Camera with through-the-lens lighting

• US 6,445,884 B1
• Filed: 02/16/1999
• Issued: 09/03/2002
• Est. Priority Date: 06/22/1995
• Status: Expired due to Fees

• Current Assignee: Microsoft International Holdings BV (Microsoft Corporation)
• Original Assignee: 3DV Systems Ltd. (Microsoft Corporation)
• Inventors: Yahav, Giora
• Primary Examiner(s): Gray, David M.
• Application Number:
  US09/250,322
• Time in Patent Office: 1,295 Days
• Field of Search: 348/370, 356/1-5, 356/141, 356/152, 356/407, 356/4.01, 356/4.07, 356/5.01, 356/5.02, 356/5.03, 396/106-110, 396/429, 396/431, 396/155, 396/176
• US Class Current: 396/106
• CPC Class Codes: B60Q 2400/50 Projected symbol or information, e.g. onto the road or car body
• CPC Class Codes: B60Q 9/008 for anti-collision purposes
• CPC Class Codes: F21S 41/141 Light emitting diodes [LED]
• CPC Class Codes: F21S 41/147 the main emission direction of the LED being angled to the optical axis of the illuminating device
• CPC Class Codes: F21S 41/663 by switching light sources by switching incandescent light sources F21S41/162
• CPC Class Codes: G01C 11/025 by scanning the object
• CPC Class Codes: G01S 17/08 for measuring distance only indirect measurement G01S17/46; active triangulation systems G01S17/48
• CPC Class Codes: G01S 17/18 wherein range gates are used
• CPC Class Codes: G01S 17/88 Lidar systems specially adapted for specific applications
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/4812 transmitted and received beams following a coaxial path
• CPC Class Codes: G01S 7/51 Display arrangements
• CPC Class Codes: G02B 7/32 using active means, e.g. light emitter including both an active and a passive focus detecting device G02B7/285; using ultrasound G02B7/40
• CPC Class Codes: H04N 23/56 provided with illuminating means
• CPC Class Codes: H04N 23/74 by influencing the scene brightness using illuminating means

Abstract

A camera is provided with through the lens lighting. An light source provides boresighted illumination by using a beamsplitter or mirror to illuminate a field of view which is congruent with the field of view of the image sensor of the camera. The light source can be an extended light source having a dimensions about equal to the image sensor. The surface of the image sensor, the light source or the beam splitter can be modulated such that light directly from the light source does not impinge the sensor.

Claims

1. A camera with through-the-lens lighting, comprising:

a modulated light source;

a photosensitive surface;

focusing optics, having an optical axis, that forms an image of a scene, within a field of view, on the photosensitive surface, wherein light from the light source is boresighted with the optical axis and directed toward the scene, illuminating substantially only the field of view of the camera;

a modulator which modulates radiation striking the photosensitive surface or the sensitivity of the photosensitive surface, wherein the modulator does not modulate the light source; and

a controller, controlling the modulator and the modulation of the light-source, to block a reaction of the photosensitive surface whenever the modulated source of light is on, while insuring that all the desired radiation reflected from the scene is collected.

2. A camera according to claim 1 and including a collimating lens which collimates the light.

3. A camera according to claim 1 wherein the light is coherent.

4. A camera according to claim 2 wherein the light is coherent.

5. A camera according to claim 1 wherein the light is incoherent.

6. A camera according to claim 2 wherein the light source is incoherent.

7. A camera according to any of claims 1-6, wherein the camera is an optical ranging camera, wherein only a desired, gated portion of the reflected radiation from the scene is collected and wherein intensity values of the image are indicative of distances of objects from the camera.

8. A camera according to any of claims 1-6, wherein the focusing optics comprises telecentric optics which collimates also reflected radiation from the scene.

9. A camera according to claim 7, wherein the focusing optics comprises telecentric optics which collimates also reflected radiation from the scene.

10. A camera according to any of claims 1-6 wherein the modulator is operative to vary the sensitivity of the photosensitive surface.

11. A camera according to any of claims 1-6, wherein the modulator modulates radiation striking the photosensitive surface and transmits substantially all the reflected radiation from the scene that reaches the camera.

12. A camera according to any of claims 1-6 wherein the source and photosensitive surface have substantially equivalent optical extents, so that light emerges through the lens, illuminating substantially only the field of view of the camera.

13. A camera according to any of claims 1-6 wherein the light source has an extended area from which light is radiated and comprising a variable-aperture iris adjacent to the extended area and wherein the aperture size controls the extent of the illuminated field of view.

28. A method according to any of claims 28-30 or 35, wherein modulating activation of the photosensitive surface in synchrony with the beam comprises:

estimating the amount of light reflected from different portions of the scene which reaches the camera from various parts of the scene;

modulating the light source with a multiple-pulse function of square pulses having a duration of δ

₁ seconds each, δ

₂ seconds apart, wherein δ

₁ and δ

₂ are determined responsive to said estimate and during δ

₁, light is transmitted and during δ

₂, light is blocked; and

modulating activation of the photosensitive surface with a multiple-pulse function of square pulses so that during δ

₁, the surface is not sensitive to light and during at least part of δ

₂, the surface is sensitive to light, so as to adjust the range of light reaching various portions of the photosensitive surface.

29. A camera according to any of claims 1-6 wherein the controller controls the modulation of the light source so that the light source provides a plurality of light pulses such that a total desired amount of light reaches the photosensitive surface from the scene.

14. A method of creating an image with through-the-lens lighting comprising:

boresighting a beam of incoherent light with the optical axis of a camera, having a field of view;

illuminating a scene with the beam of incoherent light, emerging from the camera along the optical axis, such that a region illuminated by the beam is substantially congruent with the field of view of the camera; and

creating an image on a photosensitive surface of the camera using light from the boresighted light that is reflected from the scene that is collected by the camera.

18. A method according to any of claim 14-17 and including collimating the beam.

15. A method of creating an image with through-the-lens lighting comprising:

providing a modulated beam of light;

boresighting the beam with an optical axis of a camera having a field of view;

illuminating a scene with the beam, emerging from the camera, such that substantially only the field of view of the camera is illuminated;

modulating the activation of a photosensitive surface of the camera in synchrony with the beam modulation, such that light is blocked from activating the photosensitive surface whenever the beam is on, while insuring that all the desired reflected radiation from the scene is collected on the photosensitive surface; and

creating an image on the photosensitive surface using the collected light.

16. A method according to claim 15 wherein modulating the activation comprises blocking light from incidence on the photosensitive surface.

17. A method according to claim 15 wherein modulating the activation comprises modulating the sensitivity of the photosensitive surface.

22. A method according to any of claims 15-17 or 21, wherein modulating activation of the photosensitive surface in synchrony with the beam comprises:

estimating the average distance to the scene and the depth of scene;

modulating the light source with a multiple-pulse function of square pulses having a duration of δ

₁ seconds each, δ

₂ seconds apart, wherein during δ

₁, light is transmitted and during δ

₂, light is blocked;

modulating activation of the photosensitive surface with a multiple-pulse function of square pulses so that during δ

₁, the surface is not sensitive to light and during at least part of δ

₂, the surface is sensitive to light; and

determining δ

₁ and δ

₂ responsive the average distance and depth of scene.

23. A method according to claim 22 wherein the duration of the light pulse, is shorter than twice the time taken for light to propagate to the scene and wherein δ

₁+δ

₂, the time for a complete modulation cycle, is greater than the total time for light to propagate to the scene and for reflected radiation from all points on the scene to be recovered.

24. A method according to claim 22 wherein estimating comprises:

focusing the camera on the scene using the camera'"'"'s focusing optics;

determining the distance to a point of optimum focus based on the setting of the focusing optics;

determining the depth of field of the focusing optics for that setting;

estimating the distance to scene based on the distance to a point of optimum focus; and

estimating the depth of the scene based on the depth of field of the focusing optics for that setting.

25. A method according to claim 22 wherein estimating comprises:

setting the camera to a range-determining mode;

varying the modulation function; and

using the first few images to estimate the distance to the scene and the depth of the scene.

26. A method according to claim 22 wherein a number of pulses of light illuminates the scene to provide a desired illumination thereof, said desired illumination being based at least in part on the determined distance.

27. A method according to claim 22 wherein estimating comprises setting the value of distance to the scene plus the depth of the scene to be equal to the range of the light source.

19. A method of creating an image with through-the-lens lighting comprising:

providing a beam of light, emanating from an extended source, internal to a camera;

boresighting the beam with an optical axis of the camera; and

illuminating a scene with the beam, emerging from the camera, such that the beam illuminates a region substantially congrugent with the field of view of the camera;

modulating the beam;

modulating activation of a photosensitive surface of the camera in synchrony with the beam modulation, blocking light from activating the photosensitive surface whenever the beam is on, while insuring that all the desired reflected radiation from the scene is collected and;

creating an image on the photosensitive surface of the camera using boresighted light that is reflected from the scene that is collected by the camera.

20. A method according to claim 19 wherein modulating the activation comprises blocking light from reaching the photosensitive surface.

21. A method according to claim 19 wherein modulating the activation comprises modulating the sensitivity of the photosensitive surface.