Among light emitting and sensitive element pairs arranged along rows and columns of a matrix in each of first and second layers of an optical computer operable as a neural network with one-to-one correspondence kept between the pairs in the first layer and the pairs in the second layer, the light emitting elements and the light sensitive elements are connected along the rows in the first layer and along the columns in the second layer. Optical intensity controlling elements of a panel are placed in optical paths defined by the pairs in the first layer and the pairs which correspond in the second layer to the pairs of the first layer, respectively. When the light emitting element rows are driven, optical beams are emitted by the light emitting elements of the first layer and controlled by the respective controlling elements to have first-layer controlled amounts of light, respectively. In response to the controlled amounts of light, the light sensitive element columns of the second layer produce second-layer output signals. It is possible to use the second-layer output signals in controlling the controlling elements and thereby to train the optical computer. If desired, the light emitting element columns of the second layer are driven by the second-layer output signals to make the light sensitive element rows of the first layer produce first-layer output signals and to use the first-layer output signals in controlling the controlling elements.
Optical neural net trainable in rapid time