Anti-aliasing photodetector system

Patent metadata

Field	Value
Publication number	US-9909922-B2
Application number	US-201514844383-A
Country	US
Kind code	B2
Filing date	Sep 3, 2015
Priority date	Sep 3, 2015
Publication date	Mar 6, 2018
Grant date	Mar 6, 2018

Abstract

An anti-aliasing photodetector system for a powered ophthalmic device, such as a contact lens, may be utilized for any number of functions. The anti-aliasing photodetector system converts current from an array of photodetectors into a voltage for use in other aspects of the powered ophthalmic device. The anti-aliasing photodetector system comprises a photodiode array including a plurality of individual photodiodes, an integrate-and-hold circuit, including a capacitor and switch to convert current to voltage, and an analog-to-digital converter. The anti-aliasing photodetector system provides for low power consumption, a wide dynamic range, noise rejection, and is capable of detecting incident ambient visible light as well as incident infrared light.

First claim

What is claimed is:

1. A powered ophthalmic device comprising:
a first sensor including one or more photodiodes producing a first output current;
a first integrator receiving the first output current and converting it to a first output voltage, wherein the first integrator comprises a first switch and a first capacitor, and is configured to integrate the first output current over a predetermined integration period of time;
an analog-to-digital converter configured to receive the first output voltage and to provide a digital output signal based on the first output voltage;
a second sensor containing one or more photodiodes producing a second output current;
a second integrator receiving the second output current and converting it to a second output voltage, wherein the second integrator comprises a third switch and a second capacitor, and is configured to integrate the second output current over the predetermined integration period of time;
a light-blocking element configured to block substantially all incident light from reaching the second sensor;
a first output voltage switch configured to selectively couple the first output voltage to the analog-to-digital converter;
a first digital register configured to selectively receive a digital output of the analog-to-digital converter or to hold a stored value, the stored value being based on the digital output of the analog-to-digital converter at an earlier time;
a second output voltage switch configured to selectively couple the second output voltage to the analog-to-digital converter; and
a digital subtractor coupled to the first digital register and to the analog-to-digital converter.

2. The powered ophthalmic device according to claim 1 , wherein a component of the first output current from the photodiodes of the first sensor is proportional to incident light.

3. The powered ophthalmic device according to claim 1 , wherein the predetermined integration period of time is a function of a period of an undesired signal.

4. The powered ophthalmic device according to claim 1 further comprising a reference voltage source, and wherein the first switch is configured to selectively couple the first capacitor to the voltage reference source.

5. The powered ophthalmic device according to claim 1 , wherein the first sensor is further configured to firstly close the first switch to precharge the first capacitor for a precharge time interval and then to secondly open the first switch for a predetermined integration period of time.

6. The powered ophthalmic device according to claim 1 , wherein the one or more photodiodes of the first sensor are selectively coupled to the first capacitor such that the gain and/or sensitivity of the first sensor can be varied.

7. The powered ophthalmic device according to claim 6 , wherein the selective coupling of the one or more photodiodes of the first sensor is based on a function of the output voltage.

8. The powered ophthalmic device according to claim 1 , wherein the first integrator further comprises a second switch configured to selectively couple the capacitor to the one or more photodiodes of the first sensor such that the output voltage of the integrator is held for a predetermined hold period of time.

Assignees

• Johnson & Johnson Vision Care

Inventors

• Schweickert Robert Karl
• Hoggarth Steven Phillip
• Barrows Corey Kenneth
• Humphreys Scott Robert
• Toner Adam Walter
• Pugh Randall Braxton

Classifications

• H04N25/76

  Addressed sensors, e.g. MOS or CMOS sensors · CPC title

• H04N25/63

  applied to dark current · CPC title

• G01J1/4228

  arrangements with two or more detectors, e.g. for sensitivity compensation · CPC title

• H04N5/374

  Electricity · mapped topic

• G02C7/049 Primary

  Contact lenses having special fitting or structural features achieved by special materials or material structures · CPC title