Patent Application
20190289188
The present invention generally relates to an image sensor, and more particularly to a system and method of adjusting power of a light-emitting device by an image sensor.
Structured-light (SL) projector is commonly used to project a known pattern on to a scene. The structure-light projector may be adopted in a three-dimensional (3D) scanning system for measuring 3D shape of an object. The SL projector may emit invisible (e.g., infrared or IR) structured light without interfering with other computer vision tasks (or human vision look and feel).
The power of a light-emitting device (e.g., IR light-emitting device) of the SL projector is commonly controlled with both a proximity sensor and an ambient light sensor. The proximity sensor is a sensor capable of detecting presence of nearby objects without any physical contact.
The ambient light sensor is a sensor capable of detecting ambient light power (or energy).
The proximity sensor and the ambient light sensor used to control the power of light-emitting device of the SL projector incur design complexity, high power consumption and cost. Moreover, there may be a lack of proximity sensor and ambient light sensor made specifically for a certain range of infrared spectrum. A need has thus arisen to propose a novel scheme of adjusting power of a light-emitting device without using conventional proximity sensor and ambient light sensor.
In view of the foregoing, it is an object of the embodiment of the present invention to provide a system and method of adjusting power of an infrared (IR) light-emitting device without using conventional proximity sensor and ambient light sensor but with a single IR sensor, thus substantially reducing design complexity, power consumption and cost.
According to one embodiment, a system of adjusting power of a light source includes an image sensor, a target object detection unit, a distance determination unit, a light energy measuring unit and a controller. The image sensor captures an image and obtains gain and exposure. The target object detection unit detects a target object in the image and finds a size of the target object. The distance determination unit determines distance of the target object according to the size of the target object. The light energy measuring unit measures light energy according to the gain and the exposure. The controller controllably adjusts power of the light source according to the distance and the light energy.
In the embodiment, the system 100 may include an IR sensor (or an image sensor in general) 11 capable of detecting infrared light in a specific range (e.g., atmospheric window around 940 nm) of infrared spectrum. The IR sensor 11 of the embodiment may include, but not limited to, a complementary metal-oxide-semiconductor (CMOS) image sensor or CIS.
In step 21, the IR sensor 11 operatively captures an IR image (or an image in general). In the embodiment, the resolution of the IR image may, for example, be 640×480 (i.e., Video Graphics Array (VGA)) or 320×240 (i.e., Quarter Video Graphics Array (QVGA)). Specifically, the IR sensor 11 captures the IR image in automatic exposure (AE) mode. The task of capturing the IR image may obtain gain (e.g., automatic gain in this case) that represents amplification of signal from the IR sensor 11, and exposure that represents amount of light per unit area reaching the IR sensor 11. The use of the gain and the exposure will be explained later in this specification.
The system 100 of the embodiment may include a target object detection unit 12 configured to detect (or identify) a target object in the IR image (step 22). The task of detecting the target object may find a location and a size of the target object.
The system 100 of the embodiment may include a distance determination unit 13 configured to determine distance of the target object (from the IR sensor 11) according to the size of the target object in the IR image (step 23).
In the embodiment, the system 100 may include a light energy measuring unit 14 configured, in step 24, to measure (environmental) IR light energy according to the gain and the exposure obtained in step 21. Specifically, in the embodiment, the measured IR light energy is related to a product (or multiplication) of the gain and the exposure (i.e., gain*exposure). Particularly, the measured IR light energy is inversely proportional to the product of the gain and the exposure.
The light energy measuring unit 14 of the embodiment may include a band-pass filter configured to pass wavelengths (or frequencies) within a specific range (e.g., atmospheric window around 940 nm) of infrared spectrum, and to reject (or attenuate) wavelengths outside that range.
In the embodiment, the system 100 may include a controller 15 that operatively receives the determined distance (from the distance determination unit 13) and the measured light energy (from the light energy measuring unit 14), according to which the controller 15 may controllably adjust power of the IR light-emitting device 10, for example, of a SL projector (step 25). That is, the farther is the distance or higher is the light energy, more power is fed to the IR light-emitting device 10. According to the embodiment as discussed above, the system 100 and the method 200 can determine proximity and ambient light without using conventional proximity sensor and ambient light sensor but with a single IR sensor, thus substantially reducing design complexity, power consumption and cost.
Although specific embodiments have been illustrated and described, it will be appreciated by those skilled in the art that various modifications may be made without departing from the scope of the present invention, which is intended to be limited solely by the appended claims.
