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WO-2026093077-A1 - TMA TELESCOPE HAVING TWO OPTICAL CHANNELS

WO2026093077A1WO 2026093077 A1WO2026093077 A1WO 2026093077A1WO-2026093077-A1

Abstract

The invention relates to a three-mirror anastigmat telescope, comprising at least a primary mirror (1), a secondary mirror (2) positioned in front of the primary mirror (1) such that the primary and secondary mirrors have optical surfaces (1.1, 2.1) opposite one another, a tertiary mirror (3) having an optical surface (3.1) opposite the optical surface (2.1) of the secondary mirror (2), and a first optronic sensor (10) positioned opposite the tertiary mirror (3). The telescope comprises a second optronic sensor (20) positioned behind the secondary mirror (2) and the optical surface of the secondary mirror (2.1) has a dichroic treatment (2') intended to separate an incident luminous flux reflected by the primary mirror (1) into a first luminous flux reflected towards the first optronic sensor (10) via the tertiary mirror (3) and a second luminous flux transmitted to the second optronic sensor (20), the first luminous flux and the second luminous flux being in different spectral bands and the secondary mirror (2) being transparent to the spectral band of the second luminous flux.

Inventors

  • RIGUET, François
  • RODOLFO, Jacques

Assignees

  • SAFRAN REOSC

Dates

Publication Date
20260507
Application Date
20251021
Priority Date
20241028

Claims (8)

  1. 1. An anastigmatic three-mirror telescope, comprising at least one primary mirror (1), a secondary mirror (2) positioned in front of the primary mirror (1) such that the primary and secondary mirrors have optical surfaces (1.1, 2.1) opposite each other, a tertiary mirror (3) having an optical surface (3.1) opposite the optical surface (2.1) of the secondary mirror (2), and a first optronic sensor (10) positioned opposite the tertiary mirror (3), characterized in that the telescope comprises a second optronic sensor (20) positioned behind the secondary mirror (2) and the optical surface of the secondary mirror (2.1) comprises a dichroic coating (2') arranged to separate an incident light flux reflected by the primary mirror (1) into a first light flux reflected towards the first optronic sensor (10) via the tertiary mirror (3) and a second light flux transmitted to the second optronic sensor (20). the first luminous flux and the second luminous flux belonging to different spectral bands and the secondary mirror (2) being transparent to the spectral band of the second luminous flux.
  2. 2. Telescope according to claim 1, having an aperture diaphragm placed at the level of the secondary mirror (2).
  3. 3. Telescope according to claim 1 or 2, comprising at least one field corrector (30) disposed between the secondary mirror (2) and the second sensor (20).
  4. 4. Telescope according to claim 3, wherein the field corrector (30) is a lens field corrector.
  5. 5. Telescope according to any one of the preceding claims, wherein the secondary mirror (2) has a rear surface (2.2) shaped as a lens to put in forms the second beam of light.
  6. 6. Telescope according to any one of the preceding claims, wherein the first luminous flux comprises at least one wavelength in the visible range.
  7. 7. Telescope according to any one of the preceding claims, wherein the second luminous flux comprises at least one wavelength in the infrared range.
  8. 8. Telescope according to claims 6 and 7, wherein the primary mirror (1) and the tertiary mirror (3) are made of silicon carbide and the secondary mirror (2) is made of silicon.

Description

TMA TYPE TELESCOPE WITH TWO OPTICAL CHANNELS The present invention relates to the field of optics and more particularly to TMA type telescopes, that is to say, three-mirror anastigmatic telescopes. BACKGROUND OF THE INVENTION It is known from TMA type telescopes, comprising at least one primary mirror, a secondary mirror placed in front of the primary mirror in such a way that the primary and secondary mirrors have optical surfaces facing each other, a tertiary mirror having an optical surface facing the optical surface of the secondary mirror, and an optronic sensor placed facing the tertiary mirror to capture a light flux reflected successively by the primary mirror, the secondary mirror and the tertiary mirror. Some telescopes of this type are designed to have two separate optical paths leading to two sensors sensitive to distinct spectral bands, such as an infrared sensor and a visible sensor. To achieve this, dichroic plates are placed between the mirrors to separate the incident light into infrared light transmitted to the infrared sensor and visible light reflected back to the visible sensor. This results in an increased telescope size. Furthermore, the use of a dichroic plate in a converging beam (at the telescope's output) introduces aberrations into the wavefront of the light beam transmitted by the dichroic plate. These aberrations can be difficult to correct to obtain an image of the expected quality. SUBJECT OF THE INVENTION The invention aims in particular to provide a telescope that at least partially remedies the aforementioned drawbacks. SUMMARY OF THE INVENTION To this end, the invention provides a three-mirror anastigmatic telescope comprising at least one primary mirror, a secondary mirror positioned in front of the primary mirror such that the primary and secondary mirrors have optical surfaces facing each other, and a tertiary mirror having an optical surface facing the optical surface of the secondary mirror. The telescope includes a first optronic sensor positioned opposite the tertiary mirror and a second optronic sensor positioned behind the secondary mirror. The optical surface of the secondary mirror includes a dichroic coating arranged to separate an incident light beam reflected by the primary mirror into a first light beam reflected towards the first optronic sensor via the third mirror and a second light beam transmitted to the second optronic sensor. The first and second light beams belong to different spectral bands, and the secondary mirror is transparent to the spectral band of the second light beam. Thus, the secondary mirror will split the incident light beam reflected by the primary mirror into a first beam of light reflected towards the first sensor and a second beam of light transmitted towards the second sensor. Positioning the second sensor behind the secondary mirror helps to minimize its transverse dimensions. Furthermore, this arrangement simplifies the optical formula, avoids spectral separation downstream of the telescope, and allows for a large aperture ratio for the second spectral band by placing it directly on the side of the primary mirror's focal point. Depending on optional features, used individually or in whole or in combination: - the telescope includes at least one first field corrector positioned between the secondary mirror and the second sensor; - the first field corrector is a lens-based field corrector; - the secondary mirror has a rear surface shaped like a lens to shape the second beam of light; - the first luminous flux includes at least one wavelength from the visible range; - the second luminous flux includes at least one wavelength from the infrared range; - the primary mirror and the tertiary mirror are made of silicon carbide and the secondary mirror is made of silicon; - the telescope has an aperture diaphragm located at the secondary mirror. Other features and advantages of the invention will become apparent from the following description of a particular and non-limiting embodiment of the invention. BRIEF DESCRIPTION OF THE DRAWINGS Reference will be made to the attached drawings, including: [Fig. 1] is a schematic axial cross-sectional view of a telescope according to the invention; [Fig. 2] is an isolated view of the first optical path of the telescope according to the invention; [Fig. 3] is an isolated view of the second optical path of the telescope according to the invention. DETAILED DESCRIPTION OF THE INVENTION With reference to the figures, the telescope according to the invention is of the TMA type and comprises at least one primary mirror 1, one secondary mirror 2, and one tertiary mirror 3. The primary mirror 1 and the secondary mirror 2 have surfaces Optical surfaces 1.1 and 2.1 are positioned opposite each other. The tertiary mirror 3 has an optical surface 3.1 opposite the optical surface 2.1 of the secondary mirror 2. The primary mirror 1, the secondary mirror 2, and the tertiary mirror 3 each have rear surfaces oppo