Optical limiter device and an optical arrangement comprising said device |
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申请号 | EP07118681.1 | 申请日 | 2007-10-17 | 公开(公告)号 | EP2051125B1 | 公开(公告)日 | 2014-11-26 |
申请人 | SAAB AB; | 发明人 | Gårdbäck, Elisabeth; Elg, Alf-Peter; | ||||
摘要 | |||||||
权利要求 | |||||||
说明书全文 | This invention relates to an optical limiter device and an optical arrangement comprising such an optical limiter device Existing optical limiting devices comprise two lenses arranged so that an intermediate image is formed in a perpendicular plane between them. In the intermediate image plane is an optical limiter disposed. The limiter can be of several different materials. Optical limiters are for example known in documents Oculars are known that comprises a non linear attenuator device. The article of The described existing devices are not applicable to cameras, binocular or sensor devices, oculars or optical systems in general. The existing optical limiting devices are built into existing optical systems. This is a complicated operation. To achieve good optical limiting properties, it is important to have high intensity inside the limiter material, therefore a small point spread function, is desired. One of the problems with known limiter materials is that they have high linear absorption. The limiter material needs to be kept as thin as possible to limit the absorption losses. I order to provide an optical limitation in a thin limiter material, accurate focusing is essential. A more accurate focusing also provides a higher intensity in the intermediate image and this provides for better limitation properties since a non linear material in many cases has a threshold can begin its limiting more accurately. This is difficult to achieve with an inbuilt device since the optical system, e.g. binocular or camera, ocular or sensor device, is generally not designed to provide optimal intermediate images. Instead, optical systems are optimized with regard to the image plane, i.e. the plane where the image to be treated is formed, e.g. the film plane in a camera. Another problem with the solution incorporated optical limiter into a passive optical system is that the focusing position in the image plane is often changed when the temperature is altered. This has the effect that the intermediate focus for the limiter is changed without any control, giving effects which decrease or destroy the ability to limit. This means that for optimal operation of the limiting material, a refocusing must be performed to meet the focus change. Generally, an optical system, such as a binocular, camera, ocular, or sensor device, is not adapted to perform such refocusing in a plane where an intermediate image is formed. This means that the optical limiter's performance is degraded as the focus in the intermediate image is changed. One of the objects of the present invention is to provide an optical limiter that can be fitted to existing equipment, which reduces the intensity above a certain level of intensity. To reduce at least some of the failings discussed above the solution comprising the features of claim 1 is proposed. Said optical limiter device provides ability to accurately focus the incoming electromagnetical waves so that a well focused intermediate image is provided. This provides for more optimal use of the non limiter material, and the possibility to refocus, should that be necessary. Refocusing can be performed with out altering of the focus of the optical equipment that the optical limiter device is set to protect. The optical limiter devices with the individually adjustable focus of said first lens device provides for a reduced thickness of the optical limiter element in said optical limiter. The optical limiter device is arranged so that the second lens device's focus can be adjusted independently so that the waves leaving the optical limiter device can be adjusted to have substantially the same angle to the optical axis as the waves inciding to the optical limiter device. This has the effect that it is possible to adjust the optical limiter device in a manner so that the optical limiter device perturb the incoming electromagnetical waves as little as possible. In one embodiment a joint locking mechanism is comprised so that when the locking mechanism is locked the focusing of one of the lens devices generates a focusing of the other lens device. This has the effect that the focusing of the two lens devices can be performed in the same operation. In one embodiment first lens device comprises an objective. In one embodiment the second lens device comprises an objective. The optical limiter device is arranged to comprise means to be detachably mountable on an optical system such as a camera, a binocular, night vision goggles an optical sight or glasses. This has the effect that the limiter can be detached and used on several optical systems. It also makes it easier for a user to clean and perform maintenance on the optical limiter. In one embodiment said means comprises a screw and clamp arrangement. In one embodiment said means comprises a clamp and hook arrangement. In one embodiment said means comprises a hook and loop arrangement. In one embodiment said means comprises a thread arranged adjacent said second lens device for mounting on an optical device. Accordingly any optical device can be equipped with said optical limiter device. This yields a powerful, efficient and yet economic solution to limit high intensity electromagnetical waves in an existing device. In the proposed optical limiter device the electromagnetic waves leaving said optical limiter device has essentially the same direction as the inciding waves unless the waves entering has an intensity over a certain predetermined level. This has the effect that the optical limiter device is not interfering with the device it's set to protect. When incoming radiation having intensity above this level enters, the optical limiter device reduces the intensity of the incoming radiation and a good protection is offered to the equipment or eye on which the optical limiter device is fitted. In one embodiment is an optical limiter provided wherein said non linear device is activated at a predetermined intensity level. In one embodiment is an optical limiter provided wherein the electromagnetical waves that are processed is comprised throughout the electromagnetical spectrum. One embodiment comprises an optical arrangement comprising an optical limiter device of the mentioned embodiments, the arrangement comprises an optical system such as a camera, a binocular, or night vision goggles wherein said optical limiter device's focus is adjustable independently of the focus of the optical device.
In In The focusing units 1, 2 above are preferably lens devices. The focusing of the focusing units is performed in any manner known to the person skilled in the art. In one embodiment they are objectives comprising several lenses. The focusing of the lens devices can be performed individually. I.e the focusing can be performed individually without interaction between the two lens devices. For example by altering the distance of the lens device's individually with regard to the focusing plane. Internal focusing in the lens devices is preferable. In one embodiment the two focusing units comprised of two lens devices, have a joint locking mechanism, that can is manually operated. The Joint locking mechanism could for example be a slidable housing which in a first position only acts one the lens devices and when slid acts on both lens devices. When in this second mode the both focusing mechanisms of the lens devices of the focusing units acts dependently of each other. I manner of operating the optical limiter device 20 could be, adjust the first lens device so that a good intermediate image is provided, adjust the second lens device to arrive at essentially non perturbed groups of exiting rays, and then actuating said locking mechanism for further adjustments of both lens devices at the same time. Of course one can imagine operating manners where the locking mechanism is not used for further adjustments. Even though the embodiments above and the accompanying figures discloses parallel groups of rays of electromagnetical ways inciding and exiting the optical limiter device 20, in reality waves from close objects will be converging and not parallel. The optical limiter device 20 is of course arranged to handle rays of electromagnetical waves inciding from all distances, and not only rays inciding from long distances where the rays are essentially parallell. The optical limiter device 20 of the preferred embodiment can preferably be used in several different applications, for example as a protection for a camera The optical limiter device 20 together with the optical system is an optical arrangement comprising an optical limiter device of the mentioned embodiments, the arrangement comprises an optical system such as a camera, a binocular, or night vision goggles wherein said optical limiter device's focus is adjustable independently of the focus of the optical device. To attach the optical limiter device 20 in these different application several different techniques can apply, such as a screw and clamp arrangement, a hook and loop arrangement, a clamp and hook arrangement. Within the scoop other ways of attaching is of course possible such as incorporating a thread arranged adjacent said second lens device for mounting on said optical device. When the optical limiter device 20 in any embodiment above is used alone in front of the human eye, several ways of attachment for convenient use can be imagined. It's of course possible to hold the device for a shorter period. But attachment on glasses or other more stable attachment is preferred. |