def get_qpimage_raw(self, idx=0):
        """Return QPImage without background correction"""
        name = self._get_experiments()[idx]
        with h5py.File(name=self.path, mode="r") as h5:
            exp = h5["Experiments"][name]
            # hologram data
            data = exp["data"][:]
            # resolution
            rx = exp["axis-0"].attrs["scale"]
            ry = exp["axis-1"].attrs["scale"]
            if rx != ry:
                raise NotImplementedError("Only square pixels supported!")
            runit = exp["axis-0"].attrs["units"]
            if runit == "nm":
                pixel_size = rx * 1e-9
            else:
                raise NotImplementedError("Units '{}' not implemented!")

        meta_data = {"pixel size": pixel_size}
        meta_data.update(self.meta_data)

        qpi = qpimage.QPImage(data=data,
                              which_data="hologram",
                              meta_data=meta_data,
                              holo_kw=self.holo_kw,
                              h5dtype=self.as_type)
        # set identifier
        qpi["identifier"] = self.get_identifier(idx)
        return qpi