High-speed analog photon counter and method

• US 8,338,773 B2
• Filed: 09/06/2010
• Issued: 12/25/2012
• Est. Priority Date: 09/06/2010
• Status: Active Grant

• Current Assignee: King Abdullah University of Science and Technology
• Original Assignee: King Abdul AZIZ City For Science and Technology
• Inventors: Eldesouki, Munir, Deen, Mohamed Jamal, Fang, Qiyin
• Primary Examiner(s): NGUYEN, SANG H
• Application Number:
  US12/876,174
• Publication Number:
  US 20120057152A1
• Time in Patent Office: 841 Days
• Field of Search: 356213-235, 250/208.1, 250/214.DC, 250/214.1, 250/214.A, 348/302
• US Class Current: 250/214.A
• CPC Class Codes: G01J 1/46 using a capacitor

Abstract

A high speed analog photon counter and method is provided. In one aspect, the method includes delivering an electric charge to a circuit of the high speed analog photon counter through a current source of the circuit. The method also includes accumulating the electric charge in a capacitor of the circuit electrically coupled to the current source. The method further includes comparing the electric charge accumulated in the capacitor of the circuit with a reference voltage through a comparator of the circuit electrically coupled to an output of the capacitor. The output of the capacitor of the circuit is coupled to an input of the comparator of the circuit, and the reference voltage is coupled to another input of the comparator of the circuit. The method furthermore includes resetting the capacitor of the circuit when the electric charge accumulated in the capacitor of the circuit matches the reference voltage.

Claims

1. A method comprising:

accumulating an electric charge in a capacitor of a circuit electrically coupled to a current source of the circuit;

comparing the electric charge accumulated in the capacitor of the circuit with a reference voltage through a comparator of the circuit electrically coupled to an output of the capacitor to enable accumulation of the electrical charge until an output voltage of the capacitor matches the reference voltage;

generating a reset pulse at an output of the comparator when the output voltage of the capacitor matches the reference voltage;

resetting the capacitor through a first reset transistor of the circuit electrically coupled to the output of the comparator;

clearing the circuit through a second reset transistor configured to receive a signal external to the circuit to clear the circuit; and

implementing the circuit inside a pixel circuit to increase a speed of operation of a measurement device.

2. The method of claim 1, further comprising:

delivering the electric charge to the circuit through the current source;

resetting the capacitor of the circuit when the electric charge accumulated in the capacitor of the circuit matches the reference voltage; and

measuring an intensity of light through the circuit and the comparator of the circuit.

3. The method of claim 1, further comprising:

generating a digital pulse at an output of a photodiode corresponding to a photon incident on the photodiode, wherein the output of the photodiode is coupled to an input of the current source; and

delivering an amount of the electric charge proportional to a pulse width of the digital pulse; and

wherein an increase in the output voltage of the capacitor corresponds to the photon incident on the photodiode.

4. An image sensor device comprising:

a pixel circuit; and

an intensity measurement circuit implemented in the pixel circuitto measure an intensity of light and to increase a speed of operation of the image sensor device, the intensity measurement circuit further comprising;

a first circuit to deliver an electric charge to the intensity measurement circuit through a current source;

a second circuit to accumulate the electric charge in a capacitor of the intensity measurement circuit electrically coupled to the current source; and

a third circuit to compare the electric charge accumulated in the capacitor of the intensity measurement circuit with a reference voltage through a comparator of the intensity measurement circuit electrically coupled to an output of the capacitor,

wherein the capacitor is configured to reset when the electric charge accumulated therein matches the reference voltage,

wherein the comparator is configured to generate a reset pulse at an output of the comparator when the output of the capacitor matches the reference voltage,

wherein the capacitor is configured to reset through a first reset transistor of the intensity measurement circuit electrically coupled to the output of the comparator,

wherein the intensity measurement circuit is configured to reset through a second reset transistor, and

wherein the second reset transistor is configured to receive a signal external to the circuit to clear the circuit.

5. The image sensor device of claim 4, further comprising:

a photodiode external to the intensity measurement circuit to;

generate a digital pulse at an output thereof, wherein the output of the photodiode is electrically coupled to an input of the current source of the intensity measurement circuit, and

deliver an amount of the electric charge proportional to a pulse width of the digital pulse to the intensity measurement circuit through the current source of the intensity measurement circuit.

6. The image sensor device of claim 5,

wherein an increase in the output voltage of the capacitor corresponds to the number of photons incident on the photodiode, and

wherein the photodiode is implemented inside the pixel circuit.

7. The image sensor device of claim 5,

wherein the current source is a voltage controlled current source,

wherein the intensity measurement circuit accumulates the electric charge until an output voltage of the capacitor of the intensity measurement circuit matches the reference voltage at the comparator of the intensity measurement circuit, and

wherein the reference voltage corresponds to a threshold number of counts of photons incident on the photodiode.

8. The image sensor device of claim 4, wherein the intensity measurement circuit is configured to detect photons from n-number of photodiodes through coupling additional current sources between each of the n-number of photodiodes and the intensity measurement circuit when the image sensor device includes n-number of photodiodes such that an input of each current source is coupled to each photodiode and an output of each current source is coupled to the intensity measurement circuit.