JP4541757B2 - Polarizing element - Google Patents

Description

  The present invention relates to a polarization element such as a polarization separation element that has a plurality of wavelengths or band lights and is used in a relatively wide incident angle range. For example, the present invention relates to a photographing optical system, a projection display device (projector), and an image processing device. The present invention relates to various optical devices such as semiconductor manufacturing apparatuses.

  Conventionally, it has been known that a SWS (sub-wavelength structure) element having a one-dimensional grating shape with a period equal to or less than a wavelength has a structural birefringence.

In general, in a one-dimensional grating as shown in FIG. 24, a medium of n ₁ and n ₂ repeats at a ratio of a: b, and the effective refractive index of each polarized light is expressed by equations (1) and (2). The

In a one-dimensional lattice, when n1 is a dielectric and n2 is air, a filling factor f, which is a ratio to the pitch of the medium, is expressed by Equation (3). In this example, the etching is performed so that the filling factor is about 0.5.
f = a / (a + b) (3)
FIG. 25 shows a change in effective refractive index with respect to the filling factor f of TiO2 in a lattice in which the dielectric of a one-dimensional lattice is TiO2 (n1 = 2.304) and one is air (n2 = 1.0). It is a graph.

From FIG. 25, n _TE > n _TM regardless of the value of f.

  As a condition that the one-dimensional grating as described above can be described by an effective refractive index, it is necessary that the pitch of the grating is sufficiently small so that diffraction does not occur.

When the refractive index of the incident-side medium of the grating having the pitch d as shown in FIG. 3 is n1, the refractive index of the emission-side medium is n2, the incident angle of incident light is θ1, and the exit angle of emitted light by diffraction is θ2. When the adjacent optical path difference (L1-L2) is an integral multiple of the wavelength, diffracted light is generated. This is expressed by conditional expression (4), and diffraction occurs when this expression holds.
dn1sin θ1-dn2sin θ2 = mλ (4)
However, m is an integer. If this equation (4) is set so that there is no solution other than m = 0, diffraction does not occur.

Equation (4) is transformed into Equation (5), where n is the medium on the incident side and the exit side.
sin θ1−sin θ2 = mλ / dn (5)
Assuming that θ1 and θ2 take arbitrary values, the left side of equation (5) is in the range of equation (6).
-2 ≤ left side ≤ 2 (6)
Therefore, if λ / dn is larger than the left side, diffraction does not occur. That is, Equation (7) is a condition for preventing diffraction from occurring at all incident angles.
d <λ / 2n (7)
A manufacturing method is proposed in Patent Document 1 for an element having a so-called cross-girder structure in which the one-dimensional lattices are stacked so as to be orthogonal to each other. A cross-layered photosensitive material having photosensitive characteristics is arranged in a laminated structure, and each is exposed and etched to realize a cross-beam structure. Examples are only schematic diagrams of a cross-beam structure, and there is no description of numerical examples showing the size of specific shapes, but the pitch of the grating must be less than the wavelength in order to use as a photonic crystal In addition, the above-mentioned conditions that do not cause diffraction must be satisfied. The medium on the incident side and the emission side of the element is air (n = 1.0), and it can be considered that the pitch is about half the wavelength from the conditional expression (7).
JP 2001-209189 A

  However, when the above element is used in a configuration in which it is embedded between two prisms, such as a polarization separation element, diffraction is caused by the fact that the refractive index n in the conditional expression (7) is larger than that of air. The pitch for preventing it from becoming narrower. In the one-dimensional grating as described above, if the pitch is narrowed without changing the ratio of the medium to the pitch (filling factor) and the thickness (h) of the grating, the ratio of the height and width of the grating (aspect ratio) increases. As a result, there was a problem that the manufacturing difficulty level increased.

  In view of these problems, the present invention sets the pitch optimally according to the incident angle and direction of the light beam to be used, thereby simplifying the manufacturing while maintaining the condition that no diffraction occurs with respect to the total light beam. It is an object to obtain a polarizing element having a configuration.

In order to solve the above problem, the present invention provides a layer having a refractive index periodic structure having a period equal to or shorter than a use wavelength in a first periodic direction parallel to a predetermined surface, and the first periodic in parallel to the predetermined surface. A polarizing element in which both sides of a polarization separation layer in which a layer having a refractive index periodic structure with a period equal to or shorter than a use wavelength in a second periodic direction perpendicular to the direction is laminated in a direction perpendicular to the predetermined plane are sandwiched by prisms There,
The absolute value of the photoelastic constant of the prism is smaller than 1.0 × 10 −8 cm 2 / N, and the polarization separation layer is inclined by 45 ° with respect to the incident surface of the incident side prism of the two prisms, Of the first periodic direction and the second periodic direction, the period in the periodic direction that is nearly parallel to the incident plane of the light beam having the maximum incident angle among the light beams incident on the polarizing element is PA, and is orthogonal thereto. When the period in the period direction is PB, the polarizing element is characterized by satisfying the following conditional expression.
PA <PB

The present invention includes a layer having a refractive index periodic structure having a period equal to or shorter than a use wavelength in a first periodic direction parallel to a predetermined surface, and a second periodic direction parallel to the predetermined surface and perpendicular to the first periodic direction. A polarizing element in which a layer having a refractive index periodic structure with a period equal to or shorter than the used wavelength is sandwiched between prisms on both sides of the polarization separation layer laminated in a direction perpendicular to the predetermined plane,
The absolute value of the photoelastic constant of the prism is smaller than 1.0 × 10 −8 cm 2 / N, and the polarization separation layer is inclined by 45 ° with respect to the incident surface of the incident side prism of the two prisms, When the central light beam of the light beam incident on the polarizing element is a representative light beam, the light beam is incident on the incident plane of the first periodic direction and the second periodic direction when the representative light beam is incident on the polarizing element. On the other hand, a polarizing element is characterized in that the following conditional expression is satisfied, where PA is a period in a periodic direction that is nearly parallel, and PB is a period in a periodic direction that is orthogonal thereto.
PA <PB

The present invention includes a layer having a refractive index periodic structure having a period equal to or shorter than a use wavelength in a first periodic direction parallel to a predetermined surface, and a second periodic direction parallel to the predetermined surface and perpendicular to the first periodic direction. A polarizing element in which a layer having a refractive index periodic structure with a period equal to or shorter than the used wavelength is sandwiched between prisms on both sides of the polarization separation layer laminated in a direction perpendicular to the predetermined plane,
The prism has an absolute value of a photoelastic constant smaller than 1.0 × 10 −8 cm 2 / N, and the polarization separation layer is inclined by 45 ° with respect to the incident surface of the incident side prism of the two prisms, When the light beam passing through the optical axis of the exit side prism among the two prisms placed on the exit side of the light beam exiting from the polarizing element is used as a representative light beam, the first periodic direction and the second periodic direction Among them, when the period in the periodic direction that is nearly parallel to the incident plane when the representative light beam is incident on the polarizing element is PA and the period in the periodic direction perpendicular to the same is PB, the following conditional expression must be satisfied. It was set as the characteristic polarizing element.
PA <PB

  Using the polarizing element, the light beam from the light source unit is guided to a modulation unit that modulates based on an image signal, and the light beam modulated by the modulation unit is projected onto a predetermined surface by a projection optical system. Thus, an effective projection display device can be obtained.

  According to the present invention, as described above, the structure in which the polarizing element is sandwiched between the prisms has a simple shape in manufacture, and the polarizing element performance has high performance in a wide range in both wavelength characteristics and incident angle characteristics. There is an effect that a polarizing element can be realized.

  FIG. 1 is a configuration diagram of a polarization splitting prism according to a first embodiment of the present invention. Table 1 shows design values representing the configuration of the first embodiment.

  In FIG. 1, the polarization separation layer (23) is inclined 45 ° with respect to the incident surface (25) of the prism. P-polarized light (18) and S-polarized light (20) incident on the incident surface (25) perpendicularly enter the polarization separation layer (23), and reflect (21) the S-polarized light. The light is emitted from an exit surface (26) different from the entrance surface (25) in 22). The P-polarized light is transmitted (19) and is emitted from the exit surface (27) on the exit-side prism (24).

  FIG. 2 is a schematic diagram showing the direction of the lattice. The incident plane (28) when entering the polarization separation layer (23) and the first one-dimensional grating of the polarization separation layer are parallel to each other as shown in FIG. The second one-dimensional grating is arranged perpendicular to the incident plane as shown in FIG.

  4 is a view of the lattice obliquely, FIG. 5 is a cross-sectional structural view of the lattice viewed from the direction A indicated by the arrow 29 in FIG. 2, and FIG. 6 is a direction B indicated by the arrow 30 in FIG. It is the cross-section figure of the grating | lattice seen from. The first one-dimensional lattice is an L layer (101, 103) in a lattice direction P in which air and a dielectric are alternately repeated. The second one-dimensional lattice is an H layer in a lattice direction V in which air and a dielectric are alternately repeated. (102). It is possible to achieve polarization separation with a relatively simple configuration of three layers as a whole. Moreover, TiO2 is used as the dielectric.

  The reason why the layers are the H layer and the L layer represents the level of the effective refractive index with respect to the S-polarized light to be reflected. The thickness of the one-dimensional grating layer in the grating direction V is 64 nm, which is sufficient to completely achieve S-polarized light reflection. In general, it is known that when a light is incident on a medium having a low refractive index from a medium having a high refractive index, if the incident angle is equal to or greater than a critical angle, the light is totally transmitted without being transmitted. However, at this time, evanescent light oozes out in a very small region near the boundary surface. If there is a next medium in the light arrival region, the light is transmitted. This phenomenon is attenuated total reflection (ATR). By utilizing the interference between the light beams of the ATR, a high reflectance is obtained in a wide angle range and wavelength range. On the other hand, the thickness of the L layer made of a one-dimensional grating in the grating direction P is 370 nm, and this number is for effectively utilizing reflection by ATR.

  When this film thickness is reduced, transmission by ATR increases in the incident angle region above the critical angle, and sufficient reflection cannot be obtained.

  On the other hand, from the viewpoint of ATR, the thicker the film thickness, the better. However, even if the film thickness is increased, the reflectance becomes asymptotic to total reflection, so that the effect of simply increasing the film thickness cannot be obtained. With this one-dimensional lattice shape, the manufacturing difficulty increases as the film thickness increases. For this reason, it is preferable to set the thickness to about the thickness of the embodiment.

  Further, the range of the use angle includes normal reflection below the critical angle, but in the interference there, the optimum result was obtained by setting the thickness in the example.

In Example 1, as shown in Table 1, a relatively low refractive index of about 1.603 was used for the glass material of the prism. The dielectrics of the H layer, which is a one-dimensional lattice in the lattice direction V, and the L layer, which is a one-dimensional lattice in the lattice direction P, are both TiO ₂ , and a high refractive index material having a refractive index of 2.282 is used for filling. Birefringence is efficiently generated by setting the factors to L layer = 0.18 and H layer = 0.84.

  Regarding the layer of the one-dimensional grating in the grating direction V, the P-polarized light is TM and the S-polarized light is TE. For the one-dimensional lattice layer in the lattice direction P, P-polarized light is TE and S-polarized light is TM.

In the expressions (1) and (2), a graph showing effective refractive indexes for respective polarized light when one medium is TiO ₂ and the other is air and the filling factor f (the ratio of TiO _{2 to} the pitch) is changed. Is as shown in FIG.

  For P-polarized light, as shown in Table 1, when the first one-dimensional grating is f = 0.18, the effective refractive index in the TE direction is 1.35, and for the second one-dimensional grating, f = 0.84. The effective refractive index in the TM direction is 1.83.

  For one S-polarized light, the effective refractive index in the TM direction is 1.07 in the first one-dimensional grating as shown in Table 1, and the effective refractive index in the TE direction is 2.18 in the second one-dimensional grating.

  Thus, the effective refractive indexes of the first and second one-dimensional grating layers are close to each other with respect to the P-polarized light, and a large refractive index difference is generated with respect to the S-polarized light. Reflection is realized.

  The prism shape is shown in FIG. A shape in which the L-layer grating (101, 103) is sandwiched between the incident-side prism (22) and the emission-side prism (24) in the inclined direction as shown in FIG. It is.

  FIG. 11 shows the incident light flux. As shown in FIG. 11, the light incident on this prism has a circular opening centered on the optical axis (32) that forms 45 ° on the surface of the polarizing element, and is approximately Fno. Incident as 2.0 luminous flux (31). In this case, when the plane including the periodic direction of the grating in the P direction and the optical axis (32) as shown in FIG. 13 is a cross section (33), the angle of the incident light beam in the cross section (33) is as shown in FIG. It has a width of θ3 with respect to the optical axis.

  Further, when the plane including the periodic direction of the grating in the V direction and the optical axis (32) as shown in FIG. 15 is a cross section (34), the angle of the incident light beam in the cross section (34) is shown in FIG. As shown, the angle of the light beam with the optical axis tilted by θ0 and the maximum incident angle is θ3.

  It is necessary to prevent the incidence angle in each cross section and the grating pitch from causing diffraction. In the cross section of FIG. 14, the incident angle θ0 with respect to the grating of the optical axis is 0 °, and the light beam with the maximum incident angle is θ3 = about 14.5 ° of Fno2.0.

Here, in the above-mentioned diffraction conditional expression (5),
sin θ1−sin θ2 = mλ / dn (5)
The incident angle θ1 of the incident light is in the following range (9), and sin θ1 is in the following range (10).
−14.5 ≦ θ1 ≦ 14.5 (9)
−0.25 ≦ sin θ1 ≦ 0.25 (10)
When θ2 is arbitrary, possible values of the left side of Equation (6) are as follows.
−1.25 ≦ left side ≦ 1.25 (11)
Therefore, when the following condition is satisfied, Equation (5) has no solution other than m = 0.
1.25 <λ / dn (12)
That is, no diffraction occurs when the grating pitch d satisfies the following conditional expression (13).
d <λ / 1.25n (13)
Of the wavelengths used, the shortest wavelength λ = 430 nm and the refractive index n = 1.603 of the prism are substituted as follows.
d <215 [nm] (14)
The lattice pitch shown in the cross-sectional view of FIG. 14, that is, the lattice pitch of the L layer, is 200 nm as shown in Table 1, which is a value that substantially satisfies the above conditions.

On the other hand, in the cross section of FIG. 16, the incident angle of the optical axis with respect to the grating is θ0 = 45 °, and the angle of the light beam with the maximum incident angle is θ3 = 59.5 °. Using the expression (5) in the same manner as described above, the value that can be taken by the left side of the expression (5) is in the range of the expression (15), and when the grating pitch d satisfies the following conditional expression (16), the diffraction is Does not occur.
-1.87 ≦ left side ≦ 1.87 (15)
d <λ / 1.87n (16)
Of the wavelengths used, the shortest wavelength λ = 430 nm and the refractive index n = 1.603 of the prism are substituted as follows.
d <143 [nm] (17)
The lattice pitch shown in the cross-sectional view of FIG. 16, that is, the lattice pitch of the H layer is 140 nm as shown in Table 1, which is a value that substantially satisfies the above conditions.

  Regarding the incident angle θ0 of the optical axis and the incident angle θ3 of the maximum light beam, the maximum direction is because the incident plane is the V direction. The pitch of the L layer lattice (101, 103) is PB, and the pitch of the H layer lattice (102) is PA. This is a value satisfying conditional expression (8) as shown in Table 3.

  As shown in Table 1, the pitch of the L-layer grating is larger, but in the L-layer grating, the medium width ratio is small and the layer is thick, so the aspect ratio (ratio of the grating thickness to the grating width) Although it is larger, increasing the pitch as much as possible reduces the aspect ratio and reduces manufacturing difficulty.

  FIGS. 26A to 26C show the simulation results of the performance by the rigorous coupled-wave analysis (RCWA) of this design value. In the P-polarized light, the transmittance is lowered at a high incident angle, but it is at a level that causes almost no problem in consideration of the weight of the angle characteristics in actual use.

  With respect to S-polarized light, there is almost no light beam transmitted in a fairly wide incident angle range of 35 to 55 ° except that the performance is deteriorated on the short wavelength side with a low incident angle, and a complete reflectance is achieved.

  FIG. 7 shows the configuration of the polarization separation element of the second embodiment. FIG. 7 is a view of the lattice as viewed obliquely. 8 and 9 are sectional views as seen from the direction as shown in FIG. 2 as in the first embodiment.

  The first one-dimensional lattice is an H layer (201, 203, 205) in the lattice direction V in which air and a dielectric are alternately repeated. The second one-dimensional lattice is composed of L layers (202, 204) in the lattice direction P in which air and dielectric are alternately repeated.

  It is possible to achieve polarization separation with a relatively simple configuration of five layers as a whole. Moreover, TiO2 is used as the dielectric.

In Example 2, as shown in Table 2, a relatively low refractive index of about 1.603 was used for the glass material of the prism. The dielectrics of the H layer, which is a one-dimensional lattice in the lattice direction V, and the L layer, which is a one-dimensional lattice in the lattice direction P, are both TiO ₂ , and a high refractive index material having a refractive index of 2.282 is used for filling. Birefringence is efficiently generated by setting the factors to L layer = 0.30 and H layer = 0.90.

  Regarding P-polarized light, as shown in Table 2, when f = 0.30 in the first one-dimensional grating, the effective refractive index in the TE direction is 1.55, and when f = 0.90 in the second one-dimensional grating. The effective refractive index in the TM direction is 1.98.

  For one S-polarized light, the effective refractive index in the TM direction is 1.17 in the first one-dimensional grating as shown in Table 2, and the effective refractive index in the TE direction is 2.21 in the second one-dimensional grating.

  Thus, the effective refractive indexes of the first and second one-dimensional grating layers are close to each other with respect to the P-polarized light, and a large refractive index difference is generated with respect to the S-polarized light. Reflection is realized.

  The prism shape is shown in FIG. As shown in FIG. 10, the L-layer grating (202, 204) is between the incident-side prism (22) and the emission-side prism (24), and the H-layer grating (201, 203, 205) is orthogonal to the inclined direction as shown in FIG. It is a shape sandwiched between.

  The incident light flux is the same as that of the first embodiment and is shown in FIG.

  In FIGS. 14 and 16, it is necessary to prevent the incidence angle and the grating pitch at each of the cross sections (33) and (34) from causing diffraction, and the condition of the pitch of each grating at that time is similarly the above formula (14). (17).

  As shown in Table 2, the lattice pitch of the H layer is 120 nm, which satisfies the conditional expression (17). On the other hand, the lattice pitch of the L layer is 300 nm, which exceeds the conditional expression (14), but has been expanded to a range where there is no substantial problem in performance.

  Regarding the incident angle θ0 of the optical axis and the incident angle θ3 of the maximum light beam, the maximum direction is because the incident plane is the V direction. The pitch of the L-layer lattice (202, 204) is PB, and the pitch of the H-layer lattice (201, 203, 205) is PA, which is a value that satisfies the conditional expression (8) as shown in Table 3.

  As shown in Table 2, the pitch of the L-layer grating is larger, but in the L-layer grating, the medium width ratio is small and the layer is thick, so the aspect ratio (ratio of the grating thickness to the grating width) However, increasing the pitch as much as possible reduces the aspect ratio and reduces manufacturing difficulty.

  FIGS. 27A to 27C show performance simulation results based on the rigorous coupled-wave analysis (RCWA) of this design value. In the P-polarized light, the transmittance is somewhat lowered at a low incident angle, but almost the same performance is achieved in other cases.

  With respect to S-polarized light, there is almost no light beam transmitted in a fairly wide incident angle range of 35 to 55 ° except that the performance is deteriorated on the short wavelength side with a low incident angle, and a complete reflectance is achieved.

  FIG. 17 shows a polarizing element of Example 3. It is an element used in such a configuration that the incident angle is 0 °, such as a phase plate. As shown in the figure, the one-dimensional lattices (35) and (36) are stacked so as to be orthogonal to each other. FIG. 18 shows an incident light beam of Example 3. As shown in the figure, the optical axis (32) is incident at an incident angle of 0 °, and has a elliptical aperture centered on it. As shown in FIG. 19, the light beam in the cross section (37) including the major axis of the ellipse of the opening is as shown in FIG. Further, as shown in FIG. 20, the light flux in the cross section (38) including the minor axis of the ellipse of the opening is as shown in FIG.

The incident light flux in the cross section (37) shown in FIG. = 2.0 and θ4 = 14.5 °. Therefore, the lattice pitch in the cross-sectional direction needs to satisfy Expression (14) as in the first embodiment.
d <215 [nm] (14)
On the other hand, the incident light beam in the cross section (38) shown in FIG. = 4.0, and θ5 = 7.2 °. The lattice pitch in the cross-sectional direction is calculated in the same way as equation (18).
d <238 [nm] (18)
As shown in Table 3, since the pitch of each grating satisfies the conditional expressions (14) and (18), diffraction does not occur.

  In Example 3, the light beam whose cross-section (37) shown in FIG. 21 is the incident plane has the maximum incident angle. Therefore, the lattice pitch shown in this cross-sectional view is PA, and the lattice pitch orthogonal thereto is PB. As shown in Table 3, these values satisfy the conditional expression (8).

  FIG. 23 shows a fourth embodiment of the present invention. 1 shows a reflection type image modulation apparatus using a polarization separation element of the present invention. In the figure, 1 is a light source composed of a high-pressure mercury lamp, 2 is a reflector for emitting light from the light source 1 in a predetermined direction, and 3 is an integrator for forming an illumination area having uniform illumination intensity. It is composed of eye lenses 3a and 3b, 4 is a polarization conversion element that aligns non-polarized light in a predetermined polarization direction, 5 is a condenser lens that collects illumination light, 6 is a mirror, and 7 is illumination light. A field lens that makes telecentric light, 8 is a dichroic mirror that transmits light in the green wavelength region, and 9a1, 9b1, and 9c1 are polarization separation layers, respectively. , 9b, 9c are the polarization separation prisms of Examples 1 and 2 having the polarization separation layers 9a1, 9b1, 9c1. The optical axis (32) shown in FIG. 11 and the optical axis of the projection lens (14) on the exit side are optically aligned, and the grating pitch of the polarization separating element at that time is the same as that of the first and second embodiments. As a result, the conditional expression (1) is satisfied. 10a and 10b are color selective phase difference plates that respectively convert (rotate) the polarization direction of light in a predetermined wavelength region by 90 °, and 11r, 11g, and 11b each reflect incident illumination light and modulate it according to an image signal. A reflective liquid crystal display element 14 for forming image light and 14 is a projection lens system. When the polarization separation elements of the first and second embodiments are arranged as described above, since the incident angle characteristics and wavelength characteristics are excellent, it is possible to realize a reflection type liquid crystal projector with extremely high contrast obtained in the entire optical system.

Configuration diagram of polarization separation element corresponding to the first embodiment of the present invention The schematic diagram explaining the direction of the polarization separation element corresponding to 1st, 2nd Example of this invention Schematic diagram explaining diffraction by grating The perspective view of the grating | lattice shape of the polarization splitting element corresponding to 1st Example of this invention Sectional view of the grating from the direction A of the grating shape of the polarization beam splitter corresponding to the first embodiment of the present invention Sectional view of grating from direction B of the grating shape of the polarization beam splitter corresponding to the first embodiment of the present invention The perspective view of the grating | lattice shape of the polarization splitting element corresponding to 2nd Example of this invention Sectional view of grating from direction A of grating shape of polarization separation element corresponding to second embodiment of the present invention Sectional view of grating from direction B of grating shape of polarization separation element corresponding to second embodiment of the present invention Configuration diagram of a polarization beam splitting element prism corresponding to the first embodiment of the present invention The schematic diagram which shows the incident light beam to the polarization splitting element prism corresponding to 1st, 2nd Example of this invention Configuration diagram of polarization splitting element prism corresponding to the second embodiment of the present invention The schematic diagram which shows the incident light beam to the polarization splitting element prism corresponding to 1st, 2nd Example of this invention The schematic diagram which shows the incident light beam to the polarization splitting element prism corresponding to 1st, 2nd Example of this invention The schematic diagram which shows the incident light beam to the polarization splitting element prism corresponding to 1st, 2nd Example of this invention The schematic diagram which shows the incident light beam to the polarization splitting element prism corresponding to 1st, 2nd Example of this invention Configuration diagram of phase element corresponding to third embodiment of the present invention The schematic diagram which shows the incident light beam to the phase element corresponding to 3rd Example of this invention The schematic diagram which shows the incident light beam to the phase element corresponding to 3rd Example of this invention The schematic diagram which shows the incident light beam to the phase element corresponding to 3rd Example of this invention The schematic diagram which shows the incident light beam to the phase element corresponding to 3rd Example of this invention The schematic diagram which shows the incident light beam to the phase element corresponding to 3rd Example of this invention Configuration diagram in which a polarization separation element corresponding to the fourth embodiment of the present invention is incorporated in a reflection type liquid crystal projector optical system The figure explaining the model of the effective refractive index of a one-dimensional type SWS grating Graph showing structural birefringence when TiO2 is used for a one-dimensional SWS lattice The graph (a) showing the polarization separation characteristic in the visible light region of the polarization separation element corresponding to the first embodiment in the visible light region is incident angle 35.0 ° (b) is incident angle 45.0 ° (c) is incident Wavelength characteristics of transmittance of each polarized light at an angle of 55.0 ° The graph (a) showing the polarization separation characteristic in the visible light region by the RCWA calculation of the polarization separation element corresponding to the second embodiment is incident angle 35.0 ° (b) is incident angle 45.0 ° (c) is incident. Wavelength characteristics of transmittance of each polarized light at an angle of 55.0 °

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source which consists of high pressure mercury lamps etc. 2 Reflector 3 Integrator 3a, 3b Fly eye lens 4 Polarization conversion element 5 Condenser lens 6 Mirror 7 Field lens 8 Dichroic mirror 9a, 9b, 9c1 Polarization separation prism 9a1, 9b1, 9c1 Polarization separation layer 10a 10b Color selective phase difference plate 11r, 11g, 11b Reflective type liquid crystal display element 14 Projection lens system 18 P polarized incident light 19 P polarized transmitted light 20 S polarized incident light 21 S polarized reflected light 22 Incident side prism 23 Polarized light separating layer 24 exit-side prism 25 incident surface 26 exit surface of S-polarized reflected light 27 exit surface of P-polarized transmitted light 28 incident plane 29 arrow indicating lattice section observation direction A 30 arrow indicating lattice section observation direction B 31 incident light beam 32 incident light beam Optical axis 33 Horizontal including the optical axis of the incident light beam Surface 34 Longitudinal section including optical axis of incident light beam 35 Grating constituting phase plate 36 Grating constituting phase plate 37 Cross section including optical axis of incident light beam and major axis of aperture 38 Optical axis of incident luminous flux and minor axis of aperture Cross section including

Claims (4)

A layer having a refractive index periodic structure with a period equal to or less than a use wavelength in a first period direction parallel to a predetermined plane, and a use wavelength or less in a second period direction parallel to the predetermined plane and perpendicular to the first period direction A polarizing element in which both sides of a polarization separation layer laminated with a layer having a refractive index periodic structure with a period of is laminated in a direction perpendicular to the predetermined plane,
The absolute value of the photoelastic constant of the prism is smaller than 1.0 × 10 −8 cm 2 / N,
The polarization separation layer is inclined by 45 ° with respect to the incident surface of the incident side prism of the two prisms,
Of the first periodic direction and the second periodic direction, the period in the periodic direction that is nearly parallel to the incident plane of the light beam having the maximum incident angle among the light beams incident on the polarizing element is PA, and orthogonal to it. A polarizing element characterized by satisfying the following conditional expression when the period in the periodic direction is PB.
PA <PB A layer having a refractive index periodic structure with a period equal to or less than a use wavelength in a first period direction parallel to a predetermined plane, and a use wavelength or less in a second period direction parallel to the predetermined plane and perpendicular to the first period direction A polarizing element in which both sides of a polarization separation layer laminated with a layer having a refractive index periodic structure with a period of is laminated in a direction perpendicular to the predetermined plane,
The absolute value of the photoelastic constant of the prism is smaller than 1.0 × 10 −8 cm 2 / N,
The polarization separation layer is inclined by 45 ° with respect to the incident surface of the incident side prism of the two prisms,
When the central light beam of the light beam incident on the polarizing element is a representative light beam,
Of the first periodic direction and the second periodic direction, the period in the periodic direction that is nearly parallel to the incident plane when the representative light beam is incident on the polarizing element is PA, and the period in the periodic direction orthogonal thereto. A polarizing element characterized by satisfying the following conditional expression when PB is PB.
PA <PB A layer having a refractive index periodic structure with a period equal to or less than a use wavelength in a first period direction parallel to a predetermined plane, and a use wavelength or less in a second period direction parallel to the predetermined plane and perpendicular to the first period direction A polarizing element in which both sides of a polarization separation layer laminated with a layer having a refractive index periodic structure with a period of is laminated in a direction perpendicular to the predetermined plane,
The absolute value of the photoelastic constant of the prism is smaller than 1.0 × 10 −8 cm 2 / N,
The polarization separation layer is inclined by 45 ° with respect to the incident surface of the incident side prism of the two prisms,
When the light beam passing through the optical axis of the exit side prism among the two prisms placed on the exit side of the light beam exiting from the polarizing element is a representative light beam,
Of the first periodic direction and the second periodic direction, the period in the periodic direction that is nearly parallel to the incident plane when the representative light beam is incident on the polarizing element is PA, and the period in the periodic direction orthogonal thereto. A polarizing element characterized by satisfying the following conditional expression when PB is PB.
PA <PB   The polarizing element according to any one of claims 1 to 3, wherein the light beam from the light source unit is guided to a modulation unit that modulates based on an image signal, and the light beam modulated by the modulation unit is projected optically. A projection display device, wherein the projection is performed on a predetermined plane by a system.

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