Projection lens system and image projection device

Abstract

To achieve a novel projection lens system that can satisfactorily correct coma aberration, while satisfactorily maintaining aberrations other than the coma aberration for a display surface and a projection target surface non-parallel to each other.SOLUTION: A projection lens system arranges a front group and a rear group in order from a projection target surface side toward a display surface side, and has an aperture diaphragm closer to the display surface SF than the front group G1, and a front group optical axis being an optical axis of the front group and a rear group optical axis being an optical axis of the rear group G2 and parallel to the front group optical axis are shifted relative to each other with a shift amount Δ in a direction orthogonal to these optical axes. The front group optical axis and the rear group optical axis are located in a shared plane that is shared by a display surface normal line erected on the display surface SF and a projection target surface normal line erected on the projection target surface to intersect with the display surface normal line. The rear group optical axis is tilted with respect to the display surface normal line at a tilt angle of ξ in the shared plane. In a state where the shift amount Δ is 0, a tilt angle ξs when a shine-proof condition is satisfied for the display surface and the projection target surface and the tilt angle ξ satisfy the conditional expression (1): 0<ξ / ξs<1.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a projection lens system and an image projection device. [Background technology]

[0002] Image projection devices that project an image displayed on the display surface of an image display element such as a DMD (Digital Mirror Device), a liquid crystal panel, or a light-emitting element array as a projection image onto a projection surface such as a screen via a projection lens system have traditionally been known and implemented as various types of projectors. Recently, a HUD (head-up display) has also been put into practical use in which an image projection device such as that described above is mounted on a moving object such as a vehicle, and the image displayed on the screen is focused as a virtual image using a concave mirror or the like, allowing the virtual image to be observed.

[0003] In projectors and HUDs, the display surface of the image display element and the projection surface are often not parallel to each other. When the display surface and the projection surface are not parallel to each other, the so-called "Scheimpflug condition" is known as an optical condition for obtaining a projection image that is well focused on the projection surface (Patent Document 1, etc.). The "Scheimpflug condition" is a condition that the principal surface of the projection lens system, the display surface, and the projected surface intersect so as to share a single straight line. Note that while there are "entrance side principal surface and exit side principal surface" in the principal surfaces of a projection lens system, the principal surface referred to in the Scheimpflug condition is the "entrance side principal surface (the principal surface on the display surface side)." If the angle between the principal plane of the projection lens system and the display surface is "θA", the angle between the principal plane and the projected surface is "θB", and the object distance on the optical axis of the projection lens system is "a" and the image distance is "b", then the Scheimpflug condition requires that there is a distance between them as follows: a / tanθA=b / tanθB The relationship holds. In this case, the imaging magnification m on the optical axis is "b / a", or "tan θB / tan θA". Therefore, if the inclination angle θB of the screen relative to the principal plane of the projection lens system is given as a design condition, the inclination angle θA of the display surface relative to the principal plane is given as follows: tanθA=(tanθB) / m from, θA=arctan{(tanθB) / m)} is given by:

[0004] In this way, the angle that the optical axis of the projection lens system makes with the display surface and the projected surface can be determined.

[0005] As described above, by satisfying the Scheimpflug condition, it is possible to obtain a focused projected image on a projection surface that is not parallel to the display surface.

[0006] The inventors have discovered that when the inclination angle of the optical axis of the projection lens system relative to the display surface is slightly changed from the Scheimpflug condition, the coma aberration in the projected image deteriorates significantly, but the spherical aberration and astigmatism obtain characteristics that are roughly equivalent to those obtained when the Scheimpflug condition is exactly satisfied. Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above circumstances, an object of the present invention is to realize a new projection lens system that can effectively correct coma aberration while maintaining various aberrations other than coma aberration in a good condition for a display surface and a projection surface that are not parallel to each other. [Means for solving the problem]

[0008] The projection lens system of the present invention projects an image displayed on a display surface of an image display element as a projection image onto a projection surface tilted with respect to the display surface, and includes a front group and a rear group arranged in this order from the projection surface side to the display surface side, an aperture stop is provided on the display surface side of the front group, and a front group optical axis, which is the optical axis of the front group, and a rear group optical axis, which is the optical axis of the rear group and is parallel to the front group optical axis, are relatively shifted in a direction perpendicular to these optical axes by a shift amount: Δ. the front group optical axis and the rear group optical axis are located within a common plane shared by a display surface normal erected on the display surface and a projection surface normal erected on the projection surface so as to intersect with the display surface normal, the rear group optical axis is tilted at a tilt angle ξ with respect to the display surface normal within the common plane, and when the shift amount Δ is set to 0, the tilt angle ξs and the tilt angle ξ satisfy the Scheimpflug condition with respect to the display surface and the projection surface, and (1) 0 < ξ / ξs < 1 Satisfied the aperture stop is disposed between the front group and the rear group, and is independently shifted in the shared plane in a direction perpendicular to the optical axis of the rear group. . Effect of the Invention

[0009] According to the present invention, it is possible to realize a novel projection lens system that can effectively correct coma aberration while maintaining various aberrations other than coma aberration in a favorable manner for a display surface and a projection surface that are not parallel to each other. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing a lens configuration of a projection lens system according to a first embodiment. [Diagram 2] FIG. 4 is a diagram showing data of the projection lens system of Example 1. [Diagram 3] FIG. 4 is a diagram showing spherical aberration and astigmatism of the lens systems of Example 1 and Comparative Example. [Figure 4] FIG. 4 is a lateral aberration diagram of the first embodiment. [Diagram 5] 4 is a lateral aberration diagram of a comparative lens system of Example 1. FIG. [Figure 6] FIG. 11 is a diagram showing a lens configuration of a projection lens system according to a second embodiment. [Figure 7]FIG. 11 is a diagram showing data of a projection lens system according to a second embodiment. [Figure 8] FIG. 11 is a diagram showing spherical aberration and astigmatism of the lens systems of Example 2 and Comparative Example. [Figure 9] FIG. 11 is a lateral aberration diagram of the second embodiment. [Figure 10] 10A to 10C are lateral aberration diagrams of a comparative lens system of Example 2. [Figure 11] FIG. 11 is a diagram showing a lens configuration of a projection lens system according to a third embodiment. [Figure 12] FIG. 11 is a diagram showing data of the projection lens system of Example 3. [Figure 13] FIG. 11 is a diagram showing spherical aberration and astigmatism of the lens systems of Example 3 and Comparative Example. [Figure 14] FIG. 11 is a lateral aberration diagram of Example 3. [Figure 15] 11A to 11C are lateral aberration diagrams of a comparative lens system of Example 3. [Figure 16] FIG. 13 is a diagram showing a lens configuration of a projection lens system according to a fourth embodiment. [Figure 17] FIG. 13 is a diagram showing data of the projection lens system of Example 4. [Figure 18] FIG. 13 is a diagram showing spherical aberration and astigmatism of the lens systems of Example 4 and Comparative Example. [Figure 19] FIG. 13 is a lateral aberration diagram of Example 4. [Figure 20] 13A to 13C are lateral aberration diagrams of a comparative lens system of Example 4. [Figure 21] FIG. 13 is a diagram showing a lens configuration of a projection lens system according to a fifth embodiment. [Figure 22] FIG. 13 is a diagram showing data of the projection lens system of Example 5. [Figure 23] FIG. 13 is a diagram showing spherical aberration and astigmatism of the lens systems of Example 5 and Comparative Example. [Figure 24] FIG. 13 is a lateral aberration diagram of Example 5. [Diagram 25] 13A to 13C are lateral aberration diagrams of a comparative lens system of Example 5. [Figure 26] FIG. 13 is a diagram showing a lens configuration of a projection lens system according to a sixth embodiment. [Figure 27] FIG. 13 is a diagram showing data of the projection lens system of Example 6. [Figure 28] FIG. 13 is a diagram showing spherical aberration and astigmatism of the lens systems of Example 6 and Comparative Example. [Figure 29] FIG. 13 is a lateral aberration diagram of Example 6. [Diagram 30] 13 is a lateral aberration diagram of a comparative lens system of Example 6. FIG. [Diagram 31] FIG. 1 shows optical data for Examples 1 to 6. [Diagram 32] FIG. 1 is a diagram for explaining tilt and shift. [Diagram 33] FIG. 1 is a diagram illustrating an embodiment of a projection optical device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] As described above, the inventors have newly discovered that in a projection lens system in which the front group and the rear group are arranged in order from the projection surface side to the display surface side, which are not parallel to each other, and the aperture stop is located "on the display surface side of the front group," when the optical axis of the front group is the "front group optical axis" and the optical axis of the rear group is the "rear group optical axis," it is possible to effectively improve "deterioration of coma aberration" by shifting these front group optical axis and rear group optical axis relatively to each other in a direction perpendicular to these optical axes while keeping them parallel to each other. The relative shift amount between the front group optical axis and the rear group optical axis is designated as shift amount: Δ. The front group optical axis and the rear group optical axis are shifted from each other, but are parallel to each other. The optical axis of the rear group is tilted at a tilt angle ξ with respect to the display surface. Since the optical axis of the front group is parallel to the optical axis of the rear group, the optical axis of the front group is also tilted at a tilt angle ξ with respect to the display surface. The display surface and the projection surface are not parallel to each other, but the normal to these surfaces is considered, and the normal to the display surface is called the "display surface normal." Additionally, among the normals to the projection surface, the one that intersects with the display surface normal is called the "projection surface normal." The plane shared by these mutually intersecting display surface normals and projection surface normals (both the display surface normals and the projection surface normals lie within this plane) is called the "shared plane." The above-mentioned shifts and tilts of the front group optical axis and rear group optical axis are carried out within this shared plane.

[0012] Here, when the shift amount Δ is set to 0, there is no mutual shift between the front group optical axis and the rear group optical axis, and the front group optical axis and the rear group optical axis join together to form the same straight line. When the front group optical axis and the rear group optical axis form the same straight line in this way, the optical axis is called a "shared optical axis."

[0013] In this way, the tilt angle of the optical axis when the "lens system in which the front group optical axis and the rear group optical axis form a common optical axis" satisfies the Scheimpflug condition with respect to the display surface and the projection surface is defined as "ξs." The above tilt angles ξ and ξs are expressed by the following condition: (1) 0<ξ / ξs<1 Satisfy. In other words, in the "projection lens system of the present invention" in which the front group optical axis and the rear group optical axis are shifted from each other, the tilt amount of the rear group optical axis: ξ is smaller than the "tilt amount: ξs that satisfies the Scheimpflug condition when the shift amount: 0."

[0014] As described above, the projection lens system of the present invention has an aperture stop on the display surface side of the front group, but the aperture stop may be located between the front and rear groups or within the rear group. "An aperture diaphragm located between the front and rear groups" separates the front and rear groups. When the aperture diaphragm is located within the rear group, one or more of the lenses that make up the rear group will be located on the front group side of the aperture diaphragm.

[0015] When the image display element is a DMD, the display surface is a plane that is a collection of tiny mirror surfaces (hereinafter referred to as "micromirror surfaces"), and by tilting the micromirror surfaces that make up the display image, image light (a light beam that enters the projection lens system and forms a projected image) is formed by "reflected light from the tilted micromirror surfaces." In this case, depending on the inclination angle between the display surface and the projection surface, the inclination required for the micromirror surface may "exceed the inclination angle possible for the micromirror surface." In such a case, it is possible to satisfy the Scheimpflug condition by inclining the display surface itself to set a bias angle with respect to the inclination angle of the micromirror surface. However, in this case, a part of the reflected light (called "flat light") from the display surface of the illumination light irradiated on the display surface of the DMD may enter the projection lens system and interfere with the "image light from the micromirror surface inclined according to the display image," degrading the contrast of the projected image projected on the projection surface. In addition, if a bias angle is given, the orientation of the projection surface must also be adjusted in order to satisfy the Scheimpflug condition, which may cause layout problems.

[0016] By using the projection lens system of the present invention, the bias angle can be set to 0, thereby preventing a part of the flat light from interfering with the image light.

[0017] The aperture stop can be shifted independently (from the shift of the front and rear groups) in the direction perpendicular to the rear group optical axis (which is also perpendicular to the front group optical axis) within the "shared plane". By shifting the aperture stop in this way, it is possible to effectively compensate for the "deterioration in the F-number" caused by the shift / tilt of the front group optical axis and the rear group optical axis.

[0018] As described above, the projection lens system of the present invention has a two-group configuration, consisting of a front group and a rear group, but the refractive powers of these front and rear groups can be set to any positive or negative value as long as the "condition that the refractive power of all groups be positive" is satisfied. In other words, the possible combinations of refractive powers of the front and rear groups are "positive-positive, positive-negative, negative-positive." Of these, the most preferable combination is one in which the refractive power of the front group is positive or negative, and the refractive power of the rear group is positive.

[0019] The projection lens system of this invention is "a projection lens system that projects an image displayed on the display surface of an image display element as a projection image onto a projection surface that is tilted with respect to the display surface," so its design condition is premised on the display surface and projection surface being non-parallel to each other.

[0020] When designing, it is necessary to specify the positional relationship between the projection lens system and the display surface or the projected surface. This positional relationship is set with respect to the "projected surface and display surface." Now, shift and tilt will be described with reference to FIG. 32 is an explanatory diagram, in which the projection surface (screen) is indicated by the symbol SC, and the display surface is indicated by the symbol SF. A straight line SL connecting the center of the projection surface SR and the center of the display surface SF is called a "reference line."

[0021] Moreover, the reference character G1 denotes the front group, and the reference character G2 denotes the rear group. 32(a) is referred to as the “non-shifted state.” In the non-shifted state, the optical axes of the front group G1 and the rear group G2 are not shifted from each other, and these optical axes coincide with each other to form a “common optical axis” and coincide with the reference line SL. Fig. 32(b) shows the state in which the common optical axis AXC has been rotated counterclockwise from the non-shifted state, and this state is called the "tilt reference state." The rotation of the common optical axis AXC from the non-shifted state to the tilt reference state is performed with the intersection point P0 with the reference line SL of the lens LN1 "closest to the projection surface SC" of the front group G1 as the "center of rotation." "ξ" is the tilt angle.

[0022] 32(c) shows a state in which the front group G1 has shifted downward in the direction perpendicular to the rear group optical axis from the tilt reference state. The magnitude of this shift is taken as "shift amount: Δ". The shift direction of the front group G1 in FIG. 32(c) is not limited to "downward" and can also be "upward." Fig. 32(d) shows a state in which the rear group G2 is shifted downward in a direction perpendicular to the optical axis of the front group G1 from the tilt reference state in Fig. 32(b). In this case as well, the shift amount of the rear group G2 is "shift amount: Δ". The shift direction of the rear group G2 in FIG. 32(d) is not limited to "downward" and can also be "upward."

[0023] FIG. 32(e) shows a state in which the front group G1 and rear group G2 have been shifted together from the state shown in FIG. 32(c) to the upper part of the drawing. The direction of the "integral shift" of front group G1 and rear group G2 in Figure 32(e) is not limited to "upward" but can also be "downward."

[0024] As shown in FIG. 32(c), the case in which the front group G1 is shifted from the tilt reference state (FIG. 32(b)) is referred to as the "first case." As shown in FIG. 32(d), the case in which the rear group G2 is shifted from the tilt reference state (FIG. 32(b)) is referred to as the "second case." Furthermore, as in the first and second cases, from a state in which the front group G1 or the rear group G2 has shifted (Figures 32(c) and (d)), Figure 32(e) shows a state in which the front group G1 and the rear group G2 as a whole have shifted in a direction perpendicular to the front group optical axis while maintaining the tilt angle: ξ and shift amount: Δ. This case is called the "third case". The overall shift direction is also not limited to the upward direction in Figure 32(e), and can also be downward.

[0025] In the first or third case, when the front group optical axis shifts with respect to the rear group optical axis by a shift amount of the front group optical axis: Δ1, the focal length of the front group: f1, the shift amount of the front group optical axis: Δ1, and the focal length of the entire group: f satisfy the conditional formula: (2) 0.000047( / mm)<|Δ1 / f1| / f<0.001( / mm) It is preferable to satisfy the following: In the second or third case, when the rear group optical axis shifts with respect to the front group optical axis by a rear group optical axis shift amount: Δ2, the focal length of the rear group: f2, the rear group optical axis shift amount: Δ2, and the focal length of the entire group: f satisfy the conditional formula: (3) 0.000047( / mm)<|Δ2 / f2| / f<0.001( / mm) It is preferable to satisfy the following: The above conditional expressions (2) and (3) both relate to the correction of coma, and in either case, if the lower limit is exceeded, then "insufficient correction of coma" due to the shift of the shifting group is likely to occur, and if the upper limit is exceeded, then conversely, "excessive correction of coma" is likely to occur.

[0026] The lower limits of the conditional expressions (2) and (3) are preferably 0.00007, more preferably 0.0001, and the upper limits are preferably 0.0007, more preferably 0.0005. All the values ​​are expressed in units of "( / mm)".

[0027] In the projection lens system of the present invention, one or more lenses can be aspheric lenses. The use of aspheric lenses can improve performance. The aspheric lenses can be configured as "glass molded lenses" or "plastic lenses." If two or more lenses are aspheric lenses, some of them can be "glass molded lenses" and the rest can be "plastic lenses." "Glass molded lenses" are less susceptible to environmental fluctuations such as temperature and humidity, and plastic lenses can be "manufactured at low cost." Of course, all the lenses in the projection lens system may be made of glass lenses, or may be made of plastic lenses, or may be made of a mixture of glass lenses and plastic lenses.

[0028] The "projection lens system" described above can be used as the projection lens system of "an image projection device that projects, by the projection lens system, an image displayed on the display surface of an image display element as a projection image onto a projection surface tilted in one direction relative to the display surface."

[0029] In such an image projection device, "DMD (Digital Mirror Device), LCD panel, light-emitting element array, etc." can be used as the image display element, and when a DMD is used as the image display element, a "prism that guides illumination light to the display surface of the DMD" can be provided between the DMD and the rear group. In this case, the "object light incident surface facing the display surface" of the prism can be arranged to face the display surface in parallel. Alternatively, the normal to the display surface may be tilted relative to the object light incidence surface of the prism within the common plane. In this way, part of the tilt angle ξ of the rear group optical axis of the projection lens system can be borne by the tilt of the display surface, making it possible to relax the design requirements for the projection lens system.

[0030] The image projection device of the present invention can, of course, be configured as a projector device, but it can also be configured as a HUD (head-up display) in which the image projection device is mounted on a moving body such as a vehicle, and an image displayed on a screen is formed as a virtual image using a concave mirror or the like, and the virtual image can be observed.

[0031] Six specific examples of the projection lens system will be given below. "Example 1" The "configuration in a common plane" of the projection lens system of the first embodiment is shown in Fig. 1. In Fig. 1, the left side is the projection surface side, and the right side is the display surface side. The image display element is assumed to be a DMD, the display surface of which is a flat surface indicated by the symbol SF, and the symbol G indicates a cover glass that protects the display surface SF. This point is the same in the following Examples 2 to 6. Reference symbol G1 denotes a front group, reference symbol G2 denotes a rear group, reference symbol S denotes an aperture stop, and reference symbol Pr denotes a prism for guiding illumination light that is disposed between rear group G2 and display surface SF. The prism Pr has a rectangular parallelepiped shape, and the "object light incident surface facing the display surface SF" faces the display surface SF in parallel.

[0032] Front group G1 is made up of "four lenses arranged from the projection surface side to the display surface side: a biconvex lens, a positive meniscus lens, a negative meniscus lens, and a biconcave lens," and has "negative refractive power." The entire front group G1 shifts by an amount Δ in a direction perpendicular to the front group optical axis (downward in the illustration). 1, the amount of shift is indicated by the upward direction being positive (+) and the downward direction being negative (-). The same applies to the following examples.

[0033] The rear group G2 consists of "six lenses arranged from the projection surface side to the display surface side: a positive meniscus lens, a biconvex lens, a biconvex lens, a biconcave lens, a biconvex lens, and a biconvex lens" and has "positive refractive power." An aperture stop S is disposed between the front group G1 and the rear group G2, separating them. The shift amount of the front group G1 is Δ=-0.11 mm. The optical axis of the rear group G2 is tilted counterclockwise with respect to the display surface SF at a tilt angle of ξ=1.83 degrees, and the aperture stop S is shifted +0.66 mm toward the top of the drawing with respect to the rear group optical axis. Moreover, the entire projection lens system, with the front group G1 and the rear group G2 integrated, is shifted +0.032 mm upward in the drawing within the common plane. That is, Example 1 corresponds to the above-mentioned "third case."

[0034] The data from Example 1 are shown in FIG. FIG. 2 shows data from the projection surface to the display surface, going from top to bottom. In the diagram in Figure 2, "TYPE" in the left column indicates the type of optical surface (including the projection surface, aperture stop, prism surface, cover glass, and display surface), and "Sphere" means "spherical surface." Additionally, "R" is the radius of curvature of the optical surface, and "d" is the "surface spacing of adjacent optical surfaces." FIG. 3 shows the spherical aberration and astigmatism of the lens systems of Example 1 and Comparative Example. FIG. 3(a) is an aberration diagram of the first embodiment, and (b) is an aberration diagram of the comparative lens system. The "comparison lens system" is a lens system in which the "shift amount: Δ is 0" in the examples, and is a lens system in the "tilt standard state" previously described with reference to Figure 32(b). The same applies to the other examples below. In the "Comparative Example Lens System", the shift amount Δ is set to 0, so that the front group G1 and the rear group G2 have a common optical axis, and the tilt angle ξ is the same as that in the first embodiment. As is clear from the aberration diagram of Example 1 shown in FIG. 3(a) and the aberration diagram of the comparative lens system shown in (b), there is substantially no difference in performance regarding spherical aberration and astigmatism.

[0035] FIGS. 4(a) and (b) show lateral aberration diagrams relating to Example 1, and FIGS. 5(a) and (b) show lateral aberration diagrams relating to the comparative example lens system.

[0036] As is clear from a comparison of the lateral aberration diagrams of FIG. 4 and FIG. 5, the projection lens system of Example 1 has effectively improved coma aberration compared to the comparative lens system. In the first embodiment, the tilt angle ξ of the optical axis of the rear group G2 relative to the display surface SF is 1.83 degrees, as described above. The "tilt angle: ξs at which the comparative lens system satisfies the Scheimpflug condition" is given by the above formula: θA=arctan{(tanθB) / m} In this case, the screen inclination angle: θB = 27 degrees, and the imaging magnification: m = 11.702, from which it follows that θA = ξs = 2.493 degrees. That is, the value of the parameter ξ / ξs in conditional formula (1) is 1.83 / 2.493=0.74 It is.

[0037] "Example 2" The "configuration in a common plane" of the projection lens system of the second embodiment is shown in Fig. 6 following Fig. 1. To avoid complication, the same symbols and signs as in Fig. 1 are used for those that are unlikely to be confused. The rectangular parallelepiped prism Pr has an "object light incident surface facing the display surface SF" and the display surface SF facing in parallel.

[0038] Front group G1 consists of "four lenses arranged from the projection surface to the display surface: a biconvex lens, a positive meniscus lens, a negative meniscus lens, and a biconcave lens," and has "negative refractive power." The entire front group G1 is shifted in a direction perpendicular to the front group optical axis (downward in the illustration) by an amount of shift Δ=-0.12 mm.

[0039] The rear group G2 "is made up of six lenses arranged from the projection surface side to the display surface side: a positive meniscus lens, a biconvex lens, a biconvex lens, a biconcave lens, a biconvex lens, and a biconvex lens," and "has positive refractive power. An aperture stop S is disposed between the front group G1 and the rear group G2, separating them. The optical axis of the rear group G2 is tilted counterclockwise with respect to the display surface SF at a tilt angle of ξ=2.01 degrees, and the aperture stop S is shifted +0.74 mm toward the top of the drawing with respect to the rear group optical axis. The second embodiment is also the above-mentioned "third case."

[0040] The data for Example 2 is shown in FIG. 7, which parallels FIG. FIG. 8 shows the spherical aberration and astigmatism of the lens systems of Example 2 and the comparative example. FIG. 8(a) is an aberration diagram of the second embodiment, and (b) is an aberration diagram of the comparative lens system. The amount of tilt of the common optical axis of the front group G1 and the rear group G2 of the "comparison lens system" is the same as the amount of tilt of the second embodiment. As is clear from the aberration diagram of Example 2 shown in FIG. 8(a) and the aberration diagram of the comparative lens system shown in (b), there is no substantial difference in performance regarding spherical aberration and astigmatism.

[0041] 9(a) and (b) show lateral aberration diagrams relating to Example 2, and FIGS. 10(a) and (b) show lateral aberration diagrams relating to the comparative lens system. As is clear from a comparison of the lateral aberration diagrams in FIG. 9 and FIG. 10, the projection lens system of Example 2 has effectively improved coma aberration compared to the comparative lens system. In the second embodiment, the tilt angle ξ of the optical axis of the rear group G2 relative to the display surface SF is 2.01 degrees, as described above. The "tilt angle: ξs at which the comparative lens system satisfies the Scheimpflug condition" is the screen inclination angle: θB = 27 degrees, and the imaging magnification: m = 10.969, from which θA = ξs = 2.660 degrees. That is, the value of the parameter ξ / ξs in conditional formula (1) is 2.01 / 2.660=0.76 It is.

[0042] "Example 3" FIG. 11 shows the “configuration in a common plane” of the projection lens system of the third embodiment. The rectangular parallelepiped prism Pr has an "object light incident surface facing the display surface SF" and the display surface SF facing in parallel.

[0043] Front group G1 consists of "three lenses: a biconvex lens, a positive meniscus lens, and a biconcave lens arranged from the projection surface to the display surface" and has "positive refractive power". The entire front group G1 is shifted in a direction perpendicular to the front group optical axis (upward in the illustration) by an amount of shift Δ=+1.46 mm.

[0044] The rear group G2 has positive refractive power and is composed of six lenses: a biconcave lens, a positive meniscus lens, a biconvex lens, a biconcave lens, a biconvex lens, and a biconvex lens, arranged from the projection surface to the display surface. The aperture stop S is placed between the biconcave lens and the positive meniscus lens. The optical axis of rear group G2 is tilted counterclockwise with respect to display surface SF at a tilt angle of ξ=3.00 degrees, and aperture stop S is shifted +1.28 mm toward the top of the drawing with respect to the rear group optical axis. Example 3 corresponds to the first case described above.

[0045] The data for Example 3 is shown in FIG. 12, which parallels FIG. FIG. 13 shows the spherical aberration and astigmatism of the lens systems of Example 3 and Comparative Example. FIG. 13(a) is an aberration diagram of the third embodiment, and (b) is an aberration diagram of the comparative lens system. The tilt amount of the “Comparative Example Lens System” is the same as that of the third embodiment. As is clear from the aberration diagram of Example 3 shown in FIG. 13(a) and the aberration diagram of the comparative lens system shown in (b), there is substantially no difference in performance regarding spherical aberration and astigmatism.

[0046] FIGS. 14(a) and (b) show lateral aberration diagrams relating to Example 3, and FIGS. 15(a) and (b) show lateral aberration diagrams relating to the comparative example lens system. As is clear from a comparison of the lateral aberration diagrams of FIG. 14 and FIG. 15, the projection lens system of Example 3 has effectively improved coma aberration compared to the comparative lens system. In the third embodiment, the tilt angle ξ of the optical axis of the rear group G2 relative to the display surface SF is 3.00 degrees, as described above. The "tilt angle: ξs at which the comparative example lens system satisfies the Scheimpflug condition" is the screen inclination angle: θB = 27 degrees, and the imaging magnification: m = 8.193, from which θA = ξs = 3.559 degrees. That is, the value of the parameter ξ / ξs in conditional formula (1) is 3.00 / 3.559=0.84 It is.

[0047] "Example 4" FIG. 16 shows the “configuration in a common plane” of the projection lens system of the fourth embodiment. The rectangular parallelepiped prism Pr has an "object light incident surface facing the display surface SF" and the display surface SF facing in parallel. Front group G1 consists of "three lenses: a positive meniscus lens, a positive meniscus lens, and a negative meniscus lens arranged from the projection surface side to the display surface side," and has "positive refractive power," and the entire front group G1 is shifted in a direction perpendicular to the front group optical axis (upward in the illustration) by an amount of shift Δ=+1.36 mm.

[0048] The rear group G2 has positive refractive power and is composed of six lenses: a biconcave lens, a positive meniscus lens, a biconvex lens, a biconcave lens, a positive meniscus lens, and a biconvex lens, arranged from the projection surface to the display surface. The aperture stop S is placed between the biconcave lens and the positive meniscus lens. The optical axis of the rear group G2 is tilted counterclockwise with respect to the display surface SF at a tilt angle of ξ=3.04 degrees, and the aperture stop S is shifted +1.35 mm toward the top of the drawing with respect to the rear group optical axis. Example 4 corresponds to the first case described above.

[0049] The data for Example 4 is shown in FIG. 17, which parallels FIG. An aspheric surface is used in Example 4. The data is shown in Figure 17(a) and the aspheric surface data is shown in Figure 17(b). The aspheric surface is expressed by the well-known formula: z is the aspheric amount, c is the paraxial curvature, r is the distance from the optical axis, k is the conic constant, and α1, α2, α3, and α4 are the 2nd, 4th, 6th, and 8th order aspheric coefficients. z=cr 2 / [1+√(1―(1+k)c 2 r 2 )] +α1·r 2 +α2·r 4 +α3·r 6 +α4·r 8 It is expressed as:

[0050] In the data shown in Figure 17(b), for example, "-4.547277E-06" means "-4.547277×10 -6 " means.

[0051] FIG. 18 shows the spherical aberration and astigmatism of the lens systems of Example 4 and Comparative Example. FIG. 18(a) is an aberration diagram of the fourth embodiment, and (b) is an aberration diagram of the comparative lens system. The "comparison lens system" has the same data as in the fourth embodiment, with the shift amount Δ of the front group G1 set to 0 and the tilt amount set to the same as that in the fourth embodiment.

[0052] As is clear from the aberration diagram of Example 4 shown in FIG. 18(a) and the aberration diagram of the comparative lens system shown in (b), there is substantially no difference in performance regarding spherical aberration and astigmatism.

[0053] FIGS. 19(a) and (b) show lateral aberration diagrams relating to Example 4, and FIGS. 20(a) and (b) show lateral aberration diagrams relating to the comparative example lens system. As is clear from a comparison of the lateral aberration diagrams in FIG. 19 and FIG. 20, the projection lens system of Example 4 has effectively improved coma aberration compared to the comparative lens system. In the fourth embodiment, the tilt angle ξ of the optical axis of the rear group G2 relative to the display surface SF is 3.04 degrees, as described above. The "tilt angle: ξs at which the comparative example lens system satisfies the Scheimpflug condition" is the screen inclination angle: θB = 27 degrees, and the imaging magnification: m = 8.221, from which θA = ξs = 3.547 degrees. That is, the value of the parameter ξ / ξs in conditional formula (1) is 3.04 / 3.547=0.86 It is.

[0054] "Example 5" FIG. 21 shows the “configuration in a common plane” of the projection lens system of the fifth embodiment. The rectangular parallelepiped prism Pr has an "object light incident surface facing the display surface SF" and the display surface SF facing in parallel.

[0055] Front group G1 consists of "three lenses: a positive meniscus lens, a positive meniscus lens, and a biconcave lens arranged from the projection surface side to the display surface side," and has "positive refractive power," and the entire front group G1 is shifted in a direction perpendicular to the front group optical axis (upward in the illustration) by an amount of shift Δ=+1.40 mm.

[0056] The rear group G2 has positive refractive power and is composed of six lenses: a biconcave lens, a biconvex lens, a biconvex lens, a biconcave lens, a biconvex lens, and a biconvex lens, arranged from the projection surface to the display surface. The aperture stop S is placed between the biconcave lens and the biconvex lens. The optical axis of the rear group G2 is tilted counterclockwise with respect to the display surface SF at a tilt angle of ξ=3.05 degrees, and the aperture stop S is shifted +1.48 mm toward the top of the drawing with respect to the rear group optical axis. The fifth embodiment also falls into the first category.

[0057] The data for Example 5 is shown in FIG. 22, similar to FIG. An aspheric surface is also used in Example 5, and the data is shown in FIG. 22(a) and the aspheric surface data is shown in FIG. 22(b). FIG. 23 shows the spherical aberration and astigmatism of the lens systems of Example 5 and the comparative example. FIG. 23(a) is an aberration diagram of the fifth embodiment, and (b) is an aberration diagram of the comparative lens system. As is clear from the aberration diagram of Example 5 shown in FIG. 23(a) and the aberration diagram of the comparative lens system shown in (b), there is substantially no difference in performance regarding spherical aberration and astigmatism.

[0058] FIGS. 24(a) and (b) show lateral aberration diagrams relating to Example 5, and FIGS. 25(a) and (b) show lateral aberration diagrams relating to the comparative example lens system. As is clear from a comparison of the lateral aberration diagrams in FIG. 24 and FIG. 25, the projection lens system of Example 5 has effectively improved coma aberration compared to the comparative lens system. In the fifth embodiment, the tilt angle ξ of the optical axis of the rear group G2 relative to the display surface SF is 3.05 degrees, as described above. The "tilt angle: ξs at which the comparative example lens system satisfies the Scheimpflug condition" is the screen inclination angle: θB = 27 degrees, and the imaging magnification: m = 8.219, from which θA = ξs = 3.548 degrees. That is, the value of the parameter ξ / ξs in conditional formula (1) is 3.05 / 3.548=0.86 It is.

[0059] "Example 6" FIG. 26 shows the “configuration in a common plane” of the projection lens system of the sixth embodiment. The rectangular parallelepiped prism Pr has an "object light incident surface facing the display surface SF" and the display surface SF facing in parallel.

[0060] The front group G1 consists of "four lenses arranged from the projection surface side to the display surface side: a biconvex lens, a positive meniscus lens, a biconcave lens, and a biconcave lens" and has "negative refractive power."

[0061] The rear group G2 has positive refractive power and is composed of five lenses: a positive meniscus lens, a biconvex lens, a biconcave lens, a biconvex lens, and a biconvex lens, arranged from the projection surface side to the display surface side. The aperture stop S is located between the front group G1 and the rear group G2. The entire rear group G2 is shifted by an amount of shift Δ=+0.13 mm in a direction perpendicular to the rear group optical axis (upward in the drawing).

[0062] The optical axis of the rear group G2 is tilted counterclockwise with respect to the display surface SF at a tilt angle of ξ=2.63 degrees, and the aperture stop S is shifted +1.45 mm toward the top of the drawing with respect to the rear group optical axis. Example 6 is the second case described above.

[0063] The data for Example 6 is shown in FIG. 27, parallel to FIG. FIG. 28 shows the spherical aberration and astigmatism of the lens systems of Example 6 and the comparative example. FIG. 28(a) is an aberration diagram of Example 6, and (b) is an aberration diagram of the comparative lens system. As is clear from the aberration diagram of Example 6 shown in FIG. 28(a) and the aberration diagram of the comparative lens system shown in (b), there is substantially no difference in performance regarding spherical aberration and astigmatism.

[0064] FIGS. 29(a) and (b) show lateral aberration diagrams relating to Example 6, and FIGS. 30(a) and (b) show lateral aberration diagrams relating to the comparative lens system. As is clear from a comparison of the lateral aberration diagrams in FIG. 29 and FIG. 30, the projection lens system of Example 6 has effectively improved coma aberration compared to the comparative lens system. In the sixth embodiment, the tilt angle ξ of the optical axis of the rear group G2 relative to the display surface SF is 3.05 degrees, as described above. The "tilt angle: ξs at which the comparative lens system satisfies the Scheimpflug condition" is the screen inclination angle: θB = 27 degrees, and the imaging magnification: m = 8.229, from which θA = ξs = 3.543 degrees. That is, the value of the parameter ξ / ξs in conditional formula (1) is 3.05 / 3.543=0.86 It is.

[0065] FIG. 31 shows the optical data for Examples 1 to 6 above. That is, Figure 31(a) shows the magnification (imaging magnification on the optical axis), focal length (focal length of the entire system: f), front group focal length: f1, rear group focal length: f2, and the tilt amount (projection tilt amount) of the front and rear groups relative to the display surface, while (b) shows the shift amount of the projection lens system as a whole (Examples 1 and 2), the front group shift amount, the rear group shift amount, and the parameter values ​​of conditional expressions (2) and (3).

[0066] As described above, the projection lens systems of Examples 1 to 6 have good performance with respect to the display surface SF and the projection surface that are not parallel to each other, with the coma aberration also being well corrected while maintaining various aberrations other than coma in a good condition.

[0067] One embodiment of the image projection device is shown in Fig. 33. Fig. 33 shows an example of the image projection device mounted on a moving object such as a vehicle to configure a HUD. In the figure, the portion designated by reference numeral 100 indicates a portion including "an image display element, a projection lens system, and an illumination optical system for illuminating the display surface of the image display element" in the image projection device. Reference numeral 80 denotes a "diffuse transparent screen" that forms the projection surface. The screen 80 is inclined with respect to the display surface of the image display element. The portion denoted by reference numeral 100 may be any of the above-described embodiments 1 to 6. An image (driving information, etc.) displayed on the display surface is projected as a projection image onto a screen 80 by a projection lens system. Light diffused by the screen 80 forms a virtual image 120 by a concave mirror 90, which is a virtual image forming element, and the imaging light flux by the concave mirror 90 is reflected by a windshield 1000 of the vehicle toward the driver's eye EY, so that the driver can view the virtual image 120 through the windshield 1000.

[0068] Although a preferred embodiment of the invention has been described above, the invention is not limited to the specific embodiment described above, and various modifications and variations are possible within the spirit of the invention described in the claims, unless otherwise specifically limited in the above description. The effects described in the embodiments of the present invention are merely a list of preferred effects resulting from the invention, and the effects of the invention are not limited to "those described in the embodiments." [Explanation of symbols]

[0069] G1 front group G2 rear group S aperture stop Pr Prism G Cover glass for the display surface of the DMD, which is an image display element SF display surface [Prior art documents] [Patent documents]

[0070] [Patent Document 1] JP 2007-163547 A

Claims

1. A projection lens system that projects an image displayed on a display surface of an image display element as a projection image onto a projection surface that is tilted with respect to the display surface, a front group and a rear group are arranged in this order from the projection surface side to the display surface side, an aperture stop is provided on the display surface side of the front group, a front group optical axis that is the optical axis of the front group and a rear group optical axis that is the optical axis of the rear group and is parallel to the front group optical axis are relatively shifted in a direction perpendicular to these optical axes by a shift amount: Δ, the front group optical axis and the rear group optical axis are located within a common plane shared by a display surface normal line erected on the display surface and a projection surface normal line erected on the projection surface so as to intersect with the display surface normal line, the rear group optical axis is tilted at a tilt angle ξ with respect to the display surface normal within the shared plane, In a state where the shift amount Δ is set to 0, the tilt angle ξs when the Scheimpflug condition is satisfied with respect to the display surface and the projection surface, and the tilt angle ξ is expressed by the conditional formula: (1) 0 <ξ / ξs< 1 Satisfied, The aperture stop is disposed between the front group and the rear group, and is independently shifted within the shared plane in a direction perpendicular to the optical axis of the rear group.

2. A projection lens system that projects an image displayed on a display surface of an image display element as a projection image onto a projection surface tilted relative to the display surface, a front group and a rear group are arranged in this order from the projection surface side to the display surface side, an aperture stop is provided on the display surface side of the front group, a front group optical axis that is the optical axis of the front group and a rear group optical axis that is the optical axis of the rear group and is parallel to the front group optical axis are relatively shifted in a direction perpendicular to these optical axes by a shift amount: Δ, the front group optical axis and the rear group optical axis are located within a common plane shared by a display surface normal line erected on the display surface and a projection surface normal line erected on the projection surface so as to intersect with the display surface normal line, the rear group optical axis is tilted at a tilt angle ξ with respect to the display surface normal within the shared plane, In a state where the shift amount Δ is set to 0, the tilt angle ξs when the Scheimpflug condition is satisfied with respect to the display surface and the projection surface, and the tilt angle ξ is expressed by the conditional formula: (1) 0 <ξ / ξs< 1 Satisfied, The aperture stop is disposed in the rear group and is independently shifted in the shared plane in a direction perpendicular to the rear group optical axis.

3. A projection lens system according to claim 1 or 2, a projection lens system in which the refractive power of the front group is positive or negative, and the refractive power of the rear group is positive.

4. A projection lens system according to any one of claims 1 to 3, A projection lens system in which a straight line connecting the center of the projection surface and the center of the display surface is used as a reference line, and from an unshifted state in which a common optical axis, in which the optical axes of the front and rear groups are aligned, is aligned with the reference line, the rear group optical axis is shifted in a direction perpendicular to the front group optical axis by a shift amount: Δ (≠ 0) with the intersection of the lens surface of the front group closest to the projection surface and the reference line as the center of rotation, relative to a tilt reference state in which the common optical axis is tilted at a tilt angle: ξ.

5. A projection lens system that projects an image displayed on a display surface of an image display element as a projection image onto a projection surface inclined with respect to the display surface, a front group and a rear group are arranged in this order from the projection surface side to the display surface side, an aperture stop is provided on the display surface side of the front group, a front group optical axis that is the optical axis of the front group and a rear group optical axis that is the optical axis of the rear group and is parallel to the front group optical axis are relatively shifted in a direction perpendicular to these optical axes by a shift amount: Δ, the front group optical axis and the rear group optical axis are located within a common plane shared by a display surface normal line erected on the display surface and a projection surface normal line erected on the projection surface so as to intersect with the display surface normal line, the rear group optical axis is tilted at a tilt angle ξ with respect to the display surface normal within the shared plane, In a state where the shift amount Δ is set to 0, the tilt angle ξs when the Scheimpflug condition is satisfied with respect to the display surface and the projection surface, and the tilt angle ξ is expressed by the conditional formula: (1) 0 <ξ / ξs< 1 Satisfied, A projection lens system in which a straight line connecting the center of the projection surface and the center of the display surface is used as a reference line, and from an unshifted state in which a common optical axis, in which the optical axes of the front and rear groups are aligned, is aligned with the reference line, the front group optical axis is shifted by a shift amount Δ (≠0) in a direction perpendicular to the rear group optical axis, relative to a tilt reference state in which the common optical axis is tilted at a tilt angle ξ, with the intersection point between the lens surface of the front group closest to the projection surface and the reference line as the center of rotation.

6. A projection lens according to claim 5, The aperture stop is disposed between the front group and the rear group.

7. A projection lens according to claim 5, A projection lens system in which the aperture stop is disposed in the rear group.

8. A projection lens system according to any one of claims 5 to 7, The projection lens system, wherein the aperture stop is independently shifted in a direction perpendicular to the rear group optical axis within the shared plane.

9. A projection lens system according to claim 5, further comprising: a projection lens system in which the refractive power of the front group is positive or negative, and the refractive power of the rear group is positive.

10. A projection lens system according to any one of claims 4 to 9, The projection lens system is shifted as a whole in a direction perpendicular to the front group optical axis while maintaining the tilt angle: ξ and the shift amount: Δ.

11. A projection lens system according to any one of claims 4 to 10, the front group optical axis is shifted with respect to the rear group optical axis by a front group optical axis shift amount: Δ1, The focal length of the front group: f1, the shift amount of the optical axis of the front group: Δ1, and the focal length of the entire group: f are expressed by the condition: (2) 0.000047( / mm)<|Δ1 / f1| / f<0.001( / mm) A projection lens system that satisfies the above.

12. A projection lens system according to any one of claims 4 to 10, the rear group optical axis is shifted with respect to the front group optical axis by a rear group optical axis shift amount: Δ2, The focal length of the rear group: f2, the shift amount of the optical axis of the rear group: Δ2, and the focal length of the entire group: f are expressed by the condition: (3) 0.000047( / mm)<|Δ2 / f2| / f<0.001( / mm) A projection lens system that satisfies the above.

13. A projection lens system according to any one of claims 1 to 12, A projection lens system in which one or more lenses are aspheric.

14. The projection lens system of claim 13, A projection lens system in which one or more of the aspheric lenses are formed as a glass molded lens or a plastic lens.

15. An image projection device that projects an image displayed on a display surface of an image display element as a projection image onto a projection surface tilted with respect to the display surface by a projection lens system, comprising:

15. An image projection device using the projection lens system according to claim 1 as said projection lens system.

16. The image projection device according to claim 15, The image display element is a DMD, and the image projection device has a prism between the DMD and the rear group that guides illumination light to the display surface of the DMD.

17. The image projection device of claim 16, an object light incidence surface of the prism facing the display surface faces the display surface in parallel to the object light incidence surface of the prism; 18. The image projection device according to claim 17, An image projection device, wherein a normal to the display surface is tilted relative to the object light incident surface of the prism within the shared plane.

19. An image projection device described in any one of claims 15 to 18, mounted on a moving body.

Images