Spectroscopic instrument

1. A spectroscopic instrument, comprising:

a compartment which houses spectroscopic instrument components and is arranged to receive desiccant to protect the instrument components;

a deformable container having at least one wall portion which is movable within the compartment so as to vary a volume of the compartment that is occupied by the deformable container as the container is deformed, the interior of the deformable container being in fluid communication with the surroundings of the instrument, such that a difference in pressure between the compartment and the surroundings tends to cause the deformable container to deform, moving the wall portion; and

at least one valve for allowing fluid communication between the compartment and the surroundings, when a pressure difference between the compartment and the surroundings exceeds a predetermined threshold.

2. A spectroscopic instrument according to claim 1 in which two valves are provided, one being an over-pressure valve for relieving over-pressure in the compartment and one being an under-pressure valve for relieving under-pressure in the compartment.

3. A spectroscopic instrument according to claim 1 in which the deformable container is of a laminate material, the laminate material comprising at least one plastic layer and at least one metallic film layer.

4. A spectroscopic instrument according to claim 1 in which the deformable container comprises a bag.

5. A spectroscopic instrument according to claim 4 in which the bag comprises two or more walls which are heat sealed together.

6. A spectroscopic instrument according to claim 1 which comprises a tube which is arranged to allow fluid communication between the interior of the deformable container and the surroundings.

7. A spectroscopic instrument according to claim 6 in which the tube is mounted on the deformable container.

8. A spectroscopic instrument according to claim 6 in which a wall of the deformable container comprises an aperture through which the tube extends and a seal is provided between the tube and the material of the deformable container to seal against at least one of ingress and egress of fluid through the aperture other than through the tube.

9. A spectroscopic instrument according to claim 6 in which the tube is mounted to the compartment.

10. A spectroscopic instrument according to claim 6 in which a wall of the compartment comprises an aperture through which the tube extends, and a seal is provided between the tube and the compartment wall to seal against at least one of ingress and egress of fluid through the aperture in the compartment wall other than through the tube.

11. A spectroscopic instrument according to claim 1 in which, when at its maximum extent, the deformable container occupies between 5% and 50% of the volume of the compartment.

12. A spectroscopic instrument according to claim 1 in which, when at its maximum extent, the deformable container occupies between 10% and 15% of the volume of the compartment.

13. A spectroscopic instrument, comprising:

at least one spectroscopic instrument component being sensitive to moisture;

a compartment for housing the at least one spectroscopic instrument component and arranged to receive desiccant to protect the at least one spectroscopic instrument component;

a deformable container having at least one wall portion which is movable within the compartment so as to vary a volume of the compartment that is occupied by the deformable container as the container is deformed, the interior of the container being in fluid communication with the surroundings of the instrument, such that a difference in pressure between the compartment and the surroundings tends to cause the deformable container to deform, moving the wall portion; and

at least one valve for allowing fluid communication between the compartment and the surroundings, when a pressure difference between the compartment and surroundings exceeds a predetermined threshold.

14. A spectroscopic instrument according to claim 13 in which two valves are provided, one being an over-pressure valve for relieving over-pressure in the compartment and one being an under-pressure valve for relieving under-pressure in the compartment.

15. A spectroscopic instrument according to claim 13 in which the deformable container is of a laminate material, the laminate material comprising at least one plastic layer and at least one metallic film layer.

16. A spectroscopic instrument according to claim 13 in which the deformable container comprises a bag.

17. A spectroscopic instrument according to claim 13 which comprises a tube which is arranged to allow fluid communication between the interior of the deformable container and the surroundings.

18. A spectroscopic instrument according to claim 17 in which the tube is mounted on the deformable container.

19. A spectroscopic instrument according to claim 17 in which a wall of the deformable container comprises an aperture through which the tube extends and a seal is provided between the tube and the material of the deformable container to seal against at least one of ingress and egress of fluid through the aperture other than through the tube.

20. A spectroscopic instrument according to claim 17 in which a wall of the compartment comprises an aperture through which the tube extends, and a seal is provided between the tube and the compartment wall to seal against at least one of ingress and egress of fluid through the aperture in the compartment wall other than through the tube.