Patent Number: 
Section: claims

1. An imaging apparatus comprising:a detector device for determining points of incidence of photons and having an impact surface, andan aperture for projecting the photons to the detector device, having an inlet surface and an outlet surface facing the impact surface, and comprising pinholes connecting the inlet surface and the outlet surface,characterised in thatthe pinholes comprise one or more central pinholes and one or more peripheral pinholes, andat least one central pinhole and at least one peripheral pinhole are formed with focal opening depths different from each other, wherein a focal opening of the at least one central pinhole is located closer to the inlet surface than a focal opening of the at least one peripheral pinhole. 2. The apparatus according to claim 1, characterised in that the focal opening of at least one central pinhole is located farther from the inlet surface than the focal opening of at least one peripheral pinhole. 3. The apparatus according to claim 1 characterised in that the pinholes are formed to implement jointly a complete projection of a volume of interest. 4. The apparatus according to claim 3, characterised in that the one or more central pinholes are formed to implement a complete projection of a primary volume of interest being a part of the volume of interest. 5. The apparatus according to claim 1 characterised in that the detector device comprises a scintillation crystal converting the photons projected to the impact surface into light scintillations, and photodetectors arranged on the side of the scintillation crystal opposite the impact surface and suitable for determining locations of light scintillations. 6. The apparatus according to claim 5, characterised by comprising a scintillation crystal having parallel flat sides, the impact surface is formed on one flat side of the scintillation crystal, and the photodetectors are arranged centrally to grid points of a regular grid along the scintillation crystal flat side opposite the impact surface and the photons are projected by the pinholes onto image segments formed on the impact surface centred on central points of areas between the grid points. 7. The apparatus according to claim 1, characterised in that the pinholes have a conic or pyramid shape, and the shapes of the inlet window, outlet window and the focal opening of the pinholes are planar and can be transformed into each other by affine transformation. 8. The apparatus according to claim 1, characterised in that image segments are arranged without overlapping in the same number as the pinholes in accordance with the projection of the pinholes on the impact surface. 9. An aperture for an imaging apparatus, which apertureis suitable for the imaging of photons,has an inlet surface and an outlet surface, andcomprises pinholes connecting the inlet surface and the outlet surface,characterised in thatthe pinholes comprise one or more central pinholes and one or more peripheral pinholes, andat least one central pinhole and at least one peripheral pinhole are formed with focal opening depths different from each other, wherein a focal opening of the at least one central pinhole is located closer to the inlet surface than a focal opening of the at least one peripheral pinhole. 10. The aperture according to claim 9, characterised in that the focal opening of at least one central pinhole is located farther from the inlet surface than the focal opening of at least one peripheral pinhole. 11. The aperture according to claim 9, characterised in that the pinholes are formed to jointly implement a complete projection of a volume of interest. 12. The aperture according to claim 11, characterised in that one or more central pinholes are formed to implement a complete projection of a primary volume of interest being a part of the volume of interest. 13. The aperture according to claim 9, characterised in that the pinholes have a conic or pyramid shape, and the shapes of the inlet window, outlet window and focal opening of the pinholes are planar and can be transformed into each other by affine transformation. 14. A method for manufacturing an aperture of an imaging apparatus comprisingmodelling a reference aperture suitable for projecting photons, having an inlet surface and an outlet surface, and comprising pinholes connecting the inlet surface and the outlet surface, said reference aperture comprising pinholes with focal openings formed at equal distances from the inlet surfacecharacterised byselecting one or more central pinholes and one or more peripheral pinholes from the pinholes,defining an aperture by displacing in relation to the inlet surface along main axes of the pinholes the focal opening of at least one central pinhole and/or the focal opening of at least one peripheral pinhole, wherein a focal opening of the at least one central pinhole is displaced closer to the inlet surface and a focal opening of the at least one peripheral pinhole is displaced away from the inlet surface, andforming the defined aperture. 15. The method according to claim 14, characterised bydetermining sensitivity and/or resolution obtainable by the reference aperture and a detector device, by matching the detector device to the reference aperture, anddisplacing in relation to the inlet surface along the main axes of the pinholes the focal opening of at least one central pinhole and/or the focal opening of at least one peripheral pinhole, so that the sensitivity and/or resolution obtainable by the determined aperture and the matched detector device are altered in accordance with the spatial distribution of a photon emitting material being in the volume of interest. 16. The method according to claim 14, characterised in that the focal opening of at least one central pinhole is displaced away from the inlet surface and the focal opening of at least one peripheral pinhole is displaced closer to the inlet surface. 17. An imaging apparatus, comprising:a detector device configured to determine points of incidence of photons and having an impact surface;an aperture configured to project the photons to the detector device having an inlet surface and an outlet surface facing the impact surface; andpinholes connecting the inlet surface and the outlet surface and including one or more central pinholes and one or more peripheral pinholes, wherein at least one central pinhole and at least one peripheral pinhole are formed with focal opening depths different from each other and a focal opening of the at least one central pinhole is located farther from the inlet surface than a focal opening of the at least one peripheral pinhole. 18. An aperture for an imaging apparatus, comprising:an inlet surface and an outlet surface; andpinholes connecting the inlet surface and the outlet surface and including one or more central pinholes and one or more peripheral pinholes, wherein at least one central pinhole and at least one peripheral pinhole are formed with focal opening depths different from each other and a focal opening of the at least one central pinhole is located farther from the inlet surface than a focal opening of the at least one peripheral pinhole. 19. A method for manufacturing an aperture of an imaging apparatus, comprising:modeling a reference aperture suitable for projecting photons having an inlet surface and outlet surface with pinholes connecting the inlet surface and the outlet surface so that focal openings are formed at equal distances from the inlet surface;selecting one or more central pinholes and one or more peripheral pinholes from the pinholes;defining an aperture by displacing in relation to the inlet surface along main axes of the pinholes a focal opening of at least one central pinhole and/or a focal opening of at least one peripheral pinhole, wherein the focal opening of the at least one central pinhole is displaced away from the inlet surface and the focal opening of the at least one peripheral pinhole is displaced closer to the inlet surface; andforming the defined aperture.