Time of flight sensing for brightness and autofocus control in image projection devices

Patent metadata

Field	Value
Publication number	US-2018091784-A1
Application number	US-201615280171-A
Country	US
Kind code	A1
Filing date	Sep 29, 2016
Priority date	Sep 29, 2016
Publication date	Mar 29, 2018
Grant date	—

Abstract

An image projection device, such as a pico projector or LCD projector, includes image projection circuitry configured to generate a light beam having a power. The image projection circuitry projects the light beam onto and focuses the light beam on a projection surface located an imaging distance from the image projection circuitry. A time-of-flight sensor is configured to sense the imaging distance between the image projection circuitry and the projection surface and to generate an imaging distance signal indicating the sensed imaging distance. Control circuitry is coupled to the image projection circuitry and to the time-of-flight sensor and is configured to adjust the power and the focus of the light beam based upon the imaging distance signal.

First claim

1 . An image projection device, comprising:
image projection circuitry configured to generate a light beam having a power, and to project the light beam onto and focus the light beam on a projection surface located an imaging distance from the image projection circuitry; a time-of-flight sensor configured to sense the imaging distance between the image projection circuitry and the projection surface, and to generate an imaging distance signal based on the sensed imaging distance; and control circuitry coupled to the image projection circuitry and to the time-of-flight sensor, the control circuitry configured to adjust the power and the focus of the light beam based upon the imaging distance signal.

2 . The image projection device of claim 1 , wherein the time-of-flight sensor is further configured to sense a level of ambient light incident upon the time-of-flight sensor and to generate an ambient light signal based on the sensed level of ambient light, and wherein the control circuitry is further configured adjust the power of the light beam based upon the ambient light signal.

3 . The image projection device of claim 1 , wherein the control circuitry is further configured to adjust the power of the light beam to a power interrupt threshold in response to the imaging distance signal reaching a minimum distance threshold.

4 . The image projection device of claim 1 , wherein the image projection circuitry comprises an optical engine including a plurality of laser diodes.

5 . The image projection device of claim 1 , wherein the control circuitry further comprises a look-up table including a plurality of focus and imaging distance values, each focus being associated a corresponding imaging distance value and wherein the control circuitry is configured to adjust the focus of the light beam using the focus value associated with imaging distance value indicated by the imaging distance signal.

6 . The image projection device of claim 1 , wherein the time-of-flight sensor comprises a single zone single photon avalanche diode array.

7 . The image projection device of claim 6 , wherein the control circuitry is further configured to calculate an average of the imaging distance signal over time to generate an average imaging distance value, and is further configured to adjust the focus of the light beam based on the average imaging distance value.

8 . The image projection device of claim 1 , wherein the time-of-flight sensor comprises a multi zone single photon avalanche diode array.

9 . The image projection device of claim 8 ,
wherein the imaging projection circuitry is configured to project the light beam onto the projection surface within an image projection field of view on the projection surface to generate a projected image in the image projection field of view; wherein the time-of-flight sensor is further configured to project the light beam to generate a plurality of projection patterns, each projection pattern being projected onto a respective one of a plurality of spatial zones on the projection surface; wherein the multi zone photon avalanche diode array includes a plurality of array zones, each of the plurality of array zones being configured to sense reflection of the projected light beam off a corresponding one of the plurality of spatial zones, and the multi zone photon avalanche diode array configured to generate for each of the plurality array zones a corresponding zone sensed event signal based on the sensed reflection of the projected light beam off the corresponding spatial zone; and wherein the time-of-fight sensor is configured to generate a plurality of zone imaging distance signals, each of the plurality of zone imaging distance signals being based upon the zone sensed event signal of a corresponding one of the plurality of array zones and indicating an imaging distance between the time-of-flight sensor and the corresponding one of the plurality of spatial zones.

10 . The image projection device of claim 9 , wherein the control circuitry is configured to control the image projection circuitry to adjust the focus of the projected image based upon the plurality of zone imaging distance signals.

11 . The image projection device of claim 10 , wherein the control circuitry is configured to control the image projection circuitry to adjust the focus through digital keystone correction.

12 . The image projection device of claim 10 , wherein the image projection circuitry further comprises an adjustable projection lens configured to adjust the focus of the projected image based upon a focus adjustment signal, and wherein the control circuitry is configured to generate the focus adjustment signal based upon the plurality of zone imaging distance signals to adjust the focus of the projected image.

13 . The image projection device of claim 9 , wherein the plurality of spatial zones includes a plurality of spatial zones arranged in rows and columns within a field of view of the time-of-flight sensor.

14 . The image projection device of claim 13 , wherein each row of spatial zones includes the same number of spatial zones and each column of spatial zones includes the same number of columns.

15 . The image projection device of claim 13 , wherein the time-of-flight sensor field of view is approximately the same as the image projection field of view.

16 . A method of controlling a projected light beam, the method comprising:
projecting an image onto a projection surface positioned at an imaging distance, the image having a brightness; transmitting an optical signal onto a spatial zone on the projection surface; sensing a reflected optical signal that is reflected off the spatial zone responsive to the transmitted optical signal; determining the imaging distance based upon time-of-flight measurements of the transmitted and reflected optical signals; controlling the brightness of the projected image based upon the determined imaging distance; and focusing the projected image based upon the determined imaging distance.

17 . The method of claim 16 further comprising:
sensing a level of ambient light based upon time-of-flight measurements of the transmitted and reflected optical signals; and
controlling the brightness of the projected image based upon the sensed level of ambient light.

18 . The method of claim 16 further comprising:
determining whether the imaging distance has reached a minimum distance threshold; and
reducing the brightness of the projected image to a brightness interrupt threshold in response to the imaging distance reaching the minimum distance threshold.

19 . The method of claim 16 , wherein transmitting an optical signal onto a spatial zone on the projection surface comprises transmitting an infrared optical signal onto the spatial zone.

20 . The method of claim 16 , wherein controlling the brightness of the projected image based upon the determined imaging distance comprises increasing and decreasing the brightness of the projected image as a linear function of the determined imaging distance.

21 . An image projection device, comprising:
image projection circuitry configured to generate a light beam and to project the light beam onto a projection surface located an imaging distance from the image projection circuitry; a time-of-flight sensor configured to sense the imaging distance between the image projection circuitry and the projection surface, and to generate an imaging distance signal based on the sensed imaging distance; and control cir

Assignees

• St Microelectronics Res & Dev Ltd
• St Microelectronics Inc

Inventors

• Dutton Neale
• Yang Xiaoyong
• Channon Kevin

Classifications

• G01S7/4865

  Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak (peak detection in noise, signal conditioning G01S7/487) · CPC title

• H04N9/315

  Modulator illumination systems (general applications of lighting devices F21V; general optical systems G02B; lamp houses for projectors not peculiar to the presence of an electronic spatial light modulator G03B21/20) · CPC title

• G01S17/10

  using transmission of interrupted, pulse-modulated waves (determination of distance by phase measurements G01S17/32) · CPC title

• H04N9/3155 Primary

  for controlling the light source (light source control per se H05B35/00 – H05B47/00; control of an illumination source for displays in general G09G3/3406) · CPC title

• H04N9/3185

  Geometric adjustment, e.g. keystone or convergence (optical or mechanical adjustment of convergence H04N9/317; using scanning means H04N3/22; optical or mechanical adjustments of projectors not peculiar to the presence of an electronic spatial light modulator G03B21/14) · CPC title