JP7557347B2 - 3D image display device - Google Patents

Description

The present invention relates to a three-dimensional image display device that displays a group of elemental images in a time-division manner for each predetermined depth display range.

A wide variety of 3D image display methods are known, including the twin-eye method using 3D glasses. Among them, the integral method has been proposed as a type of light field display that reproduces 3D images by light reproduction.

This integral method can reproduce natural 3D images with horizontal and vertical parallax by placing a lens array composed of many tiny lenses in front of the display device. Furthermore, with the integral method, the display characteristics of 3D images are determined by the pixel density of the display device and the design of the lens array. One issue with this integral method is that the spatial resolution of 3D images decreases when they are reproduced at deep depth positions. To increase the spatial resolution at deep depth positions without narrowing the viewing angle, the lens pitch of the lens array can be lengthened and the focal length can be increased. In this case, the spatial resolution of 3D images at shallow depth positions decreases, making it difficult to reproduce 3D images with high spatial resolution across the entire depth display range.

In order to solve the above-mentioned problems, a conventional technology has been proposed that uses a time-division display technique to improve the spatial resolution characteristics of 3D images at deep depth positions (for example, Non-Patent Document 1). This conventional technology uses one lens array and multiple LCD displays, and displays elemental images on each LCD display in frame sequential order. In other words, the conventional technology utilizes the fact that the depth positions at which spatial resolution is high differ depending on the distance between the multiple LCD displays and the lens array, and displays the 3D images played on each LCD display in a time-division manner. As a result, the conventional technology can play 3D images with high spatial resolution over a wide depth display range.

Applied Optics, Vol. 45, No. 18, June 2006

However, with the above-mentioned conventional technology, as the light passes through each LCD display, the brightness of the light is significantly reduced due to the shielding around the pixel openings of the LCD display, so unless a very bright backlight is used, the displayed image becomes dark. Furthermore, with the conventional technology, a video playback device is required for each LCD display, which causes the system configuration to become large-scale and complex.

Therefore, the objective of the present invention is to provide a three-dimensional image display device that has high spatial resolution, suppresses the decrease in brightness, and is simple in configuration.

To solve the above problem, the three-dimensional image display device according to the present invention is a three-dimensional image display device that displays a group of element images corresponding to a predetermined depth display range in a time-division manner, and is configured to include a display means that displays the group of element images made up of element images, and a lens array that is made up of element lenses arranged two-dimensionally and can switch between a lens state in which the element lenses function as convex lenses and a transmission state in which the element lenses transmit light from the element images.

According to this configuration, a lens array is provided for each depth display range so that the distance from the display means is different. Furthermore, the lens array closer to the display means has a shorter distance between element lenses and a shorter focal length of the element lenses than the lens array farther from the display means. In other words, the lens array closer to the display means has a short lens pitch and focal length, so it can reproduce 3D images with high spatial resolution at shallow depth positions. On the other hand, the lens array farther from the display means has a long lens pitch and focal length, so it can reproduce 3D images with high spatial resolution at deep depth positions.

Therefore, in a three-dimensional image display device, by time-divisionally displaying elemental image groups that have high spatial resolution in different depth display ranges, it is possible to reproduce three-dimensional images with high spatial resolution in all depth display ranges. Furthermore, since a three-dimensional image display device has only one display means, the configuration is simplified, and since the light of the elemental image groups emitted from the display means does not pass through other display means, a decrease in brightness can be suppressed.

The present invention provides a three-dimensional image display device that has high spatial resolution, suppresses brightness degradation, and is simple in configuration.

1 is a schematic configuration diagram of a three-dimensional image display device according to a first embodiment. FIG. 1A is an explanatory diagram illustrating a Nyquist frequency in a conventional stereoscopic display device, and FIG. FIG. 11 is an explanatory diagram illustrating a maximum spatial frequency in a conventional stereoscopic display device. FIG. 1 is an explanatory diagram illustrating a viewing zone angle in a conventional stereoscopic display device. 2 is an explanatory diagram illustrating a maximum spatial frequency in the three-dimensional image display device of FIG. 1 . FIG. 11 is a schematic diagram illustrating the configuration of a three-dimensional image display device according to a second embodiment. In the second embodiment, (a) is an explanatory diagram for explaining a lens state, and (b) is an explanatory diagram for explaining a transmission state. FIG. 11 is a schematic diagram illustrating the configuration of a three-dimensional image display device according to a third embodiment. In the third embodiment, (a) is an explanatory diagram in which the front-stage lens array is in the lens state, and (b) is an explanatory diagram in which the rear-stage lens array is in the lens state.

Each embodiment of the present invention will be described below with reference to the drawings. However, each embodiment described below is intended to embody the technical concept of the present invention, and unless otherwise specified, the present invention is not limited to the following. In addition, the same means will be given the same reference numerals, and the description may be omitted.

First Embodiment
[Configuration of 3D image display device]
The configuration of a three-dimensional image display device 1 according to the first embodiment will be described with reference to FIG.
The three-dimensional image display device 1 displays a group of elemental images corresponding to a predetermined depth display range in a time-division manner. As shown in Fig. 1, the three-dimensional image display device 1 includes a display unit 2, a lens array 3 ( ₃₁ , ₃₂ ), and a synchronization control device 4.

The display means 2 is a general display device that displays a group of elemental images composed of elemental images. In addition, the display means 2 displays a group of elemental images in a depth display range corresponding to the lens array 3 in a lens state described later in a time-division manner in response to a command from the image switching means 41 described later. For example, a direct-view display device such as a liquid crystal display or an organic EL (organic electroluminescence) display can be used as the display means 2. In this embodiment, the display means 2 is disposed at a location where focal lengths _f1 and _f2 described later coincide.

The lens array 3 is composed of element lenses 30 arranged two-dimensionally. The lens array 3 is a lens/transmission switchable lens array that can switch between a lens state and a transmission state in response to a command from a switching control means 40 described later.
The lens state refers to a state in which each element lens 30 functions as a convex lens with respect to the light of the element image, and the transmission state refers to a state in which each element lens 30 transmits the light of the element image.

For example, the lens array 3 can be a two-dimensional array of liquid crystal lenses as element lenses 30. Here, the liquid crystal lens is made of liquid crystal sealed in a lens-shaped space, and can change the effective refractive index according to the applied voltage to switch between the lens state and the transmission state. The liquid crystal lens may also switch between the lens state and the transmission state by changing the polarization state of the incident light.

Further, the lens array 3 is provided for each depth display range so that the distance from the display means 2 is different. In this embodiment, two lens arrays 3 are provided, such as a lens array 3 ₁ close to the display means 2 and a lens array 3 ₂ far from the display means 2.

Here, the lens array ₃₁ closer to the display means 2 has a shorter lens pitch (the distance between the element lenses 30) and a shorter focal length of the element lenses 30 than the lens array 32 farther from the display means _2. As shown in Fig. 1, the lens pitch _p1 of the lens array ₃₁ is shorter than the lens pitch p2 of the lens array _32. Here, since the lens pitch _p1 is half the lens pitch _p2 , the lens array ₃₁ has twice as many element lenses 30 as the lens array _32. Also, the focal length _f1 of the element lenses ₃₀ constituting the lens array ₃₁ is shorter than the focal length _f2 of _the element lenses 30 constituting the lens array 32.

In FIG. 1, for ease of understanding, the lens array ₃₁ has 1,212 element lenses 30 and the lens array ₃₂ has 6 element lenses 30, but a large number of element lenses 30 (e.g., several hundred or more) may be provided.

The synchronization control device 4 synchronizes the display timing of the elemental image group with the switching timing of the lens state or the transparent state on a frame-by-frame basis, and includes a switching control means 40 and an image switching means 41. For example, the synchronization control device 4 performs switching at a speed at which viewer A does not perceive flicker = N x 60 Hz (where N is the number of lens arrays 3).

The switching control means 40 switches the state of the lens array 3 in a time-division manner so that one of the lens arrays 3 is in the lens state and the other lens array 3 is in the transmission state. In this embodiment, the switching control means 40 alternates between a case where the lens array ₃₁ is in the lens state and the lens array ₃₂ is in the transmission state, and a case where the lens array ₃₁ is in the transmission state and the lens array ₃₂ is in the lens state.

The image switching means 41 synchronously displays the elemental image group in the depth display range corresponding to the lens array 3 in the lens state on the display means 2. Here, when the lens array _3-1 is in the lens state, the image switching means 41 displays the elemental image group in the depth display range corresponding to the lens array _3-1 on the display means 2. Also, when the lens array _3-2 is in the lens state, the image switching means 41 displays the elemental image group in the depth display range corresponding to the lens array _3-2 on the display means 2. It is assumed that the elemental image groups in the depth display range corresponding to the lens arrays _{3-1 and 3-2} are stored in advance.

[Time-division display by 3D image display device]
The spatial resolution characteristics of the integral system will be described below as a premise for time-division display by the three-dimensional image display device 1.
First, in order to facilitate understanding of the spatial resolution characteristics of the integral system, the maximum spatial frequency, the Nyquist frequency, and the visual spatial frequency, which are indices indicating the spatial resolution characteristics, will be described.

The maximum spatial frequency β _max [cycles per radian (cpr)] is expressed by the following formula (1), where β _n is the Nyquist frequency [cpr], β is the visual spatial frequency [cpr], and min is a function that returns the minimum value of the specified parameters.

Figure 2 shows a conventional stereoscopic display device 9 that employs the integral method. The stereoscopic display device 9 includes a display device 90 that displays a group of elemental images, and a lens array 92 in which elemental lenses 91 are arranged two-dimensionally.

2A, the Nyquist frequency _βn indicates a spatial frequency resulting from sampling of a three-dimensional image B by element lenses 91, and is expressed by the following formula (2): p is the lens pitch of the lens array 92, and L is the viewing distance from the viewer A to the lens array 92.

On the other hand, the perceived spatial frequency β indicates the spatial frequency resulting from sampling of the three-dimensional image B by the pixels of the display device 90, as shown in FIG. 2(b), and is expressed by the following equation (3). Note that f is the focal length of the lens array 92, g is the pixel pitch of the display device 90, and z is the depth position of the three-dimensional image B. Furthermore, the depth position z is positive on the viewer A side.

3 shows an example of a graph of spatial resolution characteristics when pixel pitch g=50 μm, lens pitch p=0.3 mm, focal length f=1.5 mm, and viewing distance L=2000 mm. The origin (z=0) of the depth position is the surface (lens array surface) on which the lens array 92 is located. However, in FIG. 3, the unit of the maximum spatial frequency β _max is converted from [cycles per radian (cpr)] to [cycles per degree (cpd)].

3, the maximum spatial frequency _βmax is the Nyquist frequency _βn when the depth position z of the three-dimensional image B is shallow. On the other hand, when the depth position z of the three-dimensional image B becomes deep, the influence of the visual spatial frequency β becomes more dominant than the Nyquist frequency _βn , and the maximum spatial frequency _βmax decreases.

The viewing angle of an integral 3D image will now be described. As shown in FIG. 4, the viewing angle θ of an integral 3D image is determined by the lens pitch p and focal length f of the lens array 92, and is expressed by the following equation (4).

Next, the time-division display of the elemental images by the three-dimensional image display device 1 will be described.
Here, consider the case where the lens array ₃₁ closer to the display means 2 is in the lens state. In this case, the Nyquist frequency _βn in equation (2) becomes high, so the spatial resolution of the three-dimensional image B becomes high at a shallow depth position z. On the other hand, the observed spatial frequency β in equation (3) becomes low, so the spatial resolution of the three-dimensional image B becomes low at a deep depth position z.

Also, consider a case where the lens array ₃₂ , which is farther from the display means 2, is in the lens state, compared to a case where the lens array ₃₁ is in the lens state. The spatial resolution of the three-dimensional image B becomes lower at a shallow depth position z, but the spatial resolution of the three-dimensional image B becomes higher at a deep depth position z.

As described above, in a certain frame, the three-dimensional image display device 1 sets the lens array ₃₁ to the lens state and plays back only the three-dimensional image B at the shallow depth position z. Then, in the next frame, the three-dimensional image display device 1 sets the lens array ₃₂ to the lens state and plays back only the three-dimensional image B at the deep depth position z. In this way, the three-dimensional image display device 1 can play back the three-dimensional image B at a high maximum spatial resolution at all depth positions z by displaying the elemental image group in a time-division manner.

It is necessary to set the same viewing zone angle θ of the 3D image B reproduced by each lens array 3. If the viewing zone angle θ of the 3D image B is different, the viewing zone angle θ will be the same as that of the lens array 3 having the narrowest viewing zone angle θ, resulting in inefficient light reproduction. In the 3D image display device 1 of Figure 1, it is necessary to set the lens pitch P and focal length f of each lens array _3-1 , _3-2 so as to satisfy the following formula (5) based on the above formula (4).

A graph showing the spatial resolution characteristics of the three-dimensional image B reproduced by the three-dimensional image display device 1 and the depth display range of each lens array 3 is shown in Fig. 5. In the example of Fig. 5, the lens pitch _p1 of the lens array 31 is 0.3 mm and the focal length _f1 is 1.5 mm, and the lens pitch _p2 of the lens array ₃₂ is 0.6 mm and the focal length _f2 is 3.0 mm. The viewing angle θ of the three- _dimensional image B reproduced by both lens arrays 3 is about 11 degrees according to formula (4). In addition, the pixel pitch g of the display means 2 is 50 μm, and the viewing distance L is 2000 mm.

When the maximum spatial resolution β _max1 of the lens array 3 ₁ and the maximum spatial resolution β _max2 of the lens array 3 ₂ are calculated from the above formulas (1) to (3), the depth positions z of the intersections of the maximum spatial resolutions β _max1 and β _max2 are -16 mm and 19 mm. Therefore, the lens array 3 ₁ plays back the 3D image B in a depth display range R ₁ of -16 to 19 mm. Moreover, the lens array 3 ₂ plays back the 3D image B in a depth display range R ₂ that is deeper than the depth display range R ₁ .

It goes without saying that the depth display range of the three-dimensional image display device 1 is not limited to the example shown in FIG.
Furthermore, the three-dimensional image display device 1 may set three or more depth display ranges. In this case, the three-dimensional image display device 1 may be provided with the same number of lens arrays 3 as the depth display ranges, and the elemental images corresponding to each depth display range may be displayed on the display means 2 in a time-division manner.

[Action and Effects]
As described above, in the three-dimensional image display device 1, the elemental image group having high spatial resolution in different depth display ranges is time-divided, thereby making it possible to reproduce a three-dimensional image B having high spatial resolution in all depth display ranges. Furthermore, in the three-dimensional image display device 1, since there is only one display means 2, the configuration is simplified, and since the light of the elemental image group emitted from the display means 2 does not pass through other display means, a decrease in brightness can be suppressed.

Second Embodiment
[Configuration of 3D image display device]
With reference to FIG. 6, the configuration of a three-dimensional image display device 1B according to the second embodiment will be described with respect to differences from the first embodiment.
The three-dimensional image display device 1B differs from the first embodiment in that it displays images in a time-division manner according to the polarization direction. As shown in Fig. 6, the three-dimensional image display device 1B includes a display means 2, a lens array 3B ( _3B1 , _3B2 ), a synchronization control device 4B, and a polarization switching element 5 ( ₅₁ , ₅₂ ). Note that the display means 2 is the same as in the first embodiment, and therefore a description thereof will be omitted.

First, the polarization switching element 5 will be described.
The polarization switching elements 5 are disposed in front of each lens array 3, and switch the polarization direction of light from the display means 2. Here, the polarization switching element ₅₁ is disposed in front of the lens array _3B1 , and the polarization switching element ₅₂ is disposed in front of the lens array _3B2 . Furthermore, the polarization switching element 5 switches the polarization direction to horizontal polarization or vertical polarization in response to a synchronization signal from a switching control means 40B, which will be described later.

The lens array 3B is provided for each depth display range so that the distance from the display means 2 is different. In this embodiment, two lens arrays 3B are provided, such as a lens array 3B ₁ close to the display means 2 and a lens array 3B ₂ far from the display means 2.

In addition, in the lens array 3B, the element lenses 30B are composed of a polarizing diffractive lens 31 and a convex lens 32. That is, in the lens array 3B, the polarizing diffractive lenses 31 and the convex lenses 32 as the element lenses 30B are two-dimensionally arranged. Here, the lens array _3B1 closer to the display means ₂ has a shorter lens pitch and the focal length of the element lenses 30B is shorter than that of the lens array 3B2 farther from _the display means 2. For example, the lens array _3B1 has twice the number of element lenses 30B as the lens array 3B2.

The polarized diffractive lens 31 is a lens whose focal length changes between positive and negative depending on the polarization direction. For example, the polarized diffractive lens 31 can be made of a periodically oriented liquid crystal polymer (Optica, Vol. 2, No. 11, pp. 958-964, November 2015). In addition, a polarized diffractive lens whose focal length changes between positive and negative depending on the direction of circular polarization instead of linear polarization may be used as the polarized diffractive lens 31. In this case, the polarization switching element 5 switches the light from the display unit 2 to right-handed circular polarization or left-handed circular polarization.
The convex lens 32 is disposed for each polarizing diffractive lens 31, and is, for example, a general convex lens.

The lens array 3B can be combined with a polarization switching element 5 arranged in front of it to switch between the lens state and the transmission state in the same way as in the first embodiment, as will be described in detail later.

The synchronization control device 4B synchronizes the display timing of the elemental image group with the switching timing of the lens state or the transparent state on a frame-by-frame basis, and includes a switching control means 40B and an image switching means 41. Note that the image switching means 41 is the same as in the first embodiment, so a description thereof will be omitted.

The switching control means 40B switches the state of the lens array 3B in a time-division manner so that one of the lens arrays 3B is in the lens state and the other lens array 3B is in the transmission state. In this embodiment, the switching control means 40B outputs a synchronization signal indicating the switching timing of the lens state or the transmission state to the polarization switching elements _5-1 , _5-2 so as to be synchronized with the image switching means 41. This allows the switching control means 40B to switch between a case where the lens array 3B- ₁ is in the lens state and the lens array 3B- ₂ is in the transmission state, and a case where the lens array 3B- ₁ is in the transmission state and the lens array 3B- ₂ is in the lens state.

[Switching between lens state and transmissive state]
The switching of the lens state or the transmission state in the lens array 3B will be described in detail with reference to FIG.

The polarizing diffraction lens 31 has the characteristic that its focal length switches between positive and negative depending on the polarization direction of the incident light beam. Here, the focal length of the convex lens 32 is f. Furthermore, the focal length of the polarizing diffraction lens 31 when a horizontally polarized light beam is incident is +f, and the focal length of the polarizing diffraction lens 31 when a vertically polarized light beam is incident is -f.

As shown in FIG. 7(a), when the polarization switching element 5 switches the polarization direction of the incident light to horizontal polarization, the incident light is focused at the focal length f/2 of the element lens 30B composed of the polarizing diffraction lens 31 and the convex lens 32. In other words, the lens array 3B is in a lens state and functions as a lens array.

On the other hand, as shown in FIG. 7(b), when the polarization switching element 5 switches the polarization direction of the incident light to vertical polarization, the focal length of the polarizing diffraction lens 31 is negative, so the lens action is cancelled out between the rear convex lens 32. In other words, the lens array 3B is in a transmissive state, and the incident light passes through without being refracted.

In the three-dimensional image display device 1B, the focal length of the polarizing diffraction lens 31 when a horizontally polarized light ray is incident may be -f, and the focal length of the polarizing diffraction lens 31 when a vertically polarized light ray is incident may be +f. In this case, when the polarization switching element 5 switches the polarization direction of the incident light to horizontal polarization, the lens array 3B is in a transmissive state, and the incident light passes through without being refracted. On the other hand, when the polarization switching element 5 switches the polarization direction of the incident light to vertical polarization, the lens array 3B is in a lens state and functions as a lens array.

[Action and Effects]
As described above, the three-dimensional image display device 1B can realize a multi-layer lens/transmission switching lens array by including a plurality of pairs of the lens array 3B, which is composed of the polarizing diffractive lens 31 and the convex lens 32, and the polarization switching element 5. As a result, the three-dimensional image display device 1B can reproduce a three-dimensional image B with high spatial resolution in the entire depth display range, as in the first embodiment. Furthermore, the three-dimensional image display device 1B has a simple configuration since it has only one display means 2, and the light of the elemental image group emitted from the display means 2 does not pass through other display means, so that a decrease in brightness can be suppressed.

Third Embodiment
[Configuration of 3D image display device]
With reference to FIG. 8, the configuration of a three-dimensional image display device 1C according to the third embodiment will be described with respect to differences from the second embodiment.
The three-dimensional image display device 1C differs from the second embodiment in that it has only one polarization switching element 5C. As shown in Fig. 8, the three-dimensional image display device 1C has a display means 2, a lens array 3C ( _3C1 , _3C2 ), a synchronization control device 4C, and a polarization switching element 5C. Note that the display means 2 is the same as in the second embodiment, so a description thereof will be omitted.

First, the polarization switching element 5C will be described.
The polarization switching element 5C is disposed between the display means 2 and the lens array _3C1 closest to the display means 2, and switches the polarization direction of the light from the display means 2. Note that the configuration of the polarization switching element 5C itself is similar to that of the second embodiment, so further description will be omitted.

Two lens arrays 3C are provided. Here, the lens array _3C2 , which is farther from the display means 2, is disposed after the lens array _3C1 , which is closer to the display means 2. Also, unlike the second embodiment, no polarization switching element is disposed between the lens arrays _3C1 and _3C2 .

In addition, the lens array 3C has element lenses 30C each composed of a polarizing diffractive lens 31 and a convex lens 32. That is, the lens array 3C has the polarizing diffractive lenses 31 and the convex lenses 32 arranged two-dimensionally as the element lenses 30C. Here, the lens array _3C1 closer to the display means 2 has a shorter lens pitch and a shorter focal length of the element lenses 30C than the lens array 3C2 farther from the display means _2. Note that the configuration of the lens array 3C itself is the same as that of the second embodiment, and therefore further description will be omitted.

The synchronization control device 4C synchronizes the display timing of the elemental image group with the switching timing of the lens state or the transparent state on a frame-by-frame basis, and includes a switching control means 40C and an image switching means 41. Note that the image switching means 41 is the same as in the first embodiment, so a description thereof will be omitted.

The switching control means 40C switches the state of the lens array 3C in a time-division manner so that one lens array 3C is in the lens state and the other lens array 3C is in the transmission state. In this embodiment, the switching control means 40C outputs a synchronization signal indicating the switching timing of the lens state or the transmission state to the polarization switching element 5C so as to be synchronized with the image switching means 41. This allows the switching control means 40C to switch between a case where the lens array _3C1 is in the lens state and the lens array _3C2 is in the transmission state, and a case where the lens array _3C1 is in the transmission state and the lens array _3C2 is in the lens state.

[Switching between lens state and transmissive state]
The switching of the lens state or the transmission state in the lens array 3C will be described in detail with reference to FIG.
9, the polarizing diffractive lenses 31 of the lens arrays _3C1 and _3C2 are designed so that the incident light and the emerging light to the lens array 3C are the same. The principle by which the element lens 30C is switched between the lens state and the transmitting state is the same as in the second embodiment.

9A, when the polarization switching element 5C switches the polarization direction of the incident light to horizontal polarization, the front lens array _3C1 is in a lens state and the rear lens array _3C2 is in a transmission state. That is, in the three-dimensional image display device 1C, the front lens array _3C1 functions as a lens array for horizontally polarized incident light.

9B, when the polarization switching element 5C switches the polarization direction of the incident light to vertical polarization, the front lens array _3C1 is in a transmitting state and the rear lens array _3C2 is in a lens state. In other words, in the three-dimensional image display device 1C, the rear lens array _3C2 functions as a lens array for vertically polarized incident light.

[Action and Effects]
In this way, the three-dimensional image display device 1C can realize a two-layer lens/transmission switching lens array by including two lens arrays _3C1 and _3C2 and one polarization switching element 5C. As a result, the three-dimensional image display device 1C can reproduce a three-dimensional image B with high spatial resolution in the entire depth display range, as in the second embodiment. Furthermore, in the three-dimensional image display device 1C, the light of the elemental image group emitted from the display means 2 does not pass through other display means, so that a decrease in brightness can be suppressed.

Furthermore, although the 3D image display device 1C cannot realize a lens/transmission switching lens array with three or more layers, it requires only one polarization switching element 5C, making the configuration simpler.

Although each embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiments, and also includes design modifications and the like within the scope of the gist of the present invention.
In the lens array, thinner diffractive lenses may be used instead of convex lenses.
As the polarization switching element, a liquid crystal panel having a high response speed such as an OCB type can be used.

In the first and second embodiments, it has been described that two lens arrays are provided, and two groups of elemental images corresponding to the depth display range of each lens array are displayed in a time-division manner, but this is not limited to the above. For example, the three-dimensional image display device may be provided with three or more lens arrays, and three or more groups of elemental images corresponding to the depth display range of each lens array may be displayed in a time-division manner.

In the first to third embodiments, the lens array closer to the display means has twice as many element lenses as the lens array farther from the display means, but this is not limited to this. For example, the lens array closer to the display means may have element lenses that are an integer multiple of 3 or more, or a decimal multiple, of the lens array farther from the display means.

Reference Signs List 1, 1B, 1C 3D image display device 2 Display means ₃ , 3 1, 3 ₂ Lens array 3B, 3B ₁ , 3B ₂ Lens array 3C, 3C ₁ , 3C ₂ Lens array 4, 4B, 4C Synchronization control device 5, _{5 1} , 5 ₂ Polarization switching element 5C Polarization switching element 9 Stereoscopic display device 30 Element lens 40, 40B, 40C Switching control means 41 Image switching means 90 Display device 91 Element lens 92 Lens array

Claims (5)

A three-dimensional image display device that displays a group of elemental images corresponding to a predetermined depth display range in a time-division manner,
a display means for displaying the element image group composed of element images;
a lens array that is configured by element lenses that are arranged two-dimensionally, and that can switch between a lens state in which the element lenses function as convex lenses and a transmission state in which the element lenses transmit light of the element images;
the lens array is provided for each of the depth display ranges so that the distance from the display means is different;
A three-dimensional image display device, characterized in that the lens array closer to the display means has a shorter distance between the element lenses and a shorter focal length of the element lenses than the lens array farther from the display means. The three-dimensional image display device according to claim 1, characterized in that the lens array is composed of liquid crystal lenses as the element lenses. Further, a polarization switching element is disposed in front of each of the lens arrays and switches the polarization direction of the light from the display means,
The lens array includes:
The three-dimensional image display device according to claim 1, characterized in that the element lenses are composed of polarizing diffractive lenses whose focal length changes positive and negative depending on the polarization direction, and convex lenses arranged for each of the polarizing diffractive lenses. a polarization switching element disposed between the display means and the lens array closest to the display means, for switching a polarization direction of light from the display means;
The lens array is provided in two pieces,
The three-dimensional image display device according to claim 1, characterized in that the element lenses are composed of polarizing diffractive lenses whose focal length changes positive and negative depending on the polarization direction, and convex lenses arranged for each of the polarizing diffractive lenses. a switching control means for switching the states of the lens arrays in a time division manner so that one of the lens arrays is in a lens state and the other lens array is in a transmission state;
a video switching means for displaying, in synchronization with the display means, the group of element images in a depth display range corresponding to the lens array in a lens state;
5. The three-dimensional image display device according to claim 1, further comprising:

Images