The two wide bands (WIDE-S and WIDE-L) yield higher-quality images because they had a broader wavelength coverage than the two narrow bands (N60 and N160).

Difference maps based on the WIDE-S and WIDE-L data
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Since Galactic emission is strong in the far-IR regime, extraction of the faint dust bands from the far-IR maps is not a simple task. To measure the dust-band structure precisely, image-enhancing techniques were used. Fourier filtering is a commonly used technique to extract structures from an image (e.g., [@Sykes88; @Reach97]). However, it is likely that smooth and broad components of the dust-band structures are removed by Fourier filtering. Since the main aim of this paper is to construct ZE templates that can be subtracted from the AKARI far-IR images, we adopted the following approach to deduce the intensities and positions of the small-scale ZE structures.

The WIDE-S (90 $\micron$) maps include both IPD and interstellar dust emission, while the WIDE-L (140 $\micron$) maps, which cover longer wavelengths than their WIDE-S counterparts, mainly detect interstellar dust emission (IR Galactic cirrus). The dust grains in the asteroidal dust bands spiral inward from the main asteroid belt (located at a distance from the Sun of $\sim 2$–3 a.u.) 