IMPROVEMENTS IN OR RELATING TO A DEVICE FOR IMAGING

Abstract

A substrate for facilitating the measurement, using Total Internal Reflection microscopy, of the status of an assay; a first surface including a test site at which one or more reagents for the assay are immobilised; a second surface substantially parallel to the first surface; a third surface joining the first and second surfaces; a fourth surface joining the first and second surfaces; wherein three characteristics of the surfaces are manipulated to ensure that light launched through the third surface impinges on the centre of the first surface solely at the test site and then undergoes Total Internal Reflection; wherein the three characteristics are: the length of the first and second surfaces between the third and fourth surfaces; the length of the third and fourth surfaces; the angle subtended between the first and third surfaces.

Claims

1: A substrate for facilitating the measurement, using a Total Internal Reflection based optical imaging system, of the status of an assay; the substrate comprising: a first surface including a test site at which one or more reagents for the assay are immobilised; a second surface substantially parallel to the first surface; a third surface joining the first and second surfaces; a fourth surface joining the first and second surfaces; wherein three characteristics of the surfaces are manipulated to ensure that light launched through the third surface impinges on the first surface substantially at the test site and then undergoes Total Internal Reflection; impinges on the fourth surface and is partially reflected to impinge on the second surface; wherein the reflected light forms a closed loop reflection pattern; wherein the three characteristics are: the length of the first and second surfaces between the third and fourth surfaces; the length of the third and fourth surfaces; the angle subtended between the first and third surfaces.

2: The substrate according to claim 1, wherein at least a portion of the light is transmitted through the fourth surface.

3: The substrate according to claim 1, wherein the angle subtended between the first and third surfaces is between 70 and 90.

4: The substrate according to claim 1, wherein the closed loop reflection pattern is a symmetrical pattern.

5: The substrate according to claim 1, wherein the closed loop reflection pattern is a diamond pattern.

6: The substrate according to claim 1, wherein the closed loop reflection pattern comprising more than one diamond.

7: The substrate according to claim 1, wherein the substrate is glass.

8: The substrate according to claim 1, wherein at least one of the surfaces of the substrate is polished.

9: The substrate according to claim 1, wherein the length of the first and second surfaces between the third and fourth surfaces is 5 to 130 mm.

10: The substrate according to claim 1, wherein length of the third and fourth surfaces is between 0.5 and 10 mm.

11: The substrate according to claim 1, wherein the first surface of the substrate forms part of a microfluidic channel.

12: A Total Internal Reflection (TIR) based optical imaging system for reducing unwanted light scattering at a test site of the substrate of claim 1, the system comprising: an incident beam which illuminates the test site at such an angle to facilitate TIR; wherein a portion of the incident beam is reflected at the fourth surface of the substrate; a closed reflection loop formed by the reflected portion of the incident beam, which at least partly follows the same path within the substrate as the incident beam; and wherein by at least partly following the same path as the incident beam, the closed reflection loop reduces unwanted light scattering by avoiding interaction with features of the substrate which could cause the beam to scatter.

13: The system according to claim 12, further comprising a light source.

14: The system according to claim 12, further comprising a detector.

15: The system according to claim 14, wherein the detector further comprises imaging optics and an imaging sensor.

Description

FIGURES

[0032] The present invention will now be described, by way of example only, with reference to the accompanying figures in which:

[0033] FIG. 1 shows a typical Total Internal Reflection microscope setup;

[0034] FIG. 2 shows a substrate with an incident beam undergoing a Fresnel reflection at the air-glass interface at the input face of the substrate;

[0035] FIG. 3 shows the substrate of FIG. 2, with an additional Fresnel reflection at the air-glass interface at the output face of the substrate;

[0036] FIG. 4 shows a diamond-shaped light path within the substrate;

[0037] FIG. 5 shows the substrate of FIG. 4 including a microfluidic channel;

[0038] FIG. 6 shows the reflected beam interacting with the features within an overly long substrate;

[0039] FIG. 7 shows a light beam interacting with the corner of a substrate at the output face of an overly long substrate;

[0040] FIG. 8 shows a closed reflection loop with two Total Internal Reflections on each pass through the substrate; and

[0041] FIG. 9 shows a closed reflection loop within a dove prism-shaped substrate.

DETAILED DESCRIPTION

[0042] FIG. 1 shows a Total Internal Reflection based optical imaging system that is a microscopy system and a substrate 10. The substrate comprises a first surface 12 which is the location of the test site 22, a second surface 14, a third surface 16 which is also the input surface for the incident beam 20, and a fourth surface 18 which is also the output surface for the output beam 24. Using the Total Internal Reflection microscopy architecture shown in FIG. 1, a sample located at the test site 22 can be interrogated by the incident beam 20. The incident beam 20 refracts on transmission through the third surface 16 and undergoes Total Internal Reflection at the test site 22. The subsequent optical radiation produced by the sample can be imaged by a lens 26 onto an image sensor 28. After undergoing Total Internal Reflection, the beam refracts again on transmission through the fourth surface 18.

[0043] FIG. 1 considers only the dominant transmitted beams, and does not depict weaker reflected beams. The light refracting at the third surface 16 and the fourth surface 18, can be a major source of background signal in TIR images. Fresnel reflections occur at the interface between two materials with different refractive indices. Referring to FIG. 2, the Fresnel reflection of light 30 as the incident beam 20 impinges on the third surface 16 is shown. Referring to FIG. 3, an additional Fresnel reflection 32 is shown as light impinges at the fourth surface 18 after undergoing Total Internal Reflection at the test site 22.

[0044] The scattered light resulting from Fresnel reflections within the substrate 10 can be can be directly or indirectly collected by the imaging lens 26 and directed onto the image sensor 28. This will increase the background level of the images obtained using the system, with the exact background distribution dependent on the specific nature of the deleterious scattering sites. This subsequently reduces the signal-to-background ratio and signal-to-noise ratio of the images and reduces the sensitivity of the TIR system.

[0045] According to the present invention, the surfaces of the substrate 10 may be manipulated such that light launched through the third surface 16 impinges at the centre of the first surface 12 solely at the test site 22 and then undergoes Total Internal Reflection, as shown in FIG. 3. The characteristics of the substrate can be manipulated such that the Fresnel reflection 32 reflects from the fourth surface 18 and back towards the centre of the substrate 10. FIG. 3 shows a substrate 10 with an angle subtended between the first surface 12 and third surface 16 of 90. Along with the angle subtended between the surfaces, the length of the surfaces may manipulated such that the reflected beam 32 is incident on the second surface 14 of the substrate 10, as shown in FIG. 3.

[0046] Although FIGS. 1 to 3 provide an example system that is based around microscopy, it will be understood that, in some embodiments, the optical imaging system may not magnify the image or, indeed, may de-magnify the image.

[0047] Referring to FIG. 4, according to the present invention, the characteristics of the substrate 10 may be manipulated such that the reflected beam 32 is incident on the second surface 14 of the substrate 10 at the same angle as the incident beam 20 is incident on the first surface 12, and therefore also undergoes Total Internal Reflection. As shown in FIG. 4, the light path within the substrate may form a diamond-shaped loop. The Fresnel reflected beam 34 spatially overlaps with the incident beam 20 at the third surface 16 and a portion of the Fresnel reflected beam is reflected at the third surface 16 and continues to travel along the diamond-shaped loop.

[0048] Referring to FIG. 5, the substrate 10 may form part of a microfluidic channel 36. The diamond light path may perfectly aligned with the microfluidic channel 36, as shown in FIG. 5, such that there is no interaction between the light path and the features of the microfluidic channel 36. The diamond loop would continue indefinitely, growing continually weaker on each reflection until the number of photons in the beam is reduced to a point where no further reflection occurs.

[0049] FIG. 6 shows an example of a substrate 10 wherein the three characteristics of the surfaces have not been manipulated to ensure that light launched through the third surface impinges on the centre of the first surface 12 solely at the test site 22. As shown in FIG. 6, the length of the substrate 10 is overly long, which causes the reflected beam 34 reflected from the second substrate 14, to be incident on the features of the microfluidic channel 36. At the site of scattering 38, light is scattered across a wide range of directions, including directly into the imaging lens 26, and into other parts of the system that are in the field of view of the image sensor 28. A similar outcome would also occur if the angle of the incident beam 20 was too steep.

[0050] Referring to FIG. 7, an additional example of a substrate 10 which is overly long is shown. After undergoing Total Internal Reflection at the test site 22, the beam of light 42 interacts with the corner of the substrate 10 at the fourth surface 18, resulting in an unwanted scattering site 40 due to the non-planar surface and the typically lower optical quality achieved at corners, i.e., bevels, chipping, cracking.

[0051] Referring to FIG. 8, an example of a closed reflection loop 44 is shown in which the light beam undergoes two total internal reflections on each pass through the substrate 10.

[0052] Referring to FIG. 9 an example of a substrate 10 where the angles subtended between the first 12 and third surfaces 12 is not 90 is shown. The prism geometry of the substrate enables the closed reflection loop 46 to be perfectly reflected back and forth between the third surface 16 and the fourth surface 18.

[0053] Various further aspects and embodiments of the present invention will be apparent to those skilled in the art in view of the present disclosure.

[0054] and/or where used herein is to be taken as specific disclosure of each of the two specified features or components with or without the other. For example A and/or B is to be taken as specific disclosure of each of (i) A, (ii) B and (iii) A and B, just as if each is set out individually herein.

[0055] Unless context dictates otherwise, the descriptions and definitions of the features set out above are not limited to any particular aspect or embodiment of the invention and apply equally to all aspects and embodiments which are described.

[0056] It will further be appreciated by those skilled in the art that although the invention has been described by way of example with reference to several embodiments. It is not limited to the disclosed embodiments and that alternative embodiments could be constructed without departing from the scope of the invention as defined in the appended claims.