-axis reflector and the central optical axis of the light beam of the light source is 10° to 30°, preferably 15°.

[0023] In one embodiment, the distance between the light source and the first and second off-axis reflectors is in a range of 2 to 8 centimeters, and the mirror size of the first and second off-axis reflectors is in a range of 1 to 6 centimeters.

[0024] According to the optical path switching device for an optical detection system of the above embodiment, two off-axis reflectors with non-overlapping light output paths can reflect two light beams for different purposes from the same light source, thereby improving the utilization rate of the light source. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of the structure of an optical path switching device provided in one embodiment of the present application (I);

[0026] Figure 2A schematic diagram of the structure of an optical path switching device provided in one embodiment of the present application (II);

[0027] Figure 3 A schematic diagram of the structure of an optical path switching device provided in one embodiment of the present application (III);

[0028] Figure 4 A schematic diagram of the structure of an optical path switching device provided in one embodiment of the present application (IV);

[0029] Figure 5 A schematic diagram of the structure of an optical path switching device provided in one embodiment of the present application (V);

[0030] Figure 6 A structural schematic diagram of an optical path switching device provided in one embodiment of the present application (VI);

[0031] Figure 7 A schematic diagram of the structure of an optical path switching device provided in one embodiment of the present application (VII);

[0032] Figure 8 For the corresponding Figure 1 Left view of

[0033] Fig. 9 For the corresponding Figure 4 Left view of

[0034] Fig.10 A schematic diagram of the structure of an optical detection system.

[0035] Figure numerals: 1 - light source; 2 - first off-axis reflector; 30 - first movable reflector; 31 - second movable reflector; 32 - third reflector; 33 - fourth reflector; 4 - second off-axis reflector; 50 - filter wheel; 60 - aperture assembly. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below by specific embodiments in conjunction with the accompanying drawings. Wherein similar elements in different embodiments adopt associated similar element numbers. In the following embodiments, many detailed descriptions are for making the present application better understood. However, those skilled in the art can easily recognize that some features can be omitted in different situations, or can be replaced by other elements, materials, methods. In some cases, some operations related to the present application are not shown or described in the specification, this is to avoid the core part of the present application being overwhelmed by too much description, and for those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations according to the description in the specification and the general technical knowledge in the art.

[0037] In addition, the features, operations or characteristics described in the specification can be combined in any appropriate manner to form various implementations. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment and are not meant to be a required sequence, unless otherwise specified that a certain sequence must be followed.

[0038] The serial numbers of the components in this document, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in this application, unless otherwise specified, include direct and indirect connections (couplings).

[0039] Embodiment 1

[0040] like Figure 1 As shown, an embodiment of the present application provides an optical path switching device for an optical detection system, which may include: a first off-axis reflector 2 and a first movable reflector 30 .

[0041] The first off-axis reflector 2 is configured to be installed on the light path of the light source 1. The off-axis reflector is an optical element that can change the direction of light transmission, and can reflect light to other positions in the off-axis direction while maintaining the phase and amplitude of the light. A high-quality, highly collimated light beam can be formed by the light reflected on the off-axis reflector. By collimating the light beam of the light source 1 in this way, the propagation direction of the light can be made more consistent, which is suitable for fields such as optical detection and precision manufacturing that require high precision.

[0042] The first movable reflector 30 is configured to be movably mounted on the light output path of the first off-axis reflector 2, and can cut into or out of the light output path of the first off-axis reflector 2, so that the subsequent light path changes between a first cut-in state and a first cut-out state. The first movable reflector 30 can be driven by a displacement actuator, such as Figure 1 The first movable reflector 30 can be moved into or out of the transmission optical path of the light reflected by the first off-axis reflector 2.

[0043] like Figure 1 As shown in (A) in FIG. 1 , when the first movable reflector 30 cuts into the light path of the first off-axis reflector 2 (i.e., in the first cut-in state), the light beam emitted by the light source 1 can be transmitted to the first detection unit after being reflected by the first off-axis reflector 2 and the first movable reflector 30. Figure 1As shown in (B), when the first movable reflector 30 cuts out the light path of the first off-axis reflector 2 (i.e., in the first cut-out state), the light beam emitted by the light source 1 can be transmitted to the second detection unit after being reflected by the first off-axis reflector 2. The first detection unit and the second detection unit can be selectively connected to subsequent light paths that provide different purposes, including but not limited to: imaging, wide spectrum ellipsometer detection, and reflection spectrometer detection.

[0044] In this embodiment, a combination of an off-axis reflector and a movable reflector can be used to split two paths of light, and the two paths of light can enter different detection light paths. In other embodiments, the number of off-axis parabolic mirrors can be other values, and the number of movable reflectors can be multiple to perform multi-path beam splitting.

[0045] In some embodiments, when the optical path switching device includes the first movable reflecting mirror 30 , it may further include: a second movable reflecting mirror 31 .

[0046] The second movable reflector 31 is configured to be movably mounted on the light-emitting path of the first off-axis reflector 2 in the first cut-out state, so that the subsequent light path changes between the second cut-in state and the second cut-out state.

[0047] For example, Figure 2 As shown in (A) in FIG. 1 , when the first movable reflector 30 cuts into the light path of the first off-axis reflector 2, the light beam emitted by the light source 1 can be transmitted to the first detection unit after being reflected by the first off-axis reflector 2 and the first movable reflector 30. Figure 2 As shown in (B) in FIG. 1 , when the first movable reflector 30 cuts out the light path of the first off-axis reflector 2 and the second movable reflector 31 cuts into the light path of the first off-axis reflector 2 (i.e., in the second cut-in state), the light beam emitted by the light source 1 can be transmitted to the second detection unit after being reflected by the first off-axis reflector 2 and the second movable reflector 31. Figure 2 As shown in (C), when the first movable reflector 30 cuts out the light path of the first off-axis reflector 2, and the second movable reflector 31 cuts out the light path of the first off-axis reflector 2 (i.e., in the second cut-out state), the light beam emitted by the light source 1 can be transmitted to the third detection unit after being reflected by the first off-axis reflector 2. The first detection unit, the second detection unit, and the third detection unit can each be selectively connected to a subsequent light path providing different purposes, including but not limited to: imaging, wide spectrum ellipsometer detection, and reflection spectrometer detection.

[0048] In some embodiments, Figure 3 As shown, the optical path switching device may further include: a third reflecting mirror 32 .

[0049] The third reflector 32 is configured to be installed on the light-emitting path of the first off-axis reflector 2 in the second cut-out state.

[0050] The propagation direction of the laser can be changed by the third reflector 32 so that it can be emitted at a desired location, for example, Figure 3 As shown, the light path exits corresponding to the first detection unit, the second detection unit and the third detection unit can be located on the same side, so that the operator can obtain the light beam for detection.

[0051] In this embodiment, the light beam generated by the light source 1 is collimated by an off-axis reflector so that the light beam is emitted in parallel to a subsequent light path. The light path is switched in the subsequent light path by a movable reflector that can be switched in / out so that the light beam enters a different light path, such as SE, SR or imaging light input path.

[0052] In order to ensure that each optical path can select the required wavelength, the optical path switching device can also have a filter wheel 50. The filter wheel 50 is a double-wheel structure, which can provide light of different wavelengths for SE, SR and imaging. At the same time, the light beam is collimated by an off-axis parabolic mirror, and the distance between the off-axis parabolic mirror and the SE and other optical paths can be adjusted, thereby providing space for setting the filter wheel 50.

[0053] Embodiment 2

[0054] like Figure 4 As shown, an embodiment of the present application further provides an optical path switching device for an optical detection system, which may include: a first off-axis reflector 2 and a second off-axis reflector 4 .

[0055] The first off-axis reflector 2 is configured to be installed on the light path of the light source 1.

[0056] The second off-axis reflector 4 is configured to be installed on the light output path of the light source 1 and not overlap with the light output path of the light source 1 covered by the first off-axis reflector 2 .

[0057] For example, Figure 4 As shown, a plurality of off-axis reflectors arranged side by side are arranged in the optical path, the arrangement direction of the first off-axis reflector 2 and the second off-axis reflector 4 are in different planes from the incident surface, the light source 1 (such as a laser) can be located at the focal position of the first off-axis reflector 2 and the second off-axis reflector 4, and the first off-axis reflector 2 and the second off-axis reflector 4 collimate the incident light beam. The light beam emitted through the first off-axis reflector 2 enters the first detection unit; the light beam emitted through the second off-axis reflector 4 enters the third detection unit. The first detection unit and the third detection unit can be selectively connected to subsequent optical paths that provide different purposes, and the purposes can be selected from: imaging, wide spectrum ellipsometer detection, and reflection spectrometer detection.

[0058] In this embodiment, two off-axis reflectors are used to split the two paths of light, which enter different detection light paths respectively. In other embodiments, the number of off-axis parabolic mirrors can be other values ​​to perform multi-path beam splitting.

[0059] like Figure 5 As shown, in some embodiments, when the device includes the second off-axis reflector 4 , it may further include: a third reflector 32 and / or a fourth reflector 33 .

[0060] The third reflector 32 is configured to be installed on the light-emitting path of the first off-axis reflector 2. The fourth reflector 33 is configured to be installed on the light-emitting path of the second off-axis reflector 4.

[0061] The propagation direction of the laser can be changed by the third reflector 32 and the fourth reflector 33 so that the laser can be emitted at a desired location, for example, Figure 5 As shown, the light path exits corresponding to the first detection unit and the third detection unit can be located on the same side, so as to facilitate the operator to obtain the light source 1 and switch the light source 1.

[0062] Embodiment 3

[0063] like Figure 6 As shown, an embodiment of the present application further provides an optical path switching device for an optical detection system, which may include: a first off-axis reflector 2 , a first movable reflector 30 , and a second off-axis reflector 4 .

[0064] The first off-axis reflector 2 is configured to be installed on the light output path of the light source 1 .

[0065] The first movable reflector 30 is configured to be movably mounted on the light output path of the first off-axis reflector 2, and can cut in or out of the light output path of the first off-axis reflector 2, so that the subsequent light path changes between a first cut-in state and a first cut-out state.

[0066] The second off-axis reflector 4 is configured to be installed on the light output path of the light source 1 and not overlap with the light output path of the light source 1 covered by the first off-axis reflector 2 .

[0067] The arrangement direction of the first off-axis reflector 2 and the second off-axis reflector 4 is in a different plane from the incident surface, and the light source 1 (such as a laser) can be located at the focal position of the first off-axis reflector 2 and the second off-axis reflector 4, and the first off-axis reflector 2 and the second off-axis reflector 4 collimate the incident light beam. Figure 6 As shown in (A) in FIG. 1 , when the first movable reflector 30 cuts into the light path of the first off-axis reflector 2 (i.e., in the first cut-in state), the light beam emitted by the light source 1 can be transmitted to the first detection unit after being reflected by the first off-axis reflector 2 and the first movable reflector 30. The light beam emitted by the second off-axis reflector 4 enters the third detection unit. Figure 6 As shown in (B), when the first movable reflector 30 cuts out the light path of the first off-axis reflector 2 (i.e., in the first cut-out state), the light beam emitted by the light source 1 can be transmitted to the second detection unit after being reflected by the first off-axis reflector 2. The light beam emitted by the second off-axis reflector 4 enters the third detection unit. The first detection unit, the second detection unit, and the third detection unit can be selectively connected to subsequent light paths that provide different purposes, and the purposes can be selected from: imaging, wide-spectrum ellipsometer detection, and reflection spectrometer detection.

[0068] In this embodiment, by using a combination of two off-axis reflectors and one movable reflector, three-way light splitting can be achieved, and the light enters the light paths corresponding to different detection units respectively. In other embodiments, the number of off-axis parabolic mirrors can be other values, and the number of movable reflectors can be multiple to perform multi-way beam splitting.

[0069] In some embodiments, Figure 7 As shown, the device may further include a third reflector 32 and a fourth reflector 33. The third reflector 32 is configured to be installed on the light output path of the first off-axis reflector 2 in the first cut-out state, and the fourth reflector 33 is configured to be installed on the light output path of the second off-axis reflector 4.

[0070] like Figure 7 As shown, when the first movable reflector 30 cuts into the light-outgoing optical path of the first off-axis reflector 2, the light beam emitted by the light source 1 can be transmitted to the first detection unit after being reflected by the first off-axis reflector 2 and the first movable reflector 30. The light beam emitted by the second off-axis reflector 4 is reflected by the fourth reflector 33 and enters the third detection unit. When the first movable reflector 30 cuts out of the light-outgoing optical path of the first off-axis reflector 2, the light beam emitted by the light source 1 is reflected by the first off-axis reflector 2, and then reflected by the third reflector 32 and transmitted to the second detection unit.

[0071] In the first cutting state, the light output path of the first movable reflector 30, the light output path of the third reflector 32, and the light output path of the fourth reflector 33 are each selectively connected to subsequent light paths providing different purposes, and the purposes can be selected from: imaging, wide spectrum ellipsometer detection, and reflection spectrometer detection.

[0072] Embodiment 4

[0073] This embodiment further describes the reflector and other optical elements of the optical path switching device based on the above-mentioned embodiments 1 to 3.

[0074] like Figure 7 As shown, in some embodiments, the light source 1 may be a wide-wavelength light source 1 , and the device may further include: at least one filter wheel 50 .

[0075] The filter wheel 50 is configured to filter and provide light of different wavelength ranges, and is arranged on the light output path of the first off-axis reflector 2 and / or the second off-axis reflector 4. The filter wheel 50 may be a double-wheel structure, and may provide light of different wavelength ranges. For example, the laser wavelength may be 100nm to 2500nm, and the filter wheel 50 may provide a wavelength of 200nm to 1000nm or other wavelength bands for SE and SR; and may provide multiple wavelengths such as infrared wavelength, white light, and filter light for imaging.

[0076] For example, a filter wheel 50 can be respectively arranged on the light output path of the first off-axis reflector 2 and the second off-axis reflector 4. The function of the filter wheel 50 is to select or switch the light of a specific wavelength range in the light path to achieve the effects of adjusting the brightness of the light, protecting the detector and shielding interference. The filter wheel 50 is usually composed of a plate with a plurality of holes and a plurality of different filters, and can replace a single filter in the optical system. By rotating the filter wheel 50, different filters can be easily switched to better match the type of light source 1, the experimental object and the measurement needs.

[0077] Further explanation: Wide spectrum ellipsometer is mainly used to measure the optical rotation and linear polarization of polarized light. Its working principle is to determine the optical rotation properties, optical activity, crystal structure and other parameters of the material by measuring the different reflection behaviors of the sample to right-handed and left-handed circularly polarized light. Its measurement frequency is very high and can cover the entire spectrum range from near infrared to ultraviolet, so it can be used to study the structure, composition, morphology and other aspects of the material.

[0078] Reflection spectrometers are mainly used to measure the reflectance spectrum of materials, that is, to measure how the reflectance of the material to the incident light changes with the wavelength of the light. By measuring the reflectance spectrum of the material, the chemical composition, crystal structure, surface morphology, electronic structure and other information of the material can be determined. Compared with the wide-spectrum ellipsometer, the spectral range of the reflection spectrometer is wider, including all visible light from the far infrared band to the ultraviolet band and most of the infrared light. In addition, the reflection spectrometer can also perform high spatial resolution imaging measurement, which is used to characterize the microstructure and morphology of the material surface.

[0079] From the perspective of wavelength range, the measurement range of reflectance spectrometers is usually larger than that of wide-spectrum ellipsometers. Generally speaking, the measurement range of reflectance spectrometers can cover the entire visible spectrum from far infrared to ultraviolet and most of the infrared spectrum, while the measurement range of wide-spectrum ellipsometers is mainly concentrated in the UV-Vis near-infrared region.

[0080] Therefore, the filtering ranges of the two filter wheels 50 on the light output paths of the first off-axis reflector 2 and the second off-axis reflector 4 may be different, and can be set according to the wavelength of the detection light required by the subsequent light path.

[0081] In some embodiments, Figure 7 As shown, the optical path switching device may further include: an aperture assembly 60.

[0082] The aperture assembly 60 is configured to be arranged in the optical path to reduce the divergence angle of the light beam. The aperture assembly 60 reduces the scattering of light by limiting the transmission range of the light during the propagation process. Specifically, the aperture can shield unnecessary light, leaving only the central light beam passing through, limiting its width, thereby reducing the divergence angle of the light beam, shortening the transmission distance of the light beam, and improving the focusing degree and resolution. In practical applications, the aperture is usually in the shape of a circle, a square, a cross, etc., and its aperture and thickness are designed and processed according to specific needs.

[0083] For example, Figure 7 As shown, the aperture assembly 60 can be arranged in front of the light path entrance corresponding to the first detection unit, or at the light path entrance corresponding to other detection units, or in other light paths in the device.

[0084] like Figure 7 As shown, in some embodiments, the first off-axis reflector 2 and / or the second off-axis reflector 4 can be an off-axis parabolic reflector, and the first movable reflector 30 can be an off-axis parabolic reflector or a concave reflector.

[0085] Off-axis reflectors usually refer to parabolic or ellipsoidal reflectors. The shape of this type of reflector is not symmetrical, unlike ordinary plane mirrors or spherical mirrors, which have rotational symmetry. Their reflective surfaces are usually designed to be aspherical in shape so that the incident light is reflected to a position at a certain distance (offset) from the axis of the reflector. Through off-axis reflection, the occlusion and beam scattering caused by passing through the center of the reflector can be avoided, greatly improving the imaging quality and collimation of the beam.

[0086] The mobile reflector is an off-axis parabolic reflector or a concave reflector, and converges the light beam collimated by the off-axis reflector to facilitate the transmission of the subsequent light path.

[0087] In some embodiments, when the device includes the second off-axis reflector 4, the first off-axis reflector 2 and the second off-axis reflector 4 have a common focus, and the light source 1 is arranged at the common focus.

[0088] The off-axis reflector is a non-rotating, asymmetric optical element, and its optical axis does not coincide with the plane mirror surface. Therefore, it is generally impossible to directly use parallel light for illumination, and a spotlight or other light source 1 is required to provide the light source 1. Placing the light source 1 at the focus of the off-axis reflector can make the light reflected from the off-axis reflector more parallel relative to a point light source 1, thereby improving the light focusing effect. This can make the generated light spot clearer, brighter, and smaller in size, which is beneficial to improving the resolution of the system, controlling aberrations, and enhancing the sensitivity of detection and analysis.

[0089] In addition, placing the light source 1 at the focus of the off-axis reflector can also reduce the size of components such as prisms and apertures, because the size of the light beam passing through these components is smaller and more practical.

[0090] In some embodiments, when the device may include a second off-axis reflector 4, the offset angle range between the central optical axis of the incident light path of the first off-axis reflector 2 and the central optical axis of the light beam of the light source 1 may be 10° to 30°, preferably 15°; the offset angle range between the central optical axis of the incident light path of the second off-axis reflector 4 and the central optical axis of the light beam of the light source 1 is 10° to 30°, preferably 15°.

[0091] According to the principle of off-axis parabolic reflection optics, the smaller the angle of the incident light beam, the smaller the angle of the outgoing light beam. Therefore, the shape and size of the off-axis reflector will affect the angle between the incident light beam and the reflected light beam.

[0092] In actual design, the deviation angle range between the central optical axis of the incident light path and the central optical axis of the light beam of light source 1 is generally limited according to the shape and size of the off-axis reflector and the requirements of the optical imaging of the system. In general, this angle range should not be too large to avoid adverse effects such as enlarged light spot and image distortion caused by the deviation of the off-axis reflector.

[0093] In some embodiments, in order to reduce the influence of light interference, the distance between the light source 1 and the first off-axis reflector 2 may range from 2 to 8 centimeters, and the mirror size of the first off-axis reflector 2 may range from 1 to 6 centimeters.

[0094] The interference phenomenon of the reflected light from the off-axis parabola is related to the distance between the light source 1 and the off-axis parabola. When the distance between the light source 1 and the off-axis parabola is close, the angle between the incident light and the reflected light is small, the optical path difference is relatively small, and the interference phenomenon is relatively weak; when the distance between the light source 1 and the off-axis parabola is far, the optical path difference is large, the interference phenomenon is more significant, and because the distance between the off-axis parabola mirror and the laser is too large, it is easy to reduce the light utilization rate.

[0095] Within a certain range, the larger the size of the off-axis parabola, the more significant the interference phenomenon. This is because the different sizes of the off-axis parabola will have different effects on the optical path difference of the reflected light, resulting in different intensities of the interference phenomenon.

[0096] However, when the distance between light source 1 and the off-axis parabola is relatively close, interference may also occur, especially when the size of light source 1 is comparable to that of the off-axis parabola. At this time, the angle between the incident light and the reflected light is small, and the optical path difference is relatively small. However, since the size of light source 1 is comparable to that of the off-axis parabola, it can be considered that the center of light source 1 may not be able to approximately hit the center of the parabola, and a light backscatter effect will occur, making the interference fringes very obvious.

[0097] When the size of the off-axis parabola increases, the change in the incident angle of the light becomes more obvious, resulting in a greater optical path difference and a stronger interference phenomenon. Therefore, when designing an off-axis parabola reflective optical system, it is necessary to choose the appropriate size of the off-axis parabola to reduce or eliminate the influence of the interference phenomenon.

[0098] In the first embodiment, Figure 8 As shown, the divergence angle of the light collected by only a large off-axis parabola to the surface of the object to be measured is too large, and the aperture assembly 60 has a greater limiting effect on the light beam, resulting in a decrease in light utilization. Fig. 9 As shown, in the second and third embodiments, a plurality of small off-axis parabolic mirrors are used to enable the laser to provide light beams to a plurality of detection units simultaneously, thereby enabling simultaneous detection, improving detection efficiency, and also improving light utilization.

[0099] In summary, the optical path switching device provided in the present application can realize the switching of multiple optical paths through the combination of multiple off-axis reflectors, or the combination of off-axis reflectors and movable reflectors, thereby improving the utilization rate of lasers and reducing the cost of detection equipment.

[0100] like Fig.10 As shown, the optical path switching device in the embodiment of the present application can provide laser light for both the SR and imaging optical paths (the "SR light source" in the figure). The switching of the incident optical paths of SR and SE can be achieved by cutting into the plane reflector 4. In this embodiment, the objective lens can be switched to an objective lens of different magnifications by the objective lens switching device, so that the imaging unit forms images of different magnifications of the object to be measured.

[0101] This document is described with reference to various exemplary embodiments. However, those skilled in the art will recognize that changes and modifications may be made to the exemplary embodiments without departing from the scope of this document. For example, various operating steps and components for performing the operating steps may be implemented in different ways (e.g., one or more steps may be deleted, modified, or incorporated into other steps) depending on the specific application or considering any number of cost functions associated with the operation of the system.

[0102] Although the principles of this invention have been shown in various embodiments, many modifications of structures, arrangements, proportions, elements, materials and components particularly suitable for specific environments and operational requirements can be used without departing from the principles and scope of this invention. The above modifications and other changes or amendments will be included in the scope of this invention.

[0103] The foregoing specific description has been described with reference to various embodiments. However, those skilled in the art will recognize that various modifications and changes can be made without departing from the scope of the present disclosure. Therefore, the consideration of the present disclosure will be illustrative rather than restrictive, and all these modifications will be included in its scope. Similarly, the advantages, other advantages and solutions to the problems of various embodiments have been described above. However, the benefits, advantages, solutions to the problems and any elements that can produce these, or make them more clear, should not be interpreted as critical, necessary or necessary. The term "include" and any other variants used in this article are all non-exclusive inclusions, so that the process, method, article or device including the list of elements not only includes these elements, but also includes other elements that are not explicitly listed or do not belong to the process, method, system, article or device. In addition, the term "coupled" and any other variants used in this article refer to physical connections, electrical connections, magnetic connections, optical connections, communication connections, functional connections and / or any other connections.

[0104] Those skilled in the art will appreciate that many changes may be made to the details of the above-described embodiments without departing from the basic principles of the invention. Therefore, the scope of the present invention should be determined solely by the claims.

Claims

1. An optical path switching device for an optical detection system, characterized in that: include: The first off-axis reflector is configured to be installed on the light path of the light source. The second off-axis reflector is configured to be installed on the light output path of the light source and not overlap with the light output path of the light source covered by the first off-axis reflector.

2. The optical path switching device according to claim 1, characterized in that: Also includes: The first movable reflector is configured to be movably mounted on the light output path of the first off-axis reflector, and can cut in or out of the light output path of the first off-axis reflector, so that the subsequent light path changes between a first cut-in state and a first cut-out state.

3. The optical path switching device according to claim 2, characterized in that: Also includes: a third reflector and / or a fourth reflector, The third reflector is configured to be installed on the light output path of the first off-axis reflector in the first cut-out state, The fourth reflector is configured to be installed on the light output path of the second off-axis reflector.

4. The optical path switching device according to claim 3, characterized in that: In the first cutting state, the light output path of the first movable reflector, the light output path of the third reflector, and the light output path of the fourth reflector are each selectively connected to a subsequent light path providing different purposes, and the purposes can be selected from: imaging, wide spectrum ellipsometer detection, and reflection spectrometer detection.

5. The optical path switching device according to claim 1, characterized in that: The light source is a wide wavelength light source, and the device further comprises: At least one filter wheel is configured to filter and provide light of different wavelength ranges, and is arranged on the light output path of the first off-axis reflector and / or the second off-axis reflector.

6. The optical path switching device according to claim 1, characterized in that: Also includes: The aperture assembly is configured to be arranged in the light path to reduce the divergence angle of the light beam.

7. The optical path switching device according to claim 1, characterized in that: The first off-axis reflector and / or the second off-axis reflector are off-axis parabolic reflectors.

8. The optical path switching device according to claim 1, characterized in that: The first off-axis reflector and the second off-axis reflector have a common focus, and the light source is arranged at the common focus. Preferably, the first off-axis reflector and the second off-axis reflector have the same focal length.

9. The optical path switching device according to claim 1, characterized in that: The offset angle range between the central optical axis of the incident light path of the first off-axis reflector and the central optical axis of the light beam of the light source is 10° to 30°, preferably 15°; the offset angle range between the central optical axis of the incident light path of the second off-axis reflector and the central optical axis of the light beam of the light source is 10° to 30°, preferably 15°.

10. The optical path switching device according to claim 1, characterized in that: The distance between the light source and the first and second off-axis reflectors is in the range of 2 to 8 centimeters, and the mirror size of the first and second off-axis reflectors is in the range of 1 to 6 centimeters.

Images