JP2009229552A - Projection optical system and headup display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection optical system suitable for a headup display device which displays a bright and uniform virtual image even when it is viewed from any place within a predetermined range. <P>SOLUTION: The headup display device 10 is equipped with: a transmission type liquid crystal display panel 16; a backlight 17 radiating light to the back of the liquid crystal display panel 16; and the projection optical system 20 enlarging and projecting an image displayed on the liquid crystal display panel 16. The projection optical system 20 comprises a relay lens 21 and a projection lens L1. The relay lens 21 is constituted to efficiently use telecentric display light 26 by satisfying some conditions, and forms a real image Ir by enlarging the image displayed on the liquid crystal display panel 16. The projection lens L1 enlarges the real image Ir further and projects it to a windshield 13 of an automobile to display the virtual image Iv for a driver 14. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a head-up display device in which an image is projected onto a windshield of an automobile or an aircraft, and the image is observed as a virtual image through the windshield.

  2. Description of the Related Art A head-up display device is known in which display light of an image is reflected toward a driver (observer) on a windshield of an automobile so that an image of an instrument such as a speedometer can be observed as a virtual image. The instrument image displayed by the head-up display device is enlarged and displayed as a virtual image at a position 2 m or more away from the driver through the windshield. The display image can be observed with almost no change.

  The optical unit used in the head-up display device includes an image display panel, an illumination light source, and a projection optical system. As the image display panel, a transmissive liquid crystal display panel is often used, and a backlight is disposed behind it. Illumination light from the backlight is transmitted through the liquid crystal display panel, becomes display light having image information displayed on the liquid crystal display panel, and enters the projection optical system. The projection optical system magnifies and projects the display light on the windshield, and displays the magnified virtual image on the driver as described above.

As a projection optical system used for a head-up display device, for example, an image displayed on a liquid crystal display panel is enlarged and projected by a mirror lens (Patent Document 1), or an image is projected by an enlarged lens (Patent Document 2). Etc. are known.
JP 2006-11168 A JP 2007-148092 A

  However, when directly enlarging and projecting a display image with a mirror lens or a magnifying lens, the image displayed on the liquid crystal display panel is somewhat due to the relationship between the size of the virtual image to be displayed and the distance from the projection optical system to the virtual image to be displayed. The size of is required. For this reason, a large liquid crystal display panel must be used, and accordingly, a large backlight is required, which makes it difficult to reduce the size, cost and power consumption of the head-up display device. .

  In addition, when the size of the virtual image displayed by the head-up display device is set to about 150 mm that is easy for the driver to observe, the displayed virtual image is displayed with both eyes even if the driver moves about 20 mm from side to side. In order to enable observation with the projection optical system, the exit pupil size of the projection optical system needs to be about 100 mm. At this time, considering that the display light is reflected by the windshield positioned approximately in the middle between the driver and the displayed virtual image, the aperture of the projection optical system needs to be 150 mm. If the distance from the projection optical system to the virtual image is D, the projection magnification is β, and the focal length of the projection optical system is f, x = (1 + β) × f (imaging formula), for example, 0.8 type When the 16 mm width of the liquid crystal display panel is enlarged nine times and a 144 mm virtual image is displayed, the focal length of the projection optical system is 100 mm. However, a lens having a diameter of 150 mm and a focal length of 100 mm has an F value of 0.67 and is extremely bright, so that it is difficult to realize.

  Therefore, instead of directly enlarging and projecting the image displayed on the liquid crystal display panel, a projection optical system is used in which an image enlarged by the relay lens is formed on the screen, and this enlarged image is further enlarged and projected by the projection lens. It is possible. However, this projection optical system has poor utilization efficiency of illumination light, and there is a problem that a virtual image to be displayed becomes darker than before even when a backlight having the same brightness as that of the conventional one is used. On the other hand, in order to display a virtual image with the same level of brightness as a conventional head-up display device, it is necessary to use an extremely high-brightness backlight, which increases the installation space, cost, and power consumption. is there.

  Patent Document 2 discloses a projection optical system that efficiently uses illumination light by forming an aerial image that does not use a screen or the like with a relay lens and matching the NA of the projection optical system with the principal ray angle. This projection optical system has a large projection magnification and has a very large NA on the liquid crystal display panel side.

  As is well known, the liquid crystal display panel has a limited viewing angle at which an image with good contrast and brightness can be observed, and this viewing angle is narrow. Since the projection optical system having a large NA on the liquid crystal display panel side uses display light emitted at an angle larger than the viewing angle of the liquid crystal display panel, the use efficiency of illumination light is increased, but a virtual image to be displayed is displayed. There is a problem that shading occurs in the color and contrast of the image. Also, in order to prevent shading of the color and contrast of the virtual image to be displayed, when illuminating according to the chief ray angle of the projection optical system, the chief ray will diverge to the back side (backlight side). Therefore, there is a problem that the backlight has to be larger than before.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a projection optical system capable of projecting an image displayed on a small liquid crystal display panel as a bright and uniform virtual image. Another object of the present invention is to provide a small and inexpensive head-up display device that projects a bright and uniform virtual image and consumes less power.

  The projection optical system of the present invention is a reflective surface facing an observer at a predetermined position, reflects display light emitted from a transmissive liquid crystal display panel to the observer side, and displays the liquid crystal display through the reflective surface. A projection optical system for enlarging and projecting an image displayed on the panel as a virtual image, irradiating light from behind the liquid crystal display panel, and having information on the image displayed on the liquid crystal display panel from the front of the liquid crystal display panel Illuminating means for emitting display light, a relay lens for condensing display light emitted from the liquid crystal display panel, and enlarging an image displayed on the liquid crystal display panel to form a real image, and the relay lens A projection lens that magnifies and projects the enlarged real image of the image formed by the projection onto the reflecting surface, the focal length of the relay lens is f1, and the image side is in a positive direction. The distance from the image side principal point of the Ray lens to the exit pupil of the relay lens is α, the focal length of the projection lens is f3, and the distance from the image side principal point of the relay lens to the real image formed by the relay lens. b, the distance from the real image to the object-side principal point of the projection lens is δ, the distance from the image-side principal point of the projection lens to the observer is WD, and the size of the range in which the observer's viewpoint moves is Dpo, when the size of the exit pupil of the relay lens is Dpr2, 0.5 <α / f1 <1.5, f3 = WD × (−α + b + δ) / (− α + b + δ + WD), Dpo = Dpr2 × WD / It satisfies the condition of (−α + b + δ).

  Further, when the distance from the observer to the virtual image is L and the magnification of the virtual image with respect to the size of the image displayed on the liquid crystal display panel is M, 1 <L / (M × Dpo) <4 It satisfies the following conditions.

  A head-up display device according to the present invention includes the above-described projection optical system.

  ADVANTAGE OF THE INVENTION According to this invention, the projection optical system which can project the image displayed on a small-sized liquid crystal display panel as a bright uniform virtual image can be provided. In addition, a bright and uniform virtual image can be projected, and a small and inexpensive head-up display device with low power consumption can be provided.

  As shown in FIG. 1, the head-up display device 10 is arranged on a dashboard 12 of an automobile 11, and the values of instruments such as a speedometer are displayed in front of a driver (observer) 14 on a windshield 13 (reflection surface). ) Display over.

  The head-up display device 10 incorporates a small liquid crystal display panel 16 (see FIG. 2), and displays instrument values on the liquid crystal display panel. The head-up display device 10 enlarges and projects the display light 26 emitted from the liquid crystal display panel 16 toward the windshield 13 by the projection optical system 20 (see FIG. 2). The projected display light 26 is reflected by the windshield 13 toward the driver 14.

  The head-up display device 10 does not display a real image on the windshield 13 but displays a virtual image Iv at a position of a distance D from the driver 14 through the windshield 13.

  The distance D at which the virtual image Iv is displayed is sufficiently long so that the virtual image Iv can be viewed with little eye movement during driving and almost no focus adjustment of the eyes. For example, the virtual image Iv is displayed at a distance of 2 m or more from the driver.

  As shown in FIG. 2, the head-up display device 10 includes a liquid crystal display panel 16, a backlight 17 (illuminating means), and a projection optical system 20.

  The liquid crystal display panel 16 displays values of various instruments such as a speedometer, a tachometer, a water temperature gauge, and a fuel gauge. The liquid crystal display panel 16 is a transmissive type, and is illuminated with illumination light from a backlight 17 provided behind, and transmits display light 26 having information on the displayed image to the front.

  The backlight 17 is made of, for example, a white LED, and uniformly illuminates the liquid crystal display panel 16 from behind. Note that the backlight 17 is not limited to irradiating white illumination light with a white LED, and may emit illumination light of a desired color. For example, it may be composed of single-color LEDs such as red, green, and blue, or an image may be displayed in a desired color by combining some of these single-color LEDs. Further, the backlight 17 is not limited to the LED, and other known lamps may be used.

  The projection optical system 20 includes a relay lens 21 and a projection lens L1. The image displayed on the liquid crystal display panel 16 is enlarged and formed as a real image Ir, and then the real image Ir is further enlarged and formed on the windshield 13. Project. The relay lens 21 is configured so that the liquid crystal display panel 16 side (object side) is telecentric. The relay lens 21 condenses the telecentric display light 26 emitted from the liquid crystal display panel 16 and enlarges the image displayed on the liquid crystal display panel 16 to form a real image Ir. The projection lens L1 is, for example, a Fresnel lens, and magnifies and projects the real image Ir formed by the relay lens 21 onto the windshield 13.

  When the focal length of the relay lens 21 is f1, and the distance from the image side principal point Hr2 of the relay lens 21 with the image side in the positive direction to the exit pupil Pr2 of the relay lens 21, the projection optical system 20 is α. It is comprised so that the following formula 1 may be satisfied.

  The condition shown in Equation 1 is to limit the position of the exit pupil Pr2 of the relay lens 21, and out of the display light 26 emitted from the liquid crystal display panel 16, the so-called telecentric that can be regarded as substantially parallel to the optical axis of the relay lens 21. This is a condition for efficiently using only the characteristic display light 26 for image display. When the value of α / f1 exceeds the upper limit and the lower limit of Equation 1, out of the display light 26 emitted from the liquid crystal display panel 16, the display light 26 outside the viewing angle of the liquid crystal display panel 16 is also used for displaying the virtual image Iv. As a result, the virtual image Iv has shading in brightness and contrast.

  Further, the projection optical system 20 has the focal length of the projection lens L1 as f3, the distance from the image side principal point Hr2 of the relay lens 21 to the real image Ir imaged by the relay lens 21, and the real image Ir to the projection lens L1. When the distance to the object side principal point Hp1 is δ and the distance from the image side principal point Hp2 of the projection lens L1 to the driver 14 is WD, the following Expression 2 is satisfied.

  The condition shown in Expression 2 determines the focal length of the projection lens L1 according to the position (value of α) of the exit pupil Pr2 of the relay lens 21 determined so as to satisfy the condition of Expression 1. This is a condition in which the position of the exit pupil Pr2 and the position of the observer range Po are conjugate.

  Furthermore, when the size of the range in which the driver's viewpoint moves (hereinafter referred to as the observer range Po) is Dpo and the size of the exit pupil Pr2 of the relay lens 21 is Dpr2, the projection optical system 20 It is comprised so that the conditions of several 3 may be satisfy | filled. Note that the size Dpo of the observer range Po is, for example, the diameter when the observer range is circular, or the diagonal length when the observer range Po is rectangular, for example. The length of the range Po is a reference length, and the size of the exit pupil Pr2 refers to the diameter of the exit pupil Pr2.

  The condition shown in Equation 3 is that the size Dpr2 of the exit pupil Pr2 of the relay lens 21 and the size of the observer range Po are set according to the position of the exit pupil Pr2 of the relay lens 21 that is determined so as to satisfy the condition of Equation 1. The ratio of Dpo is determined. The telecentric display light 26 determined by Equation 1 is efficiently used so that the most bright and high contrast virtual image Iv can be observed from the observer range Po of a predetermined size. It is a condition to make it.

  Further, the projection optical system 20 has a condition of the following equation 4 when the distance from the driver 14 to the virtual image Iv is L and the magnification of the virtual image Iv with respect to the size of the image displayed on the liquid crystal display panel 16 is M. It is configured to satisfy.

  The effective F number on the liquid crystal display panel 16 side of the relay lens 21 is proportional to L / (M × Dpo). Therefore, if the value of L / (M × Dpo) is below the lower limit of Equation 4, the F number of the relay lens 21 becomes small, and the aberration cannot be corrected sufficiently. On the other hand, when the value of L / (M × Dpo) exceeds the upper limit of Equation 4, the magnification of the relay lens 21 is reduced, and if the virtual image Iv having a predetermined luminance is to be displayed, the liquid crystal display panel 16 is increased in size. Invite.

  Since the projection optical system 20 is configured so as to satisfy the conditions of the above formulas 1 to 4, the optical axis of the relay lens 21 from the liquid crystal display panel 16 as schematically shown in FIG. Only the telecentric display light 26 emitted substantially parallel to the light is used for displaying the virtual image Iv. The telecentric display light 26 is enlarged and formed into a real image Ir by the relay lens 21, and the real image Ir is further enlarged by the projection lens L1 and projected onto the windshield 13.

  Although not shown in FIG. 3 to avoid complication, the display light 26 reflected by the windshield 13 is incident on the eyes of the driver 14 who observes at one point in the observer range Po. Since the telecentric display light 26 emitted from one point of the liquid crystal display panel 16 is incident by the projection lens L1 so as to widen the solid angle within the observer range Po, the driver 14 emitted from these same one point. A virtual image Iv obtained by further enlarging the real image Ir at the position of a virtual intersection of the display light 26 is observed through the windshield 13.

  For example, as schematically shown in FIG. 3B, when the driver 14 observes the virtual image Iv from the lower end of the observer range Po, the display light 26a is incident on the eyes of the driver 14. The display light 26a is telecentric display light 26a that is emitted slightly obliquely upward from the liquid crystal display panel 16 but is emitted at a viewing angle such that the luminance and contrast can be regarded as normal values to be output. Further, when the driver 14 observes the virtual image Iv from the upper end of the observer range Po, the virtual image Iv observed from the lower end of the observer range Po also emits the liquid crystal display panel 16 slightly obliquely downward, but the luminance or It is displayed by the display light 26 having a normal contrast and telecentricity.

  Such a virtual image Iv that the driver 14 observes from a certain position of the observer range Po is displayed by the telecentric display light 26 in a peculiar point such as the upper end, the lower end, or the center of the observer range Po. The virtual image Iv is displayed by the telecentric display light 26 in the same manner when the virtual image Iv is observed from any position within the observer range Po.

  As shown in FIG. 3, it is not necessary to arrange an actual aperture in the relay lens 21 in order to use the telecentric display light 26 for displaying the virtual image Iv. When the projection optical system 20 is configured to satisfy the conditions of Formulas 1 to 4, the display light 26 incident on the eyes of the driver 14 when the virtual image Iv is observed from the observer range Po is relayed. It is automatically limited to the display light 26 emitted from the actual exit pupil (hereinafter, the actual pupil) inside the relay lens 21 conjugate with the exit pupil Pr2 of the lens 21. The size of the real pupil 27 of the relay lens 21 may be the same as the conjugate image in the observer range Po or larger than the conjugate image in the observer range Po. By configuring so as to satisfy the above, the size of the real pupil 27 is the same as the conjugate image of the observer range Po.

  Further, since the projection optical system 20 is configured so as to satisfy the conditions of the above-mentioned formulas 1 to 4, the observer range Po and the exit pupil Pr2 of the relay lens 21 are schematically shown in FIG. The positions are conjugate to each other. Thereby, all the display light 26 emitted from the liquid crystal display panel 16 with a telecentric viewing angle is incident on the observer range Po. Therefore, among the display light 26 emitted from the liquid crystal display panel 16, the display light 26 emitted at a viewing angle with normal brightness and contrast is used for displaying the virtual image Iv most efficiently.

  In particular, the object side principal point Hr2 of the relay lens 21 and the exit pupil Pr2 of the relay lens 21 are not matched, and the distance α from the object side principal point Hr2 of the relay lens 21 to the exit pupil Pr2 of the relay lens 21 as described above. Is set within the range of the condition of Equation 1, the range of the telecentric display light 26 emitted from the liquid crystal display panel 16 matches the observer range Po. Thereby, when observing the virtual image Iv from any position in the observer range Po, only the telecentric display light 26 suitable for displaying the virtual image Iv and causing no shading in luminance and contrast is used for displaying the virtual image Iv. Is done.

  In addition, the projection optical system 20 can sufficiently correct the aberration because the value of L / (M × Dpo) is a value within the range of the condition of Equation 4, and sufficiently A small backlight 17 displays a virtual image Iv with high brightness and high contrast.

  Hereinafter, specific examples of the projection optical system 20 are shown as Examples 1 to 3. The size of the image displayed on the liquid crystal display panel 16 is 30 mm × 10 mm in the first embodiment, 15 mm × 5 mm in the second and third embodiments, and the distance L from the driver 14 to the virtual image Iv is 2 m. It comprised so that it might become. In the lens data shown in each example, the units of L, f1, f3, α, b, δ, Dpo, Dpr2, and WD are all mm.

[Example 1]
As shown in FIG. 5, the projection optical system 31 includes, in order from the image side, three lenses of a projection lens L1, a second lens L2, a third lens L3, and a fourth lens L4 provided with a Fresnel surface on the image side. It is comprised from the relay lens 32 which consists of. Each surface of the lenses constituting these projection optical systems 31 is represented by Si using surface numbers i (i = 1 to 8) in order from the image side. Further, the distance between adjacent surfaces Si (the surface distance between the surface Si and the surface Si + 1 on the optical axis) is Di.

  As lens data of the projection optical system 31, a curvature radius Ri (mm) of each surface Si, a distance between surfaces Di (mm), and a lens number j (j = 1 to 4) in order from the image side, d line (587) Table 1 shows the refractive index Ndj of each lens Lj and the Abbe number νdj of each lens Lj with respect to .6 nm).

  In the lower part of Table 1, the focal length f1 of the relay lens 32, the distance α from the image-side principal point Hr2 of the relay lens 32 to the image-side principal point Hr2 of the relay lens 32 to the exit pupil Pr2 of the relay lens 32, the projection The focal length f3 of the lens L1, the distance b from the image side principal point Hr2 of the relay lens 32 to the real image Ir, the distance δ from the real image Ir to the object side principal point Hp1 of the projection lens L1, and the image side principal point Hp2 of the projection lens L1 To the observer range Po, the size Dpo of the observer range Po, the size Dpr2 of the exit pupil Pr2 of the relay lens 32, the magnification M of the virtual image Iv with respect to the image on the liquid crystal display panel 16, the observer range Po L, the distance L from the virtual image Iv, the value of α / f1, and the value of L / (M × Dpo).

  As shown in Table 1, each surface of the second lens L2 to the fourth lens L4 constituting the relay lens 32 is a spherical surface, and the liquid crystal display panel 16 side (object side) surface of the fourth lens L4. The distance from S8 to the image display surface of the liquid crystal display panel 16 is 52.720 mm.

  As can be seen from Table 1, the projection optical system 31 satisfies α / f1 = 0.66 and satisfies the condition of Equation 1. Further, the focal length f3 of the projection lens L1 is a value that satisfies the condition of Equation 2 calculated from the values of α, b, δ, and WD, and the size Dpo of the observer range Po is α, b, It is a value that satisfies the condition of Equation 3 calculated from δ and Dpr2. Similarly, L / (M × Dpo) = 3.98, which satisfies the condition of Equation 4.

  The spherical aberration of the projection optical system 31 is shown in FIG. 6A, the astigmatism is shown in FIG. 6B, and the distortion is shown in FIG. 6C. The spherical aberration is indicated by a solid line for the e-line (wavelength 546.1 nm), a broken line for the g-line (wavelength 435.8 nm), and a two-point difference line for the C-line (wavelength 656.3 nm). Astigmatism is indicated by a solid line in the sagittal direction and by a broken line in the tangential direction.

  7A to 7D show lateral aberrations in the tangential direction for image heights of the projection optical system 31 of 0 mm, 25 mm, 75 mm, and 80 mm. 7E to 7G show the lateral aberrations in the sagittal direction when the image height of the projection optical system 31 is 25 mm, 75 mm, and 80 mm.

  As described above, since the projection optical system 31 according to the first embodiment is configured to satisfy the conditions of Equations 1 to 4, the telecentric display light 26 emitted from the small liquid crystal display panel 16 can be efficiently used. By utilizing this, when observing the virtual image Iv from any position in the observer range Po, it can be projected as a bright and uniform virtual image Iv without causing shading in luminance and contrast. If the projection optical system 31 is mounted, the head-up display device 10 can project a bright and uniform virtual image Iv with the small liquid crystal display panel 16 and the backlight 17, and therefore, the power consumption is small and the size is small. And inexpensively configured.

[Example 2]
As shown in FIG. 8, the projection optical system 41 includes five projection lenses L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, and a sixth lens L6 in order from the image side. The relay lens 42 is composed of a lens. Each surface of the lenses constituting the projection optical system 41 is represented by a surface number i (i = 1 to 11) in order from the image side. Further, the distance between adjacent surfaces Si (the surface distance between the surface Si and the surface Si + 1 on the optical axis) is Di. Note that the third lens L3 and the fourth lens L4 constituting the relay lens 42 are cemented by a surface S6.

  As lens data of the projection optical system 41, each curvature with respect to the d-line is defined with a curvature radius Ri (mm) of each surface Si, a distance between surfaces Di (mm), and a lens number j (j = 1 to 6) in order from the image side. Table 2 shows the refractive index Ndj of the lens Lj and the Abbe number νdj of each lens Lj.

  In the lower part of Table 2, the focal length f1 of the relay lens 42, the distance α from the image side principal point Hr2 of the relay lens 42 with the image side in the positive direction to the exit pupil Pr2 of the relay lens 42, the projection lens L1 A focal length f3, a distance b from the image side principal point Hr2 of the relay lens 42 to the real image Ir, a distance δ from the real image Ir to the object side principal point Hp1 of the projection lens L1, and an observation from the image side principal point Hp2 of the projection lens L1. The distance WD to the observer range Po, the size Dpo of the observer range Po, the size Dpr2 of the exit pupil Pr2 of the relay lens 42, the magnification M of the virtual image Iv with respect to the image on the liquid crystal display panel 16, and the virtual image from the observer range Po The distance L to Iv, the value of α / f1, and the value of L / (M × Dpo) are shown.

  As shown in Table 2, the distance from the liquid crystal display panel 16 side (object side) surface S11 of the sixth lens L6 to the image display surface of the liquid crystal display panel 16 was 19.412 mm. Further, in the lens constituting the relay lens 42, the surfaces S2, S4, S6 to S11 are spherical surfaces, and the surfaces S1, S3, and S5 are aspherical surfaces. The specific shapes of the aspherical surfaces S1, S3, and S5 are as follows: the length of the perpendicular line drawn from the aspherical point of height y from the optical axis to the tangential plane of the aspherical vertex from the height y. x, the radius of curvature r near the apex of the aspheric surface, the conical coefficient K, and the aspherical coefficient A2i of the second i-th order (i = 2 to 5) are expressed by the following equation (5). Further, the aspherical coefficients of the surfaces S1, S3, and S5 are specifically set to the values shown in Table 3.

  As can be seen from Table 2, the projection optical system 41 satisfies α / f1 = 0.96, which satisfies the condition of Equation 1. Further, the focal length f3 of the projection lens L1 is a value that satisfies the condition of Equation 2 calculated from the values of α, b, δ, and WD, and the size Dpo of the observer range Po is α, b, It is a value that satisfies the condition of Equation 3 calculated from δ and Dpr2. Similarly, L / (M × Dpo) = 1.43, which satisfies the condition of Equation 4.

  The spherical aberration of the projection optical system 41 is shown in FIG. 9A, the astigmatism is shown in FIG. 9B, and the distortion is shown in FIG. 9C. FIGS. 10A to 10D show lateral aberrations in the tangential direction for image heights of 0 mm, 25 mm, 75 mm, and 80 mm. FIGS. 10E to 10G show image heights of 25 mm, The lateral aberration in the sagittal direction is shown for the cases of 75 mm and 80 mm. Note that the notations of these aberrations are the same as those in the first embodiment.

  As described above, since the projection optical system 41 according to the second embodiment is configured to satisfy the conditions of Equations 1 to 4, the telecentric display light 26 emitted from the small liquid crystal display panel 16 can be efficiently used. By utilizing this, an image displayed on the small liquid crystal display panel 16 can be projected as a bright and uniform virtual image Iv without causing shading in luminance and contrast. If the projection optical system 41 is mounted, the head-up display device 10 can project a bright and uniform virtual image Iv with the small liquid crystal display panel 16 and the backlight 17, and thus the power consumption is small and the size is small. And inexpensively configured.

[Example 3]
As shown in FIG. 11, the projection optical system 51 includes, in order from the image side, a relay lens 52 including seven lenses: a projection lens L1 having a Fresnel surface on the image side, a second lens L2 to an eighth lens L8. Consists of Each surface of the lens constituting the projection optical system 51 is represented by Si using a surface number i (i = 1 to 15) in order from the image side. In addition, an interval between adjacent surfaces Si (an exempt interval on the optical axis between surfaces Si and Si + 1) is Di. Note that the fifth lens L5 and the sixth lens L6 constituting the relay lens 52 are joined by a surface S10.

  As lens data of the projection optical system 51, the curvature radius Ri (mm) of each surface Si, the distance between surfaces Di (mm), and the lens number j (j = 1 to 8) in order from the image side, each lens for the d line. Table 4 shows the refractive index Ndj of Lj and the Abbe number νdj of each lens Lj.

  In the lower part of Table 4, the focal length f1 of the relay lens 52, the distance α from the image-side principal point Hr2 of the relay lens 52 to the image-side principal point Hr2 of the relay lens 52 to the exit pupil Pr2 of the relay lens 52, projection The focal length f3 of the lens L1, the distance b from the image side principal point Hr2 of the relay lens 52 to the real image Ir, the distance δ from the real image Ir to the object side principal point Hp1 of the projection lens L1, the image side principal point Hp2 of the projection lens L1 To the observer range Po, the size Dpo of the observer range Po, the size Dpr2 of the exit pupil Pr2 of the relay lens 52, the magnification M of the virtual image Iv with respect to the image on the liquid crystal display panel 16, the observer range Po L, the distance L from the virtual image Iv, the value of α / f1, and the value of L / (M × Dpo).

  As shown in Table 4, each surface of the second lens L2 to the eighth lens L8 constituting the relay lens 52 is a spherical surface, and the liquid crystal display panel 16 side (object side) surface of the eighth lens L8. The distance from S15 to the image display surface of the liquid crystal display panel 16 is 19.886 mm.

  As can be seen from Table 4, the projection optical system 51 satisfies α / f1 = 0.68 and satisfies the condition of Equation 1. Further, the focal length f3 of the projection lens L1 is a value that satisfies the condition of Equation 2 calculated from the values of α, b, δ, and WD, and the size Dpo of the observer range Po is α, b, It is a value that satisfies the condition of Equation 3 calculated from δ and Dpr2. Similarly, L / (M × Dpo) = 2.00, which satisfies the condition of Equation 4.

  The spherical aberration of the projection optical system 51 is shown in FIG. 12A, the astigmatism is shown in FIG. 12B, and the distortion is shown in FIG. 13A to 13D show lateral aberrations in the tangential direction for the image heights of 0 mm, 25 mm, 75 mm, and 80 mm, and FIGS. 13E to 13G show the image height of 25 mm. The lateral aberration in the sagittal direction is shown for the cases of 75 mm and 80 mm. Note that the notations of these aberrations are the same as those in the first embodiment.

  As described above, since the projection optical system 51 according to the third embodiment is configured to satisfy the conditions of Formulas 1 to 4, the telecentric display light 26 emitted from the small liquid crystal display panel 16 is efficiently used. By utilizing this, when observing the virtual image Iv from any position in the observer range Po, it can be projected as a bright and uniform virtual image Iv without causing shading in luminance and contrast. If the projection optical system 51 is mounted, the head-up display device 10 can project a bright and uniform virtual image Iv with the small liquid crystal display panel 16 and the backlight 17, and thus the power consumption is small and the size is small. And inexpensively configured.

  In the above-described embodiment, a refractive lens such as a Fresnel lens is used as the projection lens L1, but not limited thereto, an optical member having a lens effect such as a mirror aspheric lens may be used as the projection lens L1. In the above-described embodiment, the projection lens L1 is an example of a single refraction lens. However, the projection lens L1 may be composed of a plurality of refraction lenses. You may comprise the projection lens L1 combining a certain optical member.

  In the above-described embodiment, a 15 mm × 5 mm 0.8-type liquid crystal display panel or a 30 mm × 10 mm liquid crystal display panel is used as the liquid crystal display panel 16. Other different liquid crystal display panels may be used. Similarly, values determined according to the type and application of the head-up display device, such as the size of the virtual image Iv to be displayed, are not limited to the values shown in the above-described embodiments, and may be set as appropriate.

  In the above-described embodiment, the head-up display device of the present invention is described as an example for an automobile. However, the present invention is not limited to this, and the head-up display device of the present invention is applied to other devices such as an aircraft and a ship. It can be used suitably. Thus, when the head-up display device of the present invention is applied to a device other than an automobile, the surface shape of a non-rotationally symmetric aspheric surface is set according to the shape of a reflecting surface (a windshield in an automobile) that magnifies and projects display light. However, it is necessary to individually determine the detailed surface shape of the concave mirror. Moreover, since the state of inclination and curvature of the windshield differs depending on the vehicle type and the like, the same adjustment is necessary even when the head-up display device of the present invention is used in an automobile.

  Since the head-up display device is installed on a dashboard or the like of an automobile, each part constituting the head-up display device is preferably excellent in heat resistance.

It is explanatory drawing which shows the outline of a head-up display apparatus. It is explanatory drawing which shows the structure of a projection optical system typically. It is explanatory drawing which shows the optical path of display light typically. It is explanatory drawing which shows typically the exit pupil of a relay lens. 1 is a cross-sectional view of a projection optical system of Example 1. FIG. FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, and distortion of the projection optical system of Example 1. 2 is a lateral aberration diagram of the projection optical system of Example 1. FIG. 6 is a cross-sectional view of a projection optical system of Example 2. FIG. FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, and distortion of the projection optical system of Example 2. FIG. 6 is a lateral aberration diagram of the projection optical system of Example 2. FIG. 6 is a cross-sectional view of the projection optical system of Example 3. FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, and distortion of the projection optical system of Example 3. FIG. 6 is a lateral aberration diagram of the projection optical system according to Example 3.

Explanation of symbols

10 Head-up display device 14 Driver (observer)
16 Liquid crystal display panel 17 Backlight (lighting means)
20, 31, 41, 51 Projection optical system 21, 32, 42, 52 Relay lens 26 Display light L1 Projection lens f1 Focal length of relay lens f3 Focal length of projection lens Iv Virtual image Ir Real image Pr2 Exit pupil of relay lens Hr2 Relay lens Image side principal point Po observer range Hp2 image side principal point of the projection lens Hp1 object side principal point of the projection lens

Claims (3)

A reflective surface facing an observer at a predetermined position reflects display light emitted from a transmissive liquid crystal display panel to the observer side, and an image displayed on the liquid crystal display panel through the reflective surface is a virtual image. In the projection optical system that magnifies and projects as
Illuminating means for irradiating light from behind the liquid crystal display panel and emitting display light having image information displayed on the liquid crystal display panel from the front surface of the liquid crystal display panel;
A relay lens for condensing display light emitted from the liquid crystal display panel and enlarging an image displayed on the liquid crystal display panel to form a real image;
A projection lens that magnifies and projects an enlarged real image of the image formed by the relay lens onto the reflecting surface;
With
The distance from the image side principal point of the relay lens to the exit pupil of the relay lens with the focal length of the relay lens as f1, the image side as the positive direction, α, the focal length of the projection lens as f3, and the relay lens B is the distance from the image side principal point to the real image formed by the relay lens, δ is the distance from the real image to the object side principal point of the projection lens, and the observer is the image side principal point of the projection lens. Is WD, the size of the range in which the observer's viewpoint moves is Dpo, and the size of the exit pupil of the relay lens is Dpr2.
0.5 <α / f1 <1.5,
f3 = WD × (−α + b + δ) / (− α + b + δ + WD),
Dpo = Dpr2 × WD / (− α + b + δ)
A projection optical system characterized by satisfying the following condition. When the distance from the observer to the virtual image is L, and the magnification of the virtual image with respect to the size of the image displayed on the liquid crystal display panel is M,
1 <L / (M × Dpo) <4
The projection optical system according to claim 1, wherein the following condition is satisfied.   A head-up display device comprising the projection optical system according to claim 1.

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