日本日立公司中央研究所制成了在直径0.5毫米的圆形基板上能存储2万位数字信息的全息照相存储器。这种存储器的存储密度是每1平方毫米10万位,和过去的存储器相比约提高1个数量级。由于提出了无规移相器——它能使信息光在存储面上均匀分布——的提案而使这种高密度存储得以实现。这种移相器能使几种类型的无规图案的矩阵相互交替地重迭在 The Hitachi Central Research Institute has made a holographic memory capable of storing 20,000 digital information on a circular substrate of 0.5 mm in diameter. The storage density of this memory is 100,000 bits per 1 mm2, which is an order of magnitude more than in the past memory. This high-density storage is achieved due to the proposal of a random phase shifter that enables information light to be evenly distributed across the memory plane. This phase shifter enables several types of randomly patterned matrices to be alternately superimposed on each other