Opto-electronic imaging systems are used, for example, in the field of space technology, for earth observation, in reconnaissance systems or in automotive engineering for recognizing obstacles. The sensor head of opto-electronic systems consists of front optics, for example, a lens objective or a telescope, detectors in the focal plane and electronics. The front optics, for example, reflecting telescopes as often used for space instruments have a curved image plane or a curved focal plane. However, conventional detector technology requires a planar design. To flatten the image surface, so-called field correctors or field flatteners must, therefore, be connected downstream of the telescopes or optics in order to be able to place a planar detector surface into the focal surface. In general, the field correctors consist of lens assemblies that can typically effect a correction of the image plane only in a limited region over the field of view.
FIG. 4 illustrates a conventional Cassegrain system that can be used as a reflecting telescope for space instruments. FIG. 5 illustrates the curved focal surface of a concave mirror. FIG. 6 illustrates a Quasi-Ritchey-Chrétien booster system with a conventional field corrector or its beam paths, respectively.
However, in many applications, a broad field of view is required, for example to achieve a broad swath width. A corresponding expansion of the visual field of the telescope is particularly required in a scanning pushbroom instrument. For reasons of stability, particularly to withstand the launching loads, reflecting telescopes are primarily used for geometric high-resolution space instruments. Furthermore, in many cases a broadband spectral sensitivity is required.
The detectors in the focal plane are the hearts of opto-electronic imaging systems. For example, conventional CCD detectors are often used as well as CMOS detectors with active pixel technology. These detectors have an integrated readout electronics and can be manufactured in one manufacturing process.
In the field of automotive engineering, cameras used for recognizing obstacles are required to have a large visual field or panorama cameras are used. However, these require complicated optics to achieve a large visual field and to reduce distortions. Correspondingly, the price for a camera or an imaging system for such applications is very high.
To achieve a better reproduction quality, very narrow thermo-mechanical tolerances are also required. The field correctors often restrict the spectral transmission range, which is caused, for example, by the narrow transmission range of the employed lens glasses.
Overall, the conventional opto-electronic imaging systems or detector designs exhibit significant disadvantages, such as the restriction of the field of view and the limitations of spectral transmission properties of the telescopes, a complex design with field correctors to create planar image planes, complicated and elaborate front optics and high costs.
Therefore, the objectives of the present invention include overcoming the aforementioned disadvantages, simplifying opto-electronic imaging systems and enabling wider fields of view (FOV).