LARGE SCALABLE APERTURE-COMBINED OPTICAL TELESCOPE

Abstract

It comprises optical assemblies that focus light onto individual first optical fibers which are combined together in a final single optical fiber, collecting a considerable amount of light from a target, to feed an instrument such as a spectrograph. The first optical fibers are kept centred on the target through image devices that also provide images, and these images can be combined to give rise to a high-quality image of the field surrounding the target. The final effective aperture of the device is scalable, using different numbers of optical assemblies and depending on their diameters.

Claims

14. A scalable aperture-combined optical telescope, comprising several optical assemblies, each comprising: an optical tube aimed to a target, with an aperture for receiving light, a light output and an output axis, an active optical package, associated to the light output, comprising: an atmospheric dispersion corrector associated to the light output, a focuser following the atmospheric dispersion corrector, a tip-tilt refractive compensator following the focuser, an image device, intended to receive the light from the tip-tilt refractive compensator and acquire images; a flat diagonal flip mirror following the tip-tilt refractive compensator, intended to reflect the light onto the image device, and which comprises a drilled hole with capacity of being aligned with the output axis of the optical tube, an alignment frame, following the flat diagonal flip mirror, a first optical fiber, fixed to the alignment frame, and inserted in the drilled hole of the flat diagonal flip mirror, intended to capture the incoming light from the target, wherein each first optical fiber is of multimode optical fiber (MMF) type, and the scalable aperture-combined optical telescope additionally comprising: a photonic lantern configured to combine several first optical fibers in a final single optical fiber of multimode optical fiber (MMF) type, by stacking and tapering the first optical fibers with high core-to-cladding ratios such that the claddings, when tapered, become too thin to efficiently confine light, and the final single optical fiber, that connects the photonic lantern to a measuring device.

15. The scalable aperture-combined optical telescope of claim 14, wherein the image device comprises a camera.

16. The scalable aperture-combined optical telescope of claim 15, wherein the image device additionally comprises a filter wheel positioned before the camera.

17. The scalable aperture-combined optical telescope of claim 15, wherein the camera is a CCD or CMOS low readout-noise camera.

18. The scalable aperture-combined optical telescope of any of the preceding claims wherein the optical assemblies are installed on a mount or several mounts that can aim to any specific location.

19. The scalable aperture-combined optical telescope of claim 14, wherein the measuring device is a spectrograph.

20. The scalable aperture-combined optical telescope of claim 14, wherein the measuring device is a polarimeter.

21. The scalable aperture-combined optical telescope of claim 14, wherein the measuring device is a photometer.

22. A method for obtaining images from a target, which uses the device of claim 14, and comprising the steps of: receiving a light into the optical tubes, correcting the light on the atmospheric dispersion corrector, reflecting the light on the flat diagonal flip mirror onto the image device, and acquiring images, adjusting the optical tube and/or the tip-tilt refractive compensator in order to center the light onto the drilled hole, focusing the light from the tip-tilt refractive compensator on the first optical fiber, combining the light from several first optical fibers of multimode optical fiber (MMF) type into a final single optical fiber via the photonic lantern configured to combine the first optical fibers in a final single optical fiber of multimode optical fiber (MMF) type, by stacking and tapering the first optical fibers with high core-to-cladding ratios such that the claddings, when tapered, become too thin to efficiently confine light, and feeding the light into the measuring device.

23. The method for obtaining images from a target according to claim 22, additionally comprising the step of: combining the images from the image devices in a final image, in an external device, using appropriate algorithms.

Description

DESCRIPTION OF THE DRAWINGS

[0052] To complement the description being made and in order to aid towards a better understanding of the characteristics of the invention, in accordance with a preferred example of a practical embodiment thereof, a set of drawings is attached as an integral part of said description wherein, with illustrative and non-limiting character, the following has been represented:

[0053] FIG. 1.—Shows an optical assembly in a second embodiment of the invention.

[0054] FIG. 2.—Shows two optical assemblies and a photonic lantern which combines the light from the first optical fibers coming from the optical assembly.

[0055] FIG. 3.—Shows a module of optical assemblies mounted on a mount.

[0056] FIG. 4.—Shows a group of modules connected and feeding the same measuring device which can be shared with other existing facilities (in the picture, the 3.5m telescope of Calar Alto observatory, for instance).

[0057] FIG. 5A.—Shows the first optical fibers being combined into a final single optical fiber in the photonic lantern.

[0058] FIG. 5B.—Shows a horizontal section of the photonic lantern.

PREFERRED EMBODIMENT OF THE INVENTION

[0059] With the help of FIGS. 1 to 5, a preferred embodiment of the present invention is described below.

[0060] The object of the invention consists on a scalable aperture-combined telescope, which comprises several optical assemblies, preferably more than three. Each of the optical assemblies comprises an optical tube (1), with an aperture (2) aimed to a target in the sky for receiving light, and a light output (3), for exiting the light. The optical tube (1) works as any common telescope optical tube (1), receiving the light and reflexing it inside, until it exists the optical tube (1) by the light output (3). The optical tube (1) is also defined by an output axis (16).

[0061] The optical assemblies, shown in FIGS. 1a and 1b, have each an active optical package, aligned with the output axis (16). Such active optical package is comprised of the next elements, placed in the following sequence: [0062] an atmospheric dispersion corrector (4), [0063] a focuser device (5), [0064] a tip-tilt refractive compensator (6), [0065] a flat diagonal flip mirror (7), which comprises a drilled hole (11) intended to be aligned with the output axis (16) of the optical tube (1), [0066] an alignment frame (17), which holds a first optical fiber (8) inserted in the drilled hole (11), and which is intended to receive the light, and [0067] an image device, intended to receive the light when it is reflected on the flat diagonal flip mirror (7).

[0068] The image device comprises a filter wheel (12), intended to filter the light reflected on the flat diagonal flip mirror (7), and a camera (13) following the filter wheel. The camera (13) could be, for example a cooled CCD (Charge Coupled Device) or CMOS (Complementary Metal-Oxide Semiconductor) low readout-noise camera (13).

[0069] The scalable aperture-combined optical telescope of the present invention combines multiple optical assemblies, preferably more than three, as seen in FIG. 2 (where only two assemblies are shown for drawing simplicity), resulting in a telescope with a larger effective aperture equivalent to the square root of the number of assemblies multiplied by the aperture of a single assembly. The light of the target is collected in the individual active optical package associated to each optical tube (1), by the first optical fiber (8).

[0070] The cameras (13) record the field of view of each optical assembly and acquire images. The gathered images are summed together to achieve a much better image in terms of sensitivity. The images are processed in an external device by using a special optimal combination algorithm. The main aim of the algorithm is to minimize the cosmetic defects of the camera (13), removing cosmic rays, hot pixels, electric nose spikes and/or diffraction effects caused by the telescope spiders, improving the signal to noise ratio.

[0071] The cameras (13) also keep the first optical fibers (8) well aligned to the output axis (16) of the optical tubes (1) by using the Tip-Tilt refractive compensators (6), working as guider devices.

[0072] Once the light is gathered by each first optical fibers (18), a photonic lantern (9) is used to combine all the light received from each optical assembly. Light from each of the optical assemblies will be combined into one final single optical fiber (10) through a photonic lantern (9), as seen in FIGS. 5A and 5B. The final single optical fiber (10) feeds the light into a spectrograph (18), allowing the light from all the optical assemblies to be summed together into a common spectrograph (18).

[0073] The photonic lanterns (9) of the present invention couple light from many MMFs (multimode optical fibers) to a single MMF by stacking and tapering single first optical fibers (8), with a core and a cladding, and with high core-to-cladding ratios such that claddings, when tapered, become too thin to efficiently confine light. The core of the final single optical fiber (10) is formed by fusing the cores of the first optical fibers (8), with the cladding formed from the single optical fibers (8).

[0074] The individual optical assemblies are attached to a common mount (14), as seen in FIG. 3. Each mount (14) with several optical assemblies attached is referred to as a module (15). Light from multiple modules (15) is collected in the same manner, combining the light received from each module (15) via a photonic lantern (9) and fed into a final single optical fiber (10) and a spectrograph (18), as seen in FIG. 4.

[0075] By repeating this scheme, larger effective apertures (2) or larger collecting areas can be achieved. As an example, nine modules (15) could correspond to a 15 m class telescope, depending on the exact aperture of the individual assemblies. Additionally, the concept results in a scalable and modular telescope, and could grow with time, depending of the total number of optical assemblies incorporated.

[0076] The current invention also comprises a method to operate the scalable aperture-combined optical telescope, for spectroscopic measurements and image acquisition. The steps of said method comprise receiving light in the optical tube (1), correcting the light on the atmospheric dispersion corrector (4), reflecting the light on the flat diagonal flip mirror (7) onto the image device and acquiring images with the cameras (13), adjusting the optical tube (1) and/or the tip-tilt refractive compensator (6)in order to centre the light onto the drilled hole (11) and therefore the first optical fiber (8), combining the light from several fibers (8) into a final single optical fiber (10) via the photonic lantern, feeding the light into the spectrograph (18), and combining the images in an external device acquired in the image device in a final image using appropriate algorithms. [0077] 1-13. (canceled).