Nanoco’s HEATWAVETM quantum dots are specially designed for use in the sensor industry to extend the range of current CMOS Image Sensors out into the Near Infrared (NIR) range of wavelengths.
Like all quantum dots, HEATWAVETM material can be tuned for specific absorption bands by adjusting the size of the particle, ranging from 900nm out to 1800nm, and simply applying a layer onto the surface of a CMOS Image Sensor extends its sensitivity range out to this region.
Extending this range allows the sensors to maintain the small pixel size of CMOS Image Sensors compared to other expensive technology in the NIR region, allowing for higher resolution camera devices at a much cheaper cost. In addition, HEATWAVETM material maintains the device sensitivity in the visible part of the spectrum, allowing devices which can readily switch between visible and non-visible light detection.
Applications for NIR CMOS Image Sensors are typically defined by their peak sensitivity wavelength. Some of these applications are outlined below with the advantages HEATWAVETM quantum dots could offer to device manufacturers.
Biometric facial recognition in CMOS Image Sensor camera modules often utilises what is known as a structured light approach to sensing where a fixed pattern of light at a target and measuring the level of distortion of the pattern caused by the targets 3D features using a corresponding sensor module. As this is a process done with an observer a safe non-visible wavelength is required so as to not be intrusive for the user, with 940nm often chosen due to the ready availability of emission sources.
Common silicon CIS cameras are used for the subsequent light detection but they do come at a disadvantage in that they have poor sensitivity at the required 940nm wavelength unless a costly wavelength specific modification process is used. HEATWAVETM quantum dot-enabled CMOS Image sensors however are able to maintain a high efficiency in this NIR region, with an additional advantage that the camera can still maintain efficient sensitivity at visible wavelengths. The increase in efficiency reduces the power requirement for the facial recognition sensor whilst also improving the speed facial recognition can take place, in addition cameras sensitive from visible wavelengths through to NIR allow the same module to provide multiple functions for a given device saving valuable space if utilised in often crowded consumer electronic devices.
Optical diagnostics work by pulsing light through the skin of a patient and measuring the amount of absorption and scattering that has occurred. Once tuned to a specific molecule at a specific wavelength the level of absorption and scattering can be used to determine the levels of the target molecule in a patient’s blood, proving a non-invasive diagnostic path. Current molecules of interest are haemoglobin for blood O2 levels at 575nm, bilirubin to indicate liver function at 455nm and glucose to indicate diabetic insulin levels at 1650nm.
HEATWAVE TM quantum dot-enabled CMOS sensor devices will allow this wide range of wavelengths to be detected by the same device, and with the advantage of small pixel size will take up minimal room on a wearable device. In addition the high efficiency of the material will reduce power consumption of the detector set up, extending usage time between charges for a user.
Sensors for range finding and LiDAR applications are tuned to wavelengths where atmospheric absorption of light is quite high, ensuring the minimal amount of light from the sun is present to provide signal interference. The technology works by measuring the amount of time it takes for an emitted beam of light to bounce off a target and be picked up by a detector and using that time to calculate the target distance, called Time of Flight (ToF) detection. When combined in an array or emitters and detectors it can be used to map out a 3D image of objects within the sensors field of view.
HEATWAVE TM quantum dots have demonstrated fast response times and high efficiencies, both key features for the development and range extension of ToF sensing technology for both consumer electronics and industry. Range finding LiDAR technology is currently finding lots of interest in different fields such as machine vision, autonomous vehicles, geographical mapping and military targeting applications.
Night vision applications typically use light in the NIR to enable vision in low light situations, with the camera using light from solar bodies such as the moon or from an external illumination source emitting at a non-visible wavelength. Current technology suited for vision in the region has relatively low pixel resolution, however, resulting in low final image resolution or over-sized sensor arrays. HEATWAVE TM quantum dots enable high resolution CMOS sensors to efficiently operate in this region allowing for highly detailed images to be obtained by the viewer for target identification