Optical Transducer: Working Principle, Types and Applications
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Light is converted into electrical quantity by an optical transducer. Other names for them include photoelectric transducers. There are three types of optical transducers: photoemissive, photoconductive, and photovoltaic. The idea behind how photo emissive devices work is that when light strikes a cathode, electrons are released from the surface of the cathode.
The idea behind how the photoconductive devices work is that when a material is illuminated, its resistance changes. The output voltage produced by the photovoltaic cells is proportional to the radiation intensity. The incident radiation can be visible light, x-rays, gamma rays, ultraviolet, or infrared. Light rays are transformed into an electronic signal by an optical transducer. An optical transducer’s function is to measure a physical quantity of light and, depending on the transducer type, translate that measurement into a form that can be understood by a built-in measuring device.
Types of Optical Sensors (Optical Transducer)
There are various types of optical sensors; the most popular types that we have used in actual applications are listed below.
- Devices that measure resistance by translating a change in incident light into a change in resistance are called photoconductive devices.
- An amount of incident light is converted into an output voltage by the photovoltaic cell (also known as a solar cell).
- A quantity of incident light is converted by the photodiodes into an output current.
Bi-polar transistors with the base-collector junction exposed to light are known as phototransistors. With an internal gain, this produces the same behavior as a photodiode.
The operating principle of an optical sensor is the transmission and reception of light; the object to be detected interrupts or reflects a light beam that is emitted by an emitting diode. The interruption or reflection of the light beam is assessed based on the type of device. This enables the detection of objects regardless of the material they are made of (wood, metal, plastic, or another). Even the detection of transparent objects and those with various colors or contrast variations is possible with the aid of special devices. various kinds of optical sensors are described below.
The transmitter and receiver of the system are two independent parts that are placed across from one another. A light beam is directed at the receiver by the transmitter. The receiver interprets a break in the light beam as a switch signal. Where the interruption occurs is unimportant.
Advantage: Large operating distances are possible, and recognition is not affected by the surface structure, color, or reflectivity of the object. To ensure a high level of operational dependability, the object must be large enough to completely block the light beam.
Both the transmitter and the receiver are located in the same home, and the emitted light beam is reflected back to the receiver by a reflector. A switching operation is started by a break in the light beam. It doesn’t matter where the interruption takes place.
Advantage: Large operating distances with switching points that are precisely reproducible and only require minimal mounting effort are made possible by retro-reflective sensors. Regardless of the surface pattern or color of any object that blocks the light beam, accurate detection is possible.
Diffuse Reflection Sensors
One housing contains both the transmitter and the receiver. The intended target object reflects the transmitted light.
Advantage: The switching condition is the intensity of diffused light at the receiver. The rear part always reflects better than the front part, regardless of the sensitivity setting. This has the effect of causing incorrect switching operations.
Different Light Sources For Optical Sensors (Optical Transducer)
Different kinds of light sources exist. The first light sources used to study optics were the sun and the light emanating from torch flames. As a matter of fact, the reference points in the optical spectrum are still provided by light from specific types of (exited) matter, such as iodine, chlorine, and mercury ions. The monochromatic light source is one of the essential elements in optical communication. Monochromatic, portable, and long-lasting light sources are essential for optical communications. These two light sources are of two different types.
1. LED (Light Emitting Diode)
Light is produced as a result of the recombination of electrons and holes at the junctions of n-doped and p-doped semiconductors. The recombination may be occurring or it may be stimulated as another photon during the excitation, which is accomplished by applying an external voltage. This makes it easier to couple an optical device with LED light.
2. LASER (Light Amplification by Stimulated Emission Radiation)
When the electrons in the atoms of particular glasses, crystals, or gases absorb energy from an electrical current and become excited, a laser is produced. Around the atom’s nucleus, the excited electrons transition from a lower energy orbit to a higher energy orbit. The electrons then emit photons (light particles) when they return to their usual or ground state. So All of these coherent photons have the same wavelength. The common visible light is not coherent and has many different wavelengths.
Applications of Optical Sensors
Computers and motion detectors are just two examples of devices that use these optical sensors. So In order for optical sensors to function properly and maintain their sensitivity to the property being measured, they must be the right type for the application. Computers, xerox machines, and lights that turn on automatically in the dark are just a few of the everyday devices that include optical sensors. Alarm systems, synchros for flash photography, and systems that can detect the presence of objects are a few of the common applications.
Ambient Light Sensors
This sensor is typically found on mobile phones. It will increase battery life and enable simple-to-view displays that are environment-friendly.
In the field of biomedicine, optical sensors are widely used. So Several instances Utilizing a tunable diode laser to analyze breath, A heart-rate monitor that uses light, or an optical heart-rate monitor, can measure your heart rate. An optical sensor analyzes the light that was reflected after an LED pierces the skin and cast its light there. Variations in light level can be translated into heart rate because blood absorbs more light. The name of this procedure is photoplethysmography.
Optical Sensor Based Liquid Level Indicator
An infrared LED coupled with a light transistor and a transparent prism tip at the front make up the two main components of an optical sensor-based liquid level indicator. When the sensor tip is encircled by air, the infrared light that the LED emits reacts by bouncing back inside the tip before returning to the transistor. When the sensor is submerged in liquid, the light spreads out and returns to the transistor less frequently. Point level sensing is possible because the amount of reflected light that reaches the transistor affects output levels.
So Do you know the fundamentals of an optical sensor? We acknowledge that the information provided above, along with the associated images. And various real-time applications, clarifies the fundamentals of the optical sensor concept. Additionally, if you have any questions about this idea. Or how to put any sensor-based projects into practice, please share your thoughts and suggestions in the section below for comments. What are the various light sources used by an optical sensor, I ask you?