Method for modelling an image device, corresponding computer program product and computer-readable carrier medium
A method for modelling an imaging device including an image sensor and an optical system is disclosed. The optical system has an aperture iris diaphragm defining an entrance pupil of the optical system. For a given configuration of the imaging device the method includes estimating a set of characteristic intrinsic parameters of the imaging device, in which a first intrinsic parameter is representative of a distance between the image plane and a sensor conjugated plane conjugated to the image sensor with respect to the optical system; a second intrinsic parameter is representative of a distance between the sensor conjugated plane and the entrance pupil and a third intrinsic parameter is representative of a magnification of the optical system; determining first and second modelling data respectively as a function of the first and third intrinsic parameters and second and third intrinsic parameters; and establishing a model of the imaging device as a function of the second and third modelling data.
1. A method for modelling an imaging device comprising an image sensor and an optical system, the image sensor being disposed in an image plane of the optical system, the optical system comprising an aperture iris diaphragm defining an entrance pupil of the optical system, the method comprising, for a given configuration of said imaging device:
determining a set of characteristic intrinsic parameters of said imaging device, comprising:
a first intrinsic parameter representative of a distance between said image plane and a sensor conjugated plane conjugated to the image sensor with respect to the optical system;
a second intrinsic parameter representative of a distance between said sensor conjugated plane and the entrance pupil;
a third intrinsic parameter representative of a magnification of said optical system;
determining first modelling data as a function of said first and third intrinsic parameters;
determining second modelling data as a function of said second and third intrinsic parameters;
mapping at least a 3D point with associated at least an image point on said image sensor based on a model of the imaging device obtained as a function of said second and third modelling data.
2. The method according to claim 1 , wherein the first modelling data comprises a first invariant distance P x defined between said image plane and a first invariant projection point (p x ) disposed on an optical axis of said imaging device, said first invariant distance P x satisfying the following formula:
P
x
=
Z
M
+
1
with:
Z, the distance between said image plane and said sensor conjugated plane;
M, the magnification of said optical system.
3. The method according to claim 2 , wherein the set of characteristic intrinsic parameters further comprises a fifth intrinsic parameter representative of a position of the optical axis with respect to the image plane.
4. The method according to claim 1 , wherein the second modelling data is a second invariant distance P α defined between said image plane and a second invariant projection point (p α ) located on the optical axis of the imaging device, said second invariant distance P α satisfying the following formula:
P
α
=
D
M
with:
D, the distance between said sensor conjugated plane and the entrance pupil;
M, the magnification of optical system.
5. The method according to claim 1 , wherein the second intrinsic parameter is estimated by calibration.
6. The method according to claim 1 , wherein the second intrinsic parameter is estimated as a function of the first intrinsic parameter and a fourth intrinsic parameter of said set, representative of a distance between said image plane and the entrance pupil.
7. The method according to claim 1 , wherein the set of characteristic intrinsic parameters further comprises a sixth parameter representative of a dimension of the entrance pupil.
8. The method according to claim 1 , wherein the given configuration of said imaging device comprises a setting belonging to the group comprising: a setting of focus, a setting of distance between a principal plane of the optical system and said image plane.
9. Use of a model of an imaging device established by the method according to claim 1 , for determining metric information of a scene imaged by said imaging device.
10. A device for modelling an imaging device comprising an image sensor and an optical system, the image sensor being disposed in an image plane of the optical system, the optical system comprising an aperture iris diaphragm defining an entrance pupil of the optical system, the device comprising, for a given configuration of said imaging device:
estimating unit configured to estimate a set of characteristic intrinsic parameters of said imaging device, comprising:
a first intrinsic parameter representative of a distance between said image plane and a sensor conjugated plane conjugated to the image sensor with respect to the optical system;
a second intrinsic parameter representative of a distance between said sensor conjugated plane and the entrance pupil;
a third intrinsic parameter representative of a magnification of said optical system;
determining unit configured to determine a first modeling data as a function of said first and third intrinsic parameters;
determining unit configured to determine a second modeling data as a function of said second and third intrinsic parameters;
mapping unit configured to map at least a 3D point with associated at least an image point on said image sensor based on a model of the imaging device obtained as a function of said second and third modelling data.
11. The device according to claim 10 , wherein the first modelling data comprises a first invariant distance P x defined between said image plane and a first invariant projection point (p x ) disposed on an optical axis of said imaging device, said first invariant distance P x satisfying the following formula:
P
x
=
Z
M
+
1
with:
Z, the distance between said image plane and said sensor conjugated plane;
M, the magnification of said optical system.
12. The device according to claim 11 , wherein the set of characteristic intrinsic parameters further comprises a fifth intrinsic parameter representative of a position of the optical axis with respect to the image plane.
13. The device according to claim 10 , wherein the second modelling data is a second invariant distance P α defined between said image plane and a second invariant projection point (p α ) located on the optical axis of the imaging device, said second invariant distance P α satisfying the following formula:
P
α
=
D
M
with:
D, the distance between said sensor conjugated plane and the entrance pupil;
M, the magnification of optical system.
14. The device according to claim 10 , wherein the second intrinsic parameter is estimated by calibration.
15. The device according to claim 10 , wherein the second intrinsic parameter is estimated as a function of the first intrinsic parameter and a fourth intrinsic parameter of said set, representative of a distance between said image plane and the entrance pupil.
16. The device according to claim 10 , wherein the set of characteristic intrinsic parameters further comprises a sixth parameter representative of a dimension of the entrance pupil.
17. The device according to claim 10 , wherein the given configuration of said imaging device comprises a setting belonging to the group comprising: a setting of focus, a setting of distance between a principal plane of the optical system and said image plane.