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What is Optical Sensors
Overview of Optical Sensors
Optical sensors are all about detecting and measuring light intensity. They convert light rays into electrical signals and connect to electrical triggers that are sensitive to changes in light. You’ll find optical sensors in all sorts of devices, like computers and motion detectors. In this article, we’ll explore the types of optical sensors that have been developed and their various applications.
Types of Optical Sensors
The main idea behind optical sensors is the transmission and reception of light. They evaluate light that’s reflected or interrupted by a target object, based on what the object is made of—like wood, metal, plastic, or even transparent and colored materials.
Optical sensors use different types of light sources, which need to be monochromatic, long-lasting, and compact. The two most common light sources are Light Emitting Diodes (LEDs) and LASER (Light Amplification by Stimulated Emission of Radiation).
You can place optical sensors either externally or internally in a device. External sensors, called extrinsic sensors, collect and transmit the needed amount of light. On the other hand, internal sensors, or intrinsic sensors, often measure bends and changes in light direction. These are usually embedded in optical fibers or other devices.
Depending on the application, different types of optical sensors come into play. For example, in photoconductive devices, they measure resistance by converting changes in light into changes in resistance.
In solar cells, these sensors turn light into output voltage. A photodiode takes incident light and converts it to output current. A phototransistor, which is a type of bipolar transistor, works like a photodiode but with some internal gain. Let’s look at some common types of optical sensors.
Through-beam Sensors
In through-beam sensors, you have a transmitter and a receiver facing each other. When the light gets interrupted, the receiver interprets this as a switch signal.
These sensors work over considerable distances and can detect various object surfaces, structures, and colors.
Retro-reflective Sensors
Retro-reflective sensors have the transmitter and receiver in the same system. Just like through-beam sensors, they initiate switching operations and cover large distances. They accurately detect any object that interrupts the light beam.
Diffuse Reflection Sensors
With diffuse reflection sensors, the transmitter and receiver are also in one system. This type detects the light that’s reflected by objects nearby.
Optical Sensors in Action
Optical sensors are really cool because they analyze reflected light. For example, as blood absorbs more light, changes in light intensity can show us the heart rate. This neat process is called photoplethysmography.
Contactless Sanitizer Dispensers
The COVID-19 pandemic created a huge demand for contactless solutions. One common use for optical sensors is in contactless sanitizer dispensers found in healthcare facilities. These help keep things hygienic without the need for touch.
Breath Analyzers
Breath analysis is done using a tunable diode laser, making it super effective for various applications.
Detection of Biomarkers in Human Serum
Serum is key for proteomic analysis because it carries important markers that tell us about overall health. However, detecting certain diagnostic biomarkers, especially low-molecular-weight (LMW) peptides and circulatory proteins, can be tricky due to their changing concentrations in serum.
Recently, a new strategy was developed to improve the detection of LMW amino acids. This method mixes mid-infrared (MIR) and near-infrared (NIR) spectroscopic data to spot LMW compounds in complex serum samples.
Agricultural Applications
In agriculture, optical sensors have made it possible to detect pesticides in food products right on-site. There have been some exciting advancements in optical sensing tech, like target-responsive hydrogels, fluorescence sensors, and even wearable glove-based sensors. These innovations help us quickly detect pesticide residues in food.
Environmental Applications
Heavy metal pollution, like cadmium in soil, can really affect food security and human health. While microelectronic sensors using fluorescence spectrometry (XRF) are often used to find heavy metals, their accuracy and sensitivity can be questionable. To address this, a high-detection-efficiency photodiode (HDEPD) has been created, which significantly boosts the accuracy of these measurements.
Industrial and Commercial Applications
Optical sensors also play a role in industries, like detecting liquid levels in engineering facilities. For instance, they can measure petroleum levels in refineries and tanks. Plus, in smartphones, ambient light sensors help save battery life by adjusting screen brightness based on the surrounding light.
The Future of the Optical Industry
Looking ahead, the demand for optical sensors is expected to grow, with an estimated compound annual growth rate (CAGR) of around 9.5% from 2022 to 2032. With advancements like automatic lamps, position sensors, and photoelectric sensors, the optical industry, especially in electronics, is gaining a lot of attention.
As we find ways to develop various optical sensors for critical biomedical analysis at low costs, the future looks bright for this industry. The booming biometric market, along with the use of fiber optic sensors in aerospace and smart homes, is driving up sales of optical sensors.
