| 摘要 |
Apparatus for use in measuring a luminescent property such as phosphorescence of a sample comprises a light emitting diode (LED) 18 for emitting radiation to excite the sample 12. Driver circuitry 20 generates a control signal for modulating the intensity of the emitted radiation from the LED 18. The control signal has a first component at a first frequency with a period that is less than, or of the same order as, an expected characteristic time constant, such as a decay constant, of the luminescent property. The control signal has a second component at a second frequency with a period that is greater than the expected characteristic time constant of the luminescent property. A photodiode 22 receives the radiation luminesced from the sample 12 as a result of the excitation and detector circuitry 24 generates a detection signal representing an intensity of the received radiation, and demodulates the detection signal to produce a signal representing the luminescent property of the sample. Measurement of phosphorescence can be made independently of background, reflection and fluorescence effects. |
