Thermal imagers for smartphones and tablets: description and characteristics

Thermal imaging cameras are widely used in many industries for decades: soldiers find targets through thermal sights, police install them on helicopters to search for people, and builders use sensors to find sources of cold air that seeps into homes. 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.

Handyman

Perhaps the hunt for Arnold Schwarzenegger in the 1987 classic "Predator" is not your horse. But today the methods of application for a thermal imager is enough - to find the missing cat hiding in the dark under the porch, to diagnose the blockage of the pipe in the bathroom or to see how much propane remains in the gas grill tank. These cameras allow you to see an invisible earlier thermal landscape, revealing the amazing worlds around us.

There are also limitations. For example, the glass is good for transmitting visible light, but it filters infrared radiation, which we call heat. This makes the windows virtually opaque for thermal imagers. The device can show the temperature of the glass surface, but if someone is standing behind the window without touching it, then this person will remain almost invisible, although you can see the heat reflection in the glass. That is why the thermal camera lenses are not made of ordinary glass, they require special materials, such as germanium, which transmit light in the infrared range.

Their resolution is much lower than that of conventional multi-megapixel cameras built into smartphones today. Images are blurred and the video speed is small. But with all this, the sensations of a person who looks into total darkness and see a living thermal landscape are simply indescribable.

Flir One vs. Seek Thermal

If you look 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 group of manufacturers, the most famous are Seek Thermal and Flir Systems. Their cameras can be connected to the phone jack. Seek has the advantage in size: the thermal imager for an Android-based smartphone is less than a 9-volt battery, while the Flir One is slightly wider than the iPhone 5S and is almost twice as thick. Both devices are protected from damage when worn in a bag, but Seek is also waterproof, and looks much stronger.

Thermal Imager for smartphone Seek Thermal power switch, battery or port for charging does not. Thanks to this the design of the camera is very elegant, simple, without any additional cables or chargers. But it has a serious load on the phone's battery. Flir has a different approach, with an internal battery that needs to be charged with the supplied mini USB cable. The battery lasts for an hour of continuous use.

Another difference, which ultimately makes FLIR the best choice for most people, is the presence of two cameras - traditional with VGA resolution and thermal. In real time, the image on the phone is made up of two channels. In this case, the high-contrast contours of the full-color camera provide the necessary clarity of the temperature clots. This is especially necessary when you need to return to the images later. Otherwise, it is difficult to understand what exactly is captured in the picture.

Both cameras are available for devices that use the Lightning interface and for Android devices with a micro-USB connector.

In the form of a thermal imager for a smartphone and a tablet Seek Thermal is a prefix, and FLIR ONE is designed as a bumper for the iPhone. Despite the different form factors, the device combines high quality assembly, stable operation and convenient design.

FLIR ONE: a thermal imager for smartphones. Description

In the first generation of FLIR ONE, the VGA-camera for the visible spectrum and the long-wave infrared sensor Lepton were combined in the form of neat removable "sled", which can be pulled out if necessary. The bumper remained on the iPhone all the time, and the "skids" were disconnected for charging via micro-USB. In the models for iOS and Android, this decision was discarded in favor of a separate set-top box.

Unlike Seek, which is powered by the phone, ONE has a built-in battery. It should be noted that ONE FLIR does not act as an external battery pack for the iPhone, all energy is consumed by a temperature sensor and a camera.

This solution is a bit "full" of the slender profile of the iPhone 5s. The convex shape and cutout for the lens and flash visually weight the soft polycarbonate construction more than it really is.

In addition to the two logos, the design without excesses corresponds to the design of the rest of the company's high-quality products. A micro-USB port, a charging status indicator and a headphone cutout are located at the bottom, and a thermal imager, a mode switch, and a lens cap are located at the rear. A multi-color LED is installed directly above the cameras for signaling the power status and successful calibration.

On the thin bumper there are cutouts for access to the volume and mute buttons, the rear lens and the Lighting port, the speaker, the headphone jacks, the microphone and even the Apple logo.

Seek Thermal: a thermal imager for smartphones. Characteristics

By the size of Seek does not exceed that of the thumb and in the connected state adds 2.5 cm of the overall height of the phone. The thickness of the device is sufficient to not go beyond the profile of the smartphone.

Magnesium body Seek almost weightless, but it will take time to get used to the additional "chin". Since the Lightning iPhone or micro-USB Android connector is the only point of contact with the phone, a thin metal ledge carries the function of supporting the entire design, that is, the module can simply fall off when a collision occurs.

Externally, the thermal imager for the smartphone and tablet is attractive, small in size with concentric circles around the lens of the chalcogenide lens, the material that is commonly used in photonics. On traditional lenses, these crests deflect reflected light, but here they are more for the species.

The kit includes a sturdy case filled with a dense protective rubber with a recess under the device for reliable protection during transportation.

MSX Technology

Thermal imagers for smartphones FLIR and Seek use completely different hardware and software.

As mentioned above, FLIR uses two dedicated sensors to output a hybrid thermal image. Promoted under the name MSX, the system combines the visual information of the VGA camera and the temperature data captured by the FLTI 80x60 Lepton matrix. This approach gives impressive results, giving a clear form to blurred thermal 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).

At the same time MSX-mixing is imperceptible, but at close distances, parallax becomes an increasingly important problem. To compensate for this, you must use the FLIR ONE Closeup application, which allows users to manually configure the MSX merge points horizontally. The program works in standard color modes, but it lacks the more subtle settings offered by the main FLIR program, such as setting emission factors to adjust the ability of a material to emit thermal energy.

Useful Tools

The response of the image is instantaneous - the delay is felt only when panning. Processing photos is just as fast. Video shooting starts without delay, and the image adjustment tools provided by FLIR ONE are high-end. Of these, the most useful is a point meter that can decipher the value of the thermal signature in the form of a thermometer reading at any selected point.

There is one inconvenient aspect of the FLIR ONE design - it's a self-calibration mechanism. From time to time, the application requires you to slide down the switch located just below the double lens. Since the finger, as a rule, is already in the desired position, it is easy to do, but the program asks to perform this procedure constantly. Switching makes the whole phone move, which spoils the quality of the video recording.

Calibration resets the sensor, not MSX-parallax, so performing this adjustment operation is not so necessary for image quality. For accurate readings, however, periodic adjustment is necessary.

Reliable FLIR ONE software

FLIR company, with its rich history of military and professional thermal imaging solutions, has provided its hardware with reliable programs that allow various modes of operation, ways of displaying temperatures and much more. Unfortunately, many features are distributed between different applications, which is not very convenient.

It is clear that some functions may not be necessary for users - professionals do not need a thermal panorama, but a lot of files clutter the screen and require constant switching between programs in order to find the right tool. Consolidation is simply necessary.

As for the applications themselves, FLIR ONE Paint, for example, allows you to paint the thermal indication of an ordinary photo. The program splits the MSX-data of the photo into two different images, which can then be mixed manually.

FLIR ONE Timelapse is another useful tool that allows you to take pictures at intervals of a few seconds or minutes and play them in video mode.

True temperature sensor

The thermal imager for Android smartphones Seek uses a "true temperature sensor", or vanadium oxide microbolometer, capable of detecting long-wavelength infrared radiation in the range of 7.2 to 13 microns. According to the technical specification, the sensor has a total of 32,136 thermocouples per matrix of 206 by 156 pixels.

Thermal imagers for smartphones Seek and FLIR use completely different sensors. Since the first relies solely on the thermal sensor, its output image is spherical and fuzzy. Without sharp boundaries and contrasting tones, like the two-lens FLIR, the pictures of Seek are deceptively blurred. With a higher number of pixels, True Thermal Sensor removes much more information than Lepton FLIR.

Another area in which Seek is superior to FLIR is the range of detectable temperatures -40 ° C to 330 ° C, and the tests confirm this. The maximum that FLIR ONE is capable of is 100 ° C. When the temperature is much higher than 330 °, the Seek software fails and starts to show values of tens of thousands of degrees. But this, most likely, is some slight mistake.

Instead of a permanent manual reset of the temperature sensor, Seek performs this task automatically when the temperature of the camera changes. The operation of the electromechanical shutter is followed by a small click, but its audibility is minimal.

Seek offers 3 levels of IR sensitivity, detection, recognition and identification for distances of 300, 75 and 45 m. The field of view at 36 ° is inconvenient when shooting near. You can use a digital zoom, but the quality is so low that you can not use it.

Rich Opportunities

The only Seek app is well-tuned, with many great features that will satisfy both professionals and amateurs. Along with several viewing modes - color, white, black, etc., - the program displays the maximum and minimum temperatures, which is very useful when searching for objects in the dark. A threshold mode is also available for detecting thermal signatures above a certain level, which is useful when used in hot environments, such as the engine compartment of a car.

The Thermal + program is similar to the FLIR Paint application and superimposes temperature data over a normal picture. Unfortunately, this function uses a camera that is 12 cm on the opposite end of the phone. Parallax is not calculated accurately, as a result of which the image is mismatched.

Advantages and disadvantages

At $ 250, the thermal imager for an Android smartphone FLIR ONE can cost more than the phone to which it is attached, but for some, the position accuracy offered by MSX technology is worth it.

The Seek Compact price is the same and the device has a higher resolution sensor, although the images it creates are not so perfect.

FLIR ONE - a thermal imager for a smartphone, user reviews about which are most benevolent. Buyers are delighted with MSX-imposition, detailing the image, having its own battery and powerful visualization software.

Among the shortcomings - the need for periodic calibration of the sensor, specific to the iPhone 5 / 5s design of the bumper model, software, broken into separate components.

The positive quality of Seek Thermal is the presence of a fast self-calibrating sensor, and negative - a narrow field of view and a small detail of the image.

In terms of overall quality, FLIR ONE is on par with competitor, but lags behind when it comes to thermal radiation recognition . But the lack of sensitivity of the Lepton sensor is compensated by superimposing a VGA camera on the image, which allows achieving incredible detail. The FLIR ONE images look amazing, and the software is reliable, though fragmented. Nevertheless, which thermal imagers for smartphones would not have been selected, any of them will allow us to look at a world that has never been seen before, even though it was always before our eyes.