Generation method for complex amplitude in-line hologram and image recording device using said method
A method for generating a complex amplitude in-line hologram and an image recording device using said method makes it possible to realize high-speed processing and high-speed recording from a single off-axis hologram without limiting the spatial frequency band and without creating errors from interpolation. The complex amplitude in-line hologram is generated by performing the following in order: the acquisition of data for one off-axis hologram obtained by way of off-axis holography, and for an off-axis reference light used for obtaining the hologram; the setting of a reconstruction in-line reference light; a modulation process for performing spatial heterodyne modulation on the hologram on the basis of the phases of the reference lights; and a filtering process for performing spatial frequency filtering on the hologram modulated by the modulation process. Because spatial sampling is not performed, the limits on the viewing angle are relaxed.
1. A generation method for generating a complex amplitude in-line hologram from an off-axis hologram, comprising the steps of:
performing spatial heterodyne modulation on an off-axis hologram obtained by off-axis holography, based on phase of an in-line reference light for reconstruction and phase of an off-axis reference light used for obtaining the off-axis hologram; and
performing spatial frequency filtering on the hologram modulated by the spatial heterodyne modulation, wherein
the method generates the complex amplitude in-line hologram by performing the spatial heterodyne modulation and the spatial frequency filtering in order.
2. A generation method for generating a complex amplitude in-line hologram according to claim 1 , characterized in that the method further comprises the steps of:
generating a basic hologram as a pretreatment process by subtracting a light intensity component of the off-axis reference light from the off-axis hologram before performing both the spatial frequency filtering and the spatial heterodyne modulation;
deriving a light intensity component of an object light as a generation-derivation process using a complex amplitude in-line hologram generated by performing the spatial heterodyne modulation and the spatial frequency filtering on the basic hologram generated in the pretreatment process;
generating a complex amplitude in-line hologram as an approximation process by performing the spatial heterodyne modulation and the spatial frequency filtering on an off-axis hologram obtained by subtracting the derived light intensity component of the object light from the basic hologram; and
calculating a light intensity component of the object light using the complex amplitude in-line hologram generated in the approximation process and judging whether or not the light intensity component is within a tolerance, as a calculation-judgment process, wherein
when the light intensity component of the object light is judged not to be within the tolerance in the calculation-judgment process, the method repeats the approximation process and the calculation-judgment process using the light intensity component of the object light in order to eliminate influence of the object light and generate a complex amplitude in-line hologram.
3. A generation method for generating a complex amplitude in-line hologram according to claim 2 , characterized in that the method further comprises the steps of:
obtaining the off-axis hologram electronically as an off-axis hologram obtaining process through a photo detector by off-axis holography; and
measuring intensity of the reference light on a light receiving surface of the photo detector before or after the off-axis hologram obtaining process, wherein
the off-axis hologram obtaining process is carried out in a condition that the intensity of the reference light on the light receiving surface being made larger than that of the object light on the light receiving surface.
4. A generation method for generating a complex amplitude in-line hologram according to claim 1 , characterized in that the method further comprises the steps of:
reconstructing an image from the off-axis hologram;
detecting a gap between optical axes of the object light and the reference light used for obtaining the off-axis hologram from the reconstructed image; and
setting an optical axis of the in-line reference light for reconstruction by using the gap, as an axis setting process.
5. A generation method for generating a complex amplitude in-line hologram from an off-axis hologram, comprising the steps of:
performing spatial frequency filtering on an off-axis hologram obtained by off-axis holography; and
performing spatial heterodyne modulation on the hologram filtered by the spatial frequency filtering, based on phase of an in-line reference light for reconstruction and phase of an off-axis reference light used for obtaining the off-axis hologram, wherein
the method generates the complex amplitude in-line hologram by performing the spatial frequency filtering and the spatial heterodyne modulation in order.
6. A generation method for generating a complex amplitude in-line hologram according to claim 5 , characterized in that the method further comprises the steps of:
generating a basic hologram as a pretreatment process by subtracting a light intensity component of the off-axis reference light from the off-axis hologram before performing both the spatial frequency filtering and the spatial heterodyne modulation;
deriving a light intensity component of an object light as a generation-derivation process using a complex amplitude in-line hologram generated by performing the spatial heterodyne modulation and the spatial frequency filtering on the basic hologram generated in the pretreatment process;
generating a complex amplitude in-line hologram as an approximation process by performing the spatial heterodyne modulation and the spatial frequency filtering on an off-axis hologram obtained by subtracting the derived light intensity component of the object light from the basic hologram; and
calculating a light intensity component of the object light using the complex amplitude in-line hologram generated in the approximation process and judging whether or not the light intensity component is within a tolerance, as a calculation-judgment process, wherein
when the light intensity component of the object light is judged not to be within the tolerance in the calculation-judgment process, the method repeats the approximation process and the calculation-judgment process using the light intensity component of the object light in order to eliminate influence of the object light and generate a complex amplitude in-line hologram.
7. A generation method for generating a complex amplitude in-line hologram according to claim 6 , characterized in that the method further comprises the steps of:
obtaining the off-axis hologram electronically as an off-axis hologram obtaining process through a photo detector by off-axis holography; and
measuring intensity of the reference light on a light receiving surface of the photo detector before or after the off-axis hologram obtaining process, wherein
the off-axis hologram obtaining process is carried out in a condition that the intensity of the reference light on the light receiving surface being made larger than that of the object light on the light receiving surface.
8. A generation method for generating a complex amplitude in-line hologram according to claim 7 , characterized in that the method further comprises the steps of:
reconstructing an image from the off-axis hologram;
detecting a gap between optical axes of the object light and the reference light used for obtaining the off-axis hologram from the reconstructed image; and
setting an optical axis of the in-line reference light for reconstruction by using the gap, as an axis setting process.
9. A generation method for generating a complex amplitude in-line hologram according to claim 6 , characterized in that the method further comprises the steps of:
reconstructing an image from the off-axis hologram;
detecting a gap between optical axes of the object light and the reference light used for obtaining the off-axis hologram from the reconstructed image; and
setting an optical axis of the in-line reference light for reconstruction by using the gap, as an axis setting process.
10. A generation method for generating a complex amplitude in-line hologram according to claim 5 , characterized in that the method further comprises the steps of:
reconstructing an image from the off-axis hologram;
detecting a gap between optical axes of the object light and the reference light used for obtaining the off-axis hologram from the reconstructed image; and
setting an optical axis of the in-line reference light for reconstruction by using the gap, as an axis setting process.
11. An image recording device for generating a complex amplitude in-line hologram from an off-axis hologram which records an object image so as to record the hologram electronically as object image information, comprising:
an off-axis hologram obtaining unit for recording the object image as the off-axis hologram by off-axis holography;
a hologram converter for generating the complex amplitude in-line hologram from the off-axis hologram obtained by the off-axis hologram obtaining unit; and
a storage unit for electronically recording the complex amplitude in-line hologram generated by the hologram converter as object image information, wherein
the hologram converter includes:
a modulation unit for performing spatial heterodyne modulation on the off-axis hologram, based on phase of an in-line reference light for reconstruction and phase of an off-axis reference light used for obtaining the off-axis hologram; and
a filtering unit for performing spatial frequency filtering on the hologram modulated by the modulation unit, and wherein
the image recording device generates the complex amplitude in-line hologram using the modulation unit and the filtering unit.
12. An image recording device according to claim 11 , wherein the off-axis hologram obtaining unit uses a pulsed laser as a light source of coherent light.
13. An image recording device according to claim 12 , wherein
the off-axis hologram obtaining unit records an object image as a color off-axis hologram using a plurality of lasers having different wavelength zone each other, and wherein
the hologram converter generates a color complex amplitude in-line hologram from the color off-axis hologram.
14. An image recording device according to claim 11 , wherein
the off-axis hologram obtaining unit records an object image as a color off-axis hologram using a plurality of lasers having different wavelength zone each other, and wherein
the hologram converter generates a color complex amplitude in-line hologram from the color off-axis hologram.
15. An image recording device for generating a complex amplitude in-line hologram from an off-axis hologram which records an object image so as to record the hologram electronically as object image information, comprising:
an off-axis hologram obtaining unit for recording the object image as the off-axis hologram by off-axis holography;
a hologram converter for generating the complex amplitude in-line hologram from the off-axis hologram obtained by the off-axis hologram obtaining unit; and
a storage unit for electronically recording the complex amplitude in-line hologram generated by the hologram converter as object image information, wherein
the hologram converter includes:
a filtering unit for performing spatial frequency filtering on the off-axis hologram; and
a modulation unit for performing spatial heterodyne modulation on the hologram filtered by the filtering unit, based on phase of an in-line reference light for reconstruction and phase of an off-axis reference light used for obtaining the off-axis hologram:
the image recording device generates the complex amplitude in-line hologram using the modulation unit and the filtering unit.
16. An image recording device according to claim 15 , wherein the off-axis hologram obtaining unit uses a pulsed laser as a light source of coherent light.
17. An image recording device according to claim 16 , wherein
the off-axis hologram obtaining unit records an object image as a color off-axis hologram using a plurality of lasers having different wavelength zone each other, and wherein
the hologram converter generates a color complex amplitude in-line hologram from the color off-axis hologram.
18. An image recording device according to claim 15 , wherein
the off-axis hologram obtaining unit records an object image as a color off-axis hologram using a plurality of lasers having different wavelength zone each other, and wherein
the hologram converter generates a color complex amplitude in-line hologram from the color off-axis hologram.