Surface color and liquid contact angle imaging

Abstract

An apparatus and method for imaging a side view of an object on a surface, a contact angle of a liquid object, a color of an object, or a combination thereof is disclosed.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority to U.S. Provisional Patent Application No. 62 / 764,888, filed on August 16, 2018, the contents of which are relied upon and are incorporated herein by reference in their entirety. The entire disclosure of any publication or patent document mentioned herein is incorporated by reference in its entirety. Technical Field

[0003] The present invention relates, among other things, to apparatus and methods for performing biological and chemical assays and computational imaging. Background Art

[0004] In biological and chemical assays (eg, diagnostic tests), there is often a need for simple, rapid, and sensitive performance of the assay (including imaging). The present invention provides, among other things, devices and methods for simple, rapid, and sensitive performance of the assay (including imaging). Summary of the invention

[0005] One aspect of the present disclosure provides an apparatus and method for imaging the contact angle, side view, or both of a small liquid droplet on a surface using an adapter attached to a smartphone and using a camera and light source on the smartphone.

[0006] Another aspect of the present disclosure provides an apparatus and method for imaging and analyzing the color of a surface, particularly making the color measurement insensitive to illumination.

[0007] Another aspect of the present invention provides a compact color calibration card within an optical adapter to make color measurements insensitive to illumination.

[0008] Another aspect of the present disclosure provides an apparatus and method capable of easily and flexibly connecting a light source of a smartphone with an optical adapter using optical fibers. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Those skilled in the art will appreciate that the drawings described below are for illustration purposes only. These drawings are not intended to limit the scope of the present invention in any way. The drawings are not drawn entirely to scale.

[0010] Figure 1 A schematic diagram of an optical system is shown in which a smartphone is used to observe and measure the contact angle of a liquid droplet on a surface, such as mammalian skin.

[0011] Figure 2Example smartphone images showing droplets on skin (a) and (b) and droplets on plastic (c) and (d). The focal length of the lens used by the smartphone camera is 8 mm. The wettability of the skin or plastic can be further analyzed on the smartphone using software.

[0012] Figure 3 A schematic diagram of an optical system is shown in which a smartphone images and analyzes the color of a surface.

[0013] Figure 4 A system for imaging an assay device is shown.

[0014] Figure 5 An adapter for imaging an assay device is shown.

[0015] Figures 6 to 8 A schematic diagram of an adapter for imaging an assay device is shown.

[0016] The following detailed description shows some embodiments of the present invention by way of example and not limitation. The section headings and any subheadings used herein are for organizational purposes only and should not be interpreted as limiting the subject matter described in any way. The content under the section heading and / or subheading is not limited to the section heading and / or subheading, but applies to the entire description of the present invention.

[0017] Several exemplary embodiments are shown below:

[0018] An optical adapter that attaches to a smartphone for brightfield and fluorescence microscopy;

[0019] An optical adapter that attaches to a smartphone using an angled-end fiber as a light source for colorimetric measurements;

[0020] An optical adapter for colorimetric measurements that attaches to a smartphone using side illumination of a ring fiber as a light source;

[0021] Tomography apparatus and methods;

[0022] Machine learning assisted measurement and imaging;

[0023] Apparatus and methods for tissue staining and cell imaging; and

[0024] Dual-lens imaging system.

[0025] A-1. Imaging the liquid contact angle and side view of an object on a surface

[0026] Figure 1A schematic diagram of an optical system is shown in which a smartphone is used to observe and measure the contact angle of a small liquid droplet on a surface, such as mammalian skin. Figure 1 Apparatus and methods are shown for imaging the contact angle, side view, or both of a small droplet (and / or other small object) on a surface using an adapter attached to a smartphone and using a camera and light source on the smartphone.

[0027] According to one embodiment, the present disclosure provides an apparatus for imaging a side view of a small object on a surface, comprising: (a) an optical housing (also referred to as an "adapter"), (b) a side mirror; (c) a light source, and (d) a camera;

[0028] wherein the housing is connected to and houses the side mirror, the light source, and the camera, wherein the housing has an opening to fit over a surface having a small object (e.g., a small droplet), wherein the housing prevents or reduces ambient light from entering the interior of the housing during measurement of the small object;

[0029] Wherein, the side mirror is at an inclined angle to the measured optical axis;

[0030] The optical axis of the measurement is determined by an axis passing through the center of the camera and perpendicular to the surface on which the small object is located;

[0031] wherein the light source is above the surface and may have an annular shape, which may be, for example, centrally symmetric relative to a center of the camera; and

[0032] Among them, the camera has an imaging sensor and an imaging lens.

[0033] As an example, Figure 1 An adapter for imaging an assay device according to some embodiments is shown. The adapter includes a housing that can be attached to a smartphone. The adapter has a side-emitting fiber ring, an imaging lens, a reflector, and an opening. Figure 1 In the adapter, a side-emitting fiber is placed around the imaging lens and below the camera. The side-emitting fiber has a circular shape that is symmetrical with respect to the center of the imaging lens. The two end faces of the optical fiber are placed facing the LED of the smartphone. The light emitted by the LED is coupled into the optical fiber through the end face and is uniformly emitted from the optical fiber along the side wall. There is an opening for sampling at the bottom of the adapter. When imaging the contact angle of a droplet on a surface, the adapter can be pressed on the surface and the droplet of interest can be located in the opening area. The reflector is mounted directly below the imaging lens, and the reflector is tilted at, for example, 45 degrees relative to the optical axis of the imaging lens and the camera. The function of the reflector enables the camera to observe the contact angle of the liquid from the side.

[0034] Figure 2 Shown by Figure 1Images of actual droplets (i.e. objects) on different surfaces (i.e. human skin a) and b); and plastic c) and d)) taken by the device shown. The device can see the sidewalls of the adapter and the contact angle of the droplet.

[0035] The entire device can be very compact. The distance between the smartphone camera and the sample surface can be as short as up to 40mm, 30mm, 20mm, 10mm, or any range in between.

[0036] The reflector used in the above embodiments may be, for example, a right-angle prism whose inclined surface is coated with a reflective material, such as aluminum, silver, gold, copper, a high refractive index dielectric material, or a combination thereof.

[0037] The reflector used in the above-described embodiments may be, for example, a plane reflector located on an inclined flat surface.

[0038] The mirror used in the above embodiments may be positioned above the surface where the object is located (ie a small target such as a droplet or the surface itself) and the reflective surface of the mirror intersects the surface and the measurement optical axis.

[0039] The position of the reflector used in the above-described embodiments may be, for example, below the surface on which the small object lies (if the surface is transparent), and the reflective surface of the reflector intersects the surface and the measuring optical axis.

[0040] A2. Surface color measurement

[0041] Another aspect of the present disclosure provides an apparatus and method for imaging and analyzing the color of a surface, more particularly making the color measurement insensitive to illumination. Another aspect of the present invention provides a compact color calibration card (ie, reference color pattern) within an optical adapter to make the color measurement insensitive to illumination.

[0042] like Figure 3 As shown, a reference color pattern is provided inside the adapter. When imaging the sample surface, the adapter is configured so that the reference color pattern or reference card and the sample surface to be imaged are imaged simultaneously in the same field of view of the imager (e.g., a smartphone camera). With the aid of the reference color pattern, the color of the sample surface can be analyzed. The reference color pattern can minimize errors caused by changes in the illumination and camera settings of the smartphone. The reference color pattern has a predetermined known color pattern. The reference color pattern has been pre-characterized under different lighting conditions, so that by comparing the actual imaged surface with the reference color pattern, the true color of the object can be recovered from the surface image taken under unknown lighting conditions.

[0043] The device can also be used to observe the color and detailed features of hair on a surface.Hair can include, for example, head hair and other body hair, as well as other sources of hair and hair-like fibers.

[0044] The device can also be used to observe the color and detailed features of human or animal anatomical structures (such as the ear or nose) by pressing the opening of the adapter against the anatomical structure.

[0045] In some embodiments, the reflector and the reference color pattern may be placed in a single adapter.

[0046] In some embodiments, multiple reflectors, multiple reference color patterns, or both may be placed in a single adapter.

[0047] According to one embodiment of the present disclosure, a device for measuring the color of a surface includes: (a) an optical housing (also called an "easy adapter"), (b) a color reference, (c) a light source, and (d) a camera.

[0048] The housing connects and houses the side mirror, the light source and the camera. The housing has an aperture or opening to fit or be placed on a surface having an object (e.g., a droplet), and the housing prevents or reduces ambient light from entering the interior of the housing during measurement of the object. The color reference provides a predetermined color or color spectrum for comparison with the color of the object. The light source may be in close proximity to the object or surface and may have a circular shape that is centrally symmetrical relative to the center of the camera. The camera may have, for example, an imaging sensor and an imaging lens.

[0049] Other examples:

[0050] 1. A device for irradiating and imaging an object, comprising:

[0051] Imaging lens;

[0052] Reflector;

[0053] Ring irradiator;

[0054] an opening for sampling the surface;

[0055] wherein the opening area is illuminated by light from the annular illuminator;

[0056] The imaging lens collects light reflected by the reflector toward a camera in the smartphone.

[0057] 2. A device for irradiating and imaging an object, comprising:

[0058] Imaging lens;

[0059] Reflector;

[0060] Ring irradiator;

[0061] an opening for sampling the surface;

[0062] Refer to the color pattern;

[0063] Wherein, the reference color pattern and the sampling surface can be viewed in the same field of view of a smartphone camera.

[0064] 3. A device for irradiating and imaging an object, comprising:

[0065] A smartphone, the smartphone comprising a camera and a light source;

[0066] A device for irradiating and imaging an object, comprising:

[0067] Imaging lens;

[0068] Reflector;

[0069] Ring irradiator;

[0070] an opening for sampling the surface;

[0071] Wherein, light emitted from the light source of the smartphone is coupled into the annular illuminator.

[0072] 4. An apparatus, device or method according to any preceding embodiment, wherein the reflector may be below the imaging lens and the angle thereof may be selectable.

[0073] 5. An apparatus, device or method according to any preceding embodiment, wherein the reflector located below the imaging lens can redirect the side view of the object to the imaging plane of the camera.

[0074] 6. An apparatus, device or method according to any of the preceding embodiments, wherein the reflector is tilted relative to the optical axis, and its tilt angle can be, for example, 20 degrees, 30 degrees, 40 degrees, 50 degrees, 60 degrees, 70 degrees, 80 degrees, including intermediate values ​​or ranges.

[0075] 7. A device, apparatus or method according to any preceding embodiment, wherein the annular illuminator is made of side-emitting fiber.

[0076] 8. An apparatus, device or method according to any of the preceding embodiments, wherein the diameter of the imaging lens is in millimeters and is at least 2 mm, 3 mm, 4 mm, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 40 mm or 50 mm, including intermediate values ​​or ranges.

[0077] 9. An apparatus, device or method according to any preceding embodiment, wherein the distance between the smartphone and the sample is in millimeters and is a maximum of 40 mm, 30 mm, 20 mm, 10 mm, including intermediate values ​​or ranges.

[0078] 10. In some embodiments, the apparatus, device or method according to any of the preceding embodiments, wherein the color reference pattern located below the imaging lens redirects the side view of the object to the imaging plane camera.

[0079] 11. In some embodiments, according to any of the aforementioned embodiments, the device, apparatus or method, wherein the color reference pattern is tilted relative to the optical axis, and its tilt angle can be, for example, 20 degrees, 30 degrees, 40 degrees, 50 degrees, 60 degrees, 70 degrees, 80 degrees, including intermediate values ​​or ranges.

[0080] 12. In some embodiments, the device, apparatus or method according to any preceding embodiment, wherein the illuminator is made of an active light source.

[0081] 13. In some embodiments, the surface of interest in the measurement is a human skin area. A color reference can be used to measure the exact skin absorption spectrum. Therefore, the observed color of the skin area under different illumination spectra can be predicted.

[0082] A-3. Method and apparatus for supporting change of light source position

[0083] Another aspect of the present disclosure provides an apparatus and method capable of easily and flexibly connecting a light source of a smartphone with an optical adapter using optical fibers.

[0084] Figure 4 A system for imaging an assay device according to some embodiments is shown. Figure 4 In the present invention, a light guide receives light from a light source of a smartphone and then redirects the light received from the light source to a second reflector. The second reflector reflects the light received from the light guide toward the first reflector. The first reflector reflects the light received from the second reflector toward a second plate of the assay device. In response to the light reflected by the second reflector toward the second plate, some light is transmitted from the first plate of the assay device due to light scattering by a liquid sample in the assay device. The light transmitted from the first plate of the assay device is collected by an imaging lens and directed to a camera in the smartphone.

[0085] Figure 5An adapter for imaging an assay device according to some embodiments is shown. The adapter has a housing that can be attached to a smartphone. The adapter has a light guide, a first reflector, a second reflector, and an imaging lens located within its housing. Depending on the implementation or design, the diameter of the imaging lens is at least 2 mm, 3 mm, 4 mm, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 40 mm, or 50 mm, or in a range between any two values. The housing of the adapter has an entrance aperture, an exit aperture, a first exposure aperture, and a second exposure aperture. During operation, a light source of the smartphone emits light toward a first end of the light guide through the entrance aperture of the housing so that the light is further transmitted toward a second end of the light guide. The light emitted from the second end of the light guide is reflected by the second mirror and the first mirror, respectively, and is used to illuminate the assay device. When the assay device is illuminated through the first exposure aperture, some light is transmitted from a first plate of the assay device due to light scattering by a liquid sample in the assay device. The imaging lens collects light transmitted from the first plate of the assay device through the second exposure aperture and directs the collected light to a camera in the smartphone.

[0086] Figures 6 to 8 is a schematic diagram of an adapter for an imaging and assay device according to some embodiments. Figures 6 to 8 In, the adapter includes a base module and an insert module. The base module includes an imaging lens, a first reflector, and a second reflector. The insert module includes a light guide. Depending on the implementation or design, the diameter of the imaging lens can be, for example, at least 2 mm, 3 mm, 4 mm, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 40 mm, or 50 mm, or within a range between any two values. Figure 6 In the case of a first type of plug-in module, the first type is combined with the base module to form an adapter for use with a smartphone (ie, Type A). Figure 7 In the case of a plug-in module, the plug-in module is disassembled and separated from the base module. Figure 8 In the case of a second type of plug-in module, the second type is combined with the base module to form an adapter for use with a smartphone (ie, Type B). Figure 6 In the Type A smartphone shown, the camera and the light source are separated by a distance SA. Figure 8 In the Type B smartphone shown, the camera and the light source are separated by a distance SB. Figure 6 The middle is the distance SA, Figure 8 SB is the distance in the middle. When the same base module is combined with the corresponding plug-in module, the same base module can be used for both Type A smartphones and Type B smartphones to form an adapter.

[0087] Figure 6 and Figure 8The insert modules in each of the plurality of light guides have different offset distances between a first center of the first end of the light guide and a second center of the second end of the light guide along a direction parallel to the surface of the smartphone. Figure 6 and Figure 8 When the condition SA+LA=SB+LB is satisfied, the same base module can be used in the adapter for Type A smartphone and the adapter for Type B smartphone.

[0088] In some embodiments, by inserting a set of modules (e.g. Figure 6 and Figure 8 In some embodiments, the offset distance can be selectively changed within a range of 2 mm to 40 mm. Depending on the implementation or design, the offset distance is at least 2 mm, 3 mm, 4 mm, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 40 mm, or 50 mm, or within a range between any two values.

[0089] like Figure 5 or Figures 6 to 8 The adapter shown in any of the above may have many other embodiments, variations or improvements. In some embodiments, the light guide may be formed of an optical fiber. In some embodiments, the adapter may include an optical concentrator configured to be placed in front of the light source of the smartphone to enhance the light coupling between the light source and the first end of the light guide.

[0090] In some embodiments, the housing may contain an imaging lens, a first reflector, a second reflector, and a light guide, while relying on some apertures to receive or emit light. For example, the housing may have an entrance aperture, an exit aperture, a first exposure aperture, and a second exposure aperture, such as Figure 5 In some embodiments, the housing of the base module may contain an imaging lens, a first reflector, and a second reflector, and rely on some holes to receive or emit light. For example, the housing of the base module may have an interface hole, an exit hole, a first exposure hole, and a second exposure hole, such as Figures 6 to 8 As shown. Figures 6 to 8 In some embodiments, any hole of the adapter can be covered with a window that is substantially transparent to the wavelength of light being concerned. In some embodiments, all of these holes can be covered with windows to prevent dust and debris from falling into the housing.

[0091] Examples of light guides for different light source positions.

[0092] 1. A device for irradiating and imaging an object, comprising:

[0093] Imaging lens;

[0094] A first reflector;

[0095] A second reflector;

[0096] Light guide;

[0097] a slot for holding an assay device;

[0098] in:

[0099] The light guide receives light from a light source of the smartphone and redirects the received light to the second reflector;

[0100] the second reflector reflects light received from the light guide toward the first reflector;

[0101] wherein the first reflector reflects light received from the second reflector toward a second plate of the measuring device; and

[0102] The imaging lens collects light transmitted from the first plate of the assay device and directs the collected light toward a camera in the smartphone.

[0103] 2. A device for irradiating and imaging an object, comprising:

[0104] A base module, the base module having an imaging lens, a first reflector, and a second reflector;

[0105] an insert module having a light guide;

[0106] a slot for holding an assay device;

[0107] wherein, when the insertion module is engaged with the base module, the light guide receives light from a light source of the smartphone and redirects the received light to the second reflector;

[0108] the second reflector reflects light received from the light guide toward the first reflector;

[0109] The first reflector reflects light received from the second reflector toward a second plate of the measuring device; and

[0110] The imaging lens collects light transmitted from the first plate of the assay device and directs the collected light toward a camera in the smartphone.

[0111] 3. A method for irradiating and imaging a liquid sample between two parallel plates in an assay device, the method comprising the steps of:

[0112] (a) causing a light source of a smartphone to emit light toward a first end of a light guide so that the light is transmitted toward a second end of the light guide;

[0113] (b) directing light emitted from the second end of the light guide toward a second reflector;

[0114] (c) reflecting, by the second reflector, light received from the second end of the light guide toward the first reflector;

[0115] (d) reflecting, by the first reflector, the light received from the second reflector toward a second plate of the measuring device; and

[0116] (e) collecting light transmitted from the first plate of the measuring device by the imaging lens and directing the collected light to the camera in the smartphone.

[0117] 4. A method for irradiating and imaging a liquid sample between two parallel plates in an assay device, the method comprising the steps of:

[0118] (a) engaging an insert module with a base module, wherein the insert module comprises a light guide, and wherein the base module comprises an imaging lens, a first reflector, and a second reflector;

[0119] (b) after the insertion module is connected to the base module, causing a light source of the smartphone to emit light toward the first end of the light guide so that the light is transmitted toward the second end of the light guide;

[0120] (c) directing light emitted from the second end of the light guide in the insert module toward the second reflector in the base module;

[0121] (d) reflecting, by the second reflector in the base module, light received from the second end of the light guide in the plug-in module toward the first reflector in the base module;

[0122] (e) reflecting, by the first reflector, the light received from the second reflector toward a second plate of the measuring device; and

[0123] (f) collecting light transmitted from the first plate of the measuring device by the imaging lens and directing the collected light to the camera in the smartphone.

[0124] 5. The apparatus, device or method of any preceding embodiment, wherein:

[0125] The light guide is formed by an optical fiber.

[0126] 6. The apparatus, device or method according to any preceding embodiment, further comprising:

[0127] An optical concentrator is configured to be placed in front of the light source of the smartphone to enhance light coupling between the light source and the first end of the light guide.

[0128] 7. The apparatus, device or method according to any preceding embodiment, further comprising:

[0129] separating the insert module from the base module;

[0130] An alternative plug-in module is engaged with the base module, wherein the alternative plug-in module includes light guides having a different configuration than the light guides in the plug-in module.

[0131] 8. The device, apparatus or method of any preceding embodiment, wherein the imaging lens, the first reflector, the second reflector and the light guide are placed inside a housing.

[0132] 9. The device, apparatus or method of any preceding embodiment, wherein the light guide is placed inside a housing of the plug-in module.

[0133] 10. The apparatus, device or method of any preceding embodiment, wherein the imaging lens, the first reflector and the second reflector are placed inside a housing of the base module.

[0134] 11. An apparatus, device or method according to any of the preceding embodiments, wherein the imaging lens, the first reflector and the second reflector are placed inside the shell of the base module; and wherein the shell includes an entrance hole, an exit hole, a first exposure hole and a second exposure hole.

[0135] 12. An apparatus, device or method according to any of the preceding embodiments, wherein the imaging lens, the first reflector and the second reflector are placed inside the shell of the base module; and the shell of the base module includes an interface hole, an exit hole, a first exposure hole and a second exposure hole.

[0136] 13. The device, apparatus or method according to any preceding embodiment, wherein the interface hole, the outlet hole, the first exposure hole and the second exposure hole on the shell of the base module are covered with transparent windows.

[0137] 14. The apparatus, device or method according to any preceding embodiment, comprising:

[0138] The light source of the smart phone is caused to emit light through the entrance hole of the base module toward the first end of the light guide.

[0139] 15. The apparatus, device or method according to any preceding embodiment, comprising:

[0140] Light emitted from the second end of the light guide in the plug-in module is directed to the second reflector in the base module through the interface hole of the base module.

[0141] 16. The apparatus, device or method according to any preceding embodiment, comprising:

[0142] The light received from the second reflecting mirror is reflected by the first reflecting mirror toward the second plate of the measuring device through the first exposure hole of the base module.

[0143] 17. The apparatus, device or method according to any preceding embodiment, comprising:

[0144] Light transmitted from the first plate of the assay device is collected by the imaging lens through the second exposure aperture of the base module.

[0145] 18. The apparatus, device or method according to any preceding embodiment, comprising:

[0146] collecting light transmitted from the first plate of the assay device through the second exposure aperture of the base module by the imaging lens; and

[0147] The collected light is directed by the imaging lens through an exit exposure to a camera in a smartphone.

[0148] 19. The apparatus, device or method of any preceding embodiment, wherein:

[0149] By selecting an insertion module from a group of insertion modules, an offset distance between a first center of the first end of the light guide and a second center of the second end of the light guide along a direction parallel to the surface of the smartphone can be selectively changed.

[0150] 20. The apparatus, device or method of any preceding embodiment, wherein:

[0151] An offset distance between a first center of the first end of the light guide and a second center of the second end of the light guide along a direction parallel to the surface of the smartphone is a selectively variable range, and the variable range is between 2 mm and 40 mm.

[0152] 21. An apparatus, device or method according to any of the preceding embodiments, wherein the variable range is at least 2 mm, 3 mm, 4 mm, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 40 mm, or 50 mm, or within a range between any two of the values.

[0153] 22. An apparatus, device or method according to any of the preceding embodiments, wherein the diameter of the imaging lens is at least 2 mm, 3 mm, 4 mm, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 40 mm, or 50 mm, or within a range between any two of the values.

Claims

1. An apparatus for imaging a side view of an object on a surface, comprising: (a) Housing; (b) Side mirrors; (c) light source; and (d) a camera, wherein: The housing has an entrance aperture for light incidence, an exposure aperture for imaging, and an exit aperture for illuminating and observing an object on the surface; The housing accommodates the side mirror, the lens, and a light guide for receiving light from a light source through an incident hole and illuminating an object; The exposure aperture, side mirror, lens and exit aperture are optically aligned to facilitate imaging by the camera by capturing a side view of an object in the side mirror; and The side mirror is at an angle that deviates from perpendicular to the surface.

2. A method for imaging a side view of an object on a surface using the apparatus of claim 1, comprising: (a) providing the device; (b) placing the object on the surface; and (c) illuminating the object through an exit hole using the light source and light guide, wherein a side view of the object in the side mirror is captured using the camera.

3. The apparatus according to claim 1, further comprising: A color reference card is located in the housing, wherein the camera looks at the color reference card and at least a portion of the surface is in the same field of view.

4. The device according to claim 1, wherein the side mirror is inclined relative to the vertical direction of the surface, and the inclination angle is 50 degrees, 60 degrees, 70 degrees, 80 degrees or in a range between any two of the above values.

5. The device of claim 1, wherein the light guide is a ring illuminator comprising side-emitting optical fibers and forming a ring shape.

6. The apparatus of claim 1, wherein the distance between the camera and the surface is at most 20 mm.

7. The device of claim 1, wherein the housing prevents or reduces ambient light from entering an interior of the housing.

8. The apparatus of claim 1, wherein the camera is part of a smartphone.

9. The method of claim 2, wherein the imaging uses machine learning.

10. The apparatus of claim 1, wherein the object is a drop of liquid on the surface.

11. The device of claim 1, wherein the object is hair.

12. The device of claim 1, wherein the housing further comprises a plurality of mirrors, a plurality of patterns of reference colors, or both.

13. The device of claim 1, wherein the housing further comprises a second mirror.

14. The method of claim 2, further comprising a color reference card within the housing; wherein The camera looks at the color reference card and at least a portion of the surface in the same field of view.

15. The method of claim 2, wherein the housing prevents or reduces ambient light from entering an interior of the housing.

16. The method according to claim 2, wherein: The object is a drop of liquid on a flat surface.

17. The method according to claim 2, wherein: The object is hair.

18. The method of claim 2, wherein the housing further comprises a plurality of mirrors, a plurality of patterns of reference colors, or both.

19. The method of claim 2, wherein the housing further comprises a second mirror.

20. The method of claim 2, wherein the object is a liquid on a surface, and further comprising the step of measuring a contact angle of the liquid on the surface based on the image.

21. The method of claim 2, wherein the object is a droplet of liquid on a mammalian skin surface.

22. The apparatus of claim 1, wherein the imaging uses machine learning.

23. The apparatus of claim 1, wherein the camera has an imaging lens having a diameter of at least 2 mm, 3 mm, 4 mm, 5 mm, or any value in the range of any two of the foregoing values.

24. The apparatus of claim 1, wherein the distance between the camera and the sample surface is in the range of 10 mm to 20 mm.

25. The apparatus of claim 1, wherein the object is a drop of liquid on the surface, and imaging of a side view of the object is used to measure a contact angle of the liquid.

26. The method of claim 2, wherein the light guide is a ring illuminator comprising side-emitting optical fibers and formed in a ring shape.

27. The device according to claim 1, wherein: The side mirror is inclined relative to the vertical direction of the surface, and the inclination angle thereof is 45 degrees.

28. The device according to claim 1, wherein The side mirror is inclined relative to the vertical direction of the surface, and its inclination angle is 20, 50 or any value therebetween.

29. The device according to claim 1, wherein The side mirror is inclined relative to the vertical direction of the surface, and the inclination angle thereof is 50, 60 or any value therebetween.

30. The apparatus of claim 1, wherein the distance between the camera and the surface is in the range of 20 mm to 40 mm.

31. The method of claim 2, wherein the side mirror is tilted relative to a vertical direction of the surface, and the tilt angle is 45 degrees.

32. The method of claim 2, wherein the side mirror is tilted relative to the vertical direction of the surface, and the tilt angle in degrees is 20 degrees, 50 degrees, or any value in between these two values.

33. The method of claim 2, wherein the side mirror is tilted relative to a vertical direction of the surface, and the tilt angle is 50 degrees, 60 degrees, 70 degrees, 80 degrees, or a value between any two of the foregoing values.

34. The method of claim 2, wherein the distance between the camera and the surface is in the range of 20 mm to 40 mm.

35. The method of claim 2, wherein: The distance between the camera and the surface is at most 20 mm.

Images