WO2011030388A1 - 位相シフト素子 - Google Patents
位相シフト素子 Download PDFInfo
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- WO2011030388A1 WO2011030388A1 PCT/JP2009/004548 JP2009004548W WO2011030388A1 WO 2011030388 A1 WO2011030388 A1 WO 2011030388A1 JP 2009004548 W JP2009004548 W JP 2009004548W WO 2011030388 A1 WO2011030388 A1 WO 2011030388A1
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- phase shift
- phase
- light
- shift element
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/58—Optics for apodization or superresolution; Optical synthetic aperture systems
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/0075—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 with means for altering, e.g. increasing, the depth of field or depth of focus
Definitions
- the present invention relates to a phase shift element that reduces the beam spot diameter and reduces the change of the beam spot diameter with respect to the defocus amount.
- a condensing optical system such as a laser beam printer is required to have a small beam spot diameter and a small change in the beam spot diameter with respect to the defocus amount (that is, a large depth of focus).
- Patent Document 1 discloses a phase shift plate that reduces the beam spot diameter by causing a phase difference of ⁇ between the vicinity of the center of the beam spot and the other portion.
- Patent Document 2 discloses a phase shift plate that increases the depth of focus by causing a phase difference of ⁇ between a peripheral portion of a beam and an inner portion thereof.
- the conventional phase shift plate as described above is given to the beam due to factors such as variations in the thickness of the phase shift portion due to the manufacturing process, inclination between the phase shift plate with respect to the beam optical axis during product assembly, and changes in the light source wavelength.
- the phase shift element reduces the beam spot diameter and reduces the change in the beam spot diameter with respect to the defocus amount, and the beam spot with respect to the defocus amount when the phase difference deviates from the design value ( ⁇ ).
- a phase shift element having a simple structure with a small change in diameter has not been developed.
- the phase shift element reduces the beam spot diameter and reduces the change in the beam spot diameter with respect to the defocus amount.
- the phase difference deviates from the design value ( ⁇ )
- the beam spot diameter with respect to the defocus amount There is a need for a phase shift element having a simple structure with little change.
- the phase shift element according to the present invention includes an aperture arranged with a point on the optical axis of the condensing optical system as a center position, and a phase having a refractive index n that transmits light having a wavelength ⁇ that has passed through the aperture of the aperture. And a shift unit.
- the phase shift unit includes a first region having a thickness of t, a second region having a thickness of t ⁇ d, and a third region having a thickness of t + d, where t and d are constants.
- the second region and the third region are disposed adjacent to each other.
- the area of the phase shift portion through which the light that has passed through the opening is transmitted is Sa
- the area of the second region through which the light that has passed through the opening is transmitted is transmitted
- light that has passed through the opening is Sm
- the phase of the light that has passed through the second region is approximately ⁇ ahead of the phase of the light that has passed through the first region, and the phase of the light that has passed through the third region is Is delayed by approximately ⁇ from the phase of the light passing through the region.
- the image plane characteristics with respect to the defocus amount are asymmetric.
- the amount of phase advance and delay shifts from ⁇ due to the cancellation of the contribution of the asymmetric component by the second region and the contribution of the asymmetric component by the third region.
- the image plane characteristics with respect to the defocus amount continue to maintain symmetry in practice. As a result, when the phase difference (the amount of phase advance and delay) deviates from ⁇ , the change in the beam spot diameter with respect to the defocus amount becomes small.
- ⁇ 0.5 It is.
- the second and third regions are arranged around the optical axis.
- the spot diameter can be mainly reduced.
- the second and third regions are arranged at the periphery of the region of the phase shift portion through which the light passing through the opening is transmitted.
- the depth of focus can be mainly increased.
- the second and third regions are arranged concentrically around the intersection of the phase shift portion and the optical axis.
- the change in the beam spot diameter with respect to the defocus amount is reduced when the phase difference (phase advance and delay amounts) deviates from ⁇ in each direction in the plane perpendicular to the optical axis. It becomes possible.
- the second and third regions are arranged in a band shape.
- the phase difference (the amount of phase advance and delay) deviates from ⁇ in the direction perpendicular to the direction in which the band extends
- the change in the beam spot diameter with respect to the defocus amount can be reduced. It becomes possible.
- the second and third regions are arranged in a checkered pattern.
- the change in the beam spot diameter with respect to the defocus amount is small when the phase difference (phase advance and delay amounts) deviates from ⁇ for any shape of aperture. Further, by canceling out the asymmetric component more completely, the change in the beam spot diameter with respect to the defocus amount is further reduced.
- the second region and the third region are constituted by a set of regions having an area sufficiently smaller than the area of the opening.
- the change in the beam spot diameter with respect to the defocus amount is small when the phase difference (phase advance and delay amounts) deviates from ⁇ for any shape of aperture. Further, by canceling out the asymmetric component more completely, the change in the beam spot diameter with respect to the defocus amount is further reduced.
- the condensing optical system according to an aspect of the present invention includes the phase shift element according to the present invention. Therefore, the change in the beam spot diameter with respect to the defocus amount is reduced, and the condensing characteristic is improved.
- Example 1 shows an example of the condensing optical system containing the phase shift element by one Embodiment of this invention. It is a figure which shows the structure of the phase shift element by Example 1 of this invention.
- Example 1 shows the relationship between the defocus amount in the optical axis direction and the spot diameter when the phase advance of the second region and the delay of the third region phase are shifted from ⁇ with respect to the first region.
- FIG. 1 it is a figure which shows the relationship between the defocus amount of an optical axis direction, and a spot diameter at the time of changing (alpha).
- Example 1 it is a figure which shows the relationship between the defocus amount of an optical axis direction, and a spot diameter at the time of changing (beta).
- Example 2 shows the relationship between the defocus amount in the optical axis direction and the spot diameter when the phase advance of the second region and the phase delay of the third region deviate from ⁇ with respect to the first region.
- FIG. 2 it is a figure which shows the relationship between the defocus amount of an optical axis direction, and a spot diameter at the time of changing (alpha). It is a figure which shows the structure of the phase shift element by Example 3 of this invention.
- Example 3 the relationship between the defocus amount in the optical axis direction and the spot diameter when the phase advance of the second region and the phase delay of the third region deviate from ⁇ with respect to the first region, and It is a figure which shows the relationship between the defocus amount of an optical axis direction in an aperture, and a spot diameter. It is a figure which shows an example of the condensing optical system containing the phase shift element by other embodiment of this invention. It is a figure which shows the structure of the phase shift element by Example 1 of this invention. It is a figure which shows the structure of the phase shift element by Example 4 of this invention. It is a figure which shows the structure of the phase shift element by Example 5 of this invention.
- Comparative Example 1 it is a diagram showing the relationship between the defocus amount in the optical axis direction and the spot diameter when the phase delay of the second region with respect to the first region deviates from ⁇ .
- FIG. 9 is a diagram showing the relationship between the defocus amount in the optical axis direction and the spot diameter when the phase delay of the region of thickness td is deviated from ⁇ with respect to the region of thickness t in Comparative Example 2. is there.
- FIG. 1 is a diagram illustrating an example of a condensing optical system including a phase shift element according to an embodiment of the present invention.
- the phase shift element 100A includes an aperture 101A arranged perpendicular to the optical axis and a phase shift unit 103A arranged perpendicular to the optical axis.
- the surfaces of the aperture 101A and the phase shift unit 103A are arranged perpendicular to the beam direction.
- the aperture 101A and the phase shift unit 103A are arranged at an interval, but may be arranged so as to contact each other.
- the beam that has passed through the aperture 101A and the phase shift unit 103A is condensed on the image plane 203A by a condensing lens 201A having a focal length f.
- the phase shift element 100A is arranged so as to improve the beam condensing state on the image plane 203A.
- FIG. 2 is a diagram showing the configuration of the phase shift element according to the first embodiment of the present invention.
- FIG. 2A is a diagram showing the configuration of the aperture 1101.
- the aperture 1101 includes an opening 11011 that allows a beam to pass therethrough and a shielding portion 11013 that shields the beam.
- FIG. 2B is a diagram illustrating a configuration of the phase shift unit 1103.
- the phase shift unit 1103 is formed of a transparent plastic as an example.
- the phase shift unit 1103 includes a first region 11031 having a thickness t, a second region 11033 having a thickness t ⁇ d, and a third region 11033 having a thickness t + d.
- t and d are constants, and d is determined so as to satisfy the following expression.
- ⁇ is the wavelength of light used
- n is the refractive index of the material of the phase shift unit 1103.
- the material of the phase shifter 1103 is plastic in this example, but may be other materials such as glass.
- phase shift portions having different thicknesses as described above may be manufactured by transferring a mold core created by an NC processing machine to a plastic or glass material by injection molding or imprinting.
- the mold core created by etching may be transferred to a plastic or glass material by injection molding or imprinting.
- a thin film corresponding to a difference in thickness corresponding to the thickness difference may be formed on the base material by vapor deposition or sputtering.
- FIG. 2C is a diagram showing a configuration of a phase shift element 1100 in which an aperture 1101 and a phase shift unit 1103 are combined.
- FIG. 2C is a view of the phase shift element 1100 observed from the aperture 1101 side.
- the intersection of the optical axis and the surface of the phase shift unit is defined as the origin
- the direction of the optical axis is defined as the z axis
- the x axis and the y axis are defined in the plane of the phase shift unit.
- the x and y axis directions are shown in FIG. 2 and other figures.
- the region through which the light that has passed through the opening 11011 of the phase shift unit 1103 is transmitted is a circle centered on the origin.
- the second region 11033 and the third region 11035 are provided adjacent to the outer periphery in the vicinity of the circular outer periphery and adjacent to each other with the circular concentric circle as a boundary.
- Sa is the area of the phase shift portion through which the light passing through the opening 11011 is transmitted.
- Sa is the sum of the areas of the first region 11031, the second region 11033, and the third region 11035 through which the light transmitted through the opening 11011 is transmitted.
- Sp be the area of the second region 11033 through which the light passing through the opening 11011 is transmitted.
- the area of the third region 11035 through which light that has passed through the opening 11011 is transmitted is Sm.
- ⁇ and ⁇ are defined by the following equations.
- ⁇ passes through the opening 11011, which is the total value of the area of the second region 11033 through which the light passing through the opening 11011 passes and the area of the third region 11035 through which the light passed through the opening 11011 passes. It is a ratio with respect to the area of the phase shift part which the transmitted light permeate
- FIG. 3 shows the defocus amount in the optical axis direction when the phase advance of the second region 11033 and the phase delay of the third region 11035 are shifted from ⁇ with respect to the first region 11031 in the first embodiment. It is a figure which shows the relationship between a spot diameter.
- the horizontal axis in FIG. 3 indicates that f is the focal length of the condenser lens and D is the aperture diameter in the x-axis direction.
- 3 represents the defocus amount in the optical axis direction normalized by the vertical axis in FIG.
- FIG. 17 is a diagram showing a configuration of a conventional phase shift element. This phase shift element is referred to as Comparative Example 1.
- FIG. 17A is a diagram showing the configuration of the aperture 10101.
- the aperture 10101 includes an opening portion 101011 that allows a beam to pass therethrough and a shielding portion 101013 that shields the beam.
- FIG. 17B is a diagram illustrating a configuration of the phase shift unit 10103.
- the phase shift unit 10103 is formed of a transparent plastic as an example.
- the phase shift unit 10103 includes a first region 101031 having a thickness t and a second region 101033 having a thickness t + d.
- the second area 101033 corresponds to the third area 11035 of the first embodiment.
- FIG. 17C is a diagram illustrating a configuration of a phase shift element 10100 in which the aperture 10101 and the phase shift unit 10103 are combined.
- FIG. 17C is a view of the phase shift element 10100 observed from the aperture 10101 side.
- the region through which the light that has passed through the opening portion 101011 of the phase shift portion 10103 is transmitted is a circle centered on the origin.
- the second region 101033 is provided in the vicinity of the outer periphery of the circle and adjacent to the outer periphery, with the circular concentric circle as a boundary.
- FIG. 18 is a diagram illustrating the relationship between the defocus amount in the optical axis direction and the spot diameter when the phase delay of the second region 101033 is deviated from ⁇ with respect to the first region 101031 in Comparative Example 1. is there.
- the horizontal and vertical axes in FIG. 18 are the same as the horizontal and vertical axes in FIG.
- the spot diameter changes with respect to the defocus amount. Further, the ratio (absolute value) of the change amount of the spot diameter to the change amount of the defocus amount increases in accordance with the shift (shift) amount of the phase delay from ⁇ .
- the defocus amount changes even when the amount of shift (shift) from ⁇ of the phase advance and phase lag increases compared to FIG. 18 showing the result according to the first comparative example.
- the ratio (absolute value) of the change amount of the spot diameter to the amount remains small. That is, when the phase difference deviates from the design value ( ⁇ ), the change in the beam spot diameter with respect to the change in the defocus amount remains small.
- FIG. 4 is a diagram illustrating the relationship between the defocus amount in the optical axis direction and the spot diameter when ⁇ is changed in the first embodiment.
- FIG. 5A is a diagram illustrating the relationship between the defocus amount in the optical axis direction and the spot diameter when ⁇ is changed in the first embodiment.
- the phase advance and phase lag (phase shift amount) were set to 0.9 ⁇ .
- FIG. 5B is a diagram showing the relationship between ⁇ and the ratio of the change amount of the spot diameter to the change amount of the defocus amount.
- the horizontal axis in FIG. 5 indicates ⁇ , and the vertical axis in FIG. 5 indicates the ratio of the change amount of the spot diameter to the change amount of the defocus amount when the defocus amount is zero.
- the above ratio is described as “inclination at zero defocus” in FIG. 5B.
- the phase shift element 1100 of the first embodiment uses the second region 11033 and the third region 11035 in the same manner. , Function similarly to a phase plate replaced with a phase shift region of only + ⁇ or ⁇ .
- the wavefront of the focusing optical system itself is ⁇ 1
- phase shift plate for example, the phase plate of Comparative Example 1
- the phase shift amount of the phase plate changes due to a wavelength change of the light source or a thickness error of the phase shift portion, the odd symmetry of the wavefront is disturbed and the image plane characteristics become asymmetric. This phenomenon has been described with reference to FIG.
- FIG. 6 is a diagram showing a configuration of the phase shift element according to the second embodiment of the present invention.
- FIG. 6A is a diagram showing the configuration of the aperture 2101.
- the aperture 2101 includes an opening 21011 that allows a beam to pass therethrough and a shielding portion 21013 that shields the beam.
- FIG. 6B is a diagram illustrating a configuration of the phase shift unit 2103.
- the phase shift unit 2103 is formed of a transparent plastic as an example.
- the phase shift unit 2103 includes a first region 21031 having a thickness t, a second region 21033 having a thickness t ⁇ d, and a third region 21035 having a thickness t + d.
- t and d are constants, and d is determined so as to satisfy the following expression.
- ⁇ is the wavelength of light used
- n is the refractive index of the material of the phase shift unit 2103 (in this example, plastic).
- FIG. 6C is a diagram illustrating a configuration of a phase shift element 2100 in which the aperture 2101 and the phase shift unit 2103 are combined.
- FIG. 6C is a diagram of the phase shift element 2100 observed from the aperture 2101 side.
- the region of the phase shift portion 2103 through which light that has passed through the opening 21011 is transmitted is a circle centered on the origin.
- the second region 21033 and the third region 21035 are provided adjacent to each other near the origin with the circular concentric circle as a boundary.
- Equation (6) and Equation (7) are defined by Equation (6) and Equation (7) as in the first embodiment.
- FIG. 7 shows the defocus amount in the optical axis direction when the phase advance of the second region 21033 and the phase delay of the third region 21035 deviate from ⁇ with respect to the first region 21031 in the second embodiment. It is a figure which shows the relationship between a spot diameter.
- the spot diameter is almost constant even when the phase advance and phase lag change in the range of 0.8 ⁇ to 1.2 ⁇ .
- a phase shift element in which the second region 21033 having a thickness td and the third region 21033 having a thickness t + d in the second embodiment is replaced with a region having a thickness td is referred to as a comparative example 2.
- FIG. 19 shows the relationship between the defocus amount in the optical axis direction and the spot diameter when the phase delay of the region with the thickness td deviates from ⁇ with respect to the region with the thickness t in Comparative Example 2.
- FIG. The horizontal and vertical axes in FIG. 19 are the same as the horizontal and vertical axes in FIG.
- FIG. 8 is a diagram illustrating the relationship between the defocus amount in the optical axis direction and the spot diameter when ⁇ is changed in the second embodiment.
- FIG. 9 is a diagram showing the configuration of the phase shift element according to the third embodiment of the present invention.
- FIG. 9A is a diagram showing the configuration of the aperture 3101.
- the aperture 3101 includes an opening 31011 that allows a beam to pass therethrough and a shielding portion 31013 that shields the beam.
- FIG. 9B is a diagram illustrating a configuration of the phase shift unit 3103.
- the phase shift unit 3103 is formed of a transparent plastic as an example.
- the phase shift unit 3103 includes a first region 31031 having a thickness t, a second region having a thickness t ⁇ d and a third region having a thickness t + d arranged in a checkered pattern, Consists of.
- t and d are constants, and d is determined so as to satisfy the following expression.
- ⁇ is the wavelength of light used
- n is the refractive index of the material of the phase shift unit 2103 (in this example, plastic).
- FIG. 9C is a diagram illustrating a configuration of a phase shift element 3100 in which an aperture 3101 and a phase shift unit 3103 are combined.
- FIG. 9C is a diagram of the phase shift element 3100 observed from the aperture 3101 side.
- the region of the phase shift portion 3103 through which light that has passed through the opening 31011 is transmitted is a square centered at the origin (intersection of diagonal lines).
- the second region and the third region are arranged adjacent to each other in a checkered pattern, and form a band extending in the y-axis direction as a whole.
- the band is symmetric about the y-axis.
- the square area of the checkered pattern unit is sufficiently smaller than the area of the opening. Specifically, when the unit quadrangle is a square, the length of one side of the square is preferably 1/50 or less of the diameter of the opening.
- Equation (6) and Equation (7) are defined by Equation (6) and Equation (7) as in the first embodiment.
- FIG. 10 shows the defocus amount and spot in the optical axis direction when the phase advance of the second region and the phase delay of the third region deviate from ⁇ with respect to the first region 31031 in Example 3.
- FIG. 10 is a diagram illustrating a relationship between a diameter and a relationship between a defocus amount in the optical axis direction in the aperture 3101 and a spot diameter.
- the horizontal axis in FIG. 10 is the same as the horizontal axis in FIG.
- the spot diameter in the x-axis direction by the phase shift element 3100 of Example 3 is smaller than the spot diameter by the aperture 3101.
- the spot diameter in the y-axis direction by the phase shift element 3100 of the third embodiment is the same as the spot diameter by the aperture 3101.
- the reason is as follows.
- the phase shift element 3100 has a phase change in the x-axis direction.
- the entire phase shift region is equiphase regardless of whether it is positive or negative, and therefore the phase shift element 3100 does not have a phase change in the y-axis direction. Therefore, the effect of the phase shift element 3100 on the spot diameter in the y-axis direction is not different from the effect of the aperture 3101.
- the second region and the third region are arranged adjacent to a checkered pattern in which the area of the unit square is sufficiently smaller than the area of the opening, the second region And the difference in position of the third region is negligible, so the asymmetric component is better canceled out.
- the second region and the third region may be configured by a set of regions (unit regions) having a sufficiently small area compared to the area of the opening.
- the length representing the unit region is preferably 1/50 or less of the diameter of the opening.
- FIG. 11 is a diagram showing an example of a condensing optical system including a phase shift element according to another embodiment of the present invention.
- a lens system 201B in FIG. 11 is an asymmetric lens system in the x-axis direction and the y-axis direction, and is used in, for example, a laser beam printer.
- the phase shift element 100B includes an aperture 101B and a phase shift unit 103B.
- a condensing optical system that is asymmetric in the x-axis direction and the y-axis direction also has asymmetric image plane characteristics in the x-axis direction and the y-axis direction. Therefore, it is effective to use a phase shift element that is asymmetric in the x-axis direction and the y-axis direction.
- FIG. 12 is a diagram showing the configuration of the phase shift element according to the fourth embodiment of the present invention.
- FIG. 12A shows the configuration of the aperture 4101.
- the aperture 4101 includes an opening 41011 that allows a beam to pass therethrough and a shielding portion 41013 that shields the beam.
- the opening 41011 is oval with the major axis in the x-axis direction.
- FIG. 12B is a diagram illustrating a configuration of the phase shift unit 4103.
- the phase shift unit 4103 is formed of a transparent plastic as an example.
- the phase shift unit 4103 concentrically adjoins the first region 41031 having a thickness t, the second region having a thickness t ⁇ d, and the third region having a thickness t + d with the origin as the center. And an area 41033 arranged in the same manner.
- t and d are constants, and d is determined so as to satisfy the following expression.
- ⁇ is the wavelength of light used
- n is the refractive index of the material of the phase shift unit 2103 (in this example, plastic).
- FIG. 12C is a diagram illustrating a configuration of a phase shift element 4100 in which the aperture 4101 and the phase shift unit 4103 are combined.
- FIG. 12C shows the phase shift element 4100 observed from the aperture 4101 side.
- the region of the phase shift portion 4103 through which light that has passed through the opening 41011 is transmitted has an elliptical shape with the origin at the center and the major axis in the x-axis direction.
- the second region and the third region are arranged adjacent to each other with a concentric circle centered on the origin. Adjacent pairs of the second region and the third region are arranged adjacent to each other. Adjacent pairs of the second region and the third region are arranged in the vicinity of the outer periphery of the elliptical long axis (x-axis) direction.
- the phase shift element 4100 increases the image plane depth in the x-axis direction, that is, the major axis direction of the elliptical opening.
- FIG. 13 is a diagram showing a configuration of a phase shift element according to the fifth embodiment of the present invention.
- FIG. 13A is a diagram showing the configuration of the aperture 5101.
- the aperture 5101 includes an opening 51011 that allows a beam to pass therethrough and a shielding portion 51013 that shields the beam.
- the opening 51011 is oval with the major axis in the x-axis direction.
- FIG. 13B is a diagram illustrating a configuration of the phase shift unit 5103.
- the phase shift portion 5103 is formed of a transparent plastic as an example.
- the phase shift unit 5103 includes a first region 51031 having a thickness t, a second region having a thickness td, and a third region having a thickness t + d adjacent to each other in a band shape in the x-axis direction. And an arranged band-like region 51033.
- t and d are constants, and d is determined so as to satisfy the following expression.
- ⁇ is the wavelength of light used
- n is the refractive index of the material of the phase shift unit 5103 (in this example, plastic).
- FIG. 13C is a diagram showing a configuration of a phase shift element 5100 in which an aperture 5101 and a phase shift unit 5103 are combined.
- FIG. 13C is a diagram of the phase shift element 5100 observed from the aperture 5101 side.
- the region of the phase shift portion 5103 through which light that has passed through the opening 51011 is transmitted has an elliptical shape with the origin at the center and the major axis in the x-axis direction.
- the second region and the third region are disposed adjacent to each other as a band in the x-axis direction.
- adjacent band-like pairs of the second region and the third region are arranged near the outer periphery of the elliptical short axis (y-axis) direction.
- the phase shift element 5100 increases the image plane depth in the y-axis direction, that is, in the short-axis direction of the elliptical opening.
- FIG. 14 is a diagram showing the configuration of the phase shift element according to the sixth embodiment of the present invention.
- FIG. 14A is a diagram showing the configuration of the aperture 6101.
- the aperture 6101 includes an opening 61011 through which a beam passes and a shielding unit 61013 that shields the beam.
- the opening 61011 is oval with the major axis in the x-axis direction.
- FIG. 14B is a diagram illustrating a configuration of the phase shift unit 6103.
- the phase shift unit 6103 is formed of a transparent plastic as an example.
- the phase shift unit 6103 includes a first region 61031 having a thickness t, a second region 61033 having a thickness td, and a third region 61035 having a thickness t + d.
- the second region 61033 and the third region 61035 are arranged adjacent to each other in a concentric ellipse shape with the optical axis position as the center.
- t and d are constants, and d is determined so as to satisfy the following expression.
- ⁇ is the wavelength of light used
- n is the refractive index of the material of the phase shift unit 6103 (in this example, plastic).
- FIG. 14C is a diagram showing a configuration of a phase shift element 6100 in which an aperture 6101 and a phase shift unit 6103 are combined.
- FIG. 14C is a view of the phase shift element 6100 observed from the aperture 6101 side.
- the region of the phase shift portion 6103 through which light that has passed through the opening portion 6101 is transmitted has an elliptical shape with the origin at the center and the major axis in the x-axis direction.
- the second region 61033 and the third region 61035 are arranged adjacent to each other with a concentric ellipse centered on the origin. In the present embodiment, adjacent pairs of the second region and the third region are arranged in the vicinity of the outer periphery of the ellipse at a distance from the outer periphery.
- the phase shift element 6100 increases the image plane depth in the x-axis direction and the y-axis direction.
- FIG. 15 is a diagram illustrating an example of another embodiment of the present invention in which the phase shift unit 103C is provided on the surface of the lens 201C.
- the phase shift unit functions similarly even if it is provided on the surface of the lens. Therefore, in Examples 1 to 6, the phase shift unit may be provided on the lens surface.
- the transfer shift element 100C of the present embodiment includes an aperture 101C and a phase shift unit 103C provided on the surface of the lens 201C.
- FIG. 16 is a diagram showing the relationship between ⁇ , the spot diameter, and the side lobe intensity in the phase shift element having the same structure as that of the first embodiment.
- the horizontal axis of FIG. 16 indicates ⁇ defined by the equation (6).
- shaft of FIG. 16 shows a spot diameter (right scale), peak intensity, and side lobe intensity (left scale).
- the spot diameter is the same as the vertical axis in FIG.
- the intensity on the vertical axis is obtained by normalizing the peak intensity and the side lobe intensity with the peak intensity without phase change.
- the second region and the third region are regions in which the phase is changed by ⁇ with respect to the first region.
- ⁇ 0.9
- the phase shift element is a region that occupies 90% of the area outside the concentric circle centered on the optical axis, in the region of the phase shift portion through which the light that has passed through the aperture is transmitted, is a region that changes the phase by ⁇ .
- a region that occupies an area of 10% inside a concentric circle centered on the optical axis is the first region.
- phase shift element functions in the same manner as the phase shift element according to the second embodiment.
- the decrease in spot diameter as ⁇ decreases from 1 to 0.8 corresponds to the decrease in spot diameter as ⁇ increases from 0 in FIG.
- the side lobe intensity is about 0.1 at the maximum.
- the reason for the step change in the vicinity is that the side lobe intensity reaches 50% of the peak intensity in the vicinity of the above value, and the spot diameter evaluated by the full width at half maximum of the peak intensity expands to a range including the side lobe. It is.
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Abstract
Description
0<α<1
の範囲で
α=0 または α=1
の場合よりも、前記集光光学系の集光面におけるスポット径を小さくすること及び焦点深度を大きくすることの少なくとも一方を実現するように
α
を定めている。
β=0.5
である。
であれば、SpとSmが等しいので、第2の領域による非対称成分の寄与と第3の領域による非対称成分の寄与とがほぼ完全に打ち消しあう。その結果、位相差(位相の進み及び遅れの量)がπからずれたときに、デフォーカス量に対するビームスポット径の変化がさらに小さくなる。
α=0.1
β=0.5
とした。
α=0.9
β=0.0
とした。
β=0.5
とした。
0<α<0.15
であるのが好ましい。
α=0.1
とした。また、位相進み及び位相遅れ(位相シフト量)は、0.9πとした。
β=0.5
の場合に、デフォーカス量の変化量に対するスポット径の変化量の割合(絶対値)は最小となる。デフォーカス量の変化量に対するスポット径の変化量の割合(絶対値)を抑えるには、
の場合に、デフォーカス量の変化量に対するスポット径の変化量の割合(絶対値)が最小となる理由は以下のとおりである。
の場合に上記凹領域と上記凸領域の面積が等しくなるので、双方からの寄与による非対称成分は、ほぼ打ち消され、図3に示したように最終的に得られる像面特性は実用的には対称性を保ち続ける。
α=0.1
β=0.5
とした。
β=0.5
とした。
α=0.1
β=0.5
とした。
β=0.5
とすることができる。第2に、非対称成分がよりよく打ち消される。たとえば、第2の領域及び第3の領域を同心円状に配置した場合には、それぞれの領域は外側と内側に配置される。したがって、
β=0.5
であっても、第2の領域及び第3の領域の位置の差により、電場の非対称成分は完全に打ち消されることはない。これに対して、第2の領域及び第3の領域を、単位の四角形の面積が開口部の面積に比較して十分に小さい市松模様状に隣接して配置する場合には、第2の領域及び第3の領域の位置の差は無視しうるので、非対称成分がよりよく打ち消される。
0<α<0.15
であるのが好ましい。図16に示すように、上記の範囲ではサイドローブの強度も押さえられる。
α=0.9
である位相シフト素子は、開口部を通過した光が透過する位相シフト部の領域の内、光軸を中心とする同心円の外側の90%の面積を占める領域が、位相をπ変化させる領域であり、光軸を中心とする同心円の内側の10%の面積を占める領域が第1の領域である。これに対して、図6に示した実施例2による位相シフト素子においては、
α=0.1
であるので、光軸を中心とする同心円の外側の90%の面積を占める領域が第1の領域であり、光軸を中心とする同心円の内側の10%の面積を占める領域が位相をπ変化させる領域である。位相の変化は相対的なものであるので、実施例1と同様の構造を有し、
α=0.9
である位相シフト素子は、実施例2による位相シフト素子と同様に機能する。図16において、αが1から0.8に減少するにしたがって、スポット径が小さくなることは、図8において、αが0から増加するにしたがって、スポット径が小さくなることに対応する。
0.8<α<1.0
であるのが好ましい。図16に示すように、サイドローブ強度は、最大で約0.1である。
α=0.75
付近でステップ状に変化している理由は、上記の値付近でサイドローブ強度がピーク強度の50%に達し、ピーク強度の半値全幅で評価したスポット径が、サイドローブを含む範囲まで拡大するためである。
Claims (9)
- 集光光学系の光軸上の点を中心位置として配置されたアパーチャと、前記アパーチャの開口を通過した波長λの光を透過させる屈折率nの材質からなる位相シフト部と、を備えた、位相シフト素子であって、t及びdを定数として、前記位相シフト部は、tの厚さの第1の領域と、t-dの厚さの第2の領域と、t+dの厚さの第3の領域からなり、第2の領域と第3の領域とは隣接して配置されており、前記開口を通過した光が透過する前記位相シフト部の面積をSa、前記開口を通過した光が透過する第2の領域の面積をSp、前記開口を通過した光が透過する第3の領域の面積をSm、
0<α<1
の範囲で
α=0 または α=1
の場合よりも、前記集光光学系の集光面におけるスポット径を小さくすること及び焦点深度を大きくすることの少なくとも一方を実現するように
α
を定めた位相シフト素子。 - β=0.5
である請求項1に記載の位相シフト素子。 - 第2及び第3の領域が前記光軸の周辺に配置された請求項1又は2に記載の位相シフト素子。
- 第2及び第3の領域が、前記開口を通過した光が透過する前記位相シフト部の領域の周縁部に配置された請求項1又は2に記載の位相シフト素子。
- 第2及び第3の領域が、前記位相シフト部と前記光軸との交点を中心とする同心円状に配置された請求項1又は2に記載の位相シフト素子。
- 第2及び第3の領域が、帯状に配置された請求項1又は2に記載の位相シフト素子。
- 第2及び第3の領域が、市松模様状に配置された請求項1又は2に記載の位相シフト素子。
- 第2の領域及び第3の領域が、前記開口の面積に比較して十分に小さい面積の領域の集合から構成されている請求項1又は2に記載の位相シフト素子。
- 請求項1から8のいずれか1項に記載の位相シフト素子を含む集光光学系。
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JP2015028564A (ja) * | 2013-07-30 | 2015-02-12 | 京セラドキュメントソリューションズ株式会社 | 光源ユニット及びこれを用いた画像形成装置 |
Citations (5)
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JPH01315041A (ja) * | 1988-06-14 | 1989-12-20 | Nec Corp | 光ヘッド装置及び情報記録再生方法 |
JPH04123016A (ja) * | 1990-09-14 | 1992-04-23 | Canon Inc | レーザ装置 |
JPH0689455A (ja) * | 1991-07-29 | 1994-03-29 | Sony Corp | 光ピックアップ |
JPH0695038A (ja) * | 1992-03-19 | 1994-04-08 | Matsushita Electric Ind Co Ltd | 超解像走査光学装置、光学装置の超解像用光源装置及び光学装置の超解像用フィルター |
JPH0784221A (ja) * | 1993-09-14 | 1995-03-31 | Matsushita Electric Works Ltd | 集光用光学装置とこれに付加される光学的付加装置及びこれらを用いた測定機器 |
-
2009
- 2009-09-11 KR KR1020127007867A patent/KR101362508B1/ko active IP Right Grant
- 2009-09-11 JP JP2010544516A patent/JP4953108B2/ja not_active Expired - Fee Related
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Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH01315041A (ja) * | 1988-06-14 | 1989-12-20 | Nec Corp | 光ヘッド装置及び情報記録再生方法 |
JPH04123016A (ja) * | 1990-09-14 | 1992-04-23 | Canon Inc | レーザ装置 |
JPH0689455A (ja) * | 1991-07-29 | 1994-03-29 | Sony Corp | 光ピックアップ |
JPH0695038A (ja) * | 1992-03-19 | 1994-04-08 | Matsushita Electric Ind Co Ltd | 超解像走査光学装置、光学装置の超解像用光源装置及び光学装置の超解像用フィルター |
JPH0784221A (ja) * | 1993-09-14 | 1995-03-31 | Matsushita Electric Works Ltd | 集光用光学装置とこれに付加される光学的付加装置及びこれらを用いた測定機器 |
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JP2015028564A (ja) * | 2013-07-30 | 2015-02-12 | 京セラドキュメントソリューションズ株式会社 | 光源ユニット及びこれを用いた画像形成装置 |
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KR20120048029A (ko) | 2012-05-14 |
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