FIELD

[0001] The specification relates generally to apparatus and methods associated with petrographic imaging, and more specifically to petrographic imaging apparatus for imaging an optically shielded thin section.

BACKGROUND

[0002] U.S. Pat. App. No. 3,649,100 purports to disclose a polarizing slide unit of conventional 35 mm photographic slide proportions or other standard slide proportions adapted to be handled or projected by a conventional diascope or slide projector. The polarizing slide unit includes a polarizing light mount assembly of hollow construction having slot or pocket means adapted to removably receive a rock thin section or the like and which may be of standard or conventional microscope slide proportions. The polarizing mount assembly removably supports a rock section slide specimen in sandwich fashion between two polarizing filter panes positioned relative to one another with mutually crossed polarizing axes. The slide unit combination of the rock specimen thin section and the polarizing mount assembly is adapted to be positioned in the light system of a conventional slide projector and to project a polarized light image of the thin section specimen on a projection screen surface.

[0003] U.S. Pat. App. No. 9,786,065 purports to disclose techniques for an image-based analysis of a geological thin section, in which the techniques include (i) acquiring a plurality of images from a geological thin section of a rock sample from a subterranean zone; (ii) manipulating the plurality of images to derive a composite image; (iii) optimizing the composite image to derive a seed image; (iv) identifying, in the seed image, a particular seed pixel of a plurality of contiguous pixels that comprise an image of a grain of a plurality of grains of the rock sample in the seed image; (v) determining, with a specified algorithm, a shape of the grain based on the seed pixel; (vi) determining, based on the shape of the grain, a size of the grain; and (vii) preparing the determination of the size of the grain for presentation to a user. [0004] U.S. Pat. App. No. 10,043,274 purports to disclose a method for processing image data of a sample is disclosed. The method comprises registering a first and a second images of at least partially overlapping spatial regions of the sample and processing data from the registered images to obtain integrated image data comprising information about the sample, said information being additional to that avail-able from said first and second images.

SUMMARY

[0005] The following summary is intended to introduce the reader to various aspects of the applicant’s teaching, but not to define any invention.

[0006] According to some aspects, there is provided a petrographic imaging apparatus for imaging petrographic thin sections, the petrographic imaging apparatus comprising a housing having a first end and a second end opposite the first end, and an imaging axis extending between the first and second ends; a thin section holder for holding a planar thin section, the planar thin section having a forward surface and an opposing rearward surface, the thin section holder secured to the housing and operable to hold the thin section with the forward surface facing the second end and the rearward surface facing the first end in a first position that is in line with the imaging axis; a sensor system secured to the housing in a second position that is at the second end of the housing and in line with the imaging axis, and the sensor system operable to be directed along the imaging axis to record a physical property of the thin section held by the thin section holder in the first position; at least one light source secured to the housing and operable to illuminate the thin section held by the thin section holder in the first position, the at least one light source including at least one transmitted light source arranged to illuminate the thin section from the first end; a first filter holder operable to hold a first polarizing filter in a third position that is in line with the imaging axis and between the thin section forward surface and the sensor system, and a second filter holder operable to hold a second polarizing filter in a fourth position that is in line with the imaging axis and between the thin section rearward surface and the at least one transmitted light source, and wherein the housing optically shields at least the thin section in the first position and the sensor system in the second position from light sources external to the petrographic imaging apparatus.

[0007] In some examples, the housing delineates an imaging cavity in which the thin section is received in the first position, and wherein the housing optically shields the imaging cavity from the light sources external to the petrographic imaging apparatus.

[0008] In some examples, the housing includes a framework covered with an outer skin such that light is substantially or entirely blocked from entering the imaging cavity.

[0009] In some examples, the housing is a monocoque housing.

[0010] In some examples, the transmitted light source is operable to emit visible light.

[0011] In some examples, the transmitted light source is operable to direct substantially all the visible light emitted by the transmitted light source directly towards the thin section in the first position.

[0012] In some examples, at least one of the pair of filter holders is operable to selectively hold the first or second polarizing filter in line with the imaging axis.

[0013] In some examples, at least one of the pair of filter holders is operable to selectively remove the first or second polarizing filter from the third or fourth position and move at least one other filter into the third or fourth position.

[0014] In some examples, the at least one of the pair of filter holders includes a turntable operable to rotate to remove the first or second polarizing filter from the third or fourth position and move at least one other filter into the third or fourth position. [0015] In some examples, the at least one of the pair of filter holders includes a rail system to carry the first or second polarization filter in and out of the third or fourth position.

[0016] In some examples, the at least one light source includes an incident light source arranged to illuminate the thin section in the first position from the second end.

[0017] In some examples, the incident light source is operable to emit electromagnetic radiation with a wavelength between 100 nm and 10,000 nm.

[0018] In some examples, a field of view of the sensor system in the second position includes at least 75% of a forward surface area of the forward surface of the thin section in the first position, and the incident light source is arranged to evenly illuminate the forward surface of the thin section in the first position without blocking the field of view of the sensor system in the second position.

[0019] In some examples, the petrographic imaging apparatus further comprises an incident light polarization assembly positioned between the incident light source and the thin section in the first position to polarize light from the incident light source without obstructing the field of view of the sensor system in the second position.

[0020] In some examples, the petrographic imaging apparatus further comprises a bandpass filter holder operable to selectively position a bandpass filter in line with the imaging axis between the sensor system in the second position and the thin section in the first position.

[0021] In some examples, the sensor system includes a camera or a spectroradiometer.

[0022] In some examples, the sensor system is selectively positionable in line with the imaging axis. [0023] In some examples, the sensor system in the second position has a field of view covering at least half of a forward surface area of the forward surface of the thin section in the first position.

[0024] In some examples, the first polarizing filter is a first plane polarizing filter and the second polarizing filter is a second plane polarizing filter, and wherein at least one of the first plane polarizing filter held by the first filter holder in the third position, the second plane polarizing filter held by the second filter holder in the fourth position, and the thin section held by the thin section holder in the first position is rotatable about the imaging axis in a rotational movement.

[0025] In some examples, the petrographic imaging apparatus further comprises a stepper motor operable to drive the rotational movement.

[0026] In some examples, the sensor system in the second position is operable to capture a plurality of images of the thin section in the first position during the rotational movement.

[0027] In some examples, the plurality of images are taken without relative movement between the thin section and the sensor system.

[0028] In some examples, the sensor system in the second position is operable to capture a plurality of images including a first image of the thin section in the first position while the thin section is illuminated by a first light source of the at least one light source and a second image of the thin section in the first position while the thin section is illuminated by a second light source of the at least one light source.

[0029] In some examples, the thin section holder is operable to hold the thin section in the first position with the forward surface perpendicular to the imaging axis, and wherein the sensor system in the second position has an optical axis parallel with the imaging axis.

[0030] In some examples, the sensor system includes a SLR digital camera. [0031] In some examples, the thin section holder is operable to remove the thin section from the first position and move at least one other thin section into the first position.

[0032] In some examples, the at least one light source includes an infrared light source or an ultraviolet light source.

[0033] In some examples, the at least one light source is operable to illuminate the thin section in the first position from at least two angles of incidence.

[0034] According to some aspects, there is provided a petrographic imaging system for imaging petrographic thin sections, the petrographic imaging system comprising a petrographic imaging apparatus, including a housing having a first end and a second end opposite the first end, and an imaging axis extending between the first and second ends, a thin section holder for holding a planar thin section, the planar thin section having a forward surface and an opposing rearward surface, the thin section holder secured to the housing and operable to hold the thin section with the forward surface facing the second end and the rearward surface facing the first end in a first position that is in line with the imaging axis, a sensor system secured to the housing and operable to be directed along the imaging axis from a second position at the second end to record a physical property of the thin section held by the thin section holder in the first position, at least one light source secured to the housing and operable to illuminate the thin section held by the thin section holder in the first position, the at least one light source including at least one transmitted light source arranged to illuminate the thin section from the first end, a first filter holder operable to hold a first plane polarizing filter in a third position that is in line with the imaging axis and between the thin section forward surface and the sensor system, and a second filter holder operable to hold a second plane polarizing filter in a fourth position that is in line with the imaging axis and between the thin section rearward surface and the at least one transmitted light source, and wherein the housing optically shields at least the thin section in the first position and the sensor system in the second position from light sources external to the petrographic imaging apparatus, and wherein at least one of the first plane polarizing filter in the third position, the second plane polarizing filter in the fourth position, and the thin section in the first position is rotatable in a rotational movement; and a control system communicatively coupled to the petrographic imaging apparatus to control the rotational movement and the sensor system, the control system operable to apply a set of predetermined settings to the petrographic imaging apparatus in response to receiving an indication of a type of the thin section.

[0035] In some examples, the sensor system includes a digital camera.

[0036] In some examples, the at least one light source includes an infrared light source or an ultraviolet light source.

[0037] In some examples, the at least one light source is operable to illuminate the thin section in the first position from at least two angles of incidence.

[0038] In some examples, the petrographic imaging apparatus further comprises a stepper motor operable to drive the rotational movement, the control system communicatively coupled to the stepper motor to control the stepper motor.

[0039] In some examples, the petrographic imaging apparatus further comprises an automated thin section exchanger operable to remove the thin section from the thin section holder and replace the thin section with an other thin section.

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The drawings included herewith are for illustrating various examples of articles, methods, and apparatuses of the present specification and are not intended to limit the scope of what is taught in any way. In the drawings:

[0041] Figure 1 is a perspective view of a first petrographic imaging apparatus; [0042] Figure 2 is an exploded view of the petrographic imaging apparatus of Figure 1 ;

[0043] Figure 3 is a perspective top view of a second petrographic imaging apparatus;

[0044] Figure 4 is a perspective top view of a sample thin section;

[0045] Figure 5 is a perspective top view of the petrographic imaging apparatus of Figure 3, with a door open to show an imaging chamber;

[0046] Figure 6 is a perspective bottom view of the petrographic imaging apparatus of Figure 5;

[0047] Figure 7 is a cross sectional view of the petrographic imaging apparatus of Figure 3, taken along line 7-7 of Figure 6;

[0048] Figure 8 is a cross sectional view of the petrographic imaging apparatus of Figure 3, taken along line 8-8 of Figure 6; and

[0049] Figure 9 is a schematic diagram of a petrographic imaging system.

DETAILED DESCRIPTION

[0050] Various apparatuses or processes will be described below to provide an example of an embodiment of each claimed invention. No embodiment described below limits any claimed invention and any claimed invention may cover processes or apparatuses that differ from those described below. The claimed inventions are not limited to apparatuses or processes having all of the features of any one apparatus or process described below or to features common to multiple or all of the apparatuses or process described below. It is possible that an apparatus or process described below is not an embodiment of any claimed invention. Any invention disclosed in an apparatus or process described below that is not claimed in this document may be the subject matter of another protective instrument, for example, a continuing patent application, and the applicants, inventors or owners do not intend to abandon, disclaim, or dedicate to the public any such invention by its disclosure in this document.

[0051] Referring to Figure 1 , an example of a petrographic imaging apparatus 10 for imaging petrographic thin sections is illustrated. The petrographic imaging apparatus 10 includes a housing 12 having a first end 14 and a second end 16 opposite the first end 14. The housing 12 has an imaging axis 18 extending between the first and second ends 14, 16.

[0052] The petrographic imaging apparatus 10 also includes a thin section holder 20 for holding a planar thin section 22. The planar thin section 22 has a forward surface 24 and an opposing rearward surface 26. The thin section holder 20 is secured to the housing 12 and operable to hold the thin section 22 in a first position 30 in line with the imaging axis 18 with the forward surface 24 facing the second end 16 and the rearward surface 26 facing the first end 14. The thin section holder 20 may be operable to rotate the thin section 22 about the imaging axis 18 while the thin section 22 is in the first position 30 (e.g., carrying the thin section 22 on a rotatable turntable). The thin section holder 20 may also be operable to selectively hold the thin section 22 in the first position 30 (i.e. , able to remove the thin section from the first position 30, such as by carrying it along rails, and/or replace the thin section with another thin section).

[0053] In some examples, the thin section holder 20 is operable to carry the thin section 22 in and out of the position 30, and the petrographic imaging apparatus 10 includes a slide changer 23 operable to remove the thin section 22 from the thin section holder 20 when the thin section 22 is not in the position 30 and place another thin section on the thin section holder 20 to be moved into the position 30 to be sensed.

[0054] The petrographic imaging apparatus 10 includes a sensor system 34 secured to the housing 12. The sensor system 34 is operable to be directed along the imaging axis 18 from a second position 36 at the second end 16 to record a physical property of the thin section 22 held by the thin section holder 20 in line with the imaging axis 18. The sensor system 34 may include a camera and/or a spectroradiometer. The sensor system 34 may be selectively positionable in line with the imaging axis 18 (e.g., using a rail system and/or a wheel or turntable).

[0055] The sensor system 34 in the second position 36 may have a field of view (i.e. , the area that the sensor system 34 can capture, such as the area that a camera of the sensor system 34 can capture in an image) covering a large portion of a forward surface area of the forward surface 24 of the thin section 22 held in the first position 30. For example, the sensor system 34 may have a field of view covering at least half of a forward surface area of the forward surface 24 of the thin section 22 in the first position 30.

[0056] At least one light source 38 is secured to the housing 12 and operable to illuminate the thin section 22 held by the thin section holder 20 in the first position 30.

[0057] The at least one light source 38 includes at least one transmitted light source 40 arranged to illuminate the thin section 22 from the first end 14 (i.e., from a side opposite the sensor system 34). The at least one transmitted light source 40 may be operable to emit visible light. In some examples, the transmitted light source 40 is operable to direct substantially all the visible light emitted by the transmitted light source 40 directly towards the thin section 22 in the first position 30 (i.e., the transmitted light source 40 does not emit light in directions other than directly towards the first position 30). The transmitted light source 40 may include a fiberoptic backlight.

[0058] In some examples, the at least one light source 38 includes an incident light source 42 (Figure 2) arranged to illuminate the thin section 22 in the first position 30 from the second end 16 (i.e., from the same side that the sensor system 34 is on). The incident light source 42 is operable to emit electromagnetic radiation with a wavelength between 100 nm and 10,000 nm. In some examples, a field of view of the sensor system 34 in the second position 36 includes at least 75% of a forward surface area of the forward surface 24 of the thin section 22 in the first position 30, and the incident light source 42 is arranged to evenly illuminate the forward surface 24 of the thin section 22 in the first position 30 without blocking the field of view of the sensor system 34 in the second position 36 (e.g., the incident light source 38 may be shaped as an annular ring as shown in Figure 2).

[0059] The incident light source 38 may include a tunable light source. For example, the incident light source 38 may include at least one tunable light emitting diode assembly (e.g., tunable to emit ultraviolet light, visible light, or near infrared light).

[0060] In some examples, an incident light polarizing filter holder 43 is operable to selectively position a polarizing filter in a fifth position 45 between the incident light source 42 and the thin section 22 in the first position 30 to polarize light from the incident light source 42. The incident light polarization assembly 43 may be arranged to polarize light from the incident light source 42 prior to the light reaching the thin section 22 in the first position 30 without the incident light polarization assembly 43 obstructing the field of view of the sensor system 34 in the second position 36.

[0061] The petrographic imaging apparatus 10 also includes a first filter holder 44 and a second filter holder 46. The first filter holder 44 is operable to hold a first polarizing filter (e.g., a first plane polarizing filter) in a third position 48 in line with the imaging axis 12 and between the sensor system 34 and the thin section forward surface 24 of the thin section 22 in the first position 30. The second filter holder 46 is operable to hold a second polarizing filter (e.g., a second plane polarizing filter) in a fourth position 50 in line with the imaging axis 12 and between the at least one transmitted light source 40 and the thin section rearward surface 26 of the thin section 22 in the first position 30.

[0062] In some examples, one or both of the first and second filter holders 44, 46 is operable to move the carried filter. In the illustrated example, both of the first and second filter holders 44, 46 is operable to move the carried filter. In some examples, the first filter holder 44 is operable to selectively hold the first polarizing filter in line with the imaging axis 18, and may be operable to remove the first polarizing filter from the third position 48 and move at least one other filter into the third position 48. In some examples, the second filter holder 46 is operable to selectively hold the second polarizing filter in line with the imaging axis 18, and may be operable to remove the second polarizing filter from the fourth position 50 and move at least one other filter into the fourth position 50.

[0063] Referring now to Figure 2, in some examples, at least one of the pair of filter holders 44, 46 includes a rotatable wheel or turntable (not shown) and/or a rail system 54 for use in moving the carried filter. In the illustrated example each of the pair of filter holders 44, 46 includes a rail system 54 to carry the first or second polarization filter in and out of the third position 48 or fourth position 50. In some examples, each of the pair of filter holders 44, 46 includes a wheel or turntable operable to rotate to remove the first or second polarizing filter from the third position 48 or fourth position 50 and move at least one other filter into the third position 48 or fourth position 50. Alternatively, or additionally, one or both of the pair of filter holders 44, 46 may include a turntable operable to rotate the carried filter about the imaging axis 18 while the carried filter is in position (i.e., in the third position 48 or fourth position 50), such that different light polarization combinations may be tried.

[0064] Referring again to Figure 1 , the housing 12 optically shields at least the thin section 22 in the first position 30 and the sensor system 34 in the second position 36 from light sources external to the petrographic imaging apparatus 10. In some examples, the housing 12 delineates an imaging cavity in which the thin section 22 is received in the first position 30, and the housing 12 optically shields the imaging cavity from the light sources external to the petrographic imaging apparatus 10. The housing 12 may be a monocoque housing or may include a framework covered with an outer skin such that light is substantially or entirely blocked from entering the imaging cavity.

[0065] In some examples, the petrographic imaging apparatus 10 also includes a bandpass filter holder 60 operable to selectively position a bandpass filer in a sixth position 62 in line with the imaging axis 18 between the sensor system 34 in the second position 36 and the thin section 22 in the first position 30. The bandpass filter holder 60 may include a rotatable wheel 52 and/or a rail system 54 for use in moving the carried filter (e.g., rotating the wheel 52, indicated in Figure 2, to exchange one filter for another, and moving the wheel along the rail to move it out of line with the imaging axis 18).

[0066] In some examples, at least one of the first polarizing filter held by the first filter holder 44 in the third position 48, the second polarizing filter held by the second filter holder 46 in the fourth position 50, and the thin section 22 held by the thin section holder 20 in the first position 30 is rotatable about the imaging axis 18 in a rotational movement (e.g., the holder of one or more is able to rotate the filter and/or then section in position). The petrographic imaging apparatus 10 may include a stepper motor operable to drive the rotational movement. The sensor system 34 in the second position 36 may be operable to capture a plurality of images of the subject thin section 22 in the first position 30 during the rotational movement.

[0067] The petrographic imaging apparatus 100 may also include a further carrier 70 for a non-reflective background sheet. The carrier 70 may be operable to hold the non-reflective background sheet in a seventh position 72 in line with the imaging axis 18 and between the thin section holder 20 and the transmitted light source 40. For example, the carrier 70 may be operable to hold the non- reflective background sheet between the thin section holder 20 and the second filter holder 46 in the fourth position 50. The carrier 70 may be operable to move the non-reflective background sheet, such as to move the sheet in and out of the seventh position 72 along rails 54. The non-reflective background sheet may be a matte blank that is placed under the thin section to prevent spurious reflections and inaccuracy when using reflected light.

[0068] Referring now to Figure 3, another example of a petrographic imaging apparatus 100 is illustrated. In some examples, the petrographic imaging apparatus 100 has a housing 104 forming an enclosed imaging chamber 108 (Figure 5). In some examples, an enclosed imaging chamber shields a sample, such as a thin section, from unintended light contamination. In some examples, an enclosed imaging chamber facilitates capturing uncontaminated images. The petrographic imaging apparatus 100 is configured for us in imaging thin sections, such as from oil and gas exploration.

[0069] In the illustrated example, the housing 104 includes a body portion 112 enclosing an imaging chamber. The body portion 112 may be wider at a first end (e.g., the lower end) than at an opposite end (e.g., an upper end) to accommodate a thin section at the wider end to be imaged by a sensor from the opposite end. In some examples, the body portion 112 is a truncated pyramidal shape. The enclosed imaging chamber 108 of the illustrated example is accessible through a door 116 in a wall of the truncated pyramidal body portion 112.

[0070] The illustrated housing 104 also includes a base portion 120 on a first end 124 of the truncated pyramidal body portion 104 and an imaging system case portion 128 on a second end 132 of the truncated pyramidal body portion 112 opposite the first end 124. The illustrated example base portion 120 rests on legs 122.

[0071] In some examples, a petrographic imaging apparatus such as the petrographic imaging apparatus 100 of Figure 3 may be used to image a sample of material such as rock, mineral, and/or soil. In some examples, the sample of material is processed and/or shaped to facilitate imaging. In some examples, the sample of material is formed into a thin section. For example, a thin sliver of material may be taken from the sample and mounted to a glass slide.

[0072] Referring now to Figure 4, an example of a thin section 136 is illustrated. The example thin section 136 has a forward surface 140 and a rearward surface 144 opposite the forward surface 140. The example thin section 136 is a rectangular thin section having a forward surface length 148 and a forward surface width 152. In the illustrated example, the thin section 136 is a rectangular thin section, however in other examples the thin section 136 may be circular, oval, or otherwise shaped.

[0073] Referring now to Figure 5, the enclosed imaging chamber 108 may be accessed through an opening in the housing 104 when the door 116 is open. The enclosed imaging chamber 108 has a chamber first end 156 and a chamber second end 160 opposite the chamber first end 156. An imaging axis 164 extends between the chamber first end 156 and the chamber second end 160.

[0074] In some examples, the petrographic imaging apparatus 100 includes at least one sample holder to hold a sample, such as a thin section, to be studied and at least one filter holder to hold a polarizing filter adjacent the sample held by the at least one sample holder. In some examples, the petrographic imaging apparatus 100 includes at least one filter holder to hold a filter to modify light incident on a sample held by the sample holder and/or to modify light emitted from a sample held by the sample holder. In some examples, a filter is a planar polarizing filter. In some examples, a polarizing filter is a plane polarizing filter. In some examples, a polarizing filter is a circular polarizing filter.

[0075] In the illustrated example, the petrographic imaging apparatus 100 includes a sample holder 168, a first filter holder 172, and a second filter holder 176. The illustrated sample holder 168 is a thin section holder and is operable to hold a subject thin section 136 at the chamber first end 156 with the thin section forward surface 140 of the subject thin section 136 facing the chamber second end 160. In some examples, the sample holder 168 is operable to hold the thin section 136 with the forward surface 140 perpendicular to the imaging axis 164. The first filter holder 172 is operable to hold a first polarizing filter adjacent and parallel to the thin section forward surface 140 and the second filter holder is operable to hold a second polarizing filter adjacent and parallel to the thin section rearward surface 144.

[0076] In the illustrated example, each of the sample holder 168, the first filter holder 172, and the second filter holder 176 is a slot through the housing 104 from one side to an opposite side, and each is shaped to hold a thin, planar object. The illustrated sample holder 168 extends between sample access openings 180 in the outer surface of housing 104 (Figure 7). The illustrated first filter holder extends between first filter access openings 184 in the outer surface of housing 104 (Figure 8). The illustrated second filter holder extends between second filter access openings 188 in the outer surface of housing 104 (Figure 8).

[0077] Each of the illustrated sample holder 168, the first filter holder 172, and the second filter holder 176 intersects the chamber first end 156. In the illustrated example, the imaging axis 164 is a vertical axis, and the chamber first end 156 is a lower end while the chamber second end 160 is an upper end. In some examples, the sample holder 168 is a thin section holder operable to hold a thin section 136 with a forward surface facing upward and perpendicular to the imaging axis 164, the first filter holder 172 operable to hold the first filter above and parallel to the thin section 136 and the second filter holder 176 operable to hold the second filter below and parallel to the thin section 136.

[0078] In some examples, at least one sample held by a sample holder and/or at least one filter held by a filter holder is a rotatable element that is rotatable in a rotational movement. In some examples, the imaging axis 164 passes through the rotatable element, and the rotational movement is a rotation about the imaging axis 164.

[0079] In some examples, the petrographic imaging apparatus 100 includes a rotator system coupled to the one or more rotatable elements to rotate the one or more rotatable elements. Rotation of a sample and/or filter may permit additional information to be extracted from a petrographic thin section. In some examples, rotation facilitates viewing the petrographic thin section 136 at different rotational perspectives. In some examples, rotation facilitates viewing the petrographic thin section 136 in plane-polarized light and/or cross-polarized light.

[0080] In some examples, many mineral are colorless in plane-polarized light, and grain boundaries are difficult to distinguish. In some examples, interference color displayed depends on the mineral type, the orientation of the indicatnx of the grain with respect to the polarizers, and the thickness of the thin section 136. In some examples, adjacent grains may have similar interference colors at some orientations of the thin section 136 with respect to the polarizing filters.

[0081] In some examples, additional information is extracted by rotating the thin section 136 relative the polarizing filter or filters. In some examples, additional information is extracted by rotating one or more filter relative to the thin section and one or more other filter. In some examples, a plurality of thin section images taken at different angels of rotation provides more information than a single image.

[0082] In some examples, the petrographic imaging apparatus 100 can take a plurality of images of the thin section 136 during the rotational movement of the rotatable element or elements. In some examples, images taken at different rotational positions of the rotational movement provide different information about the thin section 136.

[0083] In some examples, the plurality of images are taken without any relative movement between the subject thin section 136 and the optical imaging system 192 (Figure 6). For example, one or more polarizing filter held by a filter holder may rotate between imaging events. In some examples, a polarizing filter held by first filter holder 172 is rotated between imaging events and/or a polarizing filter held by second filter holder 176 is rotated between imaging events. In some examples, maintaining the position of the thin section 136 relative to the optical imaging system 192 facilitates comparing images. In some examples, an identical portion of the forward surface 140 is imaged in each image of a stack or plurality of images.

[0084] In some examples, the plurality of images are taken without relative movement between the subject thin section 136 and the optical imaging system 192 aside from rotational movement of the subject thin section 136 about the imaging axis 164. [0085] In some examples, the rotational movement is a continuous movement. In some examples, the rotational movement is a stepped movement between predetermined positions. In some examples, a stepper motor is used to drive the rotational movement. The stepper motor may be used to rotate the rotatable element or elements between a set of at least two predetermined positions. For example, a stepper motor may be used to drive a polarizing filter held by the first filter holder 172 to rotate by 90 degrees about the imaging axis 164 while the sample held by the sample holder 168 and the second polarizing filter held by the second filter holder 176 are held in position. A 90 degree rotational movement may permit viewing the petrographic thin section 136 in cross-polarized light.

[0086] In some examples, the thin section 136 may be rotated in addition to or as an alternative to rotation of one or more polarizing filter. For example, the stepper motor may be independently operable to rotate the thin section 136 between a plurality of sample rotational positions and operable to rotate the polarizing filter held by the first filter holder 172 about the imaging axis 164 between at least a pair of rotational positions with angles of rotation separated by 90 degrees.

[0087] In some examples, one or more of a sample and a polarizing filter can be inserted and/or removed from the petrographic imaging apparatus 100 between images. For example, a user may wish to take an image with only a single polarizing filter, and a polarizing filter held by one of the first filter holder 172 and the second filter holder 176 may be removed. In some examples, the petrographic imaging apparatus 100 includes an automated filter and sample management system to insert and/or remove a polarizing filter and/or a sample.

[0088] In some examples, one or more of a sample and a polarizing filter can be replaced between images. In some examples, the automated filter and sample management system of the petrographic imaging apparatus 100 includes an automated thin section exchanger system. In some examples, the automated thin section exchanger system is operable to remove a subject thin section from a position held by the sample holder 168 and replace it with a replacement thin section.

[0089] In some examples, the petrographic imaging apparatus 100 includes an optical imaging system. In some examples, the optical imaging system is secured to a second end 160 of an enclosed imaging chamber opposite the first end 156 where the thin section 136 may be held. The optical imaging system may be, for example, a digital camera for taking one or more images of the thin section 136.

[0090] Referring now to Figure 6, in the illustrated example an optical imaging system 192 is secured to the housing 104 at the chamber second end 160 and is operable to image the subject thin section 136 held by the thin section holder 168. In the illustrated example, the optical imaging system 192 is in the imaging system case portion 128 at the chamber second end 160. The optical imaging system 192 includes an imaging lens 196 with an optical axis 200. In the illustrated example, the optical axis 200 is coaxial with the imaging axis 164.

[0091] In some examples, a field of view of an optical imaging system 192 covers at least half of a forward surface area of the forward surface 140 of the thin section 136 held at the chamber first end 156. In some examples, the optical imaging system 192 has a field of view having a view length and a view width. In some examples, the view length is at least half of the surface length 148 of the forward surface 140 of the subject thin section 136. In some examples, the view width is at least half of the surface width 152 of the forward surface 140 of the subject thin section 136.

[0092] In some examples, the optical imaging system 192 includes a digital camera. For example, the optical imaging system 192 may include a single lens reflex camera (SLR camera). In some examples, the optical imaging system 192 can be zoomed to accommodate various sizes of the thin section 136. In some examples, the optical imaging system has a set of predetermined zoom settings associated with a set of predetermined thin section sizes. In some examples, the optical imaging system 192 is a digital camera with a resolution between 24 and 32 megapixels. In some examples, the optical imaging system is a high-resolution system which includes a cooling system.

[0093] In some examples, the petrographic imaging apparatus 100 includes at least one light source. The at least one light source is secured to the housing 102 and operable to illuminate the thin section 136 held by the thin section holder 168. In some examples, the petrographic imaging apparatus 100 includes more than one light source.

[0094] In some examples, the petrographic imaging apparatus 100 includes more than one light source and the light sources are different types of light sources and/or are positioned with different angles of incidence on the thin section 136.

[0095] In some examples, the at least one light source is at least two light sources and the at least two light sources are different types of light sources. In some examples, different types of light sources differ in the wavelength, wavelength range, and/or intensity of the light they are able to deliver to the thin section 136 held by the thin section holder 168.

[0096] In some examples, the petrographic imaging apparatus 100 includes at least one of a visible light source operable to illuminate the thin section 136 with visible light, an infrared light source operable to illuminate the thin section 136 with infrared light, and an ultraviolet light source operable to illuminate the thin section 136 with ultraviolet light. In some examples, the at least one light source includes at least one visible light source and at least one of a ultraviolet light source and an infrared light source. In some examples, the petrographic imaging apparatus 100 can take a first image while the thin section 136 is illuminated by a first light source and can take a second image while the thin section 136 is illuminated by a second light source of a different type that the first light source.

[0097] In some examples, the at least one light source is at least two light sources and the at least two light sources are operable to illuminate the subject thin section 136 held by the thin section holder 168 from at least two angles of incidence. In some examples, the petrographic imaging apparatus 100 includes at least one transmission light source operable to illuminate the thin section 136 from the rearward surface 144 while the forward surface 140 is imaged by the optical imaging system 192 and at least one reflection light source operable to illuminate the thin section 136 from the forward surface 140 while the forward surface 140 is imaged by the optical imaging system 192. In some examples, the petrographic imaging apparatus 100 can take a first image while the thin section 136 is illuminated by a first light source from a first angle of incidence and can take a second image while the thin section 136 is illuminated by a second light source from a second angle of incidence different from the first angle of incidence.

[0098] In some examples, the petrographic imaging apparatus 100 has a plurality of illumination modes using different types of light sources and/or different light source positions relative to a thin section held by thin section holder 168. In some examples, the illumination mode of the petrographic imaging apparatus 100 can be switched between imaging events. In some examples, different illumination modes provide different information about a petrographic thin section 136. In some examples, switching illumination modes between imaging events facilitates comparing images.

[0099] In some examples, a plurality of images may be taken of the thin section 136 and the illumination mode may be changed between imaging events in addition or in alternative to changing one or more rotational positons. In some examples, the plurality of images taken in different illumination modes are taken without any rotational movement of any rotatable element. In some examples, the plurality of images taken in different illumination modes are taken without any relative movement between the subject thin section 136 and the optical imaging system 192 (Figure 6). In some examples, the plurality of images taken in different illumination modes are taken without relative movement between the subject thin section 136 and the optical imaging system 192 aside from rotational movement of the subject thin section 136 about the imaging axis 164. [00100] Referring again to Figure 6, in the illustrated example a visible spectrum transmission light source 204 is secured to the base 120 of the petrographic imaging apparatus 100 below the second filter holder 176. The visible spectrum transmission light source 204 is operable to illuminate the thin section 136 held by the thin section holder 168 with visible light from the rearward surface 144. An epifluorescent reflective light source is secured in the imaging chamber 108 at the chamber second end 160. The epifluorescent reflective light source is operable to illuminate the thin section 136 held by the thin section holder 168 with epifluorescent light from the forward surface 140.

[00101] A cable 208 extends from the illustrated example petrographic imaging apparatus 100. In some examples, the cable 208 includes a power cable to couple the petrographic imaging apparatus 100 to a power source. For example, the power source may supply power for one or more of the optical imaging system 192, a light source, an automated filter and sample management system, and a stepper motor.

[00102] In some examples, the cable 208 includes a communication cable to communicatively couple the petrographic imaging apparatus 100 with a control system.

[00103] Referring now to Figure 9, in some examples a petrographic imaging system 212 includes the petrographic imaging apparatus 100 and a control system 216 communicatively coupled to the petrographic imaging apparatus 100 through a communication link 218. In some examples, the communication link 218 is wired. In some examples, the communication link 218 is wireless. In some examples, the communication link 218 is a wired communications link included in cable 208 of petrographic imaging apparatus 100.

[00104] In some examples, the control system 216 includes a processor to implement instructions. In some examples, the control system 216 includes an input device 220 to receive input from a user and one or more data storage devices 224. In some examples, an input device is one or more of a computer mouse, computer keyboard, touchpad, and audio input device.

[00105] In some examples, the one or more data storage devices 224 are provided to store images received from the petrographic imaging apparatus 100. In some examples, the one or more data storage devices 224 store instructions for the petrographic imaging apparatus 100. In some examples, the data storage device includes instructions to direct the optical imaging system 192 to capture an image. In some examples, the data storage device includes instructions to direct the optical imaging system 192 to capture a plurality of images. In some examples, the data storage device includes instructions to direct the optical imaging system 192 to capture an image and to direct the at least one light source, automated filter and sample management system, and/or rotator system to change operational modes between imaging events.

[00106] In some examples, the control system 216 is integrated into the petrographic imaging apparatus 100. For example, the control system 216 may include a touch pad input device 220 on a wall of housing 104 and a data storage device 224 secured to housing 104, and may be communicative coupled to the imaging system, at least one light source, automated filter and sample management system, and/or rotator system via one or more interior communication link 218.

[00107] In some examples, the control system 216 is distributed. For example, the input device 220 may be integrated into or secured to the optical imaging apparatus 100 while one or more data storage devices 224 is located remotely.

[00108] In some examples, the control system 216 is operable to apply a set of predetermined settings to the petrographic imaging apparatus 100. In some examples, the control system 216 is operable to apply a set of predetermined settings to the petrographic imaging apparatus 100 in response to receiving an indication of the type of thin section 136 and/or the type of output required. In some examples, settings include one or more of applying rotational movement to one or more rotatable element, adjusting the optical imaging system 192, operating the optical imaging system 192 to capture one or more images, and operating the at least one light source to turn on or off one or more light sources of the at least one light source. [00109] For example, a user may indicate that a set of 2 images is required, one with plane polarized light and the other with cross polarized light. The control system 216 may be operable to first direct the optical imaging system 192 to capture a first image, then direct the rotator system to rotate the first polarizing filter held by the first filter holder 172 by 90 degrees, then direct the optical imaging system 192 to capture a second image, and provide the first and second images to the user. In some examples, providing images to a user includes one or more of displaying the images on a screen and storing to a data storage device such as device 224.

[00110] The present description is provided by way of example only. Various modification and variations may be made to these examples without departing from the scope of the invention, which is limited only by the appended claims.