Light sensor and decay-time scanner
AssigneeSicpa Holding SA
InventorsFrédéric Pierson, Joël Bonny, Samuel Brügger, Daniel Zahnd
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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.
Claims13
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.
Dependencies are inferred from the claim text.