Method of image correction for an eye level image projector, and apparatus for performing the method

• US 20030112418A1
• Filed: 12/11/2002
• Published: 06/19/2003
• Est. Priority Date: 12/13/2001
• Status: Active Grant

• Current Assignee: Valeo Vision (Valeo SE)
• Original Assignee: Valeo Vision (Valeo SE)
• Inventors: Albou, Pierre, Leleve, Joel, Coutte, Cyrille
• Granted Patent: US 7,068,240 B2
• Time in Patent Office: Days
• US Class Current: 353/97
• CPC Class Codes: G02B 2027/012 comprising devices for attenuating parasitic image effects
• CPC Class Codes: G02B 2027/014 comprising information/image processing systems
• CPC Class Codes: G02B 27/01 Head-up displays

Abstract

A vehicle has an eye level display for displaying information to the driver by means of images projected on to the windshield and reflected off it. The eye level display system includes means for correcting the image projected, in order substantially to eliminate multiple images. The projected image is corrected essentially by producing a corrected image, in the form of a digital matrix, before it is projected on the windshield by the projector. In one embodiment, the corrective processing step comprises inverting the matrix characteristic of the multiplication caused by the windshield. In another embodiment, it consists in producing a corrected image adaptively by minimising an error function below a predetermined threshold.

Claims

1. A method of image correction for an eye level image projector, comprising the steps of:

producing a digital image in the form of a matrix, each cell of which represents a point on the image to be viewed by projection;

applying a corrective processing step which is dependent on optical and geometrical characteristics of the windshield and which produces a deformation of the projected image, such that the image multiplication effect whereby multiple projection images are produced is reduced; and

the light flux is projected on the windshield.

2. A method according to claim 1, wherein the corrective image processing step consists in shifting, in a direction away from the direction of multiplication of the image, each horizontal line of the matrix produced from a predetermined number of image lines.

3. A method according to claim 1, wherein the corrective processing step consists in producing a corrective matrix calculated by matricular inversion of a matrix characteristic of the image multiplication effect produced by the windshield, and applying a matricular product with the matrix to be displayed, whereby to produce the corrected matrix for projection on the windshield.

4. A method according to claim 3, wherein the corrective processing step further includes a step of shifting values of the corrected matrix in such a way that no value of the matrix is negative.

5. A method according to claim 4, wherein the step of shifting values of the corrected matrix is followed by a step of reducing the dynamic of the corrected matrix.

6. A method according to claim 5, wherein, as a function of the contrasts measured on the corrected matrix, a step of amplification of the contrasts on the image initially generated is performed in such a way as to provide an image for projection having contrasts greater than a predetermined threshold.

7. A method according to claim 2, wherein the corrective processing step consists in producing an error matrix comprising the difference between a matrix (D×

B) simulating the image multiplication effect introduced by the windshield and the matrix (A) effectively generated, and then producing an error criterion and modifying the cells of the matrix (B) of the image to be projected that is in course of being adapted, whereby to minimise the error matrix and/or a scalar measurement of the latter.

8. A method according to claim 7, wherein the step of producing an error criterion consists in projecting the values of the said matrix (D×

B) of simulating the effect of multiplication of the image to be projected, in a range of values between 0 and 1, deducing a scalar error value according to a predetermined function, such as the sum of absolute values of the intervals between the simulation matrix and the matrix to be projected, and modifying the cells of the matrix to be projected in such a way that the scalar error criterion is below a predetermined threshold.

9. A method according to claim 8, wherein each column of the matrix to be projected is, during the process of minimising the error, divided into a plurality of sub-columns in order to reduce the number of components of minimisation.

10. A method according to claim 8, wherein the criterion for minimisation of the error is established in such a way as to have regard to the transitions in the image to be projected, by applying a matricular gradient operator on the image to be projected and testing the minimisation on the gradient of the image to be projected and the gradient of the original image.

11. A method according to claim 10, wherein the step of minimising the criterion comprises calculation of a predetermined linear combination of a distance criterion and a criterion as to the derivatives.

12. A method according to claim 11, wherein the step of calculating the criterion for minimisation of the error comprises a step of calculating the logarithm whereby to take account of the dynamic of the eye.

13. Apparatus for performing a method according to claim 1 by applying the method to an eye level image projector for projecting images on a motor vehicle windshield, comprising:

a generator of images to be projected;

an image corrector for applying a corrective processing step which depends on the optical and geometrical characteristics of the windshield, and for producing a deformation of the projected image such that the multiplication effect in the viewed image is reduced; and

an image projector for projecting the corrected image on the windshield, arranged to receive the image after processing and to produce a light flux to be reflected at least partially towards the windshield.