JP2008016101A - Information reproducing method and holography device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an information reproducing method capable of suppressing reproduction errors caused by uneven luminance without excessively increasing an arithmetic operation amount, and a holography device. <P>SOLUTION: A control unit calculates average intensity Bave[n] representing received light intensity of [0] data for each reference pattern, and average intensity Wave[n] representing received light intensity of [1] data. The control unit calculates an intensity difference D[n] for each reference pattern (step S110), and extracts a reference pattern having a largest intensity difference (step S112). An intermediate value between the extracted average intensities Wave and Bave is set to standard threshold intensity Ths (step S114). The control unit adjusts the light receiving sensitivity of an imaging part for a small area so that the intermediate value Mave matches the standard threshold intensity Ths (step S122). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an information reproducing method and a holographic device, and more particularly to a technique for suppressing the influence of luminance unevenness generated in reproduced light from a hologram recording medium.

  In recent years, a holographic recording method for recording / reproducing information using holography has been used in many fields. In such a hologram recording method, when writing information to the hologram recording medium, signal light that has been subjected to spatial light modulation (amplitude modulation, phase modulation, etc.) according to the information to be recorded is applied to the hologram recording medium together with the reference light. The Then, interference fringes generated by interference between the signal light and the reference light are recorded on the hologram recording medium. Here, since the signal light is modulated by an optical modulator having a spatial spread, the signal light includes image information including a plurality of data (data patterns) arranged two-dimensionally.

  On the other hand, at the time of reading information from the hologram recording medium, the same reference light as that at the time of writing information is applied to the hologram recording medium. Then, in the hologram recording medium, a part of the reference light is diffracted by the recorded interference fringes, and reproduction light having image information similar to the signal light is generated. Then, the reproduction light is guided to the imaging unit via the optical system and is received by the imaging unit. Thereafter, binarization processing is performed based on the received light intensity of the image information received by the imaging unit, and the information is reproduced.

  By the way, in the image information received by the imaging unit, non-uniform luminance (so-called luminance unevenness) due to crosstalk noise caused by multiplexed recording, an optical system, or the like may occur. Due to such luminance unevenness, the received light intensity of the image information becomes non-uniform. Therefore, if the binarization process is performed using the same threshold value, there is a possibility that the information is erroneously reproduced. Therefore, it is necessary to suppress such a reproduction error due to luminance unevenness.

  Therefore, for example, in Japanese Patent Application Laid-Open No. 11-272151 (Patent Document 1), as a second embodiment, a reference that bears at least the first and second digit levels to be read and determined at the time of reproduction at a predetermined position of each data block as a second embodiment A digital signal reproduction method is disclosed in which a threshold value is determined based on the value of a read signal corresponding to the reference bit for each block while bit data is arranged.

Furthermore, in Japanese Patent Application Laid-Open No. 11-272151 (Patent Document 1), as a first embodiment, a data block is recorded on a recording medium by including a plurality of bit data bearing all the digit levels to be read and judged during reproduction. On the other hand, a digital signal reproduction method is disclosed in which a threshold value is determined for each block based on the value of a read signal corresponding to bit data bearing all digit levels to be read.
Japanese Patent Laid-Open No. 11-272151

  However, in the second embodiment of Japanese Patent Application Laid-Open No. 11-272151 (Patent Document 1), the reference bit data carrying the first and second digit levels is only allocated one bit per block. For this reason, when a specific noise is superimposed on the reference bit data or when an image sensor that receives the reference bit data has a defect, a correct threshold value cannot be determined. There was a problem that playback errors could not be suppressed.

  In the first embodiment of Japanese Patent Application Laid-Open No. 11-272151 (Patent Document 1), a “1” / “0” determination is made once by comparing with a provisional slice level arbitrarily determined for each block. The data carrying “or“ 0 ”is obtained. Then, a new slice level that minimizes the reading error of the read data is newly set from the average value of the read data corresponding to the determination data “1” and the average value of the read data corresponding to the determination data “0”. And “1” / “0” determination is performed again. Thus, since at least two “1” / “0” determinations are required for each block, there is a problem in that the amount of calculation processing increases as the amount of information included in the image information increases. As a result, there is a problem in that the time required for one reading increases and high-speed information reading is obstructed.

  Accordingly, the present invention has been made to solve such a problem, and an object of the present invention is to provide an information reproduction method and a holography device capable of suppressing a reproduction error due to luminance unevenness without excessively increasing the amount of calculation processing. Is to provide.

  According to the first invention, there is provided an information reproducing method for reproducing information recorded on a hologram recording medium. An information reproduction method according to the present invention includes a step of irradiating a hologram recording medium with a reference light from a light source, a step of receiving image information of reproduction light generated from the hologram recording medium by irradiation of the reference light with an imaging unit, And reproducing information based on the received light intensity. In the hologram recording medium, information is recorded so that the image information includes a plurality of known reference patterns, and the imaging unit receives light sensitivity of the image information in units of small areas each including the reference pattern. Is configured to be changeable. Furthermore, the information reproducing method according to the present invention includes a step of adjusting the light receiving sensitivity for the small area based on the light receiving intensity of the reference pattern in each of the small areas.

  According to the information reproducing method according to the first aspect of the present invention, the light reception sensitivity in the imaging unit is adjusted in units of each small region based on the light reception intensity of the reference pattern that forms a part of the small region. In this way, the threshold value after receiving the image information is not optimized, but the received light intensity of the image information itself is optimized, so that reproduction errors can be reliably suppressed. Further, it is not necessary to frequently adjust the light receiving sensitivity after the light receiving sensitivity is adjusted once, so that the calculation processing amount does not increase excessively.

  Preferably, the reference information includes first data and second data associated with different received light intensity values.

  More preferably, the information reproducing method further includes a step of calculating a first representative intensity representative of the light reception intensity of the first data and a second representative intensity representative of the light reception intensity of the second data, The step of adjusting the sensitivity adjusts the light receiving sensitivity so that an intermediate value between the first representative intensity and the second representative intensity matches a predetermined threshold intensity in each of the small regions.

  More preferably, each of the first representative intensities is an average value of the received light intensities of all the first data included in the corresponding small area, and each of the second representative intensities is in the corresponding small area. It is the average value about the light reception intensity | strength of all the 2nd data contained.

  Preferably, the step of adjusting the light receiving sensitivity is executed only when at least one of the first representative intensity and the second representative intensity is outside a predetermined reference range.

  Preferably, the imaging unit includes a photoelectric conversion element that converts light energy into an electric signal, and the light receiving sensitivity is increased by adjusting at least one of the amount of light energy used for conversion of the electric signal and the amount of amplification of the electric signal. Be changed.

  Preferably, the imaging unit includes a CMOS image sensor, and the light receiving sensitivity is changed by adjusting at least one of an exposure time and an amplification gain of the CMOS image sensor.

Preferably, each of the reference patterns is arranged at the center of the corresponding small region.
Preferably, at least one of the plurality of reference patterns is used for specifying at which position of the imaging unit the image information is projected.

  According to the second invention, the holography device is capable of reproducing the information recorded on the hologram recording medium. A holography device according to the present invention includes a light source configured to irradiate a hologram recording medium with reference light, an imaging unit for receiving image information of reproduction light generated from the hologram recording medium by irradiation of the reference light, and image information And a control unit for reproducing information based on the received light intensity. In the hologram recording medium, information is recorded so that a plurality of reference patterns are included in the image information, and the imaging unit is a small area unit that includes a reference pattern in response to a command from the control unit. Thus, the light receiving sensitivity of the image information can be changed. Furthermore, the control unit adjusts the light receiving sensitivity for the small area based on the light reception intensity of the reference pattern in each of the small areas.

  According to the holography device of the second invention, the light receiving sensitivity in the imaging unit is adjusted in units of each small region based on the light reception intensity of the reference pattern that forms a part of the small region. In this way, the threshold value after receiving the image information is not optimized, but the received light intensity of the image information itself is optimized, so that reproduction errors can be reliably suppressed. Further, it is not necessary to frequently adjust the light receiving sensitivity after the light receiving sensitivity is adjusted once, so that the calculation processing amount does not increase excessively.

  Preferably, the reference information includes first data and second data associated with different received light intensity values.

  More preferably, the control unit calculates a first representative intensity representative of the light reception intensity of the first data and a second representative intensity representative of the light reception intensity of the second data, and further, each of the small regions The light receiving sensitivity is adjusted so that the intermediate value between the first representative intensity and the second representative intensity coincides with a predetermined threshold intensity.

  More preferably, each of the first representative intensities is an average value of the received light intensities of all the first data included in the corresponding small area, and each of the second representative intensities is in the corresponding small area. It is the average value about the light reception intensity | strength of all the 2nd data contained.

  More preferably, the control unit adjusts the light receiving sensitivity only when at least one of the first representative intensity and the second representative intensity is outside a predetermined reference range.

  Preferably, the imaging unit includes a photoelectric conversion element that converts light energy into an electric signal, and the light receiving sensitivity is increased by adjusting at least one of the amount of light energy used for conversion of the electric signal and the amount of amplification of the electric signal. Be changed.

  Preferably, the imaging unit includes a CMOS image sensor, and the light receiving sensitivity is changed by adjusting at least one of an exposure time and an amplification gain of the CMOS image sensor.

Preferably, each of the reference patterns is arranged at the center of the corresponding small region.
Preferably, at least one of the plurality of reference patterns is used for specifying at which position of the imaging unit the image information is projected.

  Preferably, the holography device according to the present invention modulates a part of the light emitted from the light source to generate a signal light for irradiating the hologram recording medium, and to input information. And an encoder for controlling the generation of signal light by the light modulator, and the encoder controls the light modulator so that a plurality of reference information is recorded in addition to the input information. .

  According to the present invention, it is possible to realize an information reproducing method and a holography device that can surely suppress a reproduction error due to luminance unevenness without excessively increasing an arithmetic processing amount.

  Embodiments of the present invention will be described in detail with reference to the drawings. Note that the same or corresponding parts in the drawings are denoted by the same reference numerals and description thereof will not be repeated.

FIG. 1 is a schematic configuration diagram of a holography device 100 according to an embodiment of the present invention.
Referring to FIG. 1, holography device 100 according to the embodiment of the present invention can record information on hologram recording medium 200 and can reproduce information recorded on hologram recording medium 200. The hologram recording medium 200 is configured as a rotating disk type or a card type as an example. The holography device 100 includes a control unit 2, an encoder unit 4, an optical modulator 6, a light source 8, an optical branching unit 10, an imaging unit 12, and a decoder unit 18.

  The control unit 2 selectively executes information recording on the hologram recording medium 200 and information reproduction from the hologram recording medium 200 in response to an external recording / reproduction command R / W. That is, when receiving an information recording command to the hologram recording medium 200, the control unit 2 performs control so that input data Din input from the outside is written to the hologram recording medium 200. On the other hand, when receiving the information reproduction command from the hologram recording medium 200, the control unit 2 controls the information recorded on the hologram recording medium 200 to be output to the outside as the output data Dout.

  The control unit 2 includes a memory 2a, and stores temporary data related to arithmetic processing in the memory 2a.

  The encoder unit 4 encodes the input data Din at the time of recording information on the hologram recording medium 200, and generates a data pattern (hereinafter also referred to as “image information”) in which a plurality of data are arranged two-dimensionally. . Although the level value of each data assigned to the image information can be arbitrarily set, in this embodiment, binary data (for example, “0” data and “1” data) is used as an example.

  The optical modulator 6 divides the reference light from the light source 8 into two when information is recorded on the hologram recording medium 200. Then, the optical modulator 6 performs spatial light modulation on the one split light according to the image information received from the encoder unit 4 to generate signal light. As the spatial light modulation, amplitude modulation, phase modulation, or a combination of both can be used. In this embodiment, amplitude modulation is employed. That is, the signal light emitted from the light modulator 6 has a two-dimensional intensity (shading) pattern corresponding to the image information. In the following description, a case where an amplitude modulation method in which “0” data is assigned to “black” (lowest gradation value) and “1” data is assigned to “white” (maximum gradation value) will be exemplified.

  Further, the light modulator 6 performs non-modulation (intensity distribution is uniform) or light modulation of a predetermined pattern on the other divided light to generate reference light.

  The optical modulator 6 generates reference light similar to that used when recording information on the hologram recording medium 200 during information reproduction from the hologram recording medium 200, but does not generate signal light.

  As a configuration in which the light modulator 6 divides the reference light from the light source into two, a movable mask or an optical shutter may be used.

  The light source 8 irradiates spatially and temporally coherent light so that stable optical interference occurs in the hologram recording medium 200. As an example, the light source 8 includes a semiconductor laser.

  The optical branching unit 10 transmits the signal light and the reference light emitted from the optical modulator 6 and guides them to the hologram recording medium 200, and reflects the reproduction light generated from the hologram recording medium 200 to guide it to the imaging unit 12.

  When reproducing information from the hologram recording medium 200, the imaging unit 12 receives image information of reproduction light generated from the hologram recording medium 200 by irradiation of reference light, and receives a digital signal corresponding to the received light intensity of the image information at the decoder unit 18. Output to. Specifically, the imaging unit 12 includes an image cell array 14 that receives image information of reproduction light, and a peripheral circuit 16 that generates a digital signal indicating the received light intensity of the image information received by the image cell array 14.

  The decoder unit 18 reproduces the information recorded on the hologram recording medium 200 based on the digital signal indicating the received light intensity of the image information received from the imaging unit 12.

(Information recording on the hologram recording medium 200)
FIG. 2 is a more detailed configuration diagram relating to information recording on the hologram recording medium 200.

  With reference to FIG. 2, the holography device 100 further includes a collimating lens 30, a quarter-wave plate 32, and an objective lens 34.

  The collimating lens 30 is disposed between the light source 8 and the light modulator 6, converts the reference light 40 (laser light) emitted from the light source 8 into parallel light, and guides it to the light modulator 6. The quarter-wave plate 32 is disposed between the light branching unit 10 and the hologram recording medium 200, and converts the polarization direction of transmitted light from linearly polarized light to circularly polarized light. The objective lens 34 converges the light transmitted through the quarter wavelength plate 32 onto the holography device 100 and guides the light generated from the holography device 100 to the quarter wavelength plate 32.

  When receiving an information recording command to the hologram recording medium 200, the encoder unit 4 encodes input data Din input from the outside to generate image information.

FIG. 3 is a diagram illustrating an example of image information generated by the encoder unit 4.
FIG. 4 is a diagram showing the data arrangement of the small area shown in FIG. 3 in more detail.

  Referring to FIG. 3, the image information is composed of a plurality of small areas (blocks). Each subregion includes one reference pattern. As will be described later, the reference pattern is a data pattern used for adjusting the light receiving sensitivity of the imaging unit 12 for a corresponding small region during information reproduction.

  Referring to FIG. 4, the reference pattern is arranged at the center of the corresponding small area. In the present embodiment, as an example, four “0” data (“black” region) arranged in 2 bits × 2 bits and ten “1” data (“white”) arranged on the outer periphery thereof. A 4-bit × 4-bit square data pattern is used. In addition, data bits obtained by encoding the input data Din are arranged in an area other than the reference pattern in the small area.

  3 and 4 exemplify a configuration in which both the small region and the reference pattern are formed in a square shape, but the configuration is not limited to a square shape, and may be any shape such as a rectangle, a ring, a cross, and the like. The shape can be selected. Further, the position where the reference pattern is arranged is not limited to the central portion of the image information, and can be arranged at an arbitrary position.

  Referring to FIG. 2 again, the optical modulator 6 generates a signal light 42 by spatially modulating a part of the reference light 40 according to the image information received from the encoder unit 4. Therefore, a two-dimensional intensity pattern as shown in FIG. 3 appears on the irradiation surface of the signal light 42. The light modulator 6 emits a part of the reference light 40 as the reference light 44 as it is.

  The signal light 42 and the reference light 44 emitted from the encoder unit 4 pass through the optical branching unit 10 and enter the quarter wavelength plate 32. The signal light 42 and the reference light 44 are converted from linearly polarized light into circularly polarized light by the quarter wavelength plate 32, respectively. The signal light 42 and the reference light 44 converted into circularly polarized light are converged at an arbitrary position of the hologram recording medium 200 by the objective lens 34.

  Since both the signal light 42 and the reference light 44 are generated from the coherent reference light 40, the signal light 42 and the reference light 44 cause optical interference in the hologram recording medium 200. Therefore, interference fringes generated by interference between the signal light 42 and the reference light 44 appear in the hologram recording medium 200.

  On the other hand, the hologram recording medium 200 is configured by bonding a recording layer 202 and a reflective film 204, and interference fringes generated by interference between the signal light 42 and the reference light 44 are recorded on the recording layer 202.

(Information reproduction from hologram recording medium 200)
FIG. 5 is a more detailed configuration diagram relating to information reproduction from the hologram recording medium 200.

  Referring to FIG. 5, when receiving an information reproduction command from hologram recording medium 200, encoder unit 4 generates only reference light 44 without generating signal light 42.

  The reference light 44 emitted from the encoder unit 4 passes through the optical branching unit 10 and enters the quarter wavelength plate 32. The reference light 44 is converted from linearly polarized light into circularly polarized light by the quarter wavelength plate 32. The reference light 44 converted into circularly polarized light is converged at an arbitrary position of the hologram recording medium 200 by the objective lens 34. Then, the reference light 44 is diffracted by the interference fringes recorded on the recording layer 202 of the hologram recording medium 200 and then reflected by the reflective film 204 to become the reproduction light 46. In the hologram recording medium 200, since the interference fringes recorded on the recording layer 202, that is, diffraction according to the recorded image information occurs, the reproduction light 46 has the same intensity pattern as the recorded image information.

  Then, the reproduction light 46 is converted into parallel rays by the objective lens 34 and then enters the quarter-wave plate 32. The reproduction light 46 is converted from circularly polarized light to linearly polarized light by the quarter wavelength plate 32. The reproduction light 46 converted into linearly polarized light is reflected by the light branching unit 10 and guided to the imaging unit 12.

  The imaging unit 12 receives the image information of the reproduction light 46 and outputs a digital signal corresponding to the received light intensity of the image information to the decoder unit 18. In the following description, the image information of the reproduction light 46 received by the imaging unit 12 is also referred to as “reproduction image information”.

  That is, the imaging unit 12 receives a two-dimensional intensity (shading) pattern generated by the projection of the reproduction light 46, acquires the intensity value (shading value) of each bit, and outputs it to the decoder unit 18. For example, if the number of gradations of the imaging unit 12 is 256, the imaging unit 12 determines which value is 0 to 255 gradations for the light reception intensity of each bit.

  Then, the decoder unit 18 reproduces information recorded on the hologram recording medium 200 based on the received light intensity received from the imaging unit 12, and outputs the information as output data Dout to the outside. Specifically, the decoder unit 18 determines whether the received light intensity of each bit is “0” data or “1” data by comparing with a predetermined threshold intensity.

  Here, as will be described later, the imaging unit 12 is configured to be able to change the light receiving sensitivity in units of small areas. Then, in order to avoid a reproduction error due to luminance unevenness that occurs in the reproduction image information of the reproduction light 46, the control unit 2 captures the corresponding small region based on the received light intensity of each reference pattern included in the reproduction image information. 12 is adjusted. That is, the control unit 2 optimizes the light reception sensitivity of the imaging unit 12 in units of small areas, thereby uniformizing the light reception intensity of the entire received reproduction image information and suppressing a reproduction error due to luminance unevenness.

(Configuration of the imaging unit 12)
With reference to FIG. 1 again, the detailed configuration and operation of the imaging unit 12 will be described in detail.

  The image cell array 14 of the imaging unit 12 includes, for example, a complementary metal oxide silicon (CMOS) image sensor, and is arranged in association with each of a plurality of bit lines BL and a plurality of word lines WL arranged in a matrix. A plurality of photocells PC are included. Each of the photocells PC corresponds to a pixel of the imaging unit 12 and detects and outputs the received light intensity of incident light.

  The imaging unit 12 must be able to independently detect the light reception intensity of each data (bit) of the reproduction image information, so that each photocell PC is configured in association with the data arrangement of the reproduction image information. The physical size is configured to be equal to or smaller than the area allocated to one data in the reproduction image information.

  Each of the photocells PC includes a photodiode PD that is a photoelectric conversion element that converts received light energy into an electrical signal. Each of the photocells PC is connected between the corresponding photodiode PD and the corresponding bit line BL, and the corresponding photodiode PD is connected to the corresponding bit according to the activation / inactivation of the corresponding word line WL. An access transistor ATR that electrically connects / disconnects with the line BL is included.

  The peripheral circuit 16 receives the row address RA, the column address CA, and the control command CTRL from the control unit 2 and acquires the received light intensity from the photocell PC to be read from the image cell array 14. The peripheral circuit 16 includes a word line driver WD, a bit line driver BD, a transfer gate TG, an amplification amplifier 20, and an analog-to-digital converter (ADC) 22.

  Each of the word line drivers WD is electrically connected to the corresponding word line WL, and activates (high voltage state) or deactivates (low voltage state) the corresponding word line WL according to the row address RA. .

  Each transfer gate TG is connected between a corresponding bit line BL and an output data line DL, and each gate is connected to a corresponding bit line driver BD. The bit line driver BD activates (high voltage state) or deactivates (low voltage state) the corresponding transfer gate TG according to the column address CA. Therefore, the transfer gate TG activated by the bit line driver BD electrically connects the corresponding bit line BL and the output data line DL.

  That is, the electrical signal from the photocell PC located at the intersection of the word line WL activated by the word line driver WD and the bit line BL corresponding to the transfer gate TG activated by the bit line driver BD is output data. The signal is output to the amplification amplifier 20 via the line DL. Therefore, random access to the image cell array 14 is possible.

  The amplification amplifier 20 is connected to the output data line DL, amplifies the electric signal received from the target photocell PC with a predetermined amplification gain, and then outputs the amplified signal to the analog-digital converter 22.

  The analog-digital converter 22 converts the amplified electric signal (analog signal) output from the amplifier 20 into a digit value (for example, 0 to 255 gradations) according to the amplitude value.

(Reception sensitivity of the imaging unit 12)
The light receiving sensitivity in the imaging unit 12 is changed by adjusting at least one of the amount of light energy used for conversion of the electrical signal in the photodiode PD and the amplification amount of the electrical signal output from the photodiode PD. That is, the light receiving sensitivity in the imaging unit 12 is changed by adjusting at least one of the exposure time of the photocell PC and the amplification gain in the amplification amplifier 20.

  The exposure time of the photocell PC is determined by the activation / inactivation timing of the corresponding word line WL. Specifically, the photocell PC can switch between output of an electric signal (charge) and generation of an electric signal (accumulation of electric charge) according to activation / deactivation of the corresponding word line WL. Therefore, the exposure time of the corresponding photocell PC can be adjusted by adjusting the inactive period of the word line WL. That is, as the inactive period of the word line WL is lengthened, the charge accumulation amount by the photodiode PD is increased and the light receiving sensitivity is increased. On the other hand, as the inactive period of the word line WL is shortened, the charge accumulation by the photodiode PD is increased. The amount decreases and the light receiving sensitivity decreases.

  In addition, the amplification amplifier 20 amplifies the electric signal output from the photocell PC specified by the word line WL and the bit line BL with a predetermined amplification gain. Therefore, the light reception in the imaging unit 12 is adjusted by adjusting the amplification gain. Sensitivity can be changed. That is, by adjusting the amplification gain in synchronization with the activation / deactivation timing of the word line WL and the bit line BL, the light receiving sensitivity can be changed in units of photocells PC.

  As described above, since the imaging unit 12 can change the light receiving sensitivity in units of photocells PC, it is naturally possible to change the light receiving sensitivity in units of small areas including a plurality of photocells PC. That is, the control unit 2 outputs a control command CTRL for changing the light receiving sensitivity to the imaging unit 12 in units of a plurality of photocells PC corresponding to each small area of the reproduction image information.

(Processing related to information reproduction)
The control unit 2 reproduces information from the hologram recording medium 200 while adjusting the light reception sensitivity in the imaging unit 12 for the corresponding small region based on the light reception intensity of the reference pattern according to the following processing flow. In the following processing flow, a case where n reference patterns are included in one image information is illustrated.

FIG. 6 is a flowchart showing a process related to information reproduction according to the embodiment of the present invention.
Referring to FIG. 6, control unit 2 sets the light receiving sensitivity of each photocell PC in image cell array 14 to an initial value (step S100). That is, the control unit 2 gives a control command CTRL to the imaging unit 12 so as to set the activation / inactivation timing of the word line WL and the amplification gain in the amplification amplifier 20 to predetermined initial values.

  The control unit 2 receives the reproduction image information generated from the hologram recording medium 200 by the irradiation of the reference light 44 by the imaging unit 12 (step S102). That is, the control unit 2 gives a control command for irradiating the reference light 44 to the hologram recording medium 200 to the encoder unit 4 and also outputs a control command for reading the received light intensity of the reproduction image information from the imaging unit 12 to the decoder unit. Give to 18.

  Then, the control unit 2 acquires the light reception intensity B [n: i] of “0” data and the light reception intensity W [n: j] of “1” data from the decoder unit 18 for each reference pattern of the reproduction image information. (Step S104). In the received light intensity B [n: i] and the received light intensity W [n: j], the subscript “n” indicates the corresponding reference pattern, and the subscript “i” is “0” data included in each reference pattern. The subscript “j” indicates the total number of “1” data included in each reference pattern.

  Further, for each reference pattern, the control unit 2 calculates a representative intensity of “0” data representing the received light intensity of “0” data and a representative intensity of “1” data representing the received light intensity of “1” data. (Step S106). As an example, for each reference pattern, the control unit 2 averages the average intensity Bave [n] obtained by averaging all of the received light intensity B [n: i] and the average intensity Wave obtained by averaging all the received light intensity W [n: i]. [N] is calculated.

  The control unit 2 determines whether each of the calculated average intensity Bave [n] and average intensity Wave [n] is within the respective reference ranges (step S108). That is, the control unit 2 determines whether luminance unevenness has occurred in the reproduction image information. The reference range may be derived experimentally in advance, but may be determined based on the light reception intensity after the previous light reception adjustment.

  When each of the calculated average intensity Bave [n] and average intensity Wave [n] does not exist within the reference range (NO in step S108), the control unit 2 determines that the average intensity Wave [n] An intensity difference D [n] (= average intensity Wave [n] −average intensity Bave [n]) for each reference pattern is calculated from the difference with the average intensity Bave [n] (step S110).

  Then, the control unit 2 extracts a reference pattern having the maximum intensity difference from the calculated intensity differences D [n] for each reference pattern (step S112). That is, the control unit 2 specifies the reference pattern that maximizes the threshold strength margin. Further, the control unit 2 sets the threshold intensity in the extracted reference pattern, that is, an intermediate value between the average intensity Wave and the average intensity Bave (= {average intensity Wave + average intensity Bave} / 2) as the standard threshold intensity Ths. (Step S114).

Subsequently, the control unit 2 executes light receiving sensitivity adjustment processing for each of the small regions.
The control unit 2 selects the first small area of the reproduction image information (step S116). Then, the control unit 2 calculates an intermediate value Mave (= {average intensity Wave + average intensity Bave} / 2) between the average intensity Wave and the average intensity Bave in the selected small region (step S118). Then, the control unit 2 determines whether or not the intermediate value Mave substantially matches the standard threshold strength Ths (step S120). When the intermediate value between the average intensity Wave and the average intensity Bave does not substantially match the standard threshold intensity Ths (NO in step S120), the control unit 2 matches the intermediate value Mave with the standard threshold intensity Ths. As described above, the light receiving sensitivity of the imaging unit 12 for the small region is adjusted (step S122). As an example, the control unit 2 changes at least one of the exposure time of the photocell PC and the amplification gain in the amplification amplifier 20 by an adjustment amount corresponding to the deviation between the standard threshold strength Ths and the intermediate value Mave.

  After the light receiving sensitivity is changed, the control unit 2 gives a control command for irradiating the hologram recording medium 200 with the reference light 44 to the encoder unit 4, and the light receiving intensity B [i] for the reference pattern of the selected small region. Then, the received light intensity W [j] is acquired (step S124). Then, the control unit 2 uses the acquired received light intensity B [i] and received light intensity W [j] to obtain an intermediate value Mave (= {average intensity Wave + average intensity) between the average intensity Wave and the average intensity Bave in the selected small region. Bave} / 2) is calculated (step S118). Furthermore, the control unit 2 determines whether or not the intermediate value Mave substantially matches the standard threshold strength Ths (step S120).

  When intermediate value Mave substantially matches standard threshold strength Ths (YES in step S120), control unit 2 determines whether all small regions of the reproduction image information have been selected (step S126). ). If all the small areas in the reproduction image information have not been selected (NO in step S126), the control unit 2 selects the next small area of the reproduction image information (step S128), and steps S118 and thereafter. Execute the process again.

  When all the small areas in the reproduction image information are selected (YES in step S126), the control unit 2 causes the imaging unit 12 to reproduce the reproduction image information generated from the hologram recording medium 200 by the irradiation of the reference light 44. Light is received (step S130). That is, the control unit 2 gives a control command for irradiating the reference light 44 to the hologram recording medium 200 to the encoder unit 4, and outputs a control command for reading the received light intensity of the reproduction image information from the imaging unit 12. Give to 18.

  After the reproduction image information generated from the hologram recording medium 200 by the irradiation of the reference light 44 is received by the imaging unit 12 (after execution of step S130), or each of the calculated average intensity Bave [n] and average intensity Wave [n] When it exists in each reference range (in the case of YES in step S108), the control unit 2 reproduces information based on the received light intensity of the reproduction image information and outputs it as output data Dout (step S132). That is, the control unit 2 gives a control command for reproducing information to the decoder unit 18 based on the received light intensity of the reproduction image information output from the imaging unit 12. In the binarization process in the decoder unit 18, the above-described standard threshold strength Ths is commonly used for any small region. This is a natural result of determining the light receiving sensitivity for the corresponding small region so that the threshold intensity of each reference pattern matches the standard threshold intensity Ths.

  Thereafter, the control unit 2 determines whether it is necessary to reproduce other information from the hologram recording medium 200 (step S134). When it is necessary to reproduce other information from hologram recording medium 200 (YES in step S134), control unit 2 executes the processing from step S102 onward again.

  When it is not necessary to reproduce other information from hologram recording medium 200 (NO in step S134), control unit 2 ends the process.

  In the above processing flow, the example in which the light reception sensitivity in the imaging unit 12 is changed by adjusting at least one of the exposure time of the photocell PC or the amplification gain in the amplification amplifier 20 has been described. The adjustment target may be appropriately selected according to the amount of change in sensitivity.

  According to the above-described processing flow, in the process of reproducing information from the hologram recording medium 200 for the first time, it is necessary to adjust the light receiving sensitivity for each small region of the reproduction image information. There is little need to adjust the sensitivity frequently. That is, the light receiving sensitivity for each small region determined in the first light receiving sensitivity changing process is adjusted so as to cancel out the inherent luminance unevenness caused by the photocell PC and the optical system of the imaging unit 12. Such luminance unevenness does not depend on the type and time of the hologram recording medium 200, and therefore once adjusted, there is little need to adjust again.

  According to the present embodiment, the light reception sensitivity in the imaging unit 12 is adjusted in units of each small region based on the light reception intensity of the reference pattern that forms a part of the small region. In this way, the threshold value after receiving the image information is not optimized, but the received light intensity of the received image information is optimized, so that reproduction errors can be reliably suppressed.

  Further, according to the present embodiment, the light receiving sensitivity in the image pickup unit 12 after adjustment includes a correction amount for canceling the inherent luminance unevenness caused by the photocell PC or the optical system of the image pickup unit 12. Yes. In such luminance unevenness, the temporal variation is small, so that the light reception sensitivity once adjusted does not need to be frequently adjusted. Therefore, the amount of calculation processing related to information reproduction from the hologram recording medium 200 does not increase excessively, and high-speed information reading can be realized.

  Further, according to the present embodiment, the reference pattern arranged in each small area is composed of a plurality of “0” data and “1” data, and is evaluated by an average value of received light intensity corresponding to each data. Therefore, even if a defect exists in any of the photocells PC of the imaging unit 12, the influence on the adjustment process of the received light intensity can be reduced. Therefore, it is possible to realize a holography device having a relatively high strength against the defect of the imaging unit 12.

  In addition, according to the present embodiment, since the reference pattern is arranged at the center of each small area, the luminance unevenness in each small area can be evaluated using the same index. Therefore, when there is irregular luminance with regularity (for example, when the central portion of the reproduced image information has high luminance and the peripheral portion has low luminance), the light receiving sensitivity should be adjusted. It can be realized more effectively.

(Modification)
In the above-described embodiment, the configuration in which a plurality of reference patterns are arranged in the image information only for the purpose of adjusting the light receiving sensitivity for each small area has been described. It can also be used as a function for matching.

  Since the holographic device according to the modification of the present embodiment is the same as that shown in FIGS. 1, 2, and 5, detailed description thereof will not be repeated.

FIG. 7 is a diagram showing an example of image information according to a modification of the present embodiment.
Referring to FIG. 7, the image information according to the modification of the present embodiment is composed of four small areas, and reference patterns are arranged at the four corners. In addition, the reference pattern in the modification of this Embodiment is the same as the reference pattern shown in FIG. 4 as an example.

  As described above, the reference patterns arranged at the four corners of the image information are used to specify at which position of the imaging unit 12 the reproduced image information is projected.

  As shown in FIGS. 2 and 5, the reproduction image information is generated by irradiating the hologram recording medium 200 with the reference light 44, and thus the projection position of the reproduction image information is likely to be shifted. However, in order to reproduce information in bit units from the reproduction image information, it is necessary to associate at least one photocell PC with each bit of the reproduction image information.

  Therefore, as one method of avoiding a reproduction error due to a shift in the projection position, the image pickup unit 12 having a light receiving area larger than the projection area of the reproduction image information is adopted, and only the area where the reproduction image information is projected is used. There is a method of setting an effective light receiving area. In such a method, it is necessary to specify the projection position of the reproduction image information, and an example of processing relating to the specification of the projection position and the determination of the effective light receiving area is referred to as alignment.

FIG. 8 is a diagram for explaining an example of alignment of reproduction image information.
FIG. 8A is a diagram illustrating a case where the reproduction image information matches the effective light receiving area of the imaging unit 12.

FIG. 8B is a diagram illustrating a case where a change occurs in the projection position of the reproduction image information.
Referring to FIG. 8A, when the reproduction image information is projected onto the light receiving area of the imaging unit 12, the decoder unit 18 (FIG. 1) is based on the reference patterns arranged at the four corners of the reproduction image information. The projection position of the reproduction image information is specified, and the specification information is output to the control unit 2 (FIG. 1).

  Then, based on the specific information received from the decoder unit 18, the control unit 2 outputs a control command CTRL to the imaging unit 12 so that the received light intensity is output for the region where the reproduction image information is projected. In this way, the control unit 2 determines an effective light receiving area.

  Referring to FIG. 8B, the decoder unit 18 periodically specifies the projection position of the reproduction image information and outputs the identification information to the control unit 2, so that the control unit 2 projects the reproduction image information. The positional deviation of the position can be detected. When the projection position of the reproduction image information is changed, the control unit 2 shifts the effective light receiving area to the optimum position according to the procedure described above. As described above, the control unit 2 maintains the effective light receiving region at the optimum position for any positional deviation of up / down / left / right and rotation based on the reference pattern of the reproduction image information.

  In addition, the configuration for changing the light receiving sensitivity of imaging unit 12 for a small region is the same as that in the present embodiment described above, and therefore detailed description will not be repeated.

  In the above description, the configuration in which the effective light receiving area of the imaging unit 12 is changed to correct the deviation in the projection position of the reproduction image information has been described. However, other optical correction configurations are possible. is there.

  Further, the reference pattern may have any position and shape as long as the projection position of the reproduction image information can be specified.

  According to the modification of the embodiment of the present invention, in addition to the effects in the above-described embodiment, the reference pattern is used for adjusting and aligning the light receiving sensitivity of the imaging unit 12, so that the reference pattern and the position are included in the information image. A larger amount of information can be recorded as compared with the case where the alignment pattern is arranged. Therefore, information can be efficiently written on the hologram recording medium 200.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a schematic configuration diagram of a holography device according to an embodiment of the present invention. It is a more detailed block diagram concerning information recording on a hologram recording medium. It is a figure which shows an example of the image information produced | generated by an encoder part. It is a figure which shows the data arrangement | positioning of the small area | region shown in FIG. 3 in detail. It is a more detailed block diagram concerning information reproduction from a hologram recording medium. It is a flowchart which shows the process which concerns on the information reproduction according to embodiment of this invention. It is a figure which shows an example of the image information according to the modification of this Embodiment. It is a figure for demonstrating an example of position alignment of reproduction | regeneration image information.

Explanation of symbols

  2 control unit, 2a memory, 4 encoder unit, 6 optical modulator, 8 light source, 10 optical branching unit, 12 imaging unit, 14 image cell array, 16 peripheral circuit, 18 decoder unit, 20 amplification amplifier, 22 analog-digital converter, 30 collimating lens, 32 1/4 wavelength plate, 34 objective lens, 40 reference light, 42 signal light, 44 reference light, 46 reproduction light, 100 holography device, 200 hologram recording medium, 202 recording layer, 204 reflecting film, ATR access Transistor, B, W Light intensity, Bave, Wave Average intensity, BD bit line driver, BL bit line, CA column address, CTRL control command, D intensity difference, Din input data, DL output data line, Dout output data, Mave intermediate Value, PC photocell, PD file DOO diode, R / W recording / reproducing command, RA row address, TG transfer gate, Ths standard threshold intensity, WD word line driver, WL the word line.

Claims (19)

An information reproducing method for reproducing information recorded on a hologram recording medium,
Irradiating the hologram recording medium with a reference light from a light source;
Receiving image information of reproduction light generated from the hologram recording medium by irradiation of the reference light with an imaging unit;
Regenerating the information based on the received light intensity of the image information,
The hologram recording medium is recorded with information so that the image information includes a plurality of known reference patterns,
The imaging unit is configured to change the light receiving sensitivity of the image information in units of small areas each including the reference pattern,
The information reproduction method includes the step of adjusting the light reception sensitivity for the small area based on the light reception intensity of the reference pattern in each of the small areas.   The information reproduction method according to claim 1, wherein the reference information includes first data and second data associated with different received light intensity values. The information reproducing method further includes a step of calculating a first representative intensity representative of the received light intensity of the first data and a second representative intensity representative of the received light intensity of the second data,
The step of adjusting the light receiving sensitivity adjusts the light receiving sensitivity so that an intermediate value between the first representative intensity and the second representative intensity matches a predetermined threshold intensity in each of the small regions. The information reproducing method according to claim 2. Each of the first representative intensities is an average value of the received light intensity of all the first data included in the corresponding small region,
4. The information reproducing method according to claim 3, wherein each of the second representative intensities is an average value of the received light intensities of all the second data included in the corresponding small area.   5. The information according to claim 3, wherein the step of adjusting the light receiving sensitivity is executed only when at least one of the first representative intensity and the second representative intensity is outside a predetermined reference range. Playback method.   The imaging unit includes a photoelectric conversion element that converts light energy into an electric signal, and the light receiving sensitivity is changed by adjusting at least one of an amount of light energy used for conversion of the electric signal and an amplification amount of the electric signal. The information reproduction method according to any one of claims 1 to 5.   The information according to any one of claims 1 to 6, wherein the imaging unit includes a CMOS image sensor, and the light receiving sensitivity is changed by adjusting at least one of an exposure time and an amplification gain of the CMOS image sensor. Playback method.   The information reproduction method according to claim 1, wherein each of the reference patterns is arranged at a center portion of the corresponding small region.   The information reproduction according to any one of claims 1 to 8, wherein at least one of the plurality of reference patterns is used to specify at which position of the imaging unit the image information is projected. Method. A holography device capable of reproducing information recorded on a hologram recording medium,
A light source configured to irradiate the hologram recording medium with reference light;
An imaging unit for receiving image information of reproduction light generated from the hologram recording medium by irradiation of the reference light;
A decoder unit for reproducing the information based on the received light intensity of the image information;
A control unit,
The hologram recording medium is recorded with information so that the image information includes a plurality of reference patterns,
The imaging unit is configured to change the light receiving sensitivity of the image information in units of small regions each including the reference pattern in accordance with a command from the control unit,
The said control part is a holography apparatus which adjusts the said light reception sensitivity about the said small area based on the light reception intensity | strength of the said reference pattern in each of the said small area.   The holography device according to claim 10, wherein the reference information includes first data and second data associated with different received light intensity values.   The control unit calculates a first representative intensity representative of the received light intensity of the first data and a second representative intensity representative of the received light intensity of the second data, and further, each of the small regions The holographic device according to claim 11, wherein the light receiving sensitivity is adjusted so that an intermediate value between the first representative intensity and the second representative intensity matches a predetermined threshold intensity. Each of the first representative intensities is an average value of the received light intensity of all the first data included in the corresponding small region,
The holography device according to claim 12, wherein each of the second representative intensities is an average value of the received light intensities of all the second data included in the corresponding small region.   The holography according to claim 12 or 13, wherein the control unit adjusts the light receiving sensitivity only when at least one of the first representative intensity and the second representative intensity is outside a predetermined reference range. apparatus.   The imaging unit includes a photoelectric conversion element that converts light energy into an electric signal, and the light receiving sensitivity is changed by adjusting at least one of an amount of light energy used for conversion of the electric signal and an amplification amount of the electric signal. The holography device according to any one of claims 10 to 14.   The holography according to any one of claims 10 to 15, wherein the imaging unit includes a CMOS image sensor, and the light receiving sensitivity is changed by adjusting at least one of an exposure time and an amplification gain of the CMOS image sensor. apparatus.   17. The holography device according to claim 10, wherein each of the reference patterns is arranged at a center portion of the corresponding small region.   The holography device according to any one of claims 10 to 17, wherein at least one of the plurality of reference patterns is used to specify at which position of the imaging unit the image information is projected. . The holographic device comprises:
A light modulation unit capable of modulating a part of light emitted from the light source and generating signal light for irradiating the hologram recording medium;
An encoder unit for controlling generation of the signal light by the optical modulation unit according to input information;
The holography device according to claim 10, wherein the encoder unit controls the light modulation unit such that the plurality of reference information is recorded in addition to the input information.

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