Security Camera for Carbon Fiber Manufacturing Plant
I had engineer from a precision braid textile plant call a few days ago with an interesting request. It's not unusual to receive phone calls from experts in different industries. I've helped engineers at NASA, architects in New York, marine biologists in San Diego and everything in between. We usually get the same questions over and over. "How far can it see?" and "Will it read license plates?" are a few examples. Others simply collapse at our virtual doorstep when a human being answers the phone after combing through hundreds of sites like a forensic analyst.
With so much information about cameras on the web, it's easy to see why so many people have such a hard time choosing their devices. And I'm only referring to security cameras here. You still have video cameras, point and shoots, cell phone cameras, extreme sports cameras, SLRs, DSLRs, tablet cams, webcams, and even your fridge might have a camera now.
So when this customer from the textile plant called prepared with a very specific question about a lens, it was a little refreshing. It's much easier to visualize an application when the customer can describe the environment from the camera's point of view.
For those who don't know, the carbon fiber manufacturing process involves an intricate web of devices and machinery which stretches, heats, carbonizes, and treats the material with chemicals until the product is finished.
With each piece of equipment comes a long list of components which need to be calibrated, cleaned, and monitored. In this particular case, the customer wanted to see the texture of the material coming out of the press. A camera was already in place pointed at the feeder but the image quality was so low, he couldn't see the quality of the material coming out.
There are a few points to keep in mind here:
Because the material is moving out of the feeder at a fast speed, it is important the camera can handle fast moving objects effortlessly. This determines the fluidity, or "smoothness", of the video. In the customer's case, he needed something with high frame rate or he risked missing detail.
The existing camera was so close to the machinery, it had a hard time picking what to focus on. The adjusting the focal length on a security camera is like adjusting a pair of binoculars to focus on something far away. In the customers case, the focal length was really important because the camera had to be close to the machinery
The resolution of the sensor determines the amount of detail in an image. The image sensor inside the camera determines how much detail and light a camera can soak up. High quality sensors are very sensitive to light and know how to process it. Low quality sensors have a hard time processing light and where to display it on a monitor. Resolution was important in this case because with a high resolution image, the customer wouldn't see much detail.
So for this customer it was necessary to provide an example because it was too difficult to guarantee a good capture without testing it internally.Here I used a 720p camera with a 3.6mm fixed lens. What this means is that the image sensor produces 1280 × 720 pixel images. This is sometimes referred to as 1MP but not always. It is important to check the actual resolution of the camera in pixels. The camera produces the following viewing angle. Which in this case didn't matter as much since the object the customer was trying to capture was about 6 inches from the camera sensor.
The camera uses a Texas Instruments DaVinci media processor which produces 1MP images at 30 frames per second making it a good fit for this application. It also produces images faster than the human eye can process. So why record a video we can't process? So we can slow it down!!!. Using software you can slow the video down and capture even more detail from moving objects. So even though this customer couldn't see every single detail at real time, he could play back video at a slower speed and even analyze individual frames. As you can see in the image below, the camera was able to produce decent detail at 6 inches away. The $20 bill is 7 inches from the sensor. You can barely see it, but there is an ID card in the middle bottom of the screen with a bar code which is 6 inches away. The motion detector is about 10 inches away.
While this specific camera didn't produce enough detail for what the customer was trying to accomplish, it was enough to guarantee a good shot with the the 2MP camera which had the same focal length but higher amount of detail. Here are some other factors which play a role in capturing good video:
- Sensor Defects
But the message here is this: Great quality video happens when framerate, focal length, and resolution work in harmony. If you depend too much on one or the other, you have a vulnerability in your surveillance system and could risk losing valuable detail used to see someone's face, a license plate, or money going into a pocket.