Optical system

Abstract

An optical system comprising: a fluid-tight housing having an interior that is configured, in use, to be filled at least partially with an optically transparent medium; at least one reflector disposed at least in part within the interior; and a pressure compensator operably connected to the fluid-tight housing and configured to minimise a pressure differential between the interior of the fluid-tight housing and an environment exterior of the fluid-tight housing.

Description

[0001] OPTICAL SYSTEM

[0002] The present disclosure relates to the field of optical systems, more particularly to submergible optical systems. The disclosure also relates to the use of optical systems, in particular to underwater use of optical systems.

[0003] The project leading to this application has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No.

[0004] 101000858.

[0005] A diverse range of biological and biomolecular sensing techniques across industries -from food safety to medicine to environmental monitoring - rely on optical, e.g. fluorometric, detection of a signal molecule or ‘reporter’ bound to an analyte. For example, these techniques can report the abundance and activities of nucleic acids, metabolites, and proteins within complex solutions. These techniques may be used to identify the concentration and structure of molecules in a liquid by identifying the visual spectrum emitted from a sample after it is excited by incident light. These optical systems typically operate on the bench in laboratories, at atmospherics pressures and surrounded by air.

[0006] Optical systems, e.g. including fluorometers, capable of being deployed underwater may be useful in many applications including environmental monitoring, oceanographic research, oil spill detection and water quality measurements.

[0007] For example, fieldwork in freshwater and / or saltwater environments in in cases where humans are impacted or environment change is detrimental can be time-sensitive, requiring a response or change to prevent harm. Typically, this requires the systems to be contained withing pressure-tight fluid-tight housings, often made of titanium. These fluid-tight housings are both expensive and difficult to manufacture, especially when such systems are intended for use at great depths below the ocean and need to withstand high pressure differentials.

[0008] A first aspect provides an optical system comprising:

[0009] a fluid-tight housing having an interior that is configured, in use, to be filled at least partially with an optically transparent medium;at least one reflector disposed at least in part within the interior; and a pressure compensator operably connected to the fluid-tight housing and configured to minimise a pressure differential between the interior of the fluid-tight housing and an environment exterior of the fluid-tight housing.

[0010] The optical system may not need a pressure-tight fluid-tight housing to function in environments where there is a pressure differential between an interior and exterior of the fluid-tight housing.

[0011] One or more of the reflectors may be operable to produce collimated light from uncollimated light and / or vice versa. One or more of the reflectors may be operable to produce focused light from collimated light and / or vice versa.

[0012] The optical system may collimate and / or focus light independent of the refractive index of the optically transparent medium within the interior of the fluid-tight housing.

[0013] At least one, for example all, of the reflectors may include a mirror. One or more, e.g. all, of the reflectors may include a parabolic mirror and / or at least one of the reflectors may include a spherical mirror. One or more of the parabolic mirrors may be an off-axis parabolic mirror. One or more, e.g. all, of the reflectors may be include a retroreflector.

[0014] A fill port may be configured to allow a material, e.g. the optically transparent medium or one or more ingredients or precursors thereof, to be introduced into and / or drained from the interior of the fluid-tight housing. The fill port may be disposed at least partially within a wall of the fluid-tight housing.

[0015] The pressure compensator may be disposed at least partially within a wall of the fluid-tight housing. The pressure compensator may include a syringe or a piston in fluid communication with the interior. The pressure compensator may include an elastic zone configured to deform, in use, thereby increasing or reducing a volume including the interior, to minimise the pressure differential between the interior and the environment exterior of the fluid-tight housing.

[0016] The fluid-tight housing may comprise, or consist essentially of, a polymeric material such as a plastic. This may make the optical system easy and relatively inexpensive tomanufacture. For example, the fluid-tight housing or a part thereof may be manufactured using 3D printing. Other fabrication techniques including CNC machining and injection moulding may be used. Any suitable fabrication technique may be used.

[0017] The optical system may include at least one light source. One or more of the light sources may be disposed at least partially within the interior of the fluid-tight housing. One or more of the light sources may be configured to emit uncollimated light. One or more of the light sources may include a light emitting diode (LED) or a laser. In use, light, e.g. uncollimated light, emitted by the light source may be incident upon one or more of the reflectors and be reflected therefrom, e.g. as collimated light.

[0018] The optical system may include one or more sample holders configured to hold, in use, a sample for optical analysis. One or more of the sample holders may be disposed at least partially within the interior of the fluid-tight housing. One or more of the sample holders may include a flow cell. For example, one or more of the flow cells may be a quartz spectrophotometry flow cell. In use, the optical system may be configured to guide light to be incident upon the sample within one or more of the sample holders.

[0019] The optical system may include one or more optical system elements. The one or more optical system elements may include one or more filters or irises or light blockers.

[0020] The optical system may include one or more excitation filters. One or more of the excitations filters may be disposed at least partially within the interior of the fluid-tight housing. One or more of the excitation filters may be configured to filter light that is incident upon it. One or more of the excitation filters may be configured to filter collimated or uncollimated light before or after it interacts with the or a sample held by one or more of the sample holders.

[0021] The optical system may include one or more emission filters. One or more of the emission filters may be disposed at least partially within the interior of the fluid-tight housing. One or more of the emission filters may be configured to filter light that is incident upon it. One or more of the emission filters may be configured to filter light before or after it has interacted with the or a sample held by one or more of the sample holders.The optical system may include one or more detectors. One or more of the detectors may be disposed at least partially within the interior of the fluid-tight housing. One or more of the detectors may include a photodetector and / or may be configured to detect, directly or indirectly, light or a property thereof. In implementations, one or more of the detectors may include a solid-state detector. In implementations, one or more of the detectors may be configured to detect light after light has interacted with the or a sample held in one or more of the sample holders.

[0022] At least a portion of the interior may include an optical path cavity. The optical path cavity may constitute at least a portion of the interior. The optical path cavity may be shaped and dimensioned to define at least partially an optical pathway through the optical system or a part thereof, e.g. an optical system unit according to the present disclosure.

[0023] One or more, for example all, of the elements of the optical system disposed at least partially within the interior of the fluid-tight housing may be couplable, e.g. releasably couplable, to the interior of the fluid-tight housing.

[0024] One or more, for example all, of the elements of the optical system disposed within the interior of the fluid-tight housing may be connected to and / or disposed at least partially within a mounting plate. The interior of the fluid-tight housing may comprise one or more mounting points for mounting one or more elements of the optical system thereon. In implementations, one or more of the mounting points may be configured to allow the mounting plate to be coupled thereto, e.g. releasably coupled thereto. In implementations, one or more of the mounting points may include a slot for receiving a mounting plate.

[0025] One or more optical windows may be disposed in a wall of the fluid-tight housing. One or more of the optical windows may be configured to constitute, in use, an optical entry window and / or an optical exit window.

[0026] A first optical window may be disposed in a first wall of the fluid-tight housing and a second optical window may be disposed in the first wall or a second wall of the fluid-tight housing. After being reflected by one or more of the reflectors, light that entersthe interior of the fluid-tight housing via the first optical window may leave the interior of the fluid-tight housing via the second optical window and / or vice versa.

[0027] The optical system may be configured such that, in use, light entering the interior of the fluid-tight housing via the first optical window may leave the fluid-tight housing via the second optical window as collimated light and / or, in use, light entering the interior of the fluid-tight housing via the second optical window may leave the fluid-tight housing via the first optical window as focused light.

[0028] The optical system may be configured to magnify an image of an object. The object may include the or a sample held in the or a sample holder.

[0029] The optically transparent medium may be inert. The optically transparent medium may include a resin, a gel and / or a fluid, e.g. a liquid. The optically transparent medium may include an oil, e.g. a silicone oil. The optically transparent medium may be substantially incompressible.

[0030] The optically transparent medium may be transparent for select wavelengths of light.

[0031] In implementations, there may be no lens or lenses disposed at least partially within the interior. The optical system may not include any lenses.

[0032] A second aspect provides an optical system comprising:

[0033] one or more optical system units, one or more of the optical system units comprising:

[0034] a fluid-tight housing having an interior that is configured, in use, to be filled at least partially with an optically transparent medium;

[0035] at least one reflector disposed at least in part within the interior of the fluid-tight housing;

[0036] at least one optical window disposed in a wall of the fluid-tight housing; and

[0037] a pressure compensator connected to the fluid-tight housing and configured to minimise a pressure differential between the interior of the fluid-tight housing and an exterior of the fluid-tight housing;wherein at least a portion of one or more of the reflectors is / are arranged such that light that enters the interior of the fluid-tight housing via one of the optical windows is incident upon one or more of the reflectors before leaving the interior of the fluid-tight housing via one of the optical windows and / or vice versa.

[0038] An optical system may include a plurality of optical system units. One or more of the optical system units may be an optical system unit according to the present disclosure. Two of more of the optical system units may be arranged in optical series such that light passes sequentially through the optical system units arranged in the optical series.

[0039] A modular or composite optical system may include a plurality of optical system units. One or more of the optical system units may include an optical system unit according to the present disclosure.

[0040] One or more of the reflectors may be operable to produce collimated light from uncollimated light and / or vice versa. One or more of the reflectors may be operable to produce focused light from collimated light and / or vice versa. At least one, for example all, of the reflectors in the optical system unit(s) may include a mirror. One or more, e.g. all, of the reflectors may include a parabolic mirror and / or at least one of the reflectors in the optical system units may include a spherical mirror. One or more, e.g. all, of the parabolic mirrors may be an off-axis parabolic mirror. One or more, e.g. all, of the reflectors may include a retroreflector.

[0041] The optical system may not need a pressure-tight fluid-tight housing to function in an environment where there is a pressure differential between an interior and exterior of the fluid-tight housing(s).

[0042] The optical system may be able to collimate and / or focus light regardless of the refractive index of the optically transparent medium within the interior of the fluid-tight housing. The optical system units may be varied in order to adjust the function of the optical system.

[0043] At least one of the optical system units may be configured such that uncollimated light entering the interior of the fluid-tight housing leaves the fluid-tight housing as collimated light. At least one of the optical system units may be configured such thatcollimated light entering the interior of the fluid-tight housing leaves the fluid-tight housing as focused light.

[0044] At least one of the optical system units may be configured such that, in use, light entering the interior of the fluid-tight housing via one of the optical windows may leave the fluid-tight housing via the same one of and / or another one of the optical windows as collimated light and / or, in use, light entering the interior of the fluid-tight housing via one of the optical windows may leave the fluid-tight housing via the same one of and / or another one of the optical windows as focused light.

[0045] One or more of the optical system units may include a fill port configured to allow a material, e.g. the optically transparent medium or one or more ingredients or precursors thereof, to be introduced into and / or drained from the interior of the fluid-tight housing. The fill port may be disposed at least partially within a wall of the fluid-tight housing.

[0046] One or more of the pressure compensators may be disposed at least partially within a wall of the fluid-tight housing. One or more of the pressure compensators may include a syringe or a piston in fluid communication with the interior. One or more of the pressure compensators may include an elastic zone configured to deform, in use, thereby increasing or reducing a volume including the interior, to minimise the pressure differential between the interior and the environment exterior of the fluid-tight housing.

[0047] The fluid-tight housing of one or more of the optical system units may comprise, or consist essentially of, a polymeric material such as a plastic.

[0048] The optical system may include at least one light source. One or more of the light sources may be disposed at least partially within the interior of one or more of the optical system units. One or more of the light sources may be configured to emit, in use, uncollimated light. One or more of the light sources may include a light emitting diode (LED) or a laser. In use, light, e.g. uncollimated light, emitted by one or more of the light sources may be incident upon one or more of the reflectors, e.g. as collimated light.In implementations, one or more of the light sources may be disposed exterior to the optical system unit(s) such that, in use, the light source(s) can emit light into the interior of one or more of the optical system units via one or more of the optical window.

[0049] The optical system may include a sample holder configured to hold, in use, a sample for optical analysis. One or more of the sample holders may be disposed at least partially within the interior of the fluid-tight housing of one or more of the optical system units. One or more of the sample holders may include a flow cell. For example, one or more of the sample holders may be a quartz spectrophotometry flow cell. In use, the optical system may be configured to guide light to be incident upon the or a sample within one or more of the sample holders.

[0050] One or more of the sample holders may be disposed exterior to the optical system unit(s), for example, such that, light exiting one of the optical system units via one of the optical windows, in use, may be incident upon the or a sample within one or more of the sample holders.

[0051] The optical system may include one or more optical system elements. One or more of the optical system elements may include a filter, an iris or a light-blocker. In implementations, one or more of the optical windows may include one or more optical system elements. In implementations, one or more of the optical system elements may be disposed exterior to the optical system units. In implementations, one or more of the optical system elements may be disposed between optical system units to act on light leaving a first one of the optical system units before the light enters another one of the optical system units arranged in optical series with the first one of the optical system units. In implementations one or more of the optical system elements may be disposed exterior of a given one of the optical system units and configured to act on light leaving the given one of the optical system units before light re-enters the given one of the optical system units.

[0052] The optical system may include one or more excitation filters. One or more of the excitation filters may be disposed at least partially within the interior of the fluid-tight housing of one or more of the optical system units. One or more of the excitation filters may be configured to filter light that is incident upon it. One or more of the excitationfilters may be configured to filter collimated or uncollimated light before or after it interacts with the or a sample held by one or more of the sample holders.

[0053] One or more of the excitation filters may be disposed between two of the optical system units such that, in use, light emerging from one of the optical system units interacts with the excitation filters before entering another one of the other optical system units.

[0054] The optical system may include one or more emission filters. One or more of the emission filters may be disposed at least partially within the interior of the fluid-tight housing of one or more of the optical system units. One or more of the emission filters may be configured to filter light that is incident upon it. One or more of the emission filters may be configured to filter light after or before it interacts with the or a sample held by one or more of the sample holders.

[0055] For example, one or more of the emission filters may be disposed between two of the optical system units such that, in use, light emerging from one of the optical system units interacts with the emission filter(s) before entering another one of the optical system units.

[0056] In implementations, the optical system may include one or more optical system elements, e.g. filters such as excitation filters and / or emission filters, configured to act on light prior to the light interacting with the or a sample held in one or more of the sample holders.

[0057] The optical system may include one or more detectors. One or more of the detectors may be disposed at least partially within the interior of the fluid-tight housing of one or more of the optical system units. One or more of the detectors may include a photodetector and / or may be configured to detect, directly or indirectly, light or a property thereof. One or more of the detectors may include a solid-state detector.

[0058] One or more of the detectors may be disposed exterior to the optical system unit(s) such that, in use, light emerging from one or more of the optical system units or a property thereof may be detected, directly or indirectly, by the detector.Th optical system may include one or more optical system elements, e.g. filters such as excitation filters and / or emission filters, configured to act on light prior to the light reaching one or more of the detectors.

[0059] At least a portion of the interior of one or more of the optical system units may include an optical path cavity. One or more of the optical path cavities may constitute at least a portion of the interior. The optical path cavity may be shaped and dimensioned to define at least partially an optical pathway through the optical system or a part thereof, e.g. an optical system unit according to the present disclosure.

[0060] One or more, for example all, of the elements of the optical system disposed at least partially within the interior of the fluid-tight housing of one or more of the optical system units may be couplable, e.g. releasably couplable, to the interior of the fluid-tight housing.

[0061] One or more, for example all, of the elements of the optical system disposed within the interior of the fluid-tight housing of one or more of the optical system units may be connected to and / or disposed at least partially within a mounting plate. The interior of the fluid-tight housing may comprise one or more mounting points for mounting one or more elements of the optical system thereon. In implementations, one or more of the mounting points may be configured to allow the mounting plate to be coupled thereto, e.g. releasably coupled thereto. In implementations, one or more of the mounting points may include a slot for receiving a mounting plate.

[0062] One or more optical windows may be disposed in a wall or walls of the fluid-tight housing of one or more of the optical system units. One or more of the optical windows may be configured to constitute, in use, an optical entry window and / or an optical exit window.

[0063] A first optical window may be disposed in a first wall of the fluid-tight housing and a second optical window may be disposed in the first wall or a second wall of the fluid-tight housing. After being reflected by one or more of the reflectors, light that enters the interior of the fluid-tight housing via the first optical window may leave the interior of the fluid-tight housing via the second optical window and / or vice versa.The optical system may be configured such that, in use, light entering the interior of the fluid-tight housing via the first optical window may leave the fluid-tight housing via the second optical window as collimated light and / or, in use, light entering the interior of the fluid-tight housing via the second optical window may leave the fluid-tight housing via the first optical window as focused light.

[0064] The optical system may be configured to magnify an image of an object. The object may include the or a sample held in the or a sample holder.

[0065] The optically transparent medium may be inert. The optically transparent medium may include a resin, a gel and / or a fluid, e.g. a liquid. The optically transparent medium may include an oil, e.g. a silicone oil. The optically transparent medium may be substantially incompressible.

[0066] The optically transparent medium may be transparent for select wavelengths of light.

[0067] In implementations, there may be no lens or lenses disposed at least partially within the interior. The optical system may not include any lenses.

[0068] An optical system according to the present disclosure may constitute a submergible optical system. Accordingly, the optical system may be deployable at depth within a body of water.

[0069] The or a sample held within the sample holder(s) may be any suitable sample for optical analysis. The sample(s) may have been collected and / or prepared for analysis and / or delivered to the sample holder(s) by any suitable means.

[0070] For instance, one or more of the samples may include a fluid and one or more species of interest contained in the fluid. The fluid may include water, e.g. sea water or fresh water.

[0071] An optical system according to the present disclosure may be implemented, for example, as a fluorometer.Such a fluorometer may be used with any fluorescence-emitting assay including but not limited to the fluorometric detection of molecules, including nucleic acids (DNA and RNA using amplification and detection technologies such as LAMP, RPA, and qPCR) and / or toxins and / or pollutants.

[0072] Fieldwork in marine and freshwater environments in cases where humans are impacted or environmental change is detrimental can be time-sensitive, requiring a response or change to prevent harm. In these cases, near real-time analyses can deliver real savings in the form of human or environmental health or financial impact. Optical systems according to the present disclosure may be employed to create an improved monitoring scenario, which may, for example, employ in situ analytics without human intervention in remote underwater environments and / or may be relatively cheap to implement.

[0073] It is envisaged that an optical system according to the present disclosure may be used to detect deep sea hazards such as microbial responses to methane or oil leaks at the seafloor or deoxygenation.

[0074] Any optical system according to the present disclosure may be utilised as a standalone system or device and / or integrated or incorporated into a wider system.

[0075] The optical system may include a data logger arranged to log data from sample analysis carried out using the optical system. The optical system may include a means for processing and / or analysing data logged in the data logger and / or a means for transferring data, in a raw form or a processed form, from the optical system to a remote location for further processing and / or analysis. The remote location may be on a research vessel and / or at a location on land.

[0076] A wider system may include one or more optical systems according to the present disclosure, e.g. a plurality of optical systems according to the present disclosure, deployed or deployable at one or more locations or regions of interest within a body of water.

[0077] Any suitable platform may be utilised in the deployment of, in particular the underwater deployment of, of an optical system according to the present disclosure. Examples ofsuitable platforms may include data buoys, vessels, autonomous underwater vehicles (AUVs).

[0078] The teaching of the present disclosure may be used to form many different optical systems, including relatively complex optical systems including illuminators, microscopes, imaging systems, spectrophotometers, interferometers, cytometers, or Raman spectroscopy systems.

[0079] The teaching of the present disclosure may be used to produce an optical system suitable for the detection of ammonia and / or monitoring of ammonia levels in rivers.

[0080] An aspect provides an optical system unit comprising:

[0081] a fluid-tight housing having an interior that is configured, in use, to be filled at least partially with an optically transparent medium;

[0082] at least one reflector disposed at least in part within the interior of the fluid-tight housing;

[0083] at least one optical window disposed in a wall of the fluid-tight housing; and

[0084] a pressure compensator connected to the fluid-tight housing and configured to minimise a pressure differential between the interior of the fluid-tight housing and an exterior of the fluid-tight housing;

[0085] wherein at least a portion of one or more of the reflectors is / are arranged such that light that enters the interior of the fluid-tight housing via one of the optical windows is incident upon one or more of the reflectors before leaving the interior of the fluid-tight housing via one of the optical windows and / or vice versa.

[0086] An aspect provides use of an optical system according to the present disclosure or an optical system including an optical system unit according to the present disclosure in optical analysis of one or more samples.

[0087] The optical analysis may be carried out at depth, e.g. within a body of a fluid such as water.

[0088] In monitoring or surveying a location or region of interest within the body of fluid such as water, the optical analysis may be repeated on one or more occasions, e.g. at regularor irregular intervals during a predetermined time period. The predetermined time period may be indefinite and / or have no set end point, e.g. in the case of ongoing environmental monitoring.

[0089] The optical analysis may be repeated on one or more occasions at one or more different locations or in one or more different regions within the body of fluid such as water.

[0090] The body of water may include a freshwater body of water or a saltwater body of water.

[0091] The person skilled in the art will appreciate that except where mutually exclusive, a feature described in relation to any one of the above aspects may be applied mutatis mutandis to any other aspect. Furthermore, except where mutually exclusive any feature described herein may be applied to any aspect and / or combined with any other feature described herein.

[0092] Examples will now be described with reference to the accompanying drawings in which:

[0093] Figure 1 shows an optical system unit;

[0094] Figure 2 shows a composite optical system;

[0095] Figure 3 shows an optical system;

[0096] Figure 4 shows an example of an optical system for image magnification;

[0097] Figure 5 shows an example of an optical system for sample analysis;

[0098] Figure 6 shows a fluid-tight housing for an optical system;

[0099] Figure 7 shows the fluid-tight housing of Figure 6 with components installed; and Figure 8 shows the fluid-tight housing of Figure 7 with a lid.

[0100] Figure 1 shows an example of an optical system unit 100.

[0101] A fluid-tight housing 101 has an interior 120. The interior 120 is defined in part by a first end wall 109, a second end wall 110 opposite the first end wall 109, a first side wall 111 and a second side wall 112 opposite the first side wall 111. The first end wall 109 connects a first end of the first side wall 111 to a first end of the second side wall 112. The second end wall 110 connects a second end of the first side wall 111 to a second end of the second side wall 112. A fill port 102 configured to allow a fluid to be introduced into and / or drained from the interior 120 fluid-tight housing 101 is disposedwithin the second side wall 112 of the fluid-tight housing 101. When the fill port 102 is not in use the fill port 102 may be closed with a fluid-tight seal. In use, the interior 120 of the fluid-tight housing 101 is filled at least partially with an inert, optically transparent medium. The interior 120 may be filled substantially entirely with the inert, optically transparent medium. The inert, optically transparent medium may include a resin, a gel or a fluid, e.g. a liquid. The inert, optically transparent medium may be substantially incompressible. For example, the inert, optically transparent medium may include, or consist essentially of, an oil, e.g. a silicone oil.

[0102] A pressure compensator 103 is disposed within the second side wall 112 of the fluid-tight housing 101. The pressure compensator 103 includes an elastic zone fluid-tight housing 101 configured to deform, in use, thereby increasing or reducing the volume of the interior 120, in order to minimise a pressure differential between the interior 120 and the environment exterior of the fluid-tight housing 101. Any suitable pressure compensator may be employed and many possible pressure compensators will now occur to the skilled person.

[0103] A reflector in the form of a parabolic mirror 104 is disposed in the interior. The parabolic mirror 104 is provided on a mount 113 connected to and extending from the first end wall 109.

[0104] A first optical window 105 is formed in the first side wall 111 of the fluid-tight housing 101. The first optical window 105 and the parabolic mirror 104 are arranged such that the first optical window 105 coincides with the focal point of the parabolic mirror 104. The first optical window 105 is optically transparent and is configured to allow light to enter / exit the interior 120 of the fluid-tight housing 101.

[0105] A second optical window 106 is formed in the second end wall 110 of the fluid-tight housing 101. The second optical window 106 and the parabolic mirror 104 are arranged such that at least a portion of reflected light 108 from the parabolic mirror 104 passes through the second optical window 106. The second optical window 106 is optically transparent and is configured to allow light to enter and / or exit the interior 120 of the fluid-tight housing 101.In a first use, light may enter the interior 120 via the first optical window 105. This light enters the interior 120 as uncollimated light 107 and is incident upon the parabolic mirror 104. As the first optical window 105 is disposed at the focal point of the parabolic mirror 104, the uncollimated light 107 reflects from the parabolic mirror 104 such that it emerges as collimated light 108. The parabolic mirror 104 directs the collimated light 108 towards the second optical window 106, whereupon it exits the interior 120 of the fluid-tight housing 101 as collimated light. In the first use, the first optical window 105 may be considered an optical entry window and the second optical window 106 may be considered an optical exit window.

[0106] In a second use, light may enter the interior 120 via the second optical window 106. This light will be incident upon the parabolic mirror 104 and be reflected. When this light is collimated light 108, the parabolic mirror 104 will reflect it such that it is focused on the focal point of the parabolic mirror 104. The parabolic mirror 104 will therefore focus the light onto the first optical window 105, whereupon it will exit the interior 120 of the fluid-tight housing 101.

[0107] By utilising reflection, operation of the optical system unit 100 is such that it is independent of the refractive index of the medium that fills the interior 120 of the fluid-tight housing 101. The optical system unit 100 may thus exhibits the same behaviour, e.g. producing collimated light from uncollimated light or producing focused light from collimated light, independent of the pressure of the environment in which the optical system unit 100 is placed.

[0108] This may be particularly useful, as it may allow the optical system unit 100 to have the same operation independent of the pressure of the environment surrounding the fluid-tight housing 101 without the need for a pressure-tight fluid-tight housing. The pressure compensator 103 may act to minimise the pressure differential between the interior 120 and exterior of the fluid-tight housing 101, thereby eliminating the need for an expensive and difficult-to-manufacture pressure-tight fluid-tight housing. While this also means that the pressure and thus refractive index of the medium filling the interior 102 changes, the use of a reflector, e.g. a parabolic mirror, rather than, for example, a lens, to produce collimated or focused light allows the optical system unit 100 to have the same behaviour independent of the refractive index of the medium.Multiple optical system units similar to the optical system unit 100 may be combined to form more complex systems. In this application, the term composite optical system may be used to refer to an optical system formed from a plurality of optical system units including one or more optical system units according to the present disclosure. For example, bright or dark-field illuminators, microscopes, fluorescence detectors, or imaging systems may be constructed. The optical system units may be arranged such that light exiting the interior 102 via an optical exit window of one optical system unit enters the interior of another fluid-tight housing of another optical system unit via said fluid-tight housing’s optical entry window.

[0109] In implementations, one or more optical elements such as filters, irises, beamsplitters, dispersive optical elements (e.g. prisms, diffraction gratings, etc) and / or light-stoppers may be disposed between optical system units.

[0110] Figure 2 shows a composite optical system 2000 comprising a first optical system unit 200 and a second optical system unit 220.

[0111] The first optical system unit 200 includes a first fluid-tight housing 201 with a first interior 235. The first interior 235 is defined in part by a first end wall 209, a second end wall 210 opposite the first end wall 209, a first side wall 211 and a second side wall 212 opposite the first side wall 211. The first end wall 209 connects a first end of the first side wall 211 to a first end of the second side wall 212. The second end wall 210 connects a second end of the first side wall 211 to a second end of the second side wall 212.

[0112] A fill port 202 configured to allow a fluid to be introduced into and / or drained from the first interior 235 is disposed within the second side wall 212 of the first fluid-tight housing 201. When the fill port 202 is not in use the fill port 202 may be closed with a fluid-tight seal. In use, the first interior 235 is filled at least partially with an inert, optically transparent medium. The first interior 235 may be filled substantially entirely with the inert, optically transparent medium. The inert, optically transparent medium may include a resin, a gel and / or a fluid, e.g. a liquid. The inert, optically transparent medium may be substantially incompressible. For example, the inert, optically transparent medium may include, or consist essentially of, an oil, e.g. a silicone oil.A pressure compensator 203 is disposed within the second side wall 212 of the first fluid-tight housing 201. The pressure compensator 203 includes an elastic zone configured to deform, in use, thereby increasing or reducing the volume of the first interior 235, in order to minimise a pressure differential between the first interior 235 and the environment exterior of the first fluid-tight housing 201. Any suitable pressure compensator may be employed and many possible pressure compensators may occur to the person skilled in the art.

[0113] A first reflector in the form of a first parabolic mirror 204 is disposed in the first interior 235. The first parabolic mirror 204 is provided on a first mount 213 connected to and extending from the first end wall 209.

[0114] A first optical window 205 is formed in the first side wall 211. The first optical window 205 and the first parabolic mirror 204 are arranged such that the first optical window 205 coincides with the focal point of the first parabolic mirror 204. The first optical window 205 is optically transparent and is configured to allow light to enter and / or exit the first interior 235.

[0115] A second optical window 206 is formed in the second end wall 210 of the first fluid-tight housing 201. The second optical window 206 and the first parabolic mirror 204 are arranged such that at least a portion of collimated light 208 reflected from the first parabolic mirror 204 passes through the second optical window 206. The second optical window 206 is optically transparent and is configured to allow light to enter and / or exit the first interior 235 of the first fluid-tight housing 201.

[0116] The second optical system unit 220 includes a second fluid-tight housing 221 with a second interior 236. The second interior 236 is defined in part by a first end wall 229, a second end wall 230 opposite the first end wall 229, a first side wall 231 and a second side wall 232 opposite the first side wall 231. The first end wall 229 connects a first end of the first side wall 231 to a first end of the second side wall 232. The second end wall 230 connects a second end of the first side wall 231 to a second end of the second side wall 232.

[0117] A fill port 222 configured to allow a fluid to be introduced into and / or drained from the second interior 236 is disposed within the second side wall 232 of the second fluid-tighthousing 221. When the fill port 222 is not in use the fill port 222 may be closed with a fluid-tight seal. In use, the second interior 236 is filled at least partially with an inert, optically transparent medium. The second interior 236 may be filled substantially entirely with the inert, optically transparent medium. The inert, optically transparent medium may include a resin, a gel and / or a fluid, e.g. a liquid. The inert, optically transparent medium may be substantially incompressible. For example, the inert, optically transparent medium may include, or consist essentially of, an oil, e.g. a silicone oil.

[0118] A pressure compensator 223 is disposed within the second side wall 232 of the second fluid-tight housing 221. The pressure compensator 223 includes an elastic zone configured to deform, in use, thereby increasing or reducing the volume of the second interior 236, in order to minimise a pressure differential between the second interior 236 and the environment exterior of the second fluid-tight housing 221. Any suitable pressure compensator may be employed and many possible pressure compensators may occur to the person skilled in the art.

[0119] A second reflector in the form of a second parabolic mirror 224 is disposed in the second interior 236. The second parabolic mirror 224 is provided on a second mount 233 connected to and extending from the first end wall 229.

[0120] A first optical window 225 is formed in the first side wall 231. The first optical window 225 and the second parabolic mirror 224 are arranged such that the first optical window 225 coincides with the focal point of the second parabolic mirror 224. The first optical window 225 is optically transparent and is configured to allow light to enter and / or exit the second interior 236.

[0121] A second optical window 226 is formed in the second end wall 230 of the first fluid-tight housing 221. The second optical window 226 and the second parabolic mirror 224 are arranged such that at least a portion of filtered collimated light 228 passes through the second optical window 226 and is incident on the second parabolic mirror 224. The second optical window 226 is optically transparent and is configured to allow light to enter and / or exit the second interior 236 of the second fluid-tight housing 221.An optical element in the form of a filter 234 is disposed between the second optical window 206 of the first fluid-tight housing 201 and the second optical window 226 of the second fluid-tight housing 221. The filter 234 is configured to filter collimated light 208 passing through the second optical window 206 of the first fluid-tight housing 201 to produce filtered collimated light 228. Filtered collimated light 228 enters the second fluid-tight housing 221 via the second optical window 226 and is then incident upon the second parabolic mirror 224. The second parabolic mirror 224 reflects the filtered collimated light 228 incident thereon to focus reflected filtered collimated light 227 at the first optical window 225 of the second optical system unit 220.

[0122] A device for holding a sample for optical analysis such as a flow cell 237 is disposed outside the second interior 236 adjacent the first optical window 225. The flow cell 237 is configured such that light exiting the second optical system unit 220 via the first optical window 225 is incident on the sample within the flow cell 237. Optical analysis of the sample may include an analysis of one or more interactions of this light with the sample within the flow cell 237.

[0123] In implementations, the filter 234 may be replaced with or employed in combination with another optical element, e.g. an iris or a light stopper.

[0124] The composite optical system 2000 may allow light to be focused on to a sample in a flow cell or the like for optical analysis of the sample to be carried out in a way that is independent of the pressure of the environment surrounding the composite optical system 2000 without requiring the use of a pressure-tight fluid-tight housing.

[0125] Figure 3 shows an optical system 300.

[0126] The optical system 300 includes a fluid-tight housing 301 with an interior 320. The interior 320 is defined in part by a first end wall 309, a second end wall 310 opposite the first end wall 309, a first side wall 311 and a second side wall 312 opposite the first side wall 311. The first end wall 309 connects a first end of the first side wall 311 to a first end of the second side wall 312. The second end wall 310 connects a second end of the first side wall 311 to a second end of the second side wall 312.A fill port 302 configured to allow a fluid to be introduced into and / or drained from the interior 320 is disposed within the second side wall 312 of the fluid-tight housing 301. When the fill port 302 is not in use the fill port 302 may be closed with a fluid-tight seal. In use, the interior 320 of the fluid-tight housing 301 is filled at least partially with an inert, optically transparent medium. The interior 320 may be filled substantially entirely with the inert, optically transparent medium. The inert, optically transparent medium may include a resin, a gel and / or a fluid, e.g. a liquid. The inert, optically transparent medium may be substantially incompressible. For example, the inert, optically transparent medium may include, or consist essentially of, an oil, e.g. a silicone oil.

[0127] A pressure compensator 303 is disposed within the second side wall 312 of the fluid-tight housing 301. The pressure compensator 303 includes an elastic zone configured to deform, in use, thereby increasing or decreasing the volume of the interior 320, in order to minimise a pressure differential between the interior 320 and the environment exterior of the fluid-tight housing 301. Any suitable pressure compensator may be employed and many suitable pressure compensators may occur to the skilled person.

[0128] A first reflector in the form of a first parabolic mirror 304 is disposed in the interior 320. The first parabolic mirror 304 is provided on a first mount 313 connected to and extending from the first end wall 309.

[0129] A first optical window 305 is disposed in the first side wall 311 of the fluid-tight housing 301. The first optical window 305 and the first parabolic mirror 304 are arranged such that the first optical window 305 coincides with the focal point of the first parabolic mirror 304. The first optical window 305 is optically transparent and is configured to allow light to enter and / or exit the interior 320 of the fluid-tight housing 301.

[0130] A second reflector in the form of a second parabolic mirror 316 is disposed in the interior 320. The second parabolic mirror 316 is provided on a second mount 318 connected to and extending from the second end wall 310.

[0131] A second optical window 306 is disposed in the second side wall 312 of the fluid-tight housing 301. The second optical window 306 and the second parabolic mirror 316 arearranged such that the second optical window 306 coincides with the focal point of the second parabolic mirror 316. The second optical window 306 is optically transparent and is configured to allow light to enter and / or exit the interior 320 of the fluid-tight housing 301.

[0132] An optical element 314 is disposed in the interior 320. The optical element 314 is configured to act on light travelling from the first parabolic mirror 304 to the second parabolic mirror 316 or vice versa. The optical element 314 may be any optical element. For example, the optical element 314 may include an iris, a filter or a light stopper.

[0133] The optical element 314 is supported by a third mount 321 connected to and extending from the second side wall 312.

[0134] A device for holding a sample for optical analysis such as a flow cell 319 is disposed outside the interior 320 adjacent the second optical window 306. The flow cell 319 is configured such that light exiting the fluid-tight housing 301 via the second optical window 306 is incident on the sample within the flow cell 319. Optical analysis of the sample may include an analysis of one or more interactions of this light with the sample within the flow cell 319.

[0135] In use, light enters the interior 320 of the fluid-tight housing 301 via the first optical window 305 and is incident upon the first parabolic mirror 304 as uncollimated light 307. After reflecting from the first parabolic mirror 304 collimated light 308 travels to the optical element 314, which acts on the collimated light 308 to produce treated collimated light 315. Treated collimated light 315 may include filtered collimated light in implementations in which the optical element 314 includes a filter. Treated collimated light 315 is then reflected by the second parabolic mirror 316. The light 317 reflected from the second parabolic mirror 316 is focused at the second optical window 306 and is then incident upon the sample in the flow cell 319.

[0136] Figure 4 shows another example of an optical system 400. The optical system 400 may be understood to be an image magnification system.

[0137] The optical system 400 constitutes a composite optical system and includes a first optical system unit 410 and a second optical system unit 430.The first optical system unit 410 includes a first fluid-tight housing 411 with a first interior 418. The first interior 418 is defined in part by a first end wall 420, a second end wall 421 opposite the first end wall 420, a first side wall 422 and a second side wall 423 opposite the first side wall 422. The first end wall 420 connects a first end of the first side wall 422 to a first end of the second side wall 423. The second end wall 421 connects a second end of the first side wall 422 to a second end of the second side wall 423.

[0138] A first fill port 412 configured to allow a fluid to be introduced into and / or drained from the first interior 418 is disposed within the second end wall 421 of the first fluid-tight housing 411. When the first fill port 412 is not in use the first fill port 412 may be closed with a fluid-tight seal. In use, the first interior 418 is filled at least partially with an inert, optically transparent medium. The first interior 418 may be filled substantially entirely with the inert, optically transparent medium. The inert, optically transparent medium may include a resin, a gel and / or a fluid, e.g. a liquid. The inert, optically transparent medium may include, or consist essentially of, an oil, e.g. a silicone oil.

[0139] A first pressure compensator 413 is disposed within the second end wall 421 of the first fluid-tight housing 411. The first pressure compensator 413 may include an elastic zone configured to deform, in use, thereby increasing or decreasing the volume of the first interior 418, in order to minimise a pressure differential between the first interior 418 and the environment exterior of the first fluid-tight housing 411. Any suitable pressure compensator may be employed and many possible pressure compensator may occur to the person skilled in the art.

[0140] A first reflector in the form of a first parabolic mirror 416 is disposed in the first interior 418. The first parabolic mirror 416 is provided on a first mount 419 connected to and extending from the first side wall 422.

[0141] A first optical window 414 is formed in the first end wall 420. The first optical window 414 and the first parabolic mirror 416 are arranged such that the first optical window 414 coincides with the focal point of the first parabolic mirror 416. The first optical window 414 is optically transparent and is configured to allow light to enter and / or exit the first interior 418.A second optical window 415 is formed in the second side wall 423 of the first fluid-tight housing 411. The second optical window 415 and the first parabolic mirror 416 are arranged such that at least a portion of collimated light 444 reflected from the first parabolic mirror 416 passes through the second optical window 415. The second optical window 415 is optically transparent and is configured to allow light to enter and / or exit the first interior 418 of the first housing 411.

[0142] The second optical system unit 430 includes a second fluid-tight housing 431 with a second interior 437. The second interior 437 is defined in part by a first end wall 438, a second end wall opposite the first end wall 438, a first side wall 439 and a second side wall 440 opposite the first side wall 439. The second end wall is formed by a portion of the second side wall 423 of the first fluid-tight housing 411 including the second optical window 415.

[0143] The first end wall 438 connects a first end of the first side wall 439 to a first end of the second side wall 440. A second end of the first side wall 439 is connected to the second side wall 423 of the first fluid-tight housing 411. A second end of the second side wall 440 is connected to the second side wall 423 of the first fluid-tight housing 411.

[0144] A second fill port 432 configured to allow a fluid to be introduced into and / or drained from the second interior 437 is disposed within the first side wall 439 of the second fluid-tight housing 411. When the second fill port 432 is not in use the second fill port 432 may be closed with a fluid-tight seal. In use, the second interior 437 is filled at least partially with an inert, optically transparent medium. The second interior 437 may be filled substantially entirely with the inert, optically transparent medium. The inert, optically transparent medium may include a resin, a gel and / or a fluid, e.g. a liquid. The inert, optically transparent medium may be substantially incompressible. For example, the inert, optically transparent medium may include, or consist essentially of, an oil, e.g. a silicone oil.

[0145] A second pressure compensator 433 is disposed within the first side wall 439 of the second fluid-tight housing 431. The second pressure compensator 433 includes an elastic zone configured to deform, in use, thereby increasing or reducing the volume of the second interior 437, in order to minimise a pressure differential between the secondinterior 437 and the environment exterior of the second fluid-tight housing 431. Any suitable pressure compensator may be employed and many possible pressure compensators may occur to the person skilled in the art.

[0146] A second reflector in the form of a second parabolic mirror 436 is disposed in the second interior 437. The second parabolic mirror 436 is provided on a second mount 441 connected to and extending from the first end wall 439.

[0147] A third optical window 434 is formed in the second side wall 440 of the second fluid-tight housing 431. The third optical window 434 and the second parabolic mirror 436 are arranged such that the third optical window 434 coincides with the focal point of the second parabolic mirror 436. The third optical window 434 is optically transparent and is configured to allow light to enter and / or exit the second interior 437.

[0148] A device for holding a sample for optical analysis such as a flow cell 417 is disposed outside the first interior 418 adjacent the first optical window 414. The flow cell 417 is arranged so that light, e.g. scattered light, reflected light or fluorescence, from the sample is able to pass into the first interior 418 via the first optical window 414.

[0149] Sample-derived light 445 passes through the first optical window 414 and is incident upon the first parabolic mirror 416 and reflected therefrom as collimated light 444.

[0150] Collimated light 444 passes through the second optical window 415 and is incident on the second parabolic mirror 436. Reflected light 442 from the second parabolic mirror 436 is focused at the third optical window 434.

[0151] In implementations, the second optical window may include an optical element, e.g. an iris, a filter or a light-stopper.

[0152] Operation of the optical system 400 as an image magnification system will now be described.

[0153] The focal length of the first parabolic mirror 416 is longer than the focal length of the second parabolic mirror 436. The amount of magnification achieved can be varied by varying the focal lengths of the first parabolic mirror 416 and the second parabolicmirror 436 relative to each other. In some examples, the focal point of the second parabolic mirror 436 may extend beyond the exit optical window 434 such that the magnified image can be viewed from a point exterior to the second optical system unit 430.

[0154] Figure 5 shows an example of an optical system 500 for sample analysis.

[0155] A fluid-tight housing 501 has an interior 520. The interior is defined in part by a first side wall 521, a second side wall 522, a third side wall 523, a fourth side wall 524, a fifth side wall 525 and a sixth side wall 526. A first end of the first side wall 521 is connected to a second end of the sixth side wall 526. A second end of the first side wall 521 is connected to a first end of the second side wall 522. The second side wall 522 is perpendicular to the first side wall 521. A second end of the second side wall 522 is connected to a first end of the third side wall 523. An internal angle of approximately 225° is formed between the second side wall 522 and the third side wall 523. A second end of the third side wall 523 is connected to a first end of the fourth side wall 524. The fourth side wall 524 is perpendicular to the third side wall 523. A second end of the fourth side wall 524 is connected to a first end of the fifth side wall 525. The fifth side wall 525 is perpendicular to the fourth side wall 524. A second end of the fifth side wall 525 is connected to a first end of the sixth side wall 526. The sixth side wall 526 is perpendicular to the fifth side wall 525. An internal angle of approximately 135° is formed between the sixth side wall 526 and the first side wall 521.

[0156] A fill port 513 configured to allow a fluid to be introduced into and / or drained from the interior 520 of the fluid-tight housing 501 is disposed within the sixth side wall 526. When the fill port 513 is not in use the fill port 513 may be closed with a fluid-tight seal. In use, the interior 520 of the fluid-tight housing 501 is filled at least partially with an inert, optically transparent medium. The interior 520 may be filled substantially entirely with the inert, optically transparent medium. The inert, optically transparent medium may include a resin, a gel and / or a fluid, e.g. a liquid. The inert, optically transparent medium may be substantially incompressible. For example, the inert, optically transparent medium may include, or consist essentially of, an oil, e.g. a silicone oil.A pressure compensator 512 is disposed within the sixth side wall 526 of the fluid-tight housing 501. The pressure compensator 503 includes an elastic zone configured to deform, in use, thereby increasing or reducing the volume of the interior 520 in order to minimise a pressure differential between the interior 502 and the environment exterior of the fluid-tight housing 501. Any suitable pressure compensator may be employed and many possible pressure compensators may now occur to the skilled person.

[0157] A first optical window 502 is disposed in the second side wall 522. The first optical window 502 acts as an entry optical window. The first optical window 502 is optically transparent. Adjacent to the optical window 502, exterior to the fluid-tight housing 501, is a first excitation filter 503. Adjacent to the first excitation filter 503, exterior to the fluid-tight housing 501, is a light source 504. In use, the first excitation filter 503 is operable to filter light emitted by the light source 504 such that only filtered light 530 having a desired wavelength or range or set of wavelengths enters the interior 520 of the fluid-tight housing 501 via the first optical window 502. In some examples, the first excitation filter 503 may not be present.

[0158] A first reflector in the form of a first parabolic mirror 505 is disposed in the interior 520. The first parabolic mirror 505 is provided on a first mount 528 connected to and extending from the first side wall 521. The first optical window 502 and the first parabolic mirror 505 are arranged such that the first optical window 502 coincides with the focal point of the first parabolic mirror 505. Filtered light 530 that enters the interior 520 of the fluid-tight housing 501 via the entry optical window 502 is incident upon the first parabolic mirror 505 and reflected such that it becomes collimated light 531.

[0159] A second optical window 507 is disposed in the fourth side wall 524. The second optical window 507 is optically transparent at least in part. The second optical window 507 may be considered a sample optical window. Adjacent the second optical window 507, exterior to the fluid-tight housing 501, there is a device such as a flow cell 515 for holding a sample for optical analysis.

[0160] A second excitation filter 506 is disposed in the interior 520. The second excitation filter 506 is configured to act on collimated light 531 travelling from the first parabolic mirror 505 towards the second optical window 507. The second excitation filter 506converts collimated light 531 to filtered collimated light 532. The second excitation filter 506 may be operable to allow only particular wavelengths of light from the collimated light 531 to reach the second optical window 507. In some examples, the second excitation filter 506 may not be present.

[0161] Filtered collimated light 532 passes through the second optical window 507 and is incident upon a sample within the flow cell 515.

[0162] A second reflector in the form of a second parabolic mirror 508 is disposed within the interior 520 501 such that its focal point coincides with the second optical window 507. The second parabolic mirror 508 is provided on a second mount 529 connected to and extending from a partition wall 527. Sample-derived light 533 that is reflected from the sample in the flow cell 515 or emitted fluorescently from the sample in the flow cell 515 will be incident upon the second parabolic mirror 508. The sample-derived light 533 will then be reflected from the second parabolic mirror 508 and form collimated output light 534.

[0163] A third optical window 509 is formed within the fifth side wall 525 of the fluid-tight housing 501. The third optical window 509 is optically transparent. The third optical window 509 may be termed a detector window. Adjacent to the third optical window 509, exterior to the fluid-tight housing 501, is an emission filter 510. Adjacent to the emission filter 510, exterior to the fluid-tight housing 501, is a detector 511. The detector 511 may include a photomultiplier tube, a multi-pixel photon detector, a partial discharge detector, or any other suitable detector for detecting, directly or indirectly, light or a property thereof.

[0164] The collimated output light 534 that is reflected from the second parabolic mirror 508 exits the interior 520 of the fluid-tight housing 501 via the third optical window 509. The collimated output light then passes through the emission filter 510, whereupon, for example, wavelengths of light that corresponded to the excitation wavelengths may be filtered out, in order to transmit only fluorescent light from the sample. The light then passes onto the detector 511 and is detected.

[0165] In other examples, the collimated light that is reflected from the second parabolic mirror 508 may be incident upon a further parabolic mirror disposed such that the third opticalwindow 509 is coincident with the focal point of the further parabolic mirror. In such examples, light that is incident upon the emission filter 510, and subsequently the detector 511, may be focused light instead of collimated light.

[0166] The optical system 500 may be suitable, for example, for sample analysis using fluorometry. It is a self-contained system that functions independently of the refractive index of the inert, optically transparent medium filling the interior 520 of the fluid-tight housing 501 and thus may not require a pressure -tight fluid-tight housing.

[0167] The optical system 500 may be suitable for use with any fluorescence-emitting assay. For example, it may be used for fluorometric detection of molecules, including nucleic acids, toxins, and pollutants, particularly from within a fluid, e.g. liquid, sample. The optical system 500 may be suitable for use at depth.

[0168] Referring now to Figures 6, 7, and 8, an example of an optical system 800 is described.

[0169] Figure 8 shows the optical system 800 in an assembled form. Figure 7 shows a portion of a fluid-tight housing 600 of the optical system 800 with optical system components in place. Figure 6 shows a portion of the fluid-tight housing 600 of the optical system 800 without any optical system components in place.

[0170] An optical system recess 601 is formed in a cylindrical disc 605. The optical system recess 601 has a shape and dimensions selected for a desired optical system configuration and / or application. The illustrated example is simply an example of a possible optical system configuration. The optical system recess 601 may be formed in the cylindrical disc 605 by any suitable process. In implementations, the disc in which the optical system recess is formed may not be cylindrical.

[0171] In the illustrated example, the cylindrical disc 605 may have a diameter of approximately 11 cm.

[0172] The optical system recess 601 defines in part an interior of the fluid-tight housing 600. The optical system recess 601 is configured to define, in use, a path that light may travel through the optical system 800.The optical system recess 601 is configured to have various optical system components disposed therein, as required to provide a desired optical system. In the illustrated example, a first mounting slot 620a, a second mounting slot 620b, a third mounting slot 620c, a fourth mounting slot 620d, a fifth mounting slot 620e, a sixth mounting slot 620f and a seventh mounting slot 620g are provided at desired locations within the optical system recess 601. Each mounting slot 620a, 620b, 620c, 620d, 620e, 620f, 620g is defined in part by a first notch and a second notch formed in opposite side walls of the optical system recess 601. Each mounting slot 620a, 620b, 620c, 620d, 620e, 620f, 620g is configured to receive an optical system component and / or an optical system component mount therein.

[0173] An annular indentation 606 is formed in a top surface 602 of the cylindrical disc 605 and surrounds the optical system recess 601. The annular indentation 606 is configured to receive a sealing member, such as an O-ring, within it.

[0174] Three attachment holes 604 are also formed in the top surface 602.

[0175] The optical system recess 601 includes a pressure compensating cavity 603 and a filling cavity 605.

[0176] Figure 7 shows the fluid-tight housing 600 of Figure 6 with optical system components installed therein.

[0177] A light source 702 is provided in a first mounting plate 701a. The first mounting plate 701a is received in the first mounting slot 620a. With the first mounting plate 701a received in the first mounting slot 620a, the light source 702 is arranged to emit, in use, uncollimated light along a path defined by the optical system recess 601. The light source 702 may include an LED light source and / or may be configured to emit uncollimated light. In other examples, other light sources may be used.

[0178] A second mounting plate 701b is received in the second mounting slot 620b. A first reflector in the form of a first parabolic mirror 703 is connected to the second mounting plate 701b. The first parabolic mirror 703 is disposed in the optical system recess 601 such that uncollimated light emitted by the light source 702 is incident upon the first parabolic mirror 703. The light source 702 and the first parabolic mirror 703 arearranged such that the light source 702 is disposed at the focal point of the first parabolic mirror 703. In use, the uncollimated light emitted by the light source 702 is reflected by the first parabolic mirror 703 as collimated light.

[0179] A third mounting plate 701c is received in the third mounting slot 620c. An excitation filter 703 is provided in the third mounting plate 701c. The excitation filter 703 is arranged to act on the collimated light reflected from the first parabolic mirror 703.

[0180] A device for holding a sample for optical analysis such as a flow cell 705 is disposed within the optical system recess 601. The flow cell 705 is arranged such that filtered collimated light from the excitation filter 703 is incident, in use, on the sample within the flow cell. Sample-derived light may then exit the flow cell 705 from an opposite side of the flow cell 705. The sample-derived light may be reflected by the sample, scattered by the sample or may include fluorescence.

[0181] A fourth mounting plate 70 Id is received in the fourth mounting slot 620d. A second reflector in the form of a second parabolic mirror 706 is connected to the fourth mounting plate 701d. The second parabolic mirror 706 is arranged such that sample-derived light is incident thereon. The second parabolic mirror 706 is arranged such that the sample in the flow cell 705 is coincident with the focal point of the second parabolic mirror 706. The light reflected from the second parabolic mirror may be termed collimated sample-derived light.

[0182] A fifth mounting plate 70 le is received in the fifth mounting slot 620e. An emission filter 707 is provided in the fifth mounting plate 701e. The emission filter 707 is arranged to act on the collimated sample-derived light from the second parabolic mirror 706 to provide filtered collimated sample-derived light.

[0183] A sixth mounting plate 70 If is received in the sixth mounting slot 620f. A third reflector in the form of a third parabolic mirror 708 is connected to the sixth mounting plate 701f. The third parabolic mirror 708 is arranged such that filtered collimated sample-derived light is incident thereon. The third parabolic mirror 708 is arranged such a detector 709 is coincident with the focus of the third parabolic mirror 708. The detector 709 is arranged to detect focused filtered sample-derived light.A seventh mounting plate 701g is received in the seventh mounting slot 620g. The detector 709 is connected to the seventh mounting plate 701g. In an implementation, the detector 709 may include a solid-state detector. In other examples, the detector may include any other suitable detector.

[0184] The optical system 800 may be suitable for use as a fluorometer, for example.

[0185] Referring to Figure 8, a lid 801 is coupled to the cylindrical disc 605.

[0186] The lid 801 is configured to cover the entirety of the top surface 602. The lid 801 includes three holes 802. Each one of the holes 802 is arranged to line up with one of the three attachment holes 604. Any suitable fastener may be employed to extend through the holes 802 and into the attachment holes 604 to secure the lid 801 to the cylindrical disc 605. A sealing member (not shown) disposed in the annular indentation 606 is clamped in place between the cylindrical disc 605 and the lid 801 to provide a fluid-tight seal between the cylindrical disc 605 and the lid 801.

[0187] The optical system 800 includes a pressure compensator in the form of a syringe 806. The syringe 806 is in fluid communication with the pressure compensating cavity 603. A piston within the syringe 806 may be moveable in order to increase or reduce an internal volume to minimise a pressure differential between the internal volume and the environment exterior of the fluid-tight housing 600.

[0188] The optical system 800 includes a fill port 805 configured to allow a fluid to be introduced into and / or drained from the optical system recess 601. The fill port 805 communicates with the filling cavity 605. When the fill port 805 is not in use the fill port may be closed with a fluid tight seal. In use, the optical system recess 601 is filled at least partially with an inert, optically transparent medium. The optical system recess 601 may be filled substantially entirely with the inert, optically transparent medium. The inert, optically transparent medium may include a resin, a gel or a fluid, e.g. a liquid. The inert, optically transparent medium may include, or consist essentially of, an oil, e.g. a silicone oil.In implementations, the light source may include an LED light source and / or may be configured to emit uncollimated light. In other examples, other light sources may be used.

[0189] The sidewalls of the optical system recess 601 may prevent light from the light source 702 from taking any path other than one described above. The sidewalls may be opaque.

[0190] The optical system 800 described with reference to Figures 6, 7 and 8 is suitable for use as, for example, a fluorometer.

[0191] For example, the optical system 800 may be suitable for use with any fluorescenceemitting assay. For example, it may be used for fluorometric detection of molecules, including nucleic acids, toxins, and pollutants, particularly from within a fluid, e.g. liquid, sample. The optical system 800 may be suitable for use at depth.

[0192] The teaching of the present disclosure may have applications in, for example, fieldwork in various settings, including oceanography and / or environmental surveying and / or monitoring.

[0193] It will be appreciated that the teaching of the present disclosure may be applicable to optical analysis of samples in environments other than within bodies of water. For instance, an optical system of the present disclosure may be deployed, e.g. at depth, within any body of fluid, e.g. a body of a liquid.

[0194] It will be understood that the invention is not limited to the examples described above. Various modifications and improvements can be made without departing from the concepts disclosed herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to all combinations and sub-combinations of any one or more features disclosed herein.

Claims

1. CLAIMS1. An optical system comprising:a fluid-tight housing having an interior that is configured, in use, to be filled at least partially with an optically transparent medium;at least one reflector disposed at least in part within the interior; and a pressure compensator operably connected to the fluid-tight housing and configured to minimise a pressure differential between the interior of the fluid-tight housing and an environment exterior of the fluid-tight housing.

2. An optical system comprising:one or more optical system units, one or more of the optical system units comprising:a fluid-tight housing having an interior that is configured, in use, to be filled at least partially with an optically transparent medium;at least one reflector disposed at least in part within the interior of the fluid-tight housing;at least one optical window disposed in a wall of the fluid-tight housing; anda pressure compensator connected to the fluid-tight housing and configured to minimise a pressure differential between the interior of the fluid-tight housing and an exterior of the fluid-tight housing;wherein at least a portion of one or more of the reflectors is / are arranged such that light that enters the interior of the fluid-tight housing via one of the optical windows is incident upon one or more of the reflectors before leaving the interior of the fluid-tight housing via one of the optical windows and / or vice versa.

3. The optical system of claim 2, wherein two of more of the optical system units are arranged in optical series such that light passes sequentially through the optical system units arranged in the optical series.

4. The optical system of claim 1, claim 2 or claim 3, wherein: one or more of the reflectors is / are operable to produce collimated light from uncollimated light and / or vice versa; and / or one or more of the reflectors is / are operable to produce focused light from collimated light and / or vice versa.

5. The optical system of any one of the preceding claims, wherein at least one of the reflectors includes a mirror.

6. The optical system of any one of the preceding claims including a fill port configured to allow a material to be filled and / or drained from the interior of the fluid-tight housing.

7. The optical system of any one of the preceding claims, wherein the pressure compensator includes a syringe or a piston in fluid communication with the interior.

8. The optical system of any one of the preceding claims, wherein the pressure compensator includes an elastic zone configured to deform, in use, thereby increasing or reducing a volume including the interior, to minimise the pressure differential between the interior and the environment exterior of the fluid-tight housing.

9. The optical system of any one of the preceding claims including at least one light source.

10. The optical system of any one of the preceding claims including one or more sample holders configured to hold, in use, a sample for optical analysis.

11. The optical system of claim 10, wherein one or more of the sample holders include a flow cell.

12. The optical system of any one of the preceding claims including one or more filters or irises or light blockers.

13. The optical system of any one of the preceding claims including one or more detectors.

14. The optical system of any one of the preceding claims, wherein one or more elements of the optical system disposed at least partially within the interior of the fluid-tight housing is / are couplable to the interior of the fluid-tight housing.

15. The optical system of any one of the preceding claims, wherein one or more optical windows is / are disposed in a wall or walls of the fluid-tight housing.

16. The optical system of any one of the preceding claims, wherein: the optically transparent medium is inert; and / or the optically transparent medium includes a resin, a gel and / or a fluid, e.g. a liquid; and / or the optically transparent medium includes an oil, e.g. a silicone oil.

17. The optical system of any one of the preceding claims including a data logger arranged to log data from sample analysis carried out using the optical system.

18. An optical system unit comprising:a fluid-tight housing having an interior that is configured, in use, to be filled at least partially with an optically transparent medium;at least one reflector disposed at least in part within the interior of the fluid-tight housing;at least one optical window disposed in a wall of the fluid-tight housing; anda pressure compensator connected to the fluid-tight housing and configured to minimise a pressure differential between the interior of the fluid-tight housing and an exterior of the fluid-tight housing;wherein at least a portion of one or more of the reflectors is / are arranged such that light that enters the interior of the fluid-tight housing via one of the optical windows is incident upon one or more of the reflectors before leaving the interior of the fluid-tight housing via one of the optical windows and / or vice versa.

19. Use of an optical system according to any one of claims 1 to 17 or an optical system including an optical system unit according to claim 18 in optical analysis of one or more samples.

20. The use of claim 19, wherein one or more of the samples includes a fluid and one or more species of interest contained in the fluid.

21. The use of claim 19 or clam 20, wherein the optical analysis is carried out at depth.

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