Scale

Abstract

A scale arrangement for a measurement encoder is disclosed, the scale arrangement comprising a scale (202) and a thermal displacement release structure (212). The thermal displacement release structure (212) includes an intermediate member (206) and a first thermal displacement release layer (204) for attaching the scale (202) to the intermediate member (206). The coefficient of thermal expansion of the intermediate member (206) and the coefficient of thermal expansion of the scale (202) satisfy the following condition:-3 * 10 <-6 > K <-1 > < = CTE (intermediate member)-CTE (scale) < = 6 * 10 <-6 > K <-1 >.

Description

[0001] The invention of the present application relates to a scale, and more particularly to a metrological scale used as part of a measuring encoder.

[0002] A metrological scale is used for position measurement of a moving part of a machine relative to a stationary part. A metrological scale typically has a series of features on it which can be read by a read head so that the read head can provide a measure of its position along the scale. A metrological scale can be mounted to a stationary part or a moving part of a machine and read by a suitable read head attached to the other of the stationary part and the moving part. Types of metrological scales include: magnetic scales (wherein the scale features are provided by features having specific magnetic properties), capacitive scales (wherein the features are provided by features having specific capacitive properties) and optical scales (wherein the features are provided by features having specific optical properties). An optical scale can be transmissive or reflective. An example of an optical scale configuration is disclosed in EP 0207121 and US 4974962.

[0003] It is known to attach metrological scales to parts using adhesives. Typically, the thermal expansion properties of the substrate on which the metrological scale is to be mounted differ from those of the metrological scale. One known method of mounting a scale to a substrate involves subjecting the scale to the substrate. In this method, the scale is fixed to the substrate so that the expansion and contraction of the scale is determined by the expansion and contraction of the substrate, i.e. the scale is mounted so that expansion and contraction of the substrate (e.g. thermal expansion) is transferred to the scale as much as possible.

[0004] In WO 2010 / 004248, a metrological scale is held against a substrate by a scale track. The disclosed track allows the metrological scale to expand and contract due to temperature changes substantially independently of the substrate.

[0005] JP H05269650 discloses an arrangement in which it is intended to prevent a decrease in position detection accuracy due to thermal expansion of a base material by mounting a main scale on a mounting member using an elastic material which decreases in volume when hardened and which maintains elasticity even after hardening.

[0006] US 7007397 discloses a glass fiber epoxy board scale which is mounted to a metal strip by 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 strip. The metal strip is mounted to a substrate via a release structure to cope with thermal displacement.

[0007] According to a first aspect of the present invention, there is provided a scale arrangement for measuring an encoder, the scale arrangement comprising a scale and a thermal displacement release structure, the thermal displacement release structure comprising an intermediate member, a first thermal displacement release layer and a second thermal displacement release layer, the first thermal displacement release layer being used to attach the scale to the intermediate member, wherein the thermal expansion coefficient of the intermediate member and the thermal expansion coefficient of the scale meet the following conditions:

[0008] -3×10 -6 K -1 ≤CTE(intermediate component)–CTE(scale)≤6×10 -6 K -1 .

[0009] By providing such a scale arrangement, the influence of thermal expansion behavior of a substrate on which the scale arrangement may be positioned may be reduced. This may improve the scale behavior during temperature changes.

[0010] Optionally, the thermal expansion coefficient of the intermediate member and the thermal expansion coefficient of the ruler meet the following conditions:

[0011] -2×10 -6 K -1 ≤CTE(intermediate component)-CTE(scale)≤2×10 -6 K -1 , optionally: -2×10 -6 K -1 ≤CTE(intermediate component)–CTE(scale)≤1.6×10 -6 K -1 , for example: -1×10 -6 K -1 ≤CTE(intermediate component)–CTE(scale)≤1×10 -6 K -1

[0012] Optionally, the thermal expansion coefficient of the intermediate member and the thermal expansion coefficient of the ruler meet the following conditions:

[0013] -0.2×10 -6 K -1 ≤CTE(intermediate component)–CTE(scale)≤0.2×10 -6 K -1

[0014] Optionally, the thermal displacement relief structure is used to attach the scale to the substrate. Optionally, the thermal expansion coefficient of the intermediate member is the intrinsic thermal expansion coefficient of the material the intermediate member comprises. Optionally, the thermal expansion coefficient of the scale is the intrinsic thermal expansion coefficient of the material the scale comprises.

[0015] Optionally, the second heat displacement release layer is used to attach the scale to the substrate, for example via an intermediate member. Optionally, the second heat displacement release layer is used to attach the intermediate member to the substrate.

[0016] Optionally, the first heat displacement release layer and / or the second heat displacement release layer exhibit elastic response, such as elastic response to shearing that may be caused by thermal expansion (e.g., in the case of the first heat displacement release layer, thermal expansion of the ruler and / or the intermediate member). Optionally, the first heat displacement release layer and / or the second heat displacement release layer are elastically deformable. Optionally, the first heat displacement release layer couples the ruler to the intermediate member. Optionally, the ruler is fastened to the intermediate member by the first heat displacement release layer. Optionally, the first heat displacement release layer and / or the second heat displacement release layer include adhesive tape. Optionally, the first heat displacement release layer and / or the second heat displacement release layer resist lateral movement of the ruler and / or the intermediate member, for example, the first heat displacement release layer can resist lateral movement of the ruler relative to the intermediate member, which can include lateral movement of the ruler relative to the intermediate member in a direction that is orthogonal to both the measurement direction of the ruler and the direction of the measurement surface of the ruler normal to the ruler. Optionally, the first heat displacement release layer and the second heat displacement release layer have the same thickness. Alternatively, the first heat displacement release layer and the second heat displacement release layer have different thicknesses, for example, the second heat displacement release layer can be thicker than the first heat displacement release layer. The first heat displacement release layer and the ruler can have the same width. The first heat displacement release layer and the intermediate member can have the same width. The width of the first heat displacement release layer can be less than the width of the ruler. The width of the first heat displacement release layer can be less than the width of the intermediate member. The second heat displacement release layer and the intermediate member can have the same width. The width of the second heat displacement release layer can be less than the width of the intermediate member. The first heat displacement release layer and the second heat displacement release layer can have the same width. Alternatively, the first heat displacement release layer and the second heat displacement release layer can have different widths, for example, the width of the first heat displacement release layer can be greater than the width of the second heat displacement release layer. The first heat displacement release layer and the second heat displacement release layer can include an integral adhesive layer (e.g., an adhesive tape), optionally, wherein the first heat displacement release layer includes a first region of the integral adhesive layer that attaches the ruler to the intermediate member, and the second heat displacement release layer includes a second region of the integral adhesive layer for attaching the intermediate member to the substrate.

[0017] Optionally, the ruler comprises a metal or metal alloy. Optionally, the intermediate member comprises a metal or metal alloy. Optionally, the ruler and the intermediate member comprise the same metal or metal alloy. The metal or metal alloy may comprise an iron-nickel ("FeNi") alloy, such as the alloy composition FeNi36. Optionally, the ruler comprises a glass or glass ceramic. Optionally, the intermediate member comprises a glass or glass ceramic. Optionally, the ruler and the intermediate member comprise the same glass or glass ceramic. Optionally, the intermediate member comprises carbon fiber. Optionally, the ruler arrangement is attached to the substrate. Optionally, the ruler arrangement is attached to the substrate via the intermediate member. Optionally, the intermediate member is attached to the substrate via a second thermal displacement release layer. Optionally, the intermediate member is attached to the substrate via one or more clamps / clamps or other mechanical constraints / fasteners (such as the FASTRACK system available from Renishaw plc). The CTE of the intermediate member may be between the CTE of the ruler and the CTE of the substrate, but of course this is not necessarily the case.

[0018] Optionally, the first heat displacement release layer is an adhesive layer. Optionally, the first heat displacement release layer is an adhesive layer for attaching the scale to the intermediate member. Optionally, the second heat displacement release layer is an adhesive layer. Optionally, the second heat displacement release layer is an adhesive layer for attaching the intermediate member to the substrate.

[0019] Optionally, the first heat displacement release layer comprises an adhesive tape. Optionally, the second heat displacement release layer comprises an adhesive tape. Optionally, the heat displacement release layers each comprise an adhesive tape. The adhesive tape may be a carrier tape having an adhesive layer disposed on each of the two faces.

[0020] Optionally, the heat displacement release structure includes more than one intermediate member. Optionally, the second heat displacement release layer is an adhesive layer that attaches the first intermediate member to the second intermediate member. Optionally, the third heat displacement release layer is an adhesive layer. Optionally, the third heat displacement release layer is an adhesive layer for attaching the second intermediate member to the substrate. Optionally, the second intermediate member is attached to the substrate via one or more clamps / clamps or other mechanical constraints / fasteners.

[0021] The scale arrangement may be attached to the substrate by a heat displacement release layer which adheres an intermediate member of the heat displacement release structure (eg the aforementioned intermediate member or, if present, a second intermediate member) to the substrate.

[0022] The heat displacement intermediate member (e.g., the aforementioned intermediate member or (if present) the second intermediate member) directly adjacent to the substrate may be fastened to the substrate (thereby attaching the scale arrangement to the substrate) by at least one mechanical fastener. At least one mechanical fastener may be used to clamp the intermediate member (e.g., the aforementioned intermediate member or (if present) the second intermediate member) against the substrate. Optionally, there is no adhesive and / or heat displacement release layer between the intermediate member and the substrate.

[0023] According to a second aspect of the present invention, there is provided a scale arrangement for measuring an encoder, the scale arrangement comprising a metal or metal alloy scale and a thermal displacement release structure, the thermal displacement release structure comprising an intermediate member and a first thermal displacement release layer for attaching the scale to the intermediate member, wherein the intermediate member comprises a metal or metal alloy, and the thermal displacement release structure optionally comprises a second thermal displacement release layer for attaching the intermediate member to a substrate.

[0024] According to a third aspect of the invention, there is provided a scale arrangement comprising a scale and a thermal displacement release structure, the thermal displacement release structure comprising a first intermediate member and a first thermal displacement release layer and a second intermediate member and a second thermal displacement release layer, the first thermal displacement release layer being used to attach the scale to the first intermediate member, the second thermal displacement release layer being used to attach the first intermediate member to the second intermediate member. The scale may comprise a metal or a metal alloy. The intermediate member may comprise a metal or a metal alloy. The scale may comprise an iron-nickel ("FeNi") alloy, in particular an alloy composition FeNi36. The second intermediate member may comprise carbon fiber.

[0025] According to a fourth aspect of the present invention, there is provided a scale arrangement for measuring an encoder, the scale arrangement comprising a scale and a thermal displacement release structure, the thermal displacement release structure comprising an intermediate member and a first thermal displacement release layer, the first thermal displacement release layer being used to attach the scale to the intermediate member, wherein the relative stiffness of the scale and the first thermal displacement release layer is at least 0.33 m -2 .

[0026] According to a fifth aspect of the present invention, there is provided a metrological scale, which comprises a scale bearing layer and an adhesive layer, wherein the scale bearing layer comprises a thickness of 50 μm to 1000 μm and a thermal expansion coefficient of not more than 2×10 -6 K -1 The material of the adhesive layer has a shear modulus of no more than 20 kPa. Optionally, the scale is a linear scale.

[0027] According to a sixth aspect of the present invention, there is provided a metrological scale, which comprises a scale bearing layer and an adhesive layer, wherein the scale bearing layer comprises a thickness of 50 μm to 1000 μm and a thermal expansion coefficient of not more than 2×10-6 K -1 and wherein the thermal expansion behavior of the scale-bearing layer when mounted to the substrate is governed by the properties of the scale-bearing layer. Optionally, the thermal expansion coefficient of the substrate is 5×10 -6 K -1 Up to 25×10 -6 K -1 .

[0028] Optionally, the substrate is granite, or iron, or steel, or aluminum. Optionally, the thermal expansion characteristics of the substrate are between the thermal expansion characteristics of granite and the thermal expansion characteristics of aluminum.

[0029] Optionally, the scale bearing layer comprises a nickel iron alloy. The scale bearing layer may comprise FeNi36 (sometimes referred to as 64FeNi and sold as Invar (RTM)). Optionally, the scale bearing layer has a thickness of no more than 900 μm, optionally no more than 800 μm, optionally no more than 700 μm, optionally no more than 600 μm, optionally no more than 500 μm, optionally no more than 400 μm, optionally no more than 300 μm, optionally no more than 200 μm. Optionally, at least 100 μm. Optionally, the adhesive layer has a thickness of no more than 0.2 mm.

[0030] According to a seventh aspect of the present invention, there is provided a measuring encoder comprising a read head and a scale according to the fifth aspect or the sixth aspect.

[0031] According to an eighth aspect of the present invention, there is provided a machine comprising a scale according to the fifth or sixth aspect or an encoder according to the seventh aspect. Optionally, the machine comprises a CMM or a machine tool, display manufacturing equipment, or semiconductor processing equipment.

[0032] Optionally, the adhesive layer is attached directly to the machine.

[0033] According to a ninth aspect of the present invention, there is provided a measuring encoder comprising a read head and a scale mounted to a substrate via an adhesive, wherein the adhesive is arranged on a surface of the scale facing the read head. Optionally, a gap is provided between the scale and the substrate. The scale may be mounted to the substrate via a height control element.

[0034] By providing a measuring encoder comprising a readhead and a scale mounted to a substrate via an adhesive, wherein the adhesive is arranged on the face of the scale facing the readhead, the height of the face of the scale facing the readhead relative to the substrate can be maintained even if the adhesive swells.

[0035] Features in one aspect may be combined in other aspects.

[0036] A scale arrangement for measuring an encoder is also disclosed. The scale arrangement may include a scale and a thermal displacement release structure. The thermal displacement release structure may include an intermediate member and a first thermal displacement release layer for attaching the scale to the intermediate member. The thermal displacement release structure may include a second thermal displacement release layer. For the thermal expansion coefficients of the intermediate member and the scale, the following may be true:

[0037] -3×10 -6 K -1 ≤CTE(intermediate component)–CTE(scale)≤6×10 -6 K -1 .

[0038] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0039] Figure 1(a) shows a prior art arrangement in which a scale is adhered to a substrate;

[0040] FIG. 1( b ) shows the prior art arrangement of FIG. 1( a ) at a higher temperature;

[0041] Figure 2 A first scale arrangement mounted on a substrate is shown;

[0042] Figure 3 An embodiment of a scale system mounted on a substrate is shown;

[0043] Figure 4 A second scale arrangement mounted on a substrate is shown;

[0044] Figure 5 A third scale arrangement mounted on a substrate is shown;

[0045] Figure 6 A fourth scale arrangement is shown;

[0046] as well as

[0047] Figure 7 A fifth scale arrangement is shown mounted on a substrate.

[0048] FIG1( 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 axis of elongation E. In use, the axis of elongation E coincides with the measurement direction. In this case, the substrate 110 may be aluminum, which has a coefficient of thermal expansion (CTE) of 21×10 -6 K -1 Up to 24×10 -6 K -1 In this case, the metrological scale 102 has a CTE of about 10×10-6 K -1 of steel.

[0049] This means that for a 1 K rise in temperature, a steel ruler will expand by 10 μm per meter of scale, whereas an aluminium substrate will expand by up to 24 μm per meter. For every 1 K change in temperature, the ruler will want to increase in length by 14 μm less per meter of scale than the aluminium substrate. It will be appreciated that this difference will be greater in absolute terms the longer the ruler length and / or the greater the temperature change.

[0050] FIG. 1( b) shows the arrangement of FIG. 1( a) at a second temperature higher than the first temperature. In this case, both the metrological scale 102 and the substrate 110 have expanded due to the temperature increase. In the example where the substrate 110 is an aluminum substrate 110 and the scale 102 is a steel scale 102, the CTE of the aluminum substrate 110 is higher than the CTE of the steel scale 102, and therefore the amount of expansion of the aluminum substrate 110 is greater than the amount of expansion of the steel scale 102. As the temperature increases, both the substrate 110 and the metrological scale 102 expand, however, due to the connection through the adhesive layer 104, the expansion of the metrological scale 102 is affected by the expansion of the substrate 110. This causes the effective CTE of the steel scale 102 to change compared to the intrinsic CTE of the steel scale 102 (i.e., the CTE caused by the temperature change alone). In this case, because the extent to which the substrate 110 expands due to thermal expansion exceeds the extent to which the steel scale 102 expands due to thermal expansion, the effective CTE of the steel scale 102 increases relative to the intrinsic CTE of the steel scale 102. It has been found that for a CTE of 24×10 -6 K -1 The aluminum substrate 110 is 3 m long (thermal reference plane to free end), 8 mm wide (in the dimension parallel to the surface of the substrate 110), and 0.2 mm thick (in the dimension normal to the surface of the substrate 110). The steel ruler 102 (whose intrinsic CTE is 10×10 -6 K -1 ), and the thickness of the adhesive layer is 0.2 mm, the width is 6 mm, and the shear modulus is 1 kNm -2 In this case, the effective CTE of the steel ruler 102 is 12.8×10 -6 K -1 .

[0051] The effect of substrate 110 (transmitted through adhesive layer 104) on metrological scale 102 depends, among other things, on the difference between the CTE of metrological scale 102 and the CTE of substrate 110, which may introduce a degree of unpredictability. For example, substrate 110 need not be aluminum, but could be granite. Since the CTE of granite is typically 7.8×10 -6 K -1 to 8.4×10 -6 K -1 , it will be appreciated that the effects on the metrological scale 102 caused by thermal expansion of the substrate 110 will be different for a granite substrate 110 as compared to an aluminum substrate 110. In fact, because the CTE of granite is lower than the CTE of steel, the effective CTE change of the steel metrological scale 102 caused by the granite substrate 110 will be negative (i.e., a compressive force will be applied) because the steel will expand more than the granite substrate 110 due to the increase in temperature.

[0052] Therefore, it may not always be possible to know the magnitude or even the direction of any error introduced into the measurement arrangement due to CTE mismatch between the scale and the substrate.

[0053] Figure 2 An exemplary embodiment of a scale arrangement 200 according to the present invention is shown. The scale arrangement 200 comprises a scale 202. Figure 2 In the illustrated scale arrangement 200, the scale 202 is attached to the substrate 210 via a heat displacement release structure 212. The heat displacement release structure 212 includes a first adhesive layer 204, an intermediate member 206, and a second adhesive layer 208.

[0054] In this embodiment, the scale 202 is a metrological scale 202 . Figure 2 The scale 202 is an elongated scale 202 having an axis of elongation E. In use, the axis of elongation E coincides with the measurement direction. The scale 202 has markings that can be read by a read head in order to determine relative position. In this embodiment, the scale 202 is a steel scale 202.

[0055] Figure 2 The intermediate member 206 of the exemplary embodiment shown is identical to the scale 202, but may not have markings that can be read by the readhead. In this embodiment, the intermediate member 206 is made of the same material as the scale 202 and has the same dimensions (width, height, length) as the scale 202.

[0056] In this embodiment, Figure 2The first adhesive layer 204 and the second adhesive layer 208 shown are identical and include adhesive tape. The adhesive tape may be a carrier tape provided with an adhesive layer on each of the two faces. The second adhesive layer 208 is non-rigid and can be deformed under the effect of a force (such as shear force) applied to the first interface (such as between the substrate 210 and the second adhesive layer 208) due to the expansion of the substrate 210 caused by temperature changes. In this case, if the shear modulus of the material is low, the material can be considered as non-rigid. In this embodiment, an adhesive tape that can be elastically stretched is used. The shear modulus of the adhesive tape is 1.2 kPa. At the second interface (such as between the second adhesive layer 208 and the intermediate member 206), due to the expansion of the intermediate member 206 caused by temperature changes, force is also applied. If the expansion of the substrate 210 and the expansion of the intermediate member 206 are not the same, the second adhesive layer 208 will apply shear force to the intermediate member 206 due to the differential expansion of the substrate 210, which will affect 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 under the action of the force (such as shear force) that occurs due to the expansion of the intermediate member 206, thereby causing the first adhesive layer to deform at the third interface (such as between the intermediate member 206 and the first adhesive layer 204). In this embodiment, an adhesive tape that can be elastically stretched is used. The shear modulus of the adhesive tape is 1.2kPa. In the current embodiment, the intermediate member may have expanded due to temperature changes and the force generated by the differential thermal expansion of the substrate 210. The ruler 202 will also have expanded due to temperature changes. If the expansion of the ruler 202 due to temperature changes is different from the expansion of the intermediate member 206, the ruler 202 will also be subjected to force (such as shear force) at the fourth interface (such as between the first adhesive layer 204 and the ruler 202). The force acting on the ruler 202 due to the differential expansion of the ruler 202 and the intermediate member 206 will affect the deformation behavior of the ruler 202.

[0057] For embodiments in which the scale 202 is a steel scale 202 and the intermediate member 206 is a steel intermediate member 206, and where this embodiment is located on an aluminum substrate 210, it will be understood that as the temperature of the scale arrangement 200 and the substrate 210 changes, the difference in CTE values ​​of the steel scale 202, the steel intermediate member 206, and the aluminum substrate 210 causes the aluminum substrate 210 to thermally expand to different degrees than the steel scale 202 and the steel intermediate member 206.

[0058] If the temperature of the scale arrangement 200 and the substrate 210 increases, the aluminum substrate 210 will thermally expand to a greater extent than the steel intermediate member 206 or the steel scale 202. When the aluminum substrate 210 expands, the second adhesive layer 208 deforms at the interface of the aluminum substrate 210 and the second adhesive layer 208, causing a shear force to be applied at the interface between the second adhesive layer 208 and the steel intermediate member 206. This shear force caused by the differential thermal expansion of the intermediate member 206 and the substrate 210 causes the steel intermediate member 206, which expands due to the temperature increase, to expand further. In this embodiment, the effective CTE of the steel intermediate member 206 is therefore higher than the intrinsic CTE of the material used to manufacture the intermediate member 206. Since the steel intermediate member 206 has expanded, the first adhesive layer 204 deforms at the interface of the steel intermediate member 206 and the first adhesive layer 204, causing a shear force to be applied at the interface between the first adhesive layer 204 and the steel scale 202. This shear force caused by the differential thermal expansion of the steel scale 202 and the steel intermediate member 206 causes the steel scale 202 to further expand. In this embodiment, the effective CTE of the steel scale 202 is therefore higher than the intrinsic CTE of the material from which the scale 202 is made, but lower than the effective CTE it would have if it were directly attached to a substrate.

[0059] For the first embodiment as follows, it includes a steel scale 202 (whose intrinsic CTE is 10×10 -6 K -1 ) and a steel intermediate member 206 (whose intrinsic CTE is 10×10 -6 K -1 ), and wherein the first adhesive layer 204 and the second adhesive layer 208 are 0.2 mm thick, 6 mm wide and have a shear modulus of 1 kNm -2 The adhesive tape of the first embodiment is located at a CTE of 24×10 -6 K -1 When the steel ruler 202 is placed on the aluminum substrate 210, the effective CTE is 10.56×10 -6 K -1 .

[0060] It can be seen that by introducing the steel intermediate member 206, the deviation of the CTE of the steel scale 202 from the intrinsic CTE of the material from which the steel scale 202 is made has been reduced compared to the example described above with respect to the steel scale 102 of FIG. 1. In other words, the behavior of the scale 202 has been improved because the effects of differential expansion of the substrate and the scale have been reduced. By introducing the steel intermediate member 206, the effective CTE has been reduced by 2.24×10 -6 K -1 .

[0061] A first embodiment of the scale arrangement may be located on different substrates, for example on a substrate having an intrinsic CTE of 8×10 -6 K -1 on granite substrate.

[0062] For the first embodiment as follows, it includes a steel scale 202 (whose intrinsic CTE is 10×10 -6 K -1 ) and a steel intermediate member 206 (whose intrinsic CTE is 10×10 -6 K -1 ), and wherein the first adhesive layer 204 and the second adhesive layer 208 are 0.2 mm thick, 6 mm wide and have a shear modulus of 1 kNm -2 The adhesive tape of the first embodiment is located at a CTE of 8×10 -6 K -1 When the steel ruler 202 is placed on the granite substrate 210, the effective CTE is 9.9×10 -6 K -1 .

[0063] As can be seen from applying the first embodiment to an aluminum substrate and a granite substrate, in both cases the behavior of the steel ruler when the temperature changes is closer to floating behavior than to controlled behavior. Pure floating behavior means that the thermal changes in temperature are not dominated by the substrate, in other words, the effective CTE of the ruler 202 will be the same as the intrinsic CTE of the material used to make the ruler 202. Controlled behavior means that the ruler is attached to the substrate so that the thermal behavior of the ruler is dominated by the thermal behavior of the substrate. If the ruler is completely dominated by the substrate, the effective CTE of the ruler will be equal to the intrinsic CTE of the material of the substrate.

[0064] For the second embodiment as follows, it includes a low expansion iron-nickel ("FeNi") alloy (having an alloy composition of FeNi36 and commonly known by the trade name Invar (RTM)) scale 202 (whose intrinsic CTE is 1.0×10 -6 K -1 ) and a low expansion FeNi alloy intermediate member 206 (whose intrinsic CTE is 1.0×10 -6 K -1 ), and wherein the first adhesive layer 204 and the second adhesive layer 208 are 0.2 mm thick, 6 mm wide and have a shear modulus of 1 kNm -2 The second embodiment of the adhesive tape is located at a CTE of 24×10 -6 K -1 When the aluminum substrate 210 is formed, the effective CTE of the low expansion FeNi alloy ruler 202 is 2.68×10 -6 K -1 This is in contrast to the following: when a low expansion FeNi alloy ruler of the same size is mounted on a 24×10 -6 K -1 When the aluminum substrate is used, the effective CTE is 7.21×10 -6 K -1 By introducing the low expansion FeNi alloy intermediate component 206, the effective CTE is reduced by 4.53×10 -6 K -1 .

[0065] When the second embodiment is located at a CTE of 8×10 -6 K -1 When the low expansion FeNi alloy ruler 202 of the second embodiment is placed on the granite substrate 210, the effective CTE is 1.51×10 -6 K -1 This is in contrast to the following: when a low expansion FeNi alloy ruler of the same size is mounted on a CTE of 8 × 10 -6 K -1 When the granite substrate is used, the effective CTE is 2.89×10 -6 K -1By introducing the low expansion FeNi intermediate component 206, the effective CTE is reduced by 1.38×10 -6 K -1 .

[0066] Although the first and second embodiments include a scale 202 and an intermediate member 206 made of the same material and thus have substantially the same intrinsic CTE (within + / - 3×10 -6 K -1 However, the present invention can also be implemented 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.

[0067] Embodiments of the present invention may include a scale arrangement in which the intrinsic CTE of the scale 202 is between the intrinsic CTE of the intermediate member 206 and the intrinsic CTE of the substrate 210 to which the scale arrangement 200 is intended to be mounted. Such a scale arrangement may work well when the intermediate member 206 is disturbed by the substrate 210. The disturbed intermediate member 206 may then better match the expansion of the scale 202 than would be achievable if the scale 202 and the intermediate member 206 had substantially similar intrinsic CTE values.

[0068] For the third embodiment as follows, it includes a steel scale 202 (whose intrinsic CTE is 10×10 -6 K -1 ) and a titanium intermediate member 206 (whose intrinsic CTE is 8×10 -6 K -1 ), and 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 modulus of 1 kPa, when the third embodiment is located at a CTE of 24×10 -6 K -1 When the steel ruler 202 is placed on the aluminum substrate 210, the effective CTE is 10.59×10 -6 K -1 This is in contrast to the following: when a steel ruler of the same size is mounted on a 24×10 -6 K -1When the aluminum substrate is used, the effective CTE is 12.8×10 -6 K -1 By introducing the titanium intermediate member 206, the effective CTE is reduced by 2.24×10 -6 K -1 .

[0069] Embodiments of the present invention may include a scale arrangement in which the intrinsic CTE of the intermediate member 206 is between the intrinsic CTE of the scale 202 and the intrinsic CTE of the substrate 210 to which the scale arrangement 200 is intended to be mounted, but this need not be the case.

[0070] For the fourth embodiment as follows, it includes a steel scale 202 (whose intrinsic CTE is 10×10 -6 K -1 ) and 3 series of intermediate members 206 (whose intrinsic CTE is 16×10 -6 K -1 ), and 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 modulus of 1 kPa, when the fourth embodiment is located at a CTE of 24×10 -6 K -1 When the steel ruler 202 is placed on the aluminum substrate 210, the effective CTE is 11.54×10 -6 K -1 This is in contrast to the following: when a steel ruler of the same size is mounted on a sheet with a CTE of 24 × 10 -6 K -1 When the aluminum substrate is used, the effective CTE is 12.8×10 -6 K -1 By introducing the 3 series steel intermediate member 206, the effective CTE is reduced by 1.26×10 -6 K -1 .

[0071] For the fifth embodiment as follows, it includes a low expansion FeNi alloy (sold as Invar (RTM)) ruler 202 (whose intrinsic CTE is 1×10 -6 K -1 ) and a carbon fiber intermediate member 206 (whose intrinsic CTE is -1×10 -6 K -1 ), and 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 modulus of 1 kPa, when the fifth embodiment is located at a CTE of 24×10 -6 K -1 When the aluminum substrate 210 is formed, the effective CTE of the low expansion FeNi alloy ruler 202 is 0.58×10 -6 K -1 This is in contrast to the following: when a low expansion FeNi alloy ruler of the same size is mounted on a CTE of 24 × 10 -6 K -1 When the aluminum substrate is used, the effective CTE is 7.2×10 -6 K -1 By introducing the carbon fiber intermediate member 206, the effective CTE is reduced by 6.7×10 -6 K -1 .

[0072] When the fifth embodiment is located at a CTE of 8×10 -6 K -1 When the steel scale 202 of the fifth embodiment is placed on the granite substrate 210, the effective CTE is 0.50×10 -6 K -1 This is in contrast to the following: when a steel ruler of the same size is mounted on a sheet with a CTE of 8 × 10 -6 K -1 When the granite substrate is used, the effective CTE is 2.90×10 -6 K -1 By introducing the carbon fiber intermediate member 206, the effective CTE is reduced by 2.40×10 -6 K -1 .

[0073] For the sixth embodiment as follows, it comprises a low expansion glass ceramic scale 202 (sold by Schott (RTM) as Robax (RTM), which has an intrinsic CTE of 0.5×10 -6 K -1 ) and a low expansion glass ceramic intermediate member 206 (sold as Robax (RTM) having an intrinsic CTE of -0.5×10 -6 K -1 ), and wherein the first adhesive layer 204 and the second adhesive layer 208 are adhesive tapes with a shear modulus of 1.2 kPa, when the sixth embodiment is located at a CTE of 8×10 -6 K -1 When the Robax (RTM) ruler 202 is placed on the granite substrate 210, the effective CTE is 0.48×10 -6 K -1 This is in contrast to the following: when a Robax ruler of the same size is mounted on a sheet with a CTE of 8 × 10 -6 K -1 When the granite substrate is used, the effective CTE is 0.66×10 -6 K -1 By introducing Robax (RTM) intermediate component 206, the effective CTE is reduced by 0.18×10 -6 K -1 .

[0074] One factor that may affect the extent to which the scale 202 is disturbed by the mismatch between the CTE of the scale 202 and the CTE of the substrate 210 on which the scale arrangement 200 is located is the stiffness of the intermediate member 206. As discussed above, as the temperature increases, the substrate 210 expands, causing forces to be transmitted through the second adhesive layer 208, which may (in the case where the intrinsic CTE of the substrate 210 is higher than the CTE of the intermediate member 206) cause the intermediate member 206 to stretch. As the stiffness of the intermediate member 206 increases, the disturbance caused by the mismatch in the intrinsic CTE values ​​of the substrate 210 and the intermediate member 206 decreases.

[0075] For the seventh embodiment as follows, it includes a steel scale 202 (whose intrinsic CTE is 10×10 -6 K -1 ) and a titanium intermediate member 206 (whose intrinsic CTE is 8×10 -6 K -1 ), and 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 modulus of 1 kPa, when the seventh embodiment is located at a CTE of 24×10 -6 K -1 When the steel ruler 202 is placed on the aluminum substrate 210, the effective CTE is 11.1×10 -6 K -1 This is in contrast to the following: when a steel ruler of the same size is mounted on a 24×10 -6 K -1 When the aluminum substrate is used, the effective CTE is 12.8×10 -6 K -1 By introducing the titanium intermediate member 206, the effective CTE is reduced by 1.77×10 -6 K -1 .

[0076] The difference between the third embodiment and the seventh embodiment is the thickness of the titanium intermediate member 206 (in the dimension normal to the surface of the substrate 210). The thickness of the titanium intermediate member 206 of the seventh embodiment is half the thickness of the titanium intermediate member 206 of the third embodiment (in the dimension normal to the surface of the substrate 210), so the stiffness of the titanium intermediate member of the seventh embodiment is also halved. The third embodiment achieves an effective CTE reduction of 2.24×10 -6 K -1 , while the seventh embodiment achieves an effective CTE reduction of 1.76×10 -6 K -1 It can therefore be seen that the stiffness of the intermediate member 206 can be used to tune the behavior of the scale 202 .

[0077] For the eighth embodiment as follows, it comprises a low expansion inorganic non-porous lithium aluminum silicon oxide glass ceramic scale 202 (sold as Zerodur (RTM) with an intrinsic CTE of 0×10 -6 K -1 ) and an Invar (RTM) intermediate member 206 (whose intrinsic CTE is 1×10 -6 K -1 ), and 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 modulus of 1 kPa, when the eighth embodiment is located at a CTE of 8×10 -6 K -1 When the Zerodur (RTM) ruler 202 is placed on a granite substrate 210, the effective CTE is 0.048×10 -6 K -1 This is in contrast to the following: when a Zerodur (RTM) ruler of the same size is mounted on a CTE of 8 × 10 -6 K -1 When the granite substrate is used, the effective CTE is 0.17×10 - 6 K -1 By introducing Invar intermediate member 206, the effective CTE is reduced by 0.13×10 -6 K -1 . The effective CTE is reduced by 70%.

[0078] For the ninth embodiment as follows, it comprises a glass ceramic scale 202 (sold as Zerodur (RTM) with an intrinsic CTE of 0×10 -6 K -1 ) and an Invar (RTM) intermediate member 206 (whose intrinsic CTE is 1×10-6 K -1 ), and 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 modulus of 1 kPa, when the ninth embodiment is located at a CTE of 8×10 -6 K -1 When the Zerodur (RTM) ruler 202 is placed on a granite substrate 210, the effective CTE is 0.114×10 -6 K -1 This is in contrast to the following: when a Zerodur (RTM) ruler of the same size is mounted on a CTE of 8 × 10 -6 K -1 When the granite substrate is used, the effective CTE is 0.17×10 -6 K -1 By introducing the Invar (RTM) intermediate component 206, the effective CTE is reduced by 0.06×10 -6 K -1 . The effective CTE was reduced by 34%.

[0079] For the eighth embodiment, the value of the stiffness of the intermediate member divided by the stiffness of the ruler is 0.104, while in the ninth embodiment, the value of the stiffness of the intermediate member divided by the stiffness of the ruler is 0.0138. It can be seen that even when the stiffness of the intermediate member 206 is much less than the stiffness of the ruler 202, an improvement in the behavior of the ruler member 202 can be achieved.

[0080] Another factor that may affect the performance of the scale arrangement 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 in terms of shear stiffness per unit length, k. The higher the value of k, the more effective the adhesive layer is at generating a force at the second interface for a given expansion of the first interface.

[0081] The shear stiffness per unit length of the adhesive tape can be calculated by multiplying the shear modulus of the adhesive tape by its thickness and then dividing by its width.

[0082] As discussed above, the amount by which intermediate member 206 is disturbed by the expansion of substrate 210 due to CTE mismatch is related to the force generated at the interface between intermediate member 206 and second adhesive layer 208 due to stretching of second adhesive layer 208 at the interface between second adhesive layer 208 and substrate 210. Thus, for a particular situation, the amount by which intermediate member 206 is disturbed is based on the ability of second adhesive layer 208 to generate a force at the second interface due to stretching at the first interface (shear stiffness, k), and based on the extent to which intermediate member 206 is affected by the force (stiffness of intermediate member 206).

[0083] 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 .

[0084] The relative stiffness (R) of the intermediate member 206 and the second adhesive layer 208 can be defined as the stiffness (EA) of the intermediate member 206 divided by the shear stiffness (k) per unit length of the second adhesive layer 208, which relative stiffness generates force at the interface between the second adhesive layer 208 and the intermediate member 206 due to the expansion of the substrate 210.

[0085] R=EA / k

[0086] For example, for the first embodiment, R = 11.2 m -2 .

[0087] For the case where (for the scale 202 and the first adhesive layer 204 or for the intermediate member 206 and the second adhesive layer 208) R = 0.27 m -2 In an embodiment of a 1 m long ruler arrangement, ruler 202 would be midway between floating and controlled (the effective CTE of the ruler would be midway between the intrinsic CTE of the material from which ruler 202 is made and the intrinsic CTE of the material from which substrate 210 is made). For shorter lengths, the effective CTE of ruler 202 would be closer to the intrinsic CTE of the material of the ruler than to the CTE of substrate 210. Longer ruler lengths would exhibit an effective CTE closer to the intrinsic CTE of substrate 210.

[0088] For the case where (for the scale 202 and the first adhesive layer 204 or for the intermediate member 206 and the second adhesive layer 208) R = 1 m -2 For the embodiment of FIG. 2 , the 2 m axis will be midway between floating and controlled, accurate to 1 significant figure. For shorter lengths, the effective CTE of the ruler 202 will be closer to the intrinsic CTE of the ruler's material than to the CTE of the substrate 210 .

[0089] It has been found that for typical ruler lengths, the relative stiffness (R) of the intermediate member 206 and the second adhesive layer 208, or the relative stiffness (R) of the ruler 202 and the first adhesive layer 204, is 0.33 m -2 or greater will provide significant improvement.

[0090] When at least one of the relative rigidity (R) of the intermediate member 206 and the second adhesive layer 208 or the relative rigidity of the ruler 202 and the first adhesive layer 204 is 1 m -2 or greater, a significant improvement in the performance of scale 202 can be seen.

[0091] For the following tenth embodiment, it includes a steel scale 202 (whose intrinsic CTE is 10×10 -6 K -1 ) and a steel intermediate member 206 (whose intrinsic CTE is 10×10 -6 K -1 ), and 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 modulus of 10 kPa (for each layer, R=1 m -2 ), when the tenth embodiment is located at a CTE of 24×10 -6 K -1 When the steel ruler 202 is placed on the aluminum substrate 210, the effective CTE is 10.796×10 -6 K -1 This is in contrast to the following: when a steel ruler of the same size is mounted on a 24×10 -6 K -1 When the aluminum substrate is used, the effective CTE is 13.3×10 -6 K -1 By introducing the steel intermediate member 206, the effective CTE is reduced by 2.54×10 -6 K -1 .

[0092] Although the above embodiments have been described with respect to Figure 2 The scale arrangement shown is described, but other embodiments may include alternative configurations of thermal displacement relief structures for the scale arrangement.

[0093] Figure 3 An exemplary configuration of a scale arrangement 300 according to the present invention is shown. The scale arrangement 300 includes a scale 302. Figure 3 In the illustrated scale arrangement 300, the scale 302 is attached to the substrate 310 via a heat displacement release structure 312. The heat displacement release 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.

[0094] In this embodiment, the scale 302 is a metrological scale 302 . Figure 3 The scale 302 is an elongate scale 302 having an axis of elongation E. In use, the axis of elongation E coincides with the measurement direction. The scale 302 has markings which can be read by a readhead in order to determine relative position.

[0095] Figure 3 The first adhesive layer 304, the second adhesive layer 308 and the third adhesive layer 316 shown are non-rigid and can be stretched. Due to the force (such as shear force) applied by stretching at the first interface (such as between substrate 310 and the third adhesive layer 316) causes force to act on the second interface (such as between the third adhesive layer 316 and the second intermediate member 314). The deformation of the third adhesive layer 316 due to the thermal expansion of substrate 310 and / or the second intermediate member 2 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 heat displacement release layer. The second adhesive layer 308 is a heat displacement release layer. The third adhesive layer is a heat release layer. In this case, if the shear modulus of the material is low, the material can be considered as non-rigid. For example, each of the first adhesive layer 304, and / or the second adhesive layer 308, and / or the third adhesive layer 316 can be an adhesive tape with a shear modulus of 1kPa.

[0096] In a particularly preferred embodiment, the scale arrangement comprises a scale (e.g. 302) and a first intermediate member (e.g. 306), both of which comprise / are made of a low expansion FeNi alloy (having an alloy composition of FeNi36 and commonly referred to as Invar (RTM)), the intrinsic CTE of the low expansion FeNi alloy being 1.0×10 -6 K -1 , and wherein the scale arrangement further comprises a second intermediate member (e.g., 314), the second intermediate member comprising an intrinsic CTE of -1×10 -6 K -1Carbon fiber / made of carbon fiber. According to the embodiment described above, a first thermal displacement layer (e.g., a first adhesive layer 304) is provided between the scale and the first intermediate member, and a second thermal displacement layer (e.g., a 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 mounted to the substrate via the adhesive layer or can be clamped to the substrate. The composite structure of multiple low expansion FeNi layers as described above enables a thinner and therefore cheaper and lighter scale to be made of a low expansion FeNi alloy without sacrificing metrological performance. In addition, the high specific stiffness of carbon fiber contributes to the handling of the FeNi alloy scale, thereby reducing the risk of damage when it is not properly supported during installation, for example. In an optional embodiment, the width of the second intermediate member (i.e., in this embodiment, the carbon fiber layer) can be greater than the width of the layer above it. This may be beneficial for mechanical handling and / or clamping purposes.

[0097] Figure 4 An exemplary configuration of a scale arrangement 400 according to the present invention is shown. Figure 4 In FIG. 4 , the elongated axis E extends into / out of the page. The ruler arrangement 400 includes a ruler 402. Figure 4 In the illustrated scale arrangement 400, the scale 402 is attached to the substrate 410 via a thermal displacement release structure 412. The thermal displacement release structure 412 includes an adhesive layer 404 and an intermediate member 406. Figure 4 The illustrated scale arrangement 400 is elongated and has a measurement direction of elongation perpendicular to the plane of the page.

[0098] In this embodiment, scale 402 is a metrological scale 402 . Figure 4 The ruler 402 is an elongated ruler 402 . Figure 4 A cross section of the scale is shown orthogonal to the axis of elongation of the scale 402. In use, the axis of elongation coincides with the measurement direction. The scale 402 has markings which can be read by a readhead in order to determine relative position.

[0099] Figure 4 The adhesive layer 404 shown is non-rigid and can be stretched, that is, due to the force (such as shear force) applied by stretching at the first interface (such as between the intermediate member 406 and the adhesive layer 404) causing the force to act on the second interface (such as between the adhesive layer 404 and the ruler 402). The deformation of the adhesive layer 404 due to the thermal expansion of the intermediate member 406 and / or the ruler 402 is elastic. The adhesive layer 404 is a heat displacement release layer. In this case, if the shear modulus of the material is low, the material can be considered as non-rigid. Here, the adhesive tape can be elastically stretched. For example, the shear modulus of the adhesive tape forming the first adhesive layer 404 can be 1kPa.

[0100] Clamps 408 are located on each side of the scale arrangement 400 and, in use, hold the intermediate member 406 against the substrate.

[0101] exist Figure 4 In the configuration shown, a mismatch between the intrinsic CTE of the substrate 410 and the intrinsic CTE of the intermediate member 406 may cause the effective CTE of the intermediate member 406 to be different from the intrinsic CTE of the intermediate member 406 due to friction between the intermediate member 406 and the substrate and / or friction between the intermediate member 406 and the clamp 408. These friction forces may occur when the substrate 410 and the intermediate member 406 expand at different rates due to temperature changes or mechanical deformation of the scale or substrate.

[0102] In some embodiments, intermediate member 406 may include carbon fiber.

[0103] Figure 5 An exemplary configuration of a scale arrangement 500 according to the present invention is shown. Figure 5 In the embodiment of the present invention, the elongation axis E extends into / outside the page. In addition to the thermal displacement release structure 512, Figure 5 The configuration shown is similar to Figure 4 Configuration shown. Figure 5 The configuration of the heat displacement release structure includes a first adhesive layer 504 , a first intermediate member 506 , a second adhesive layer 507 and a second intermediate member 508 . Figure 5 The illustrated scale arrangement 500 is attached to a substrate 510 by a clamp 509, which holds a second intermediate member 508 against the substrate 510. In some embodiments, the second intermediate member 508 comprises carbon fibers.

[0104] Figure 6 An exemplary configuration of a scale arrangement 600 according to the present invention is shown. The scale arrangement 600 includes a scale 602. Figure 6 In the illustrated scale arrangement 600, the scale 602 is attached to a thermal displacement release structure. The thermal displacement release structure includes a first adhesive layer 604A, which is a thermal release layer, and the first adhesive layer attaches the scale 602 to the first intermediate member 606A. The thermal displacement release structure further includes a second adhesive layer 604B, which is a thermal release layer attaching the scale 602 to the second intermediate member 606B.

[0105] In some embodiments, first adhesive layer 604A and second adhesive layer 604B also attach scale 602 to substrate 608. In other embodiments, scale 602 is attached to substrate 608 via a thermal displacement release structure that includes adhesive layer 604A and intermediate member 606A but without second adhesive layer 604B or second intermediate member 606B.

[0106] In other embodiments, first adhesive layer 604A and second adhesive layer 604B also attach the ruler to intermediate member 608. In some embodiments, intermediate member 608 includes carbon fibers. Figure 6 The illustrated scale arrangement 600 may be attached to a substrate, for example via a third adhesive layer (which may be a heat release layer), or by clamps, or via any other attachment method known to those skilled in the art.

[0107] Figure 7 An exemplary configuration of a scale arrangement according to the present invention is shown. The scale arrangement comprises a scale 702. Figure 7 In the illustrated ruler arrangement, the ruler 702 is attached with an adhesive layer 704, which attaches the ruler 702 to a substrate 710. In this embodiment, the ruler 702 is a low CTE ruler, in particular a FeNi36 (sometimes referred to as 64FeNi or Invar (RTM)) ruler having a thickness (in the direction normal to the substrate) of 200 μm. The adhesive layer is an adhesive tape having a thickness (in the direction normal to the substrate) of 0.2 mm, and a shear modulus of 1 kPa when the width of the adhesive tape is 6 mm. In other embodiments, the adhesive layer may include two or more layers of adhesive tape. In further embodiments, the thickness of each adhesive tape or each layer of adhesive tape shall 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 arrangement for measuring an encoder, the scale arrangement comprising a scale and a thermal displacement release structure, the thermal displacement release structure comprising an intermediate member, a first thermal displacement release layer and a second thermal displacement release layer, the first thermal displacement release layer being used to attach the scale to the intermediate member, wherein The thermal expansion coefficient of the intermediate member and the thermal expansion coefficient of the ruler meet the following conditions: -3×10 -6 K -1 ≤CTE(intermediate component)–CTE(scale)≤6×10 -6 K -1 .

2. A scale arrangement as claimed in claim 1, wherein: The second heat displacement release layer is used to attach the ruler to a substrate.

3. A scale arrangement as claimed in claim 2, wherein: The second heat displacement release layer is used to attach the intermediate member to the base material.

4. A scale arrangement as claimed in any one of claims 1 to 3, wherein: The scale comprises a metal or a metal alloy.

5. A scale arrangement as claimed in any preceding claim, wherein: The intermediate member includes a metal or a metal alloy.

6. A scale arrangement as claimed in any one of claims 1 to 3, wherein: The scale comprises glass or glass ceramic.

7. A scale arrangement as claimed in claim 6, wherein: The intermediate member includes glass or glass ceramic.

8. A scale arrangement as claimed in any one of claims 1 to 4 or 6, wherein: The intermediate member includes carbon fibers.

9. A scale arrangement as claimed in any preceding claim, wherein: The thermal displacement relief structure includes a second intermediate member.

10. A scale arrangement as claimed in claim 9, comprising a second heat displacement release layer attaching the intermediate member to the second intermediate member.

11. A scale arrangement as claimed in claim 10, wherein: The scale includes a metal or a metal alloy, the intermediate member includes a metal or a metal alloy, and the second intermediate member includes carbon fibers.

12. A scale arrangement as claimed in claim 3, 4 or 11, wherein: The metal or metal alloy comprises an iron-nickel ("FeNi") alloy, in particular having the alloy composition FeNi36.

13. A scale arrangement as claimed in any preceding claim, wherein: The relative stiffness of the ruler and the first thermal displacement release layer is at least 0.33 m -2 .

14. A scale arrangement as claimed in claim 2, wherein: The relative stiffness of the intermediate member and the second heat displacement release layer is at least 0.33 m -2 .

15. A scale arrangement as claimed in any preceding claim, wherein: The ruler arrangement is attached to a substrate.

16. A scale arrangement as claimed in claim 14, wherein: The scale arrangement is attached to the substrate by a heat displacement release layer which adheres the intermediate member of the heat displacement release structure to the substrate.

17. A scale arrangement as claimed in claim 15, wherein: An intermediate member of the thermal displacement relief structure directly adjacent the substrate is fastened to the substrate by at least one mechanical fastener, thereby attaching the scale arrangement to the substrate.

18. A scale arrangement as claimed in claim 17, wherein: The at least one mechanical fastener is used to clamp the intermediate member against the substrate.

19. A scale arrangement as claimed in claim 17 or 18, wherein: There is no adhesive and / or heat displacement release layer between the intermediate member and the substrate.

20. A scale arrangement as claimed in claims 9 and 17, wherein The second intermediate member is an intermediate member of the thermal displacement relief structure directly located on the substrate and on which the mechanical fastener acts.

21. A scale arrangement for measuring an encoder, the scale arrangement comprising a scale and a thermal displacement release structure, the thermal displacement release structure comprising a first intermediate member and a first thermal displacement release layer and a second intermediate member and a second thermal displacement release layer, the first thermal displacement release layer being used to attach the scale to the first intermediate member, and the second thermal displacement release layer being used to attach the first intermediate member to the second intermediate member.

22. A scale arrangement as claimed in claim 21, wherein: The scale includes a metal or a metal alloy, the intermediate member includes a metal or a metal alloy, and the second intermediate member includes carbon fibers.

23. A scale arrangement as claimed in claim 22, wherein: The scale comprises an iron-nickel ("FeNi") alloy, in particular having the alloy composition FeNi36.

24. A scale arrangement for measuring an encoder, the scale arrangement comprising a scale and a thermal displacement release structure, the thermal displacement release structure comprising an intermediate member and a first thermal displacement release layer, the first thermal displacement release layer being used to attach the scale to the intermediate member, wherein The relative stiffness of the ruler and the first thermal displacement release layer is at least 0.33 m -2 .

25. A scale arrangement for measuring an encoder, the scale arrangement comprising a metal or metal alloy scale and a thermal displacement release structure, the thermal displacement release structure comprising an intermediate member, a first thermal displacement release layer and a second thermal displacement release layer, the first thermal displacement release layer being used to attach the scale to the intermediate member, wherein The intermediate member includes a metal or a metal alloy.

26. A metrological scale, comprising a scale bearing layer and an adhesive layer, wherein the scale bearing layer comprises a layer having a thickness of 50 μm to 1000 μm and a thermal expansion coefficient of not more than 2×10 -6 K -1 The material of the adhesive layer has a shear modulus of no more than 20 kPa.

27. A metrological scale, comprising a scale bearing layer and an adhesive layer, wherein the scale bearing layer comprises a layer having a thickness of 50 μm to 1000 μm and a CTE of no more than 2×10 -6 K -1 materials, and wherein The thermal expansion behaviour of the scale carrying layer is governed by the properties of the scale carrying layer when mounted to a substrate.

Images