Patent Description:
Standard techniques for creating 3D topographies include stylus instruments, profilometers, ultrasonic transducers, and laser triangulation among others. Shape-from-shading (SFS) and photometric stereo (PMS) have been used to create topographies by illuminating a specimen <NUM> with one or more a light sources <NUM>, <NUM> directing oblique light <NUM>, <NUM> toward the specimen <NUM> at an angle from <NUM> to <NUM> degrees and more typically from <NUM> to <NUM> degrees, as generally represented in <FIG>. The oblique illumination is reflected from the surface S of the object as reflected light <NUM>, and is captured by an image sensor (not shown) such as a CCD or CMOS sensor of a digital camera <NUM>. The light sources are moved to different positions located circumferentially around the object, with images taken at these different positions. These images are used to calculate the topography of the specimen <NUM> by known means, employing appropriate processor(s) <NUM>.

A standard reflected light microscope employing brightfield and darkfield functionality is shown in <FIG> and <FIG>. In this example the microscope <NUM> is equipped with a camera <NUM>. Oculars may also be present, such that the numeral <NUM> is to broadly represent oculars and/or a camera. Although the following description will refer to a reflected light microscope, similar techniques apply to transmitted light microscopes or instruments using brightfield/darkfield microscope objectives. A reflected light microscope <NUM> will be referenced in the following descriptions but the technology may apply to any imaging system using a brightfield/darkfield objective. The systems generally consist of a light source <NUM> providing light <NUM>, a vertical illuminator <NUM>, a brightfield/darkfield (BD) switch <NUM> and a BD objective <NUM>. <CIT> and <CIT> describe a BD objective. In a standard BD objective <NUM>, two channels are provided to guide the light to the specimen <NUM>. The light <NUM> is directed to a mirror <NUM> that reflects the light <NUM> toward the specimen <NUM> downwardly through the vertical illuminator <NUM>, the nosepiece <NUM>, and BD objective <NUM>. The BD switch <NUM>, as schematically shown, serves to limit the light <NUM> to pass either into a brightfield channel <NUM> or darkfield channel <NUM> separated by a shield wall <NUM>. With the BD switch <NUM> in a bright field position as in <FIG>, the light <NUM> is limited to a beam that is reflected off of the mirror <NUM> to enter the brightfield channel <NUM>, which directs the illuminating light <NUM>' through the BD objective <NUM> toward the surface S of the specimen <NUM> at an angle perpendicular (<NUM> degrees) to the plane of the specimen <NUM> and allows the reflected light <NUM> to pass to the oculars or camera <NUM>. As seen in <FIG>, when the BD switch <NUM> is in a darkfield position the light <NUM> is limited to an annular beam that is reflected off of the mirror <NUM> to enter the darkfield channel <NUM>, which is an annular channel directing illuminating light <NUM>" toward the specimen at an angle less than <NUM> degrees and typically <NUM> to <NUM> degrees.

It can be seen in <FIG> that the light path in brightfield (illuminating light <NUM>') is projected through the center of the nosepiece <NUM> and through the brightfield channel <NUM> of the BD objective <NUM>. The reflected light <NUM> is reflected back through the brightfield channel <NUM>, through the nosepiece <NUM> and tube lens <NUM> and is affected by any oculars and/or captured by a camera <NUM>. It is seen here that the illumination light <NUM>' in brightfield is at <NUM> degrees to the surface S of the specimen <NUM> and the reflected light <NUM> that is measured travels parallel to the illumination light <NUM>' but in an opposite direction. The projected illuminating light <NUM>' illuminates the entire field of view.

<FIG> shows the microscope <NUM> in darkfield mode. Here the light <NUM> is blocked by the darkfield switch <NUM> so that no light passes through the brightfield channel <NUM> and is instead directed to pass through the darkfield channel <NUM> as illuminating light <NUM>". This produces an annular beam (or, in other terms, a hollow cylinder or annular cylinder) of light that is projected toward the specimen <NUM> at an oblique angle determined by the design of the objective <NUM> and wall of the darkfield channel <NUM>. As known, the BD objective will have mirrors and/or prisms and/or light diffusers built into the objective to direct the oblique light. The illuminating light <NUM>" reflects off the surface S of the specimen <NUM> and the reflected light <NUM> travels up the brightfield channel to the ocular or camera <NUM>. The projected darkfield illuminating light <NUM>" illuminates the entire field of view from about the entire periphery (<NUM> degrees) of the objective.

In brightfield imaging it can be seen that the field of view F, which takes in at least a portion of the specimen <NUM>, is filled by direct <NUM> degrees illumination (the incoming illuminating light <NUM>' is orthogonal to the general resting plane of the specimen <NUM>) whereas in darkfield imaging, the field of view F is filled by oblique illumination (the incoming illuminating light <NUM>" is at an oblique angle to the general resting plane of the specimen <NUM>). The darkfield illumination is evenly distributed through the <NUM> degree circumference of the BD objective <NUM>.

<CIT> discloses an epi-illumination microscope comprising a light shielding plate with an annular opening centering around an optical axis, a diaphragm member placed at a pupil position (focal plane) of a light source side of an objective lens having a circular opening in the center part, and five sector opening parts and sector light shielding respectively <CIT> discloses an objective lens used for a microscope includes a lens, an iris diaphragm and a tubular body, wherein the lens, which is provided in a manner facing an object, transmits light reflected from a measuring surface of the object, the iris diaphragm, which is provided behind the lens, changes an aperture diameter of a light-transmissive aperture of a light-transmissive surface that is substantially orthogonal to a main optical axis of the light transmitted through the lens, and the tubular body, which is detachably mounted on a revolving nosepiece of a trunk that includes a zoom imaging lens for forming an image from the light transmitted through the light-transmissive aperture, holds the lens and the iris diaphragm. <CIT> discloses an object lens, wherein a plurality of shield plates are rotatably disposed at a fit portion of the object lens in the vertical direction of an optical axis so that the shield plates can be opened/closed and, thus, dark field illumination light that passes through an optical path <NUM> can be shielded, wherein the incident area and incident direction of the dark field illumination light to a ring-shaped lens that emits the dark field illumination light to an object can be varied.

The present invention provides an imaging apparatus for imaging a surface of a specimen according to claim <NUM> and a process for imaging a surface of a specimen according to claim <NUM>.

The present invention modifies a standard BD microscope or other instrument using a BD objective so that in brightfield the BD objective transmits light normally and as described above. In darkfield, the light transmitted through the darkfield channel is limited so that the darkfield illumination is not through the entire <NUM> degree circumference of the BD objective but rather through only a portion of the circumference.

With reference to <FIG> and <FIG> a microscope employing brightfield and darkfield functionality in accordance with this invention is shown and designated by the numeral <NUM>. In this embodiment the microscope <NUM> is equipped with a camera <NUM>. Oculars may also be present, such that <NUM> is to broadly represent oculars and/or a camera. Although the following description will refer to a reflected light microscope, similar techniques apply to transmitted light microscopes or other instruments using BD objectives. The systems generally consist of a light source <NUM> providing light <NUM>, a vertical illuminator <NUM> (light guide), a brightfield/darkfield (BD) switch <NUM> and a BD objective <NUM>. As in a standard BD objective <NUM>, two channels are provided to guide the light to the specimen <NUM>. The light <NUM> is directed to a mirror <NUM> that reflects the light <NUM> toward the specimen <NUM> downwardly through the vertical illuminator <NUM>, the nosepiece <NUM>, and BD objective <NUM>.

The BD switch <NUM>, as schematically shown, serves to limit the light <NUM> to pass either into a brightfield channel <NUM> (<FIG>) or darkfield channel <NUM> (<FIG>) separated by a shield wall <NUM>. With the BD switch <NUM> in a bright field position as in <FIG>, the light <NUM> is limited to a beam that is reflected off of the mirror <NUM> as illuminating light <NUM>' to enter the brightfield channel <NUM>, which directs the illuminating light <NUM>' through the BD objective <NUM> toward the surface S of the specimen <NUM> at an angle perpendicular (<NUM> degrees) to the plane of the specimen <NUM> and allows the reflected light <NUM> to pass to the oculars or camera <NUM>. As seen in Fig. 5A, when the BD switch <NUM> is in a darkfield position the light <NUM> is limited to an annular beam that is reflected off of the mirror <NUM> to enter the darkfield channel <NUM>, which is an annular channel directing light coming therethrough toward the specimen at an angle less than <NUM> degrees and typically <NUM> to <NUM> degrees.

In some embodiments, the darkfield channel <NUM> directs illuminating light toward the specimen at an angle less than <NUM> degrees, in other embodiments, less than <NUM> degrees, in other embodiments, less than <NUM> degrees, in other embodiments, less than <NUM> degrees, in other embodiments, less than <NUM> degrees, in other embodiments, less than <NUM> degrees, in other embodiments, less than <NUM> degrees, in other embodiments, less than <NUM> degrees, and, in other embodiments, less than <NUM> degrees. In some embodiments, the darkfield channel <NUM> directs illuminating light toward the specimen at an angle greater than <NUM> degrees, in other embodiments, greater than <NUM> degrees, in other embodiments, greater than <NUM> degrees, and in other embodiments, greater than <NUM> degrees.

The distance between the distal end of the objective and the specimen is known as the working distance (see Fig. 5A). In some embodiments, the working distance is from <NUM> or more to <NUM> or less. In some embodiments, the working distance is from <NUM> or more to <NUM> or less, and, in other embodiments, from <NUM> or more to <NUM> or less mm. In some embodiments, the working distance is <NUM> or less, in other embodiments, <NUM> or less, in other embodiments, <NUM> or less, in other embodiment, <NUM> or less, in other embodiments, <NUM> or less and, in other embodiments, <NUM> or less.

In some embodiments, the field of view of the BD objective <NUM> is less than <NUM>. In some embodiments, the field of view of the BD objective is less than <NUM>, in other embodiments, less than <NUM>, in other embodiments, less than <NUM>, in other embodiments, less than <NUM>, in other embodiments, less than <NUM>, in other embodiments, less than <NUM>, in other embodiments, less than <NUM>.

When viewing a microscopic specimen at, for example, a size of less than <NUM>, the distance of the microscope objective is often less than <NUM> from the surface of the specimen depending on the working distance of the objective. For example a typical working distance, WD, of a 50x objective is less than <NUM> and, for a 100x objective, is typically <NUM> or less. The physical outside diameter of an objective is typically between <NUM> and <NUM>. By way of example, with a <NUM> diameter specimen and <NUM> WD, the angle of the light projecting off the surface would be approximately <NUM> degrees. In the more likely case of a WD of <NUM> the angle of light projecting on the specimen would be <NUM> degrees. Photometric stereo optimally uses illumination at <NUM> to <NUM> degrees. In most microscope use cases, then, it would not be possible to determine topographies of specimens using photometric stereo or other imaging techniques requiring oblique lighting due to the low incident of oblique illumination.

The present invention uses the darkfield channel of the objective to direct the light onto the surface of the specimen. This allows the light source to be much closer to the vertical axis of illumination. In the above standard illumination the light had to be outside the radius of the objective. The use of the darkfield channel allows the light source to be within the radius of the specimen and essentially be adjacent to the light path. The distance from the vertical axis can now be approximately equal to the WD allowing an angle of illumination to be <NUM> degrees. This angle may vary slightly with the design of the objective but is typically in the range of <NUM> to <NUM> degrees. Thus, the imaging systems according to this invention achieve oblique illumination angles despite the very tight working distances required in many applications. The method taught herein can be used to determine topographies in microscopy applications that could not be achieved by standard methods.

It can be seen in <FIG> that the light path in brightfield (illuminating light <NUM>') is projected through the center of the nosepiece <NUM> and through the brightfield channel <NUM> of the BD objective <NUM>. The reflected light <NUM> is reflected back through the brightfield channel <NUM>, through the nosepiece <NUM> and tube lens <NUM> and is affected by any oculars and/or captured by a camera <NUM>. It is seen here that the illumination light <NUM>' in brightfield is at <NUM> degrees to the general resting plane of the specimen <NUM> and the reflected light <NUM> that is measured travels parallel to the illumination light <NUM>' but in an opposite direction. Fig. 4B shows a schematic cross sectional view of the specimen <NUM> and the brightfield illumination light <NUM>' that is projected onto the specimen <NUM>. The projected brightfield illumination light <NUM>' illuminates the entire field of view.

<FIG> shows the microscope <NUM> in darkfield mode. Here the light <NUM> is blocked by the darkfield switch <NUM> so that no light passes through the brightfield channel <NUM> and is instead directed to pass through the darkfield channel <NUM> as illuminating light <NUM>". As with the embodiment of <FIG> of the prior art, this blocking of the light <NUM> produces an annular beam (or, in other terms, a hollow cylinder or annular cylinder) of light reflected off of mirror <NUM> and projected toward the specimen <NUM>. However, in distinction over the prior art, the entirety of that annular beam of illuminating light <NUM>" does not reach the specimen at an oblique angle determined by the design of the objective <NUM> and wall of the darkfield channel <NUM>. Instead, only a portion of the light at from less than the entire <NUM> degree circumference of the BD objective is delivered down the darkfield channel to reach the specimen, as arced illuminating light <NUM>*. This arced illuminating light <NUM>* still illuminates the entire field of view, but, rather than doing so from the entire <NUM> degree circumference of the objective, does so from a discrete direction of limited degrees (or minutes of arc), i.e., from only a portion of the circumference. In other embodiments, the darkfield projection of arced illuminating light <NUM>* illuminates the entire field of view from a discrete direction of limited degrees (or minutes of arc), and the darkfield illumination is devoid of any additional illumination that would interfere with the surface shading caused by the obliquely introduced arced illuminating light <NUM>*. This is accomplished by positioning a light barrier <NUM> in the path of the illuminating light <NUM>".

In some embodiments, such as that shown in <FIG>, the light barrier <NUM> has a body <NUM> with a darkfield opening <NUM> therein so that unwanted illuminating light <NUM>" is blocked and a desired arced illuminating light <NUM>* passes through the opening to be projected toward the specimen <NUM> through less that the entire <NUM> degree circumference practiced in the prior art. The body <NUM> of the light barrier <NUM> does not let illuminating light <NUM>" pass through, while the darkfield opening <NUM> simply defines an open path for the illuminating light <NUM>", which is then defined as arced illuminating light <NUM>* after being limited by passage through the light barrier opening <NUM>. The light barrier <NUM> also defines a brightfield opening <NUM> for the brightfield channel <NUM> and illuminating light <NUM>', as well as all reflected light whether from brightfield or darkfield illumination.

<FIG> shows a schematic cross sectional view of the specimen <NUM> and the arced of illumination light <NUM>* that is projected onto the specimen <NUM>. The projected arced illuminating light <NUM>* illuminates the entire field of view, but at an oblique angle and from a discrete position. With reference back to <FIG>, it is seen that only the left side of the darkfield channel <NUM> is shown having arced illuminating light <NUM>* traveling therethrough, as that reflects the location of the darkfield opening <NUM> in the light barrier <NUM>. The illumination thus comes from that direction and shines at an oblique angle across the field of view.

In some embodiments, the light barrier <NUM> is secured in the nosepiece <NUM>. In other embodiments not falling under the scope of the invention, the light barrier <NUM> is secured in the vertical illuminator <NUM>. It will be appreciated that the light barrier <NUM> and concepts related herein can be implemented in other ways as well, such as in the BD objective <NUM>.

In some embodiments of the invention, such as that in Fig. 5A, the light barrier <NUM> is mounted in the nosepiece <NUM>, and is secured to a bearing housing <NUM> that is secured to the nosepiece <NUM> without intruding upon the darkfield channel <NUM> and the light traveling therethrough, i.e., it is desirable that the light be unaffected by the encroachment of the bearing housing <NUM> in the darkfield channel <NUM>. The bearing housing <NUM> includes bearings <NUM> permitting the rotation of the light barrier <NUM> to position the darkfield opening <NUM> at a desired position about the circumference of the BD objective <NUM>, thus defining the arced illuminating light <NUM>* projected toward the specimen <NUM>. The rotation is visually represtented in <FIG> by the double-headed arrow A.

In some embodiments, a driver <NUM> serves to rotate the light barrier <NUM> to place the darkfield opening <NUM> in a desired position. In some embodiments, the driver <NUM> is a motor that interacts with the light barrier <NUM> through a belt <NUM>, but gearing and other interactions can be employed. It will be appreciated that the driver <NUM> could also be a manually manipulated driver, such as a wheel or knob geared or belted or otherwise associated with the light barrier <NUM> to rotate it.

In some embodiments, a sensor <NUM> is mounted to the microscope <NUM> at an appropriate location to identify a zero position for the light barrier <NUM>. The sensor <NUM> on the microscope <NUM> will identify the zero position when the sensor aligns with a reference element <NUM> on the light barrier <NUM>. The zero position establishes a known starting position for the light barrier <NUM> and more particularly the darkfield opening <NUM> therein, and this known starting position is used for indexing imaging so that each image recorded by the camera <NUM> has associated with it a known lighting position relative to the specimen.

The camera can be any camera useful in imaging systems and specifically used for imaging specimens intended for topographical analysis. These will often employ a CCD or CMOS sensors.

It will be appreciated that the control of all elements of the microscope can be implemented in known ways, typically with some or all controls being implemented through various hardware and/or software and/or firmware, all represented and designated herein as a processor <NUM>. One or more processors can be used and a myriad of hardware such as joysticks, relays, switches among others. The processor <NUM> can record the images taken from the camera and be programmed with the appropriate algorithms to analyze one or more images and recreate a topographical image of the portion of the specimen imaged.

For the topographical imaging techniques implemented by the processor <NUM>, it is typically necessary or at least helpful to have associated with a particular image the positioning of the incoming oblique light relative to the circumference of the objective. The shading created by the oblique light is dependent upon the position of the incoming light relative to the circumference, and establishing a zero position facilitates the automation of processes for taking multiple images and calculating topographies based upon those multiple images. Once a zero position is established, the processor and associate hardware and/or firmware and/or software can carry out an automated process of providing oblique illumination from a first position about the circumference, taking an image and collecting image data and associating it with the illumination from the first position, then providing oblique illumination from a second position about the circumference, taking an image and collecting image data and associating it with the illumination from the second position positional data; repeating the process as desired to obtain a desired number of imaging data sets from a desired number of illuminating positions. In some embodiments, the sensor <NUM> is an optical proximity sensor, wherein a light shined by the sensor <NUM> is blocked by a reference element <NUM> on the light barrier <NUM> when the sensor <NUM> and reference element <NUM> are aligned. In other embodiments, the sensor <NUM> magnetic position sensor, working by sensing a magnet serving as a reference element. Mechanical limit switches and Hall effect sensors are other examples.

In some embodiments, such as seen in <FIG> the light barrier <NUM> has a spool-like shape with two opposed walls <NUM>, <NUM>, with a separating sidewall <NUM>. A belt such as belt <NUM> (or gearing or other drive mechanisms) can engage the sidewall <NUM> to drive the light barrier <NUM>.

In some embodiments, such as that shown in <FIG>, a light barrier <NUM> has multiple openings represented at darkfield openings 244a and 244b, but any number of openings can be employed taking into account obvious size constraints. The darkfield openings 244a, 244b join to the perimeter of the of the body <NUM> of the light barrier so that moveable plugs 245a and 245b can be employed to selectively block a respective darkfield opening 244a, 244b. In the embodiment of <FIG>the darkfield openings 244a and 244b are opposite one another, and the moveable plugs 245a and 245b are joined, forming a plug unit <NUM> such that when the movable plug 245b blocks darkfield opening 244b, the movable plug 245a is removed from darkfield opening 244a (as in <FIG>) and vice versa (as in <FIG>). This allows light to pass through a desired darkfield opening 244a, 244b, providing the arced illuminating light <NUM>*, and also allows for quick switching of the positioning of the arced illuminating light <NUM>*, by switching the positioning of the plug unit <NUM>. It can be appreciated that multiple slits and moveable plugs may be employed, and that each plug could have its own control as opposed to the common control established in the present exemplary embodiment of <FIG>.

In another embodiment, such as that shown in <FIG>, a light barrier <NUM> has six darkfield openings 344a, 344b, 344c, 344d, 344e, and 344f spaced at <NUM> degrees apart around the circumference of the body <NUM> of the light barrier. Any number and position desired could alternatively be employed. The darkfield openings 344a-f join to the perimeter of the of the body <NUM> of the light barrier <NUM> so that moveable plugs 345a, 345b, 345c, 345d, 345e, and 345f can be employed to selectively block a respective darkfield opening 344a-f. In this embodiment, the movable plugs 345a-f each can be actuated independently to block a respective opening. To visually represent the selective movement, plug 345a is shown removed from its opening 344a in <FIG>, with all other plugs seated to block their respective openings, while, in <FIG>, plug 345b is shown removed from its opening 344b, with all other plugs seated to block their respective openings.

In some embodiments, such plugs can be moved by linear actuators, solenoid, eccentric, or any other known method of motion control. Linear actuators 349a, 349b, 349c, 349d, 349f are employed.

In any embodiment, the size of the arced illuminating light <NUM>* may vary as desired based on results achieved and results desired. This entails a choice of the sizing of the darkfield opening <NUM> (or 244a, 244b) In some embodiments, the arced illuminating light <NUM>* ranges from <NUM> degree or more to <NUM> degrees or less (<NUM> or more to <NUM>,<NUM> or less minutes of arc). In other embodiments, the arced illuminating light <NUM>* ranges from <NUM> degrees or more to <NUM> degrees or less (<NUM>,<NUM> or more to <NUM>,<NUM> or less minutes of arc), in other embodiments, from <NUM> degrees or more to <NUM> degrees or less (<NUM>,<NUM> or more to <NUM>,<NUM> or less minutes of arc), in other embodiments, from <NUM> degrees or more to <NUM> degrees or less (<NUM> or more to <NUM>,<NUM> or less minutes of arc), in other embodiments, from <NUM> degrees or more to <NUM> degrees or less (<NUM> or more to <NUM> or less minutes of arc), and, in other embodiments, from <NUM> degrees or more to <NUM> degrees or less (<NUM> or more to <NUM> or less minutes of arc). The size of the arced illuminating light is dependent upon the size of the darkfield opening <NUM> relative to the arc of the annular darkfield channel <NUM> with which it communicates.

Another aspect of the invention is to use the oblique lighting BD microscopes described above to create a 3D topography by taking multiple images of a specimen <NUM> obliquely illuminated with arced illuminating light <NUM>* from different positions about the <NUM> circumference of the BD objective <NUM> using the light barrier <NUM>, and processing the data from those images in accordance with topographical imaging techniques. The choice of topographical imaging technique is not limited to any particular technique, but, in some embodiments, is selected from shape from shading techniques, photometric stereo techniques, and Fourier ptychography modulation techniques. The processor <NUM> receives the imaging data from the camera <NUM> and is programmed through one or more topographical imaging techniques to generate data used to create a topographical representation of the area of the specimen <NUM> that was imaged. This is represented at output <NUM>. Using known techniques such as shape from shading algorithms, photometric stereo algorithms, and Fourier ptychography modulation algorithms with the know size, number, and position of the arced illuminating light, the angle of the oblique illumination, a 3D topography can be generated.

In some topographical imaging techniques such as shape from shading (SFS), a single obliquely illuminated specimen image generated from arced illuminating light at a single position can be sufficient to generate topographical data and images. In other topographical imaging techniques such as photometric stereo, at least two obliquely illuminated specimen images generated from arced illuminating light at two positions can be sufficient to generate topographical data and images. In other topographical imaging techniques such as Fourier ptychography modultion, at least two obliquely illuminated specimen images generated from arced illuminating light at two positions plus an image from brightfield illumination is needed to generate topographical data, and <NUM> or more obliquely illuminated specimen images will provide even better data for Fourier ptychography modulation. The existing algorithms and algorithms yet to be developed in this field will provide the ordinarily skilled artisan with the knowledge as to the number of type of images needed. The present invention does not invent or alter the algorithms but rather provides methods and apparatus that allows for their implementation.

It will be appreciated that, in some embodiments, the processor <NUM> (which again, represents any number of appropriate processors, hardware, software, firmware), automates the control of the light barrier, the illumination, the image collection and generation of topographical data and/or images.

Thus this invention provides a process for imaging a specimen with an imaging system that employs a BD objective having a darkfield channel and a bright field channel and defining a circumference about the specimen to be imaged. The process includes obliquely illuminating the specimen through the darkfield channel with a first arced illuminating light that obliquely illuminates the specimen through a first arc of the circumference, and taking a first image providing a first image data set of the specimen from the first arced illuminating light reflected off the surface of the specimen. In some embodiments, the process further includes generating a 3D topography of the specimen by processing the first data through a topographical imaging technique. In some embodiments, the arc sizes are selected as described above for the arced illuminating light <NUM>*.

In other embodiments, the process includes, obliquely illuminating the specimen through the darkfield channel with a second arced illuminating light that obliquely illuminates the specimen through a second arc of the circumference of the BD objective different from said first arc, and taking a second image providing a second image data set of the specimen from the second arced of illuminating light reflected off the surface of the specimen. In other embodiments, the process further includes illuminating the specimen through the brightfield channel with brightfield illuminating light, and taking a third image of the specimen from the brightfield illuminating light reflected off the surface of the specimen. In other embodiments, the process further includes repeating said obliquely illuminating step and said taking an image step for any n number of images producing n number of image data sets. In other embodiments, n is from <NUM> to <NUM>, in other embodiments, from <NUM> to <NUM>, in other embodiments, from <NUM> to <NUM>, and in other embodiments, <NUM>.

In other embodiments, said obliquely illuminating steps include providing a light barrier in the darkfield channel, the light barrier having a body that does not permit the passage of light therethrough, and a darkfield opening in the body that does permit the passage of light therethrough, and delivering illuminating light into the darkfield channel to the light barrier and through the darkfield opening to provide the arced illuminating light that obliquely illuminates the specimen.

In other embodiments, the process includes a processor and associate hardware and/or firmware and/or software controlling the oblique illumination of any said oblique illumination step and controlling any said image taking step. In other embodiment a same or different processor and associate hardware and/or firmware and/or software controls said step of generating a 3D topography.

Claim 1:
An imaging apparatus for imaging a surface (S) of a specimen (<NUM>), the imaging apparatus comprising:
a microscope (<NUM>) selected from reflected light microscopes and transmitted light microscopes, the microscope (<NUM>) including:
a BD objective (<NUM>) having a darkfield channel (<NUM>) and a bright field channel (<NUM>), the BD objective (<NUM>) having a circumference and
a light barrier (<NUM>) in the darkfield channel (<NUM>) mounted in a nosepiece of the microscope, the light barrier (<NUM>) having a body (<NUM>) that does not permit the passage of light therethrough, and a darkfield opening (<NUM>) in the body (<NUM>) that does permit the passage of light therethrough, such that the body (<NUM>) blocks illuminating light (<NUM>") traveling through the darkfield channel (<NUM>) toward the specimen (<NUM>), and the darkfield opening (<NUM>, <NUM>, <NUM>) defines a passage for the illuminating light (<NUM>') traveling through the darkfield channel (<NUM>) toward the specimen (<NUM>),
said darkfield opening (<NUM>) thus defining arced illuminating light (<NUM>*) that obliquely illuminates the specimen (<NUM>) through the darkfield channel (<NUM>) from a discrete direction through only an arc of limited degrees from only a portion of the circumference.