JP2023170238A - Optical system and observation device - Google Patents

Abstract

To provide an optical system that can satisfactorily acquire a corneal reflection image.SOLUTION: An optical system comprises: an observation optical system that includes a half-transmissive reflective surface (HM) and a reflective polarizer (PL1), which transmits linearly polarized light in a first direction and reflects linearly polarized light orthogonal to the first direction; and an imaging optical system that forms an optical image transmitted through the reflective polarizer. A transmission axis azimuth of the reflective polarizer is non-parallel to a plane including an entrance pupil center of the imaging optical system and an optical axis of the observation optical system.SELECTED DRAWING: Figure 1

Description

The present invention relates to an optical system and an observation device.

In recent years, observation devices have become known that provide a realistic experience by enlarging and displaying an original image displayed on a display element such as an LCD via an observation optical system and providing a large screen image to the user. There is. Furthermore, these observation devices have an imaging optical system that images the observer's pupil, and have functions such as personal authentication using an iris image and line-of-sight detection using a pupil image and a corneal reflection image. Here, the observation device is required to have a high specification, small size, and thin configuration, and it is necessary to optimize the combination of a thin and wide-field observation optical system and an imaging optical system that images the observation surface side. is important.

Patent Document 1 discloses a configuration in which an observation optical system using a free-form surface prism and an imaging optical system are combined.

Special Publication No. 2015-508182

When attempting to further widen the viewing angle of the observation optical system disclosed in Patent Document 1, the size of the free-form prism increases, resulting in an increase in the thickness of the optical system. Therefore, in order to expand the viewing angle and make the optical system thinner, a configuration is known in which the observation optical path is folded on the optical axis using a reflective polarizer and a half mirror (triple-pass optical system). . However, when combining a triple-pass optical system with an imaging optical system that images the observation surface side, it is important to adopt a configuration that takes into account the characteristics of the polarizing element in order to obtain a good corneal reflection image.

Therefore, an object of the present invention is to provide an optical system that can satisfactorily acquire a corneal reflection image.

An optical system as one aspect of the present invention includes an observation optical system having a reflective polarizer and a semi-transparent reflective surface that transmits linearly polarized light in a first direction and reflects linearly polarized light orthogonal to the first direction; an imaging optical system that forms an optical image transmitted through a reflective polarizer, and the transmission axis direction of the reflective polarizer is a plane that includes the center of the entrance pupil of the imaging optical system and the optical axis of the observation optical system. is non-parallel to

Other objects and features of the invention are illustrated in the following examples.

According to the present invention, it is possible to provide an optical system that can satisfactorily acquire a corneal reflection image.

1 is a diagram (XY sectional view) showing the basic configuration of an observation device in Example 1. FIG. FIG. 2 is a diagram (YZ sectional view) showing the basic configuration of the observation device in Example 1. FIG. 2 is a diagram showing a corneal reflection optical path diagram and an image on an imaging plane (corneal rotation angle around the Z axis is 0 degrees) in Example 1. FIG. FIG. 2 is a diagram showing a corneal reflection optical path diagram and an image on an imaging plane (corneal rotation angle around the Z axis of −25 degrees) in Example 1. FIG. 2 is a diagram showing a corneal reflection optical path diagram and an image on an imaging plane (corneal rotation angle +25 degrees around the Z axis) in Example 1. FIG. 2 is a diagram showing a corneal reflection optical path diagram and an image on an imaging plane (corneal rotation angle of -25 degrees around the Y-axis) in Example 1. FIG. 2 is a diagram showing a corneal reflection optical path diagram and an image on an imaging plane (corneal rotation angle +25 degrees around the Y-axis) in Example 1. FIG. FIG. 7 is a diagram showing corneal reflection images for each angle Φ. 3 is a cross-sectional view of the optical system in Example 1. FIG. 3 is a cross-sectional view of an optical system in Example 2. FIG. 3 is a cross-sectional view of an optical system in Example 3. FIG. FIG. 4 is a cross-sectional view of an optical system in Example 4. FIG. 2 is an explanatory diagram of a configuration using polarized light. FIG. 3 is an explanatory diagram of reflectance of polarized light. FIG. 7 is a diagram showing a corneal reflection optical path diagram and an image on an imaging surface (corneal rotation angle around the Z axis of 0 degrees) in a comparative example. FIG. 6 is a diagram showing a corneal reflection optical path diagram and an image on the imaging surface (corneal rotation angle around the Z axis +25 degrees) in a comparative example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Each embodiment relates to an optical system and an observation device including an observation optical system that enlarges and displays an image displayed on a display element (display panel) and an imaging optical system that captures an image of the observation surface side. etc. is used as appropriate. The optical system of each embodiment uses an observation optical system (triple-pass optical system) that folds the observation optical path on the optical axis using a reflective polarizer and a half mirror in order to expand the viewing angle and achieve a slim design. use When the imaging optical system is arranged with respect to the triple-pass optical system, it is preferable to adopt a configuration in which the image is transmitted through the observation optical system (observation system TTL configuration) in order to downsize the observation apparatus. Here, the imaging optical system is arranged to pass through the reflective polarizer of the observation optical system and image the observation surface side. At this time, when using the corneal reflection method as a means for detecting the line of sight of the observer, it is necessary to capture a corneal reflection image of the observer.

Here, the reflectance of polarized light will be explained with reference to FIG. FIG. 14 is a diagram showing the reflectance of S-polarized light and P-polarized light with respect to the incident angle of a light ray from air to an interface with a refractive index of 1.33 (corresponding to the refractive index of the cornea). In FIG. 14, the horizontal axis represents the incident angle, and the vertical axis represents the reflectance. Further, in FIG. 14, Rs indicates S-polarized light and Rp indicates P-polarized light. S-polarized light is light with a polarization component perpendicular to the plane containing the incident angle and reflection angle of the light ray, and P-polarized light is light with a polarization component parallel to the plane containing the incidence angle and reflection angle of the light ray. In other words, the light reflected from the cornea becomes S-polarized in many incident angle regions. Therefore, when capturing a corneal reflection image by transmitting it through a reflective polarizer in a triple-pass optical system, depending on the transmission axis direction of the reflective polarizer and the arrangement of the light source and imaging device (camera), the corneal reflection An arrangement occurs where the image is extinguished by the reflective polarizer.

Here, the above problem will be explained with reference to FIGS. 15 and 16. FIG. 15 is a diagram showing a corneal reflection optical path diagram and an image on the imaging plane (corneal rotation angle around the Z axis is 0 degrees) in a comparative example. FIG. 16 is a diagram showing a corneal reflection optical path diagram and an image on the imaging plane (corneal rotation angle around the Z axis +25 degrees) in a comparative example. In FIGS. 15 and 16, the reflective polarizer is modeled as an ideal reflective polarizer without wavelength dependence, and the transmission axis is arranged along the Y-axis direction (angle Φ=0 degree). Further, FIGS. 15 and 16 respectively show the optical path of the corneal reflected image and the image on the imaging surface of the imaging device when the corneal rotation angle around the Z axis is 0 degrees and +25 degrees. Here, the light beam from the light source IRED, which is placed near the Y-axis and at a position where the angle of incidence on the corneal reflective surface is large, is such that the corneal reflected light is polarized to S-polarized light, and the polarization direction of the S-polarized light is perpendicular to the transmission axis of the reflective polarizer. Therefore, the corneal reflection image is extinguished. In particular, when the rotation angle is +25 degrees as shown in FIG. 16, all the corneal reflection images are extinguished, making it impossible to detect the line of sight by the corneal reflection method. In other words, when combining the observation optical system of the triple-pass optical system and the imaging optical system, it is necessary to adopt a configuration that takes into account the characteristics of the polarizing element.

1 and 2 are basic layout diagrams of the observation device in Example 1. A triple-pass optical system is configured by an observation optical system including a transflective element PL1 having a reflective polarizer, a half mirror (semi-transmissive reflective surface) HM, and a convex lens G1. Further, the imaging device CAM that images the observation surface side is arranged at a position where the light passes through the transflective element PL1. The light source IRED is arranged in a circular shape around the observation optical system, as shown in FIG. The corneal reflective surface GC is modeled as an interface with a radius of curvature of -8 mm and a refractive index of 1.33, and the distance on the optical axis between the observation surface side surface of the transflective element PL1 and the surface apex of the corneal reflective surface GC is It is approximately 12 mm. Here, the reflection type polarizer is aligned with respect to the plane (XY plane) including the optical axis of the observation optical system and the center of the entrance pupil of the imaging optical system in the imaging device CAM (in FIG. 2, the center of the aperture stop surface SS of the aperture stop). Let the angle of the transmission axis direction be Φ. In FIG. 2, the angle Φ is 90 degrees, but each embodiment is not limited to this, and the transmission axis direction of the reflective polarizer is between the center of the entrance pupil of the imaging optical system and the light of the observation optical system. It only needs to be parallel to the plane that includes the axis.

The optical system and observation device of each example is for magnifying and observing the image displayed on the display element ID, and is a reflective type that transmits linearly polarized light in the first direction and reflects linearly polarized light orthogonal to the first direction. It has a polarizer (semi-transmissive reflective element PL1) and a semi-transmissive reflective surface (half mirror HM). By setting the observation optical path to a triple-pass configuration, it is possible to realize a thinner optical system and a wider viewing angle. The imaging optical system captures an image of the observation surface side through the reflective polarizer of the observation optical system. By adopting the TTL arrangement of the observation system, it is possible to downsize the observation device. Furthermore, the observation device of each embodiment includes a light source IRED that illuminates the observation surface side. The light source IRED illuminates the observation surface side and is used as a light source for a corneal reflection image, and can realize line-of-sight detection by corneal reflection method.

In each embodiment, the transmission axis direction of the reflective polarizer is not parallel to the plane containing the entrance pupil center of the imaging optical system (the center of the aperture surface SS) and the optical axis of the observation optical system. Preferably, the following conditional expression (1) is satisfied, where the angle of the transmission axis direction of the reflective polarizer with respect to a plane containing the center of the entrance pupil of the imaging optical system and the optical axis of the observation optical system is Φ (degrees). do.

10<Φ<170...(1)
Here, the effect of satisfying conditional expression (1) will be explained with reference to FIGS. 3 to 8, FIG. 15, and FIG. 16. As described above, the reflected light is polarized, so when capturing an image of the reflected light by transmitting it through a linear polarizer, it is important to appropriately arrange the transmission axis of the linear polarizer. 3 to 7 are diagrams showing corneal reflection optical path diagrams and images on the imaging plane in Example 1. Figure 3 shows the rotation angle of the corneal reflective surface GC around the Z axis of 0 degrees, Figure 4 shows the rotation angle of -25 degrees around the Z axis, Figure 5 shows the rotation angle of +25 degrees around the Z axis, and Figure 6 shows the rotation angle around the Y axis. FIG. 7 shows a case where the rotation angle is −25 degrees, and FIG. 7 shows a case where the rotation angle around the Y axis is +25 degrees. In FIG. 16 (rotation angle of the corneal reflective surface GC around the Z axis +25 degrees) as a comparative example, all the corneal reflected images are extinguished by the reflective polarizer. On the other hand, by arranging the transmission axis of the reflective polarizer so as to satisfy conditional expression (1), the reflected light from the corneal reflective surface GC reaches the imaging plane IP of the imaging device CAM.

FIG. 8 is a diagram showing corneal reflection images on the imaging plane IP of the imaging device when the angle Φ is set to 0 degrees, 45 degrees, 90 degrees, and 135 degrees. Here, if conditional expression (1) is satisfied within the range of ±25 degrees of rotation around the Z axis and ±25 degrees of rotation around the Y axis of the corneal reflection surface GC, at least one corneal reflection image reaches the imaging plane IP. reach.

Preferably, the numerical range of conditional expression (1) is set as shown in conditional expression (1a) below.

25<Φ<155...(1a)
More preferably, the numerical range of conditional expression (1) is set as shown in conditional expression (1b) below.

40<Φ<140...(1b)
By adopting the above configuration, the configuration of the thin and wide-field observation optical system and the imaging optical system that images the observation surface side is appropriate, and the optical system and observation device are capable of obtaining a good corneal reflection image. can be realized.

In each embodiment, the reflective polarizer (transflective element PL1) is preferably a flat surface. By arranging a flat reflective polarizer, various manufacturing issues such as internal stress that occurs when the reflective polarizer is molded into a curved surface and air bubbles in the adhesive part when attached to a curved surface of a substrate can be solved. can be alleviated. Further, in each embodiment, preferably, the transflective surface (half mirror HM) has a concave surface facing the observation surface side (concave surface facing the reflective polarizer). By sharing the main power (reciprocal of the focal length) of the observation optical system with the transflective surface, it is possible to configure an observation optical system with a wide field of view without causing chromatic aberration.

In Examples 3 and 4, preferably the observation optical system includes a cemented lens (first lens G1, second lens G2). By configuring the observation optical system using a cemented lens, the configuration becomes more stable against relative lens tilt, compared to a configuration in which a plurality of single lenses are individually held in a lens barrel. Further, in Examples 3 and 4, preferably the transflective surface (half mirror HM) is a cemented surface of a cemented lens. By arranging the semi-transmissive reflective surface on the cemented surface of the cemented lens, the semi-transmissive reflective surface can be protected against changes in the external environment such as moisture absorption or temperature changes.

In each embodiment, preferably a transmissive linear polarizer (transmissive element PL2) is provided on the panel surface side of the transflective surface. With this configuration, a high-quality observation optical system can be realized by employing a configuration that utilizes polarized light, which will be described later. Further, in each example, more preferably, the transmittance at a wavelength of 850 nm of polarized light in a direction perpendicular to the transmission axis of the transmissive linear polarizer disposed on the panel surface side of the transflective surface (0 degree incidence) is as follows: It is 30% or more.

Here, the wavelength band of the observation optical system is the visible light region, and the wavelength band to which the eye is especially sensitive is, for example, 450 nm to 680 nm. In order to efficiently utilize an observation optical system with a triple-pass configuration, it is necessary to sufficiently control the polarization state in the visible light region. On the other hand, the wavelength of 850 nm is near-infrared light to which the eye has almost no sensitivity, and is a wavelength band that is not used as an observation optical system. Here, the wavelength around 850 nm is a wavelength band to which an image sensor such as a CMOS sensor or a CCD sensor has sensitivity, and is therefore suitable for imaging on the observation surface side (obtaining an iris image or a corneal reflection image). In other words, regarding the transmission type linear polarizer placed on the panel surface side, by increasing the transmittance at a wavelength of 850 nm for polarized light in the direction orthogonal to the transmission axis, the function as a linear polarizer in the near-infrared wavelength region is reduced. This makes it possible to suppress a decrease in the amount of transmitted light at near-infrared wavelengths.

Here, a transmissive polarizing element has a high extinction ratio in the visible light region (ratio of linearly polarized light transmittance in the direction of the transmission axis to linearly polarized light transmittance in the direction perpendicular to the transmission axis), but has a small extinction ratio in the near-infrared region. As an example, there is an absorption type polarizing element in which iodine is adsorbed to polyvinyl alcohol. More preferably, the transmission type linear polarizer disposed on the panel surface side has a transmittance of 50% or more at a wavelength of 850 nm for polarized light in a direction perpendicular to the transmission axis. More preferably, the transmittance at a wavelength of 850 nm for polarized light in a direction perpendicular to the transmission axis is 70% or more.

In each embodiment, preferably a transmissive linear polarizer is provided on the observation surface side of the reflective polarizer. More preferably, the transmission axes of the reflective polarizer and the transmission linear polarizer are preferably substantially coincident with each other. Here, "approximately matching" is not limited to cases in which these transmission axis orientations exactly match, but also includes cases in which they are evaluated as substantially matching, for example, even if the difference is within ±10 degrees. If so, it will be evaluated as a substantial match. According to this configuration, the transmission type linear polarizer can cut off the reflected light of the reflection type polarizer with respect to external light incident from the observation surface side. More preferably, the transmittance at a wavelength of 850 nm of polarized light in a direction perpendicular to the transmission axis of the transmissive linear polarizer disposed on the viewing surface side of the reflective polarizer (0 degree incidence) is 30% or more. preferable. According to this configuration, when a configuration is adopted in which imaging is performed at a wavelength in the near-infrared region, the influence of polarization of corneal reflected light can be alleviated. More preferably, the transmission type linear polarizer disposed on the observation surface side has a transmittance of 50% or more at a wavelength of 850 nm for polarized light in a direction perpendicular to the transmission axis. More preferably, the transmittance at a wavelength of 850 nm for polarized light in a direction perpendicular to the transmission axis is 70% or more.

In each example, the light (emission wavelength) from the light source IRED is preferably near-infrared light having an emission peak in the wavelength range of 700 nm to 1200 nm. This wavelength range is outside visible light and has the sensitivity of the image sensor, and allows for both enlarged panel observation using the observation optical system and imaging of the observation surface side using the imaging optical system. On the short wavelength side of 700 nm or less, this is a region where the eye is sensitive, and illumination light for imaging on the observation surface side interferes with virtual image observation on the panel surface. On the other hand, on the long wavelength side of 1200 nm or more, the sensitivity of the image sensor becomes low, which is not preferable. More preferably, the emission wavelength of the light from the light source IRED has an emission peak between 750 nm and 1100 nm. More preferably, the emission wavelength of the light from the light source IRED has an emission peak between 800 nm and 1000 nm. Preferably, at least a portion of the light from the light source IRED passes through the reflective polarizer to illuminate the observer's eyes. According to this configuration, it is possible to downsize the optical system and the observation device.

Next, the configuration of an optical system using polarized light will be described with reference to FIGS. 9 and 13. FIG. 9 is a cross-sectional view of the optical system in Example 1. FIG. 13 is an explanatory diagram of a configuration using polarized light. The optical system includes, in order from the pupil plane SP side to the panel surface (display element ID) side, a reflective polarizer PBS (A), a first quarter-wave plate QWP1 (B), and a half mirror (transflective surface). It has a HM (C), a second quarter wavelength plate QWP2 (D), and a linear polarizing plate POL (E). A transflective element PL1 is configured by the reflective polarizer PBS and the first quarter-wave plate QWP1. Further, the second quarter-wave plate QWP2 and the linear polarizing plate POL constitute a transmission element PL2. CG is a parallel flat glass block such as a cover glass.

Here, the reflective polarizer PBS is a polarization-selective transflector configured to reflect linearly polarized light polarized in the same direction as when it passes through the linear polarizer POL, and transmit linearly polarized light perpendicular to this. An element, for example a wire grid polarizer. At this time, the wire grid forming surface of the reflective polarizer PBS functions as a transflective surface. Further, the first quarter-wave plate QWP1 and the second quarter-wave plate QWP2 are arranged with their respective slow axes tilted by 90°, and relative to the polarized light transmission axis of the linear polarizing plate POL. The slow axis of the first quarter-wave plate QWP1 is arranged at an angle of 45 degrees. The half mirror HM is formed by, for example, a dielectric multilayer film or metal vapor deposition, and functions as a transflective surface.

Next, optical path selection and operation in the configuration using polarized light will be explained with reference to FIG. The light emitted from the display surface (panel surface) of the display element ID (light emitted to display an image) becomes linearly polarized light by the linear polarizing plate POL, becomes circularly polarized light by the second quarter-wave plate QWP2, and becomes half-polarized light. incident on mirror HM. A part of the light that has reached the half mirror HM is reflected, becomes circularly polarized light in the opposite direction, and returns to the second quarter-wave plate QWP2. The reversely circularly polarized light that has returned to the second quarter-wave plate QWP2 is polarized by the second quarter-wave plate QWP2 in a direction perpendicular to that when it first passed through the linear polarizer POL. The light returns to the linear polarizing plate POL and is absorbed by the linear polarizing plate POL.

On the other hand, a part of the light that reaches the half mirror HM is transmitted and becomes linearly polarized light by the first quarter-wave plate QWP1 in the same direction as when it passed through the linear polarizer POL, and becomes a reflective polarized light. input to the child PBS. Here, due to the polarization selectivity of the reflective polarizer PBS, linearly polarized light that is polarized in the same direction as when it passes through the linearly polarizing plate POL is reflected. The light reflected by the reflective polarizer PBS becomes circularly polarized light in the opposite direction to the first quarter-wave plate QWP1 and the second quarter-wave plate QWP2. Inject into HM.

The light reflected by the half mirror HM becomes circularly polarized light in the opposite direction to the light before reflection, and enters the first quarter-wave plate QWP1 in a direction perpendicular to that when it first passes through the linear polarizer POL. The light becomes linearly polarized light and enters the reflective polarizer PBS. Here, due to the polarization selectivity of the reflective polarizer PBS, linearly polarized light that is polarized in a direction perpendicular to that when it passes through the linearly polarizing plate E is transmitted and guided to the pupil plane (exit pupil) SP. Due to the above action, only the light that has passed through the half mirror HM, reflected by the reflective polarizer PBS, reflected by the half mirror HM, and transmitted through the reflective polarizer PBS is guided to the pupil plane SP. Hereinafter, the configuration of the optical system and observation device of each example will be described in detail.

[Example 1]
First, the optical system and observation device of Example 1 will be described with reference to FIGS. 1 and 9. FIG. 9 is a cross-sectional view of the optical system of this example. The optical system of this embodiment includes a transflective element PL1 having a reflective polarizer, a half mirror HM, and a display element ID arranged in this order from the observation surface side (pupil plane SP side), and has a diagonal field of view. It has an observation optical system (numerical example 1) with an angle of about 90 degrees. The observation optical system transmits the light from the display element ID through the half mirror HM, reflects the transflective element PL1, reflects the half mirror HM, transmits the semitransparent reflective element PL1, and guides it to the pupil plane SP. Consists of a coaxial optical system. By adopting a triple-pass configuration for the observation optical system, it is possible to achieve both a wide viewing angle and a reduction in thickness of the observation device. In addition, by arranging the transmission element PL2 having a linear polarizer on the panel surface side (display element ID side) of the half mirror HM, unnecessary light that passes through the observation optical system in a single pass is blocked in a configuration that uses polarized light. can do.

The observation device of this embodiment includes an imaging device CAM that transmits through a reflective polarizer to image the observation surface side, and a light source IRED that illuminates the observation surface side. Here, the angle Φ of the transmission axis direction of the reflective polarizer with respect to the plane containing the entrance pupil center of the imaging optical system of the imaging device CAM (in this example, the center of the aperture surface SS) and the optical axis of the observation optical system is , is set at 90 degrees. Thereby, the reflected light from the corneal reflective surface GC can be transmitted through the reflective polarizer and guided to the imaging device CAM. Furthermore, the imaging optical system of this embodiment shares the observation optical system, and guides light from the observation surface side to the imaging device CAM by passing through both the half mirror HM and the transflective element PL1. With this configuration, it is possible to reduce the imaging angle on the observation surface side and alleviate trapezoidal distortion.

In this example, the transmission axis direction of the reflective polarizer is set to be non-parallel to the plane containing the center of the entrance pupil of the imaging optical system and the optical axis of the observation optical system. , preferably satisfies conditional expression (1). This point also applies to Examples 2 to 4 below.

[Example 2]
Next, with reference to FIG. 10, the optical system and observation device of Example 2 will be described. FIG. 10 is a cross-sectional view of the optical system (observation device) of this example. The observation device of this embodiment has a first lens G1, a second lens G2, and a third lens G3, a transflective element PL1 is provided on the first lens G1, and a transmissive element PL2 is provided on the third lens G3. It is provided. The optical system of this example has an observation optical system (numerical example 2) with a diagonal viewing angle of about 58 degrees. Here, the aspect ratio of the display element ID is 4:3, and FIG. 10 (XY cross section) shows the short side direction of the display element of the observation optical system. In addition, the imaging optical system of this embodiment shares an observation optical system, and transmits light through a transflective element PL1 having a reflective polarizer, a half mirror HM, and a transmitting element PL2 having a linear polarizer, and Light is guided to an imaging device CAM that images the side.

[Example 3]
Next, with reference to FIG. 11, the optical system and observation device of Example 3 will be described. FIG. 11 is a cross-sectional view of the optical system (observation device) of this example. In this example, a cemented lens of the first lens G1 and the second lens G2 is used to configure an observation optical system (numerical example 3) with a diagonal viewing angle of about 80 degrees. In addition, the imaging optical system of this embodiment shares a part of the observation optical system, and the observation optical system on the panel side of the transflective element PL1 having a reflective polarizer, the half mirror HM, and the second lens G2 is effective. The light passes through the outside of the area and is guided to the imaging device CAM that images the observation surface side. In this embodiment, by making the area outside the effective area of the observation optical system and the effective area of the imaging light beam a flat surface, it is possible to reduce the occurrence of astigmatism.

[Example 4]
Next, with reference to FIG. 12, the optical system and observation device of Example 4 will be described. FIG. 12 is a cross-sectional view of the optical system (observation device) of this example. The observation device of this example includes a first lens G1, a second lens G2, a third lens G3, a fourth lens G4, a fifth lens G5, a sixth lens G6, and a seventh lens G7. The first lens G1 and the second lens G2 constitute a cemented lens (first cemented lens), and the half mirror HM is provided on the cemented surface of the first lens G1 and the second lens G2. The transflective element PL1 is provided on the first lens G1, and the transmissive element PL2 is provided on the second lens G2. The fourth lens G4 and the fifth lens G5 constitute a cemented lens (second cemented lens). The optical system of this example includes an observation optical system (numerical example 4) having an intermediate image with a diagonal viewing angle of about 69 degrees. Here, the aspect ratio of the display element ID is 4:3, and FIG. 12 (XY cross section) shows the short side direction of the display element ID of the observation optical system. In the observation optical system of this embodiment, the first lens G1 and the second lens G2 are cemented lenses made of the same material, and the air interface is a plane, thereby forming a parallel plate.

In this embodiment, a transflective element PL1 composed of a reflective polarizer and a quarter-wave plate is arranged on the observation surface side of the first lens G1, and a half mirror HM is arranged on the cemented surface of the cemented lens. There is. Further, a transmission element PL2 composed of a quarter-wave plate and a linear polarizer is arranged on the panel surface side of the second lens G2. Further, the reflective surface (ninth surface) is arranged as a plane combiner made of a second reflective polarizer. With this configuration, external light passes through the cemented lens of this example in a single pass and is observed at approximately the same magnification, and the image light of the display element ID passes through the cemented lens of this example in triple passes and is observed at an enlarged magnification. A so-called optical see-through type observation optical system can be realized. In addition, the imaging optical system of this embodiment shares the cemented lens of the observation optical system, and transmits light through the panel side surface of the transflective element PL1 having a reflective polarizer, the half mirror HM, and the second lens G2. Light is guided to an imaging device CAM that images the observation surface side.

Next, numerical examples 1 to 4 corresponding to examples 1 to 4 regarding the observation optical system will be shown. In each numerical example, the surface number i indicates the order of the surfaces from the object side, and ri is the radius of curvature of the lens surface. di is the lens thickness or air gap between the i-th surface and the (i+1)-th surface. ndi and vdi represent the refractive index and Abbe number for the d-line, respectively. "*" indicates an aspheric surface. Furthermore, k, A4, A6, A8, A10, and A12 are aspheric coefficients. The aspherical shape x is determined by the displacement in the optical axis direction at a height h from the optical axis, with the apex of the surface as a reference,
x=(h ² /R)/[1+{1-(1+k)(h/R) ² } ^1/2 ]+A4・h ⁴ +A6・h ⁶ +A8・h ⁸ +A10・h ¹⁰
It is expressed as However, R is the paraxial radius of curvature.

(Numerical Example 1)
Unit: mm

Surface data Surface number rd nd νd Effective diameter
1 (Aperture) ∞ 15.00 4.00
2 ∞ 0.20 1.62000 55.0 40.00
3 ∞ 8.00 1.48749 70.2 40.00
4* -57.436 -8.00 (reflective surface) 40.00
5 ∞ 8.00 (reflective surface) 40.00
6* -57.436 7.39 40.00
7 ∞ 0.20 1.62000 55.0 30.00
8 ∞ 0.70 1.51633 64.1 30.00
9 ∞ 0.00 30.00
Image plane ∞

Aspheric data 4th surface
K =-1.00000e+00 A 4= 4.50466e-07

Page 6
K =-1.00000e+00 A 4= 4.50466e-07

Focal length 18.00
Pupil diameter 4.00
Viewing angle 45.00
Lens total length 47.49
BF(inG) 16.49

Single lens data lens starting surface focal length
SP 1 0.00
PL1 2 0.00
G1 3 117.82
PL2 7 0.00
CG8 0.00

(Numerical Example 2)
Unit: mm

Surface data Surface number rd nd νd Effective diameter (Y,Z)
1 (Aperture) ∞ 18.00 4.0
2 ∞ 0.20 1.50000 50.0 27.5
3 ∞ 3.00 1.53000 55.9 27.5
4* -38.483 1.87 27.5
5 -38.005 -1.87 (reflective surface) 27.5
6* -38.483 -3.00 1.53000 55.9 27.5
7 ∞ 3.00 (reflective surface) 27.5
8* -38.483 1.87 27.5
9 -38.005 1.83 1.63600 23.9 27.5
10* 99.896 0.85 23.5
11 ∞ 0.20 1.50000 50.0 21.0
12 ∞ 3.00 1.48749 70.2 21.0
13 -30.050 0.76 21.0
14 ∞ 0.40 1.51633 64.1 (8.2,11.0)
15 ∞ 0.00 (8.2,11.0)
Image plane ∞

Aspheric data 4th surface
K = 0.00000e+00 A 4= 1.14783e-05 A 6= 8.12048e-08 A 8=-3.42503e-10
A10= 1.00372e-12

Page 6
K = 0.00000e+00 A 4= 1.14783e-05 A 6= 8.12048e-08 A 8=-3.42503e-10
A10= 1.00372e-12

Side 8
K = 0.00000e+00 A 4= 1.14783e-05 A 6= 8.12048e-08 A 8=-3.42503e-10
A10= 1.00372e-12

Side 10
K = 0.00000e+00 A 4=-2.17485e-04 A 6= 1.14074e-06 A 8=-3.03928e-09
A10= 2.89322e-12

Various data

Focal length 12.97
Pupil diameter 4.00
Viewing angle (panel short side direction) 17.20
Lens total length (inG) 12.11

Single lens data lens starting surface focal length
SP 1 0.00
PL1 2 0.00
G1 3 72.61
G2 9 -43.07
PL2 11 0.00
G3 12 61.64
CG14 0.00

(Numerical Example 3)
Unit: mm

Surface data Surface number rd nd νd Effective diameter
1 (Aperture) ∞ 18.00 4.0
2 ∞ 0.20 1.50000 50.0 38.0
3 ∞ 7.00 1.53000 55.9 38.0
4* -41.951 -7.00 (reflective surface) 38.0
5 ∞ 7.00 (reflective surface) 38.0
6* -41.951 2.40 1.63600 23.9 38.0
7* -73.131 0.95 27.0
8 ∞ 0.30 1.50000 50.0 30.0
9 ∞ 0.30 1.50000 50.0 30.0
10 ∞ 1.25 30.0
11 ∞ 0.70 1.51633 64.1 30.0
12 ∞ 0.00 30.0
Image plane ∞

Aspheric data 4th surface
K = 0.00000e+00 A 4=-2.58220e-06 A 6= 1.47199e-08 A 8=-5.32418e-11
A10=7.50680e-14

Page 6
K = 0.00000e+00 A 4=-2.58220e-06 A 6= 1.47199e-08 A 8=-5.32418e-11
A10=7.50680e-14

Side 7
K = 0.00000e+00 A 4= 1.82030e-04 A 6=-1.33313e-06 A 8= 2.80530e-09

Various data

Focal length 13.50
Pupil diameter 4.00
Viewing angle 40.00
Lens total length (inG) 13.10

Single lens data lens Starting surface Focal length
SP 1 0.00
PL1 2 0.00
G1 3 79.15
G2 6 -159.48
PL2 8 0.00
PL2 9 0.00
CG 11 0.00

(Numerical Example 4)
Unit: mm

Surface data Surface number rd nd νd Effective diameter (Y,Z)
1 (aperture) ∞ 19.00 4.0
2 ∞ 0.20 1.50000 50.0 43.0
3 ∞ 4.38 1.54400 56.0 43.0
4* -80.834 -4.38 (reflective surface) 43.0
5 ∞ 4.38 (reflective surface) 43.0
6* -80.834 1.50 1.54400 56.0 43.0
7 ∞ 0.20 1.50000 50.0 (32.0,43.0)
8 ∞ 15.47 (32.0,43.0)
9 ∞ -14.80 (reflective surface) (21.0,17.0)
10 98.671 38.80 (reflective surface) (12.0,15.0)
11 16.049 3.47 1.95375 32.3 14.5
12 -69.698 2.09 14.0
13 -19.195 2.01 1.85150 40.8 12.7
14 -11.340 1.20 1.95906 17.5 12.5
15 -65.988 2.59 13.4
16 12.157 6.50 1.65160 58.5 15.7
17 -23.061 0.66 14.7
18* 63.474 3.50 1.63600 23.9 12.8
19* 20.422 3.55 12.1
20 ∞ 0.70 1.51633 64.1 13.7
21 ∞ 0.00 13.7
Image plane ∞

Aspheric data 4th surface
K = 0.00000e+00 A 4= 7.33649e-07 A 6=-1.66877e-09 A 8= 5.28772e-12
A10=-5.05759e-15

Page 6
K = 0.00000e+00 A 4= 7.33649e-07 A 6=-1.66877e-09 A 8= 5.28772e-12
A10=-5.05759e-15

Page 18
K = 0.00000e+00 A 4=-5.74635e-04

Page 19
K = 0.00000e+00 A 4= 5.49158e-05 A 6= 6.48873e-06

Various data

Focal length -9.05
Pupil diameter 4.00
Viewing angle (panel short side direction) 22.90
Lens total length (inG) 129.38

Single lens data lens Starting surface Focal length
SP 1 0.00
PL1 2 0.00
G1 3 148.59
G2 6 -148.59
PL2 7 0.00
G3 11 13.95
G4 13 29.12
G5 14 -14.43
G6 16 13.18
G7 18 -48.89
CG20 0.00

According to each embodiment, it is possible to provide an optical system and an imaging device that can satisfactorily acquire a corneal reflection image.

The disclosure of each embodiment includes the following configurations and methods.
(Configuration 1)
an observation optical system having a reflective polarizer and a transflective surface that transmits linearly polarized light in a first direction and reflects linearly polarized light perpendicular to the first direction;
an imaging optical system that forms an optical image transmitted through the reflective polarizer;
The optical system is characterized in that the transmission axis direction of the reflective polarizer is not parallel to a plane including the center of the entrance pupil of the imaging optical system and the optical axis of the observation optical system.
(Configuration 2)
When the angle of the transmission axis direction of the reflective polarizer with respect to the plane including the entrance pupil center of the imaging optical system and the optical axis of the observation optical system is Φ (degrees),
10<Φ<170
The optical system according to configuration 1, which satisfies the following conditional expression.
(Configuration 3)
3. The optical system according to configuration 1 or 2, wherein the reflective polarizer is a flat surface.
(Configuration 4)
4. The optical system according to any one of configurations 1 to 3, wherein the transflective surface has a concave surface facing the reflective polarizer.
(Configuration 5)
5. The optical system according to any one of configurations 1 to 4, wherein the observation optical system includes a cemented lens.
(Configuration 6)
6. The optical system according to configuration 5, wherein the transflective surface is a cemented surface of the cemented lens.
(Configuration 7)
7. The optical system according to any one of configurations 1 to 6, further comprising a transmission linear polarizer.
(Configuration 8)
8. The optical system according to configuration 7, wherein the transmissive linear polarizer is disposed on the panel side of the transflective surface.
(Configuration 9)
The transmissive linear polarizer is arranged on the observation surface side of the reflective polarizer,
8. The optical system according to configuration 7, wherein the transmission axes of the transmission linear polarizer and the reflection polarizer have the same direction.
(Configuration 10)
10. The optical system according to any one of configurations 7 to 9, wherein the transmittance of polarized light in a direction perpendicular to the transmission axis of the transmission type linear polarizer at a wavelength of 850 nm is 30% or more.
(Configuration 11)
The imaging optical system has an aperture stop,
11. The optical system according to any one of configurations 1 to 10, wherein the entrance pupil center is the center of a diaphragm surface of the aperture stop.
(Configuration 12)
12. The optical system according to any one of configurations 1 to 11, wherein the observation optical system and the imaging optical system share the reflective polarizer and the semi-transparent reflective surface.
(Configuration 13)
An observation device comprising the optical system according to any one of Structures 1 to 12 and a light source.
(Configuration 14)
14. The observation device according to configuration 13, further comprising a display element that emits light for displaying an image.
(Configuration 15)
15. The observation device according to configuration 13 or 14, wherein the light from the light source is near-infrared light having an emission peak in a wavelength range of 700 nm to 1200 nm.
(Configuration 16)
16. The observation device according to any one of configurations 13 to 15, wherein at least a portion of the light from the light source passes through the reflective polarizer to illuminate the observer's eyes.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the invention.

PL1 Transflective element HM Half mirror (semi-transparent reflective surface)

Claims (16)

an observation optical system having a reflective polarizer and a transflective surface that transmits linearly polarized light in a first direction and reflects linearly polarized light perpendicular to the first direction;
an imaging optical system that forms an optical image transmitted through the reflective polarizer;
The optical system is characterized in that the transmission axis direction of the reflective polarizer is non-parallel to a plane containing the entrance pupil center of the imaging optical system and the optical axis of the observation optical system. When the angle of the transmission axis direction of the reflective polarizer with respect to the plane including the entrance pupil center of the imaging optical system and the optical axis of the observation optical system is Φ (degrees),
10<Φ<170
The optical system according to claim 1, wherein the optical system satisfies the following conditional expression. The optical system according to claim 1, wherein the reflective polarizer is a flat surface. The optical system according to claim 1, wherein the transflective surface has a concave surface facing the reflective polarizer. The optical system according to claim 1, wherein the observation optical system includes a cemented lens. 6. The optical system according to claim 5, wherein the transflective surface is a cemented surface of the cemented lens. The optical system according to claim 1, further comprising a transmission linear polarizer. 8. The optical system according to claim 7, wherein the transmissive linear polarizer is disposed on the panel side of the transflective surface. The transmissive linear polarizer is arranged on the observation surface side of the reflective polarizer,
8. The optical system according to claim 7, wherein the transmission axes of the transmission linear polarizer and the reflection polarizer have the same orientation. 8. The optical system according to claim 7, wherein the transmittance of polarized light in a direction perpendicular to the transmission axis of the transmission type linear polarizer at a wavelength of 850 nm is 30% or more. The imaging optical system has an aperture stop,
2. The optical system according to claim 1, wherein the entrance pupil center is the center of a diaphragm surface of the aperture stop. The optical system according to claim 1, wherein the observation optical system and the imaging optical system share the reflective polarizer and the semi-transparent reflective surface. An observation device comprising the optical system according to claim 1 and a light source. The observation device according to claim 13, further comprising a display element that emits light for displaying an image. The observation device according to claim 13, wherein the light from the light source is near-infrared light having an emission peak in a wavelength range of 700 nm to 1200 nm. 14. The observation device according to claim 13, wherein at least a portion of the light from the light source passes through the reflective polarizer and illuminates the observer's eyes.