System and method for performing optical navigation using a compact optical element
View Patent ↗A system and method for performing optical navigation uses an illumination optical element positioned between a light source and a navigation surface to bend and collimate a beam of light from the light source, which may be originally emitted in a direction normal to the navigation surface. The illumination optical element includes a concave surface to receive the beam of light from the light source and a convex surface to transmit the beam of light from the illumination optical element toward the navigation surface. The beam of light incident on the navigation surface produces light, which is received at an image sensor array to capture frames of image data for displacement estimation.
1. A system for performing optical navigation, the system comprising;
an illumination optical element having a concave surface on a first side and a convex surface on a second side, the first and second sides being opposite sides of the illumination optical element, the illumination optical element being orientated such that that a beam of light is received at the concave surface and transmitted into the illumination optical element and the beam of light is emitted out of the convex surface toward a navigation surface;
an image sensor array positioned to receive light from the beam of light incident on the navigation surface, the image sensor array being configured to capture frames of image data from the received light for displacement estimation; and
an imaging optical element positioned between the navigation surface and the image sensor array,
wherein the imaging optical element is positioned such that the optical axis of the imaging optical element and an axis normal to the navigation surface defines a first plane perpendicular to the navigation surface and an optical axis of the beam of light incident on the navigation surface and an optical axis of the beam of light that is specularly reflected from the navigation surface defines a second plane perpendicular to the navigation surface, where the second plane does not contain the optical axis of the imaging optical element and where the angle between the first plane and the second plane is between approximately eighty to one hundred degrees.
2. The system of claim 1 further comprising a light source configured to emit the beam of light toward the concave surface of the illumination optical element in a direction normal to the navigation surface.
3. The system of claim 2 wherein the concave surface of the illumination optical element is a concave spherical surface to deflect and expand the beam of light.
4. The system of claim 3 wherein the convex surface of the illumination optical element is an ellipsoidal surface.
5. The system of claim 4 wherein the illumination optical element is configured such that the major axis of the ellipsoidal surface intersects a virtual image point that lies on an R/n sphere having a center at the center of the concave surface and on a line between the center of the concave surface and a point from which the beam of light originated, where R is the radius of the concave surface and n is the index of refraction of the illumination optical element.
6. The system of claim 5 wherein the illumination optical element is configured such that the angle between the major axis of the ellipsoidal surface and the normal of the navigation surface is twice the deflection angle of the concave surface.
7. The system of claim 1 wherein the imaging optical element is positioned such that the optical axis of the imaging optical element is tilted by an angle from the normal of the navigation surface that is equivalent to the angle between the major axis of the ellipsoidal surface and the normal of the navigation surface.
8. A method for performing optical navigation, the method comprising;
emitting a beam of light from a light source;
receiving the beam of light at a concave surface of an illumination optical element;
deflecting the beam of light at the concave surface of the illumination optical element by a first angle;
refracting the beam of light from the concave surface at a convex surface of the illumination optical element by a second angle, including collimating the beam of light at the convex surface;
emitting the beam of light out of the convex surface toward a navigation surface;
receiving light from the beam of light incident on the navigation surface at an image sensor array to capture frames of image data from the received light for displacement estimation; and
receiving the light from the navigation surface at an imaging optical element positioned between the navigation surface and the image sensor array,
wherein the receiving the light from the navigation surface at the imaging optical element includes receiving the light from the navigation surface at the imaging optical element that is positioned such that the optical axis of the imaging optical element and an axis normal to the navigation surface defines a first plane perpendicular to the navigation surface and an optical axis of the beam of light incident on the navigation surface and an optical axis of the beam of light that is specularly reflected from the navigation surface defines a second plane perpendicular to the navigation surface, where the second plane does not contain the optical axis of the imaging optical element and where the angle between the first plane and the second plane is between approximately eighty to one hundred degrees.
9. The method of claim 8 wherein the emitting the beam of light includes emitting the beam of light from the light source toward the concave surface of the illumination optical element in a direction normal to the navigation surface.
10. The method of claim 9 wherein the concave surface of the illumination optical element is a concave spherical surface to deflect and expand the beam of light.
11. The method of claim 10 wherein the convex surface of the illumination optical element is an ellipsoidal surface.
12. The method of claim 11 wherein the refracting the beam of light includes refracting the beam of light from the concave surface at the convex surface of the illumination optical element in a direction parallel to the major axis of the ellipsoidal surface.
13. The method of claim 12 wherein the refracting the beam of light includes refracting the beam of light from the concave surface at the convex surface of the illumination optical element by the second angle that is twice the first angle.
14. A system for performing optical navigation, the system comprising;
a light source configured to emit a beam of light toward a navigation surface in a direction normal to the navigation surface;
an illumination optical element having a concave surface on a first side and a convex surface on a second side, the first and second sides being opposites sides of the illumination optical element, the illumination optical element being orientated such that that the beam of light from the lights source is received at the concave surface and transmitted into the illumination optical element and the beam of light is emitted out of the convex surface toward a navigation surface; and
an image sensor array positioned to receive light from the beam of light incident on the navigation surface, the image sensor array being configured to capture produce frames of image data from the received light, the frame of image data being used for displacement estimation; and
an imaging optical element positioned between the navigation surface and the image sensor array,
wherein the imaging optical element is positioned such that the optical axis of the imaging optical element and an axis normal to the navigation surface defines a first plane perpendicular to the navigation surface and an optical axis of the beam of light incident on the navigation surface and an optical axis of the beam of light that is specularly reflected from the navigation surface defines a second plane perpendicular to the navigation surface, where the second plane does not contain the optical axis of the imaging optical element and where the angle between the first plane and the second plane is between approximately eighty to one hundred degrees.
15. The system of claim 14 wherein the concave surface of the illumination optical element is a concave spherical surface and wherein the convex surface of the illumination optical element is an ellipsoidal surface.
16. The system of claim 15 wherein the illumination optical element is configured such that the major axis of the ellipsoidal surface intersects a virtual image point that lies on an R/n sphere having a center at the center of the concave surface and on a line between the center of the concave surface and a point from which the beam of light originated, where R is the radius of the concave surface and n is the index of refraction of the illumination optical element.
17. The system of claim 1 wherein the angle between the first plane and the second plane is approximately ninety degrees.
18. The method of claim 8 wherein the angle between the first plane and the second plane is approximately ninety degrees.
19. The system of claim 14 wherein the angle between the first plane and the second plane is approximately ninety degrees.