DEVICE WITH GLAZING AND ASSOCIATED THERMAL CAMERA, AND OPTIMIZATION METHODS

Abstract

A device includes a vehicle glazing, including, in a peripheral zone, a through-hole including an insert and a thermal camera.

Claims

1. A device , comprising: a vehicle glazing, of given thickness E1, the vehicle glazing having an outer main face oriented outward and an inner main face on a vehicle interior side, the vehicle glazing comprising, in a peripheral zone, a through-hole between the inner main face and the outer main face, the through-hole being delimited by a side wall of the vehicle glazing, in said through-hole, an insert made of a material that is transparent in a range A of wavelengths in the an infrared spectrum beyond 2.5 .Math.m, ranging at least from 9.5 to 10.5 .Math.m, the insert being of given thickness e, made of a material of refractive index n in the range A, with an input face oriented toward the vehicle interior and an output face, the input face fitting within a rectangle or square of width Wi and height Di with aspect ratio Di/Wi of at least 0.8 and of at most 1.2, with Di at most 35 mm, defining a center O which is the an intersection of the diagonals of said rectangle, a thermal camera, disposed on the inner main face side so as to receive an electromagnetic radiation after passing through said insert, the thermal camera comprising an input pupil, with a height p, and an infrared detection system in the a range A and a lens, the camera being defined by: an optical axis X' passing through the a center C of the pupil, C facing the insert, a vertical viewing angle θ of at least 10°, the thermal camera being of given volume defined by a point of contact T capable of touching the vehicle glazing first, or a plate on the inner main face of the vehicle glazing, or the insert, or a piece in a peripheral environment of said vehicle glazing, in position mounted in a vehicle,
the an orthogonal reference frame (O, X, Y, Z) is defined in which X is an axis parallel to the optical axis X', oriented toward the outer main face, Z is the an axis normal to the optical axis, the axis Y is normal to X in the a plane containing P0 oriented toward the a top of the vehicle glazing, Z is normal to P0
T being in a plane P0 passing through O and C or Tv, which is a virtual point of contact, is defined as being the a projection of T in said plane P0, w being the distance according to X and algebraic in the plane P0 from T or Tv and h is the a distance according to Y in the plane P0 between C and T or Tv, the input main face of the insert having an inclination defined by an angle α with respect to X,
wherein a first straight line Dt1 is defined $y=-\text{tan}\left(\frac{\theta }{2}\right)x+\frac{\left(\text{cos}\alpha \text{tan}\left(\frac{\theta }{2}\right)-\text{sin}\alpha \right)\left[D_i\sqrt{1-\frac{1}{n^2}{\text{cos}}^2\left(\alpha -\frac{\theta }{2}\right)}-2\frac{e}{n}\text{cos}\left(\alpha -\frac{\theta }{2}\right)\right]}{2\sqrt{1-\frac{1}{n^2}{\text{cos}}^2\left(\alpha -\frac{\theta }{2}\right)}}$
a second straight line Dt2 is defined $y=\text{tan}\left(\frac{\theta }{2}\right)x+\frac{D_i}{2}\left[\text{cos}\alpha \text{tan}\left(\frac{\theta }{2}\right)+\text{sin}\alpha \right]$
Dt1 and Dt2 are secant at $\text{C}0\left({\text{x}}_{\text{C}0,}{\text{y}}_{\text{C}0}\right)$ with $x_{c_O}=-\frac{\text{sin}\alpha \left[D_i\sqrt{1-\frac{1}{n^2}{\text{cos}}^2\left(\alpha -\frac{\theta }{2}\right)}-\frac{e}{n}\text{cos}\left(\alpha -\frac{\theta }{2}\right)\right]+\frac{e}{n}\text{cos}\alpha \text{tan}\left(\frac{\theta }{2}\right)\text{cos}\left(\alpha -\frac{\theta }{2}\right)}{2\text{tan}\left(\frac{\theta }{2}\right)\sqrt{1-\frac{1}{n^2}{\text{cos}}^2\left(\alpha -\frac{\theta }{2}\right)}}$ $y_{C0}=\text{tan}\left(\frac{\theta }{2}\right)x_{C0}+\frac{D_i}{2}\left[\text{cos}\alpha \text{tan}\left(\frac{\theta }{2}\right)+\text{sin}\alpha \right]$
a third straight line Dt3 is defined $y=-\tan \left(\alpha \right)\left(x+w\right)-h$
Dt1 and Dt3 are secant at $\text{E}\left({\text{x}}_{\text{E}},{\text{y}}_{\text{E}}\right),$
Dt2 and Dt3 are secant at $\text{F}\left({\text{x}}_{\text{F}},{\text{y}}_{\text{F}}\right)$ $x_F=-\frac{D_I\cos \alpha \tan \frac{\theta }{2}+D_I\sin \alpha +2w\tan \alpha +2h}{2\left(\tan \alpha +\tan \frac{\theta }{2}\right)}$ $y_F=\tan \left(\frac{\theta }{2}\right)x_F+\frac{D_i}{2}\left[\cos \alpha \tan \left(\frac{\theta }{2}\right)+\sin \alpha \right]$ $x_E=-\frac{\frac{\left(\text{cos}\alpha \text{tan}\left(\frac{\theta }{2}\right)-\text{sin}\alpha \right)\left[D_i\sqrt{1-\frac{1}{n^2}{\text{cos}}^2\left(\alpha -\frac{\theta }{2}\right)}-2\frac{e}{n}\text{cos}\left(\alpha -\frac{\theta }{2}\right)\right]}{2\sqrt{1-\frac{1}{n^2}{\text{cos}}^2\left(\alpha -\frac{\theta }{2}\right)}}+w\text{tan}\alpha \text{+}h}{\text{tan}\alpha -\text{tan}\frac{\theta }{2}}$ ${\gamma }_E=-\text{tan}\left(\alpha \right)\left(x_E+w\right)-h$ x.sub.C being a negative value, yc being a positive value, wherein
in a case a)
y.sub.F > y.sub.C0 > y.sub.E
$\text{C}\left({\text{x}}_{\text{c}}{\text{, y}}_{\text{c}}\right)$ is inside a triangle of vertices $\text{C0}\left({\text{x}}_{\text{C0,}}{\text{y}}_{\text{C0}}\right)\text{F}\left({\text{x}}_{\text{F,}}{\text{y}}_{\text{F}}\right)\text{and}\text{E}\left({\text{x}}_{\text{E,}}{\text{y}}_{\text{E}}\right),$ at least 50% of the pupil being positioned in said triangle by including E; or
in a case b)
when $\left|x_{C0}\right|<\left|x_F\right|$ then ${\text{y}}_{\text{C}}<\left({\text{y}}_{\text{C0}}+5\text{mm}\right)$
a point K of intersection is then defined between a straight line $\text{y}={\text{y}}_{\text{C0}}$ and Dt3 therefore $x_K=w-\frac{y_{C0}-h}{\tan \left(\alpha \right)}$ $y_K=y_{C0}$ and $\left|x_K-x_{C0}\right|\le 10mm$ .

2. The device as claimed in claim 1, wherein, in the case a), at least 70% or 80% or 90% of the pupil is positioned in said triangle C0FE by including E.

3. The device as claimed in claim 1, wherein, in the case $\left(\text{a}\right),-\left({\text{y}}_{\text{C0}}\text{-2 mm}\right)<{\text{y}}_{\text{C}}<\left({\text{y}}_{\text{C0}}\text{-0}\text{.5 mm}\right)\text{and}\left({\text{x}}_{\text{F}}\text{-}\right)5\left(\text{mm}\right)<{\text{x}}_C<\left({\text{x}}_{\text{F}}+2\text{mm}\right)$ .

4. The device as claimed in claim 1, wherein $y_c<10mm$ and/or $\left|x_C\right|<5cm$ .

5. The device as claimed in claim 1, wherein θ is at least 20°.

6. The device as claimed in claim 1, wherein Di is at most 20 mm.

7. The device as claimed in claim 1, wherein X′ forms an angle of at most 20°, 10° with the horizontal and/or at most an angle equal to θ/2 ± 2°.

8. The device as claimed in claim 1, wherein the material of the insert is germanium, zinc sulfide.

9. The device as claimed in claim 1, wherein the material of the insert exhibits an infrared optical transmission of at least 50% in said range A and a light transmission of at least 30% at a reference wavelength lying between 500 nm and 600 nm.

10. The device as claimed in claim 1, wherein the material of the insert is chosen from among: a compound of zinc comprising selenium and/or sulfur, or a compound comprising a barium fluoride.

11. The device as claimed in claim 1, wherein the vehicle glazing forms a laminated glazing , the laminated glazing comprising a first sheet of glass with said inner face and an opposite face and a second sheet of glass or plastic with said outer face on an internal side of the vehicle interior, the first sheet of glass and the second sheet of glass or plastic being linked by an interlayer.

12. A vehicle comprising said device as claimed in claim 1.

13. An optimization method for forming the device defined as claimed in claim 1, comprising, for a camera with θ, p, given, determining both a smallest possible insert height D.sub.min, satisfying the case a), and the insert height Di ≥ D.sub.min is chosen such that $\left({\text{y}}_{\text{F}}{\text{-y}}_{\text{C0}}\right)\ge 0.5\text{p/2}$ .

14. An optimization method for forming the device defined as claimed in claim 1 , comprising, for a given insert height Di, for a camera with given p, determining a smallest possible θmin, satisfying the case a) and θ≥θmin is chosen such that (y.sub.F-y.sub.C0) ≥ 0.5p/2.

15. An optimization method for forming the device defined as claimed in claim 1 , comprising, for a given insert height Di and for a camera with given θ, p, determining a smallest possible h.sub.min that satisfies the case a) and h ≥ h.sub.min is chosen such that $\left({\text{y}}_{\text{F}}{\text{-y}}_{\text{C0}}\right)\ge 0.5\text{p/2}$ .

16. The device as claimed in claim 1, wherein the vehicle glazing is a motor vehicle or rail car glazing.

17. The device as claimed in claim 1, wherein the peripheral zone is in an upper part of the glazing.

18. The device as claimed in claim 1, wherein the infrared spectrum is from 8 to 12 .Math.m.

19. The device as claimed in claim 1, wherein the insert is circular.

20. The device as claimed in claim 1, wherein Di>Wi.

Description

[0120] Some advantageous but nonlimiting embodiments of the present invention are described hereinbelow, which can of course be combined with one another if necessary.

[0121] FIG. 1 schematically represents a vehicle with a device 100 comprising a windshield with an insert and a thermal camera in the vehicle interior, this is a partial cross-sectional view in a plane P0 passing through the center C of the pupil of the camera and a center O of the insert.

[0122] FIG. 2 schematically represents the insert and thermal camera of FIG. 1 with the parameters (coordinates, etc.) that are influential for the optimized positioning of the camera, this is a partial cross-sectional view in a plane P0 passing through the center C of the pupil of the camera and a center O of the insert.

[0123] FIG. 3 schematically represents the insert and the thermal camera of FIG. 1 with exemplified parameters (example 1) that are influential for the optimized positioning of the camera, this is a partial cross-sectional view in a plane P0 passing through the center C of the pupil of the camera and a center O of the insert.

[0124] FIGS. 3'and 3" represent diagrams of the lighting of the infrared sensor of the thermal camera, in gray level for the example 1 and a counter-example 1'.

[0125] FIG. 4 schematically represents the insert and the thermal camera of FIG. 1 with exemplified parameters (example 2) that are influential for the optimized positioning of the camera, this is a partial cross-sectional view in a plane P0 passing through the center C of the pupil of the camera and a center O of the insert.

[0126] FIG. 4’represents a diagram of the lighting of the infrared sensor of the thermal camera, in gray level for the example 2.

[0127] FIG. 5 schematically represents the insert and the thermal camera of FIG. 1 with exemplified parameters (example 3) that are influential for the optimized positioning of the camera, this is a partial cross-sectional view in a plane P0 passing through the center C of the pupil of the camera and a center O of the insert.

[0128] FIG. 5’represents a diagram of the lighting of the infrared sensor of the thermal camera, in gray level for the example 3.

[0129] FIGS. 6a and 6b respectively represent the variation of the ordinate y and of the negative abscissa x of the points C0, E, F as a function of θ for the case a) and the case b).

[0130] FIGS. 7a and 7b respectively represent the variation of the ordinate y and of the negative abscissa x of the points C0, E, F as a function of Di for the case a) and the case b).

[0131] FIGS. 8a and 8b respectively represent the variation of the ordinate y and of the negative abscissa x of the points C0, E, F as a function of α for the case a) and the case b).

[0132] FIGS. 9a and 9b respectively represent the variation of the ordinate y and of the negative abscissa x of the points C0, E, F as a function of h for the case a) and the case b).

[0133] FIGS. 10a and 10b respectively represent the variation of the ordinate y and of the negative abscissa x of the points C0, E, F as a function of n for the case a).

[0134] FIG. 1 schematically represents a windshield 100 according to the invention, in cross section with a thermal camera 9 placed behind the windshield facing a zone which is preferably situated in the central and upper part of the windshield. In this zone, the camera can be oriented with a certain angle with respect to the horizontal. In this example, the camera is horizontal. In particular, the lens and the infrared camera are oriented directly toward the image input zone, according to a direction parallel to the ground.

[0135] The windshield is a conventional laminated glazing comprising: [0136] an outer sheet of glass 1, preferably tinted, for example made of TSA glass and 2.1 mm thick, with an outer face F1 and an inner face F2, [0137] and an inner sheet of glass 1' (or, as a variant, a sheet of plastic), for example TSA glass (or clear or extra clear glass) and 2.1 mm thick or even 1.6 mm or even less, with outer face F3 and inner face F4 on the vehicle interior side, [0138] the two sheets of glass being linked to one another by an interlayer made of thermoplastic material 3, more often than not of polyvinylbutyral (PVB), preferably clear, of submillimetric thickness, possibly having a cross section reducing in wedge form from top to bottom of the laminated glazing, for example a PVB (RC41 from Solutia or Eastman), approximately 0.76 mm thick, or as a variant, if necessary, an acoustic PVB (three-layer or four-layer), for example approximately 0.81 mm thick, for example an interlayer made of three PVB layers.

[0139] Conventionally and as is well known, the windshield is obtained by hot-laminating elements 1, 1' and 3.

[0140] The windshield 100 comprises, on the outer face 11 for example (or preferably on F2 12 and/or on face F3 13 or F4 14), preferably an opaque coating, for example black 6, such as a layer of enamel or of black lacquer, over all the surface of the glazing disposed facing the device incorporating the thermal camera (therefore over all the perimeter of the hole), including its housing 8 (plastic, metal, etc.), so as to hide the later. The housing 8 can be fixed to a plate 7 glued to the face F4 by a glue 80 and to the roof 9.

[0141] The opaque layer 6 can extend beyond the zone with the insert. Possibly, the (lateral) extension of the opaque layer forming a strip at the top border of the through-hole so that the windshield has a (black) opaque strip along the top longitudinal edge, even a (black) opaque frame over all the periphery.

[0142] According to the invention, in the peripheral zone facing the camera, the windshield comprises a through-hole 4 between the inner face 11 and the outer face 14, the hole being delimited by a lateral wall 10 of the laminated glazing (glass ⅟PVB 3/glass 1'), said through-hole comprising: [0143] an insert 2 made of a material that is transparent in a range A of wavelengths in the infrareds which goes at least from 9.5 to 10.5 .Math.m and preferably from 8 to 12 .Math.m, the insert being of given thickness e, [0144] between the insert and the side wall, means for fixing the insert, notably in the form of a ring 5 made of flexible material, polymer, the fixing means being notably glued to the side wall.

[0145] The material of the insert 2 is also transparent in the visible at a reference wavelength lying between 500 nm and 600 nm.

[0146] It can be transparent in the visible at least in a range B going from 550 to 600 nm.

[0147] The material of the insert 2 exhibits an infrared transmission of at least 50% and, better, at least 65% in said range A and a light transmission of at least 30% and, better, at least 40% at the reference wavelength and, better, in the range B. The material of the insert 2, preferably polycrystalline, is chosen from among: [0148] a compound of zinc including selenium and/or sulfur, or [0149] a compound including a fluoride of barium.

[0150] A particular choice is: [0151] a compound including a multispectral zinc sulfide, in particular obtained after hot isostatic pressing, notably including selenium, such as ZnS.sub.xSe.sub.1-x, with x preferably at least 0.97, in particular multispectral ZnS, [0152] or a compound including a zinc selenide, in particular ZnSe, notably including sulfur, such as ZnSe.sub.yS.sub.1-y with y at least 0.97, [0153] a compound including a fluoride of barium, notably including calcium and/or strontium, notably Ba.sub.1-i-j Ca.sub.jSr.sub.iF.sub.2 with i and j preferably at most 0.25 or even Ba.sub.1-iCa.sub.iF.sub.2 with i preferably at most 0.25, in particular BaF.sub.2.

[0154] The insert 2 comprises an outer face 21 and an inner face 22 and it comprises, here, preferably, a mechanical and/or chemical protection layer 2' on the outer face and possibly on the inner face. This is a coating chosen from among a layer comprising a zinc sulfide, a diamond layer or a DLC layer.

[0155] Preferably, a multispectral ZnS can be chosen that is bare or covered with a protective layer of zinc sulfide or a ZnSe covered by a protective layer of zinc sulfide.

[0156] The through-hole 4 can alternatively be a notch, therefore a through-hole preferably opening on the roof side.

[0157] The through-hole (and the insert) can be in another region of the windshield or even in another glazing of the vehicle.

[0158] The glazing of the vehicle can be monolithic.

[0159] The insert is of given thickness e, notably from 3 to 10 mm, made of a material of refractive index n in the range A, notably from 1.35 to 4.5.

[0160] The insert is preferably of circular or quasi-circular form, the input face fitting within a rectangle or square of width Wi and height Di with aspect ratio Di/Wi of at least 0.8 and at most 1.1, with Di>Wi, defining a center O which is the intersection of the diagonals of said rectangle.

[0161] The so-called thermal camera 9 comprises a circular input pupil 91, with a height p, (generally diameter) and an infrared detection system in the range A and a lens, the camera being defined by: [0162] an optical axis X′ passing through the center C of the pupil, C facing the insert, [0163] a vertical viewing angle θ of at least 10°, 20° and in particular at most 70°, 60°.

[0164] The camera is of given volume defined by a point of contact T (wedge/upper-end plane of the lens/in front of or behind the lens) here capable of first touching a plate 7 made of plastic on the inner face of the glazing, for example of 1.5 mm, with a hole in line with the through-hole 4. This plate can be used to fix the camera 9.

[0165] The orthogonal reference frame (O, X, Y, Z) is defined in which X is an axis parallel to the optical axis X', oriented toward the outer face, Z is the axis normal to the optical axis, the axis Y is normal to X in the plane containing P0 oriented toward the top of glazing, Z is normal to P0.

[0166] T is in a plane P0 passing through O and C (or Tv, called virtual point of contact, is defined as being the projection of T in said plane P0), w is the distance according to X, algebraic in the plane P0 of T or Tv and h is the distance according to Y in the plane P0 between C and T or Tv; the input face 21 of the insert having an inclination defined by an angle α with respect to X and of at least 20°, 30°, 35°, 40° and up to 60°, even 90° or 80° with respect to the horizonal, in particular X' being at most 20° with respect to the horizontal.

[0167] FIG. 2 schematically represents the insert and the thermal camera of FIG. 1 with the parameters (coordinates, etc.) that are influential for the optimized positioning of the camera 9, this is a partial cross-sectional view in a plane P0 passing through the center C of the pupil of the camera and a center O of the insert 2.

[0168] In relation to FIG. 2, three limit conditions are defined

Condition on the Top Radius (via Dt2)

[0169] The limit case corresponds to the slope straight line

[00016]$\tan \left(\frac{\theta }{2}\right)$

and which passes through the point S of coordinates:

[00017]$x_S=-\frac{D_i}{2}\cos \alpha$

and

[00018]$y_S=\frac{D_i}{2}\sin \alpha$

therefore straight line Dt2 of equation:

[00019]$y=\tan \left(\frac{\theta }{2}\right)x+\frac{D_i}{2}\left[\cos \alpha \tan \left(\frac{\theta }{2}\right)+\sin \alpha \right]$

[0170] This is the limit case, the condition is observed if under this straight line Dt2, therefore:

[00020]$y<\tan \left(\frac{\theta }{2}\right)x+\frac{D_i}{2}\left[\cos \alpha \tan \left(\frac{\theta }{2}\right)+\sin \alpha \right]$

Condition on the Bottom Radius (Dt1)

[0171] Take the slope straight line

[00021]$-\tan \left(\frac{\theta }{2}\right)$

and which passes through the point I, whose coordinates must be found using the Descartes laws. Let i.sub.1 be the angle of incidence of the radius on the inner face of the insert, then (because the sum of the angles of a triangle equal to pi):

[00022]$i_1=\frac{\pi +\theta }{2}-\alpha ,$

let i.sub.2 be the angle of the radius in the insert of optical index n, then

[00023]$i_2={\sin }^{-1}\left(\frac{1}{n}\sin i_1\right).$

[0172] Now take the coordinates of the point B:

[00024]$x_B=\frac{D_i}{2}\cos \alpha$

and

[00025]$y_B=-\frac{D_i}{2}\sin \alpha$

and the distance between the point B and the point I which is:

[00026]$L_{B1}=e\tan i_2$

with e the thickness of the insert. Then

[00027]$\stackrel{.fwdarw.}{OI}=\stackrel{.fwdarw.}{OB}+\stackrel{.fwdarw.}{BI}$

which makes it possible to calculate the coordinates of the point I:

[00028]$x_I=\frac{D_i}{2}\cos \alpha -L_{BI}\cos \alpha$

and

[00029]$y_I=-\frac{D}{2}\sin \alpha +L_{BI}\sin \alpha$

i.e., according to the parameters of the system:

[00030]$x_I=\frac{D_i}{2}\cos \alpha -\frac{\frac{e}{n}\cos \alpha \cos \left(\alpha -\frac{\theta }{2}\right)}{\sqrt{1-\frac{1}{n^2}{\cos }^2\left(\alpha -\frac{\theta }{2}\right)}}$

[00031]$y_I=-\frac{D_i}{2}\sin \alpha +\frac{\frac{e}{n}\sin \alpha \cos \left(\alpha -\frac{\theta }{2}\right)}{\sqrt{1-\frac{1}{n^2}{\cos }^2\left(\alpha -\frac{\theta }{2}\right)}}$

which makes it possible to give the equation of the straight line Dt1:

[00032]$\begin{array}{l}y=-\tan \left(\frac{\theta }{2}\right)x+\\ \frac{\left(\cos \alpha \tan \left(\frac{\theta }{2}\right)-\sin \alpha \right)\left[D_i\sqrt{1-\frac{1}{n^2}{\cos }^2\left(\alpha -\frac{\theta }{2}\right)}-2\frac{e}{n}\cos \left(\alpha -\frac{\theta }{2}\right)\right]}{2\sqrt{1-\frac{1}{n^2}{\cos }^2\left(\alpha -\frac{\theta }{2}\right)}}\end{array}$

[0173] In the same way as previously, this is the limit case and it is important to be above this straight line Dt1 therefore:

[00033]$\begin{array}{l}y>-\tan \left(\frac{\theta }{2}\right)x+\\ \frac{\left(\cos \alpha \tan \left(\frac{\theta }{2}\right)-\sin \alpha \right)\left[D_i\sqrt{1-\frac{1}{n^2}{\cos }^2\left(\alpha -\frac{\theta }{2}\right)}-2\frac{e}{n}\cos \left(\alpha -\frac{\theta }{2}\right)\right]}{2\sqrt{1-\frac{1}{n^2}{\cos }^2\left(\alpha -\frac{\theta }{2}\right)}}\end{array}$

[0174] The most favorable case (rear vertex of the triangle, denoted C.sub.0) has the coordinates (point secant between the straight line dt1 and the straight line dt2):

[00034]$x_{C0}=-\frac{\sin \alpha \left[D_i\sqrt{1-\frac{1}{n^2}{\cos }^2\left(\alpha -\frac{\theta }{2}\right)}-\frac{e}{n}\cos \left(\alpha -\frac{\theta }{2}\right)\right]+\frac{e}{n}\cos \alpha \tan \left(\frac{\theta }{2}\right)\cos \left(\alpha -\frac{\theta }{2}\right)}{2\tan \left(\frac{\theta }{2}\right)\sqrt{1-\frac{1}{n^2}{\cos }^2\left(\alpha -\frac{\theta }{2}\right)}}$

[00035]$y_{C0}=\tan \left(\frac{\theta }{2}\right)x_{c_O}+\frac{D_i}{2}\left[\cos \alpha \tan \left(\frac{\theta }{2}\right)+\sin \alpha \right]$

[0175] Even in the asymptotic case in which e is very small (limit e tends toward 0) the following applies:

[00036]$\underset{e.fwdarw.0}{\lim }{y}_{C0}=\frac{D_i}{2}\cos \alpha \tan \left(\frac{\theta }{2}\right)$

[0176] Now, since

[00037]$0<\alpha <\frac{\pi }{2}\text{and}$

[00038]$0<\alpha <\frac{\pi }{2}$

the following clearly applies in all cases

[00039]$y_{C0}>0$

which justifies this upward shift of the optical center of the camera.

Mechanical Condition

[0177] Let h be the height between the center C of the pupil and the “wedge which touches” denoted T and w the horizontal distance between the center of this pupil and the “wedge which touches”

[0178] now, the equation of the straight line Dt3 is:

[00040]$y=-\tan \left(\alpha \right)\left(x+w\right)-h$

[0179] This is the equation of the limit case, the condition is realized if:

[00041]$y<-\tan \left(\alpha \right)\left(x+w\right)-h$

[0180] Since the aim is to find the position of retraction of the camera (in x) which satisfies the other criteria, it is more eloquent to express the condition on x as a function of y:

[00042]$x=w-\frac{y-h}{\tan \left(\alpha \right)}$

[00043]$x<w-\frac{y-h}{\tan \left(\alpha \right)}$

[0181] In particular, in the case where y = y.sub.C0

[00044]$x_{\left(y=y_{C0}\right)}<w-\frac{y_{C0}-h}{\tan \left(\alpha \right)}$

w can be positive and negative (but generally fairly small as an absolute value) and x is always negative given the orientation of the axes.

[0182] The reference point for the position of the camera is the position of the point C which is the center of the input pupil of the camera but for the entire field of the camera to be used without shadow on the edges, all of the pupil of height p should be within the triangle formed by the three straight lines Dt1, Dt2 and Dt3.

[0183] Coordinates of the point F

[00045]$x_F=-\frac{D_I\cos \alpha \tan \frac{\theta }{2}+D_I\sin \alpha +2w\tan \alpha +2h}{2\left(\tan \alpha +\tan \frac{\theta }{2}\right)}$

[00046]$y_F=\tan \left(\frac{\theta }{2}\right)x_F+\frac{D_i}{2}\left[\cos \alpha \tan \left(\frac{\theta }{2}\right)+\sin \alpha \right]$

[0184] Coordinates of the point E

[00047]$x_E=-\frac{\frac{\left(\cos \alpha \tan \left(\frac{\theta }{2}\right)-\sin \alpha \right)\left[D_i\sqrt{1-\frac{1}{n^2}{\cos }^2\left(\alpha -\frac{\theta }{2}\right)}-2\frac{e}{n}\cos \left(\alpha -\frac{\theta }{2}\right)\right]}{2\sqrt{1-\frac{1}{n^2}{\cos }^2\left(\alpha -\frac{\theta }{2}\right)}}+w\tan \alpha +h}{\tan \alpha -\tan \frac{\theta }{2}}$

[00048]$y_E=-\tan \left(\alpha \right)\left(x_E+w\right)-h$

EXAMPLES

[0185] FIG. 3 schematically represents the insert and the thermal camera of FIG. 1 with exemplified parameters (example 1) that are influential for the optimized positioning of the camera 9, this is a partial cross-sectional view in a plane P0 passing through the center C of the pupil of the camera and a center O of the insert 2.

[0186] FIGS. 3' and 3"represent diagrams of the lighting of the infrared sensor of the thermal camera, in gray level for the example 1 and a counter-example 1'.

[0187] The parameters are given in table 1.

TABLE-US-00001 θ 24 α 33 n 2.2 e 5 D 20 h 7 w 1 xc -16.5 yc 2.21 N 3 f 6.8 mm p 2.27

[0188] C is placed in the triangle EFC0 with y.sub.C = y.sub.C0 = 2.2 mm and x.sub.C is equal to -16.5 mm.

[0189] C1, the lowest point of the pupil, is on the straight line Dt1 with y.sub.C1 = 1.07 mm

[0190] C2, the highest point of the pupil, is on the straight line Dt1 with y.sub.C2 = 3.34 mm

[0191] The coordinates of E are -11.09; -0.45

[0192] The coordinates of F are -17.27; 3.56

[0193] The abscissa of C0 is x.sub.C0 = -23.6 mm

[0194] As w is positive then T is on the front-end plane of the camera

[0195] The diagram of the lighting of the sensor (from the outside) is uniform (the white is the max illumination from the homogeneous outside).

[0196] In a counter-example 1' with y.sub.C = 0 and it is clearly shown that all the bottom of the image is lost (see black part in the bottom part of FIG. 3").

[0197] In terms of effective lower vertical field of view downward, there is a change from 8° to 12° therefore there is a gain of 4° by placing the camera such that y.sub.C0 = 2.2 mm and not by centering it on the axis X.

[0198] That corresponds to a heightwise vision gain of approximately 2 m for an object/a living being at 30 m from the windshield.

[0199] FIG. 4 schematically represents the insert and the thermal camera of FIG. 1 with exemplified parameters (example 2) that are influential for the optimized positioning of the camera, this is a partial cross-sectional view in a plane P0 passing through the center C of the pupil of the camera and a center O of the insert.

[0200] FIG. 4'represents a diagram of the lighting of the infrared sensor of the thermal camera, in gray level for the example 2.

[0201] With respect to the example 1, only the input datum p is modified and is 5.67 mm, the pupil is too large to fit entirely in the triangle C0FE, centering is optimized to have a maximum fraction of the pupil fit. There is shadow at the top and the bottom of the image on the sensor (see black parts in FIG. 4').

[0202] FIG. 5 schematically represents the insert and the thermal camera of FIG. 1 with exemplified parameters (example 3) that are influential for the optimized positioning of the camera, this is a partial cross-sectional view in a plane P0 passing through the center C of the pupil of the camera and a center O of the insert 2.

[0203] FIG. 5'represents a diagram of the lighting of the infrared sensor of the thermal camera, in gray level for the example 3.

[0204] The parameters are given in table 2

TABLE-US-00002 θ 30° α 33° n 2.2 e 5 mm Di 20 mm h 10 mm w 1 mm x.sub.C -21 mm y.sub.C 2.63 mm N 1.3 f 6.8 mm p 5.23 mm

[0205] The camera is too bulky and has a large θ. That corresponds to the case b) for which the point T is fairly set back and the triangle according to a) (C above Dt1 and under Dt2) no longer exists.

[0206] A choice is made to place C td y.sub.C=y.sub.C0 and as close as possible to the curve Dt1.

[0207] FIG. 5'represents a diagram of the lighting of the infrared sensor of the thermal camera, in gray level for the example 3.

[0208] Although there are dark zones at the top and the bottom of the image, those if have been minimized by the proposed placement. That corresponds also to an equal compromise between shadow at the top and at the bottom.

[0209] FIGS. 6a and 6b respectively represent the variation of the ordinate y and of the negative abscissa x of the points C0, E, F as a function of θ for the case a) and the case b).

[0210] FIGS. 7a and 7b respectively represent the variation of the ordinate y and of the negative abscissa x of the points C0, E, F as a function of Di for the case a) and the case b).

[0211] FIGS. 8a and 8b respectively represent the variation of the ordinate y and of the negative abscissa x of the points C0, E, F as a function of α for the case a) and the case b).

[0212] FIGS. 9a and 9b respectively represent the variation of the ordinate y and of the negative abscissa x of the points C0, E, F as a function of h for the case a) and the case b).

[0213] FIGS. 10a and 10b respectively represent the variation of the ordinate y and of the negative abscissa x of the points C0, E, F as a function of n for the case a).

[0214] The parameters are given in table 3

TABLE-US-00003 θ 24° α 30° n 2.2 e 5 mm Di 20 mm h 7 mm w 1 mm N 3 f 6.8 mm p 2.26 mm

[0215] On each of the graphs of FIGS. 6a to 10b, the point of intersection R (for y) and R' (for x) of the curves gives the moment where the triangle ceases to exist (tilting toward the case b): [0216] when θ is too large, the case b) applies [0217] when Di is too small, the case b) applies [0218] when α is too small, the case b) applies [0219] or when h is too large, the case b) applies.

[0220] In particular, for the case a) on all the graphs: [0221] for C0: y.sub.C0 from 0.8 mm to 3.2 mm and x.sub.C0 -40 mm to -10 mm [0222] for E: y.sub.E<4/3 mm xE at least -20 mm and at most 3 mm [0223] and for F: y.sub.F<7 mm x.sub.F-25 mm to -10 mm.

[0224] for the case b): [0225] y.sub.C0 goes from 1 mm to 3 mm.