Holographic operating optical apparatus

An optical correlation apparatus for effecting optical correlation processing of two-dimensional images using coherent light so as to automatically carry out recognition and measurement of a given pattern, comprising:

• means for converting at least one code image and at least one input image into a corresponding coherent code image and a corresponding coherent input image;
• means for independently Fourier transforming the coherent code image and the coherent input image into a Fourier code image and a Fourier input image;
• means for enabling a coherent reference light of spherical wave or plane wave form to interfere with the Fourier code image to form a Fourier code hologram;
• means including a binary spatial light modulator for converting the Fourier code hologram into a binarized intensity hologram image and recording the same;
• means for reading the binarized intensity hologram recorded on the binary spatial light modulator using the Fourier input image;
• and
• means for Fourier transforming the read binarized intensity hologram into a correlation image and for converting the correlation image into a corresponding output signal.

A method of driving an optical correlator having means for converting at least one code image and at least one input image into a corresponding coherent code image and a corresponding coherent input image, means for Fourier transforming the coherent code image and the coherent input image independently of each other into a Fourier code image and a Fourier input image, means for enabling a coherent reference light having a spherical wave or plane wave form to interfere with the Fourier code image to form Fourier holographic fringes, a light addressed ferroelectric liquid crystal light valve for binarizing the Fourier holographic fringes and recording them in the form of a binarized intensity hologram, wherein the light valve comprises a hydrogenated amorphous silicon photoconductive layer, an optical reflection layer having a given transmittance, a pair of liquid crystal alignment layers, a ferroelectric liquid crystal layer having bistable memory characteristics between its reflectivity and an applied voltage, means for applying the voltage and a pair of transparent substrates, means for reading the binarized intensity hologram recorded on the light addressed ferroelectric liquid crystal light valve using a reading light from the Fourier input image, and means for Fourier transforming the read binarized intensity hologram into a correlation image and for photoelectrically converting the correlation image into a corresponding output signal, the method comprising the steps of:

• continuously irradiating the light addressed ferroelectric liquid crystal light valve with a writing light to form the Fourier holographic fringes;
• continuously irradiating the light addressed ferroelectric liquid crystal light valve with the reading light to form the Fourier input image;
• continuously applying to the light addressed ferroelectric liquid crystal light valve a pulse voltage having a voltage polarity relative to the hydrogenated amorphous silicon photoconductive layer which is sequentially and cyclically changed between positive, negative and zero voltages, whereby erasing of the image is carried out when the positive voltage is applied, writing of the image is carried out when the negative voltage is applied and reading of the image is carried out when either the negative voltage or zero voltage is applied;
• and controlling the pulse voltage to adjust its amplitude, frequency and pulse width when the positive, negative and zero voltages are applied so as to regulate an intensity of the correlation image.

A method of driving a holography apparatus of a Fourier transform type having means for converting at least one input image into a corresponding coherent input image, means for Fourier transforming the coherent input image into a Fourier input image, means for enabling a coherent reference light having a spherical wave or plane wave form to interfere with the Fourier input image to form Fourier holographic fringes, a light addressed ferroelectric liquid crystal light valve for binarizing the Fourier holographic fringes and recording them in the form of a binarized intensity hologram, the light valve being composed of a hydrogenated amorphous silicon photoconductive layer, an optical reflection layer having a given transmittance, a pair of liquid crystal alignment layers, a ferroelectric liquid crystal layer having bistable memory characteristics between its reflectivity and an applied voltage, means for applying the voltage and a pair of transparent substrates, means for reading the binarized intensity hologram recorded on the light addressed ferroelectric liquid crystal light valve using a coherent reading light having spherical wave or plane wave form, and means for Fourier transforming the read binarized intensity hologram image into a reconstructed image and for photoelectrically converting the reconstructed image into a corresponding output signal, the method comprising the steps of:

• continuously irradiating the light addressed ferroelectric liquid crystal light valve with a writing light which forms the Fourier holographic fringes and with the coherent reading light of spherical or plane wave form;
• continuously applying to the light addressed ferroelectric liquid crystal light valve a pulse voltage having a voltage polarity relative to the hydrogenated amorphous silicon photoconductive layer which is sequentially and cyclically changed between positive, negative and zero voltages, whereby erasing of the image is carried out when the positive voltage is applied, writing of the image is carried out when the negative voltage is applied and reading of the image is carried out when either the negative voltage or the zero voltage is applied;
• and controlling the pulse voltage to adjust its amplitude, frequency and pulse width when the positive, negative and zero voltages are applied so as to regulate an intensity or quality of the reconstructed image.

A method of driving a holographic apparatus having means for converting at least one input image into a corresponding coherent input image, means for enabling a coherent reference light having a spherical wave or plane wave form to interfere with the coherent input image to form holographic fringes, a light addressed ferroelectric liquid crystal light valve for binarizing the holographic fringes and recording them in the form of a binarized intensity hologram, the light valve being composed of a hydrogenated amorphous silicon photoconductive layer, an optical reflection layer having a give transmittance rate, a pair of liquid crystal alignment layers, a ferroelectric liquid crystal layer having bistable memory characteristics between its reflectivity and an applied voltage, means for applying the voltage and a pair of transparent substrates, means for reading the binarized intensity hologram recorded on the light addressed ferroelectric liquid crystal light valve using a coherent reading light of spherical or plane wave form, and means for converting the read binarized intensity hologram into a corresponding output signal, the method comprising the steps of:

• continuously irradiating the light addressed ferroelectric liquid crystal light valve with a writing light to form the holographic fringes;
• continuously irradiating the light addressed ferroelectric liquid crystal light valve with the coherent reading light of spherical or plane wave form;
• continuously applying to the light addressed ferroelectric liquid crystal light valve a pulse voltage having a voltage polarity relative to the hydrogenated amorphous silicon photoconductive layer which is sequentially and cyclically changed between positive, negative and zero voltages, whereby erasing of the image is carried out when the positive voltage is applied, writing of the image is carried out when the negative voltage is applied and reading of the image is carried out when the negative voltage or zero voltage is applied;
• and controlling the pulse voltage to adjust its amplitude, frequency and pulse width when the positive, negative and zero voltages are applied so as to regulate an intensity or quality of the image.