EP4315822A1

EP4315822A1 - An imaging device for a driver monitoring system

Info

Publication number: EP4315822A1
Application number: EP21847474.0A
Authority: EP
Inventors: Kah Soon Ang; Weiquan CONG
Original assignee: Continental Automotive Technologies GmbH
Current assignee: Aumovio Germany GmbH
Priority date: 2021-03-31
Filing date: 2021-12-23
Publication date: 2024-02-07
Also published as: GB202104603D0; WO2022207140A1; GB2605768A; CN117121496A

Abstract

Present disclosure discloses an imaging device for a driver monitoring system. The imaging device includes a lens stack and a beam splitter positioned and arranged along a primary optical axis. A portion of the beam splitter is coated with a dichroic coating. The dichroic coating reflects a first predetermined spectrum of light along a secondary optical axis and allow a second predetermined spectrum of light pass through the beam splitter along the primary optical axis. Further, the imaging device includes a first imaging sensor configured to receive the second predetermined spectrum of light and, a second imaging sensor configured to receive the first predetermined spectrum of light. The configuration of the imaging device aids in capturing images of the driver in different spectrums, thereby facilitating in effective monitoring of conditions of the vehicle.

Description

AN IMAGING DEVICE FOR A DRIVER MONITORING SYSTEM

TECHNICAL FIELD

Present invention relates in general to a field of automobiles. Particularly, although not exclusively, the present invention relates to an imaging device for a vehicle. Further embodiments of the present disclosure disclose the imaging device for a driver monitoring system of the vehicle.

BACKGROUND

Vehicles, such as passenger vehicles and commercial vehicles are typically operated and controlled by drivers. Through training and with experience, driver may learn how to drive a vehicle safely and efficiently in a range of conditions. For example, as driver gains experience, he may become adept at driving in challenging conditions such as rough terrain, rain, snow, darkness, and the like.

Drivers may sometime drive unsafely or inefficiently. Unsafe driving behavior may endanger the driver and may also damage the vehicle. Unsafe driving behaviors may also lead to fines, accidents, which may cause physical harm, and which may, in turn, lead to an increase in insurance rates for operating a vehicle. Inefficient driving, which may include hard accelerations, may increase the costs associated with operating a vehicle.Also, in certain scenarios, drivers may lack focus on the road due to distractions such as gadgets, and also due to drowsiness. Such lack of focus may lead to unsafe driving causing danger to the driver and the vehicle. Globally, automotive industry has been utilizing cameras for monitoring both exterior and interior of the vehicle for many years. One particular application is the use of camera to monitor the condition of a passenger compartment or cabin of a passenger vehicle. The camera may be used to monitor driving behavior of the driver or user. Driver monitoring may be done in real-time to determine condition of driver.

One of the challenges in the driver monitoring system is the quality of images captured by the camera in the passenger compartment. Poor quality of images captured by the camera leads to poor analyzation of the condition of the driver, which is undesired. Conventionally, a plurality of cameras have been adapted to capture images in different spectrum, since quality of image depends on the spectrum in which the image is captured. However, adapting the plurality of cameras is a complex arrangement as it poses space constrains in the passenger compartment, since the camera has to be strategically positioned to get a field of view of subject's facial features. In addition, positioning the camera in an optimal location to capture images of a driver within a motor vehicle is often challenging, due to space constrains in the cockpit area.

Hence, there is a need for a single camera to capture high quality images to facilitate effective monitoring of the condition of the driver.

The present disclosure has been devised in the light of the above considerations. SUMMARY

One or more shortcomings of the conventional devices and systems are overcome, and additional advantages are provided through the provision of the assembly and system as claimed in the present disclosure.

Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure.

In one non-limiting embodiment of the disclosure, an imaging device for a driver monitoring system of a vehicle is disclosed. The imaging device includes a lens stack comprising a plurality of lenses stacked along a primary optical axis. Each of the plurality of lenses is configured to receive light rays captured within a field of view of the imaging device.Further, the imaging device includes a beam splitter positioned behind the lens stack and along the primary optical axis.A portion of the beam splitter is coated with a dichroic coating to reflect a first predetermined spectrum of light from the received light rays along a secondary optical axis and allow a second predetermined spectrum of light from the received light rays along the primary optical axis. Furthermore, the imaging device includes a first imaging sensor and a second imaging sensor. The first imaging sensor is positioned in the primary optical axis and is configured to receive the second predetermined spectrum of light. The second imaging sensor positioned in the secondary optical axis and is configured to receive the first predetermined spectrum of the light. Advantageously, this aspect of the disclosure yields an imaging device which is operable to capture images in at least two predetermined spectrum of light through the same lens stack. In an embodiment of the disclosure, wherein the beam splitter is a cube beam splitter comprises a first prism and a second prism bonded to each other along a hypotenuse side.The hypotenuse side is coated with a dichroic coating. Advantageously, this aspect of the disclosure yields a compact imaging device, thus saving space.

In an embodiment of the disclosure, the first prism and the second prism are optically bonded to each other through an optically transparent glue, and a portion of the first prism and the second prism are coated with an anti-reflection coating. Advantageously, this aspect of the disclosure improves the sharpness and brightness of an image that is focused by the lens stack.

In an embodiment of the disclosure, the first predetermined spectrum of light is an infrared spectrum, and the second predetermined spectrum of light is a visible spectrum. Advantageously, this aspect of the disclosure yields an imaging device which is operable to capture images in a near infrared (NIR), through the same lens stack.

In an embodiment of the disclosure, the first imaging sensor is parallelly positioned in the primary optical axis and the second imaging sensor is positioned in the second optical axis perpendicular to the primary optical axis. Advantageous, this aspect of the disclosure yields an imaging device that is compact in size.

In an embodiment of the disclosure, the first imaging sensor and the second imaging sensor are communicatively coupled a printed circuit board.Advantageous, this aspect of the disclosure yields an imaging device with different image sensors, which can be selected according to priority.

In another non-limiting embodiment of the disclosure, a driver monitoring system for a vehicle is disclosed.The system includes an imaging device arranged in an instrument cluster of the vehicle for monitoring the driver. The imaging device includes a lens stack comprising a plurality of lenses stacked along a primary optical axis. Each of the plurality of lenses is configured to receive light rays captured within a field of view of the imaging device. Further, the imaging device includes a beam splitter positioned behind the lens stack and along the primary optical axis. A portion of the beam splitter is coated with a dichroic coating to reflect a first predetermined spectrum of light from the received light rays along a secondary optical axis and allow a second predetermined spectrum of light from the received light rays along the primary optical axis. Furthermore, the imaging device includes a first imaging sensor and a second imaging sensor. The first imaging sensor is positioned in the primary optical axis and is configured to receive the second predetermined spectrum of light. The second imaging sensor positioned in the secondary optical axis and is configured to receive the first predetermined spectrum of the light. Further, the driver monitoring system includes a computing unit, communicatively coupled to the first imaging sensor and the second imaging sensor. The computing unit is configured to determine condition of the driver, based on images captured by the imaging device.Advantageously, this aspect of the disclosure yields an imaging device which is operable to capture images in at least two predetermined spectrum of light through the same lens stack. BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES

The novel features and characteristic of the disclosure are set forth in the appended claims. The disclosure itself, however, as well as a preferred mode of use, further objectives, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which:

Fig . 1 shows a side view of an instrument cluster employed with an imaging device, in accordance with an embodiment of the present disclosure.

Fig . 2 shows a sectional view of an imaging device, according to an embodiment of the present disclosure.

Fig . 3 shows a sectional view of a beam splitter employed in the imaging device of Fig . 2 , according to an embodiment of the present disclosure.

Fig . 4 shows an operating condition of the imaging device of Fig .

2.

The figure depicts embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the method for controlling the temperature of the vehicle cabin without departing from the principles of the disclosure described herein. DETAILED DESCRIPTION

The foregoing has broadly outlined the features and technical advantages of the present disclosure in order that the description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other system for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the disclosure. The novel features which are believed to be characteristic of the disclosure, as to its organization, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.

In the present document, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

While the disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described below. It should be understood, however that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure.

The terms "comprises.... a", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a system that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such mechanism. In other words, one or more elements in the system or steps of method proceeded by "comprises...a" does not, without more constraints, preclude the existence of other elements or additional elements in the device.

It is to be noted that a person skilled in the art would be motivated from the present disclosure and modify various features of device and system, without departing from the scope of the disclosure. Therefore, such modifications are considered to be part of the disclosure.Accordingly, the drawings show only those specific details that are pertinent to understand the embodiments of the present disclosure, so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skilled in the art having benefit of the description herein.Also, the device and system of the present disclosure may be employed in any kind of vehicles including commercial vehicles, passenger vehicles, and the like. However, complete vehicle is not illustrated in the drawings of the disclosure is for the purpose of simplicity.

The term "monitoring system" used hereinafter in the present disclosure refers to a real-time system that collects observable information about driver and test their ability to perform the dynamic driving task in a safe manner. The term "primary optical axis" used in the present disclosure refers to an imaginary line passing through the center of curvature of the plurality of lenses and the term "secondary optical axis" used in the present disclosure refers to the imaginary line perpendicular to the center of curvature or the primary optical axis.Further, the term "reflection" refers to change in direction of light waves at interference. The following detailed description is merely exemplary in nature and is not intended to limit application and uses. Furthermore, there is no intention to be bound by any theory presented in the preceding background or summary or the following detailed description. It is to be understood that the disclosure may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices or components illustrated in the attached drawings and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions or other physical characteristics relating to the embodiments that may be disclosed are not to be considered as limiting, unless the claims expressly state otherwise.

The term "optically transparent glue" refers to a bonding substance or adhesive having transparent properties, such that light rays is permissible to pass through the optically transparent glue, without appreciable scattering of light rays. When used for bonding optical elements such as glass, prisms or waveguides, the background of the optical elements may be observable and permits incident light rays to pass through, thus achieving see-through effect.

The term "first", "second", "third" and the like used in the context of this disclosure may refer to modification of different elements in accordance to various exemplary embodiments, but not limited thereto. The expressions may be used to distinguish one element from another element, regardless of sequence of importance. By way of an example, "a first prism" and "a second prism" may indicate different elements of the imaging device, regardless of order or importance. Similarly, a first prism may be referred to as the second prism and vice versa without departing from the scope of this disclosure.

Hereinafter, preferred embodiments of the present disclosure will be described referring to the accompanying drawings. While some specific terms of "upper," "lower," "below", "above", "front end" or "rear end", "behind" and other terms containing these specific terms and directed to a specific direction will be used, the purpose of usage of these terms or words is merely to facilitate understanding of the present invention referring to the drawings.Accordingly, it should be noted that the meanings of these terms or words should not improperly limit the technical scope of the present invention.

Fig . 1 illustrates a sectional side view of an instrument cluster (100) in a passenger cabin of a vehicle employed with an imaging device (1) for providing inputs to a driver monitoring system. Passenger cabin of the vehiclemay include a dashboard on driver's side and the instrument cluster (100) may be integrated to the dashboard [not shown in figures]. The instrument cluster (100) may be configured to display instantaneous condition values of the vehicle such as for example speed of the vehicle, real-time fuel level, engine speed, engine check light, engine temperature, engine oil level, Anti-lock braking system (ABS) check light and the like. The driver monitoring system may include an imaging device (1), which may be arranged in the instrument cluster (100) and a computing unit, communicatively coupled to the imaging device (1). In an embodiment, the imaging device (1) may be configured to capture images of the driver in different spectrums based on the requirement. The images captured by the imaging device (1) may be analysed by the computing unit to determine condition of the driver, during the vehicle operation. In some embodiments, the images captured by the imaging device (1) may be analysed in real time to control various operations of the vehicle such as driver alert systems, collision avoidance systems, and the like. In some other embodiments, the the images captured by the imaging device (1) may be analysed in offline to determine various parameters and behaviours of the driver.

The configuration of the imaging device (1) is explained hereinafter in the present disclosure. Fig. 2 illustrates a sectional view of the imaging device (1) of the present disclosure. The imaging device (1) may include a lens stack (2). The lens stack (2) may include a plurality of lenses (2b). Each of the plurality of lenses (2b) may be stacked along a primary optical axis (A-A)of the imaging device (1).In some embodiments, the lens stack (2) may include a cylindrical tube, and each of the plurality of lenses (2a) are arranged and supported one behind the other in the cylindrical tube. The plurality of lenses (2b) may be configured to receive light rays captured within a field of view [FOV] of the imaging device (1). The term "field of view" (FOV) or more in particular, "angle of view" (AOV) shall refer to an operational angle or space which the imaging device (1) may be sensitive to light rays or electromagnetic radiation, where the imaging device (1) may receive light rays or capture images. As apparent from Fig.2, the imaging device (1)may include a beam splitter (3), which may be positioned along the primary optical axis (A-A). Preferably, the beam splitter (3) is positioned behind the lens stack (2) and along the primary optical axis (A-A).

Referring to Fig . 3 , which illustrates a sectional view of the beam splitter (3). In an embodiment, the beam splitter (3) may be a cube beam splitter (3). The beam splitter (3) may include a first prism (4) and a second prism (5). The first prism (4) and the second prism (5)may be bonded to each other along a hypotenuse side by an optically transparent glue (10), forming an angle of 45 degrees at two diagonal corners. In an embodiment, the beam splitter (3) may be coated with a dichroic coating (12). That is, an hypotenuse side of one of the first prism (4) and the second prism (5) may be coated with the dichroic coating (12). The dichroic coating (12) may reflect a first predetermined spectrum of light from the received light rays along a secondary optical axis (B-B) and allow a second predetermined spectrum of light from the received light along the primary optical axis (A-A). In an embodiment, the first predetermined spectrum of light may be an infrared spectrum particularly a near infrared spectrum (NIR) of light and the second predetermined spectrum may be a visible spectrum. Further, a portion of the first prism (4) and the second prism (5) may be coated with an anti-reflection coating. In an embodiment, an entry surface (13) of the first prism (4) and exit surfaces (14a, 14b) of the first prism (4) and the second prism (5) may be coated with anti-reflection coating. Entry surface (13) of the first prism (4) may be a side of the first prism (4), which receives light from the lens stack (2) and exit surface (14a) may be another side of the first prism (4) from which light exits the first prism (4). The anti-reflection coating improve sharpness and brightness of the image that is focused by the lens stack (2) on to the beam splitter (3).

In an embodiment, the anti-reflection coating on surface 14a can be a single layer anti-reflection (SLAR) coating, as its design wavelength is narrow NIR spectral wavelength, e.g. but not limiting to 850nm or 940nm light.

In an embodiment, the anti-reflection coating on surface 14b can be broad bandwidth anti-reflection (BBAR) coating, as its design wavelength is wide visible spectral wavelength, not limiting to 400nm~680nm light.

In an embodiment, the anti-reflection coating on surface 13 can be broad bandwidth anti-reflection (BBAR) coating, as its design wavelength is wide visible spectral wavelength, not limiting to 400nm~680nm plus NIR spectral wavelength e.g. but not limiting to 850nm or 940nm light.

In an embodiment, the anti-reflection coating material's selection depends on refractive index of prism substrate material, follow destructive interference anti-reflection coating principle, to have the coating material's refractive index equal to the square root (SQRT) of the index of the prism substrate material. The anti-reflection coating material is Magnesium fluoride (MgF2), as it has relatively low refractive index. Also, the thickness of each coating layer is a function of the design wavelength, which follow the quarter wavelength principle.

Referring again to FIG. 2 , the imaging device (1) may include a first imaging sensor (6), which may be positioned in the primary optical axis [A-A]. In an embodiment, the first imaging sensor (6) may be positioned behind the beam splitter (3). The first imaging sensor (6) is configured to receive the second predetermined spectrum passing through the beam splitter (3) along the primary optical axis (A-A).Further, the imaging device (1) may include a second imaging sensor (7), which may be positioned in the secondary optical axis (B-B). In an embodiment, the second imaging sensor (7) may be positioned parallel to the beam splitter (3) and perpendicular to the primary optical axis (A-A). The second imaging sensor (7)may be configured to receive the first predetermined spectrum, that is reflected from the beam splitter (3) along the secondary optical axis (B-B).As apparent from FIG . 2 , the first imaging sensor (6) and the second imaging sensor (7) may be communicatively coupled to corresponding printed circuit boards (PCB) (8a, 8b).In an embodiment, the first imaging sensor (6) and the second imaging sensor (7) may be directly mounted on the corresponding PCB's, and the printed circuit boards (PCB) (8a, 8b) through flexible printed circuit (FPC) or cables (9).In another embodiment, the secondary imaging sensor (7) may be hosted directly by the FPC with stiff backing and directly connect to an end of the FPC to a connector on the PCB associated with the primary imaging sensor.

In an embodiment, the printed circuit boards (PCB) (8a, 8b) with circuits and components mounted on it my be configured to support the first imaging sensor (6) and the second imaging sensor (7) to be functional by providing power supply, control signals to the image sensors (6, 7), and support image streaming interfaces with computing unit for image processing.

In an embodiment, as apparent from FIG . 2 , the lens stack (2), the beam splitter (3), the first imaging sensor (6) and the second imaging sensor (7) may be aligned to obtain sharp images. Glue (10) may be applied on an entry surface (13) of the first prism (4) and the lens stack (2) to join and align each other and followed by active alignment process. In an embodiment, the glue (10) may be ultraviolet (UV) and thermal curable glue.

In an embodiment, active alignment process may be performed with one of the element held in fixed position while the other is held in a movable gripper that is free to move the element in six degrees of freedom (DOF). As an example, the beam splitter (3) may be the fixed element while the lens stack (2) is moved in six DOF. A reference plane may be defined according to where the image sensors is to be positioned, and measurement is made according to this reference plane during alignment. Further, aligned lens stack (2) and the beam splitter (3) may be thermally cured for curing the glue.

Further, in an embodiment, the imaging device (1) may be communicatively coupled to a computing unit (not shown in figures) for operating the imaging device (1) and streaming video images of the driver. The computing unit may process the signals (i.e., images of the driver in different spectrum) from the imaging device (1) and may intervene with on-board systems like steering control module, braking control module and the like based on the driver behavior. In some embodiments, the computing unit may be configured to trigger an alarming module to alert the driver. The computing system may intervene in the on-board systems or alert driver based on the driver alertness, level of vigilances, signs of drowsiness, and the like which may be detected by the imaging device (1).

In operation, as seen in FIG . 4 , light rays captured within a field of view [FOV] may enter through the lens stack (2) and strike the beam splitter (3) along the primary optical axis (A-A). The beam splitter (3) may reflect a first predetermined spectrum of light from the received light rays along a secondary optical axis (B-B), which may be received by the second imaging sensor (7) and, allows the second predetermined spectrum of light from the received light rays along a primary optical axis (A-A), which may be received by the first imaging sensor (6). The images received by the first imaging sensor (6) and the second imaging sensor (7) of different spectrums may be received by the computing unit. The computing unit may process the signals (i.e., images of different spectrum) from the imaging device (1) to monitor the condition of the driver. The computing unit may intervene with on-board systems like steering control module, braking control module and the like based on determined condition of the driver. In some embodiments, the computing unit may process the signals (i.e., images of different spectrum) individually or fuse the images captured by the imaging device (1) in different spectrums to determine condition of the driver. In an embodiment,the configuration of the imaging device (1)aids in capturing images in different spectrums and, thus eliminates the need of multiple imaging devices for capturing images in different spectrums.

Equivalents

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

It will be understood by those within the art that, in general, terms used herein, are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to, " the term "having" should be interpreted as "having at least, " the term "includes" should be interpreted as "includes but is not limited to, " etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding the description may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a"or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated in the description. Referral Numerals:

Claims

Patent claims

1.An imaging device (1) for a driver monitoring system, comprising:

• a lens stack (2) comprising a plurality of lenses (2b) stacked along a primary optical axis (A-A) of the imaging device (1), each of the plurality of lenses (2b) is configured to receive light rays captured within a field of view of the imaging device (1);

• a beam splitter (3)positioned behind the lens tack (2) along the primary optical axis (A-A),wherein a portion of the beam splitter (3) is coated with a dichroic coating (12) to reflect a first predetermined spectrum of light from the received light rays along a secondary optical axis (B-B) and allow a second predetermined spectrum of light from the received light rays along the primary optical axis (A-A);

• a first imaging sensor (6) positioned in the primary optical axis (A-A) and is configured to receive the second predetermined spectrum of light; and

• a second imaging sensor (7)positioned in the secondary optical axis (B-B) and is configured to receive the first predetermined spectrum of the light, wherein the beam splitter is further coated with an anti-reflection coating comprising:

• a single layer anti-reflection coating; or

• a broad bandwidth anti-reflection coating.

2.The imaging device (1) as claimed in claim 1, wherein the beam splitter (3) is a cube beam splitter (3) comprising a first prism (4) and a second prism (5) bonded to each other along a hypotenuse side.

3. The imaging device (1) as claimed in claim 2, wherein the hypotenuse side of the first prism (4) is coated with the dichroic coating (12).

4. The imaging device (1) as claimed in claim 2, wherein the first prism (4)and the second prism (5)are optically bonded to each other through an optically transparent glue (10).

5. The imaging device (1) as claimed in claim 2, wherein a portion of each of the first prism (4) and the second prism (5) is coated with an anti-reflection coating.

6. The imaging device (1) as claimed in claim 1, wherein the first predetermined spectrum of light is an infrared spectrum, and the second predetermined spectrum of light is a visible spectrum.

7. The imaging device (1) as claimed in claim 1, wherein the first imaging sensor (6) is parallelly positioned in the primary optical axis (A-A) and the second imaging sensor (7) ispositioned in the second optical axis (B-B)perpendicular to the primary optical axis (A-A).

8. The imaging device (1) as claimed in claim 1, wherein the first imaging sensor (6) and the second imaging sensor (7) are communicatively coupled to a printed circuit board (PCB) (8a, 8b).

9.A driver monitoring system for a vehicle, the system comprising: ■ an imaging device (1), arranged in an instrument cluster (100) of the vehicle for monitoring a driver, the device comprising: o a lens stack (2) comprising a plurality of lenses (2b) stacked along a primary optical axis (A-A) of the imaging device (1), each of the plurality of lenses (2b) is configured to receive light rays captured within a field of view of the imaging device

(l); o a beam splitter (3) positioned behind the lens stack (2) and along the primary optical axis (A-A), wherein a portion of the beam splitter (3) is coated with a dichroic coating (12) to reflect a first predetermined spectrum of light from the received light rays along a secondary optical axis (B-B) and allow a second predetermined spectrum of light from the received light rays along the primary optical axis (A-A); o a first imaging sensor (6)positioned in the primary optical axis (A-A)and is configured to receive the second predetermined spectrum of light; and o a second imaging sensor (7) positioned in the secondary optical axis (B-B) and is configured to receive the first predetermined spectrum of the light;

■ a computing unit, communicatively coupled to the first imaging sensor (6) and the second imaging sensor (7), wherein the computing unit is configured to determine condition of the driver, based on images captured by the imaging device

(1).

10. The system as claimed in claim 9, wherein the beam splitter (3) is a cube beam splitter (3) comprises a first prism (4) and a second prism (5) bonded to each other along a hypotenuse side.

11. The system as claimed in claim 10, wherein the hypotenuse side of the first prism (4) is coated with the dichroic coating (12).

12. The system as claimed in claim 10, wherein the first prism (4)and the second prism (5)are optically coupled each other through an optically transparent glue (10).

13. The system as claimed in claim 9, wherein a portion of each of the first prism (4)and the second prism (5) is coated with an anti-reflection coating.

14. The system as claimed in claim 9, wherein the first predetermined spectrum of light is an infrared spectrum and the second predetermined spectrum of light is a visible spectrum.

15. The system as claimed in claim 9, wherein the first imaging sensor (6) is positioned parallel to the primary optical axis (A-A) and the second imaging sensor (7) is positioned perpendicular to the primary optical axis (A-A).