Pupil detection device

A pupil tracking device, comprising:

• a single light source configured to emit light toward an eyeball in a first brightness value at a first time to form a first reflection spot on the eyeball, and the single light source configured to emit light toward the eyeball in a second brightness value at a second time to form a second reflection spot on the eyeball, wherein the first brightness value is different from the second brightness value, and the first time is different from the second time;
• an image sensor configured to capture a first image containing a brightest region associated with the first reflection spot on the eyeball corresponding to the first brightness value and a second image containing a brightest region associated with the second reflection spot on the eyeball corresponding to the second brightness value, wherein the image sensor is further configured to capture a third image when the single light source is being turned off;
• and
• a processing unit electrically coupled to the image sensor and the single light source, and configured to
• calculate a first differential image between the first image and the third image, and calculate a second differential image between the second image and the third image;
• calculate a differential image by subtracting the second differential image from the first differential image, and
• identify one of two darkest regions in the differential image having a smaller area and corresponding to a position of the brightest region in the first or second differential image as an image of the single light source projected on the eyeball, and the other one of the two darkest regions in the differential image having a larger area as a pupil image.

A pupil tracking device, comprising:

• a single light source configured to emit light toward an eyeball in a first brightness value at a first time to form a first reflection spot on the eyeball, and the single light source configured to emit light toward the eyeball in a second brightness value at a second time to form a second reflection spot on the eyeball, wherein the first brightness value is equal to the second brightness value, and the first time is different from the second time;
• an image sensor configured to capture, using a first exposure time, a first image containing a brightest region associated with the first reflection spot on the eyeball corresponding to the first brightness value and capture, using a second exposure time, a second image containing a brightest region associated with the second reflection spot on the eyeball corresponding to the second brightness value, wherein the first exposure time is different from the second exposure time, wherein the image sensor is further configured to capture a third image when the single light source is being turned off;
• and
• a processing unit electrically coupled to the image sensor and the single light source, and configured to
• calculate a first differential image between the first image and the third image, and calculate a second differential image between the second image and the third image;
• calculate a differential image between the first differential image and the second differential image, and
• identify a darkest region in the differential image as an image of the single light source projected on the eyeball when a position of the darkest region in the differential image corresponds to a position of the brightest region in the first differential image or the brightest region in the second differential image.