Imaging live humans through smoke and flames using far-infrared digital holography

Abstract

The ability to see behind flames is a key challenge for the industrial field and particularly for the safety field. Development of new technologies to detect live people through smoke and flames in fire scenes is an extremely desirable goal since it can save human lives. The latest technologies, including equipment adopted by fire departments, use infrared bolometers for infrared digital cameras that allow users to see through smoke. However, such detectors are blinded by flame-emitted radiation. Here we show a completely different approach that makes use of lensless digital holography technology in the infrared range for successful imaging through smoke and flames. Notably, we demonstrate that digital holography with a cw laser allows the recording of dynamic human-size targets. In this work, easy detection of live, moving people is achieved through both smoke and flames, thus demonstrating the capability of digital holography at 10.6 μm.

Speckle pattern processing by digital image correlation

“…The objects under control can be living organisms as well as various machine parts during the process of their manufacturing or their operation. Promising technics of remote control and at the same time nondestructive testing are the optical methods, and specifically methods based on the use of coherent radiation [1][2][3][4][5][6].…”

Speckle interferometry in the long-wave infrared for combining holography and thermography in a single sensor: applications to nondestructive testing: The FANTOM Project

“…One advantage of LWIR DH is the possibility of reconstructing numerically objects larger than in visible DH (for a given distance between the object and the sensor) because the ratio of the wavelength and pixel size is generally 5 to 10 times larger in LWIR [7] [10] . Recently it was demonstrated that lensless LWIR DH can capture laser light reflected by humans illuminated through smokes and flames and reconstruct numerically images of sufficient quality to recognize the presence of people located beyond [11] . An up-to-date review of applications based on specific features of LWIR DH can be found in [12].…”

One-step reconstruction of assembled 3D holographic scenes

“…The possibility of optically or digitally processing the light coming from an object or from optical systems allows both studying the properties of the object itself or the developing of areas such as three-dimensional (3D) surface optical imaging [2], pattern recognition [3], and optical security [4], to mention just few of them. Optical processing systems can be divided into two categories: experimental [5][6][7][8][9][10][11][12][13][14] and virtual [15][16][17]. One of the main tools for such development of experimental systems is digital holography, where the light scattered or transmitted from the object or from an optical system is recorded in a sensor and then digitally or optically processed [18][19][20].…”

“…By using digital holography is possible to record and to process information of bidimensional (2D) [18,19] or 3D objects [18,20]. Recent advances show that digital holographic techniques can be further applied to imaging live humans through smoke and flames [9], or to obtain a full color natural light holographic camera [10].…”

“…Powerful tools have been developed for processing optical holograms [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. In the context of experimental optical encryption of 2D objects a filtering and positioning process were successfully applied for security purposes.…”