Optical device and optical measurement system

Abstract

An optical device and an optical measurement system wherein the optical device comprises a first lens barrel and a first optical element, a second optical element, a first lens base and a second lens base arranged in the lens barrel, the first optical element is connected with the first lens barrel, the second optical element is arranged on the first lens base, and the first lens base is arranged on the second lens base; the second lens base is connected with the first lens barrel to isolate the first lens barrel from the first lens base and the first optical element, the first lens base and the second lens base have different linear expansion coefficients, and the first lens barrel and the second lens base have the same or similar linear expansion coefficients. By utilizing the difference of linear expansion coefficients among the first lens barrel, the first lens base and the second lens base, temperature drift in opposite directions or different directions can be caused among structural components with different linear expansion coefficients so as to compensate the temperature drift of the second optical element in the axial direction of the first lens barrel relative to the first optical element; therefore, the assembly accuracy of the relative position between the optical elements is effectively improved, and favorable conditions are created for improving the optical focusing precision.

Description

Technical Field

[0001] The present invention relates to the field of optical measurement technology, and in particular to an optical device and an optical measurement system. Background Art

[0002] In existing optical inspection or measurement equipment, in order to obtain a sufficiently clear image of the sample surface, the sample surface is usually automatically focused before image acquisition. Automatic focusing includes image focusing, interference focusing and other methods. Among them, image focusing generally has low focusing accuracy and slow focusing speed, which is suitable for equipment with low precision requirements, while equipment with high precision requirements usually adopts interference focusing methods.

[0003] Taking the interference focusing method as an example, it is necessary to set up a measurement optical path and a reference optical path. In the reference optical path, by adjusting the relative position of the reference reflector and the reference objective lens, better interference fringes can be obtained, which is conducive to improving the effect of interference focusing. However, due to the existence of the linear expansion coefficient of the material, temperature changes can easily cause temperature drift of the reference reflector relative to the focal plane of the reference objective lens, causing the relative position of the reference reflector and the reference objective lens to change, thereby affecting the interference focusing accuracy, causing the equipment to have a series of problems such as blurred image acquisition, reduced detection or measurement accuracy, etc. Summary of the invention

[0004] The main technical problem solved by the present invention is how to improve the focusing accuracy of interferometric focusing by compensating and controlling temperature drift.

[0005] According to a first aspect, an embodiment provides an optical device, comprising: First lens barrel; An optical assembly is arranged in the first lens barrel; the optical assembly includes a first optical element and a second optical element that cooperate with each other, and the first optical element is connected to the first lens barrel; A lens seat assembly, used for carrying the second optical element, so that the second optical element and the first optical element are spaced and opposite to each other in the axial direction of the first lens barrel; the lens seat assembly comprises a first lens seat and a second lens seat arranged in the first lens barrel, the second optical element is arranged on the first lens seat, and the first lens seat is arranged on the second lens seat; the second lens seat is connected to the first lens barrel to isolate the first lens barrel from the first lens seat and the second optical element; Among them, the first lens mount and the second lens mount have different linear expansion coefficients; the first lens barrel and the second lens mount have the same linear expansion coefficient, or the linear expansion coefficient of the first lens barrel is closer to the linear expansion coefficient of the second lens mount than the linear expansion coefficient of the first lens mount.

[0006] In one embodiment, the lens mount assembly further includes a fixing member; the fixing member is cooperatively connected to the first lens mount to fix the second optical element to the first lens mount; wherein: the fixing member and the first lens mount have the same linear expansion coefficient, or the linear expansion coefficient of the fixing member is closer to the linear expansion coefficient of the first lens mount than the linear expansion coefficient of the second lens mount.

[0007] In one embodiment, the first lens seat has a light-transmitting window and a first assembly cavity connected in the axial direction, and the second optical element covers the light-transmitting window and is arranged in the first assembly cavity; the fixing member is arranged in the first assembly cavity and abuts against the side of the second optical element facing away from the light-transmitting window.

[0008] In one embodiment, the first mirror mount has two opposite ends in the axial direction; the second optical element is arranged at one end of the first mirror mount close to the first optical element in the axial direction, and the end of the first mirror mount far away from the first optical element in the axial direction is connected to the second mirror mount to form a span between the connection between the first mirror mount and the second mirror mount and the second optical element.

[0009] In one embodiment, a second assembly cavity is formed inside the second mirror seat, the outer peripheral wall of the second mirror seat and the inner wall surface of the first lens barrel are in contact with each other, and the first mirror seat is inserted into the second assembly cavity; one end of the first mirror seat away from the first optical element in the axial direction is threadedly connected to the first mirror seat so as to be able to adjust the relative position of the second optical element and the second mirror seat in the axial direction.

[0010] In one embodiment, an adjustment assembly is further included, and the adjustment assembly includes: a support member, disposed at an end of the first lens barrel away from the first optical element in the axial direction; an adjusting member, movably connected to the supporting member; the adjusting member is used to drive the second lens mount to drive the first lens mount and the second optical element to move relative to the first optical element along the axial direction; and a positioning member, sleeved on the first lens barrel and fixedly connected to the supporting member; the positioning member and the adjusting member cooperate with each other to fasten the second lens mount in the first lens barrel to fix the relative position of the first optical element and the second optical element in the axial direction.

[0011] In one embodiment, the support member, the adjusting member, the second lens mount and the first lens barrel have the same linear expansion coefficient; or the linear expansion coefficient of at least one of the support member, the adjusting member and the first lens barrel is closer to the linear expansion coefficient of the second lens mount than the linear expansion coefficient of the first lens mount.

[0012] In one embodiment, the linear expansion coefficient of the first lens mount is smaller than the linear expansion coefficient of the second lens mount, and / or the first lens mount, the second lens mount and the first lens barrel are all made of metal materials.

[0013] In one embodiment, the first optical element includes an objective lens, and the second optical element includes a reflector. The objective lens is used to project the incident light beam to the reflector, and the objective lens is also used to collect the light beam reflected by the reflector.

[0014] In one embodiment, the objective lens includes a second lens barrel and a lens group; the lens group is arranged in the second lens barrel and is spaced opposite to the reflector in the axial direction; the second lens barrel is inserted in the first lens barrel and connected to the first lens barrel; wherein the first lens barrel and the second lens barrel have different linear expansion coefficients.

[0015] In one embodiment, the second lens barrel has two opposite ends in the axial direction, and one end of the second lens barrel in the axial direction away from the reflector is threadedly connected to the first lens barrel.

[0016] According to the second aspect, an optical measurement system is provided in an embodiment, comprising a measurement optical path and the optical device described in the first aspect, the measurement optical path comprising an illumination optical path for irradiating a focus light to a device under test, a measurement optical path for the device under test to reflect the focus light, and a reference optical path for the focus light to participate in interference, and the optical device is arranged in the reference optical path.

[0017] The optical device according to the above embodiment includes a first lens barrel and a first optical element, a second optical element, a first lens seat and a second lens seat arranged in the lens barrel, the first optical element is connected to the first lens barrel, the second optical element is arranged on the first lens seat, and the first lens seat is arranged on the second lens seat; the second lens seat is connected to the first lens barrel to isolate the first lens barrel from the first lens seat and the first optical element, the first lens seat and the second lens seat have different linear expansion coefficients, and the first lens barrel and the second lens seat have the same or similar linear expansion coefficients.

[0018] On the one hand, by utilizing the difference in linear expansion coefficients between the first lens barrel, the first lens mount and the second lens mount, temperature drifts in opposite or opposite directions can be caused between structural components with different linear expansion coefficients, and the temperature drift of the second optical element relative to the first optical element in the axial direction of the first lens barrel can be compensated, thereby effectively improving the accuracy of the relative positions between the optical elements and creating favorable conditions for improving the optical focusing accuracy (or focusing accuracy).

[0019] On the other hand, by selecting the linear expansion coefficient of components such as the mirror mount and the mirror barrel, different temperature drift compensation schemes can be formed to meet the actual application needs of the optical device; at the same time, the material selection of components such as the mirror mount and the mirror barrel is more flexible, which is also conducive to controlling the processing cost and weight of the optical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the Linnik-type interferometric focusing detection principle.

[0021] Figure 2 The figure is a schematic diagram of the outer contour structure of an optical device according to an embodiment.

[0022] Figure 3 The figure is a schematic diagram of the cross-sectional structure of an optical device according to an embodiment.

[0023] Figure 4 The figure is a schematic diagram of the span from the second optical element to the second lens holder in an optical device according to an embodiment.

[0024] Figure 5 This is a simulated deformation cloud diagram (I) of the connection between the first mirror mount and the second mirror mount in an optical device of an embodiment.

[0025] Figure 6 This is a simulated deformation cloud diagram (II) of the connection between the first mirror mount and the second mirror mount in an optical device of an embodiment.

[0026] In the figure: 10, first lens barrel; 20, first optical element; 21, second lens barrel; 30, second optical element; 40, first lens holder; 40a, first assembly cavity; 50, second lens holder; 50a, second assembly cavity; 60, fixing member; 70, supporting member; 80, adjusting member; 90, positioning member; A, reference reflector; B, reference objective lens; C, spectrometer; D, measuring objective lens; F, light source; K, camera; M, measured object; L1, illumination optical path; L2, measuring optical path; L3, reference optical path. DETAILED DESCRIPTION

[0027] Wherein similar elements in different embodiments have adopted 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 effortlessly 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, and this is to avoid the core part of the present application from 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.

[0028] 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.

[0029] The serial numbers assigned to the components herein, 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).

[0030] See also Figure 1 Taking the detection or measurement equipment using the Linnik type (also known as Linnik type) interference focusing scheme as an example, the light source F generates an illumination beam (such as a focus detection light of a certain wavelength), which reaches the beam splitter C through the illumination optical path L1 and is divided into two beams. One beam enters the reference optical path L3 between the beam splitter C and the reference reflector A, and the other beam enters the measurement optical path L2 between the beam splitter C and the object to be measured M. In the process of automatic focusing, it is necessary to adjust the focal plane from the reference reflector A to the reference objective lens B, and adjust the distance from the reference objective lens B to the beam splitter C and the distance from the measurement objective lens D to the beam splitter C so that the distances are equal; when the surface of the object to be measured M is located at the focal plane position of the measurement objective lens D, the interference light with the strongest light intensity will be generated and captured by the camera K. By controlling the optical machine to move up and down in the vertical direction (or Z direction), a focusing curve for the object to be measured M will be formed. According to this focusing curve, the focusing position can be finally determined (for example, calculated by an algorithm), that is, the position of the object to be measured M relative to the front focal plane of the measurement objective lens D.

[0031] However, in the actual application of detection or measurement equipment, even if the most accurate temperature control system available is configured, it is impossible to guarantee that the ambient temperature remains absolutely unchanged; therefore, when the ambient temperature changes, due to the existence of the linear expansion coefficient of the material, it is very easy to cause the temperature drift of the reference reflector relative to the focal plane of the reference objective lens, thereby causing the relative position between the reference objective lens B and the reference reflector A to change; when the position of the reference reflector A relative to the focal plane of the reference objective lens B is shifted, it will affect the focusing curve, and the determined focusing position will not be the position with the clearest image, thereby causing problems such as blurred image acquisition and reduced detection or measurement accuracy.

[0032] In the optical device provided by the present application, a mirror seat for loading a second optical element (such as a reference reflector) is split into a first mirror seat and a second mirror seat, the second optical element is loaded by the first mirror seat, and a structural connection relationship is established between the first mirror seat and a first lens barrel for loading the first optical element (such as a reference objective lens) by the second mirror seat; wherein the second mirror seat and the first lens barrel are made of materials with the same or similar linear expansion coefficients, and the first mirror seat is made of materials with a higher or lower linear expansion coefficient than the second mirror seat; in this way, the temperature drifts generated by the first optical element and the second optical element in the axial direction of the first lens barrel can be compensated and controlled by utilizing the directional or diametric temperature drifts formed between structural components with different linear expansion coefficients, so as to minimize or even avoid the change in the relative position of the first optical element and the second optical element, thereby facilitating the ensuring of focusing accuracy and providing support for improving the optical focusing accuracy.

[0033] See also Figures 2 to 3 Combined with Figure 1 An optical device provided in an embodiment of the present application includes a first lens barrel 10, an optical component, a lens seat assembly, and other functional components that exist as needed; wherein the optical component includes a first optical element 20 and a second optical element 30 that cooperate with each other, and the lens seat assembly includes a first lens seat 40 and a second lens seat 50.

[0034] The following mainly describes the structural architecture, implementation principle, etc. of the optical device by taking the optical device used to realize interferometric focusing or interferometric measurement of an optical measurement system as an example; that is, the optical device is arranged in the reference optical path of the optical measurement system, the first optical element 20 includes an objective lens (equivalent to a reference objective lens), the second optical element 30 includes a reflector (equivalent to a reference reflector), the objective lens is used to project the light beam separated by the beam splitter to the reflector, and is also used to collect the light beam reflected by the reflector and project it to the beam splitter, so that the light beam provided by the optical device can participate in interference.

[0035] However, it should be noted that the optical device can also be used to realize other functions of the optical measurement system, or be arranged in other optical paths such as the imaging optical path and the illumination optical path of the optical measurement system; it can be understood that the first optical element 20 and the second optical element 30 can be adaptively adjusted to other optical elements.

[0036] See also Figure 2 and Figure 3 , a first optical element 20 (specifically, an objective lens), a second optical element 30 (specifically, a reflector), a first lens seat 40 and a second lens seat 50 are all arranged inside the first lens barrel 10; wherein, the first optical element 20 and the second optical element 30 are arranged opposite to each other in the axial direction of the first lens barrel 10, and the first optical element 20 is connected to the first lens barrel 10, for example, the outer wall of the objective lens barrel is threadedly connected to the inner wall of the first lens barrel 10; the second optical element 30 is arranged on the first lens seat 40, for example, the reflector is detachably fixed on the first lens seat 40 in the form of being opposite to the objective lens in the axial direction of the first lens barrel 10; the first lens seat 40 is arranged on the second lens seat 50, for example, the first lens seat 40 is threadedly connected to the second lens seat 50; the second lens seat 50 is connected to the first lens barrel 10, for example, the second lens seat 50 is slidably connected to the inner wall of the first lens barrel 10.

[0037] Among them, the first lens mount 40 and the second lens mount 50 have different linear expansion coefficients, while the first lens barrel 10 and the second lens mount 50 have the same or similar linear expansion coefficients, that is, the linear expansion coefficient of the first lens barrel 10 is closer to the linear expansion coefficient of the second lens mount 50 than the linear expansion coefficient of the first lens mount 40; for example, the first lens barrel 10 and the second lens mount 50 can be made of materials with relatively close linear expansion coefficients such as copper and stainless steel, and the first lens mount 40 can be made of materials such as aluminum alloy, indium steel, and ordinary steel.

[0038] Therefore, by splitting the lens base supporting the second optical element 30 into the first lens base 40 and the second lens base 50, the first lens barrel 10 (together with the first optical element 20) and the first lens base 40 (together with the second optical element 30) are structurally isolated by the second lens base 50, thereby avoiding direct contact and connection between the first lens base 40 and the first lens barrel 10.

[0039] On the one hand, since the first lens barrel 10 and the second lens holder 50 are made of materials with the same or similar linear expansion coefficients, the temperature drift difference introduced between the first optical element 20 and the second optical element 30 in the axial direction can be reduced as much as possible when the temperature changes; and since the first lens holder 40 is made of a material with a linear expansion coefficient that is significantly higher or lower than that of the second lens holder 50, the difference in the linear expansion coefficients of the first lens holder 40 and the second lens holder 50 can be used to generate temperature drifts in opposite or different directions at the span from the second optical element 30 to the connection between the first lens holder 40 and the second lens holder 50, so as to compensate and control the temperature drift generated in the axial direction between the first optical element 20 and the second optical element 30; in this way, the offset of the relative position between the first optical element 20 and the second optical element 30 can be effectively reduced, and even the change in the relative position of the first optical element 20 and the second optical element 30 caused by the influence of temperature can be avoided, thereby ensuring the position accuracy between the optical elements and providing support for improving the optical focusing accuracy.

[0040] On the other hand, by selecting the linear expansion coefficients of the first lens mount 40, the first lens barrel 10, the second lens mount 50 and other related components, different temperature drift compensation and control schemes can be combined to meet the actual application needs of the optical device; and the materials of the related structural components can be flexibly selected according to needs or requirements, which is beneficial to control the production cost, application cost, weight, etc. of the optical device.

[0041] In the prior art, the more common interference measurement mechanism usually includes a lens barrel, a reference objective lens, a reference reflector, a reflector seat made of aluminum alloy, etc., and the reference objective lens, the reference reflector and the reflector seat are all arranged in the lens barrel; wherein the reference objective lens and the reflector seat are respectively connected to the lens barrel, and the reference reflector is fixed to the reflector seat (it can be understood that the reflector seat of the existing interference measurement mechanism is equivalent to the first lens seat 40 or the second lens seat 50 of the optical device in the embodiment of the present application).

[0042] Taking the axial length of the reference objective lens as 44 mm and the distance between the reference objective lens and the reference reflector as 0.95 mm as an example, according to the linear expansion coefficient of copper being 1.7*10 -5 / ℃, the linear expansion coefficient of aluminum alloy is 2.3*10 -5 / ℃: Under a temperature change of 1.0℃, the temperature drift of the reference objective lens and the reference reflector is (2.3-1.7)*10 -5 *44*1+2.3*10 -5 *0.95*1=285.85nm; obviously, the temperature drift of 285.85nm has far exceeded the focusing accuracy requirement.

[0043] If the linear expansion coefficient is taken into consideration, the reflector seat is made of copper material with the same linear expansion coefficient as the lens barrel. Under a temperature change of 1.0℃, the temperature drift of the reference objective lens and the reference reflector is 1.7*10 -5 *0.95*1=16.15nm, but because the reference objective lens has an axial length of 44mm, temperature changes can easily cause the reference objective lens to become defocused due to deformation and displacement between internal lenses, and because the temperature drift between the reference objective lens and the reference reflector cannot be compensated and controlled, the focusing accuracy is also uncontrollable.

[0044] In comparison, in the optical device provided in the embodiment of the present application, by splitting the lens holder supporting the second optical element 30 into a first lens holder 40 and a second lens holder 50 having different linear expansion coefficients, it is possible to compensate and control the temperature drift between the first optical element 20 and the second optical element 30, and form different temperature drift compensation and control schemes.

[0045] For example, without considering the deformation and displacement of the internal lenses of the first optical element 20 (specifically, the objective lens) due to temperature change, which may cause defocusing; When the first lens barrel 10 and the second lens holder 50 are both made of copper, the temperature drift of the first optical element 20 and the second optical element 30 is 1.7*10 -5 *0.95*1=16.15nm; When the first lens barrel 10 is made of copper and the second lens holder 50 is made of stainless steel, the linear expansion coefficient of stainless steel is 1.65*10 -5 / ℃, it can be seen that the temperature drift of the first optical element 20 and the second optical element 30 is (1.65-1.7)*10 -5 *44*1+1.65*10 -5 *0.95*1=-6.32nm.

[0046] The span from the second optical element 30 to the connection between the first lens holder 40 and the second lens holder 50 is XX mm (it can be understood that the span XX is a variable determined according to needs or requirements).

[0047] When the first lens holder 40 is made of aluminum alloy and the second lens holder 50 is made of copper, the temperature drift compensation amount under a temperature change of 1.0°C is: (2.3-1.7)*10 -5 *XX*1=(6*XX)nm.

[0048] When the first lens holder 40 is made of aluminum alloy and the second lens holder 50 is made of stainless steel, the temperature drift compensation amount under a temperature change of 1.0°C is: (2.3-1.65)*10 -5 *XX*1=(6.5*XX)nm.

[0049] When the first mirror base 40 is made of ordinary steel and the second mirror base 50 is made of copper, according to the linear expansion coefficient of ordinary steel being 1.2*10 -5 / ℃, the temperature drift compensation under a temperature change of 1.0℃ is: (1.2-1.7)*10 -5 *XX*1=(-0.5*XX)nm.

[0050] When the first mirror base 40 is made of ordinary steel and the second mirror base 50 is made of stainless steel, the temperature drift compensation amount under a temperature change of 1.0°C is: (1.2-1.65)*10 -5 *XX*1=(-4.5*XX)nm.

[0051] When the first lens holder 40 is made of indium steel and the second lens holder 50 is made of copper, the linear expansion coefficient of indium steel is 0.15*10 -5 / ℃, the temperature drift compensation under a temperature change of 1.0℃ is: (0.15-1.7)*10 -5 *XX*1=(-15.5*XX)nm.

[0052] When the first mirror base 40 is made of indium steel and the second mirror base 50 is made of stainless steel, the temperature drift compensation amount under a temperature change of 1.0°C is: (0.15-1.65)*10 -5 *XX*1=(-15*XX)nm.

[0053] In summary, it can be seen that in the optical device provided in the embodiment of the present application, based on the set first lens holder 40 and the second lens holder 50, by selecting the materials or linear expansion coefficients of the first lens barrel 10, the first lens holder 40 and the second lens holder 50, and selecting and determining the span from the second optical element 30 to the connection between the first lens holder 40 and the second lens holder 50, different temperature drift compensation control schemes can be formed in combination according to the application requirements of the optical device, thereby effectively improving the assembly accuracy of the relative position of the first optical element 20 and the second optical element 30, reducing or even avoiding changes in the relative position between the two, thereby providing support for improving focusing accuracy, etc.

[0054] In one embodiment, see Figure 3 and Figure 4The first lens holder 40 has two opposite ends in the axial direction of the first lens barrel 10, the second optical element 30 is arranged at one end of the first lens holder 40 close to the first optical element 20 in the axial direction, and the first lens holder 40 is connected to the second lens holder 50 at one end far away from the first optical element 20 in the axial direction. By arranging the second optical element 30 and the connection between the first lens holder 40 and the second lens holder 50 at the opposite ends of the first lens holder 40, a certain span d can be formed between the connection between the first lens holder 40 and the second lens holder 50 and the second optical element 30 (for example, the reflecting surface of the reflecting mirror), so that the compensation and control of the temperature drift between the first optical element 20 and the second optical element 30 can be achieved by selecting and setting the span and matching the difference in linear expansion coefficients between related components.

[0055] For example, see Figure 3 A second assembly cavity 50a is formed inside the second lens holder 50, the outer peripheral wall of the second lens holder 50 and the inner wall surface (i.e., the inner wall of the tube) of the first lens barrel 10 are in contact with each other, and the first lens holder 40 is inserted into the second assembly cavity 50a; wherein, the first lens holder 40 is threadedly connected to the second lens holder 50 at one end away from the first optical element 20 in the axial direction of the first lens barrel 10, that is, the outer peripheral surface of the first lens holder 40 is provided with an external thread structure, and the second lens holder 50 is provided with an internal thread structure in the second assembly cavity 50a.

[0056] In this way, by utilizing the threaded connection relationship between the first lens mount 40 and the second lens mount 50, the relative position of the second optical element 30 and the second lens mount 50 in the axial direction can be adjusted, so that the span d can be selected and determined according to the application requirements of the optical device and the linear expansion coefficients of each component, thereby forming a suitable temperature drift compensation control scheme.

[0057] In one embodiment, see Figure 3 The lens seat assembly also includes a fixing member 60, which is connected to the first lens seat 40 to restrict and fix the second optical element 30 on the first lens seat 40; the fixing member 60 and the first lens seat 30 have the same or similar linear expansion coefficient, that is, the fixing member 60 and the first lens seat 40 are made of the same or similar material, or the linear expansion coefficient of the fixing member 60 is closer to the linear expansion coefficient of the first lens seat 40 than the linear expansion coefficient of the second lens seat 50 (and the first lens barrel 10); for example, the first lens seat 30 and the fixing member 60 are both made of stainless steel.

[0058] Exemplarily, the fixing member 60 may be a structural member such as a clamp, a C-shaped clamp ring, etc. The first lens holder 40 is connected to the light-transmitting window and the first assembly cavity 40a in the axial direction of the first lens barrel 10, and the second optical element 30 (such as a reflector) covers the light-transmitting window and is arranged in the first assembly cavity 40a; and the fixing member 60 is disposed in the first assembly cavity 40a and abuts against the side of the second optical element 30 facing away from the light-transmitting window to clamp the second optical element 30 between the fixing member 60 and the first lens holder 40.

[0059] Thus, the second optical element 30 can be restrained and fixed inside the first lens holder 40 in a detachable manner by means of the fixing member 60, and an optical path connection relationship can be established between the first optical element 20 and the second optical element 30 by means of the light-transmitting window. For example, a light beam passing through the objective lens can be projected to the reflector through the light-transmitting window, and a light beam reflected by the reflector can be projected to the objective lens through the light-transmitting window. Based on the characteristic that the fixing member 60 and the first lens holder 40 have the same or similar linear expansion coefficient, the influence of temperature changes on the relative position of the second optical element 30 and the first lens holder 40 can be reduced or eliminated, thereby stabilizing the position and assembly accuracy of the second optical element 30 on the first lens holder 40.

[0060] In some embodiments, the first lens holder 40 and the fixing member 60 are made of materials having a linear expansion coefficient smaller than that of the second lens holder 50 (together with the first lens barrel 10 ), so as to minimize the influence of the deformation of the first lens holder 40 or the fixing member 60 itself on the position of the second optical element 30 .

[0061] In one embodiment, see Figure 2 and Figure 3 The optical device also includes an adjustment component, which is mainly used to drive the second optical element 30, the first lens holder 40 and the second lens holder 50 to move closer to or away from the first optical element 20 in the first lens barrel 10, so as to achieve the purpose of adjusting and positioning the relative positions of the first optical element 20 and the second optical element 30 in the axial direction of the first lens barrel 10.

[0062] The adjustment assembly includes a support member 70, an adjustment member 80 and a positioning member 90; wherein the support member 70 is arranged at one end of the first lens barrel 10 away from the first optical element 20 in the axial direction; the adjustment member 80 is movably connected to the support member 70, and is used to drive the second lens holder 50 to drive the first lens holder 40 (together with the second optical element 30, the fixing member 60, etc.) to move relative to the first optical element 20 along the axial direction of the first lens barrel 10, so as to adjust the spacing between the first optical element 20 and the second optical element 30; the positioning member 90 is sleeved on the outer periphery of the first lens barrel 10 and fixedly connected to the support member 70, and is mainly used to cooperate with the adjustment member 80 to lock the second lens holder 50 inside the first lens barrel 10, so as to fix the relative position or spacing between the first optical element 20 and the second optical element 30 in the axial direction.

[0063] Exemplarily, a plurality of deformation seams extending in the axial direction are provided on the barrel wall of the first lens barrel 10 at one end axially away from the first optical element 20, and the support member 70 has an end cover portion arranged axially facing the second lens holder 50 and a sleeve portion sleeved on the outer periphery of the first lens barrel 10; the positioning member 90 can be a clamp structure, a strap structure, etc. fixed to the end of the sleeve portion away from the end cover portion; and the adjusting member 80 can be a screw structure, a micrometer structure, etc. that passes through and is screwed to the end cover portion.

[0064] In this way, the second lens holder 50 can be pushed and pulled to move axially in the first lens barrel 10 by rotating the adjusting member 80. When the second lens holder 50 is adjusted to a preset position, the supporting member 70 and the first lens barrel 10 can be locked and fixed by the positioning member 90, so that the first lens barrel 10 can clamp the second lens holder 50 due to the contraction of the deformation joint, thereby locking the position of the second lens holder 50; conversely, the restraining force on the first lens barrel 10 can be released by the positioning member 70, so that the first lens barrel 10 can loosen the second lens holder 50 due to the expansion of the deformation joint, so as to adjust the position of the second lens holder 50 or disassemble and assemble the second lens holder 50 (together with the first lens holder 40, the second optical element 30 and other components).

[0065] Of course, the adjustment component may also adopt other suitable structures as long as it can achieve the position adjustment and positioning of the second lens holder 50, which will not be elaborated here.

[0066] In some embodiments, the support member 70, the adjustment member 80, the positioning member 90, etc. have the same or similar linear expansion coefficient as the second lens holder 50 (or the first lens barrel 10), that is, the linear expansion coefficient of at least one of the support member 70, the adjustment member 80 and the positioning member 90 is closer to the linear expansion coefficient of the second lens holder 50 than the linear expansion coefficient of the first lens holder 40; for example, the adjustment assembly, the second lens holder 50 and the first lens barrel 10 are all made of copper or stainless steel. In this way, since the second lens holder 50, the first lens barrel 10, the adjustment assembly, etc., which are in direct contact connection, have the same or similar linear expansion coefficient, the temperature drift difference introduced between the first optical element 20 and the second optical element 30 in the axial direction can be reduced as much as possible, providing support for effective temperature drift compensation control.

[0067] In one embodiment, see Figure 3The optical device is configured to be applicable to an optical measurement system using interference focusing, wherein the first optical element 20 includes an objective lens, and the second optical element 30 includes a reflector; wherein the objective lens includes a second lens barrel 21 and a lens group (not shown in the figure) disposed in the second lens barrel 21, and the lens group is spaced and opposed to the reflector in the axial direction of the first lens barrel 10; the second lens barrel 21 is inserted into the interior of the first lens barrel 10 and connected to the first lens barrel 10, for example, the second lens barrel 21 has two ends opposite to each other in the axial direction, and one end of the second lens barrel 21 away from the reflector in the axial direction is threadedly connected to the first lens barrel 10, so that the axial spacing between the reflector and the lens group can be adjusted by rotating the second lens barrel 21.

[0068] More specifically, the second lens barrel 21 and the first lens barrel 10 have different linear expansion coefficients, for example, the linear expansion coefficient of the second lens barrel 21 is significantly higher or lower than the linear expansion coefficient of the first lens barrel 10. In this way, by utilizing the difference in linear expansion coefficients between the second lens barrel 21 and the second lens barrel 10, temperature drifts in opposite or different directions can be caused at the connection between the two due to different expansion degrees, thereby forming temperature drift compensation and control for the axial spacing between the reflector and the lens group.

[0069] In addition, as mentioned above, components with different linear expansion coefficients may drift in opposite or different directions at their connections (such as the connection between the first lens holder 40 and the second lens holder 50, and the connection between the first lens barrel 10 and the second lens barrel 21) due to their different expansion degrees.

[0070] Exemplarily, the first mirror base 40 is made of aluminum alloy material, and the second mirror base 50 is made of copper material. The relative deformation from the connection between the first mirror base 40 and the second mirror base 50 to the second optical element 30 (for example, the reflecting surface of the reflecting mirror) is 138nm, and the relative deformation from the first mirror base 40 to the second mirror base 50 is 171nm. Figure 5 It can be seen from the deformation cloud map that the local connection is arched forward in different directions, increasing the deformation.

[0071] For example, the first mirror base 40 is made of ordinary steel material, and the second mirror base 50 is made of copper material. The relative deformation from the connection between the first mirror base 40 and the second mirror base 50 to the second optical element 30 (for example, the reflecting surface of the reflecting mirror) is 72nm. Figure 6 It can be seen from the deformation cloud map that the local connection is pulled backward in the same direction, reducing the deformation.

[0072] Therefore, based on the phenomenon that the joints of materials with different linear expansion coefficients are prone to drift deformation in opposite directions or in different directions, this phenomenon can be combined and applied to optical devices or optical measurement systems to achieve temperature drift compensation and control; it can be understood that in some scenarios where precise temperature drift compensation and control are required, the specific structural architecture, materials, dimensional parameters, etc. of the optical device can be designed in combination with existing means such as calculation, simulation or experiment.

[0073] See also Figures 1 to 6 An embodiment of the present application further provides an optical measurement system, comprising a measurement optical path and an optical device provided by any of the aforementioned embodiments; the measurement optical path may include an illumination optical path in which a focus light is irradiated on an object to be measured, a measurement optical path in which the focus light is reflected by the object to be measured, and a reference optical path in which the focus light participates in interference; that is, the optical device may be arranged in the reference optical path.

[0074] For example, see Figure 1 , provides a schematic diagram of the optical structure of the optical measurement system, where the light source F generates a focus detection light of a certain wavelength, the emitted focus detection light can be transmitted along the illumination optical path L1, and can be optically shaped during the transmission process. The focus detection light is split into a beam by the spectroscope C and enters the measurement optical path L2, passes through the measuring objective lens D, and finally irradiates the measured object M placed on the supporting platform. The measured object M reflects the focus detection light (i.e., the measurement reflected light) and is transmitted along the measurement optical path L2, passes through the measuring objective lens D, and reaches the spectroscope C.

[0075] The focus detection light is separated by the beam splitter C into another beam that enters the reference optical path L3, passes through the reference objective lens B and irradiates the reference reflector A. The reference reflector A reflects the focus detection light (i.e., the reference reflected light) and transmits it along the reference optical path L3, passes through the reference objective lens B and reaches the beam splitter C. The reference objective lens B and the reference reflector A are integrated into a relatively complete functional structure through the first lens barrel 10, the first lens holder 40, and the second lens holder 50, which is the optical device of the aforementioned embodiment.

[0076] The measured reflected light and the reference reflected light that reach the beam splitter C undergo optical interference, and the interference light is transmitted forward to the camera K. During the transmission process, it may undergo optional processing processes such as optical relay, optical deflection, and optical imaging. The interference image is obtained by the camera K. By analyzing the interference image, the focusing curve can be obtained to know the focusing state of the test piece M before the measuring objective lens D, such as the defocus direction and defocus amount.

[0077] It can be understood that the optical measurement system provided here can be used as a functional module of an optical inspection device or an optical measurement device, the purpose of which is to measure the focusing state of the test piece (such as a wafer), so as to cooperate with other displacement actuators to adjust the test piece to a focusing position, that is, to be located in the focal plane of the measuring objective lens and in a focused state. Of course, the optical inspection or optical measurement equipment can also have other lighting modules and imaging modules, which can share part of the optical path with the optical measurement system provided here, and can achieve clear microscopic imaging of any area on the surface of the test piece by illuminating and imaging the test piece in a focused state, which is convenient for defect detection, morphological parameter measurement or overlay alignment measurement of features in any area.

[0078] Based on the technical effects of the optical device (such as temperature drift compensation and control), the optical measurement system having the optical device should also have the same technical effects; therefore, it will not be elaborated here.

[0079] The above specific examples are used to illustrate the present invention, which is only used to help understand the present invention and is not intended to limit the present invention. For those skilled in the art, according to the concept of the present invention, some simple deductions, modifications or substitutions can be made.

Claims

1. An optical device, characterized in that: include: First lens barrel; An optical component, arranged in the first lens barrel; The optical assembly comprises a first optical element and a second optical element that cooperate with each other, and the first optical element is connected to the first lens barrel; A lens seat assembly, used for carrying the second optical element, so that the second optical element and the first optical element are spaced and opposite to each other in the axial direction of the first lens barrel; the lens seat assembly comprises a first lens seat and a second lens seat arranged in the first lens barrel, the second optical element is arranged on the first lens seat, and the first lens seat is arranged on the second lens seat; the second lens seat is connected to the first lens barrel to isolate the first lens barrel from the first lens seat and the second optical element; Among them, the first lens mount and the second lens mount have different linear expansion coefficients; the first lens barrel and the second lens mount have the same linear expansion coefficient, or the linear expansion coefficient of the first lens barrel is closer to the linear expansion coefficient of the second lens mount than the linear expansion coefficient of the first lens mount.

2. The optical device according to claim 1, characterized in that The mirror base assembly further includes a fixing member; the fixing member is connected with the first mirror base in cooperation with the first mirror base to fix the second optical element to the first mirror base; wherein: The fixing member and the first lens mount have the same linear expansion coefficient, or the linear expansion coefficient of the fixing member is closer to the linear expansion coefficient of the first lens mount than the linear expansion coefficient of the second lens mount.

3. The optical device according to claim 2, characterized in that The first lens seat has a light-transmitting window and a first assembly cavity connected in the axial direction, the second optical element covers the light-transmitting window and is arranged in the first assembly cavity; the fixing member is arranged in the first assembly cavity and abuts against the side of the second optical element facing away from the light-transmitting window.

4. The optical device according to claim 1, wherein The first mirror mount has two opposite ends in the axial direction; the second optical element is arranged at one end of the first mirror mount close to the first optical element in the axial direction, and the end of the first mirror mount far away from the first optical element in the axial direction is connected to the second mirror mount to form a span between the connection between the first mirror mount and the second mirror mount and the second optical element.

5. The optical device according to claim 4, characterized in that A second assembly cavity is formed inside the second mirror seat, the outer peripheral wall of the second mirror seat abuts against the inner wall surface of the first lens barrel, and the first mirror seat is inserted into the second assembly cavity; one end of the first mirror seat away from the first optical element in the axial direction is threadedly connected to the first mirror seat so as to be able to adjust the relative position of the second optical element and the second mirror seat in the axial direction.

6. The optical device according to claim 1, wherein: Also included is an adjustment component, the adjustment component comprising: A support member, disposed at one end of the first lens barrel in the axial direction away from the first optical element; an adjusting member, movably connected to the supporting member; the adjusting member is used to drive the second lens holder to drive the first lens holder and the second optical element to move relative to the first optical element along the axial direction; and A positioning member is sleeved on the first lens barrel and fixedly connected to the supporting member; the positioning member cooperates with the adjusting member to fasten the second lens holder in the first lens barrel to fix the relative position of the first optical element and the second optical element in the axial direction.

7. The optical device according to claim 6, characterized in that The support member, the adjusting member, the second lens mount and the first lens barrel have the same linear expansion coefficient; or the linear expansion coefficient of at least one of the support member, the adjusting member and the first lens barrel is closer to the linear expansion coefficient of the second lens mount than the linear expansion coefficient of the first lens mount.

8. The optical device according to any one of claims 1 to 7, characterized in that: The linear expansion coefficient of the first lens mount is smaller than the linear expansion coefficient of the second lens mount, and / or the first lens mount, the second lens mount and the first lens barrel are all made of metal materials.

9. The optical device according to any one of claims 1 to 7, characterized in that: The first optical element includes an objective lens, and the second optical element includes a reflector. The objective lens is used to project an incident light beam to the reflector, and the objective lens is also used to collect the light beam reflected by the reflector.

10. The optical device according to claim 9, characterized in that The objective lens includes a second lens barrel and a lens group; the lens group is arranged in the second lens barrel and is spaced opposite to the reflector in the axial direction; the second lens barrel is inserted in the first lens barrel and connected to the first lens barrel; wherein the first lens barrel and the second lens barrel have different linear expansion coefficients.

11. The optical device according to claim 10, characterized in that The second lens barrel has two opposite ends in the axial direction, and one end of the second lens barrel in the axial direction away from the reflecting mirror is threadedly connected to the first lens barrel.

12. An optical measurement system, characterized in that: comprising a measuring optical path and an optical device as claimed in any one of claims 1 to 11; The measuring optical path includes an illumination optical path for irradiating the focus light to the measured object, a measuring optical path for the measured object to reflect the focus light, and a reference optical path for the focus light to interfere. The optical device is arranged in the reference optical path.

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