Light-to-digital converter

Patent metadata

Field	Value
Publication number	US-11864876-B2
Application number	US-202016886714-A
Country	US
Kind code	B2
Filing date	May 28, 2020
Priority date	May 29, 2019
Publication date	Jan 9, 2024
Grant date	Jan 9, 2024

Abstract

A light-to-digital converter (2) comprises a light-to-current converter (10); a current integrator (4) with an integrator output (30) resettable to a baseline level; and a counter (18) with a digital output (26), wherein the light-to-current converter (10) is switchably connectable as a positive integration input to the current integrator (4), for, during a light-collecting phase (404-406), integrating a current from the light-to-current converter (10), the integrator output (30) starting from the baseline value and ending at a value to be digitized; a reference current source (14) is switchably connectable as a negative integration input to the current integrator (4), for, during a counting phase (406-408) subsequent to the light-collecting phase (404-406), integrating a reference current from the reference current source (14), the integrator output (30) starting from the value to be digitized and ending at the baseline value, the time spent integrating the reference current corresponding to the value to be digitized; and the counter (18) is configured for measuring the time.

First claim

The invention claimed is:

1. A light-to-digital converter, comprising:
a light-to-current converter;
a current integrator with an integrator output resettable to a baseline value;
and a counter with a digital output, wherein:
said light-to-current converter is arranged to be connected as a positive integration input to said current integrator during a light-collecting phase, said current integrator integrating a current resulting from light-to-current conversion at said light-to-current converter, said integrator output starting from said baseline value and ending at a value to be digitized;
a reference current source is arranged to be connected as a negative integration input to said current integrator during a counting phase subsequent to said light-collecting phase, integrating a reference current from said reference current source, said integrator output starting from said value to be digitized and ending at said baseline value, a time spent integrating said reference current corresponding to said value to be digitized; and
said counter is configured for measuring said time and outputting a count corresponding to said value to be digitized.

2. The light-to-digital converter of claim 1 , further comprising a comparator configured to compare said integrator output with a reference level corresponding to said baseline value, wherein an output of said comparator is connected to said counter.

3. The light-to-digital converter of claim 1 , further comprising said reference current source.

4. The light-to-digital converter of claim 1 , wherein said reference current is a constant current.

5. The light-to-digital converter of claim 1 , wherein said light-to-current converter comprises a photodiode.

6. The light-to-digital converter of claim 1 , wherein said light-to-current converter comprises a photomultiplier.

7. The light-to-digital converter of claim 1 , wherein said current integrator is a single-ended integrator with a capacitor as a feedback component.

8. The light-to-digital converter of claim 1 , wherein said current integrator is a differential integrator with a pair of capacitors as feedback components.

9. The light-to-digital converter of claim 1 , wherein said current integrator is based on current-sensing circuitry.

10. A photoplethysmogram, PPG, system comprising the light-to-digital converter of claim 1 .

11. A functional near-infrared spectroscopy, fNIRS, system comprising the light-to-digital converter of claim 1 .

12. A method of light-to-digital conversion, comprising:
during a light-collecting phase, a current integrator, having an integrator output, integrating a current resulting from light-to-current conversion at a light-to-current converter connected as a positive integration input, said integrator output starting from a baseline value and ending at a value to be digitized; and, thereafter,
in a counting phase, said current integrator integrating a reference current connected as a negative integration input, said integrator output starting from said value to be digitized and ending at said baseline value, a time spent integrating said reference current corresponding to said value to be digitized, wherein a counter, providing a digital output, measures said time and outputs a count corresponding to said value to be digitized.

Assignees

• Imec Vzw
• Univ Leuven Kath
• Stichting Imec Nederland
• Katholieke Univ Leuven Ku Leuven

Inventors

• Lin Qiuyang
• Xu Jiawei
• Song Shuang
• Van Helleputte Nick
• Tavernier Filip

Classifications

• A61B5/02427 Primary

  Details of sensor · CPC title

• A61B5/0042

  for the brain · CPC title

• A61B5/0075

  by spectroscopy, i.e. measuring spectra, e.g. Raman spectroscopy, infrared absorption spectroscopy (A61B5/0071 takes precedence) · CPC title

• A61B5/6826

  Finger · CPC title

• G01J1/44

  Electric circuits {(for command of an exposure part G03B7/02)} · CPC title