Electronic finder with reduced reflection caused by incoming light

• US 5,499,053 A
• Filed: 12/22/1993
• Issued: 03/12/1996
• Est. Priority Date: 12/25/1992
• Status: Expired due to Term

• Current Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Original Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Inventors: Itoh, Kazumi
• Primary Examiner(s): Harvey, David E.
• Application Number:
  US08/171,621
• Time in Patent Office: 811 Days
• Field of Search: 348/832, 348/751, 348/834, 348/759, 348/835, 348/761, 348/744, 348/766, 348/333, 348/795, 358/230, 358/231
• US Class Current: 348/333.08
• CPC Class Codes: G03B 13/02 Viewfinders
• CPC Class Codes: G03B 2213/025 Sightline detection

Abstract

An image observing apparatus capable of reducing reflections caused by incoming light. The apparatus includes an image display such as a liquid crystal cell with at least one optical system disposed between the image display and the observer'"'"'s eye. A polarizing element is disposed between the optical system and the observer'"'"'s eye. The apparatus is suited for use with electronic view finders, such as those used with video cameras. Because of the location of the polarizing element, incoming light and incoming light reflected from optical surfaces in the apparatus are decreased in intensity without any attenuation of the light forming the image. Thus, the visibility of the image is improved.

Claims

1. A finder comprising, in order from a side of incident light along an optical axis:

a liquid crystal display element including, in order along the optical axis;

a first polarizing element; and

a liquid crystal cell;

a lens unit that causes an image produced by said liquid crystal display element to enter an observer'"'"'s eye; and

a second polarizing element disposed between the observer'"'"'s eye and said lens unit for reducing reflected light incident on said lens unit from a side of said lens unit opposite said liquid crystal display element.

3. A finder according to claims 1 or 2, wherein polarizers located first farthest and second farthest from a light incidence surface of said liquid crystal display element are disposed so that transmission axes thereof are substantially parallel to each other.

4. A finder according to one of claims 1 or 2, wherein said lens unit consists essentially of a single glass lens.

2. A finder, comprising, in order along an optical axis:

a liquid crystal display element including, in order along the optical axis;

a first polarizing element;

a liquid crystal cell; and

a second polarizing element; and

a lens unit for causing an image produced by said liquid crystal display element to enter an observer'"'"'s eye;

wherein a third polarizing element is disposed on a side of said lens unit opposite said liquid crystal display element for reducing rays that are to be incident on said lens unit from the side of said lens unit opposite said liquid crystal display element.

5. A finder comprising, in order along an optical axis:

a liquid crystal display element comprising, in order along the optical axis;

a first polarizing element;

a first wave plate;

a liquid crystal cell;

a second wave plate; and

a second polarizing element; and

a lens unit for causing an image produced by said liquid crystal display element to enter an observer'"'"'s eye;

wherein each of said first wave plate and said second wave plate is constructed so as to produce a phase difference of (2n+1)λ

/4 between two components of a light wave transmitted therethrough polarized in respective directions parallel to a fast axis and a slow axis of said wave plates, said fast axis and said slow axis being perpendicular to each other, where n=0, 1, 2, 3, . . . and λ

represents a wavelength of said light wave.

6. A finder according to claim 5, wherein said first wave plate and said second wave plate are disposed so that directions of the fast axes thereof are one of parallel and perpendicular to each other and make an angle of 45°

with a transmission axis of said first polarizing element.

7. A finder comprising, in order along an optical axis:

a back light;

a first polarizing element;

a liquid crystal cell;

a second polarizing element; and

a lens unit for causing an image to enter an observer'"'"'s eye;

wherein said second polarizing element is obliquely disposed with respect to the optical axis with an angle θ

made by a normal line drawn to a surface of said second polarizing element facing said lens unit with the optical axis satisfying a condition;

space="preserve" listing-type="equation">(θ

.sub.1 +θ

.sub.2)/2<

θ

<

85°

where θ

₁ is an angle of incidence of a light ray entering an end of an image plane from an eyepoint in a plane including said normal line drawn to said surface of said second polarizing element and the optical axis, and θ

₂ is a minimum value of tan^-1 (hp+hl)/1, where P is a point of intersection of the ray entering the end of the image plane with said second polarizing element, H is a point of intersection of a perpendicular drawn from the intersection P to the optical axis with the optical axis, hp is a distance between the intersections P and H, and hl is a height from the optical axis to an apparatus frame on an opposite side of the intersection P with respect to the optical axis at a distance l from the intersection H in a range of distance between the intersection H and the eyepoint, so as to prevent light rays incident on said second polarizing element from a side of said second polarizing element opposite said liquid crystal cell and reflected from said second polarizing element from entering the observer'"'"' s eye via said lens unit.

8. A finder comprising, in order along an optical axis:

a back light;

a liquid crystal display element comprising, in order along the optical axis;

a first polarizing element;

a liquid crystal cell; and

a second polarizing element;

a lens unit for causing an image produced by said liquid crystal display element to enter an observer'"'"'s eye;

wherein said liquid crystal display element is obliquely disposed with respect to the optical axis with an angle θ

'"'"' formed by a normal line drawn to a surface of said liquid crystal display element facing said lens unit with the optical axis satisfying a condition;

space="preserve" listing-type="equation">(θ

.sub.1 '"'"'+θ

.sub.2 '"'"')/2<

θ

'"'"'

where θ

₁ '"'"' is an angle of incidence of a light ray entering a point at an end of an image plane of said liquid crystal display element from an eyepoint in a plane including said normal line drawn to said surface of said liquid crystal display element and the optical axis, and θ

₂ '"'"' is a minimum value of tan^-1 (hr+hm)/m, where R is the point at the end of the image plane of said liquid crystal display element, H'"'"' is a point of intersection of a perpendicular drawn from the point R to the optical axis with the optical axis, hr is a distance between the points R and H'"'"', and hm is a height from the optical axis to an apparatus frame on an opposite side of the point R with respect to the optical axis at a distance m from the intersection H'"'"' in a range of distance between the intersection H'"'"' and the eyepoint, so as to prevent light rays incident on said liquid crystal display element from a side of said liquid crystal display element on which said lens unit is disposed and reflected from said liquid crystal display element at least at one of said surface thereof facing said lens unit and interfaces disposed thereinside from entering the observer'"'"'s eye via said lens unit.