Thermal imaging cameras have been widely used in many industries for decades: soldiers find targets through thermal sights, police install them on helicopters to search for people, and construction workers use sensors to find sources of cold air seeping into houses. To detect temperature deviations in surrounding things, today it is enough to purchase thermal imagers for smartphones or tablets in the form of a set-top box.
Jack of all trades
The hunt for Arnold Schwarzenegger in the 1987 classic Predator may not be your forte. But today there are enough uses for a thermal imager - to find a missing cat hiding in the dark under the porch, to diagnose a blocked pipe in the bathroom, or to see how much propane is left in the tank of a gas grill. These cameras allow us to see the previously unseen thermal landscape, revealing the amazing worlds around us.
There are also limitations. For example, glass transmits visible light well, but filters infrared radiation, which we call heat. This makes windows practicallyopaque to thermal imagers. The device can show the temperature of the glass surface, but if someone stands behind the window without touching it, then this person will remain almost invisible, although the thermal reflection in the glass can be seen. This is why thermal camera lenses are not made from regular glass, they require special materials such as germanium, which transmit infrared light.
The resolution is much lower than conventional multi-megapixel cameras built into smartphones today. The images are blurry and the video speed is slow. But with all this, the feeling of a person who looks into complete darkness and sees a living thermal landscape is simply indescribable.
Flir One vs Seek Thermal
If you search for a thermal imager for a smartphone on Google, then there are not many manufacturers. They can be counted on the fingers of one hand. Even a Chinese thermal imager for a smartphone is a rarity. Among this handful of manufacturers, Seek Thermal and Flir Systems are the most prominent. Their cameras can be connected to the phone jack. Seek has a size advantage: the Android smartphone thermal imager is smaller than a 9-volt battery, while the Flir One is slightly wider than the iPhone 5S and nearly twice as thick. Both devices are protected from damage when carried in a bag, but Seek is also waterproof and looks much more durable.
The Seek Thermal Smartphone Imager does not have a power switch, battery or charging port. This makes the camera design veryelegant, simple, without any additional cables or chargers. But it puts a serious strain on the phone's battery. Flir takes a different approach, with an internal battery that needs to be charged using the included mini USB cable. The battery lasts for an hour of continuous use.
Another difference that ultimately makes the FLIR the best choice for most people is that it has two cameras, a traditional VGA camera and a thermal one. The real-time image on the phone is composed of two channels. At the same time, the high-contrast contours of the full-color camera provide the necessary clarity of temperature clots. This is especially useful when you need to return to images later. Otherwise, it is difficult to understand what exactly is captured in the picture.
Both cameras are available for Lightning and Android devices with a micro-USB connector.
The Seek Thermal thermal imager for smartphones and tablets is a set-top box, while FLIR ONE is made in the form of a bumper for iPhone. Despite different form factors, the devices are united by high build quality, stable performance and user-friendly design.
FLIR ONE: thermal imager for smartphones. Description
In the first generation FLIR ONE, the VGA visible spectrum camera and the Lepton Far Infrared sensor were combined into a neat, detachable 'sled' that could be pulled out when needed. The bumper remained on the iPhone all the time, and the skids detached forcharging via micro USB. In models for iOS and Android, this solution was abandoned in favor of a separate set-top box.
Unlike Seek, which is powered by your phone, ONE has a built-in battery. It should be noted that ONE FLIR does not act as an external battery pack for iPhone, all power is consumed by the thermal sensor and camera.
This decision "fills" the slender profile of the iPhone 5s a little. The domed shape and cutout for the lens and flash make the soft polycarbonate construction visually heavier than it actually is.
Except for the two logos, the no-frills design matches the rest of the company's high-end products. The micro-USB port, charging status indicator, and headphone cutout are on the bottom, while the thermal imager, mode switch, and lens cap are on the back. A multicolor LED is mounted directly above the cameras to signal power status and successful calibration.
Slim bumper has cutouts for access to volume and mute keys, rear lens and Lighting port, speaker, headphone jack, microphone and even the Apple logo.
Seek Thermal: thermal imager for smartphones. Features
The Seek is about the size of a thumb and adds 2.5 cm to the overall height of the phone when plugged in. The thickness of the device is sufficient not to go too far beyond the profile of the smartphone.
Seekk's magnesium case is almost weightless, but it will take time toget used to the extra "chin". Since the iPhone's Lightning connector or Android's micro-USB is the only point of contact with the phone, the thin metal protrusion has the function of supporting the entire structure, meaning the module may simply fall off in a collision.
The external thermal imager for smartphone and tablet is attractive, small in size with concentric circles around the lens made of chalcogenide lens, a material commonly used in photonics. On traditional lenses, these ridges deflect reflected light, but here they are more for show.
Supplied with a sturdy case filled with thick protective rubber with a cutout for your device for secure transport protection.
MSX Technology
FLIR and Seek smartphone thermal imagers use completely different hardware and software.
As mentioned above, FLIR uses two specialized sensors to produce a hybrid thermal image. Marketed as MSX, the system combines VGA camera visual information and temperature data captured by FLIR's 80x60 Lepton sensor. This approach gives impressive results, giving a clear shape to blurry heat spots.
In practice, the dual sensor is calibrated so that there is no need to constantly adjust the parallax if the objects are at a sufficient distance from the phone (more than one meter).
In this case, MSX blending is imperceptible, but at close distances the parallax becomes more and moremore important issue. To compensate for this, the FLIR ONE Closeup application must be used, which allows users to manually adjust the MSX horizontal merge points. The program works in standard color modes, but lacks the finer adjustments offered by the main FLIR program, such as setting emissivity to adjust a material's ability to radiate thermal energy.
Useful tools
The image response is instant - the delay is felt only when panning. Photo processing is just as fast. Video recording starts immediately and the image adjustment tools provided by FLIR ONE are top notch. Of these, the most useful is the spot meter, which can decipher the heat signature value as a thermometer reading from any selected point.
There is one inconvenient aspect of the FLIR ONE's design, and that is the self-calibration mechanism. From time to time, the application requires you to slide down the switch located just below the dual lens. Since the finger, as a rule, is already in the desired position, this is not difficult to do, but the program asks you to perform this procedure all the time. Switching causes the whole phone to move, ruining the video quality.
Calibration resets the sensor, not the MSX parallax, so performing this adjustment operation is not essential for image quality. For accurate readings, however, periodic adjustment is necessary.
Reliable FLIR ONE software
FLIR, with its rich history of military and professional thermal imaging solutions, has provided its hardware with robust programs that allow different modes of operation, temperature display and more. Unfortunately, many features are distributed among different applications, which is not very convenient.
Obviously, some features may not be needed by users - professionals don't need a thermal panorama, but a lot of files clutter up the screen and require constant switching between programs to find the right tool. Consolidation is essential.
As for the applications themselves, FLIR ONE Paint, for example, allows you to paint an ordinary photo with thermal readings. The program splits the MSX photo data into two different images, which can then be blended manually.
FLIR ONE Timelapse is another useful tool that allows you to take photos at intervals of a few seconds or minutes and play them back in video mode.
True Temperature Sensor
The Seek Thermal Imager for Android smartphones uses a "true thermal sensor", or vanadium oxide microbolometer, capable of detecting far infrared radiation in the range of 7.2 to 13 microns. According to the datasheet, the sensor has a total of 32.136 thermal pixels on a 206-by-156 dot matrix.
The Seek and FLIR smartphone thermal cameras use completely different sensors. Since the former relies solely on the thermal sensor, its output image is globular and fuzzy. Without the sharp edges and contrasting tones of the dual-lens FLIR, Seek shots are deceptively blurry. With a higher pixel count, the True Thermal Sensor captures much more information than the Lepton FLIR.
Another area where Seek outperforms FLIR is in its detectable temperature range of -40°C to 330°C, and tests confirm this. The maximum that FLIR ONE is capable of is 100°C. When measuring temperatures well above 330°, the Seek software crashes and starts showing values in the tens of thousands of degrees. But this is most likely some minor mistake.
Instead of constantly manually resetting the temperature sensor, Seek performs this task automatically when the chamber temperature changes. The operation of the electromechanical shutter is accompanied by a slight click, but its audibility is minimal.
Seek offers 3 levels of IR sensitivity, detection, recognition and identification for distances of 300m, 75m and 45m. The 36° field of view is inconvenient when shooting up close. You can use the digital zoom, but the quality drops so much that it is almost impossible to use.
Rich features
The only Seek app is well-built, with many great features that will satisfy professionals and hobbyists alike. Along with several viewing modes - color, white, black, etc. - the program displays the maximum andminimum temperatures, which is very useful when searching for objects in the dark. A threshold mode is also available to detect heat signatures above a certain level, which is useful when used in hot environments such as the engine compartment of a car.
Thermal+ is similar to FLIR Paint and overlays temperature data on top of a normal image. Unfortunately, this feature uses the camera, which is 12cm away on the opposite end of the phone. The parallax is not calculated accurately, causing the image to align incorrectly.
Pros and cons
At $250 a thermal imager for an Android smartphone, the FLIR ONE may cost more than the phone it attaches to, but for some, the positional accuracy offered by MSX technology is worth it.
The Seek Compact is the same price and has a higher sensor resolution, although the pictures it produces are not as perfect.
FLIR ONE is a smartphone thermal imager with the most favorable user reviews. Customers love the MSX overlay for detailed images, its own battery pack, and powerful imaging software.
Among the disadvantages are the need for periodic sensor calibration, iPhone 5/5s-specific design of the bumper model, software broken into separate components.
Seek Thermal's positive quality is the presence of a fast self-calibrating sensor, and the negative is the narrow field of view and low image detail.
From the point of viewThe overall quality of the FLIR ONE is on par with the competition, but lags behind when it comes to heat detection. But what the Lepton sensor lacks in sensitivity, it makes up for with a VGA camera overlay for incredible detail. The FLIR ONE shots look amazing, and the software is solid, albeit fragmented. However, no matter which smartphone thermal imager is chosen, any one of them will provide a glimpse of a world never seen before, despite always being before our eyes.
