Based on the lens function of the volume holographic grating,a device with both spectral and imaging function is recorded using a plane wave front and a convergent spherical one.Thus the spectrum is formed without a lens to focus the spectrum on the output plane.The effect of dispersion of the LiNbO_3 on the elements is considered in the design process.Experiment on the fabrication of 8-channel imaging spectral device is presented,including the real-time control of the recording time schedule.The width of the whole output spectrum on the screen is as small as 8 mm.