What Is a Photosensitive Sensor?
Photoelectric sensors use light to detect objects. The light is emitted from the Emitter and then reflected back by the target.
There are a few different types of photosensors to choose from, including the traditional resistive sensor. If you need a higher level of sensitivity, consider using a phototransistor sensor instead.
Light Sensitivity
A photosensitive sensor is a type of device that can sense light. These devices can be used for a variety of applications. They are also used in the medical industry to detect blood and other types of fluids.
Just like a thermometer or speedometer, a photosensitive sensor senses the amount of light coming in. They are usually made of a thin, transparent, material that can capture the light.
The sensitivity of a sensor can be adjusted or programmed to change the threshold of the light required for energize the sensing element. This is important because the type of object being detected can significantly alter the threshold of light that needs to be able to energize the sensor.
Having a high sensitivity is not necessarily a good thing, but it can be helpful in certain situations. If you are experiencing sudden severe light sensitivity or it does not go away, see your doctor right away to determine whether it is caused by a serious condition or simply a symptom of something else.
If you have a mild case of light sensitivity, try to reduce the amount of bright light that enters your eyes by using dark glasses or eye drops. You should also consider seeing your optometrist to have any concerns about your sensitivity investigated and treated accordingly.
Most often, light sensitivity is caused by an underlying medical condition. This may include a detached retina, contact lens irritation, sunburn or refractive surgery. It is also associated with a number of rare diseases and some medications, such as belladonna, furosemide, quinine and tetracycline.
People with light-colored eyes are more likely to experience this type of sensitivity than those with darker eye color. This is due to the fact that the melatonin in light-colored eyes can help protect the eyes from some ultraviolet (UV) radiation.
A photosensitive sensor can be made of several different materials. They are typically made from plastic or glass.
Photosensitive sensors can be either conductive or semiconductor in nature. They are mainly classified into two categories: those that generate electricity when illuminated and those that change their electrical properties when subjected to light. The former are called photovoltaic or photo-emissive sensors, while the latter are known as photoconductive devices.
Light Reflection
Reflection, or the ability to sense light, is an important aspect of a photosensitive sensor’s capability to detect objects. When a beam of light is reflected back onto the receiver, it changes the output signal from the sensor, letting the system know that an object has passed in front of the detector.
In some sensors, the light emitter and receiver are housed in the same housing while others have both components built into separate units. In these types of sensors, the light beam is emitted from the emitter and then reflected by a retroreflector to the receiver.
When an object interrupts the light beam between the two components, the reflected beam becomes diffused and the sensor detects this change in output. This type of sensor is best suited for detecting multiple, translucent objects, fill level inside containers, and object detection.
Most modern pulse modulated photosensitive sensor photoelectric sensors have a low hysteresis circuit that allows them to respond to small light changes in the light path between the transmitter and receiver. This capability greatly increases the sensing accuracy and reduces false triggers.
Another way that a photosensitive sensor can sense light is through the use of an LED source. The LED emits a pulsing light beam, typically at a frequency between 5 and 30 kHz. This eliminates ambient room lighting and other light interference from affecting the performance of the device.
Regardless of the type of photoelectric sensor used, the amount of light it receives from the source is very important. This determines how well the sensor can detect changes in the surface it is on.
There are many different kinds of photosensitive sensors available, including diffuse-reflective, through-beam, and retro-reflective. Each comes with a range of features, depending on the application.
Diffuse reflection sensors are a great choice for direct detection of objects, because they combine the light projector and receiver in one unit. They can also distinguish transparent and opaque reflective objects, and have a long operating life.
For more advanced applications, there are through-beam sensors that can suppress the background to improve their ability to accurately detect the object being measured. These sensors also have a lower power consumption and longer battery life.
Light Detection
Light detection, or the ability to sense light in a photosensitive sensor, is a vital part of any sensor. It is the process by which a sensor determines whether or not something is present in the environment and how much it is there. This information can be used to help create a more accurate picture of an area or object.
In a photosensitive sensor, light can be detected by converting the radiant energy of a photon to an electrical signal. This type of sensor is often called a photoelectric sensor, and there are many different types to choose from.
There are three main modes of detection for a photoelectric sensor: diffusing mode, convergent beam mode, and opposed mode (thru-beam). Each has its own strengths and weaknesses.
Diffusing mode is the most common sensing mode and is the simplest. In this method, a single housing houses both the transmitter and receiver. The light from the transmitter is aimed at the receiver and when the target breaks the beam, it causes the output on the receiver to change state.
This is an efficient way to detect photosensitive sensor small targets that may not have good reflectivity. It also allows for a wide range of operating stability and sensing distances.
Convergent beam mode is another option for diffused mode sensors, and it is more efficient than diffused mode sensing because all the emitted energy is focused at a single point. This can make it easier to detect narrow or low-reflectivity targets, such as glass.
The third primary mode of detection for a photoelectric sensor is opposed mode, which is a more advanced method of diffused mode sensing. It uses two separate housings, one for the transmitter and one for the receiver. When the target crosses the beam, the output on the receiver changes state.
Other types of sensors can also measure illuminance, which is the amount of light reflected by a surface. These include photodiodes, photoresistors, and phototransistors. These sensors measure the drain and collector currents of the device and then change the resistance of the device proportionally to the incoming light intensity.
Background Suppression
Background suppression, or the ability to suppress background noise, is a useful capability in photosensitive sensors. It can help to mitigate some of the sensitivity challenges that a photosensitive sensor can face when detecting objects against backgrounds such as mirrors, glass or shiny surfaces.
Compared with fixed-focus sensors, background suppression photoelectric sensor models feature electronic range adjustment via an external potentiometer that allows you to reposition the sensor within its preset sensing distance (though they operate best at their preset focal spot). Additionally, they can be used in a wide range of industrial applications because they offer tamper-proof detection and are less likely to be influenced by mounting or positional issues.
To suppress background reflections, these types of sensors use a ‘triangulation principle’ similar to a diffuse mode reflective sensor. Instead of emitting light from a lens, a target is illuminated with an LED and the target then reflects the light back to two receiver elements embedded in the sensor’s housing at different angles.
As the target moves closer to the sensor, the angle of the reflected light increases. This causes the receiver element to receive more light than it does at a greater distance, which triggers an output. As the target moves away from the sensor, the angle of the reflected lights decreases and the receiver element receives less light.
A common sensitivity challenge in photoelectric sensor systems is the presence of low-frequency noise. This type of background noise can be a problem because it prevents the detector from achieving its maximum sensitivity. It also can result in false alarms, which can lead to product rejection or production delays.
For this reason, background suppression sensors are becoming increasingly popular in automated manufacturing. For instance, a new 44B sensor from Rockwell Automation uses a dual-receiver optical system to actively ‘see’ both the target and background areas while suppressing any background reflections.
The main disadvantage of these types of sensor is that they must be positioned very precisely in order to function properly. This can be difficult, especially when aiming them at very shiny objects or mirrors, because the amount of light that is reflected back from these items can overwhelm the sensor. To avoid this, it’s important to angle the sensor slightly so that it is not perpendicular to the object or the background.
