Image recording assembly and review system with same

State of the art

In the construction of an image pickup device such as a camera with image sensors, stray light effects are problematic. Stray light effects are produced, inter alia, that reflections on different surfaces and edges occur within an optical or along an optical path of the camera. An attempt is made to reduce such stray light effects by edges as far away from the optical path, blackened surfaces and glass surfaces are generously reimbursed. The surface of the image sensor, however, can not be reimbursed, reflections on its surface can not be avoided. An image sensor, for example based on silicon reflected back about 50 to 70 percent of incident radiation. Does this reflected light to a more reflective surface, so it is thrown back to the image sensor. The result are bright spots in the camera image and called Ghosts or double vision.

A use of a camera with an image sensor is in a night vision system of a vehicle. The document<patcit id="pcit0001" dnum="EP0490029A2"><text>EP 0490029 A2</text></patcit> discloses an active night vision system for a vehicle as a further element, aside from a camera, a lighting arrangement. The illumination arrangement is configured such that it emits polarized light. The camera comprises a polarizer or polarizing filter on the incident light whose plane of polarization of the polarizer does not match the associated polarization plane is blocked.

Does emitted from the lighting arrangement of light on objects around, so the light is scattered. Due to the scattering the formerly uniform polarization of the light is lost. Does the scattered light on the camera, then a portion of the light passing through the polarizer of the camera and recorded by the image sensor of the camera.

Emitted polarized light of a second active night vision system, in particular of an oncoming vehicle can be in a suitable arrangement of the polarizer and the illumination assembly is blocked by the polarizer of the camera. In this way it can be avoided that the camera will be outshone or blinded by the light of oncoming vehicles, which has a much higher intensity than the scattered light.

Despite the use of polarized light at the illumination arrangement and the polarizer in the imaging device, ie, the camera, the image sensor may by undesirable reflection paths, as described above, outshone by the light of oncoming vehicles or blinded. This affects the function of such an active night vision system.

Disclosure of the Invention

The imaging device according to the invention comprises at least one image sensor, a polarization filter for filtering light, in particular in the visible, ultraviolet or infrared wavelength range, in dependence on its polarization plane, and an optically active means for rotating the polarization plane of light, wherein the polarization filters and the optically active means are arranged in a common beam path in front of the image sensor so that at least meets a portion of the incident light first on the polarizing filter, then the optically active agent and then on the image sensor.

Incident light is polarized by the polarizing filter, that is filtered with respect to its plane of polarization. Subsequently, the light hits the optically-active agents, whereby the polarization plane of light is rotated by a certain angle. Thereafter, the light strikes the image sensor. The proportion of light that is reflected on the image sensor, meets a second time on the optically active medium, whereby the plane of polarization of the light is rotated a second time by a certain angle. Finally, this proportion of light reflected again encounters the polarization filter. By selecting the angle through which the optically active means to rotate the polarization plane of the light, can be effected in that the proportion of light reflected upon impinging on the polarization filter having a polarization plane which is different from the polarization plane, which makes the polarization filter pass, so that the polarizing filter at least blocks a portion of the reflected light on the image sensor portion.

Preferably, the polarization filter is designed such that it the proportion of light which it locks, at least partially, advantageously largely absorbed. In this way it can be prevented that this light component falls again by reflection on the image sensor and leads to undesirable effects.

Further, preferably, the optically active means are designed such that it by about 45 degrees and λ / 8 at the wavelength λ rotates the plane of polarization of the light. Twice to impinge on the optically active medium, the polarization plane of light is rotated by 90 degrees and λ / 4 in this case, whereby the blocking of the reflected light on the image sensor portion is maximized by the polarization filter. It can be chosen other angles, but may then decrease the effectiveness of the arrangement, to reduce stray light. Likewise may be provided that rotate the plane of polarization of light further funds.

optically active agent disposed no further optical components - in an advantageous embodiment are provided between the polarizer and the optically active means in the beam path image sensor - polarizing filter. Such optical components would possibly lead to stray light that could not be suppressed. Said arrangement is therefore advantageous for a high efficiency of the stray light reduction.

The inventive active night vision system of a vehicle includes an image pick-up device according to the invention and a lighting assembly, the lighting arrangement is designed so that this polarized light emits to illuminate the area, and the polarizing filter of the imaging device is aligned with this polarity.

By using the imaging device according to the invention may stray light that is particularly generated by incident light from oncoming vehicles can be reduced, thus making it possible reduce a flare and glare of the image sensor of the imaging device or even eliminate.

Brief Description of Drawings

The invention will now be described in greater detail with reference to embodiments which are partially illustrated by figures. In which:<dl id="dl0001" compact="compact"><dt>Fig. 1A</dt><dd>a first embodiment of an imaging device according to the invention;</dd><dt>Fig. 1B</dt><dd>too <figref idrefs="f0001">Fig. 1</figref> modified second embodiment;</dd><dt>FIG. 2</dt><dd>a third embodiment of an imaging device according to the invention;</dd><dt>Fig. 3</dt><dd>an inventive night vision system with an imaging device according to the invention; </dd><dt>Fig. 4</dt><dd>a driving scene of a vehicle with the night vision system according to the invention from <figref idrefs="f0002">Fig. 3</figref> in plan view.</dd></dl>

The same or corresponding items are identified by the same or corresponding reference numerals.

Embodiments of the invention

<figref idrefs="f0001">figure 1a</figref> shows a first embodiment of an imaging device according to the invention 8a to an image sensor 1a, here a CMOS or CCD sensor based on silicon, a polarization filter 2a for polarizing light, in particular in the visible, infrared or ultraviolet range, an optically active means 3a rotating the polarization plane of light, in this case an optically active layer 3, a lens 5 and a support 6 comprises on which the image sensor is arranged 1a. An optical axis 4 in this case defines the beam path.

The lens 5 has a convex-plane formed with a convex front face and arranged at a distance to the image sensor 1a. Through the lens 5 an incident light 9-1 along the optical axis 4 is bundled in parallel. The polarizing plate 2a is a layer plane on which the image sensor 1a facing underside applied 5a of the lens. 5 The optically active layer 3a is applied directly to the lens 5 facing surface 11a of the image sensor 1a. The polarizing filter 2 is designed such that there is light 9 passes in a given preferential plane of polarization and absorbing other light. The optically active layer 3a is formed such that it rotates the plane of polarized light by 45 degrees. Between the polarizer 2 and the optically active layer 3a are located in the beam path polarizing filter 2a - optically active layer 3a - image sensor 1 in this embodiment, no further optical components; also is advantageously no more cover the image sensor 1a necessary because it is protected by the layer 3a.

Alternatively, in accordance with <figref idrefs="f0001">Fig. 1B</figref> a Glaslid 10 or a pane of glass from the image sensor 1a spaced, ie be provided between the image sensor 1a and 2a of the polarization filter, said Glaslid 10 may be paid on its top and / or bottom. Advantageously, the optically active means 3a applied as an optically active layer on the top and / or bottom of the Glaslids 10th

In both embodiments, the <figref idrefs="f0001">Fig. 1 a, b</figref> applies incident light 9-1 after passing through the lens 5 on the polarizing filter 2 and is filtered through this. The light portion 9-2 with allowable polarization direction occurs below the optically active layer 3 and impinges on the image sensor 1a. The light fraction with not allowed polarization direction (ie, in particular light orthogonal to the preference polarization plane polarization plane) is absorbed by the polarizer 2a. The image sensor 1a absorbs about 30 to 50 percent of light 9-2, wherein a portion is converted into electric charge to the output of an image signal S1. The remaining 50 to 70 percent are reflected back as light portion 9-3 and pass again the optically active layer 3a. The polarization plane of the reflected light component on the image sensor 1a 9-3 is thus rotated by a total of 90 degrees. This reflected and rotated light fraction 9-3 will now face the polarizer 2a and is completely absorbed by this completely or almost. It is thus prevented from further reflections arise and make light components undesirable on the image sensor 1a. A high absorption coefficient and low reflectivity of the polarizing filter 2a are particularly advantageous for this purpose.

In a variant of this, the polarization filter 2a and / or the optically active means 3a may be formed as discrete components.

<figref idrefs="f0001">figure 2</figref> shows a further embodiment of an imaging device according to the invention. The imaging device 8b comprises 3b an image sensor 1b, a polarizing filter 2b for polarizing light and an optically active means 3b for rotating the plane of polarization of light, here is an optically active layer. The polarization filter 2b, the optically active layer 3b and the image sensor 1b are formed as layers of a layer system. The underside of the image sensor 1b is disposed on a support 6b. immediately above the image sensor 1b follows 3b the optically active layer. As the next layer is followed by a transparent body, here a glass plate 7 which is formed as a protective layer for the image sensor 1b. The layer system is completed by the polarizer 2b, which constitutes the top layer. Also in this embodiment absorbs the polarization filter 2b does not transmitted light.

Alternatively, the polarizer 2b can also be arranged on the underside of the glass sheet 7th

In a further variant, the polarizer 2b as a layer on the image sensor 1b facing away from top of the glass plate 7 and the optically active means 3b may be applied for rotating the plane of polarization of light as an optically active layer on the underside of the glass sheet 7, wherein between the image sensor 1b and the optically active means 3b remains only a narrow air gap. Alternatively, also the optically active means 3b 2b directly to the image sensor 1b and the polarizing filters have been applied to the underside of the glass sheet. 7

As image sensors, in particular imaging sensors or pixel array sensors, in particular CMOS or CCD sensors that output an image signal S1, z. B. for image processing and display are on a display and / or for evaluating a driver assistance system.

Materials that can be used as polarization filters 2a and 2b, those skilled in the well known. As optically active agents, for example, coatings or discrete components are based on Polyphenylenamin or chiral polyaniline.

Inventive image pickup devices are particularly suitable for an active night vision system of a vehicle. <figref idrefs="f0002">Fig. 3</figref> shows an inventive night vision system 15 in which a control device 16 outputs a drive signal S2 to output to a lighting assembly 18 for dispensing polarized radiation 9, such. as a laser, the polarized light (or radiation) 9 in the near infrared for illuminating an environment radiates , Alternative lighting arrangements 18 are for example LEDs or gas discharge lamps with correspondingly set polarization devices, such as polarizing filters. The night vision system of the invention 15 further comprises an imaging device 8a or 8b in accordance with one of the embodiments described, the polarized light (or radiation) 9 receives a preferential polarization plane. When using an imaging device 8a them accordingly comprises a polarizing filter 2a for polarizing or polarization filtering the incident light 9. The polarizing plate 2a, the optically active means 3a and the image sensor 1a are tuned to a wavelength range in the near infrared region of the wavelength range of the illumination assembly 18 emitted light 9 corresponds or at least this is included. The lighting assembly 18 and the imaging device 8a are aligned such or oriented to one another that the plane of polarization of the light emitted 9 of the polarizing filter associated preferential polarization plane corresponds.

The controller 16 determines from its control signals S2 and the received image signals S1 an image and possibly also distances etc in the detected driving scene and gives an output signal S3 z. B. to a display or to its control device and / or an electronic stability program or a driver assistance system for from image analysis.

<figref idrefs="f0002">Fig. 4</figref> shows a vehicle 20 with an inventive night vision system 15 on a roadway 21. The entire night vision system 15 or at least the imaging device according to the invention 8a or 8b are preferably positioned behind a windshield 22 of the vehicle 20 and collect against a detection range 24 of the track 21 and side areas, optionally also next to the vehicle 20 Collected objects O1, O2, O3 reflect a portion of the output light. 9

If one assigns such a night vision system 15 in the vehicle 20, for example, so that the plane of polarization of the emitted light 9 is at an angle of 45 degrees relative to the horizontal, which is usually dictated by the track 21, so is the light of an oncoming, also with such a night vision system equipped second vehicle is blocked by the polarizing filter of the imaging device of the first or own vehicle 20th Furthermore, reduced by the inventive imaging device 8a or 8b, the scattered light generated by unwanted reflection that falls on the image sensor 1a or 1b. A blooming or glare of the image sensor 1a or 1b by light of the active night vision system of an oncoming vehicle can be avoided.