High speed multi-focal camera
A camera captures a visual image of an object in a rapid manner by determining a distance to the object with a time-of-flight sensor and looking up an actuator position for actuating the camera lens to a focus based upon the distance. The actuator position set by the look up table adjusts for temperature effects on focus based upon a temperature measurement associated with the lens. Visual image capture may be accomplished without image-based focus analysis, such as contrast and phase detection autofocus, by validating the distance captured with the time-of-flight sensor.
1 . An information handling system comprising:
a processor operable to execute instructions to process information;
a memory interfaced with the processor and operable to store the instructions and information;
a time-of-flight sensor operable to detect distance to an object;
an image sensor operable to capture light as visual information;
an image signal processor interfaced with the image sensor and operable to define a visual image as an array of pixel values from the visual information;
a lens aligned with the image sensor to direct light at the image sensor;
an actuator coupled to the lens to adjust the lens position relative to the image sensor to focus the light at the image sensor; and
a non-transitory memory storing instructions that when executed cause:
detection by the time-of-flight sensor of a distance to the object;
validation of the distance to the object;
lookup in focal point table of an actuator position associated with focus by the lens on the object for the distance;
actuation of the actuator to the actuator position; and
capture of a visual image at the image sensor by the image signal processor;
wherein the validation comprises analysis of the distance of the time-of-flight sensor compared against expected time-of-flight distances of facial features.
2 . The information handling system of claim 1 further comprising:
a thermistor operable to measure a temperature associated with the lens; and
a temperature adjustment stored in the focal point table to adjust the actuator position based upon the temperature.
3 . The information handling system of claim 2 wherein the capture of the visual image is executed without image-based focus analysis.
4 . The information handling system of claim 1 wherein the validation comprises analysis of a size of the object indicated by the time-of-flight sensor compared against an amount of a field of view of the lens of the object.
5 . The information handling system of claim 1 wherein the instructions further:
select a first actuator position within a first predetermined portion of the lens depth of field;
capture first visual information;
select a second actuator position within a second predetermined portion of the lens depth of field;
capture second visual information; and
compare the first visual information and the second visual information to confirm lens focus.
6 . The information handling system of claim 5 wherein the first visual information and second visual information are compared by contrast detection autofocus.
7 . The information handling system of claim 5 wherein the first visual information and second visual information are compared by phase detection autofocus.
8 . The information handling system of claim 5 wherein:
the first actuator position is one table increment closer than the actuator position associated with focus for the distance; and
the second actuator position is the actuator position associated with focus for the distance.
9 . A method for capturing a visual image with a camera comprising:
detecting by a time-of-flight sensor of a distance to an object;
validating the distance to the object, the validating including at least analysis of a size of the object indicated by the time-of-flight sensor compared against an amount of a field of view of the lens of the object;
looking up in a focal point table of an actuator position associated with focus by a lens on the object for the distance;
actuating of the actuator to the actuator position; and
capturing a visual image at an image sensor by an image signal processor of light passing through the lens focused on the object.
10 . The method of claim 9 further comprising:
measuring a temperature associated with the lens; and
applying a temperature adjustment to the focal point table to determine the actuator position based upon the temperature.
11 . The method of claim 10 further comprising capturing the visual images without image-based focus analysis.
12 . The method of claim 10 further comprising:
selecting a first actuator position within a first predetermined portion of the lens depth of field;
capturing a first visual information;
selecting a second actuator position within a second predetermined portion of the lens depth of field;
capturing a second visual information; and
comparing the first visual information and the second visual information to confirm lens focus.
13 . The method of claim 12 wherein the first visual information and second visual information are compared by contrast detection autofocus.
14 . The method of claim 12 wherein the first visual information and the second visual information are compared by phase detection autofocus.
15 . The method of claim 12 wherein:
the first actuator position is one table increment closer than the actuator position associated with focus for the distance; and
the second actuator position is the actuator position associated with focus for the distance.
16 . A camera comprising:
a time-of-flight sensor operable to detect distance to an object;
an image sensor operable to capture light as visual information;
an image signal processor interfaced with the image sensor and operable to define a visual image as an array of pixel values from the visual information;
a lens aligned with the image sensor to direct light at the image sensor;
an actuator coupled to the lens to adjust the lens position relative to the image sensor to focus the light at the image sensor; and
a non-transitory memory storing instructions that when executed cause:
detection by the time-of-flight sensor of a distance to the object;
validation of the distance to the object;
lookup in focal point table of an actuator position associated with focus by the lens on the object for the distance;
actuation of the actuator to the actuator position; and
capture of a visual image at the image sensor by the image signal processor;
wherein the instructions further:
select a first actuator position within a first predetermined portion of the lens depth of field;
capture first visual information;
select a second actuator position within a second predetermined portion of the lens depth of field;
capture second visual information; and
compare the first visual information and the second visual information by phase detection autofocus to confirm lens focus.
17 . The camera of claim 16 further comprising:
a thermistor operable to measure a temperature associated with the lens; and
a temperature adjustment stored in the focal point table to adjust the actuator position based upon the temperature.
18 . The camera of claim 17 wherein the capture of the visual image is executed without image-based focus analysis.