Scale used: the SEM information bar (read by OCR and pixel analysis) shows 15.0 kV, x5,000, WD 10.0 mm and a scale bar labelled 1 um. The bar is 53 px long (x = 1202-1254), so 1000 nm / 53 px = 18.9 nm per pixel (the 1280 px width is about 24 um). The TIFF has no usable calibration metadata (72 dpi only), so the bar was the scale.

Method: I analysed the image area only (rows 0-959, excluding the info bar). I subtracted a Gaussian background (sigma 40 px), applied a Hann window and took the 2D FFT. I zero-padded x4 to refine the peak position.

Result: the dominant spectral peak sits at a spatial frequency of 0.0211 cycles/px, a period of about 47.4 px, which is about 894 nm. The 1D profile along x gives about 909 nm. The peak is sharp and its power is about 9x that of the next peak, which is a weak long-range modulation near 3 um. Uncertainty is about +/-3% from the FFT bin width and the bar-length measurement, so the period is about 0.9 um.

Orientation: the wave vector lies about 2 degrees from the image x-axis. The structures are therefore periodic along the horizontal direction, and the ridges/stripes run essentially vertically in the image, tilted about 2 degrees from the vertical (parallel to the y-axis).

RESULT: period = 894 nm
