Patent Description:
More precisely the invention relates to a cover for an illuminating and imaging system.

Interior cameras are used in the automotive industry to monitor the interior of the cabin. An interior camera typically comprises an RGB-IR image capture apparatus working both in the visible domain and in the infrared domain. Colors images are for example used for videoconferences or face recognition of the driver whereas infrared images are used for driver motoring. In order to acquire infrared images, the interior camera also comprises an infrared light source adapted to illuminate the interior of the cabin. For aesthetic reasons and for their protection, the image capture apparatus and the infrared light source are placed behind a window extending in front of them.

Unfortunately, the window acts as a light guide between the infrared light source and the image capture apparatus. A portion of the light emitted by the infrared light source is guided to the image capture apparatus which causes glare on the acquired images, especially on the infrared images. This portion is even more significant since the light source usually emits light at wide angles in order to illuminate the whole cabin.

<CIT> discloses a camera with IR illumination and a separator between the illumination source and the image sensor as well as an IR blocking coating on parts of the front window.

In this context, one object of the invention is to provide an illuminating and imaging system according to appended claim <NUM>.

Thanks to the cover according to the invention, when propagating in the window towards the image capture apparatus, infrared light reflects on the interface between the window and the layer (at the front surface) and part of this infrared light is absorbed at each reflection. The quantity of infrared light reaching the image capture apparatus is therefore greatly reduced thanks to the layer. Glare is therefore prevented.

In a particular embodiment, the separator is also adapted to absorb infrared light. Infrared light is therefore absorbed when it reflects on both the front and back surfaces of the window, in the vicinity of the separator.

Other advantageous and non-limiting features of the method according to the invention are:.

The invention relates to an illuminating and imaging system adapted to be placed inside an automotive vehicle and comprising:.

The following description, enriched with joint drawings that should be taken as non-limitative examples, will help understand the invention and figure out how it can be realized.

A cover <NUM> according to the invention is represented in <FIG>.

As shown in <FIG>, the cover <NUM> is designed to be used in combination with an illuminating and imaging system <NUM>. In the context of this disclosure, the illuminating and imaging system <NUM> is an interior camera for an automotive vehicle. The illuminating and imaging system <NUM> comprises an image capture apparatus <NUM> adapted to acquire images of a scene, which is here the cabin of the automotive vehicle, and an infrared light source <NUM> adapted to illuminate said scene with infrared light. The image capture apparatus <NUM> comprises a lens <NUM> and RGB-IR sensor <NUM> (for "Red-Green-Blue-Infrared") composed of color pixels and of infrared pixels. The image capture apparatus <NUM> is therefore adapted to acquire both color images and infrared images.

The cover <NUM> aims at protecting the illuminating and imaging system <NUM> and also at hiding parts of the illuminating and imaging system <NUM> for passengers of the vehicle. In the following, the cover <NUM> is described as installed with respect to the illuminating and imaging system <NUM>, that is to say in front of the illuminating and imaging system <NUM>.

As shown in <FIG>, the cover <NUM> comprises a frame <NUM> which is a support element adapted to be fixed around the illuminating and imaging system <NUM>, for example to the roof of the cabin. The frame <NUM> is for example made of polycarbonate, polymethylmethacrylate or polyamide.

The frame <NUM> delimits a first opening <NUM> and a second opening <NUM>. As shown in <FIG>, the first opening <NUM> is positioned in front of the light source <NUM> to allow infrared light to propagate to the scene. The second opening <NUM> is positioned in front of the image capture apparatus <NUM> to allow images of the scene to be acquired.

Between the first opening <NUM> and the second opening <NUM>, the frame <NUM> comprises a separator <NUM>. The separator <NUM> is interposed between the image capture apparatus <NUM> and the light source <NUM>, as shown in <FIG>. Classically, the separator <NUM> prevents direct illumination of the image capture apparatus <NUM> by the light source <NUM> in the sense that no ray of infrared light, emitted by the light source <NUM>, can reach the image capture apparatus <NUM> without being reflected. The separator <NUM> is formed here in a single piece with the whole frame <NUM>. In other words, the separator <NUM> is here a portion of the frame <NUM> which is characterized in being located between the image capture apparatus <NUM> and the light source <NUM>.

As shown in <FIG>, on top of the frame <NUM> (in the direction of the scene, i.e. of the cabin), the cover <NUM> comprises a window <NUM>. The window <NUM> extends in front of the image capture apparatus <NUM> and the light source <NUM>. Here, the window <NUM> extends in particular so as to cover the first opening <NUM> and the second opening <NUM>. The window <NUM> is here a plain plate in the sense that it comprises no holes or openings.

The window <NUM> is made of a transparent material which transmits both visible light and infrared light. The window <NUM> for instance has a transmission greater than <NUM>%, and preferentially greater than <NUM>%, in wavelength ranges comprised between <NUM> and <NUM> (visible light) and in wavelength ranges comprised between <NUM> and <NUM> (infrared light).

As shown in <FIG>, the window <NUM> may be substantially plane. Here, the window <NUM> more specifically fits an external surface <NUM> of the frame <NUM> as illustrated in <FIG>. In this way, the window <NUM> is supported by the frame <NUM>. In any case, the window <NUM> has a back surface <NUM> which is in contact with the frame <NUM> and a front surface <NUM> opposite to the back surface <NUM> and oriented toward the scene. Here, the back surface <NUM> and front surface <NUM> are substantially parallel and distant of a thickness comprised between <NUM> and <NUM>. The back surface <NUM> is more specifically in contact with the external surface <NUM> of the frame <NUM> and with the separator <NUM>.

As shown in <FIG>, on top of the window <NUM> (in the direction of the scene), the cover <NUM> comprises a layer <NUM> adapted to absorb infrared light. The layer <NUM> is, in particular, adapted to absorb the light emitted by the light source <NUM>. The absorption of the layer <NUM> may depend on the emission spectrum of the light source <NUM>. In a general manner, the layer <NUM> for example has an absorption greater than <NUM>% in a wavelength range comprised between <NUM> and <NUM>. To this end, the layer <NUM> may be made of a black ink, paint, or plastic material, such as polycarbonate.

The layer <NUM> lies on the front surface <NUM> of the window <NUM> opposite to the separator <NUM>. In other words, the layer <NUM> extends in contact with the front surface <NUM>. Preferentially, the layer <NUM> faces at least <NUM>% of a surface of the separator <NUM> which is in contact with the window <NUM>. More preferentially, the layer <NUM> faces all the surface of the separator <NUM> which is in contact with the window <NUM>, as represented in <FIG>.

The layer <NUM> has for example a thickness, here in a direction substantially perpendicular the front surface <NUM>, comprised between <NUM> and <NUM>. Preferentially, the layer <NUM> has a thickness comprised between <NUM> and <NUM> when it is made of ink. Preferentially, the layer <NUM> has a thickness comprised between <NUM> and <NUM> when it is made of plastic.

Here, as represented in <FIG>, the layer <NUM> extends on a vast majority the front surface <NUM>. Here, the layer <NUM> faces at least <NUM>% of the external surface <NUM> of the frame <NUM>. However, the layer <NUM> does not extend in front of the first opening <NUM> and the second opening <NUM>. In this way, the cabin can be correctly illuminated, and infrared images can be acquired.

Thanks to the layer <NUM>, infrared light beams <NUM> emitted by the light source <NUM> and propagating in the window <NUM> towards the image capture apparatus <NUM> are at least partly, if not totally, absorbed. Indeed, as illustrated in <FIG>, these beams <NUM> reflect on the interface between the window <NUM> and the layer <NUM>. At each reflection, these beams <NUM> are partially transmitted to the layer <NUM> and absorbed by the latest. The intensity of infrared light reaching the image capture apparatus <NUM> is therefore far lower as compared with a cover that would not include an infrared absorbing layer.

Preferentially, the layer <NUM> extends such that any ray of light emitted by the infrared light source <NUM> and guided by the window <NUM> to the image capture apparatus <NUM> reflects at least once on the interface between the window <NUM> and the layer <NUM>. This ensure that any ray of infrared light is absorbed by the layer <NUM> at least once.

Here, the separator <NUM>, and more generally the frame <NUM>, is also adapted to absorb infrared light. The frame <NUM> is for example made of black polycarbonate. Attenuation of the infrared light beam <NUM> therefore happens at the interfaces of the window <NUM> with both the layer <NUM> and the separator <NUM>.

In a remarkable way, the dimensions of the separator <NUM>, and therefore those of the layer <NUM>, are selected such that the infrared light beams <NUM> reflect multiple times at the interfaces of the window <NUM> with the layer <NUM> and the separator <NUM> before reaching the image capture apparatus <NUM> (as illustrated by the dotted arrow). To this end, the thickness of the window <NUM> is smaller than a width of the separator <NUM>. The width of the separator <NUM> is here defined as its dimension along a direction D1 from the infrared light source <NUM> to the image capture apparatus <NUM>. For instance, the thickness of the window <NUM> is comprised between <NUM> and <NUM>,<NUM> and the width of the separator <NUM> is comprised between <NUM> and <NUM>.

As shown in <FIG>, the layer <NUM> fits the shape of the front surface <NUM> of the window <NUM>.

As shown in <FIG>, on top of the layer <NUM> (in the direction of the scene), the cover <NUM> comprises an infrared coating <NUM>. The infrared coating <NUM> is adapted to absorb visible light and to transmit infrared light. For instance, the infrared coating <NUM> has a transmission greater than <NUM>% in wavelength ranges comprised between <NUM> and <NUM> (infrared light) and a transmission lower than <NUM>% in wavelength ranges comprised between <NUM> and <NUM> (visible light). The infrared coating <NUM> is for example made of ink, paint, or plastic material such as polycarbonate, polymethylmethacrylate or polyamide.

The infrared coating <NUM> extends on the layer <NUM> at the opposite side from the window <NUM>. The infrared coating <NUM> extends similarly to the layer <NUM>. However, the infrared coating <NUM> also specifically extends in front of the first opening <NUM>. Consequently, the infrared coating <NUM> prevents the light source <NUM> from being seen from the cabin.

As shown in <FIG>, on top of the infrared coating <NUM> (in the direction of the scene), the cover <NUM> comprises a transparent film <NUM>. The transparent film <NUM> is here made of a transparent polycarbonate. The transparent film <NUM> protects the other elements of the cover <NUM> and, in particular, the infrared coating <NUM> and the layer <NUM>, for example against scratches. The transparent film <NUM> also ensures that the external surface of the cover <NUM> is smooth. In other words, the transparent film <NUM> also has an aesthetic purpose. Here, the transparent film <NUM> is thinner than the window <NUM>.

Optionality, the cover <NUM> may also comprises several materials (not represented) coated on the transparent film <NUM> such as anti-starch or anti-reflection varnishes or varnishes to protect against ultraviolet light.

The cover <NUM> according to the invention is here fabricated thanks to a multi-material injection molding process.

In a first step, the transparent film <NUM> is molded.

In a second step, the layer <NUM> and the infrared coating <NUM> are successively deposited onto the transparent film <NUM>. Here, the layer <NUM> and the infrared coating <NUM> are each preferentially made of an ink which is deposited by a film insert molding process. This means that the layer <NUM> and the infrared coating are formed directly on the transparent film <NUM>. As a variant, the layer and the infrared coating could be coated.

Then, in a third step the window <NUM> and the frame <NUM> are successively overmolded onto the assembly made of the transparent film <NUM>, the infrared coating <NUM> and the layer <NUM>. Firstly, said assembly is overmolded with the window <NUM>, which means that the window <NUM> is injected under high pressure onto said assembly. Secondly, the new assembly made of the transparent film <NUM>, the infrared coating <NUM> and the layer <NUM> and the window <NUM> is overmolded with the frame <NUM>, which means that the frame <NUM> is injected under high pressure onto said new assembly. The frame <NUM> and the window <NUM> are therefore molded in contact with each other.

Thanks to this multi-material injection molding process, the frame <NUM> and the window <NUM> are chemically bonded to each other, which results in a very efficient optical interface. In consequence of this efficient optical interface, infrared light propagating in the window <NUM> is efficiently transmitted to the frame <NUM>, in particular to the separator <NUM>, when reflecting on the back surface <NUM>. The optical interface is even more efficient than, here, the frame <NUM> and the window <NUM> are made of similar materials: polycarbonates only distinct in colors.

Efficient optical interfaces are also produced between the window <NUM>, the layer <NUM>, the infrared coating <NUM> and the transparent film <NUM>, thus, the transmission of infrared light between them is improved.

As a variant and as a comparison, the frame and the window could be molded separately and fixed together. The interface between the frame and the window would then comprise air or glue which reduces the quantity of infrared light transmitted from the window to the frame as compared with the above-described efficient optical interface.

Claim 1:
Illuminating and imaging system (<NUM>) comprising:
- an infrared light source (<NUM>);
- an image capture apparatus (<NUM>); and
- a cover (<NUM>) comprising:
- a window (<NUM>) designed to extend over the infrared light source (<NUM>) and the image capture apparatus (<NUM>); and
- a separator (<NUM>),
the window (<NUM>) comprising a back surface (<NUM>) in contact with the separator (<NUM>) and a front surface (<NUM>) opposite to the back surface (<NUM>), the separator (<NUM>) being positioned with respect to the window (<NUM>) in such manner as to be interposed between the light source (<NUM>) and the image capture apparatus (<NUM>) to prevent direct illumination of the image capture apparatus (<NUM>) by the light source (<NUM>),
said cover (<NUM>) comprises a layer (<NUM>) adapted to absorb infrared light, the layer (<NUM>) extending on the front surface (<NUM>) of the window (<NUM>) such as to face at least partly the separator (<NUM>), characterized in that
- said illuminating and imaging system is adapted to be placed inside an automotive vehicle; and
- said cover (<NUM>) further comprises an infrared coating (<NUM>) adapted to absorb visible light and to transmit infrared light, the infrared coating (<NUM>) extending in front of the front surface (<NUM>) of the window (<NUM>) in such manner as to face the infrared light source (<NUM>).