•A new imaging biosensor technique based on photonic crystal surface modes (PCSMs) is presented.•The spectral shift of the PCSM resonance peak is detected by a standard color camera at each point of the PC chip surface.•The dynamic range of the biosensor in the adsorbate layer thickness is 150 nm and the baseline noise is 3.5 pm.•The first experiments using the device showed that the proposed imaging method can surpass its plasmonic analog (SPRi) with respect to both signal-to-noise ratio and dynamic range. A novel biosensing technique with a two-dimensional (2D) visualization, which is based on photonic crystal surface modes (PC SMs), is presented. The 2D image of the surface with picometer thickness resolution can be obtained when the PC chip under study is placed between crossed polarizers to convert a PC SM resonance dip into a resonance peak. The PC chip is designed so that the PC SM resonance peak is located between the maxima of the blue and green pixels of a color camera. The spectral shift of the resonance peak is determined by balancing of the intensities of the blue and green pixels at each point in the color camera. The spatial distribution of resonance wavelength shifts across the camera reflects the spatial distribution of changes in the thickness of the adsorbate over the sample. The spatial resolution of the resulting 2D image is determined by the propagation length of the PC surface wave.