Hello everyone. My name is Teppei of KOYO Orient JAPAN’s Product Division.
We receive many inquiries about our super light absorption sheet "FineShut” regarding its effectiveness in the prevention of internal reflection caused by Near-Infrared (NR) light. “FineShut” has mainly been utilized in Single-Lens Reflex (SLR) cameras so I asked myself, “What exactly is Infrared?” I immediately began to research about it. I’ve attended seminars and asked our customers about it and the more I learn about the world of Infrared, the more interesting it becomes. Today, I would like to share what I have learned with you.
So right off the bat, for those of you who are familiar with Infrared light please raise your hand…I see there are many. Great!
Next, for those of you who are familiar to how Infrared light is being used around us, please speak at your monitor…ok, I heard “TV Remotes”, “Heaters”, and “Security Cameras”. Yes, you are all correct!
Now as you can see here, there’s a broad range of uses for Infrared light to the point where you may get confused to what exactly Infrared light is.
Well don’t worry because in this blog, we’ll go over how Infrared light works and its applications!
What is Infrared light?
So, what exactly is Infrared light? Please refer to the chart below.
This is the Visible Spectrum. It’s the part of the Electromagnetic Spectrum that our eyes can visually recognize. The wavelengths of the Visible Spectrum range from 380 to 750 nanometers (nm). The shorter wavelength on the left-hand side of the spectrum (380nm) is recognized as Purple and the longer wavelength on the right-hand side of the spectrum (750nm) is recognized as Red. We can’t see anything above or below this range. Anything under 380 nanometers is known as Ultravoilet (UV) and anything above 750 nanometers is known as Infrared (IR).
*Image from Wikipedia page "Visible Spectrum"*
There are different categories of Infrared. There’s Near-Infrared (750-2500nm), Mid-Infrared (2500-4000nm), and Far-Infrared (4000nm~). We’ll go over this more in detail in other blogs however the important thing is that Near-Infrared and Far-Infrared have completely different properties and uses.
For this blog, let's deepen our understanding of "Near-Infrared" using a very familiar example.
Introducing the state-of-the-art "Near-Infrared" device...the iPhone!
Surprised? First off, let’s briefly go over Near-Infrared. The characteristics of Near-Infrared include “having properties close to visible light” and “invisible to human eyes.” Since the wavelength of Near-Infrared is close to visible light, large-volume, expensive devices such as sensors and cameras can be used as is and can be manufactured at low cost. Also, because we can’t see NR light, we won’t be irritated by it.
To give an idea of Near-Infrared applications in our daily lives, we have prepared an iPhone XR and a Near-Infrared camera.
We call this camera a “Near-Infrared” camera but we took a regular digital camera and modified it. Digital cameras have silicon sensors that can pick up electromagnetic waves longer than 750nm up to 1000nm. Remember, we can’t see anything above 750nm long. For that reason, these cameras also have a filter called an “IR Cut Filter” that doesn’t allow waves longer than 750 nm through in order to better match our eyes' ability.
So, we modified this camera by removing the IR cut filter and installed an
"IR Transmission Filter" that only allows wavelengths longer than 760 nm through. Ta-da! We have made an infrared camera.
Now back to the main subject. First, let’s unlock this iPhone using Face ID. The moment we touch the power button, the iPhone has already been unlocked. It was as if there weren’t any process of authentication. However, if we look at the iPhone through our NR camera…
FLASH! FLASH! FLASH!
You can see lots of flashing from the bezel on the top side of the phone! What is that?
If we project this flashing towards a wall, it turns out the identity of the flashing is a pattern made up of countless dots.
This flashing occurs when the iPhone is running facial recognition software or when creating Memojis.
This is the identity of the iPhone’s TRUE DEPTH. Its function is to measure the exact distance of the subject from the camera, that is, the three-dimensional shape of the subject.
We monitored the Dot Projector using our NR camera. More than 30,000 Infrared dots are emitted from the dot projector. Because the iPhone’s IR camera and the dot projector are located separately, the dots will be projected slightly off from the camera. As a result, each dot captured by the IR camera shifts horizontally depending on the distance of the subject. By calculating the degree of this shift, the distance of each dot can be determined. This 3D measurement method is known as the Active Stereo Method.
This method is used to grasp the three-dimensional shape of the subject's face and to improve the accuracy of the iPhone’s face authentication. Even if you are wearing sunglasses, you can pass the authentication as long as it’s something that transmits infrared rays to some extent. Have you ever used Memoji? This function can read the facial muscles of the subject in front of the camera, another technique that “True Depth” is capable of.
I’ll leave a video here for you to get a better idea. Here we are monitoring the iPhone using our NR camera.
Incredible, isn’t it? This distance recognition technology based on dot pattern projection can perform as well if used with visible light. However, if the flashing was visible, then it would just be an unpleasant experience for everyone.
Because this technology uses Near-Infrared light, state-of-the-art optical sensing can be implemented without anyone noticing.
Cheers to Apple's technology!
iPad Pro x LiDAR
If you thought that was cool, I have some more exciting news for everybody! I recently learned that the new iPad Pro will be equipped with LiDAR scanner! This will be the first optimized LiDAR device for Augmented Reality applications, for most people. Explosive development of LiDAR applications is expected. We expect the iPhone 12 to come equipped with LiDAR as well. This is incredible!
For those of you who are not familiar with LiDAR, don't worry because in this blog we'll be going over what LiDAR is and its applications.
LiDAR and Automatic Driving
In recent years, the automobile industry has reached a major turning point. Electric Vehicles you may ask? Yes, that is true, but the development of sensor technology has opened a way to achieve humanity’s dream of automatic driving.
One of the technologies that holds the key to achieving this dream is called “LiDAR.”
LiDAR stands for "Light Imaging Detection and Ranging". The L in “LiDAR” may also stand for Laser. The literal Japanese translation is "Detection and Ranging by Light." There have been proposals for the translation to be "Ranging Sensor".
In general distance measurement mechanisms, lasers are often used. When using a laser, a laser beam is radiated instantaneously, and if the laser beam hits an object, the light that hit the object returns and is received by the mechanism. In some cases, the distance to the target can be determined in no time using this mechanism. A laser rangefinder for golf is a good example for this.
LiDAR applies this and creates Point Cloud Data by repeating many observations in 2D or 3D in a short time. This makes it possible to grasp the shape of the space and the existence of the object. You will find it to be a very useful device for automatic driving.
Now that we understand the basic mechanism of LiDAR, what kind of performance is important for it to be utilized in automatic driving? For example, if the distance between the observation points is too wide, a narrow obstacle may pass between the lasers and may not be recognized. In order to narrow the interval, the number of measurements made in a set period will become very important.
Observation distancing is an important feature. Considering the braking distance of a car, accurate measurement of at least 100 meters is required.
However, the further the distance, the less light is reflected, and the more difficult it is to detect. Such refined light would be difficult to distinguish in an environment full of extraneous light “noise.”
Therefore, as a countermeasure, there is a method that increases the output of the laser to increase the reflected light, making detection easier.
However, with this method there is a big problem, that is, the damaging effect on the human eye. I’m sure you have all heard of malicious pranks using laser pointers. A strong laser light source that is focused on the fundus of your eye can cause serious damage to it.
The LiDARs currently being used mainstream uses near-infrared wavelength of 900 nm mainly for cost reasons, but this wavelength is close to visible light, so the same eye damaging danger is present (in the case of pulse emission). Therefore, in recent years, LiDAR has switched to using longer near-infrared wavelength of 1500 nm.
By switching to 1500nm the advantage is of course that the damaging effect on the eyes is minimal. Infrared light at 1500nm has an eye power 1 million times greater than visible light (pulse emission). This allows you to use a laser that is safe and sufficiently powerful for your eyes.
The disadvantage of using 1500nm is the price. Since the market is large and inexpensive photo-detectors, made of silicon, do not have sensitivity in the 1500nm range, it is necessary to prepare special ones made of InGaAs (Indium Gallium Arsenide). This material alone is several times more expensive than that of silicon. The price of a silicon LiDAR is said to be 100,000 yen or more. That can seem expensive for it to be installed in ordinary consumer cars. So the question is, how much would a high precision 1500nm LiDAR cost?
This cost and performance improvement of LiDAR is likely to be the key to future automatic driving. It is a field that is actively being studied by renowned large companies and venture companies in several countries, so I believe we will make great progress in the future.
Up until now, iPhones used "Dot Pattern Projection (Active Stereo Method)" to determine the subject's distance from the camera so you may wonder why LiDAR will be used in this new iPad instead. I wondered about that myself. I think that for the active stereo method to work properly, the camera and the projector need to be sufficiently separated, otherwise the measurement accuracy at long distances will be poor. Even if it is most suitable for face recognition applications in the range of 30 to 50 cm, it may not have matched the iPad Pro's measurement range of 5 m this time.
Click here for an introduction video of an application that utilizes LiDAR. It's amazing!
The future looks exciting! I am very excited to what new possibilities LiDAR will unlock!
Alright, let's move on to far-infrared.
The World seen in Far-Infrared Cameras
Japan is without a doubt, the world's largest camera nation. There are renowned camera and lens manufacturers, and they are producing cameras with excellent performance. However, even with the same optical equipment, the story seems to be different for Middle and Far Infrared cameras. If we visit related booths at an exhibition, most of them are industrial cameras from overseas manufacturers. Very few are made in Japan. Why is this the case?
According to a representative from an overseas manufacturer, it seems that mid-to-far infrared cameras are an industry that progresses closely in relation to the military, and research is progressing in the United States, France, and Israel. In Japan, there are various political situations.
Now, let's take a night vision scope as an example and go through the application examples of mid-far infrared cameras as they relate to the military, without any derailment.
First, a set of near-infrared light and near-infrared camera, which was introduced in the iPhone application example. If you take a picture of your opponent in this way, you can observe it without notice. This is the beginning of night vision scope. By illuminating the darkness with near-infrared light, you can find and attack enemies in an environment that looks bright and bright. It is wonderful.
But this has a major drawback.
If the opponent was watching with a similar near-infrared camera, the near-infrared light quickly turned into a brilliant target in the dark night. That makes no sense. After that, ultra-high-sensitivity visible light cameras that can be seen even in the slightest moonlight will appear, but breakthroughs have occurred in mid-far infrared technology.
As mentioned at the beginning, the mid-to-far infrared range is the wavelength range of the mid-infrared (2500 to 4000 nm) and far-infrared (4000 nm ~). Since the numbers are larger, the unit is not 2.5 nm, but generally 2.5 to 4 μm or 4 μm.
Heat is energy such as the vibration of atoms or molecules, and this wavelength range includes the frequency that resonates with this vibration. Vibration due to the heat of molecules is emitted as it is as mid-far infrared rays, and is absorbed and converted into heat.
The words often heard in commercials such as "warm warmth with the far-infrared effect." "Fire passes through the meat with the far-infrared effect." This is the characteristic of medium to far-infrared rays that transmits thermal energy.
In the case of observation using visible light to near-infrared light, there are not many objects that emit light by themselves, so the reflected light or transmitted light of objects illuminated by the sun or lighting equipment is usually observed. Obviously, you cannot observe the subject in a completely dark room.
However, in the mid-to-far infrared range, all objects emit mid-to-far infrared radiation unless they are at -273 ° C absolute zero. So you can observe in any darkness if there is only a temperature difference between the background and the subject. Thermography, which is sometimes seen on televisions, is an image obtained with a mid-to-far infrared camera. The world of the movie “Predator”!
It is very useful to be able to observe the heat itself. The body temperature of the creature, the engine of the vehicle, the firearm after foaming. Heat often contains important information on the battlefield.
I found an easy-to-understand video on how a mid-far infrared camera is effective as a night vision camera. See a comparison of images obtained with NIGHT VISION (probably a high sensitivity near infrared camera) and THERMAL (middle to far infrared camera).
Now, a mid-far infrared camera with such wonderful characteristics. One of the drawbacks is that noise suppression is very difficult.
Noise suppression from visible light to near infrared light is easy. If there is a place where extra reflection occurs, cover it with a black material that does not reflect. Our products are used for such purposes.
However, the story is troublesome when it comes to mid-far infrared light. What we observe is heat, but everything that is not the object of observation also emits heat. In other words, anything that is hot will be a source of noise. Even lenses and camera components.
If you make a camera with luminous materials, you can only shoot pure white images full of noise.
As such, the key to achieving high image quality with mid- to far-infrared cameras is to eliminate heat. One of the techniques taken is to take pictures while cooling the camera with liquid nitrogen. You can imagine it is a very large device.
However, the resulting image is highly accurate, and using the latest equipment, if the temperature difference between the atmosphere and the observation target is 0.1 ° C, it seems that a level of 100m can be created between a person 100m away from the atmosphere in the dark.
At present, with the advent of small cooling mechanisms such as Peltier devices, uncooled sensors, and advances in noise processing by software, the size, quality, and price of mid- to far-infrared cameras have been greatly advanced. Handy types that cost less than 100,000 yen are starting to appear. Mid-far infrared cameras have become very familiar.
There are various applications that can be applied by being able to visualize heat from the beginning, such as checking the thermal design of electronic circuits and finding water leaks on building exterior walls. In the future, it may be a tool that general companies and individuals can have. It is a fast growing product in the market in recent years.
You made it!
Thank you for reading all the way. In summary, we have explained the applications and examples of the invisible infrared region. Did you enjoy it?
Koyo Orient Japan is a company specializing in products and services that mainly absorb visible to near-infrared light. The products we handle are black, and our sales vehicles are black. In a sense, it is a “black company”, but we want to continue to brighten the future of optics through our products.
If you are having trouble with internal reflection in near-infrared optics, please visit "FineShut SP" and "FineShut KIWAMI" pages. For reflection measures limited to the visible light range, please go to the "Flock Sheet" page.
Thank you for reading and have a wonderful day!