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Inrared (IR) LEDs & Sensor Applications

Infrared (IR) is invisible radiant energy, electromagnetic radiation with longer wavelengths than those of visible light, extending from the nominal red edge of the visible spectrum at ~700nm (frequency 430 THz) to 1mm (300 GHz) (although from test data some people can see infrared up to at least 1050nm) in λP wavelengths. Often times what we call Near IR is added to this range at the low end to encompass 665nm and upwards wavelengths. Much of the energy from the Sun arrives on Earth in the form of infrared radiation. Sunlight at zenith provides an irradiance of just over 1 kilowatt per square meter at sea level. Of this energy, 527 watts is infrared radiation, 445 watts is visible light, and 32 watts is ultraviolet radiation. IR radiation is often divided into three smaller regions: 0.750 – 3μm, 3 – 30μm, and 30 – 1000μm – defined as near-infrared (NIR), mid-wave infrared (MWIR), and far-infrared (FIR), respectively. The CIE IR band divisions include IR-A, -B and –C.

IR-A 700nm–1400nm (0-7μm – 1.4μm)
IR-B 1400nm–3000 nm (1.4μm – 3μm)
IR-C 3000nm–1mm (3μm – 1000μm)

 

Now, with III-V compound semiconductor technology and modern epitaxial and die fab processes, man can make IR LEDs and IR Sensors (photo-transistors and –diodes) lamps and devices for use in emitting or sensing IR radiance wavelengths ranging from the Near IR (>660nm λP) to ~1600nm λP (1.6µm). Different types of IR LEDs are specified based on their packaging and special features, such as output optical power, wavelength, and response time. IR Receivers are also called Sensors since they detect the wavelength and spectral radiation of the light from the IR emitter. IR Receivers are specified by optic features, packaging, special circuitry such as an ambient light filter, wide viewing angle, and more. These devices are for use in government, industrial (measurement, counters, motor encoders, etc), scientific, consumer (TVs/STBs, proximity sensors, cell phones, tilt sensors, ATMs/kiosks, cameras, games and toys, etc), security (movement and motion detection, fire alarms, smoke detectors, etc), computers and peripherals (keyboards/mice, etc, printers – paper/media/door detection, etc) and medical (blood/oxygen/temperature measurement) applications as well as in consumer devices. Applications range for emitters from enhancing ones night-vision at night while camping to remote control devices and eye/body tracking systems, and much more..

 

IR Communications:

This area of IR LED applications continues to grow and offer unique benefits.

Wireless IR LED Communications:

These systems work in “direct line of sight” or reflection mode, the most basic example of which can be found at the end of your TV remote control. Many use a 940nm IR LED which is pulsed on and off at 40 Kilohertz to transmit the control codes to the infrared light receiver in the appliance. Transmission is used for relatively short range communications, for example between computer peripherals to transfer files, remote controls. The IR LED signal is received by a photodiode that converts modulated signals into binary data. Now large work space IR Hubs are used in office settings for wireless communications purposes. Many of the IR communications devices employ IR Transceivers in modular form. IR Wireless Communications or networking is used in all types of applications, from the complex multi-transceiver types to simple remote controls for your TV at home. For computer communications used in local networks there are three different (Infrared Data Association: IrDA) standard protocols: a) IrDA-SIR (slow speed) infrared supporting data rates up to 115 Kbps; b) IrDA-MIR (medium speed) infrared supporting data rates up to 1.15 Mbps; c) IrDA-FIR (fast speed) infrared supporting. IrDA-Control is not the same as the standard TV or appliance type remote controls. IrDA-Control has its own set of mandatory protocols: PHY (Physical), MAC (Media Access Control), and LLC (Logical Link Control). For security purposes this type of IR link offers many advantages, primary of these is that there is no risk that the transmission can be compromised, or intercepted yet IrDA infrared port module is the most mature of the wireless communications standards. Today, IR protocols are used in applications like consumer electronics, computers, household appliances, medical devices, automotive technologies & commercial services with high 5 and 10 Gigabit speeds. These devices include cell phones, wristwatches, laptops, PDAs, digital cameras, handheld scanners, laser printers, etc. The IrDA standard has both support and user applications in all major operating systems.

Fiber-Optic IR Communications:

Many of these systems employ coherent IR Laser devices, while others utilize incoherent IR LEDs as the transmitting device and IR Photodiode as the receiving element as LEDs have a higher reliability, are easier to use than lasers and cost far less. They are used with glass and plastic fiber versions with the most common peak wavelengths being 780, 850, and 1310nm. They can be discrete types or Transceivers and used in a variety of multi-channel, repeater and other applications. LEDs are suitable primarily for local-area-network (LAN) applications with bit rates of 10-100 Mbit/s and transmission distances of a few kilometers. LEDs have also been developed that use several quantum wells to emit light at different wavelengths over a broad spectrum, and are currently in use for local-area WDM (Wavelength-Division Multiplexing) networks. The signals they produce and receive are similar to conventional systems and, as well, Wireless IR systems.

Characteristics  LEDs Lasers
 Output Power  Linearly proportional to drive current  Proportional to current above the threshold
 Current  Drive Current: 50 to 100mA Peak  Threshold Current: 5 to 40mA
 Coupled Power  Moderate  High
 Speed  Slower  Faster
 Output Pattern  Higher  Lower
 Bandwidth  Moderate  High
 Wavelengths Available  0.66 to 1.65μm  0.78 to 1.65μm
 Spectral Width Wider (40-190nm FWHM)  Narrower (0.00001nm to 10nm FWHM)
 Fiber Type  Multimode Only  SM, MM
Ease of Use Easier Harder
Life Time Longer Long
Cost Low ($5-$300) High ($100-$10,000)

 

IR Augmented Low-Light Cameras & Video:

All CCDs can detect IR. In turn IR LEDs can be used to further enhance these images from emitted and then reflected IR produced by LEDs helping enable video recording and image capturing. Many of these systems employ IR LED emitters and an infrared detector or CCD. The emitter sends out infrared, and then the detector records the picture. Use is similar to using the flash on a camera for still, timed or streaming image recording. When the system is in use the flash lights up the object in focus, and makes the image brighter in the recording. Only in this case, the flash is in infrared light instead of visible light. This technology is useful in cases where you want to see what is going on without shining visible light on the scene, such as in security systems.

 

Infrared Therapy:

IR wavelengths have been found to be beneficial to humans in many ways as they produce healing effects on the biological processes that take place in our bodies. IR Therapy is used in medical, veterinarian, sports medicine and a variety of other clinical and home-based applications. Long IR wavelengths penetrate our skin and can reach into our bodies more effectively, without damage, than other types of radiation. Cells in the skin and supporting tissue absorb wavelengths between 590nm and 950nm nanometers. Infrared light therapy is a form of phototherapy where it is directly applied to your body to cure illness. No medicines are involved in this treatment. When infrared light enters the skin surface, it facilitates release of nitric oxide. This particular component relaxes blood vessels and prevents formation of blood clots. Thus it improves blood circulation to the affected area. As more and more blood reach the damaged tissue, the supply of oxygen and valuable nutrients to it also increases. In this way, IR LEDs ensure faster healing of damaged tissues. Infrared light can be used for the treatment of minor problems like acne to more serious ailments like chronic arthritic pain, high blood pressure, fibromyalgia, and neuropathy or can be used to help in hair loss and wrinkle sublimation. IR LED Therapy has been found to effective in many applications. Many home-based therapies include the following:

Cure for Acne:

IR LEDs are used to treat acne, ATP (Adenosine triphosphate, a molecule that transfers chemical energy within cells for metabolic processes) in the skin cells gets activated and kills the bacteria present in the skin pores. When there are no bacteria, the skin inflammation goes down and acne is cured.

Chronic Pain Relief:

Chronic pain resulting from arthritis, neck pain or stiff muscles can be treated with the help of this therapy. When it is administered on a tender spot, the taut muscles loosen up and the accompanying pain is relieved.

Treating Sports Injury:

Many of the aches, soreness and swellings that athletes suffer from are either due to sprains or due to nerve cell damage; IR LED Therapy can help here too. The use of IR LEDs soothes nerves and stimulates the pituitary gland which releases endorphins in the body. Endorphins are commonly referred to as ‘natural pain relievers’. With the release of endorphins, pain is alleviated naturally. Skin, tissue and muscle damage are also healed through this treatment.

Wound Healing:

Diabetic patients have low levels of nitric oxide in the blood because their insulin-dependent blood vessels become less responsive to nitric oxide. Hence, in case of an external injury, their wounds take longer time to heal. IR LEDs facilitate the release of nitric oxide, which in turn, improves blood flow. Due to increase in blood circulation, wounds heal more quickly. IR LED therapy can also be used for cold sores, mouth sores, nicks and scratches to heal them faster and effectively.

Lowering High Blood Pressure:

High blood pressure can lead to various life-threatening diseases like heart attack and stroke. When a person is suffering from high blood pressure, it means that the heart has to work hard to maintain proper supply of blood throughout the body. Application of infrared rays increases the blood circulation in the body and provides a sense of stress-free well-being. IR bio-modulation process, in which metabolic processes within cells and tissue are increased prompting natural repair mechanisms within cells and tissue to heal; as well as use for a variety of lab and hospital research and diagnostic equipment, are found within hospital and clinic settings:

 

IR Medical/Lab Detection, Surgery, Diagnostics, Analyses & Discovery:

Here the application of IR LEDs & Sensors is quite instrumental in patient care situations as well as medical and lab equipment scenarios.

Neuroplasticity:

The human brain is designed to reorganize or restore its neural network pathways when trauma, injury or disease is present in the body. This ability enables the brain to respond to these conditions, and make steps to restore bodily systems. Infrared light therapy techniques can be used to stimulate neural processes to respond to stressed or traumatized regions within the body. However, stimulation applied to neural processes can potentially create faulty neural networks that give rise to abnormal effects that may, or may not result in permanent damage.

Laparoscopic Surgery:

One of the best things about laparoscopic surgery is that it is minimally invasive surgery with small shutterstock_260814368-docincisions. But one major challenge that comes with it is it can be hard to identify blood vessels. IR LEDs and Sensors are used for spectroscopy integrated into the tips of surgical cutting tools to help surgeons avoid cutting blood vessels accidentally. The devices detect the presence and diameter of blood vessels in laparoscopic surgery alerting the surgeon to their presence and locations. Thid approach reduces healthcare costs since it could reduce the transfusions that patient would require if a blood vessel were cut, as well as the follow-up procedures to mend the damaged blood vessel. A study by Johns Hopkins School of Medicine, relying on data from The Data Bank National Practitioner tracking medical malpractice settlements and out-of-court settlements from 1990 to 2010, estimated that about 4,000 surgical errors took place in that time frame, but acknowledged that the estimate was likely low since many cases are not reported.

Photodynamic Therapy:

One of the biggest challenges with treating cancer is killing cancer cells without harming healthy cells. Photodynamic therapy (PDT) is a treatment that uses a drug that is initiated via light, called a photosensitizer or photosensitizing agent, and a particular type of long wavelength radiance such as Near IR and IR and or combinations (to achieve skin and tissue penetration) to activate this drug. When photosensitizers are exposed to such radiance, they produce a form of oxygen that kills nearby cells and cells they are bonded to. Each photosensitizer is activated by a narrowband wavelength ideal for Near IR and IR LEDs. This wavelength determines how far the light can travel into the body or within the body as the light is delivered via a delivery implement in a direct manner or via fiber-optics in an indirect manner inside organs such as bladders, lungs, intestines, esophagus, etc. Once the drug is injected into the bloodstream tailored to bind with cancer cells, the cancer cells absorb the drug. IR LED radiation is then projected onto the relevant area; the drug absorbs it and is ‘photo-initiated’ to produce a chemical reaction that kills the cancer cells.

IR Photo-Biomodulation:

Near-infrared technology is being used to reduce hospital-acquired infections, an enormous issue providers have been addressing. One group of Drexel University researchers has developed a way to identify bed sores before they actually appear on the skin. The diffuse near-infrared light is directed to the skin using lenses, so there is no contact with the patient’s skin. The device measures hemoglobin concentration and oxygenation beneath the surface of the skin to help physicians assess tissue damage. IR LEDs are also used for oral ulcers that result from Chemotherapy, tissue repair, reduce inflammation etc.

IR Brain Trauma Diagnostics:

This technology is utilized for a variety of brain trauma diagnostic and monitoring applications. It has also been adopted by Hospitals for Intensive Care Monitoring of patients undergoing observation for small or delayed hematomas and also for monitoring post-neurosurgery patients. Neurosurgery patients can be monitored as often as necessary, at bedside, to provide early detection of changes in intracranial hematomas between CT scans thus decreasing the frequency of damaging, disruptive, and inconvenient CT monitoring. Additionally, since approximately 20% of trauma-related hematomas do not appear for more than 12 hours following an accident; this scanning technique can be used effectively as a bedside monitoring tool for hospital patients undergoing observation. For Military Applications IR Scanners can be used as a tool for mass-casualty events or for expedited evacuation decision-making.IR scanners can be portable or system based. They excel in detecting Traumatic Brain Injury (TBI) on the battlefield and in other settings where timely triage is critical. Recognizing its battlefield potential, the United States Navy’s Office of Naval Research and the United States Marine Corps have invested significantly in IR scanners and have successfully field tested them. Early hematoma detection is lifesaving technology that also supports prioritized evacuation of injured military personnel. The USMC has now fully deployed this technology at all its battalion aid stations. Screening in Remote Areas provides rapid initial evaluation enabling critical decisions on whether to leave a patient in a local hospital or evacuate to a trauma center. Head trauma patients are now diagnosed at the site of injury by first responders, in remote villages, small towns, islands, mines, sport clubs, skiing sites, hospitals and other locations that lack convenient access to CT scanners or neurosurgeons. IR scanners have also found a home in Sports Medicine where they can quickly aid in the decision to evacuate injured athletes to a trauma center or observe locally. The growing recognition of sports-related brain trauma creates an ideal application area. So to for Pediatric applications for triage of small children (where Glasgow Coma Scale is not reliable). Ambulance Services use IR scanners for patients in stroke assessment or intracranial bleeding from a head injury in two minutes. The mobile type IR scanners, with full U.S. Food and Drug Administration clearance can be used to acquire data wirelessly via a mobile phone. All made possible from the use of IR LEDs & Sensors.

Sepsis Detection:

An IR breath biomarker is part of the key to early sepsis detection. When the body has an infection, it tends to use carbon 13 in the metabolism associated with the infection. With the test, patients exhale into a bag. The sample goes into a spectrometer equipped with infrared devicess that measures the ratio between carbon 12 and carbon 13 in the carbon dioxide extracted from the breath. Sepsis is caused by the presence of bacteria or other germs in the blood, which kicks in the body’s immune response. Inflammation occurs that can cause complications with blood flow. Early detection and treatment of sepsis is critical to survival. In 2008, about $14.6 billion was spent on hospitalizations for septicemia, according to the Centers for Disease Control and Prevention.

IR LED Spectroscopy:

This type of spectroscopy deals with the study of absorption of infrared radiation which results in vibrational transitions. There are many types and configurations of IR LED Spectroscopy equipment used in laboratories, research, clinical and other user communities. The types range from large scale equipment to small hand-held mobile devices that can use your smartphone for communications and apps. This type of spectroscopy can be used to study study organic compounds, ranging from pharmaceuticals to living tissue to gases and also to identify molecules by analysing their bonds. The concept behind this is: Atoms in molecules are in their continuous state of vibration. When these molecules absorb infrared radiation, they become excited and the vibration increases. The wavelength of infrared radiation absorbed depends on the chemical bonds between atoms in molecules. For example absorption for C-Cl bond will be different from C-C or C-O or C=O or C-H bond. All these combinations have Carbon (C) in them, but since they form a bond with a different element in each case, the bond is different. By analyzing the Infrared spectrum of these substances, their composition can be determined. One of the more versatile IR LED spectrometers is a Fourier Transform Infrared Spectroscopy (FTIR). Small handheld units can use this technique to obtain an infrared spectrum of absorption, emission, photoconductivity or Raman scattering of a solid, liquid or gas. An FTIR spectrometer simultaneously collects high spectral resolution data over a wide spectral range. This confers a significant advantage over a dispersive spectrometer which measures intensity over a narrow range of wavelengths at a time. Radiation in terms of optical based spectrometers can be UV-Visible radiation or IR radiation. FTIRs can be used in all applications where old style dispersive spectrometers were used in the past and in addition, the multiplex and throughput advantages have opened up new areas of application. These include:

GC-IR (gas chromatography-infrared spectrometry):

A gas chromatograph can be used to separate the components of a mixture. The fractions containing single components are directed into an FTIR spectrometer, to provide the infrared spectrum of the sample. This technique is complementary to GC-MS (gas chromatography-mass spectrometry). The GC-IR method is particularly useful for identifying isomers, which by their nature have identical masses. The key to the successful use of GC-IR is that the interferrogram can be captured in a very short time, typically less than 1 second. FTIR has also been applied to the analysis of liquid chromatography fractions.

TG-IR (thermogravimetry-infrared spectrometry):

IR spectra of the gases evolved during thermal decomposition are obtained as a function of temperature.

Micro-samples:

Tiny samples, such as in forensic analysis, can be examined with the aid of an infrared microscope in the sample chamber. An image of the surface can be obtained by scanning.

Rare Object Analysis:

Another example is the use of FTIR to characterize artistic materials in old-master paintings, ceramics, pottery, sculptures, etc.

Emission Spectra:

Instead of recording the spectrum of light transmitted through the sample, FTIR spectrometer can be used to acquire spectrum of light emitted by the sample. Such emission can be induced by various processes, and the most common ones are luminescence and Raman scattering. Little modification is required to an absorption FTIR spectrometer to record emission spectra and therefore many commercial FTIR spectrometers combine both absorption and emission/Raman modes.

Photocurrent Spectra:

This mode uses a standard, absorption FTIR spectrometer. The studied sample is placed instead of the FTIR detector, and its photocurrent, induced by the spectrometer’s broadband source, is used to record the interferrogram, which is then converted into the photoconductivity spectrum of the sample

Gas Chromatography:

This fiedld includes CO2 sensors which are increasing in use and will reach some $150 Billion by 2020. Wherever air is and the need to analize it, this technique is used. Settings for use are unmerious, ranging from alcohol breath analyzer/ignition locking devices to chicken and greenhouse farms to industrial process controls.

IR LED Reflectography:

Infrared reflectograms are used by many disciplines in understanding their composition and structure. Fields of use include scientific, medical, laboratory, industrial, archeological, geological and many more. For example this technique of analysis is used by art conservators to see the various layers in a painting leading them to an understanding of the basic steps involved in a painting, like its outline and other layers beneath the top paint. It will also reveal if the painting is original or a duplicate copy. By looking deep into the different layers of painting and recording the infrared radiation reflected by the painting generates an image called the infrared reflectogram. This reflectogram is converted to a digital format (this is black and white) on a computer that reveals a multitude of details about the painting that are invisible to the human eyes.

 

 

The uses for IR LEDs abound. They are the key element in many systems architectures. There small size, high efficiency, narrow wavebands, rugged and reliable service can benefit many old, new and developing applications. I am a chemical engineer and want to determine the molecular structure and composition of certain substances; I am a medical technician and want to locate diseased tissues (these areas emit abnormal heat compared to the other areas) and injury by analyzing the body tissue and body fluid; I am a soldier using an infrared imaging devices to locate enemy troops in the dark, detect hidden mines, arm caches, to guide anti-aircraft missiles, etc.; I am a paramedic trying to locate missing people and people trapped under collapsed buildings; I am an archeologist studying ancient civilizations; or I am using IR LEDs to help my arthritis pain. All of these people, and many more, have IR LEDs in common.