# US 11,307,136 B2 · Light sensor and decay-time scanner

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- Number: US 11,307,136 B2
- Document ID: US11307136B2
- Status: Granted
- Kind: B2
- Application number: 16/956,932
- Filed: 2018-12-13
- Published: 2020-12-17
- Granted: 2022-04-19
- Earliest claimed: 2017-12-22
- Assignees: Sicpa Holding SA
- Applicants: Sicpa Holding SA
- Inventors: Frédéric Pierson; Joël Bonny; Samuel Brügger; Daniel Zahnd
- Web page: https://patentgrep.com/patent/US11307136B2

## CPC

- G01N 21/27: using photo-electric detection (G01N21/31 takes precedence){; circuits for computing concentration (logarithmic circuits G06G7/24; photometric circuits in general G01J)}
- H03F 3/087: {with IC amplifier blocks (H03F3/085 takes precedence)}
- G06K 19/06112: {the marking being simulated using a light source, e.g. a barcode shown on a display or a laser beam with time-varying intensity profile}
- G06K 19/0614: {the marking being selective to wavelength, e.g. color barcode or barcodes only visible under UV or IR (methods or arrangements for sensing record carriers using a selected wavelength, see G06K7/12)}
- H03F 3/45475: {using IC blocks as the active amplifying circuit}
- G01N 2021/3181: {using LEDs}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- H03F: AMPLIFIERS
- G06K: GRAPHICAL DATA READING (image or video recognition or understanding G06V); PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS

## Abstract

The disclosed scanner for detecting a decay time of light emitted by a luminescent material has a control unit operable to adapt the drive current, or the value of the drive voltage, powering its light source to accordingly adapt the intensity of excitation light delivered to the luminescent material so that its high sensitivity light sensor can reliably measure the luminescence light emitted in response to the excitation light, and thus accurately determine a corresponding decay time value.

## Claims

### Claim 1

A light sensor for detecting luminescence light received from a luminescent material, comprising:
a bias regulator operable to deliver a bias voltage Vb;
a photodiode having a cathode connected to the bias regulator so that the photodiode is reversely biased by the delivered bias voltage Vb, the photodiode being operable to deliver, in a photoconductive mode, a photocurrent intensity Ip in response to received luminescence light in a given photodiode spectral range;
an inverting transimpedance amplifier including an operational amplifier with a feedback resistor Rf and a feedback capacitor Cf mounted in parallel with the feedback resistor Rf between an inverting input terminal and an output voltage terminal of the operational amplifier, the inverting input terminal of the operational amplifier being connected to an anode of the photodiode and operable to convert the delivered photocurrent intensity Ip into an output voltage signal Vout at the output voltage terminal;
further comprising
a PNP bipolar junction transistor of which emitter E and base B are connected in parallel with said feedback resistor Rf and feedback capacitor Cf, with its base B connected to said output voltage terminal and its collector C grounded.

### Claim 2 (depends on 1)

The light sensor according to claim 1, wherein the bias regulator is a low noise, fast transient response bias regulator.

### Claim 3 (depends on 1)

The light sensor according to claim 1, further comprising capacitors C1 and C2 in series connected to the cathode of the photodiode and grounded, a grounded resistor Rg being connected to a non-inverting input terminal of the operational amplifier and a terminal between the capacitors C1 and C2, adapted to eliminate voltage variations caused by the bias regulator.

### Claim 4 (depends on 1)

The light sensor according to claim 1, further comprising a bias current sensor connected between an output voltage terminal of the bias regulator and the cathode of the photodiode operable to measure an intensity of the bias current Ibias delivered to the photodiode.

### Claim 5 (depends on 4)

A scanner for detecting luminescence light from a luminescent material upon illumination with an excitation light within an excitation wavelength range, said luminescent material emitting said luminescence light within an emission wavelength range, comprising:
a power source operable to deliver variable drive current or drive voltage; and
a light source connected to said power source and operable to illuminate said luminescent material with said excitation light within said excitation wavelength range when powered with the drive current or the drive voltage delivered by the power source, during an excitation time interval Δtex, said light source being operable to produce said excitation light with an excitation light intensity varying according to the delivered drive current or drive voltage, further comprising
a light sensor according to claim 4 operable to deliver the output voltage signal Vout to an input terminal of an analog-to-digital signal converter connected to the output voltage terminal upon illumination of said luminescent material with said light source and detection of corresponding emitted luminescence light, the analog-to-digital signal converter being operable to convert the output voltage signal Vout into a digitalized luminescence light intensity signal over a measuring time interval Δtmeas; and
a control unit connected to the bias current sensor to receive a measured value of the intensity of the bias current Ibias and further connected to a control bus, the control unit being operable to control
the power source via a first digital-to-analog signal converter connected between the power source and the control bus by setting a value of the drive current or drive voltage and a value of the excitation time interval Δtex, and
the light sensor via both the analog-to-digital signal converter, further connected to the control bus, and a second digital-to-analog signal converter, connected to an offset resistor Ro connected to the anode of the photodiode and further connected to the control bus to convert an offset current intensity Io into a digitalized offset current intensity, to set a value of the measuring time interval Δtmeas and acquire the luminescence light intensity signal over the value of the measuring time interval Δtmeas to form a digitalized luminescence light intensity signal profile I(t),
wherein
said control unit is further operable to receive said luminescence light intensity signal and control said power source to adapt the value of the drive current, or the value of the drive voltage, delivered to the light source so that a luminescence light intensity value corresponding to a delivered luminescence light intensity signal is below a maximum intensity value Imax corresponding to a saturation threshold value of the photodiode.

### Claim 6 (depends on 5)

The scanner according to claim 5, wherein the control unit, based on the measured value of intensity of the bias current Ibias, is further operable to adapt the value of the drive current, or the value of the drive voltage, delivered to the light source so that a level of the corresponding current intensity in the photodiode is below a photodiode current intensity threshold value and the level of the corresponding current intensity through the PNP bipolar junction transistor is below a transistor current intensity threshold value.

### Claim 7 (depends on 5)

The scanner according to claim 5, wherein the control unit, based on the measured value of intensity of the bias current Ibias, a received value of the digitalized offset current intensity Io, and a received value of the digitalized luminescence light intensity signal, is further operable to set a value of the delivered offset current intensity Io via the second digital-to-analog signal converter.

### Claim 8 (depends on 7)

The scanner according to claim 7, wherein the control unit is operable to switch off the light source and then acquire digitalized luminescence light intensity signal and set a value of the offset current so as to make the acquired digitalized luminescence light intensity signal close to zero, thereby compensating a current intensity due to stray light.

### Claim 9 (depends on 8)

The scanner according to claim 8, wherein the control unit is further operable to power the light source and then form a digitalized luminescence light intensity signal profile I(t), check if a value of a digitalized luminescence light intensity signal acquired after the measuring time interval Δtmeas is close to zero, and, in case said checked value is not close to zero, further set a value of the offset current to make a value of a digitalized luminescence light intensity signal further acquired after the measuring time interval Δtmeas close to zero, and then control the scanner to illuminate the luminescent material during the excitation time interval Δtex, acquire at least one corresponding digitalized luminescence light intensity signal profile I(t) over the measuring time interval Δtmeas and store in a memory each acquired digitalized luminescence light intensity signal profile.

### Claim 10 (depends on 9)

The scanner according to claim 9, wherein the control unit is further operable to determine a value of a decay time of the luminescent material from a stored digitalized luminescence light intensity signal profile.

### Claim 11 (depends on 10)

The scanner according to claim 10, wherein the control unit is further operable to decide that the luminescent material is genuine in case the determined decay time value matches a reference value of decay time.

### Claim 12 (depends on 5)

The scanner according to claim 5, wherein the illumination light source comprises a flat LED, the photodiode is a flat photodiode and said flat LED and flat photodiode are mounted adjacent and wired on a flat support member of a nose piece of the scanner for illuminating the luminescent material and collecting corresponding luminescence light, thereby allowing the nose piece to be disposed close to the luminescent material to improve illumination and luminescence light collection efficiency without necessitating a light guide.

### Claim 13 (depends on 12)

The scanner according to claim 12, wherein the illumination light source comprises a plurality of flat LEDs wired in series on the support member, and a plurality of flat photodiodes wired in parallel on the support member.