Patent ID: 12235411

DETAILED DESCRIPTION

FIG.1illustrates an example vehicle1. In this example, the vehicle includes a cabin3, a trailer5and a mirror system7. Although the example vehicle1is shown generally as a commercial vehicle, the vehicle1could be any other vehicle incorporating the mirror system described herein.

The mirror system7is positioned on the outside of the vehicle1and is oriented such that the environment outside the vehicle1is visible to a user. In the example vehicle, the mirror system7is rear- and/or side-facing and provides a mirror replacement for a conventional rear-view mirror.

FIG.2illustrates a sectional view of a camera system10of the mirror system7. The camera system10has a housing12that includes a frontal lens element14. The frontal lens element14is coupled to the housing12. A sealing member16is provided to prevent moisture from penetrating through the frontal lens element14. The frontal lens element14includes an inner surface18and an outer surface20. The outer surface20is exposed to the outside environment under normal operating conditions.

Referring toFIG.3, the frontal lens element14in one example includes a coating22and22A. In this illustrative example, the coating22is deposited along the inner surface18and the coating22A is deposited along the outer surface20. In another example, the coating22is not deposited on the inner surface18(shown as dashed lines for illustrative purposes).

The coating22can be made of a transparent conductive oxide (TCO) thin film. TCOs are a class of semiconducting thin films that have an optical band-edge typically in the ultraviolet (UV) spectral region, thereby making them optically transparent in the visible and near-infrared regions. In addition, doping these semiconducting films with appropriate dopant elements, makes the films electrically conductive, usually of n-type conduction. The conductivity is in the range appropriate for ohmic heating of the film upon applying a voltage. Furthermore, the high charge carrier concentration imparts in the films the radiative property of low emissivity with a concomitant high reflectivity in the infrared spectral wavelength region. TCOs can therefore be coated on optical elements such as those in imaging devices, e.g. cameras, and also laser scanning detection and ranging system, e.g. LiDAR, both operating variously in the visible and near-infrared spectral regions, without significantly reducing the amount of light collected by the imaging optics. Accordingly, TCOs are advantageous at preventing or reducing frost and ice formation due to their inherent property of low emissivity

TCOs are inherently hydrophilic materials. However, chemical treatment, including nano-structure patterning of these and doping some materials with fluorine, can produce TCOs with hydrophobic characteristics. For example, the coatings22,22A may be nano-etched in a motheye-type pattern to provide a hydrophobic surface that minimizes water droplet formation, retention, and adherence, while also imparting anti-reflective characteristics to the layer, thereby reducing broadband light reflection to maximize light transmission in the camera. The pattern may be printed in a temporarily photo-resistive layer using a lithographic processing method and thereafter etched in. Etching is a standard fabrication method of selectively removing part of the surface of the coatings22,22A to reveal the microstructure, which creates a contrast between different regions of the TCO coating22through differences in topography. In one example, etching can be achieved using a plasma etching process. The differences in topography are numerically designed to reduce the reflectivity of the surface while maintaining the property of low emissivity for frost or ice formation. In this example, the emissivity has a value in the range 0.05 to 0.2. Nano-etching (etching of patterns in the 1 nm to 100 nm range) can be achieved, in some examples, using wet-etching or, more likely, plasma (dry)-etching. In the illustrated example, an outer surface24of the coating22A is nano-etched such that the coating22A provides a multi-functional layer in which anti-reflective properties, low emissivity properties, and hydrophobic properties are achieved in a single layer.

In one example, the coatings22,22A can be indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), or fluorine-doped tin oxide (FTO). Material selection of the coatings22,22A serves to provide a sealing coat to the frontal lens14, a bond or environmental barrier coating with one or more layers to protect the frontal lens element14from chemical attack and erosion through abrasion, usually a result of fast airflow and environmental particle pollution. The coatings22,22A will also function as a frost-prevention coating when designed and fabricated as described above.

As shown inFIG.3with continued reference toFIG.2, the coating22A on the inner surface18of lens element14is connected to an electric power source through an electrical connector26such that the coating22A acts as a resistive heater when power is applied. In some examples, an additional or alternative electrical connection26in the form of a pad is provided between the frontal lens element14and the coating22. The power source26aids in removing frost or ice from the frontal lens element14by distributing heat along the outer surface24of the coating22A through conductive heat transfer through lens element14. In one example, the electrical connection between the frontal lens element14and the coating22allows the coating22to operate as a two-wire thermistor, whereby the temperature of14may be monitored periodically and heated if necessary to preemptively prevent frost or ice accumulation.

Referring toFIG.4, with continuing reference toFIG.3, the outer surface24of the coating22A is structured such that there is a contrast between the outer surface24topography and the coating22A topography. In this example, the outer surface24is nanostructured as a random anti-reflective sub-layer or as moth-eye structures28, according to design specification and the level of abrasion resistance required. The nano-structures28include an eye portion30and a stem portion32. The stem portion32establishes a change in structure between the eye portion30and the outer surface24. In some example, the nano-structures28will have dimensions far less than the incidence of light and thus, form a region of graded refractive index33at the interface between the outer surface24and the outside environment, giving the anti-reflective property

FIG.5illustrates a frontal lens114according to another example. Similarly, the frontal lens114includes an inner surface118and an outer surface120. A coating122A is deposited on the outer surface120. An anti-reflective (AR) coating122AR is deposited on the inner surface118. In addition, a coating122A is deposited on an inner surface120AR of the AR coating122AR (shown as dashed lines inFIG.5for illustrative purposes). In other examples, the frontal lens114selectively includes either the coating122on the inner surface118or the AR coating122AR on the inner surface118. As shown, the frontal lens114also includes an electrical connector126that is connected to the coating122A and an additional or alternative electrical connection126that is connected to the coating122.

The AR coating122AR includes multiple layers L. Each of the layers L are numerically optimized using a characteristic matrix (CM) method. The CM method includes one dimensional rigorous electromagnetic field calculations. The product of each of the layer matrix includes incident electric field amplitude at each interface between layers L. In one example, the AR coating122AR includes eight layers, thus enabling broadband spectral response from 450-850 nm of T>99.5%. Increasing the number of layers L results in steeper roll-off and decreased T. The CM method enables operable transmission, reflectance, and absorptance properties of the camera system10. The product of the CM method is in accordance with the coating122, the topography of the coating122, and the thickness of the coating122required for particular design applications.

Typically, the surface reflectance averaged over the spectral region of interest may be reduced to less than 0.5%, even to <0.1%, depending on AR coating122AR design specifications. The design methods employed are phenomenologically identical to impedance matching methods for maximum power transmission in electrical systems. The layer L may number from 1 to 20 depending on the application and the specifications, and are typically deposited in vacuum systems with the optical elements mounted in the chamber in their dozens or hundreds to reduce production costs.

The layers L can be made of various materials depending on the needs of a given implementation. In some examples, the layers L will include silica, and one or more from a group of metal oxides comprising: tantala, titania, hafnia, niobia, alumina, aluminum oxynitride and mixtures thereof.

FIG.6is a flowchart illustrating a method200of reducing both broadband reflection and emissivity of mirror replacement systems, such as the mirror replacement system element10.

At step210, the outer surface of the lens214is prepared using any known optical fabrication method. The preparation in step210corrects the shape of the outer surface of the lens214. At step220, each layer of a multilayered anti-reflective (AR) coating is optimized using the CM method. At step230, a first TCO coating is deposited on at least one of an inner and outer surface of the lens214. At step240, the multilayered AR coating is deposited on the inner surface of lens214. At step250, a second TCO coating is deposited on an outer surface of the multilayered AR coating. The deposition of the TCO coating and the multilayered AR coating can be achieved using evaporation, ion-assisted deposition, plasma sputtering, ion-beam sputtering, atomic layer deposition, chemical vapor deposition, and combination thereof. Regarding the multilayered AR coating, the choice of deposition method is restricted by the number of multilayer AR coating layers, physical and thermal characteristics of the substrate and deposition materials, and cost. At step260, the TCO coatings can be structured (e.g., moth-eye structuring) and chemically treated to improve hydrophobic properties. It is contemplated that in the case of the tin oxide the hydrophobic surface treatment compounds may include alkyl-silanes and alkyl-tin. At step270, the lens214is assembled on one or more camera systems that are arranged on a mirror replacement system of a vehicle. The lens214includes an inner and an outer surface that are optically aligned and tested for optical performance. In some examples, the lens214is a 360° view lens.

The mirror replacement systems disclosed herein can be used in vehicle applications. Vehicular optical systems (e.g., cameras) are increasingly subjected to harsh outside environments (e.g., thermal stress, high humidity, corrosion, and abrasion). Providing the coatings22,122helps maintain optical performance independent of environment factors, act as a barrier to moisture or chemical attack, be hydrophobic/hydrophilic, and be mechanically robust against thermal cycling and transients.

Although the different non-limiting examples are illustrated as having specific components, the examples of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting examples in combination with features or components from any of the other non-limiting examples.

It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed and illustrated in these exemplary embodiments, other arrangements could also benefit from the teachings of this disclosure.

The foregoing description shall be interpreted as illustrative and not in any limiting sense. A worker of ordinary skill in the art would understand that certain modifications could come within the scope of this disclosure. For these reasons, the following claims should be studied to determine the true scope and content of this disclosure.