Near-infrared Reflection? A mystery in the world of infrared camera

ojisan photo took by an infrared camera

Digital camera and Near-infrared

Hi, I am Teppei at KOPRO product division.

As a feature of our anti-reflection material, "Fine Shut" series, "absorbing near-infrared" is one of our priding features.

 

First, what is the near-infrared in the first place? Humans can visually perceive electromagnetic waves in the wavelength range of 380 to 750 nm. The short wavelength up to 380nm is recognized as blue while the long wavelength up to 750nm is recognized as red. Wavelength range exceeding red 750 nm is called infrared.

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There are 4 types of infrared rays : Near-infrared (750 ~ 1400 nm), Short-wavelength infrared (1400 ~ 3000 nm), Mid-wavelength infrared (3000 ~ 8000 nm), Long-wavelength infrared (8000 nm~). This time we talk about the Near-infrared.

 

As mentioned earlier, infrared rays are not visible. However, this changes a bit when it comes to digital camera sensor. The sensor of the digital camera has a wider wavelength range that can be captured by human eyes. It captures infrared rays.

 

Therefore, (in many camera models) an infrared cut filter is attached in front of the sensor to attenuate the closed-range infrared and bring it closer to the human eye.

It seems that there is a difference on the design concept on which wavelength range to cut. Depending on the manufacturer, there are cameras that can easily see closed-range infrared (for example, Fujifilm X-trans CMOS). These cameras are especially popular with astro-photographers.

 

Although introduction became longer, I removed the infrared cutting filter, and use a visible light range filter (IIR76) to test out the close-range infrared sensitivity and light reflection of the digital camera. Let me show you the results.

Difference in appearance of visible light and Near-infrared

photo of a man holding FineshutKIWAMI took by normal camera

I tried to take my picture in the middle of one fine day during spring. I wore my favorite Kawasaki cap and black Fleece sweater thinking I am a fashionable middle-aged man.

 

Joking aside, this is an example of a normal digital camera image. It is taken using Fujifilm's X-H1. I am holding a FineShut KIWAMI sheet (cut in a rectangular shape) on my left hand. FineShut KIWAMI cannot be distinguished at all in this picture.

 

Take a look at the next picture. It is an image taken simultaneously from an infrared camera.

photo of a man holding FineshutKIWAMI took by infrared camera

This means that the fleece jacket and cap were absorbing light in the visible light region and then reflected near-infrared rays. This results into an image where most of the colors changed to white. The plants behind me are also white, which is completely different from the picture above.

 

This time, I can also clearly see the Fineshut KIWAMI I have in my hand. This picture shows the effect of near-infrared in colors of a picture. 

comparison of photos took by normal camera and infrared camera

After which, I made the usual color photo into black and white. The difference is clear when you try to have them side by side.

 

 

The fleece jacket I wore this time was 100% polyester. In this way, even though synthetic fiber has high light absorption performance in the visible light range, it often reflects the close-range infrared in full. This shows that our FineShut KIWAMI is "strong in the near-infrared!"

Product introduction of the fine shut series, please purchase from here!

>>Near-infrared total reflectance 1.2 to 1.8% Fineshut SP

>>Near-infrared total reflectance 0.7 to 1.1% Fineshut KIWAMI

Finally

As mentioned above, I talked about the near-infrared in this blog.

It is commonly used for inspection of food and product inspection which is usually set with visible light. For example, sensors for automatic driving utilizes the function as a night vision camera. Optical use of near-infrared has received great attention in recent years.

 

However, recent anti-reflection material corresponding to the close-range infrared has been underdeveloped over the years. Our FineShut Series is a very effective and easy-to-use material, so I hope you take advantage of it.

 

Finally, I will also upload a photo of a shrine close to our company. Which is an infrared photo?  

See you on the next blog.

infrared camera took a photo of Japanese shrine

>> CHECK Ultra black sheet Finesut SP and Fineshut KIWAMI pages!!