Transmission and reception of pictorial information in digital form generally requires high data rates that impact on minimum channel bandwidths, on signal power levels, or both. The advent of optical fibers for signal transmission has reduced channel bandwidth constraints, however signal power requirements have oftentimes limited system performance in practical applications. Coherent signal detection techniques, (similar to those implemented in microwave radio systems), have positively impacted on the performance of optical front-ends used in certain digital receivers. In this paper, the use of multifrequency/multiphase signals for digital image transmission is proposed, in order to achieve high data throughput with moderate bandwidth and power requirements, while implementing coherent demodulation and a "direct bit detection" receiver. The proposed system utilizes 16 tone-quadriphase signals, to produce 64 signals, each representing 6 data bits. For image transmission at 6 bits per pixel, this scheme is attractive because bits represented by each signal, are recovered simultaneously using a novel "direct bit detection" scheme. It involves receiver coherent demodulation, dual correlations, and binary comparison operations made against zero thresholds. This results in a receiver signal processing algorithm that is independent of input signal-to-noise ratio. The receiver's bit error rate is derived and evaluated, and performance plots are presented showing system efficiency.