scale

Abstract

A scale device for a measurement encoder, the scale device including a scale (202) and a thermal displacement elimination structure (212). The thermal displacement elimination structure (212) includes an intermediate member (206) and a first thermal displacement elimination layer (204) for attaching the scale (202) to the intermediate member (206). The thermal expansion coefficients of the intermediate member (206) and the scale (202) satisfy the following: -3×10 -6 K -1 ≦CTE(intermediate material)-CTE(scale)≦6×10 -6 K -1 .

Description

[Technical Field]

[0001] The present invention relates to scales, and more particularly to metrological scales for use as part of measurement encoders. [Background technology]

[0002] Metrological scales are used to measure the position of a moving part of a machine relative to a fixed part. A metrological scale typically has a series of features that can be read by a readhead, which then provides a measurement of its position along the scale. A metrological scale can be attached to either the fixed or moving part of a machine and is read by a suitable readhead attached to the other of the fixed or moving part. Types of metrological scales include magnetic scales (where the scale features are provided by features with specific magnetic properties), capacitive scales (where the features are provided by features with specific capacitance properties), and optical scales (where the features are provided by features with specific optical properties). Optical scales can be transmissive or reflective. Examples of optical scale devices are disclosed in U.S. Patent Nos. 5,629,995 and 5,729,995.

[0003] It is known to attach metrological scales to components using adhesives. The substrate to which the metrological scale is attached and the metrological scale typically have different thermal expansion characteristics. One known method of attaching a scale to a substrate is to form the scale on the substrate. In such a method, the scale is fixed to the substrate such that the expansion and contraction of the scale is determined by the expansion and contraction of the substrate. That is, the scale is attached such that the expansion and contraction (e.g., thermal expansion) of the substrate is transferred to the scale as much as possible.

[0004] In US Patent No. 5,649,299, a metrological scale is supported on a substrate by a scale track. The track disclosed allows the metrological scale to expand and contract due to changes in temperature substantially independent of the substrate.

[0005] Patent Document 4 discloses a configuration that aims to prevent a decrease in position detection accuracy due to thermal expansion of the substrate by attaching the main scale to a mounting member using an elastic material that reduces in volume when hardened but maintains its elasticity even after hardening.

[0006] Patent Document 5 discloses a glass epoxy substrate scale attached to a metal tape with a thin layer of a strong adhesive such as an epoxy-type adhesive so that the thermal expansion characteristics of the scale are dominated by the metal tape. The metal tape is attached to the substrate via a thermal displacement elimination structure. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] European Patent Publication No. 0207121 [Patent Document 2] U.S. Patent No. 4,974,962 [Patent Document 3] International Publication No. 2010 / 004248 [Patent Document 4] Japanese Patent Application Publication No. 05-269650 [Patent Document 5] U.S. Patent No. 7,007,397 Summary of the Invention

[0008] According to a first aspect of the present invention, there is provided a scale device for a measurement encoder, the scale device including a scale and a thermal displacement elimination structure, the thermal displacement elimination structure including an intermediate member, a first thermal displacement elimination layer, and a second thermal displacement elimination layer, the first thermal displacement elimination layer is for attaching the scale to the intermediate member, and the thermal expansion coefficients of the intermediate member and the scale are -3×10 -6 K -1 ≦CTE(intermediate material)-CTE(scale)≦6×10 -6 K -1 .

[0009] By providing such a scale device, the effects of the thermal expansion behavior of the substrate on which the scale device may be placed may be reduced, thereby improving the behavior of the scale during temperature changes.

[0010] Optionally, the thermal expansion coefficient of the intermediate member and scale is -2×10 -6 K -1 ≦CTE(intermediate material)-CTE(scale)≦×10 -6 K -1 , optionally, -2×10 -6 K -1 ≦CTE(intermediate material)-CTE(scale)≦1.6×10 -6 K -1 , for example: -1×10 -6 K -1 ≦CTE(intermediate material)-CTE(scale)≦1×10 -6 K -1 Optionally, the thermal expansion coefficient of the intermediate member and the scale is -0.2 x 10 -6 K -1 ≦CTE(intermediate material)-CTE(scale)≦0.2×10 -6 K -1 Optionally, the thermal displacement elimination structure is for attaching the scale to the substrate. Optionally, the thermal expansion coefficient of the intermediate member is an intrinsic thermal expansion coefficient of a material that the intermediate member comprises. Optionally, the thermal expansion coefficient of the scale is an intrinsic thermal expansion coefficient of a material that the scale comprises.

[0011] Optionally, the second thermal displacement eliminator layer is for attaching the scale to a substrate, for example, via an intermediate member. Optionally, the second thermal displacement eliminator layer is for attaching the intermediate member to a substrate.

[0012] Optionally, the first and / or second thermal displacement elimination layers exhibit an elastic response, e.g., an elastic response to shear, which may be caused by thermal expansion, e.g., in the case of the first thermal displacement elimination layer, of the scale and / or the intermediate member. Optionally, the first and / or second thermal displacement elimination layers are elastically deformable. Optionally, the first thermal displacement elimination layer bonds the scale to the intermediate member. Optionally, the scale is fixed to the intermediate member by the first thermal displacement elimination layer. Optionally, the first and / or second thermal displacement elimination layers comprise adhesive tape. Optionally, the first and / or second thermal displacement elimination layers resist lateral movement of the scale and / or the intermediate member, e.g., the first thermal displacement elimination layer may resist lateral movement of the scale relative to the intermediate member, which may include lateral movement of the scale relative to the intermediate member in a direction orthogonal to both the measurement direction of the scale and a direction perpendicular to the measurement surface of the scale. Optionally, the first thermal displacement elimination layer and the second thermal displacement elimination layer have the same thickness. Alternatively, the first thermal displacement elimination layer and the second thermal displacement elimination layer have different thicknesses, for example, the second thermal displacement elimination layer can be thicker than the first thermal displacement elimination layer. The first thermal displacement elimination layer can have the same width as the scale. The first thermal displacement elimination layer can have the same width as the intermediate member. The first thermal displacement elimination layer can have a width smaller than the scale. The first thermal displacement elimination layer can have a width smaller than the intermediate member. The second thermal displacement elimination layer can have the same width as the intermediate member. The second thermal displacement elimination layer can have a width smaller than the intermediate member. The first thermal displacement elimination layer can have the same width as the second thermal displacement elimination layer. Alternatively, the first thermal displacement elimination layer and the second thermal displacement elimination layer can have different widths, for example, the first thermal displacement elimination layer can have a width larger than the second thermal displacement elimination layer. The first thermal displacement elimination layer and the second thermal displacement elimination layer may include a single adhesive layer (e.g., adhesive tape), and optionally, the first thermal displacement elimination layer includes a first region of the single adhesive layer for attaching the scale to the intermediate member, and the second thermal displacement elimination layer includes a second region of the single adhesive layer for attaching the intermediate member to the substrate.

[0013] Optionally, the scale comprises a metal or metal alloy. Optionally, the intermediate member comprises a metal or metal alloy. Optionally, the scale and the intermediate member comprise the same metal or metal alloy. The metal or metal alloy may comprise an iron-nickel (“FeNi”) alloy, for example, alloy composition FeNi36. Optionally, the scale comprises a glass or glass ceramic. Optionally, the intermediate member comprises a glass or glass ceramic. Optionally, the scale and the intermediate member comprise the same glass or glass ceramic. Optionally, the intermediate member comprises carbon fiber. Optionally, the scale device is attached to the substrate. Optionally, the scale device is attached to the substrate via the intermediate member. Optionally, the intermediate member is attached to the substrate via a second thermal displacement relief layer. Optionally, the intermediate member is attached to the substrate by one or more clips / clamps or other mechanical restraints / fasteners, such as the FASTRACK system available from Renishaw plc. The CTE of the intermediate member may be between the CTE of the scale and the CTE of the substrate, although of course this does not necessarily have to be the case.

[0014] Optionally, the first thermal displacement elimination layer is an adhesive layer. Optionally, the first thermal displacement elimination layer is an adhesive layer that attaches the scale to the intermediate member. Optionally, the second thermal displacement elimination layer is an adhesive layer. Optionally, the second thermal displacement elimination layer is an adhesive layer for attaching the intermediate member to the substrate.

[0015] Optionally, the first and / or second thermal displacement elimination layer comprises an adhesive tape. Optionally, the second thermal displacement elimination layer comprises an adhesive. Optionally, each thermal displacement elimination layer comprises an adhesive tape. The adhesive tape may be a carrier tape provided on each of the two surfaces having the adhesive layer.

[0016] Optionally, the thermal displacement elimination structure comprises two or more intermediate members. Optionally, the second thermal displacement elimination layer is an adhesive layer that attaches the first intermediate member to the second intermediate member. Optionally, the third thermal displacement elimination layer is an adhesive layer. Optionally, the third thermal displacement elimination layer is an adhesive layer for attaching the second intermediate member to the substrate. Optionally, the second intermediate member is attached to the substrate by one or more clips / clamps or other mechanical restraints / fasteners.

[0017] The scale device may be attached to the substrate by a thermal displacement eliminator layer that bonds an intermediate member of the thermal displacement eliminator structure (eg, the aforementioned intermediate member, or the second intermediate member, if present) to the substrate.

[0018] A thermally displaceable intermediate member (e.g., the aforementioned intermediate member or, if present, a second intermediate member) directly adjacent to the substrate may be fastened to the substrate (thereby attaching the scale device to the substrate) by at least one mechanical fastener. The at least one mechanical fastener may act to secure the intermediate member (e.g., the aforementioned intermediate member or, if present, a second intermediate member) relative to the substrate. Optionally, no adhesive layer and / or thermal displacement release layer is present between the intermediate member and the substrate.

[0019] According to a second aspect of the present invention, there is provided a scale device for a measurement encoder, the scale device comprising a metal or metal alloy scale and a thermal displacement elimination structure, the thermal displacement elimination structure comprising an intermediate member and a first thermal displacement elimination layer for attaching the scale to the intermediate member, the intermediate member comprising a metal or metal alloy, and the thermal displacement elimination structure optionally comprising a second thermal displacement elimination layer for attaching the intermediate member to a substrate.

[0020] According to a third aspect of the present invention, there is provided a scale device including a scale and a thermal displacement elimination structure, wherein the thermal displacement elimination structure includes a first intermediate member and a first thermal displacement elimination layer for attaching the scale to the first intermediate member, and a second intermediate member and a second thermal displacement elimination layer for attaching the first intermediate member to the second intermediate member. The scale can include a metal or a metal alloy. The intermediate member can include a metal or a metal alloy. The scale can include an iron-nickel (“FeNi”) alloy, particularly, alloy composition FeNi36. The second intermediate member can include carbon fiber.

[0021] According to a fourth aspect of the present invention, there is provided a scale device for a measurement encoder, the scale device including a scale and a thermal displacement elimination structure, the thermal displacement elimination structure including an intermediate member and a first thermal displacement elimination layer for attaching the scale to the intermediate member, and a relative stiffness between the scale and the first thermal displacement elimination layer of at least 0.33 mm. -2 is.

[0022] According to a fifth aspect of the present invention, there is provided a metrological scale including a scale support layer and an adhesive layer, the scale support layer having a thickness of 50 μm to 1000 μm and a surface roughness of 2×10 -6 k -1 The adhesive layer comprises a material having a coefficient of thermal expansion of: 20 kPa or less, and the adhesive layer has a shear modulus of 20 kPa or less.Optionally, the scale is a linear scale.

[0023] According to a sixth aspect of the present invention, there is provided a metrological scale including a scale support layer and an adhesive layer, the scale support layer having a thickness of 50 μm to 1000 μm and a thickness of 2×10 -6 k -1 Optionally, the substrate comprises a material having a coefficient of thermal expansion of 5×10 or less, and when attached to a substrate, the thermal expansion behavior of the scale support layer is characterized by the properties of the scale support layer. -6 K -1 ~25×10 -6 K -1Optionally, the substrate is granite, or iron, or steel, or aluminum. Optionally, the substrate has thermal expansion properties between those of granite and aluminum.

[0024] Optionally, the scale support layer comprises a nickel-iron alloy. The scale support layer may comprise FeNi36 (sometimes referred to as 64FeNi and sold as Invar®). The thickness of the scale support layer is optionally 900 μm or less, optionally 800 μm or less, optionally 700 μm or less, optionally 600 μm or less, optionally 500 μm or less, optionally 400 μm or less, optionally 300 μm or less, optionally 200 μm or less. Optionally, at least 100 μm. Optionally, the adhesive layer has a thickness of 0.2 mm or less.

[0025] According to a seventh aspect of the present invention there is provided a measurement encoder including a readhead and a scale according to the fifth or sixth aspect.

[0026] According to an eighth aspect of the present invention there is provided a machine including a scale according to the fifth or sixth aspect, or an encoder according to the seventh aspect. Optionally, the machine comprises a CMM or machine tool, a display manufacturing apparatus, or a semiconductor processing apparatus. Optionally, the adhesive layer is attached directly to the machine.

[0027] According to a ninth aspect of the present invention, there is provided a measurement encoder including a readhead and a scale attached to a substrate via an adhesive, the adhesive being disposed on the readhead facing a surface of the scale. Optionally, a gap is provided between the scale and the substrate. The scale may be attached to the substrate by a height control element.

[0028] By providing a measurement encoder that includes a readhead and a scale attached to a substrate by an adhesive, with the adhesive positioned on the readhead facing the surface of the scale, the height of the readhead facing the surface of the scale relative to the substrate can be maintained even if the adhesive expands.

[0029] Features of one embodiment may be incorporated into other embodiments.

[0030] Also disclosed is a scale device for a measurement encoder. The scale device may include a scale and a thermal displacement elimination structure. The thermal displacement elimination structure may include an intermediate member and a first thermal displacement elimination layer for attaching the scale to the intermediate member. The thermal displacement elimination structure may include a second thermal displacement elimination layer. The following may apply to the thermal expansion coefficients of the intermediate member and the scale:

[0031] -3×10 -6 K -1 ≦CTE(intermediate material)-CTE(scale)≦6×10 -6 K -1 . [Brief explanation of the drawings]

[0032] Embodiments of the present invention will now be described, by way of example only, with reference to the following drawings: [Figure 1] Figures 1(a) and (b) show a prior art device in which the scale is bonded to a substrate. [Figure 2] FIG. 2 shows a first scale device attached to a substrate. [Figure 3] FIG. 3 shows an embodiment of a scale system attached to a substrate. [Figure 4] FIG. 4 shows a second scale device attached to a substrate. [Figure 5] FIG. 5 shows a third scale device attached to a substrate. [Figure 6] FIG. 6 shows a fourth scale device. [Figure 7]FIG. 7 shows a fifth scale device attached to a substrate. DETAILED DESCRIPTION OF THE INVENTION

[0033] FIG. 1(a) shows a typical prior art arrangement in which a metrological scale 102 is attached to a substrate 110 via an adhesive layer 104 at a first temperature. The metrological scale 102 shown is an elongated metrological scale 102 having an elongated axis E. In use, the elongated axis E coincides with the direction of measurement. The substrate 110 in this case has a thickness of 21-24×10 -6 K -1 The metrology scale 102 in this case may be aluminum having a coefficient of thermal expansion (CTE) in the range of about 10×10 -6 K -1 It is a steel with a CTE of

[0034] This means that for a 1K temperature increase, the steel scale will expand by 10 μm per meter of scale, while the aluminum substrate will expand by up to 24 μm per meter. For every 1K temperature change, the scale must increase its length by 14 μm per meter of scale, less than the aluminum substrate. It will be appreciated that for longer scale lengths and / or larger temperature changes, this difference will be greater in absolute terms.

[0035] 1(b) shows the apparatus of FIG. 1(a) at a second temperature, higher than the first temperature. In this case, both the metrology scale 102 and the substrate 110 expand due to the increase in temperature. In an example where the substrate 110 is an aluminum substrate 110 and the scale 102 is a steel scale 102, the aluminum substrate 110 has a higher CTE than the steel scale 102, and therefore the aluminum substrate 110 expands by a greater amount than the steel scale 102. As the temperature increases, both the substrate 110 and the metrology scale 102 expand, but because they are connected by the adhesive layer 104, the expansion of the metrology scale 102 is affected by the expansion of the substrate 110. This changes the effective CTE of the steel scale 102 compared to the intrinsic CTE of the steel scale 102 (i.e., the CTE due to temperature change alone). In this case, the substrate 110 expands more than the steel scale 102 due to thermal expansion, and therefore the effective CTE of the steel scale 102 increases compared to the intrinsic CTE of the steel scale 102. -6 K -1 , for an aluminum substrate 110 having a length of 3 m (from the thermal base to the free edge), a width of 8 mm (dimension parallel to the surface of the substrate 110), and a thickness of 0.2 mm (dimension perpendicular to the surface of the substrate 110), the intrinsic CTE is 10 × 10 -6 K -1 The adhesive layer is 0.2 mm thick, 6 mm wide, and has a shear modulus of 1 kNm -2 , the effective CTE of steel scale 102 is 12.8 × 10 -6 K -1 It is known that...

[0036] The effect of the substrate 110 on the metrology scale 102 (transmitted by the adhesive layer 104) can introduce a degree of unpredictability depending, among other things, on the difference between the CTE of the metrology scale 102 and the CTE of the substrate 110. For example, the substrate 110 need not be aluminum; the substrate 110 could be granite. Granite typically has a CTE of 7.8-8.4×10 -6 K -1It will be appreciated that the effect on the metrology scale 102 caused by thermal expansion of the substrate 110 will be different for a granite substrate 110 compared to an aluminum substrate 110 because the substrate 110 has a CTE of 100 . In fact, because granite has a smaller CTE than steel, the change in effective CTE of the steel metrology scale 102 imparted by the granite substrate 110 will be negative (i.e., compressive) as the steel expands more than the granite substrate 110 with increasing temperature.

[0037] Therefore, it may not always be possible to know the magnitude or actual direction of the error introduced into the measurement system due to the CTE mismatch between the scale and the substrate.

[0038] 2 shows an exemplary embodiment of a scale apparatus 200 according to the present invention. The scale apparatus 200 includes a scale 202. In the scale apparatus 200 shown in FIG. 2, the scale 202 is attached to a substrate 210 via a thermal displacement elimination structure 212. The thermal displacement elimination structure 212 includes a first adhesive layer 204, an intermediate member 206, and a second adhesive layer 208.

[0039] In this embodiment, the scale 202 is a measurement scale 202. The scale 202 in Figure 2 is an elongated scale 202 having an elongated axis E. When used, the elongated axis E coincides with the measurement direction. The scale 202 has markings that can be read by a readhead to determine the relative position. In this embodiment, the scale 202 is a steel scale 202.

[0040] 2 is the same as scale 202, but may not have indicia that can be read by a readhead. Intermediate member 206 in this embodiment is made of the same material as scale 202 and has the same dimensions (width, height, length) as scale 202.

[0041] The first adhesive layer 204 and the second adhesive layer 208 shown in FIG. 2 are the same in this embodiment and include an adhesive tape. The adhesive tape can be a carrier tape with an adhesive layer on each of two sides. The second adhesive layer 208 is non-rigid and can be deformed by a force (e.g., a shear force) transmitted to the first interface (e.g., between the substrate 210 and the second adhesive layer 208) due to the expansion of the substrate 210 due to a change in temperature. Here, a material can be considered non-rigid if it has a low shear modulus. In this embodiment, an elastically stretchable adhesive tape is used. The shear modulus of the adhesive tape is 1.2 kPa. A force acts on the second interface (e.g., between the second adhesive layer 208 and the intermediate member 206) due to the expansion of the intermediate member 206 due to a change in temperature. If the expansion of the substrate 210 and the intermediate member 206 are not the same, the second adhesive layer 208 exerts a shear force on the intermediate member 206 due to the difference in thermal expansion of the substrate 210, which affects the deformation behavior of the intermediate member 206. The deformation of the second adhesive layer 208 due to the thermal expansion of the substrate 210 and / or the intermediate member 206 is elastic. The first adhesive layer 204 is non-rigid and can be deformed by a force (such as a shear force), which causes deformation of the first adhesive layer at the third interface (such as between the intermediate member 206 and the first adhesive layer 204) due to the expansion of the intermediate member 206. In this embodiment, an elastically stretchable adhesive tape is used. The shear modulus of the adhesive tape is 1.2 kPa. In this embodiment, the intermediate member can expand due to changes in temperature and by forces caused by the difference in thermal expansion of the substrate 210. The scale 202 can also expand due to changes in temperature. The scale 202 also experiences forces (such as shear forces) at a fourth interface (such as between the first adhesive layer 204 and the scale 202) when the expansion of the scale 202 differs from the expansion of the intermediate member 206 due to changes in temperature. The forces acting on the scale 202 due to the difference in thermal expansion between the scale 202 and the intermediate member 206 affect the deformation behavior of the scale 202.

[0042] In embodiments where the scale 202 is a steel scale 202 and the intermediate member 206 is a steel intermediate member 206, and where the scale and intermediate member are located on an aluminum substrate 210, it will be understood that as the temperature of the scale device 200 and the substrate 210 changes, the difference in the CTE values of the steel scale 202, the steel intermediate member 206, and the aluminum substrate 210 will cause the aluminum substrate 210 to thermally expand to a different extent than the steel scale 202 and the steel intermediate member 206.

[0043] As the temperature of the scale device 200 and the substrate 210 increases, the aluminum substrate 210 must thermally expand more than the steel intermediate member 206 or the steel scale 202. As the aluminum substrate 210 expands, the second adhesive layer 208 at its interface with the aluminum substrate 210 deforms, creating a shear force that acts on the interface between the second adhesive layer 208 and the steel intermediate member 206. The steel intermediate member 206, which has expanded due to the increase in temperature, further expands due to the shear force caused by the difference in thermal expansion between the intermediate member 206 and the substrate 210. Thus, in this embodiment, the steel intermediate member 206 has an effective CTE that is higher than the intrinsic CTE of the material from which the intermediate member 206 is made. The expansion of the steel intermediate member 206 causes the first adhesive layer 204 at its interface to deform, which in turn exerts a shear force at the interface between the first adhesive layer 204 and the steel scale 202. The steel scale 202 is further expanded by this shear force, which is caused by the difference in thermal expansion between the steel scale 202 and the steel intermediate member 206. Thus, in this embodiment, the steel scale 202 has an effective CTE that is higher than the intrinsic CTE of the material from which the scale 202 is made, but less than it would be if it were attached directly to a substrate.

[0044] A steel scale 202 having a length of 3 m (from the reference end to the free end in the measurement direction), a width of 8 mm (a dimension parallel to the surface of the substrate 210 and perpendicular to the measurement direction), and a thickness of 0.2 mm (a dimension perpendicular to the surface of the substrate 210), and having a 10×10 -6 K-1 and a steel intermediate member 206 having a length of 3 m (from the reference to the free end in the measurement direction), a width of 8 mm (a dimension parallel to the surface of the substrate 210 and perpendicular to the measurement direction), and a thickness of 0.2 mm (a dimension perpendicular to the surface of the substrate 210), and -6 K -1 and an intermediate member 206 having an inherent CTE of 0.2 mm, the first adhesive layer 204 and the second adhesive layer 208 having a thickness of 0.2 mm, a width of 6 mm, and a strength of 1 kNm. -2 The adhesive tape has a shear modulus of 24×10 -6 K -1 When located on an aluminum substrate 210 having a CTE of 10.56×10, the effective CTE of the steel scale 202 is 10.56×10. -6 K -1 is.

[0045] It can be seen that the introduction of the steel intermediate member 206 reduces the deviation of the CTE of the steel scale 202 from the intrinsic CTE of the material from which it is made, as compared to the example described above in connection with the steel scale 102 of Figure 1. In other words, the behavior of the scale 202 is improved by reducing the effect of the difference in thermal expansion between the substrate and the scale. The introduction of the steel intermediate member 206 reduces the effective CTE by 2.24 x 10 -6 K -1 A small reduction has been achieved.

[0046] The scale device according to the first embodiment can be used to scale different substrates, e.g., 8×10 -6 K -1 The granite substrate may have an inherent CTE of 0.1.

[0047] A steel scale 202 having a length of 3 m (from the reference end to the free end in the measurement direction), a width of 8 mm (a dimension parallel to the surface of the substrate 210 and perpendicular to the measurement direction), and a thickness of 0.2 mm (a dimension perpendicular to the surface of the substrate 210), and having a 10×10 -6 K -1and a steel intermediate member 206 having a length of 3 m (from the reference to the free end in the measurement direction), a width of 8 mm (a dimension parallel to the surface of the substrate 210 and perpendicular to the measurement direction), and a thickness of 0.2 mm (a dimension perpendicular to the surface of the substrate 210), -6 K -1 and an intermediate member 206 having an inherent CTE of 0.2 mm, the first adhesive layer 204 and the second adhesive layer 208 having a thickness of 0.2 mm, a width of 6 mm, and a strength of 1 kNm. -2 and the scale and intermediate member of the first embodiment have a shear modulus of 8×10 -6 K -1 When located on a granite substrate 210 having a CTE of 9.9×10, the effective CTE of the steel scale 202 is 9.9×10. -6 K -1 is.

[0048] As can be seen from applying the first embodiment to aluminum and granite substrates, in both cases the behavior of the steel scale as the temperature changes is closer to floating than dominated. Pure floating behavior is when the thermal variation of temperature is independent of the substrate, in other words when the effective CTE of the scale 202 is the same as the intrinsic CTE of the material from which the scale 202 is made. Dominated behavior is when the scale is attached to the substrate such that the thermal behavior of the scale is dominated by the thermal behavior of the substrate; if the scale is completely dominated by the substrate, the effective CTE of the scale will be the intrinsic CTE of the substrate material.

[0049] A low expansion iron-nickel (“FeNi”) alloy (having alloy composition FeNi36, often Invar®) scale 202 having a length of 3 m (from datum to free end in the direction of measurement), a width of 8 mm (dimension parallel to the surface of the substrate 210 and perpendicular to the direction of measurement), and a thickness of 0.2 mm (dimension perpendicular to the surface of the substrate 210) with a 1.0×10 -6 K -1and a low-expansion FiNi alloy intermediate member 206 having a length of 3 m (from the reference to the free end in the measurement direction), a width of 8 mm (a dimension parallel to the surface of the substrate 210 and perpendicular to the measurement direction), and a thickness of 0.2 mm (a dimension perpendicular to the surface of the substrate 210), and having an intrinsic CTE of 1.0 × 10 -6 K -1 and an intermediate member 206 having an intrinsic CTE of 0.2 mm, and the first adhesive layer 204 and the second adhesive layer 208 have a thickness of 0.2 mm, a width of 6 mm, and a strength of 1 kNm. -2 and the scale and intermediate member of the second embodiment have a shear modulus of 24×10 -6 K -1 When located on an aluminum substrate 210 having a CTE of 2.68×10, the effective CTE of the low expansion FeNi alloy scale 202 is 2.68×10. -6 K -1 This is a result of applying a low-expansion FeNi alloy scale of the same dimensions to a 24 × 10 scale by a single adhesive tape with a thickness of 0.2 mm, a width of 6 mm, and a shear modulus of 1 kPa. -6 K -1 When mounted on an aluminum substrate with a CTE of 7.21 x 10 -6 K -1 By introducing the low-expansion FeNi alloy intermediate member 206, the effective CTE was reduced to 4.53 × 10 -6 K -1 A reduction in the

[0050] The scale and intermediate member of the second embodiment are 8×10 -6 K -1 When positioned on a granite substrate 210 having a CTE of 1.51×10, the effective CTE of the low expansion FeNi alloy scale 202 of the second embodiment is 1.51×10. -6 K -1 This is the result of applying a low expansion FeNi alloy scale of the same dimensions to an 8 × 10 adhesive tape with a shear modulus of 1.2 kPa. -6 K -1 When mounted on a granite substrate with a CTE of 2.89 x 10 -6 K -1By introducing the low-expansion FeNi alloy intermediate member 206, the effective CTE was reduced to 1.38 × 10 -6 K -1 A reduction in the

[0051] The first and second embodiments include a scale 202 and intermediate member 206 made from the same material and therefore have substantially the same intrinsic CTE (+ / - 3x10 -6 k-1), but the present invention can also be realized when the scale 202 and the intermediate member 206 are made of different materials, for example, when the inherent CTE values of the materials of the scale 202 and the intermediate member 206 are different.

[0052] An embodiment of the present invention can include a scale device 202 having a specific CTE between the specific CTE of the intermediate member 206 and the specific CTE of the substrate 210 to which the scale device 200 is intended to be attached. This can work well when the intermediate member 206 is obstructed by the substrate 210. The obstructed intermediate member 206 can result in more favorable expansion of the scale 202 than would be achieved if the scale 202 and the intermediate member 206 had substantially similar specific CTE values.

[0053] A steel scale 202 having a length of 3 m (from the reference end to the free end in the measurement direction), a width of 8 mm (a dimension parallel to the surface of the substrate 210 and perpendicular to the measurement direction), and a thickness of 0.2 mm (a dimension perpendicular to the surface of the substrate 210), and having a 10×10 -6 K -1 and a titanium intermediate member 206 having a length (from the reference to the free end in the measurement direction), a width (a dimension parallel to the surface of the substrate 210 and perpendicular to the measurement direction), and a thickness of 0.2 mm (a dimension perpendicular to the surface of the substrate 210), with an intrinsic CTE of 8×10. -6 K -1and an intermediate member 206 having an intrinsic CTE of 24×10. The first adhesive layer 204 and the second adhesive layer 208 are adhesive tapes having a thickness of 0.2 mm, a width of 6 mm, and a shear modulus of 1 kPa, and the scale and intermediate member of the third embodiment are 24×10. -6 K -1 When located on an aluminum substrate 210 having a CTE of 10.59×10, the effective CTE of the steel scale 202 is 10.59×10. -6 K -1 This is because by introducing a titanium intermediate member 206, a steel scale of the same dimensions is bonded to a 24 × 10 scale by adhesive tape with a thickness of 0.2 mm, a width of 6 mm, and a shear modulus of 1 kPa. -6 K -1 When mounted on an aluminum substrate with a CTE of 12.8 x 10 -6 K -1 compared to an effective CTE of 2.24 × 10 -6 K -1 A reduction in the

[0054] An embodiment of the present invention may include a scale device in which the intermediate member 206 has a CTE between the inherent CTE of the scale 202 and the inherent CTE of the substrate 210 to which the scale device 200 is intended to be attached, although this is not necessarily the case.

[0055] A steel scale 202 having a length of 3 m (from the reference end to the free end in the measurement direction), a width of 8 mm (a dimension parallel to the surface of the substrate 210 and perpendicular to the measurement direction), and a thickness of 0.2 mm (a dimension perpendicular to the surface of the substrate 210), and having a 10×10 -6 K -1 and a 3-series intermediate member 206 having a length (from the reference to the free end in the measurement direction) of 3 m, a width of 8 mm (a dimension parallel to the surface of the substrate 210 and perpendicular to the measurement direction), and a thickness of 0.2 mm (a dimension perpendicular to the surface of the substrate 210), and -6 K -1and an intermediate member 206 having an intrinsic CTE of 24×10. The first adhesive layer 204 and the second adhesive layer 208 are adhesive tapes having a thickness of 0.2 mm, a width of 6 mm, and a shear modulus of 1 kPa, and the scale and intermediate member of the fourth embodiment are -6 K -1 When located on an aluminum substrate 210 having a CTE of 11.54×10, the effective CTE of the steel scale 202 is 11.54×10. -6 K -1 This is the result of applying a 24 × 10 adhesive tape with a shear modulus of 1.2 kPa to a steel scale of the same dimensions. -6 K -1 When mounted on an aluminum substrate with a CTE of 12.8 x 10 -6 K -1 Compared with the effective CTE of 1.26×10, the introduction of the 3-series steel intermediate member 206 resulted in an effective CTE of 1.26×10 -6 K -1 A reduction in the

[0056] A scale 202 made of a low-expansion FeNi alloy having a length of 3 m (from the reference end to the free end in the measurement direction), a width of 8 mm (a dimension parallel to the surface of the substrate 210 and perpendicular to the measurement direction), and a thickness of 0.2 mm (a dimension perpendicular to the surface of the substrate 210) was used. -6 K -1 and a carbon fiber intermediate member 206 having a length (from the reference to the free end in the measurement direction), a width of 15 mm (a dimension parallel to the surface of the substrate 210 and perpendicular to the measurement direction), and a thickness of 1.5 mm (a dimension perpendicular to the surface of the substrate 210), and having an intrinsic CTE of -1×10 -6 K -1 and an intermediate member 206 having an intrinsic CTE of 24×10. The first adhesive layer 204 and the second adhesive layer 208 are adhesive tapes having a thickness of 0.2 mm, a width of 6 mm, and a shear modulus of 1 kPa. The scale and intermediate member of the fifth embodiment are -6 K -1 When located on an aluminum substrate 210 having a CTE of 0.58×10, the effective CTE of the FeNi alloy scale 202 is 0.58×10. -6K -1 This is the result of applying a 24 × 10 adhesive tape with a shear modulus of 1.2 kPa to an FeNi alloy scale of the same size. -6 K -1 When mounted on an aluminum substrate with a CTE of 7.2 x 10 -6 K -1 By introducing the carbon fiber intermediate member 206, the effective CTE is 6.7 × 10 -6 K -1 A reduction in effective CTE of

[0057] The scale and intermediate member of the fifth embodiment are 8×10 -6 K -1 When positioned on a granite substrate 210 having a CTE of 0.50×10, the effective CTE of the steel scale 202 of the fifth embodiment is 0.50×10. -6 K -1 This is the result of applying a steel scale of the same dimensions to an 8 × 10 adhesive tape with a single adhesive layer having a thickness of 0.2 mm, a width of 6 mm, and a shear modulus of 1 kPa. -6 K -1 When mounted on a granite substrate with a CTE of 2.90 x 10 -6 K -1 By introducing the carbon fiber intermediate member 206, the effective CTE is 2.40 × 10 -6 K -1 A reduction in effective CTE of

[0058] A low expansion glass ceramic scale 202 having a length of 3 m (from the reference end to the free end in the measurement direction), a width of 15 mm (a dimension parallel to the surface of the substrate 210 and perpendicular to the measurement direction), and a thickness of 3 mm (a dimension perpendicular to the surface of the substrate 210), with a 0.5×10 -6 K -1 and a low expansion glass ceramic intermediate member 206 having a length (from datum to free end in the measurement direction), a width (in the dimension parallel to the surface of the substrate 210), and a thickness (in the dimension perpendicular to the surface of the substrate 210) of 3 m, and having an intrinsic CTE of -0.5×10.-6 K -1 and an intermediate member 206 sold under the trademark Robax®, which has an inherent CTE of 1.2 kPa, wherein the first adhesive layer 204 and the second adhesive layer 208 are adhesive tapes having a shear modulus of 1.2 kPa, and the scale and intermediate member of the sixth embodiment have an inherent CTE of 8×10. -6 K -1 The effective CTE of the Robax® scale 202 when placed on a granite substrate 210 having a CTE of 0.48×10 -6 K -1 This is the result of applying 8 × 10 pressure to a Robax scale of the same dimensions with adhesive tape having a thickness of 0.2 mm, a width of 6 mm, and a shear modulus of 1 kPa. -6 K -1 When mounted on a granite substrate with a CTE of 0.66 x 10 -6 K -1 By introducing the Robax® intermediate member 206, the effective CTE of -6 K -1 A reduction in effective CTE of

[0059] One factor that affects the extent to which the scale 202 is disturbed by a mismatch between the CTE of the scale 202 and the CTE of the substrate 210 on which the scale device 200 is disposed is the stiffness of the intermediate member 206. As discussed above, as the temperature increases, the substrate 210 expands, which results in forces being transmitted through the second adhesive layer 208 that can cause the intermediate member 206 to elongate (for a substrate 210 with a higher intrinsic CTE compared to the CTE of the intermediate member 206). Increasing the stiffness of the intermediate member 206 reduces variations caused by a mismatch in the intrinsic CTE values of the substrate 210 and the intermediate member 206.

[0060] A steel scale 202 having a length of 3 m (from the reference end to the free end in the measurement direction), a width of 8 mm (a dimension parallel to the surface of the substrate 210 and perpendicular to the measurement direction), and a thickness of 0.2 mm (a dimension perpendicular to the surface of the substrate 210), and having a 10×10 -6 K -1and a titanium intermediate member 206 having a length (from the reference to the free end) of 3 m, a width of 8 mm (a dimension parallel to the surface of the substrate 210 and perpendicular to the measurement direction), and a thickness of 0.1 mm (a dimension perpendicular to the surface of the substrate 210), with an intrinsic CTE of 8×10 -6 K -1 and an intermediate member 206 having an intrinsic CTE of 24×10. The first adhesive layer 204 and the second adhesive layer 208 are adhesive tapes having a thickness of 0.2 mm, a width of 6 mm, and a shear modulus of 1 kPa, and the scale and intermediate member of the seventh embodiment are 24×10. -6 K -1 When located on an aluminum substrate 210 having a CTE of 11.1×10, the effective CTE of the steel scale 202 is 11.1×10. -6 K -1 This is the result of applying a 24 × 10 scale to a steel scale of the same dimensions with adhesive tape having a thickness of 0.2 mm, a width of 6 mm, and a shear modulus of 1 kPa. -6 K -1 When mounted on an aluminum substrate with a CTE of 12.10 x 10 -6 K -1 By introducing the titanium intermediate member 206, the effective CTE is 1.77 × 10 -6 K -1 A reduction in effective CTE of

[0061] The difference between the third embodiment and the seventh embodiment is the thickness (the dimension perpendicular to the surface of the substrate 210) of the titanium intermediate member 206. The titanium intermediate member 206 of the seventh embodiment has half the thickness (the dimension perpendicular to the surface of the substrate 210) of the titanium intermediate member 206 of the third embodiment, and therefore has half the rigidity. The third embodiment has a thickness of 2.24×10 -6 K -1 while the seventh embodiment achieves an effective CTE reduction of 1.76×10 -6 K -1 Therefore, it can be seen that the stiffness of the intermediate member 206 can be used to adjust the behavior of the scale 202.

[0062] A scale 202 of low expansion inorganic non-porous lithium aluminum silicon oxide glass ceramic having a length of 3 m (from the reference point to the end in the measurement direction), a width of 15 mm (the dimension parallel to the surface of the substrate 210 and perpendicular to the measurement direction), and a thickness of 3 mm (the dimension perpendicular to the surface of the substrate 210), with a 0.02×10 -6 K -1 The scale 202 is sold as Zerodur® and has an inherent CTE of 1×10. ... -6 K -1 and an intermediate member 206 having an inherent CTE of 8×10, wherein the first adhesive layer 204 and the second adhesive layer 208 are adhesive tapes having a thickness of 0.2 mm, a width of 6 mm, and a shear elastic modulus of 1 kPa, and the scale and intermediate member of the eighth embodiment have an inherent CTE of 8×10. -6 K -1 When placed on a granite substrate 210 having a CTE of 0.048×10, the effective CTE of the ® scale 202 is 0.048×10. -6 K -1 This is the same as the measurement of an 8 x 10 scale of Zerodur® of the same dimensions with an adhesive tape having a thickness of 0.2 mm, a width of 6 mm, and a shear modulus of 1 kPa. -6 K -1 When mounted on a granite substrate with a CTE of 0.17 x 10 -6 K -1 By introducing the Invar intermediate member 206, the effective CTE is reduced to 0.13 × 10 -6 K -1 This is a 70% reduction in effective CTE.

[0063] A glass-ceramic scale 202 having a length of 3 m (from the reference to the free end in the measurement direction), a width of 15 mm (a dimension parallel to the surface of the substrate 210 and perpendicular to the measurement direction), and a thickness of 3 mm (a dimension perpendicular to the surface of the substrate 210), with a resolution of 0.02×10-6 K -1 The scale 202 is sold as Zerodur® and has an inherent CTE of 1×10, and the Invar® intermediate member 206 is 3 m long (from the reference to the free end in the measurement direction), 6 mm wide (dimension parallel to the surface of the substrate 210 and perpendicular to the measurement direction), and 0.05 mm thick (dimension perpendicular to the surface of the substrate 210). -6 K -1 and an intermediate member 206 having an inherent CTE of 8×10. The first adhesive layer 204 and the second adhesive layer 208 are adhesive tapes having a thickness of 0.2 mm, a width of 6 mm, and a shear elastic modulus of 1 kPa, and the scale and intermediate member of the ninth embodiment have an inherent CTE of 8×10. -6 K -1 When placed on a granite substrate 210 having a CTE of 0.114×10, the effective CTE of the Zwrodur® scale 202 is 0.114×10. -6 K -1 This is the same as the measurement of an 8 x 10 scale of Zerodur® of the same dimensions with an adhesive tape having a thickness of 0.2 mm, a width of 6 mm, and a shear modulus of 1 kPa. -6 K -1 When mounted on a granite substrate with a CTE of 0.17 x 10 -6 K -1 By introducing the Invar® intermediate member 206, the effective CTE is reduced to 0.06×10 -6 K -1 This is a 34% reduction in effective CTE.

[0064] In the eighth embodiment, the stiffness of the intermediate member divided by the stiffness of the scale is 0.104, while in the ninth embodiment, the stiffness of the intermediate member divided by the stiffness of the scale is 0.0138. It can be seen that an improvement in the behavior of the scale member 202 can be achieved even when the stiffness of the intermediate member 206 is much less than the stiffness of the scale 202.

[0065] Another factor that can affect the performance of the scale device 200 is the ability of the first adhesive layer 204 and the second adhesive layer 208 to generate a force at a second interface (such as the interface between the first adhesive layer 204 and the scale 202) for a given expansion of the first interface (such as the interface between the intermediate member 206 and the first adhesive layer 204). This can be measured as shear stiffness per unit length, k. The higher the value of k, the more effectively the adhesive layer generates a force at the second interface for a given expansion of the first interface. The shear stiffness per unit length of an adhesive tape can be calculated by multiplying the shear modulus of the adhesive tape by its thickness and then dividing by its width.

[0066] As discussed above, the amount of interference that intermediate member 206 experiences due to expansion of substrate 210 due to a CTE mismatch is related to the force generated at the interface between intermediate member 206 and second adhesive layer 208 due to the stretching of second adhesive layer 208 at the interface between second adhesive layer 208 and substrate 210. Thus, the amount of interference that intermediate member 206 experiences in a particular case is based on the ability of second adhesive layer 208 to generate a force (shear stiffness, k) at the second interface due to the stretching at the first interface, and the extent to which intermediate member 206 is subjected to the force (stiffness of intermediate member 206).

[0067] The stiffness of the intermediate member 206 can be calculated by taking the product of the Young's modulus (E) of the material and the cross-sectional area (A) of the intermediate member 206 .

[0068] The relative stiffness (R) of the intermediate member 206 and the second adhesive layer 208, which generates a force at the interface between the second adhesive layer 208 and the intermediate member 206 due to the expansion of the substrate 210, can be defined as the stiffness (EA) of the intermediate member 206 divided by the shear stiffness per unit length (k) of the second adhesive layer 208. R=EA / k For example, in the first embodiment, R=11.2 m −2 .

[0069] R=0.27m -2In embodiments (either the scale 202 and the first adhesive layer 204, or the intermediate member and the second adhesive layer 208), the scale 202 of a 1 meter long scale device is intermediate between floating and dominated (the effective CTE of the scale is intermediate between the intrinsic CTE of the material from which the scale 202 is made and the intrinsic CTE of the material from which the substrate is made). At shorter lengths, the scale 202 has an effective CTE that is closer to the intrinsic CTE of the scale material than to the CTE of the substrate 210. Longer scale lengths exhibit an effective CTE that is closer to the intrinsic CTE of the substrate 210.

[0070] For either the scale 202 and the first adhesive layer 204, or the intermediate member and the second adhesive layer 206, R=1 m -2 In this embodiment, the 2m axis is halfway between floating and dominated, to one significant figure. At shorter lengths, the scale 202 has an effective CTE that is closer to the intrinsic CTE of the scale material than the CTE of the substrate 210.

[0071] For a typical scale length, the relative stiffness (R) value of the intermediate member 206 and the second adhesive layer 208, or the relative stiffness (R) value of the scale 202 and the first adhesive layer 204, is 0.33 m. -2 This has been found to result in substantial improvements.

[0072] The relative stiffness (R) of at least one of the intermediate member 206 and the second adhesive layer 208 or the scale 202 and the first adhesive layer 204 is 1 m -2 If this is the case, a significant improvement in the performance of the scale 202 is observed.

[0073] A steel scale 202 having a length of 2 m (from the reference end to the free end in the measurement direction), a width of 8 mm (a dimension parallel to the surface of the substrate 210 and perpendicular to the measurement direction), and a thickness of 0.18 mm (a dimension perpendicular to the surface of the substrate 210), and having a 10×10 -6 K -1and a steel intermediate member 206 having a length of 2 m (from the reference to the free end in the measurement direction), a width of 8 mm (a dimension parallel to the surface of the substrate 210 and perpendicular to the measurement direction), and a thickness of 0.18 mm (a dimension perpendicular to the surface of the substrate 210), -6 K -1 and an intermediate member 206 having an inherent CTE of 0.2 mm, and the first adhesive layer 204 and the second adhesive layer 208 have a thickness of 0.2 mm, a width of 6 mm, and a strength of 10 kNm. -2 For each layer with a shear modulus of R = 1 m -2 The adhesive tape of the tenth embodiment provides a 24×10 -6 K -1 When located on an aluminum substrate 210 having a CTE of 10.796×10, the effective CTE of the steel scale 202 is 10.796×10. -6 K -1 This is the result of applying a 24 × 10 adhesive tape of the same dimensions to a steel scale with a thickness of 0.2 mm, a width of 6 mm, and a shear modulus of 10 kPa. -6 K -1 When mounted on an aluminum substrate with a CTE of 13.3 x 10 -6 K -1 By introducing the steel intermediate member 206, the effective CTE is increased to 2.54 × 10 -6 K -1 A small reduction has been achieved.

[0074] Although the above-described embodiments are described with respect to a scale device as shown in FIG. 2, other embodiments may include alternative configurations for the thermal displacement elimination structure of the scale device.

[0075] 3 shows an exemplary configuration of a scale device 300 according to the present invention. The scale device 300 includes a scale 302. In the scale device 300 shown in FIG. 3, the scale 302 is attached to a substrate 310 via a thermal displacement elimination structure 312. The thermal displacement elimination structure 312 includes a first adhesive layer 304, a first intermediate member 306, a second adhesive layer 308, a second intermediate member 314, and a third adhesive layer 316.

[0076] In this embodiment, the scale 302 is a measurement scale 302. The scale 302 in Figure 3 is an elongated scale 302 having an elongated axis E. In use, the elongated axis E coincides with the direction of measurement. The scale 302 has markings that can be read by a readhead to determine relative position.

[0077] The first adhesive layer 304, the second adhesive layer 308, and the third adhesive layer 316 shown in FIG. 3 are non-rigid and can stretch. A force (such as a shear force) exerted due to stretching at a first interface (such as between the substrate 310 and the third adhesive layer 316) causes a force to act at a second interface (such as between the third adhesive layer 316 and the second intermediate member 214). The deformation of the third adhesive layer 316 due to thermal expansion of the substrate 310 and / or the second intermediate member 314 is elastic. The deformation of the second adhesive layer 308 and / or the first intermediate member 306 is elastic. The first adhesive layer 304 is a thermal displacement elimination layer. The second adhesive layer 308 is a thermal displacement elimination layer. The third adhesive layer is a thermal displacement elimination layer. Here, a material can be considered non-rigid if it has a low shear modulus. For example, each of the first adhesive layer 304, the second adhesive layer 308, and the third adhesive layer 316 can be an adhesive tape having a shear modulus of 1 kPa.

[0078] In a particularly preferred embodiment, both scale devices are 1.0×10 -6 K -1and a first intermediate member (e.g., 306) including / made from a low expansion FeNi alloy (having alloy composition FeNi36, often referred to as Invar®) having a specific CTE of -1×10 -6 K -1 The scale further includes a second intermediate member (e.g., 314) including / made of carbon fiber having a specific CTE of 1 / 2. According to the above-described embodiment, a first thermal displacement layer (e.g., first adhesive layer 304) is provided between the scale and the first intermediate member, and a second thermal displacement layer (e.g., second adhesive layer 308) is provided between the first intermediate member and the second intermediate member. The second intermediate member (i.e., in this embodiment, the carbon fiber layer) can be attached to a substrate via the adhesive layer or fixed to the substrate. The composite structure of multiple layers of low-expansion FeNi as described above enables thinner, therefore less expensive, and lighter, scales made from low-expansion FeNi alloy without sacrificing metrology performance. Furthermore, the high specific stiffness of carbon fiber aids in handling the FeNi alloy, thereby reducing the risk of damage if not properly supported, for example, during installation. In an optional embodiment, the width of the second intermediate member (i.e., in this embodiment, the carbon fiber layer) can be wider than the layers above it. This may be beneficial for mechanical, handling and / or fixation purposes.

[0079] FIG. 4 shows an exemplary configuration of a scale device 400 according to the present invention. In FIG. 4, an elongated axis E extends into / out of the plane of the drawing. The scale device 400 includes a scale 402. In the scale device 400 shown in FIG. 4, the scale 402 is attached to a substrate 410 via a thermal displacement elimination structure 412. The thermal displacement elimination structure 412 includes an adhesive layer 404 and an intermediate member 406. The scale device 400 shown in FIG. 4 is elongated and has an elongated measurement direction perpendicular to the plane of the drawing.

[0080] In this embodiment, the scale 402 is a metrological scale 402. The scale 402 in Figure 4 is an elongated scale 402. Figure 4 shows a cross section of the scale, perpendicular to the elongated axis of the scale 402. In use, the elongated axis coincides with the direction of measurement. The scale 402 has markings that can be read by a readhead to determine relative position.

[0081] The adhesive layer 404 shown in FIG. 4 is non-rigid and stretchable, i.e., a force (such as a shear force) exerted due to stretching at a first interface (such as between the intermediate member 406 and the adhesive layer 404) generates a force acting at a second interface (such as between the adhesive layer 404 and the scale 402). The deformation of the adhesive layer 404 due to thermal expansion of the intermediate member 406 and / or the scale 402 is elastic. The adhesive layer 404 is a thermal displacement elimination layer. Here, if a material has a low shear modulus, the material can be considered non-rigid. Here, the adhesive tape can be stretched elastically. For example, the shear modulus of the adhesive tape forming the first adhesive layer 404 can be 1 kPa.

[0082] Fasteners 408 are located on each side of the scale device 400 to hold the intermediate member 406 against the substrate during use of the device.

[0083] 4, the mismatch between the intrinsic CTE of the substrate 410 and the intrinsic CTE of the intermediate member 406 can cause the intermediate member 406 to have an effective CTE that is different from the intrinsic CTE of the intermediate member 406 due to frictional forces between the intermediate member 406 and the substrate and / or frictional forces between the intermediate member 406 and the fasteners 408. These frictional forces can arise when the substrate 410 and the intermediate member 406 expand at different rates due to changes in temperature or mechanical strain on the scale or substrate.

[0084] In some embodiments, the intermediate member 406 may include carbon fiber.

[0085] FIG. 5 illustrates an exemplary configuration of a scale device 500 in accordance with the present invention. In FIG. 5, an elongated axis E extends into / out of the plane of the page. The configuration illustrated in FIG. 5 is similar to the configuration illustrated in FIG. 4, except for a thermal displacement elimination structure 512. The thermal displacement elimination structure configuration in FIG. 5 includes a first adhesive layer 504, a first intermediate member 506, a second adhesive layer 507, and a second intermediate member 508. The scale device 500 illustrated in FIG. 5 is attached to a substrate 510 by fasteners 509 that hold the second intermediate member 508 to the substrate 510. In some embodiments, the second intermediate member 508 comprises carbon fiber.

[0086] Figure 6 shows an exemplary configuration of a scale device 600 according to the present invention. The scale device 600 includes a scale 602. In the scale device 600 shown in Figure 6, the scale 602 is attached to a thermal displacement elimination structure. The thermal displacement elimination structure includes a first adhesive layer 604A, which is a heat removal layer, and which attaches the scale 602 to a first intermediate member 606A. The thermal displacement elimination structure further includes a second adhesive layer 604B, which is a heat removal layer, and which attaches the scale 602 to a second intermediate member 606B.

[0087] In some embodiments, the first adhesive layer 604A and the second adhesive layer 604B also attach the scale to the substrate 608. In other embodiments, the scale 602 is attached to the substrate 608 via a through thermal displacement relief structure that includes the adhesive layer 604A and the intermediate member 606A, but without the latter second adhesive 604B or second intermediate member 606B.

[0088] In other embodiments, the first adhesive layer 604A and the second adhesive layer 604B also attach the scale to the intermediate member 608. In some embodiments, the intermediate member 608 comprises carbon fiber. The scale device 600 shown in Figure 6 can be attached to a substrate, for example, via a third adhesive layer (which may be a heat extraction layer), by fasteners, or by any other attachment method known to one of skill in the art.

[0089] FIG. 7 shows an exemplary configuration of a scale device according to the present invention. The scale device includes a scale 702. In the scale device shown in FIG. 7, the scale 702 is attached to an adhesive layer 704, which attaches the scale 702 to a substrate 710. In this embodiment, the scale 702 is a low-CTE scale, specifically, an FeNi36 (sometimes referred to as 64FeNi or Invar®) scale, having a thickness (perpendicular to the substrate) of 200 μm. The adhesive layer is an adhesive tape having a thickness (perpendicular to the substrate) of 0.2 mm and a shear modulus of 1 kPa when the adhesive tape has a width of 6 mm. In other embodiments, the adhesive layer may include two or more layers of adhesive tape. In further embodiments, the thickness of each or each layer of adhesive tape need not be 0.2 mm; for example, the thickness of each layer of adhesive tape may be greater than or less than 0.2 mm.

Claims

1. A scale device for a measuring encoder, comprising a scale and a thermal displacement removal structure, the thermal displacement removal structure including an intermediate member, a first thermal displacement removal layer, and a second thermal displacement removal layer, wherein the first thermal displacement removal layer is for attaching the scale to the intermediate member, and the thermal expansion coefficients of the intermediate member and the scale are as follows: -3 x 10 －６ K －１ ≤ CTE (intermediate member) - CTE (scale) ≤ 6 × 10 －６ K －１ Scale device.

2. The scale apparatus according to claim 1, wherein the second thermal displacement removal layer is for attaching the scale to the substrate.

3. The scaling apparatus according to claim 2, wherein the second thermal displacement removal layer is for attaching the intermediate member to the substrate.

4. The scaling apparatus according to claim 1, wherein the scale comprises a metal or a metal alloy.

5. The scaling apparatus according to claim 1, wherein the intermediate member includes a metal or a metal alloy.

6. The scaling apparatus according to claim 1, wherein the scale comprises glass or glass ceramic.

7. The scaling apparatus according to claim 6, wherein the intermediate member includes glass or glass ceramic.

8. The scale apparatus according to claim 1, wherein the intermediate member includes carbon fiber.

9. The scale apparatus according to claim 1, wherein the thermal displacement removal structure includes a second intermediate member.

10. The scale apparatus according to claim 9, further comprising a second thermal displacement removal layer for attaching the intermediate member to the second intermediate member.

11. The scale apparatus according to claim 10, wherein the scale comprises a metal or a metal alloy, the intermediate member comprises a metal or a metal alloy, and the second intermediate member comprises carbon fiber.

12. The scaling apparatus according to claim 4, wherein the metal or metal alloy includes an iron-nickel ("FeNi") alloy, and in particular has an alloy composition FeNi 36.

13. The relative stiffness between the scale and the first thermal displacement removal layer is at least 0.33 m －２ The scaling apparatus according to claim 1.

14. The relative stiffness between the intermediate member and the second thermal displacement removal layer is at least 0.33 m －２ The scaling apparatus according to claim 2.

15. The scaling device according to claim 1, wherein the scaling device is attached to a substrate.

16. The scale device according to claim 14, wherein the scale device is attached to the substrate by a thermal displacement removal layer that adheres the intermediate member of the thermal displacement removal structure to the substrate.

17. The scale device according to claim 15, wherein the intermediate member of the thermal displacement removal structure, which is directly adjacent to the substrate, is fixed to the substrate by at least one mechanical fastener, thereby attaching the scale device to the substrate.

18. The scaling apparatus according to claim 17, wherein the at least one mechanical fastener acts to fix the intermediate member to the substrate.

19. The scaling apparatus according to claim 17 or 18, wherein there is no adhesive and / or thermal displacement removal layer between the intermediate member and the substrate.

20. The scale apparatus according to claim 17, wherein the second intermediate member is an intermediate member of the thermal displacement removal structure that is directly present on the substrate and on which the mechanical fastener acts.

21. A scale device for a measuring encoder, the scale device comprising a scale and a thermal displacement removal structure, the thermal displacement removal structure comprising a first intermediate member and a first thermal displacement removal layer for attaching the scale to the first intermediate member, and a second intermediate member and a second thermal displacement removal layer for attaching the first intermediate member to the second intermediate member.

22. The scale apparatus according to claim 21, wherein the scale comprises a metal or metal alloy, the intermediate member comprises a metal or metal alloy, and the second intermediate member comprises carbon fiber.

23. The scaling apparatus according to claim 22, wherein the scale comprises, in particular, an iron-nickel ("FeNi") alloy having the alloy composition FeNi36.

24. A scale device for a measuring encoder, comprising a scale and a thermal displacement removal structure, wherein the thermal displacement removal structure includes an intermediate member and a first thermal displacement removal layer for attaching the scale to the intermediate member, and the relative rigidity of the scale and the first thermal displacement removal layer is at least 0.33 m －２ This is a scaling device.

25. A scale device for a measuring encoder, the scale device comprising a metal or metal alloy scale and a thermal displacement removal structure, the thermal displacement removal structure including an intermediate member, a first thermal displacement removal layer and a second thermal displacement removal layer, the first thermal displacement removal layer for attaching the scale to the intermediate member, and the intermediate member comprising a metal or metal alloy.

26. A measuring scale comprising a scale support layer and an adhesive layer, wherein the scale support layer contains a material having a thickness of 50 μm to 1000 μm and a coefficient of thermal expansion of －６ K －１ or less, and the shear modulus of the adhesive layer is 20 kPa or less. Measuring scale.

27. A measuring scale comprising a scale support layer and an adhesive layer, wherein the scale bearing layer has a thickness of 50 μm to 1000 μm and 2 × 10 －６ K －１ A measuring scale comprising a material having the following CTE, wherein, when mounted on a substrate, the thermal expansion behavior of the scale support layer is governed by the properties of the scale support layer.

Images