635nm Bandpass Filter (AlGaInp)

Context: This patent describes a barcode reader or imaging engine that uses specific LED illumination to read codes. The system requires an optical filter to ensure that only the light from the illumination source (centered around 635nm) reaches the sensor, while sunlight or room light is blocked.

Usage of Filter: The bandpass filter is used as an ambient light rejection filter in a barcode scanning system.

Function: The filter is designed with a Center Wavelength (CWL) of 635nm and a Full Width at Half Maximum (FWHM) of approximately 65nm. Its function is to pass the specific amber/red LED light used to illuminate the target while absorbing or reflecting all other wavelengths.

Result: The scanner achieves a high signal-to-noise ratio, allowing it to accurately decode barcodes even in bright ambient light conditions or on glossy surfaces where interference would otherwise occur.

Context: This device helps nurses and doctors locate veins beneath a patient's skin by scanning a laser over the area. Deoxygenated hemoglobin in the blood absorbs red light (specifically around 635nm) more than the surrounding tissue.

Usage of Filter: The bandpass filter is used as a laser line cleanup and contrast enhancement element in a medical visualization device.

Function: A 635nm bandpass filter is often placed in the optical path of the laser diode source. Its function is to "clean up" the laser output, removing any spontaneous emission or spectral noise that falls outside the 635nm peak. It ensures the light projected onto the skin is monochromatic and precise.

Result: The device projects a high-contrast map directly onto the patient's skin where veins appear as dark lines against a red background, significantly improving the success rate of venipuncture (finding a vein for IVs or blood draws).

Context: This patent describes a handheld imaging device used to detect bacteria in wounds by exciting them with specific wavelengths of light. Bacteria produce endogenous fluorophores (like porphyrins) that fluoresce when excited by specific light sources.

Usage of Filter: The bandpass filter is used as an excitation filter for fluorescence-based wound monitoring.

Function: The system uses a 635nm light source (laser or LED) to excite specific bacterial markers. A 635nm bandpass filter is used to narrow the bandwidth of this excitation light, ensuring that no stray light overlaps with the detection range (which is usually at a longer wavelength, e.g., >660nm).

Result: The system achieves clear separation between the excitation light and the faint fluorescence signal emitted by the bacteria, allowing clinicians to "see" infection in a wound bed that would otherwise look invisible to the naked eye.