Multi-way LED-based surface reflectance sensor and spectrophotometer
First Claim
1. A light sensor comprising:
- a set of light emitting diodes, each light emitting diode configured to emit a corresponding wavelength such that at least one wavelength of one light emitting diode is different than one other wavelength of another light emitting diode; and
a microcontroller, comprising;
a plurality of pairs of I/O pins, there being one pair of I/O pins connected to one corresponding light emitting diode;
means for selectively driving a first subset of the light emitting diodes in a reverse bias to charge a capacitance of the first subset of light emitting diodes; and
means for measuring a time for the capacitance of each of the first subset of light emitting diodes to discharge due to photocurrent induced by incident light on the first subset of light emitting diodes, the time being inversely proportional to an intensity of the incident light.
1 Assignment
0 Petitions
Accused Products
Abstract
A light sensor circuit based on direct connection of LEDs to I/O pins of a microcontroller. The LEDs are reverse biased and the parasitic junction capacitance is charged in an output mode. Then, the I/O pins placed into an high-impedance input mode. The time for the capacitance to be discharged by photoconduction caused by light incident on the LEDs is inversely proportional to an intensity of the incident light, and can be directly measured as the time required for the I/O pin to transition from fully-charged (5 volts) to a logic threshold level (1.7 volts). By using multiple LEDs, multiplexed between emissive and sensing modes, a wide variety of sensors can be constructed, particularly, when the LEDs emit light at different wavelength.
-
Citations
39 Claims
-
1. A light sensor comprising:
-
a set of light emitting diodes, each light emitting diode configured to emit a corresponding wavelength such that at least one wavelength of one light emitting diode is different than one other wavelength of another light emitting diode; and
a microcontroller, comprising;
a plurality of pairs of I/O pins, there being one pair of I/O pins connected to one corresponding light emitting diode;
means for selectively driving a first subset of the light emitting diodes in a reverse bias to charge a capacitance of the first subset of light emitting diodes; and
means for measuring a time for the capacitance of each of the first subset of light emitting diodes to discharge due to photocurrent induced by incident light on the first subset of light emitting diodes, the time being inversely proportional to an intensity of the incident light. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 36, 37, 38, 39)
-
-
35. A method for sensing incident light, comprising the steps of:
-
selecting a set of light emitting diodes having corresponding wavelengths such that at least one wavelength of one light emitting diode is different that one other wavelength of another light emitting diode; and
selectively driving a first subset of the light emitting diodes in a reverse bias to charge a capacitance of the first subset of light emitting diodes; and
measuring a time for the capacitance of each of the first subset of light emitting diodes to discharge due to photocurrent induced by incident light on the first subset of light emitting diodes, the time being inversely proportional to an intensity of the incident light.
-
Specification