Patent Description:
Such a device for acquiring images inside a vehicle can be designed as an integrated component, i.e. it has to be integrated into the installation space of the vehicle, e.g. into the dashboard or the roof. The installation space of vehicles is usually very limited so that there is a need for a device for acquiring images inside a vehicle with a compact design.

The article "<NPL> discloses a device for acquiring images inside a vehicle for gesture recognition with an illuminator to illuminate a field of view, an image sensor that is arranged to acquire images from the field of view, and an optical element.

<CIT> relates to systems and methods for optical detection of the position and movements of the fingers of the driver of a motor vehicle. The system comprises an infrared light source and an optical matrix sensor to detect the light reflected by the driver's fingers.

<CIT> discloses a biometric authentication apparatus with an illumination light-emitting element, a biometric-authentication-oriented imaging apparatus, a light guide body and a light blocking body.

<CIT> also discloses a biometric authentication apparatus having a light-emitting device, an image sensor, a light-guide member and a hood that prevents light leaked from the light guide member from entering into an optical unit.

<CIT>, <CIT>, and <CIT> disclose a device according to the preamble of claim <NUM>.

It is an object of the invention to provide a device for acquiring images inside a vehicle with a compact design and good NVH characteristics.

The object is satisfied by a device for acquiring images inside a vehicle according to claim <NUM>.

The device of the invention comprises an illuminator to illuminate a field of view. The field of view is usually defined as a space where the driver's head is located when he or she is driving the vehicle. The device further comprises an image sensor that is arranged to acquire images from the field of view. If the field of view is defined as a space in which the driver's head is located, the image sensor can acquire images from the drivers head. Further, the device comprises an optical element having a light-transparent portion and a light-blocking portion, wherein the light-transparent portion is arranged so that light of the illuminator being emitted to the field of view passes through the light-transparent portion, and wherein the light-blocking portion is arranged to block light of the illuminator being emitted in a direction towards the image sensor. The light-transparent portion and/or the light-blocking portion comprise/comprises an elastic material.

One general idea of the invention is to provide one optical element that has different optical properties in different portions. This optical element is one single prefabricated part, for example manufactured by a multicomponent injection molding process.

The optical element according to the invention has two separate functions: letting light of the illuminator pass through its light-transparent portion to the field of view and blocking light of the illuminator travelling to the sensor to avoid so called light leaks.

In the present teaching, the light emitted by the illuminator may generally be visible to the human eye, but preferably comprises or essentially consists of light that is not visible to the human eye, for example electromagnetic radiation in the form of infrared light.

Advantageous embodiments of the device for acquiring images inside a vehicle can be taken from the following description, the dependent claims and the drawings.

In accordance with an embodiment, the light-transparent portion forms at least one lens. The light-transparent portion can form precisely one lens. Alternatively, the light-transparent portion can form more than one lens. This has the advantage that the optical element can be used to modify the illumination of the field of view. The illumination should generally be modified to be uniform throughout the field of view and the least possible outside the field of view.

In the present teaching, the term light-transparent generally means, that at least light of a certain wavelength-range can pass through the material.

According to one aspect, the light-transparent portion is configured to not block any light, i.e. let light of any wavelength pass through itself. Alternatively, the light-transparent portion is configured to only let light of a certain wavelength-range pass through. In one embodiment, the light-transparent portion is configured to essentially only let infrared light pass through. This has the advantage that a so called red glow effect is minimized.

In another aspect, the light-transparent portion is configured to at least let infrared light pass through, i.e. the part is infrared-light transparent. Therefore, infrared light can be used to illuminate the field of view.

According to a further aspect, the illuminator is arranged to emit light in an infrared-range wavelength. The illuminator can be arranged to emit light near-infrared light, in particular in a range from <NUM> to <NUM>. The advantage of using light in the infrared-range wavelength to illuminate the field of view is that the driver cannot see the light and thus is not dazzled by the light.

In an aspect of the invention, the illuminator comprises at least one laser and/or at least one light emitting diode. The illuminator can comprise precisely one laser or one LED. Alternatively, the illuminator can comprise multiple lasers or LEDs which particularly can be arranged in a matrix.

The at least one LED of the illuminator can be an SMD LED or a chip on board LED. The at least one laser can be a vertical-cavity surface-emitting laser (VCSEL).

According to an aspect, the illuminator comprises a light source that is encapsulated by the light-transparent portion. The term "encapsulated by the light-transparent portion" means that the light-transparent portion encompasses the light source so that the light source is sealed either completely by the light-transparent portion or by the light transparent portion in combination with other parts of the device.

According to another embodiment, the device does not comprise a separate reflector part. For example, the light-transparent portion can have a reflective coating that renders a separate reflector part unnecessary. The advantage of not having a separate reflector part is that the device can be made in a particularly compact design.

In order to improve the illumination of the field of view, an LED with a built-in lens can be used. In addition, the light-transparent portion can be formed as a lens. In one embodiment, the built-in lens and the lens formed by the light-transparent portion are optically connected in series so that the light of the illuminator passes both lenses. This helps to provide an even illumination of the field of view.

The light source can comprise at least one LED and/or at least one laser that are fixed to a printed circuit board (PCB). The PCB and the light-transparent portion can enclose the light source to seal the light source. In order to avoid losing the sealing properties over the product life-cycle the light-transparent portion can be fixedly connected to the printed circuit board, e.g. glued to the printed circuit board. This also limits noise caused by vibrations of the PCB.

According to one embodiment, the light-transparent portion comprises, in particular is made of, an elastic material. Alternatively the light-blocking portion can comprise, in particular can be made of, an elastic material. Preferably, both the light-transparent portion and the light-blocking portion both comprise, in particular are both made of, an elastic material. Using an elastic material for the light-transparent portion and/or the light-blocking portion helps to avoid noise in the device and additionally helps to improve sealing of the device.

Alternatively, the light-transparent portion and the light-blocking portion can be made of an inelastic material such as a thermoplastic material.

According to one aspect, the light-transparent portion comprises silicon rubber and particularly consists of silicon rubber. Alternatively, the light-blocking portion can comprise silicon rubber and particularly consist of silicon rubber. In a preferred embodiment, the light-transparent portion and the light-blocking portion both comprise silicon rubber. Preferably, both the light-transparent portion and the light-blocking portion consist of silicon rubber. Silicon rubber can be used to manufacture complex geometries and has good damping and sealing properties. Therefore, it is well suited for manufacturing the light-transparent portion and/or the light-blocking portion.

According to one aspect, the light-transparent portion comprises a convex surface facing a light source of the illuminator. According to another aspect, the light-transparent portion defines an inner space having an undercut, i.e. the light-transparent portion defines a space with an inner circumference that increases towards the inside. In particular, the light-transparent portion is formed to comprise an opening with an inner circumference that is smaller than the inner circumference of the adjacent space inside the portion.

In another aspect, the surface of the light-transparent portion is at least partially coated. In particular, the coating can be an anti-reflective coating. The anti-reflective coating can be placed on the surface that faces towards the light source and/or the field of view. Alternatively or additionally the coating can comprise a reflective coating. The reflective coating can be used to replace a reflector part as mentioned before. In this case, the reflective coating can be placed on side-surfaces of the light-transparent portion, i.e. the surfaces that do not face towards the light source or the field of view. As an example, the reflective coating can comprise metal.

In one aspect, the light-transparent portion has a light-entering surface with diffusing properties, a light-exiting surface with diffusing properties and/or comprises a material having light diffusing properties.

According to another aspect, the light-transparent portion comprises microlenses and/or a structure is formed on the surface of the light-transparent portion.

Examples of a structure on the surface of the light-transparent portion can be refractive microlenses, beam homogenizers, and collimators. Such a structure can be placed on the surface that faces towards the light source and/or the surface that faces the field of view. The structure can also be placed inside the body of the light-transparent portion.

In one embodiment, the illuminator comprises a reflector that is provided to deflect the light of a light source in the direction of the field of view. In particular, the reflector abuts the light-transparent portion and/or the light-blocking portion. The reflector can even be fixedly connected to the light-transparent portion and/or the light-blocking portion. When the reflector abuts the light-transparent portion or the light-blocking portion, vibrations of the reflector initiated by frequent illumination causing noise are being eliminated. This is especially the case when the light-transparent portion and/or the light-blocking portion are made from an elastic material such as silicon rubber.

The reflector can be at least partially made from a metallic or metalized material. For example, the reflector can be made from a material comprising copper and/or aluminum.

According to an embodiment, the reflector and the light-blocking portion abut or touch each other to form a sealing surface. This helps sealing the inside of the reflector. In particular the sealing surface between the reflector and the light-blocking portion extends along a closed shape, e.g. a closed circle or a square.

To improve sealing of the inside of the reflector, the reflector and the light-transparent portion can abut each other to form a sealing surface. Particularly, the sealing surface between the reflector and the light-transparent portion can extend along a closed shape.

The illuminator can comprise a printed circuit board. In this case, in order to improve sealing between the printed circuit board and the light-transparent portion, the light-transparent portion and the printed circuit board can abut or touch each other to form a sealing surface. It can be favorable if the sealing surface between the light-transparent portion and the printed circuit board extends along a closed shape.

According to another aspect, a cover is provided at the front face of the device. The cover is impermeable to visible light, i.e. it is configured to filter at least a majority of the visible light that would otherwise enter or exit the device. Thus, the cover may appear black or dark colored to a person.

In a further embodiment, the light-blocking portion and the cover abut each other to form a sealing surface. Also the sealing surface between the light-blocking portion and the cover can extend along a closed shape, e.g. a square or a circle. In particular, a sealing lip can be formed on the light-blocking portion that is in contact with the cover. A second sealing lip can be formed on the light-blocking portion that is in contact with a housing of the device.

According to another aspect, the light-blocking portion forms a frame through which the light of the light source emits light to the field of view. Therefore, the light-blocking portion forms an opening though which the light passes into the field of view. The light-blocking portion thus is used to define a shape of the light beam of the illuminator. Additionally or alternatively, the light-blocking portion and the light-transparent portion can form a connection zone, i.e. a connecting surface where the two parts are connected to each other, that extends along a closed shape.

The features and advantages of the various embodiments of the present invention will, in the following, be described with reference to the figures.

<FIG> depict embodiments according to the invention. The same or corresponding components are labeled with the same reference signs to simplify comparison of the several embodiments.

<FIG> depicts a device <NUM> for acquiring images inside a vehicle, in particular for gesture recognition and/or fatigue detection. The device <NUM> can be integrated into a dashboard or a roof of a vehicle (not shown). The device <NUM> for acquiring images inside a vehicle comprises two illuminators <NUM> to illuminate a field of view <NUM>, an image sensor <NUM> that is arranged to acquire images from the field of view <NUM>, and an optical element <NUM> having light-transparent portions 18a and light-blocking portions 18b. The light-transparent portions 18a are arranged so that light of the illuminator <NUM> being emitted to the field of view <NUM> passes through the light-transparent portions 18a. The light-blocking portions 18b are arranged to block light of the illuminator <NUM> being emitted in a direction towards the image sensor <NUM> to avoid so called light leaks.

In the embodiment of <FIG>, the illuminators <NUM> each comprise a light source <NUM> being a light emitting diode (LED) that is fixedly connected to a printed circuit board (PCB) <NUM>. The illuminators <NUM> further comprise a reflector <NUM> that is provided to deflect the light of the light source <NUM> in the direction of the field of view <NUM>. The reflectors <NUM> are connected to the PCB <NUM> in a way that a sealing surface is established between the reflectors <NUM> and the PCBs <NUM>. For example, the PCBs <NUM> and/or the reflectors <NUM> can be coated with an elastic material so that the surface between each reflector <NUM> and the corresponding PCB <NUM> is sealed properly.

The reflectors <NUM> each comprise at least one inner reflecting surface 24a that defines an inner space <NUM>. This space <NUM> is occupied by the light-transparent portions 18a of the optical element <NUM>. As shown in <FIG>, the inner circumference of the reflecting surface 24a increases towards the end opposite the light source <NUM>. Similarly, the outer circumference of the light-transparent portion 18a of the optical element increases along the general direction the light travels from the light source <NUM> to the field of view <NUM>.

The light sources <NUM> are encapsulated by the light-transparent portions 18a so that the light sources <NUM> are sealed. In the embodiment of <FIG>, the light-transparent portions 18a each abut the respective PCB <NUM> along a closed shape around the light source <NUM>. Since the light-transparent portions 18a are made from an elastic material such as silicon rubber, sealing of the light sources <NUM> is improved.

Each reflector <NUM> is positioned around one of the light sources <NUM>. At a distal end from the light source <NUM>, the reflector <NUM> abuts the light-blocking portion 18b of the optical element <NUM>. The reflector <NUM> and the light-blocking portion 18b together form a shield so that light emitted by the illuminator <NUM> does not directly shine towards the image sensor <NUM>. Therefore, the reflector <NUM> and the light-blocking portion 18b are arranged to block light of the illuminator <NUM> being emitted in a direction towards the image sensor <NUM> to avoid so called light leaks.

At the side facing the field of view <NUM>, i.e. the front face, the device <NUM> is equipped with a cover <NUM>. The cover <NUM> is impermeable to visible light and thus appears as a black or dark surface to a driver. The light-blocking portion 18b abuts the cover <NUM> so that a sealing surface is established.

When the light sources <NUM> emit infrared light, it passes through the light-transparent portion 18a and through the cover <NUM> into the field of view <NUM>. The infrared light is reflected by an object placed in the field of view <NUM>, such as the head of a driver, and is then detected by the image sensor <NUM>. On the other hand, light that does not exit the device <NUM> and would be detected by the image sensor <NUM> is blocked by the light-blocking portion 18b.

In <FIG>, an optical element <NUM> for four light-sources <NUM> is depicted. The optical element <NUM> comprises two light-transparent portions 18a and a light-blocking portion 18b connecting the two light-transparent portions 18a. Each light-transparent portion 18a is configured to receive a pair of light-sources <NUM>. The light-blocking portion 18b forms three frames <NUM>, <NUM>, <NUM>, one frame <NUM> for the first pair of light-sources <NUM>, one frame <NUM> for the second pair of light-sources <NUM>, and one frame <NUM> between the frames <NUM>, <NUM> for the image sensor <NUM>. Therefore, the light sources <NUM> can be arranged on at least two sides of the image sensor <NUM>.

<FIG> depicts a third embodiment. This embodiment does not need a separate reflector part. The light-transparent portion 18a encompasses the light source <NUM> and is connected to the PCB <NUM> along a closed shape to seal the light source <NUM>. The light-blocking portion 18b extends from the PCB <NUM> to the cover <NUM> in order to block light emitted from the light source <NUM> that would otherwise radiate directly into the image sensor <NUM> and therefore cause light leaks.

The light-transparent portion 18a forms a convex surface on the side where the light exits the light-transparent portion 18a. Thus, the light-transparent portion 18a forms a lens <NUM> in order to better define the illumination of the field of view <NUM>. A peripheral surface <NUM> of the light-transparent portion 18a or a peripheral surface <NUM> of the light-blocking portion 18b can be coated with a reflective coating to better define illumination of the field of view <NUM>.

The light-transparent portion 18a and the light-blocking portion 18b both abut the PCB <NUM> and the cover <NUM> to buffer vibrations of the PCB <NUM> and/or the cover <NUM>. The light-transparent portion 18a and/or the light-blocking portion 18b can be fixed to the PCB <NUM> and/or the cover <NUM> to make sure that vibrations are buffered continuously.

<FIG> depicts a fourth embodiment. It varies from the embodiment of <FIG> in that the light source <NUM> is a SMD (surface mounted device) LED with an integrated reflector. SMD LEDs have a longer technical lifetime and are brighter than regular LEDs.

<FIG> shows a SMD LED as used in the fourth embodiment of <FIG>. The SMD LED comprises a heatsink <NUM> having a reflective surface 38a mounted on the printed circuit board <NUM>. A bonding wire <NUM> connects the PCB <NUM> with a semiconductor crystal <NUM> that is covered by a phosphorus layer <NUM>. The SMD LED can have an integrated lens <NUM> as shown in <FIG>. Alternatively, the SMD LED does not have an integrated lens, e.g. the SMD LED is a flat LED.

<FIG> depicts a fifth embodiment. It varies from the embodiments of <FIG> and <FIG> in that the light source <NUM> is a COB (chip on board) LED without reflector. COB LEDs can be built in a compact design and are very reliable. In this embodiment, the light-transparent portion 18a does not form a lens but instead lies flat on the cover <NUM>.

<FIG> shows a COB LED as used in the fifth embodiment of <FIG>. The COB LED comprises a semiconductor crystal <NUM> that is mounted, e.g. glued, on a printed circuit board <NUM>. The PCB <NUM> is also used for cooling of the LED. Two bonding wires <NUM>, <NUM> connect the semiconductor crystal <NUM> to the PCB <NUM>. The semiconductor crystal <NUM> is covered by a phosphorus layer <NUM>. Then, the semiconductor crystal <NUM> with the phosphorus layer <NUM> and the two bonding wires <NUM>, <NUM> are covered by a lens <NUM> that can be made from epoxide resin.

<FIG> depicts a sixth embodiment with a special form of the light-transparent portion 18a. The light-transparent portion 18a forms a cavity <NUM> with an opening <NUM> and defines a space <NUM> that is partly occupied by the light source <NUM>, e.g. a SMD LED or a COB LED. The cavity's inner circumference, the measured distance once around the inner surface at a given height, varies in that it becomes larger at a height that is further away from the light source <NUM>. Therefore, the cavity <NUM> defines an undercut <NUM> with respect to the opening <NUM>. In the cavity <NUM>, on the side facing the light source <NUM>, the light-transparent portion 18a has a convex surface <NUM>. Thus, the light-transparent portion 18a forms a lens <NUM>. In the opposite direction facing away from the light source <NUM>, the light-transparent portion 18a has a surface that is flat and lies flat against the cover <NUM>.

<FIG> depicts a light-transparent portion 18a according to a seventh embodiment. This embodiment is similar to the light-transparent portion 18a of <FIG> with some exceptions that are explained in the following. The light-transparent portion 18a of <FIG> does not abut the PCB <NUM>. A second, independent difference is that the light-transparent portion 18a has a surface facing away from the light source <NUM> that is convex and thus forms a lens <NUM>.

<FIG> depicts a device <NUM> according to an eighth embodiment. The device <NUM> for acquiring images inside a vehicle comprises multiple LEDs <NUM> to illuminate the field of view <NUM>, an image sensor <NUM> that is arranged to acquire images from the field of view <NUM>, and an optical element <NUM> having a light-transparent portion 18a and a light-blocking portion 18b. The light-transparent portion 18a is arranged so that light of the LEDs <NUM> being emitted to the field of view <NUM> passes through the light-transparent portion 18a. The light-blocking portion 18b is arranged between the LEDs <NUM> and the image sensor <NUM> to block light of the LEDs <NUM> being emitted in a direction towards the image sensor <NUM> to avoid so called light leaks.

In the embodiment of <FIG>, the multiple LEDs <NUM> are all fixedly connected to one printed circuit board (PCB) <NUM>. A reflector <NUM> is provided to reflect the light of the LEDs <NUM> in the direction of the field of view <NUM>. The reflector <NUM> is connected, e.g. glued, to the PCB <NUM> in a way that a sealing surface is established between the reflector <NUM> and the PCB <NUM>. Alternatively, the PCB <NUM> and/or the reflector <NUM> can be coated with an elastic material so that the surface between reflector <NUM> and the PCB <NUM> is sealed properly. Furthermore, the light-transparent portion 18a, which is made from an elastic material such as silicon rubber, abuts the PCB <NUM> to damp vibrations of the PCB <NUM>.

The reflector <NUM> is positioned around the light-transparent portion 18a and comprises an inner reflecting surface 24a that faces towards the light-transparent portion 18a. As shown in <FIG>, the inner circumference of the reflecting surface 24a increases in a first sector <NUM> and then stays constant in a second sector <NUM>. Similarly, the outer circumference of the light-transparent portion 18a of the optical element <NUM> increases in the first sector <NUM> and stays constant in the second sector <NUM>. As can be seen in <FIG>, the first sector <NUM> is closer to the light source <NUM> than the second sector <NUM>.

The LEDs <NUM> are encapsulated by the light-transparent portion 18a so that each LED <NUM> is sealed. To do so, the light-transparent portion 18a abuts the PCB <NUM> along a closed shape around each LED <NUM>. Since the light-transparent portion 18a is made from an elastic material such as silicon rubber, sealing of each LED <NUM> is ensured.

In order to avoid vibrations of the reflector <NUM> to cause noise, the light-transparent portion 18a abuts the reflector <NUM> and therefore damps vibrations of the reflector <NUM>. Therefore, vibrations of the reflector <NUM> due to vibrations of the PCB <NUM> or due to the photomechanical effect are successfully avoided.

The reflector <NUM> and the light-blocking portion 18b together form a shield so that light emitted by the LEDs <NUM> does not directly reach the image sensor <NUM>, i.e. so that light emitted by the LEDs <NUM> does not reach the image sensor <NUM> without leaving the device. In other words, the reflector <NUM> and the light-blocking portion 18b are arranged to block light of the illuminator <NUM> being emitted in a direction towards the image sensor <NUM> to avoid so called light leaks.

At the side facing the field of view, the device <NUM> according to the embodiment of <FIG> is also equipped with a cover <NUM> forming the face side of the device. The cover <NUM> is impermeable to visible light and thus appears as a black or dark surface to the driver. The light-blocking portion 18b forms a flexible sealing lip <NUM> that is in contact with the cover <NUM> so that a sealing surface is established. The light-blocking portion 18b also forms a second flexible sealing lip <NUM> that is in contact with a housing <NUM> of the device <NUM> so that a second sealing surface is established.

As explained before, infrared light that is emitted from the LEDs <NUM> can radiate through the light-transparent portion 18a and through the cover <NUM> into the field of view <NUM>. The infrared light is reflected by an object placed in the field of view <NUM>, such as the head of a driver and is then detected by the image sensor <NUM>. On the other hand, light that stays inside the device <NUM> and would usually be detected by the image sensor <NUM> is blocked by the light-blocking portion 18b.

As can be seen from <FIG>, the light-transparent portion 18a forms a lens <NUM> on a side of the light-transparent portion 18a that faces away from the light sources <NUM>. The lens <NUM> is located in the second sector <NUM> of the light-transparent portion 18a.

In <FIG>, it can be seen that the light-blocking portion 18b forms multiple rectangular frames <NUM>, <NUM>, <NUM> that each define an opening for light to shine into the field of view <NUM>. The light-blocking portion 18b also forms a circular frame <NUM> so that light can pass through to the image sensor <NUM>.

<FIG> shows the optical element <NUM> with the light-transparent portion 18a and the light-blocking portion 18b. As can be seen from this figure, the light-transparent portions 18a each have a rectangular outer form in line with the form of the frames <NUM>, <NUM>, and <NUM>.

Claim 1:
Device (<NUM>) for acquiring images inside a vehicle, comprising
an illuminator (<NUM>) to illuminate a field of view (<NUM>),
an image sensor (<NUM>) that is arranged to acquire images from the field of view (<NUM>), and
an optical element (<NUM>),
wherein the optical element (<NUM>) has a light-transparent portion (18a) and a light-blocking portion (18b), wherein the light-transparent portion (18a) is arranged so that light of the illuminator (<NUM>) being emitted to the field of view (<NUM>) passes through the light-transparent portion (18a), and wherein the light-blocking portion (18b) is arranged to block light of the illuminator (<NUM>) being emitted in a direction towards the image sensor (<NUM>)
characterized in that
the light-transparent portion (18a) and
the light-blocking portion (18b) comprise an elastic material to improve sealing of the device.