Military infrared (IR) imaging systems utilize one or more IR wavelength-bands, among short wavelength IR (SWIR), middle wavelength IR (MWIR), and long wavelength IR (LWIR) band. The IR image wavelength-band conversion which transforms one arbitrary IR wavelength-band image to another IR wavelength-band image is needed for IR signature modeling and image synthesis in the IR systems. However, the IR wavelength-band conversion is very challenging because absorptivity and transmittance of objects and background (atmosphere) are different according to the IR wavelength band and because radiation and reflectance characteristics of the SWIR are very different from the LWIR and MWIR. Therefore, the IR wavelength-band conversion in this paper applies to only IR targets and monotonous backgrounds at a long distance for military purposes. This paper proposes an IR wavelength-band conversion method which transforms one arbitrary IR wavelength-band image to another IR wavelength-band image by using the surface temperature estimation of an object and the error attenuation method for the estimated temperature. The surface temperature of the object is estimated by an approximated Planck’s radiation equation and the error of estimated temperature is corrected by using the slope information of exact radiance along with the approximated one. The corrected surface temperature is used for generating another IR wavelength-band image. The verification of the proposed method is demonstrated through the simulations using actual IR images obtained by thermal equipment.

Infrared (IR) target signatures and background scenes are mainly used for military research purposes such as reconnaissance and detection of enemy targets in modern IR imaging systems like IR search and track (IRST) system. For understanding and analyzing IR signatures and backgrounds in the IR imaging systems, an IR wavelength band (WB) conversion which transforms an arbitrary WB image to another WB is very important in the absence of equipment by WB. In addition, IR image synthesis of targets and backgrounds can provide a great deal of information in the IR target detection field. However, the WB conversion is actually a very challenging research due to lack of information on the absorptivity and transmittance of enormous components of an object or atmosphere. In addition, the radiation and reflectance characteristics of short-wave IR (SWIR)-WB are very different from those of long-wave IR (LWIR)-WB and middle-wave IR (MWIR)-WB. Therefore, the WB conversion in this paper is limited only to IR target signatures and monotonous backgrounds, which is commonly used for military purposes, at a long distance. This paper proposes an IR synthesis method for generating a synthesized IR image of three IR-WBs by synthesizing an IR target signature and a real background scene for an arbitrary IR-WB. In the proposed method, each temperature information is first estimated from an IR target signature and IR background image for an arbitrary IR-WB, and then a synthesized temperature image is generated by combining the respective temperature information estimated from the IR target signature and background scene. Finally, the synthesized temperature image is transformed into an IR radiance image of three IR-WBs. Through the proposed method, various IR synthesis experiments are performed for various IR target signature and background scenes.

생산적 적대 신경망(generative adversarial network) 학습 기반의 영상 변환은 낮 영상을 밤 영상으로 재생하는 방법 등에 활용될 수 있다. 그러나 어두운 밤 영상을 낮 영상으로 변환하는 반대의 경우, 영상에서 손실된 정보를 예측하여 다시 생성하기 때문에 낮 영상을 밤 영상으로 변환할 때보다 많은 문제를 노출한다. 본 논문에서는 pix2pix 기법을 기반으로 하여 밤 영상을 낮 영상으로 변환하는 방법을 제안한다. 제안한 방법은 기울기 소실(gradient vanishing) 문제를 해결하기 위하여 pix2pix 은닉 유닛 수를 최적화하고 가상의 밤 영상에 대한 학습 데이터를 만들기 위하여 촬영된 낮 영상의 노출 값을 조절하였다. 실험 결과는 제안된 방법이 pix2pix와 Cycle GAN보다 정답 영상(ground truth)과 비교한 MOS(mean opinion score)와 PSNR(peak signal-to-noise ratio) 지표에서 우수한 결과를 보여준다.