Infrared Laser – Lighting and 3D Sensing Application
Publish Date：2020-05-14
Light and Lighting
Light (also known as visible light) is usually defined as an electromagnetic wave that can be observed by the human eye. The main source of light in nature is the sun that we can see every day. And because of the sun, the earth also has the concept of day and night.
Before the 19th century, the range of people’s activities at night was greatly limited due to the lack of effective and long-term stable lighting technology. This situation continued until the first electric lamp was invented, and humans got rid of oil lamps or candlelight dependence. The use of incandescent light bulbs represents that human civilization has evolved from steam to electric power, the factory began to operate day and night, and various commodities can be produced in large quantities and quickly. The artificial light source technology not only lights up the world, but also becomes the most indicative symbol of the Second Industrial Revolution.
Diode laser lighting technology
From incandescent bulbs, halogen lamps, mercury lamps, fluorescent lamps, to LED lamps, people have never stopped studying lighting technology. Scientists and engineers are constantly pursuing higher luminous efficacy and longer service life. The advancement of lighting technology has also expanded its application range from factory or home lighting to scientific research, stage, projection, monitoring, military and other fields. In recent years, because of the increasing requirements for the performance of lighting tools, laser diode (LD) lighting technology is also emerging.
Compared with other lighting methods, the diode laser has the following characteristics:
1. High Output Power:
The theory of diode laser luminescence is to use the electron-hole recombination that occurs on the PN junction of the diode to emit photons. And form a standing wave in the resonance cavity formed by the laser gain medium and the two reflection surface, eventually emit high-intensity laser light.
Lasers are currently known to produce the most powerful and controllable light source.
2. Wall-plug efficiency:
Wall-plug efficiency (WPE) refers to the efficiency of converting input current into optical power. For diode lasers and LEDs, the conversion of electrical energy into light energy is accompanied by heat generation. The low WPE represents not only high power consumption; the thermal energy generated by the diode will further cause the distortion of electronic structure, this leads to a shift in the emission wavelength and even a vicious cycle of WPE degradation.
In terms of high-power lighting requirements, diode laser lighting technology has higher efficiency than LEDs. It provides energy-saving, stable, high-brightness light sources.
3. Coherence and Monochromaticity of Laser：
Coherence and monochromaticity are the most notable characteristics of Lasers. As mentioned earlier, the LD will emit laser after forming a standing wave in the resonant cavity, so it will have a consistent phase and wavelength after being emitted. Because of this feature, laser light is irreplaceable in areas that need to use special wavelength or phase characteristic, such as 3D sensing and optical communications.
Infrared Laser Lighting Application
Infrared (IR) refers to electromagnetic waves with a wavelength between 760nm and 1mm, and the near-infrared (NIR, wavelength from 760nm to 1400nm) is commonly used in the lighting field. Although its wavelength is close to that of red light, it cannot be observed by the human eye. Using invisible light for lighting sounds paradoxical, but this is why it can be used in special lighting field. Below we will introduce some of the most typical applications.
1. Night Vision Application
The first thing to introduce is the night vision technology using IR light illumination. This technology was first used in the World War II. At that time, the battlefield was observed with a set of IR light sources and a night vision device to receive images reflected by objects. Because IR light is invisible to the naked eye, the party equipped with an IR night vision device will have a huge advantage.
After the war, this technology was extended to the field of livelihood. For example, surveillance cameras that can be seen in front of the home or on the street, the monitor can directly observe the surrounding environment under sunlight during the day. And at night, it will turn on the IR light source as lighting and switch to night vision mode. Therefore, it can achieve all-day security protection. Similar applications include night vision cameras equipped with IR projection systems.
So what role do IR laser diodes play in the field of night vision applications? Although other light-emitting methods such as LEDs can produce IR light, however, the night vision application can be upgraded to a completely different level after being used with a laser.
Fig. 1 Schematic diagram of IR night vision observation with CCD
When using a non-laser light source for illumination, most of the range is only a few meters to tens of meters due to the factor of light source energy and divergence. This may be sufficient for household needs. However, for the use of outdoor wide-area areas such as large-scale factory monitoring, field or forest observation, and highway monitoring that require long-distance observation, a higher power light source is inevitably required. And it is even more so in military applications because night vision equipment has been widely used in various countries. The low power IR sources that can only be used at short distances will expose your location and cause danger. For traditional light sources, the method to increase total power is to combine many low-power light sources into an array. However, this method will cause the large volume of light source module, and there will be many restrictions on its use. The high power laser source is the only reasonable choice, especially for applications that require privacy and portability.
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2. Night Vision Simulation
The night simulation technology is a demand arising from IR night vision technology. It is mainly used in military training, flight simulation and other fields. In the same scene, the image formed by the reflection of visible light and IR will be quite different. This is because materials have different absorption and reflection factor for different wavelengths. If users of IR night vision devices have not undergone simulation training, they are likely to misinterpret IR images. This can lead to disastrous consequences in work that requires precision operations.
Fig. 2 Schematic diagram of IR laser projector for simulation training
IR laser projectors for simulation training were born in response to this demand. After storing the actual or simulated IR night vision scene records, the IR laser projector can project various screen data into the training place. This allows trainees equipped with IR night vision devices to learn how to judge and understand the image in a safe environment.
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3. 3D sensing
Since the iPhone X began to use the face ID recognition, 3D sensing is arguably the hottest area for IR laser applications in recent years.
Not only that, VR/AR, Light Detection and Ranging (LiDAR) and many other applications
3D sensing is not only used in mobile phone face recognition, VR / AR, Light Detection and Ranging (LiDAR) and many other applications are all built on 3D sensing technologies. The theory is to use a set of IR laser projector and matching receivers to calculate the environmental space based on the reflected data. At present, the main operating methods can be divided into Structure Light Type and Time of Flight (ToF) Type. The theory of structured light is to use a Diffractive Optical Element (DOE) to project a specific pattern of IR laser, when this pattern is projected onto the detected object, it will produce different distortion due to the appearance of the detected object and reflect into the receiver, and it can calculate the spatial information according to the signal. The iPhone X system belongs to this type.
ToF operates IR laser in pulse mode. The projected laser will pass through a diffuser to form a uniform light surface. After it encounters an object and reflects to the receiver, the system can calculate spatial information based on the time difference and phase change of the reflection light. Regardless of structure light type or ToF type, the detection range is positively related to the power of the light source. Short-range detection such as mobile phone face recognition, the light source only requires milliwatt (mW) level. And for long-range detection such as LiDAR for vehicles or unmanned aerial vehicles, it requires watt (W) level high-power light sources. Depending on the power of the laser light source used, it has different fields of use. As small as the sweeping robot to judge the obstacles in the room, as big as the aircraft to scan and draw the topographic map. It occupies a pivotal position in all spatial recognition applications. At the same time, it also gives a 3D vision to variety of unmanned automatic machinery, which will be a driving force that cannot be ignored for the future evolution of industrial technology.
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Suitable Product for IR Lighting Application
Currently, products suitable for IR light application, usually the following wavelengths: 808nm, 830nm, 850nm, 940nm. As the largest professional diode laser manufacturer in Taiwan, Arima Lasers Corp. has many years of experience in production and research and development of IR diode lasers. We can provide complete solutions for various needs and in the night vision applications and 3D sensing have commercial results.
Especially in recent years, Arima Lasers has focused on the development of high power laser products, and has launched 2W 808nm/830nm TO9 (Ø 9mm) package laser products, that can be applied to long range night vision technology. This product has a long service life, high reliability, and without catastrophic optical damage (COD). The Mean Time between Failure (MTBF) at an operating temperature of 60 °C is much higher than the standard 20,000 hours. It is suitable for various devices such as night vision monitor, IR assistant exposure light, laser projector, and so on.
>> High Power Lasers
For 3D sensing applicition, in addition to the TO-package products, Arima Lasers also launch a series of new Surface Mount Device Laser Diode (SMD LD) products in 2020. There are three wavelengths available: 830nm, 850nm, and 940nm. Because of sunshine interference, the wavelengths of 830nm and 850nm are suitable for equipment operating in a state without sunlight (night or indoor). However, the wavelength of 940nm in sunlight is easily absorbed by the moisture in the atmosphere and is difficult to transmit to the earth's surface. Therefore, it can get undisturbed data when using 940nm IR laser as the 3D sensing light source in outdoor.
>> SMD Products
In addition to the products that can be found on the website, Arima Lasers also provides customized design services. If you have requirements related to IR laser lighting and 3D sensing, please contact us.
>> Contact Us
Contact Author >> Chunwei_Mi@arimalasers.com
Author: Dr. Chun-Wei, Mi
Laser Application Dept. Associate Manager
