US 8,149,486 B2 · Recording device, recording/reproducing method, and reproducing method

Abstract

A hologram recording and reproduction method is configured such that the number of values which can be implemented per one pixel is increased from two according to a conventional method to three or more to achieve increase of the data recording capacity. While two values are conventionally represented by two different values of “0” and “1” of the amplitude, for example, phases “0” and “π” are combined with the amplitudes “0” and “1” thereby to make it possible to represent three values of “0,” “1” and “−1” (amplitude “1”×phase “π”). In particular, a two-value data train of “0” and “1” is converted into another data train of three values of “0,” “1” and “−1” in accordance with a rule for encoding determined in advance, and the amplitude “0” is allocated to pixels of the value “0”; the amplitude “1” (phase “0”) is allocated to pixels of the value “1”; and the amplitude “1” and the phase “π” are allocated to pixels of the value “−1,” to carry out recording. Increase of the data recording capacity can be achieved thereby.

Claims15

Dependent claims

A recording apparatus for carrying out recording on a hologram recording medium on which data are recorded as interference fringes of reference light and signal light, comprising:

a spatial light intensity modulator configured to carry out spatial light intensity modulation in a unit of a pixel;
a spatial light phase modulator configured to carry out spatial light phase modulation in a unit of a pixel;
an optical system configured to introduce light emitted from a light source to the hologram recording medium through the spatial light intensity modulator and the spatial light phase modulator;
a convertor configured to convert an input data train formed from combinations of two different values into another data train formed from combinations of three or more different values;
and
an amplitude and phase controller configured to control a light intensity and phase of each of the pixels of the spatial light intensity modulator and the spatial light phase modulator in response to each of the values of the another data train obtained from the converter, wherein
the converter carries out a modulation process according to a method using both amplitude and phase data or a method using a plurality of phase data displaced from each other to convert the input data train into combinations of in-phase data and quadrature data, and
the amplitude and phase controller is configured to perform control so that the light intensity and the phase of each of the pixels of the spatial light intensity modulator and the spatial light phase modulator may be a predetermined light intensity and a predetermined phase which correspond to a combination of the in-phase data and quadrature data obtained by the convertor.

5 more elements

A recording and reproduction method for a recording and reproduction apparatus that carries out recording and reproduction on and from a hologram recording medium on which data are recorded as interference fringes of reference light and signal light and includes a spatial light intensity modulator that carries out spatial light intensity modulation in a unit of a pixel, a spatial light phase modulator that carries out spatial light phase modulation in a unit of a pixel, and an optical system that introduces light emitted from a light source to the hologram recording medium through the spatial light intensity modulator and the spatial light phase modulator, comprising:

a three-value modulation encoding step of converting an input data train formed from combinations of two different values into another data train formed from combinations of three different values by carrying out a modulation process according to a method using both amplitude and phase data or a method using a plurality of phase data displaced from each other to convert the input data train into combinations of in-phase data and quadrature data;
an amplitude and phase controlling step of
controlling, upon recording, the spatial light intensity modulator so that, where a reference light area for producing the reference light and a signal light area for producing the signal light are defined in advance by the spatial light intensity modulator and the spatial light phase modulator, the light intensity at least in the reference light area may have a predetermined pattern, and controlling, in the signal light area, the light intensity and the phase of each of the pixels of the spatial light intensity modulator and the spatial light phase modulator in response to each value of the data train obtained by the three-value modulation encoding step, wherein the light intensity and the phase of each of the pixels of the spatial light intensity modulator and the spatial light phase modulator is controlled to be a predetermined light intensity and a predetermined phase which correspond to a combination of the in-phase data and quadrature data obtained in the step of three-value modulation, and
controlling, upon reproduction, the spatial light intensity modulator so that, when a reproduction image according to the data recorded on the hologram recording medium is to be obtained by irradiation of the reference light, the light intensity in the reference light area may have a pattern same as the predetermined pattern used upon recording and an overall light intensity in the signal light area may be a predetermined light intensity higher than a maximum value of absolute values of the amplitude of the reproduction image, and controlling the spatial light phase modulator so that a phase difference of π/2 may be provided between a reference phase in the reference light area and the phase in the signal light area;
an image signal acquisition step of receiving the reproduction image according to the data recorded on the hologram recording medium and obtained in response to introduction of the reference light produced during the control in the reference light area upon reproduction by the amplitude and phase controlling step and coherent light of the predetermined light intensity produced during the control in the signal light area to the hologram recording medium by the optical system and the coherent light and obtaining an image signal based on a result of the reception of the reproduction image and the coherent light;
a square root calculation step of calculating a square root of each of values which form the image signal obtained by the image signal acquisition step;
a removal step of removing a component of the coherent light from the image signal based on the result of the square root calculation by the square root calculation step;
a pixel value acquisition step of acquiring the pixel values recorded on the hologram recording medium based on the image signal obtained by the removal step;
a data discrimination step of carrying out data discrimination regarding the pixel values obtained by the pixel value acquisition step to obtain a data train formed from combinations of the three different values;
and
a decoding step of decoding the data train obtained by the data discrimination step and formed from combinations of the three different values into another data train formed from combinations of two different values in accordance with a rule for modulation encoding by the three-value modulation encoding step.

8 more elements

a multi-value modulation encoding step of carrying out a modulation process according to a method using both amplitude and phase data or a method using a plurality of phase data displaced from each other to convert an input data train formed from combinations of two different values into combinations of in-phase data and quadrature data;
an amplitude and phase controlling step of
controlling, upon recording, the spatial light intensity modulator so that, where a reference light area for producing the reference light and a signal light area for producing the signal light are defined in advance by the spatial light intensity modulator and the spatial light phase modulator, the light intensity at least in the reference light area may have a predetermined pattern, and controlling, in the signal light area, so that the light intensity and the phase of each of the pixels of the spatial light intensity modulator and the spatial light phase modulator may be a predetermined light intensity and a predetermined phase corresponding to a combination of in-phase data and quadrature data obtained by the multi-value modulation encoding step, and
controlling, upon reproduction, the spatial light intensity modulator so that, when a reproduction image according to the data for one hologram page recorded on the hologram recording medium is to be obtained by irradiation of the reference light, the light intensity in the reference light area may have a pattern same as the predetermined pattern used upon recording and an overall light intensity in the signal light area may be, where a higher one of maximum values of absolute values of the amplitude on an in-phase axis and the amplitude on a quadrature axis of the recording signal determined from a combination of a light intensity and a phase to be modulated by the spatial light modulater and the spatial light phase modulator is represented by MAX, higher than twice MAX, and controlling the phase of each of the pixels of the spatial light phase modulator so that two different beams of coherent light having a light intensity obtained by the control of the light intensity in the signal light area and higher than twice MAX are produced separately at two different timings such that the phase difference thereof from the reproduction image is 0 and π/2;
an image signal acquisition step of receiving the reproduction image according to the data recorded on the hologram recording medium and obtained twice in response to introduction of the two beams of the coherent light and the reference light produced during the control for each one hologram page upon reproduction by the amplitude and phase controlling step to the hologram recording medium by the optical system and the coherent light and obtaining two different image signals based on a result of the reception of the reproduction image and the coherent light;
a square root calculation step of calculating a square root of each of values which form the two image signals obtained by the image signal acquisition step;
a multi-value demodulation step of carrying out a mathematic operation using square root calculation results of the two different image signals obtained by the square root calculation step and the values of the light intensity of the coherent light to calculate a combination of the in-phase data and quadrature data recorded on each of the pixels in the hologram page;
and
a decoding step of decoding the data formed from the combinations of the in-phase data and quadrature data obtained as calculation results of the multi-value demodulation step into data formed from combinations of the two different values in accordance with a rule for modulation encoding by the multi-value modulation encoding step.

6 more elements

A reproduction method for a reproduction apparatus which that carries out reproduction from a hologram recording medium on which information of light intensity and phase based on combinations of in-phase data and quadrature data obtained by a modulation process according to a method using both amplitude and phase data or a method using a plurality of phase data displaced from each other is recorded as interference fringes of reference light and signal light and includes a spatial light intensity modulator that carries out spatial light intensity modulation in a unit of a pixel, a spatial light phase modulator that carries out spatial light phase modulation in a unit of a pixel, and an optical system for introducing light emitted from a light source to the hologram recording medium through the spatial light intensity modulator and the spatial light phase modulator, comprising:

an amplitude and phase controlling step of
controlling the light intensity of each of the pixels of the spatial light intensity modulator so that, when a reproduction image according to the data for one hologram page recorded on the hologram recording medium is to be obtained by irradiation of the reference light, the light intensity in a reference light area for producing the reference light may have a predetermined pattern same as that used upon recording and an overall light intensity in a signal light area for producing the signal light may be, where a higher one of maximum values of absolute values of the amplitude on an in-phase axis and the amplitude on a quadrature axis of a signal recorded on the hologram recording medium is represented by MAX, higher than twice MAX, and
controlling the phase of each of the pixels of the spatial light phase modulator so that two different beams of coherent light having a light intensity obtained by the control of the light intensity in the signal light area and higher than twice MAX are produced separately at two different timings such that the phase difference thereof from the reproduction image is 0 and π/2;
an image signal acquisition step of receiving the reproduction image according to the data recorded on the hologram recording medium and obtained twice in response to introduction of the two beams of the coherent light and the reference light produced during the control for each one hologram page upon reproduction by the amplitude and phase controlling step to the hologram recording medium by the optical system and the coherent light and obtaining two different image signals based on a result of the reception of the reproduction image and the coherent light;
a square root calculation step of calculating a square root of each of values which form the two image signals obtained by the image signal acquisition step;
a multi-value demodulation step of carrying out a mathematic operation using square root calculation results of the two different image signals obtained by the square root calculation step and the values of the light intensity of the coherent light to calculate a combination of the in-phase data and quadrature data recorded on each of the pixels in the hologram page;
and
a decoding step of decoding the data formed from the combinations of the in-phase data and quadrature data obtained as calculation results of the multi-value demodulation step into data formed from combinations of the two different values in accordance with a rule for modulation encoding determined in advance.

5 more elements

Dependencies are inferred from the claim text.

Recording device, recording/reproducing method, and reproducing method

Life of this patent

Recording device, recording/reproducing method, and reproducing method

Life of this patent

Abstract

Claims15