JP2003161915A - Electronic viewfinder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic viewfinder in which a visual field mask is not thermally damaged even when a solar ray reversely enters from an eyepiece optical system. <P>SOLUTION: The liquid crystal viewfinder is provided with a reflection type liquid crystal display element (1) which displays an image on a display screen (1a), a light emitting diode (LED) (8) which illuminates the display screen (1a), a diffusion plate (9), a polarization plate (10), an eyepiece (4) or the like with which the image on the display screen (1a) is enlarged to be observed, a polarizing beam splitter (PBS) sheet (3) which polarizes and separates an illuminating optical path and an eyepiece optical path, a visual field mask (2) which regulates the visual field of the finder between the PBS sheet (3) and the liquid crystal display element (1). The surface reflectivity for incident light to the visual field mask (2) is 20% or larger and the illuminating light emitted from the polarization plate (10) is linearly polarized before the incident on the PBS sheet (3). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic viewfinder (so-called EVF), for example, a camera used for photographing a still image or a moving image of a subject (for example, a digital camera, a video camera, a mobile phone, Personal computer, mobile computer,
An electronic viewfinder suitable for a camera built in or attached to an information portable terminal or the like, the electronic viewfinder (for example, a liquid crystal viewfinder) for projecting and displaying a two-dimensional image of a display element (for example, a liquid crystal display element) on the eye. It is about.

[0002]

2. Description of the Related Art In an optical finder, when an extremely high-intensity object (sun or the like) enters the field of view, the field mask is strongly illuminated by the surface reflection of the eyepiece. As a result, when the visual field mask shines brightly, a bright portion is generated outside the visual field and the finder quality is degraded. In order to prevent this, it is common to use a black field mask. Also, in a liquid crystal viewfinder, the viewfinder field is composed of a liquid crystal display element, so it is necessary to place a visual field mask on the eyepiece-side encapsulation glass of the liquid crystal display element in order to hide the liquid crystal encapsulation part. Field masks are commonly used.

[0003]

In order to increase the viewing angle and the high eye point of an EVF such as a liquid crystal viewfinder, it is necessary to increase the diameter of the eyepiece. However, when the diameter of the eyepiece lens is increased, if the sunlight is incident from the eyepiece lens, the sunlight collected by the eyepiece lens causes large heat damage (deformation etc.) to the black visual field mask with high light absorption rate. Will end up. A similar problem occurs in the conventional silver-salt film camera, but it is not a serious problem. For example, in the case of a single-lens reflex camera, the F-number is dark because the focal length of the eyepiece is long, and in the case of a lens shutter camera, the viewing angle is narrow.
The number is not so bright either.

In the EVF, the size of the display element is greatly reduced in order to reduce the cost and the size. In order to obtain a finder magnification corresponding thereto, it is necessary to shorten the focal length of the eyepiece optical system. In addition, it is desired that the viewing angle be larger than that of a finder for a lens shutter camera. Therefore, EVF is F
Since the number is bright (small), it is easy to be damaged by the sunlight. It should be noted that, although proposals regarding measures against thermal damage to polarizing plates and the like in liquid crystal viewfinders have been made in the past (Japanese Patent Laid-Open No. 9-127429).
No. 1, pp. 187-242, etc.), there is no known countermeasure for the thermal damage of the visual field mask.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electronic viewfinder in which the visual field mask is not damaged by the sun even when the sunlight is incident from the eyepiece optical system. To do.

[0006]

In order to achieve the above object, the electronic viewfinder of the first invention is a reflection type liquid crystal display device for displaying an image on a display surface, and an illumination optical system for illuminating the display surface. System, an eyepiece optical system for magnifying and observing an image on the display surface, and a polarized beam for polarization-separating an illumination optical path from the illumination optical system to the display surface and an eyepiece optical path from the display surface to the eyepiece optical system. What is claimed is: 1. A liquid crystal viewfinder, comprising: a splitter; and a field mask that regulates the field of view of the finder between the polarization beam splitter and the liquid crystal display element, the surface reflectance of incident light to the field mask being 20% or more. The illumination light emitted from the illumination optical system is linearly polarized before being incident on the polarization beam splitter.

An electronic viewfinder of a second invention is characterized in that, in the structure of the first invention, the visual field mask is made of metal.

An electronic viewfinder according to a third aspect of the invention is characterized in that, in the structure of the first or second aspect of the invention, the eyepiece side surface of the visual field mask is not a matte surface.

In the electronic viewfinder of the fourth invention, a display element for displaying an image on a display surface, an eyepiece optical system for magnifying and observing an image on the display surface, and an eyepiece optical system and the display element are provided. An electronic viewfinder comprising: a visual field mask that regulates the visual field of the viewfinder, wherein at least a field near the visual field of a surface on the eyepiece side of the visual field mask has a surface reflectance of 20% or more with respect to incident light,
It is characterized in that it is inclined by 15 degrees or more with respect to a plane perpendicular to the eyepiece optical axis.

An electronic viewfinder of a fifth invention is characterized in that, in the constitution of any one of the first to fourth inventions, the eyepiece optical system has a focal length of less than 20 mm.

[0011]

DETAILED DESCRIPTION OF THE INVENTION An electronic viewfinder (EVF) embodying the present invention will be described below with reference to the drawings.
Each of the embodiments of the liquid crystal viewfinder described below is a camera used for shooting a still image or a moving image of a subject.
EVF suitable for (digital cameras, etc.) but display element
The application is not limited to the EVF as long as it is a device that projects and displays a two-dimensional image of (for example, a liquid crystal display element) on the eye. For example, HM
It can also be used as an image display device such as a D (Head Mounted Display). In addition, the same reference numerals are given to the same or corresponding portions in the embodiments and the like, and the duplicate description will be appropriately omitted.

FIG. 1 shows an embodiment of a liquid crystal viewfinder, which is a separation part (EV) of an illumination optical path and an eyepiece optical path.
FIG. 2 shows an enlarged view of the F illumination section). 1 and 2, 1 is a reflective liquid crystal display element, 1a is a display surface, 2 is a visual field mask, 3 is a PBS (Polarizing Beam Splitter) sheet, and 4 is a
Is an eyepiece lens, 5 is a protective glass, 6 is a structural member, 7 is a lens barrel, 8 is an LED (Light Emitting Diode), 9 is a diffuser plate, 10
Is a polarizing plate and AX is an eyepiece optical axis. The PBS sheet (3), the diffusion plate (9), the polarizing plate (10), etc. are fixed to the structural member (6), and the three eyepieces (4) are fixed to the lens barrel (7).

The liquid crystal display element (1) displays a two-dimensional image on the display surface (1a). The display surface (1a) of the liquid crystal display element (1) is L
The ED (8) is illuminated by an illumination optical system composed of a diffuser plate (9) and a polarizing plate (10) that constitute illumination light with the emitted light from the ED (8). At this time, the radiated light emitted from the LED (8) is diffused by the diffuser plate (9) and transmitted through the polarizing plate (10) to be linearly polarized. This linear polarization is performed by PBS described later.
It is performed for polarization separation in the sheet (3), specifically, only the polarization component of the illumination light in the direction perpendicular to the paper surface is the polarizing plate (10).
Will be transmitted through. The illumination light source is not limited to the LED (8), and external light (sunlight or the like) outside the liquid crystal viewfinder may be used as the illumination light source.

The illumination light emitted from the polarizing plate (10) is unidirectional.
The light enters the cylindrical PBS sheet (3) curved in the direction of the long side of the screen here. The PBS sheet (3) is a polarization beam splitter that polarizes and separates the illumination optical path from the polarizing plate (10) to the display surface (1a) and the eyepiece optical path from the display surface (1a) to the eyepiece lens (4). A specific example thereof is DBEF (trade name) manufactured by Sumitomo 3M Limited. With this setting of the PBS sheet (3), S-polarized light (polarized light component perpendicular to the paper surface) of the incident light on the PBS sheet (3) is reflected (FIG. 2), and P-polarized light (polarized light component parallel to the paper surface). ) Is transparent. However, the illumination light emitted from the polarizing plate (10) is PBS
Since the S-polarized light reflected by the sheet (3) is linearly polarized (before entering the eyepiece optical path), all the illumination light incident on the PBS sheet (3) is reflected. In addition, PB
The S sheet (3) not only has a polarization separation function, but also has a curved cylindrical shape (a spherical shape may be used if necessary).
Since it also functions as a condenser lens, it contributes to weight reduction, size reduction, and cost reduction of the illumination optical system.

The illumination light (S-polarized light) reflected by the PBS sheet (3) passes through the opening (H) of the field mask (2) and then enters the display surface (1a) of the liquid crystal display element (1). . This liquid crystal display element
(1) is a method of modulating illumination light (S-polarized light) whose polarization directions are aligned by selective polarization control according to the display of each pixel (that is, ON / OFF for each pixel) of a two-dimensional image, and two types of polarized light The reflected light composed of (P-polarized light and S-polarized light) is emitted. That is, the liquid crystal display element
Each pixel forming the display surface (1a) of (1) rotates the polarization direction of incident light (S-polarized light) by 90 degrees when ON, and reflects light.
(P-polarized light) is emitted, and when OFF, the reflected light (S-polarized light) is emitted in the same polarization state without rotating the polarization direction of the incident light (S-polarized light). FIG. 2 shows an optical path in which an ON-state pixel rotates the polarization direction of incident light (S-polarized light) by 90 degrees and emits reflected light (P-polarized light).

The PBS sheet (3) transmits the reflected light (P-polarized light) from the ON-state pixel and reflects the reflected light (S-polarized light) from the OFF-state pixel. Therefore, it is emitted from the display surface (1a) of the liquid crystal display element (1) and the aperture of the visual field mask (2).
Of the reflected light (P-polarized light, S-polarized light) that has passed through (H), only the reflected light (P-polarized light) from the ON pixel is in the PBS sheet (3).
(FIG. 2), and enters the eyepiece lens (4) as image light. 3 eyepieces (4) and protective glass
The eyepiece optical system (focal length: 10 mm) composed of (5) guides the image light to the pupil (EP) to magnify and observe the two-dimensional image of the display surface (1a). In the two-dimensional image, ON-state pixels are observed bright (white), and OFF-state pixels are dark (black).
To be observed.

The viewfinder field of the two-dimensional image observed as described above is restricted by the field mask (2) disposed between the PBS sheet (3) and the liquid crystal display element (1). . The field mask (2) is a stainless steel plate (S
US430, thickness: 0.1 mm). The surface of the field mask (2) on the side of the eyepiece optical system (4,5) is mirror-finished with a metallic luster so as to maintain the polarization state of the incident light (not a matte surface). The surface reflectance for the incident light is 20% or more. In addition,
Here, the plate-shaped metal visual field mask (2) is fixed on the sealing glass of the liquid crystal display element (1), but even if the visual field mask (2) is configured by metal deposition on the surface of the sealing glass. Good.

When the focal length of the eyepiece optical system (4,5) is short as in this embodiment, the F number is inevitably small. Therefore, in order to prevent the visual field mask (2) from being seriously damaged by heat (deformation or the like) even if sunlight is incident back from the eyepiece optical system (4,5), it is necessary to take measures against heat damage. The visual field mask (2) used in the present embodiment is
Since the surface reflectance for incident light is 20% or more, the heat generation and temperature rise due to the concentrated sunlight is largely suppressed (less than half that when using a black field mask) to prevent the thermal damage. be able to. Moreover, since the high reflectance material used is a metal (here, SUS430),
Due to the cooling effect due to the good heat conduction of the metal material and the high heat resistance of the metal material, it is possible to completely prevent heat damage due to reverse incidence of sunlight. Therefore, it is possible to take the optimum countermeasure against heat damage required by the balance between the metal material forming the visual field mask (2) and the surface reflectance of 20% or more. This heat damage countermeasure is a visual field mask (2)
In consideration of the amount of heat collected in, the focal length of the eyepiece optical system (4, 5) is optimal for the EVF configuration of less than 20 mm.

In the liquid crystal viewfinder as in the present embodiment, the viewfinder field is composed of the liquid crystal display element (1), and therefore, an object brighter than the illumination of the display surface (1a) (an extremely high brightness object such as the sun) ) Never enters the field of view. Therefore, the visual field mask (2) does not shine brightly and the viewfinder quality is not deteriorated due to the surface reflection of the eyepiece lens (4). Further, as described above, even if the surface reflectance of the visual field mask (2) is high, the light reflected by the visual field mask (2) causes the eyepiece lens.
Since it does not enter the (4), the field mask (2) does not shine brightly and the viewfinder quality is not degraded. This will be described in more detail with reference to FIG.

As shown in FIG. 3, the illumination light (S-polarized light) emitted from the polarizing plate (10) is reflected by the PBS sheet (3) and the field mask (2).
Even when the liquid crystal display element (1) is reflected on the surface, the polarization direction does not rotate and the polarization state (S polarization) is maintained as in the OFF state pixel display (black display) of the liquid crystal display element (1). Therefore, the illumination light is P
It cannot pass through the BS sheet (3) and the field mask (2)
Will be observed black. Illumination light is PBS sheet
The polarization state is maintained even when reflected by (3), because the PBS sheet (3) is set to reflect only S-polarized light and the illumination light from the polarizing plate (10) This is because it is linearly polarized (only S-polarized light is emitted) in the polarization direction reflected in 3). Also, even if the illumination light is reflected by the visual field mask (2), its polarization state is maintained only in the visual field mask (2).
This is because the surface of the sheet is a mirror surface, and therefore, the light directly incident on the field mask (2) from the polarizing plate (10) and reflected therefrom cannot pass through the PBS sheet (3). In addition,
If the surface of the field-of-view mask (2) is a matte surface, the polarization state may change during reflection and pass through the PBS sheet (3). Therefore, the surface of the field-of-view mask (2) should be a mirror surface. desirable.

As described above, the use of polarized light for image display E
With the VF configuration, even if the surface reflectance of the visual field mask (2) is high, it is possible to prevent the light reflected by the visual field mask (2) from being emitted to the eyepiece (3) side rather than the PBS sheet (3). Which allows the visual field mask (2) to appear black. Further, in the liquid crystal viewfinder of the present embodiment, external light (sunlight or the like) is applied from the eyepiece side while observing an image.
Even if the light enters in the opposite direction, the light will be transmitted through the PBS sheet (3) at least twice before it enters the eye, and the amount of light will be less than half that in the case without the PBS sheet (3).
Therefore, in view of the fact that the peep part of the viewfinder is shielded by the face, the field mask (2) is observed as a black color with a brightness that is hardly noticeable. In addition, it is desirable that the lens surface of the eyepiece lens (4) is subjected to a vapor deposition treatment for reflection prevention or the like, if necessary.

FIG. 4 shows another embodiment of the liquid crystal viewfinder. In FIG. 4, 11 is a transmissive liquid crystal display element, 11a is a display surface, 12 is a field mask, 12a is a field near the field, and 18 is a backlight. The liquid crystal display element (1) displays a two-dimensional image on the display surface (1a), and the display surface (1a) is illuminated from the back side by the backlight (18). Display surface (1a)
The eyepiece optical system (4,5) for magnifying and observing the two-dimensional image is composed of three eyepieces (4) and a protective glass (5) as in the embodiment of FIG. In order to prevent the light of the backlight (18) from being reflected on the surface of the eyepiece (4) and the reflected light illuminating the field mask (12) to appear white, all the lens surfaces of the eyepiece (4) Is subjected to an anti-reflection vapor deposition process.

The visual field mask (12) for controlling the finder visual field between the eyepiece lens (4) and the liquid crystal display element (11) is a resin molded product whose surface is vapor-deposited with Al (aluminum). is there. Also, the eyepiece optical system (4,5) of the visual field mask (12)
On the side surface, there is a near field part (12
a) is formed so as to surround the opening (H) corresponding to each side of the viewfinder field. When external light (sunlight, etc.) is incident from the eyepiece optical system (4,5), the incident light is reflected by the field mask (1
The area (12a) near the field of view 2) is reached. Therefore, Al
It suffices that the vapor deposition process is performed at least in the field-of-view vicinity portion (12a), and the surface reflectance in the field-of-view vicinity portion (12a) may be 20% or more with respect to the incident light. Near field of view (1
By setting the surface reflectance to the incident light of 2a) to 20% or more, the heat generation and the temperature increase due to the concentrated sunlight are significantly increased as in the embodiment of FIG. 1 (half that in the case of using the black visual field mask). The following can be suppressed to prevent the thermal damage. This measure against heat damage is optimal for an EVF configuration in which the focal length of the eyepiece optical system (4,5) is less than 20 mm, considering the amount of heat collected in the visual field mask (2).

Further, the eyepiece optical system (4,5) of the visual field mask (12)
The near field part (12a) of the side surface is inclined by 15 degrees or more with respect to a plane perpendicular to the eyepiece optical axis (AX) (here, θ = 45).
Every time). Field of view near the plane perpendicular to the optical axis (AX)
If the inclination angle θ of (12a) is less than 15 degrees, the eyepiece optical system
There is a possibility that external light that is incident back from (4,5) may be visible depending on the position of the eye. As in the present embodiment, if the visual field vicinity portion (12a) is composed of an inclined surface and the inclination angle θ with respect to the plane perpendicular to the eyepiece optical axis (AX) is 15 degrees or more, the eyepiece optical system (4,5 Even if the external light is incident from the back side), the back incident light is prevented from directly entering the eye.

The above-described embodiments include inventions having the following configurations. An electronic device including a display element for displaying an image on a display surface, an eyepiece optical system for magnifying and observing the image on the display surface, and a visual field mask for restricting a finder visual field between the eyepiece optical system and the display element. In the viewfinder, the eyepiece-side surface of the visual field mask has a portion having a surface reflectance with respect to incident light of 20% or more, and a lens surface constituting the eyepiece optical system is subjected to antireflection treatment. An electronic viewfinder that features With this configuration, it is possible to prevent the heat damage and prevent the visual field mask from being illuminated by the reflected light from the eyepiece lens surface and appearing white.

[0026]

As described above, according to the present invention, since the surface reflectance of the visual field mask is high, it is possible to prevent the visual field mask from being damaged by heat even if the sunlight is incident from the eyepiece optical system. You can If the field mask is made of metal,
With the cooling effect due to the good heat conduction of the metal material and the high heat resistance of the metal material, it is possible to more efficiently prevent heat damage due to the reverse incidence of sunlight.

[Brief description of drawings]

FIG. 1 is an optical sectional view showing an embodiment of a liquid crystal viewfinder.

FIG. 2 is an enlarged cross-sectional view showing an optical path separation portion in the liquid crystal viewfinder of FIG.

FIG. 3 is an enlarged cross-sectional view for explaining the reason why the field mask looks black in the liquid crystal viewfinder of FIG.

FIG. 4 is an optical sectional view showing another embodiment of the liquid crystal viewfinder.

[Explanation of symbols]

1 ... Reflective liquid crystal display element 1a… Display surface 2… Field mask 3… PBS sheet (polarizing beam splitter) 4 ... Eyepiece (eyepiece optical system) 8… LED 9… Diffuser (illumination optical system) 10… Polarizing plate (illumination optical system) 11 ... Transmissive liquid crystal display element 12… Vision mask 12a ... near field of view H ... opening AX ... Eyepiece optical axis EP ... Hitomi

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02F 1/13357 G02F 1/13357 2H091 G03B 11/00 G03B 11/00 2H099 13/06 13/06 5C022 H04N 5 / 225 H04N 5/225 B F term (reference) 2H018 AA32 2H044 AJ06 2H083 AA06 AA30 EE30 2H087 KA03 KA14 LA12 PA03 PA17 PB03 QA02 QA07 QA14 QA22 QA25 QA32 QA42 QA45 RA42 2H088 EA10 EA25 HA14 HA20 HA21 MA20 2H091 FA10X FA15X FA34X FA45X LA03 LA04 MA02 MA10 2H099 AA11 BA17 CA02 CA07 CA11 5C022 AC03 AC09 AC61

Claims (5)

[Claims] 1. A reflective liquid crystal display device for displaying an image on a display surface, an illumination optical system for illuminating the display surface, an eyepiece optical system for magnifying and observing an image on the display surface, and the illumination optical system. A polarization beam splitter that polarizes and separates the illumination optical path to the display surface and the eyepiece optical path from the display surface to the eyepiece optical system, and a field of view that limits the viewfinder view between the polarization beam splitter and the liquid crystal display element. A liquid crystal viewfinder, comprising: a mask; and a surface reflectance of 20% with respect to light incident on the field mask.
The electronic viewfinder as described above, characterized in that the illumination light emitted from the illumination optical system is linearly polarized before entering the polarization beam splitter. 2. The electronic viewfinder according to claim 1, wherein the field mask is made of metal. 3. The electronic viewfinder according to claim 1, wherein the eyepiece side surface of the visual field mask is not a matte surface. 4. A display element for displaying an image on a display surface, an eyepiece optical system for magnifying and observing an image on the display surface, and a visual field mask for regulating a viewfinder visual field between the eyepiece optical system and the display element. An electronic viewfinder comprising: a visual field mask, wherein at least a portion near a visual field of a surface on the eyepiece side has a surface reflectance of 20% or more with respect to incident light, and a plane perpendicular to the optical axis of the eyepiece. An electronic viewfinder that is inclined by 15 degrees or more. 5. The electronic viewfinder according to claim 1, wherein the eyepiece optical system has a focal length of less than 20 mm.