GB2597781A

GB2597781A - Graticule assembly

Info

Publication number: GB2597781A
Application number: GB2012223.0A
Authority: GB
Inventors: Collingwood Buckle Lewis
Original assignee: Foundrax Engineering Products Ltd
Current assignee: Foundrax Engineering Products Ltd
Priority date: 2020-08-06
Filing date: 2020-08-06
Publication date: 2022-02-09
Also published as: GB202012223D0

Abstract

A graticule assembly 104 consists of a graticule 202; and a source of electromagnetic radiation 204 configured to illuminate the graticule 202 with electromagnetic radiation. The electromagnetic radiation can be visible light which is provided by light emitting diodes or it may be ultraviolet light or infrared light. The graticule may have a fluorescent material configured to absorb ultraviolet light and emit visible light. The assembly may be used in a Brinell microscope and may be used in a Brinell hardness test to measure an indentation in a material. The graticule may reduce or increase an intensity of light it outputs when it is lit by the light source.

Description

GRATICULE ASSEMBLY FIELD OF THE INVENTION

The present invention relates to graticule assemblies including those for use with microscopes.

BACKGROUND

Many optical devices include graticules (also known as reticules) which may be built into the eyepiece of the optical device.

A graticule comprises a pattern of fine lines or markings which may be formed on or embedded in a transparent structure, such as a glass plate. The graticule may define fiducial marks and/or a measuring scale. The graticule may be used by a user viewing an object coincidentally with the graticule using the optical device to determine a size of and/or distance to the viewed object.

Examples of optical devices that may include a graticule include, but are not limited to, microscopes, telescope, binoculars, and weapon sights or scopes.

SUMMARY OF THE INVENTION

In a first aspect, there is provided a graticule assembly comprising a graticule, and a source of electromagnetic radiation configured to illuminate the graticule with electromagnetic radiation.

The electromagnetic radiation may be visible light. The electromagnetic radiation source may comprise one or more light emitting diodes. The visible light may be a coloured light selected from the group of coloured light consisting of red light, orange light, and green light. The source of electromagnetic radiation may be configured to be switched between outputting visible light having a first wavelength (or a first colour) and a second wavelength (or a second, different colour), the second wavelength being different to the first wavelength. -2 -

The electromagnetic radiation may be ultraviolet light or infrared light.

The electromagnetic radiation may be ultraviolet light, and the graticule may comprise a fluorescent material configured to absorb ultraviolet light and emit visible light.

The graticule assembly may further comprise a substrate, wherein the graticule is formed on a surface of, or embedded in, the substrate. The graticule may comprise one or more of: a paint or ink; a luminescent material; a fluorescent material; a phosphorescent material; an etched or engraved portion; and wires or fibres embedded with a substrate. The substrate may be a transparent or translucent substrate. The source of electromagnetic radiation may be configured to illuminate the graticule through the substrate. The substrate may comprise borosilicate glass. The source of electromagnetic radiation may be embedded in the substrate. The source of electromagnetic radiation may be remote from the substrate. The substrate may comprise a first surface, a second surface opposite to first surface, a side surface disposed between the first surface and the second surface. The graticule may be disposed on the first surface. The source of electromagnetic radiation may be positioned at or proximate to the side surface. The source of electromagnetic radiation may be arranged to illuminate the graticule from the side surface.

The graticule may comprise a plurality of substantially parallel lines. The source of electromagnetic radiation may be arranged to illuminate the graticule from a direction substantially parallel with one or more of the substantially parallel lines.

The graticule assembly may further comprise an optical system configured to produce an image of the graticule.

In a further aspect, there is provided a microscope comprising the graticule assembly of any preceding aspect.

The microscope may be a Brinell microscope.

The microscope may further comprise an illumination assembly configured to illuminate an object being viewed using the microscope. The -3 -source of electromagnetic radiation may be operatively coupled to the illumination assembly such that operation of the source of electromagnetic radiation is dependent on operation of the illumination assembly and/or operation of the illumination assembly is dependent on operation of the source of electromagnetic radiation. The illumination assembly may be configured to, responsive to the source of electromagnetic radiation being switched to a state in which it illuminates the graticule, reduce an intensity of light it outputs. The illumination assembly may be configured to, responsive to the source of electromagnetic radiation being switched to a state in which it does not illuminate the graticule, increase an intensity of light it outputs. The source of electromagnetic radiation may be configured to, responsive to the illumination assembly being switched on or off, vary an intensity of the electromagnetic radiation it outputs.

In a further aspect, there is provided a method comprising: providing a microscope, the microscope being in accordance with any preceding aspect; viewing an object using the microscope such that the object and the graticule are viewed coincidently; while the object and the graticule are being viewed coincidently, controlling the source of electromagnetic radiation to illuminate the graticule with electromagnetic radiation.

In a further aspect, there is provided a Brinell hardness test, comprising: providing an object; indenting, with an indenter, a surface of the object thereby to form an indentation in a surface of the object; providing a microscope, the microscope being in accordance with any preceding aspect; viewing, using the microscope, the surface of the object such that the indentation and the graticule are viewed coincidently; while the indentation and the graticule are being viewed coincidently, controlling the source of electromagnetic radiation to illuminate the graticule with electromagnetic radiation; using the graticule, determining a dimension of the indentation; and using the determined dimension of the indentation, determining a value indicative of a material hardness of the object (for example a Brinell Hardness Number (BHN) or an HBW value). -4 -

In a further aspect, there is provided a method of forming a graticule assembly comprising providing a graticule and coupling, to the graticule, a source of electromagnetic radiation such that the source of electromagnetic radiation is arranged to illuminate the graticule with electromagnetic radiation.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic illustration (not to scale) of a microscope; Figure 2 is a schematic illustration (not to scale) of a graticule assembly of the microscope; and Figure 3 is a schematic illustration (not to scale) of the graticule assembly.

DETAILED DESCRIPTION

Figure 1 is a schematic illustration (not to scale) of a microscope 100 according to an embodiment.

In this embodiment, the microscope 100 comprises a substantially tubular housing 101 containing an ocular lens 102, a graticule assembly 104, an objective lens 106, and a workpiece illumination assembly 108.

The ocular lens 102 is located at or proximate to a first opening at a first end of the housing 101. In use, the first end of the housing 101 is at the top of the microscope 100, as shown in Figure 1. In practice, the ocular lens 102 may comprise a plurality or series of lenses.

The graticule assembly 104 is located in the housing 101 between the ocular lens 102 and the objective lens 106. In use, as shown in Figure 1, the graticule assembly 104 is located below the ocular lens 102 and above the objective lens 106. The graticule assembly 104 will be described in more detail later below with reference to Figures 2 and 3. In this embodiment, the graticule assembly 104 comprises a graticule (see Figures 2 and 3). -5 -

The ocular lens 102 and the graticule assembly 104 may be located in an eyepiece of the microscope 100.

The objective lens 106 is located in the housing 101 between the graticule assembly 104 and the workpiece illumination assembly 108. In use, as shown in Figure 1, the objective lens 106 is located below the graticule assembly 104 and above the workpiece illumination assembly 108. The objective lens 106 is located at or proximate to a second opening at a second end of the housing 101, the second end being opposite to the first end. In use, as shown in Figure 1, the second end of the housing 101 is at the bottom of the microscope 100 and above an object 110 being viewed. In practice, the objective lens 106 may comprise a plurality or series of lenses.

The workpiece illumination assembly 108 is located at or proximate to the second opening at the second end of the housing 101. The workpiece illumination assembly 108 comprises a light source. In this embodiment, the workpiece illumination assembly 108 comprises a first plurality of light emitting diodes (LEDs). The microscope 100 may comprise a power source for the first plurality of LEDs. The workpiece illumination assembly 108 may be switched on or off by a user using the microscope 100. The workpiece illumination assembly 108 is configured to, when switched on, illuminate the object 110 being viewed, i.e. to provide visible light onto an upper surface of the object 110.

In use, the upper surface of the object 110 is illuminated with light from the workpiece illumination assembly 108. This light is reflected from the upper surface of the object 110 (which in this embodiment includes surface features such as an indentation 112) and into the housing 101 at the second end. The reflected light entering the second end of the housing 101 is focussed by the objective lens 106 to produce a magnified image. The focussed light from the objective lens 106 passes through the graticule assembly 104, and the ocular lens 102, allowing for a user 114 to view an image comprising the surface of the object 110 (including the indentation 112) and the graticule of the graticule assembly 104. The ocular lens 102 magnifies the image from the objective lens 106. -6 -

The ocular lens 102 and/or the objective lens 106 may be moveable within the housing 101. Such relative movement may allow the user to focus the image they see, for example such that that both the surface of the object 110 and the graticule are both in focus simultaneously. Such relative movement may allow for variation of the magnification provided by the microscope 100.

In this embodiment, the microscope 100 is used in a Brinell hardness test performed on the object 110. The microscope 100 may be referred to as a Brinell microscope, a Brinell testing microscope, or Brinell hardness testing microscope.

to The Brinell hardness test may be performed on the object 110 as follows.

Firstly, the indentation 112 is formed on the surface of the object 110 with an indenter. The characteristics of the indenter (including, for example, the size, shape, and material of the indenter), and the force applied, may be application dependent and may depend on the object 110 under test. Secondly, the user 114 views the indentation 112 on the surface of the object 110 using the microscope 110. As described above, the graticule of the graticule assembly 114 is viewed coincidently with the indentation. Thirdly, the user 114 measures or determines a dimension (e.g. a diameter) of the indentation 112 using the graticule. Fourthly, the user 114 calculates a Brinell Hardness Number (BHN) for the object 110 using the measured dimension of the indentation 112. The BHN is a number on the Brinell scale. The BHN characterises the indentation hardness of the object material. In other embodiments, a different value that is indicative of the material and/or indentation hardness of the object material is calculated using the measured dimension of the indentation 112, instead of or in addition to the BHN. For example, an HBW value (Hardness Brinell Wolfram).

Figure 2 is schematic illustration (not to scale) showing further details of an embodiment of the graticule assembly 104.

The graticule assembly 104 comprises a transparent substrate in the form of a transparent disc 200, a graticule 202, an illuminator 204, and an illuminator power source 205. -7 -

A top down view of the transparent disc 200 and the graticule 202 is shown in Figure 2.

Figure 3 is a schematic illustration (not to scale) showing a side-view of the transparent disc 200 and the graticule 202.

The transparent disc 200 is a substantially cylindrical disc of a transparent material, such as a transparent glass or plastic. Preferably, the transparent disc 200 is made of a material that is resistant to scratches and abrasions, and that includes very low levels of imperfections. Examples of such materials include, but are not limited to, borosilicate glass, such as Borofloat (RTM) 33. In practice, the transparent disc 200, i.e. the graticule substrate, may comprise a plurality or series of substrates or lenses that may be coupled together.

The transparent disc 200 may have any appropriate dimensions, depending on application.

The graticule 202 is a pattern of fine lines or markings formed on a surface (e.g. an upper, circular surface) of the transparent disc 200. The graticule 202 defines a measurement scale. For example, the lines of the graticule 202 may be spaced at 50pm intervals. Also for example, the lines of the graticule 202 may be lOpm thick or less.

In this embodiment, the graticule 202 is formed as follows. Firstly, the pattern of fine lines is etched onto the surface of the transparent disc 200. Any appropriate etching process may be performed, including but not limited to acid etching or laser etching. Secondly, the etched lines are painted with a paint, such as an enamel paint. Any appropriate painting process may be used to apply the paint to the etched portions of the surface of the transparent disc 200.

The illuminator 204 comprises a light source. In this embodiment, the illuminator 204 comprises a second plurality of LEDs.

In this embodiment, illuminator 204, i.e. the second plurality of LEDs, is embedded in the transparent disc 200. The illuminator 204, i.e. the second -8 -plurality of LEDs, is located at or proximate to a side surface of the transparent disc, spaced apart from the graticule 202 The illuminator power source 205 is operably coupled to the illuminator 204 and configured to provide electrical power to the illuminator 204.

The illuminator power source 205 comprises an electrical circuit including a battery 206 and a switch 206. The switch 206 is operable by a user 114 of the microscope 100.

In operation, when the switch 206 is closed, the battery 206 is electrically coupled to the illuminator 204, thereby to provide electrical power to the second plurality of LEDs. This causes the second plurality of LEDs to emit visible light into the transparent disc 200. The majority of this light tends to be retained in the transparent disc 200 via total internal reflection. This light travels through the transparent disc 200 and is incident on the graticule 202. The light incident or impinging on the graticule 202 tends to be scattered, or reflected, by the graticule 202. The etched portion of the graticule 202 may cause the incident light to be scattered. At least some of the scattered light travels through the housing 101 to the ocular lens 102, whereby it can be seen by the user 114.

Thus, the graticule 202 is illuminated, i.e. "lit-up", by the illuminator 204, and appears brighter to the user 114 than if the graticule 202 was not illuminated.

Advantageously, the above-described apparatus tends to improve visibility of the graticule by the user. This tends to facilitate the user distinguishing the graticule from other objections in the viewed image, e.g. features on the surface of the object in the above embodiment. This tends to facilitate and provide for more accurate measurement of features of the object being viewed The above-described graticule assembly tends to be particularly beneficial when implemented in a Brinell microscope, i.e. a microscope used in Brinell testing of an object for the measurement of an indentation to determine the object's BHN. Often, the surfaces of objects undergoing Brinell testing comprise marks or scratches, for example, caused by grinding, cutting, or other -g -machining processes. These marks typically appear as dark lines when viewed through a microscope. Conventional graticules also tend to appear as dark lines when viewed through a microscope. Thus, conventionally, it can be difficult for a user to distinguish between graticule marks and surface marks/imperfections on an object. This can cause errors in the determination of indentation dimensions, and thus incorrect evaluations of an object's BHN. Advantageously, the above-described apparatus tends to solve this problem by illuminating the graticule, providing greater differentiation between the graticule and the surface marks, and enabling the user to more easily differentiate between the graticule and ro those surface marks.

In the above-described graticule assembly, the graticule comprises a plurality of substantially parallel lines, and the illuminator, i.e. the second plurality of LEDs, is arranged to illuminate the graticule from a direction substantially parallel with one or more of the substantially parallel lines. This advantageously tends to provide for equal illumination the parallel lines of the graticule. Nevertheless, in other embodiments, the illuminator has a different position with respect to the graticule.

In the above embodiments, the graticule assembly is implemented in a microscope, in particular a Brinell microscope. However, in other embodiments, the graticule assembly is implemented in a different type of optical device.

Examples of such other types of optical device include, but are not limited to, telescope, binoculars, and weapon sights or scopes.

In the above embodiments, the illuminator, i.e. the second plurality of LEDs, is configured to illuminate the graticule with visible light. This light may be any appropriate colour. Preferably, the colour of the visible light emitted by the illuminator provides a high degree of contrast with the object being viewed. Examples of appropriate colours of light for providing such contrast include, but are not limited to red, orange, yellow, and green. In some embodiments, the illuminator is configured to allow a user to select the colour of light used to illuminate the graticule. For example, the illuminator may be configured to allow a user to select and switch between multiple different colours of light, such as red light and green light. In such embodiments, the illuminator may comprise -10 -multiple different LEDs, each configured to emit a different respective colour of light, and each being separately connectable to a power source, or the illuminator may comprise one or more LEDs with integral variable diodes to provide selectable colour shift.

In other embodiments, the illuminator comprises only a single LED.

In other embodiments, the illuminator comprises a different light source, other than a plurality of LEDs.

In other embodiments, the illuminator is configured to emit a different type of electromagnetic radiation other than visible light. For example, in some embodiments, the illuminator is configured to illuminate the graticule with ultraviolet (UV) or infrared (IR) light instead of visible light. In such embodiments, the graticule may be formed from a fluorescent (or alternatively phosphorescent) material, such as a fluorescent paint or ink. In use, incident electromagnetic radiation (e.g. UV light) provided by the illuminator is absorbed by the fluorescent graticule, and the graticule emits visible light which may be seen by the user. Advantageously, use of non-visible light to illuminate the graticule tends to reduce "fogging" and other artefacts that may be caused by the application of additional light into the microscope to illuminate the graticule. Such "fogging" and other artefacts may be caused by imperfections in the transparent disc upon which the graticule is formed. These imperfections may scatter the visible light used to illuminate the graticule, which may have a detrimental effect on the image seen by the user. Use of non-visible light to illuminate the graticule tends to solve this problem.

In the above embodiments, the illuminator is embedded in the transparent disc. This may improve retention of light from the illuminator within the transparent disc. However, in other embodiments, the illuminator is not embedded in the transparent disc, and is instead external to (e.g. remote from) the transparent disc.

In the above embodiments, the illuminator is located at or proximate to a side wall or surface of the transparent disc. However, in other embodiments, the illuminator has a different position.

In the above embodiments, the graticule is formed by etching the transparent disc and subsequently applying paint to the etched portions of the disc. In other words, the graticule comprises etched material and paint. However, in other embodiments, the graticule is formed in a different manner and may comprise different materials. For example, in some embodiments, the paint may be omitted, and the graticule may be formed by etching only. In some embodiments, the etching is omitted, and the graticule is formed only from a material (e.g. a paint or ink) disposed on the surface of the transparent disc. In some embodiments, the graticule is formed from a luminescent (e.g. fluorescent or phosphorescence) material. In some embodiments, the graticule is formed from a material that is disposed on the surface of the transparent disc by vacuum deposition, or another deposition process. In some embodiments, the graticule is formed from a material, such as wires or fibres, embedded in the transparent disc.

In the above embodiments, the transparent substrate, i.e. the transparent disc, is substantially cylindrical. However, in other embodiments the transparent substrate has a different shape, i.e. is non-cylindrical.

In the above embodiments, the microscope comprises a workpiece illumination assembly comprising a first plurality of LEDs. However, in other embodiments the workpiece illumination assembly is omitted. In some embodiments, the workpiece illumination assembly is external to the microscope.

In some embodiments, the workpiece illumination assembly and the illuminator are operatively coupled together. For example, in some embodiments the workpiece illumination assembly may be controlled based on the operation of the illuminator, and/or vice versa. For example, in some embodiments, the intensity of the light output by the workpiece illumination assembly may be controlled based on the intensity of the light output by the illuminator. By way of example, the workpiece illumination assembly may first be controlled to output visible light at a first, relatively high intensity when the illuminator is in its off state. Responsive to the user switching the illuminator to its on state, the workpiece illumination assembly may reduce (e.g. -12 -automatically) the intensity of the light it outputs. Similarly, the workpiece illumination assembly may increase (e.g. automatically) the intensity of the light it outputs responsive to the user switching the illuminator to its off state. This may be performed such the level of light received by the user remains substantially constant, or within a permitted range of intensity. A suitable light level sensing means may be implemented to measure the intensity of the light provided to the user. This automatic varying of the light intensities of the workpiece illumination assembly and/or the illuminator tends to be particularly useful in embodiments in which the microscope is used with a camera, i.e. where a camera is used to capture images of the magnified object surface and the graticule. Such automatic light level control tends to prevent or reduce the risk of over/under exposure of the camera images.

In the above embodiments, the microscope comprising the illuminated graticule is used to measure dimensions of an indentation. However, in other embodiments, the microscope and/or illuminated graticule may be used in a different application, for example to determine, measure, or analyse some characteristic of a different type of surface feature or treatment.

In the above embodiments, the graticule is as shown in Figure 2 and comprises a plurality of parallel lines. However, in other embodiments, the graticule may be formed of different features, i.e. may be a different pattern, depending on application. The graticule may be any shape used for comparison and/or alignment.

Claims

-13 -CLAIMS1. A graticule assembly comprising: a graticule; and a source of electromagnetic radiation configured to illuminate the graticule with electromagnetic radiation.
2. The graticule assembly of claim 1, wherein the electromagnetic radiation is visible light.to
3. The graticule assembly of claim 2, wherein the electromagnetic radiation source comprises one or more light emitting diodes.
4. The graticule assembly of claim 2 or 3, wherein the visible light is a coloured light selected from the group of coloured light consisting of red light, orange light, and green light.
5. The graticule assembly of any of claims 2 to 4, wherein the source of electromagnetic radiation is configured to be switched between outputting visible light having a first wavelength and a second wavelength, the second wavelength being different to the first wavelength.
6. The graticule assembly of claim 1, wherein the electromagnetic radiation is ultraviolet light or infrared light.
7. The graticule assembly of claim 1, wherein: the electromagnetic radiation is ultraviolet light; and the graticule comprises a fluorescent material configured to absorb ultraviolet light and emit visible light.
8. The graticule assembly of any of claims 1 to 7, further comprising a substrate, wherein the graticule is formed on a surface of, or embedded in, the substrate.
9. The graticule assembly of claim 8, wherein the graticule comprises one or more of: a paint or ink; a luminescent material; a fluorescent material; a phosphorescent material; an etched or engraved portion; and wires or fibres embedded with a substrate.
10. The graticule assembly of claim 8 or 9, wherein: the substrate is a transparent substrate; and the source of electromagnetic radiation is configured to illuminate the graticule through the substrate.
11. The graticule assembly of claim 10, wherein the substrate comprises borosilicate glass.
12. The graticule assembly of any of claims 8 to 11, wherein the source of electromagnetic radiation is embedded in the substrate.
13. The graticule assembly of any of claims 8 to 11, wherein the source of electromagnetic radiation is remote from the substrate.
14. The graticule assembly of any of claims 8 to 13, wherein the substrate comprises: a first surface; a second surface opposite to first surface; a side surface disposed between the first surface and the second surface; the graticule is disposed on the first surface; and the source of electromagnetic radiation is positioned at or proximate to the side surface.
15. The graticule assembly of any of claims 8 to 14, wherein the substrate comprises: a first surface; a second surface opposite to first surface; a side surface disposed between the first surface and the second surface; the graticule is disposed on the first surface and the source of electromagnetic radiation is arranged to illuminate the graticule from the side surface
16. The graticule assembly of any of claims 1 to 15, wherein: the graticule comprises a plurality of substantially parallel lines; and the source of electromagnetic radiation is arranged to illuminate the graticule from a direction substantially parallel with one or more of the substantially parallel lines.
17. The graticule assembly of any of claims 1 to 16 further comprising an optical system configured to produce an image of the graticule.
18. A microscope comprising the graticule assembly of any of claims 1 to 17.
19. The microscope of claim 18, wherein the microscope is a Brinell microscope.
20. The microscope of claim 18 or 19, further comprising an illumination assembly configured to illuminate an object being viewed using the microscope.
21. The microscope of claim 20, wherein the source of electromagnetic radiation is coupled to the illumination assembly such that operation of the source of electromagnetic radiation is dependent on operation of the illumination assembly and/or operation of the illumination assembly is dependent on operation of the source of electromagnetic radiation.
22. The microscope of claim 21, wherein: the illumination assembly is configured to, responsive to the source of electromagnetic radiation being switched to a state in which it illuminates the graticule, reduce an intensity of light it outputs; and/or the illumination assembly is configured to, responsive to the source of electromagnetic radiation being switched to a state in which it does not illuminate the graticule, increase an intensity of light it outputs.
23. A method comprising: providing a microscope, the microscope being in accordance with any of claims 18 to 22; -17 -viewing an object using the microscope such that the object and the graticule are viewed coincidently; while the object and the graticule are being viewed coincidently, controlling the source of electromagnetic radiation to illuminate the graticule with electromagnetic radiation.
24. A Brinell hardness test, comprising: providing an object; indenting, with an indenter, a surface of the object thereby to form an indentation in a surface of the object; providing a microscope, the microscope being in accordance with any of claims 18 to 22; viewing, using the microscope, the surface of the object such that the indentation and the graticule are viewed coincidently; while the indentation and the graticule are being viewed coincidently, controlling the source of electromagnetic radiation to illuminate the graticule with electromagnetic radiation; using the graticule, determining a dimension of the indentation; and using the determined dimension of the indentation, determining a value indicative of a material hardness of the object.
25. A method of forming a graticule assembly comprising: providing a graticule; and coupling, to the graticule, a source of electromagnetic radiation such that the source of electromagnetic radiation is arranged to illuminate the graticule with electromagnetic radiation.