JP2001324741A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image pickup device which is equipped with an electronic view finder using a reflection type liquid crystal display element suitable to a camera, and whose photographing range is easily grasped, and which is made small in size and which can be tightly held so as to suppress a shake. SOLUTION: The device is provided with a photographing optical system, an imaging device for receiving a luminous flux guided from the photographing optical system, an image display element, a controller for converting image information from the imaging device to a display signal, a light source for illuminating the image display element and an observation optical system, the focal distance of the observation optical system satisfies the condition of (1) 13 mm<f<21 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus provided with an electronic viewfinder using a reflection type liquid crystal display element suitable for cameras such as silver halide cameras and digital cameras.

[0002]

2. Description of the Related Art Many silver halide cameras and digital cameras are
It has a means for recording an image by the photographing optical system and an observation optical system for confirming the photographing range. As a means for recording an image, a chemical reaction on a film surface is used in the case of a silver halide camera, and information obtained by photoelectric conversion by an electronic imaging device such as a CCD is used in the case of a digital camera.

[0003] On the other hand, an observation optical system which guides a light beam from a subject side to an observer side and forms an image on a retina of an observer's eye to observe an image to be photographed is often used. I have.

[0004] This type of observation optical system may be shared with an imaging optical system for forming an image for recording a part of the incident side, and may not be shared. A specific example of the former is a single-lens reflex camera. In the latter example, a real image finder having an objective optical system, an image erecting means, and an eyepiece optical system, which is particularly suitable for a zoom optical system, is mounted on many products. These may be collectively referred to as an optical finder.

[0005] In addition to the optical viewfinder, the digital camera is equipped with an electronic viewfinder that displays an image on an LCD (Liquid Crystal Display) and allows the observer to directly see the image to see the range of influence. Many have been commercialized. Many digital cameras equipped with both an optical viewfinder and an electronic viewfinder have been commercialized.

[0006]

In recent years, miniaturization of a camera, high zoom ratio of a zoom lens, and cost reduction have become strong. When a real-image finder is mounted on such a high-magnification camera, the finder also needs to have a high-magnification. For this reason, the size of the viewfinder becomes large and the structure becomes complicated,
And this leads to higher costs.

In the case of a taking lens, a retractable lens system allows the camera to be compact when the lens system is stored. However, a retractable retractable viewfinder restricts the design and complicates the mechanism. The camera on which it is mounted is unknown.

On the other hand, a single-lens reflex camera type camera does not have a problem of a zoom ratio, but requires a mechanism for dividing an image forming optical path and an observation system optical path. For this reason, the mechanism becomes complicated, and in the case of light quantity division, the light quantity becomes small, and the arrangement of the optical system after the light division is restricted, and there is a problem that the camera becomes large.

Further, a camera of the type that directly looks at the LCD needs to keep the eye of the observer and the LCD at a clear distance of about 25 cm, which is not preferable in terms of holding the camera. Particularly, in the case of a small digital still camera having a high image quality and a high zoom ratio, there is a problem that the image quality is deteriorated due to a blur at the telephoto end.

A so-called EVF (Electronic View Finder) for observing a virtual image through a small LCD through an eyepiece has been proposed, but this is based on a transmissive LCD. Transmissive LCD as image display device for EVF
Have drawbacks such as a low aperture ratio and conspicuous black matrix between pixels.

On the other hand, as a conventional example of an image display device using a reflection type LCD, US Pat.
No. 20 and JP-A-2000-10041 are known. Japanese Patent Application Laid-Open No. 2000-10041 is known as a type to be mounted on the observer's head. These are optical systems having a wide field of view to obtain a sense of reality. However, these are unsuitable as observation systems used in cameras.

The present invention is an imaging apparatus provided with an electronic viewfinder using a reflection type liquid crystal display element suitable for a camera. The imaging apparatus can be held in a small size that allows an observer to easily grasp a shooting range and is hard to cause blurring. It is intended to provide a simple imaging device.

[0013]

An image pickup apparatus according to the present invention comprises an image pickup optical system, an image pickup element for receiving a light beam guided by the image pickup optical system, an image display element for displaying an image, and an image pickup element. A controller for converting the obtained image information into a signal that can be displayed on the image display element, a light source that emits illumination light guided to the image display element, and an observation optical system for guiding the image to the observer's eyes. The image display device is a reflection type image display device that displays an image by reflecting illumination light, and the observation optical system satisfies the following condition (1). (1) 13 mm <f <21 mm where f is the focal length of the observation optical system.

The distance between the surface of the observation optical system on the observer side and the pupil of the observer is approximately determined in consideration of the frame holding the observation optical system, the shape of the camera body, the shape of the observer's face, glasses, and the like. 1
Desirably 3 mm to 21 mm, about 15 mm to 20 mm
It is more preferable if it is on the order. In addition, since the reflection type liquid crystal display element has a characteristic of substantially regular reflection of illumination light, it is necessary to illuminate almost vertically in order to perform efficient illumination, and the luminous flux illuminated vertically is higher than that of the liquid crystal display element. Inject almost vertically. In order to guide this light flux to the pupil of the observer so that the periphery cannot be efficiently removed, it is preferable that the rear focal position of the observation optical system be near the pupil of the observer.

If the focal length f of the observation optical system exceeds the lower limit of 13 mm of the condition (1), a lens layout is required such that the rear principal point position of the observation optical system is closer to the pupil side of the observer than the optical system. In order to ensure good image performance, the configuration of the optical system must be complicated, which is not preferable. If the upper limit of 21 mm is exceeded, the distance between the liquid crystal display element and the position of the pupil of the observer on the optical axis must be increased, and the camera cannot be reduced in size.

In the above-described image pickup apparatus of the present invention, the incident optical axis of the photographing optical system and the exit optical axis of the observation optical system are substantially parallel, and the direction of the light beam entering the photographing optical system and the light beam emerging from the observation optical system. Are desirably substantially the same.

In order to take a picture with less camera shake,
It is desirable that the observer face the direction of the subject, hold the body firmly, and photograph the periphery of the observation portion in a stable posture with the periphery of the eye or eyeglasses. For this purpose, the incident optical axis of the photographing optical system and the emission optical axis of the observation optical system as described above are substantially parallel, and the light beam entering the photographing optical system and the light beam exiting from the observation optical system are in substantially the same direction. Desirably. The direction of the light beam emitted from the observation optical system may be adjusted according to the photographing conditions.

Further, in the photographing apparatus of each of the above structures,
When the diagonal length of the display portion of the image display element is d, it is desirable that the following condition (2) is satisfied. (2) 4mm <d <6mm

It has been found that, in the photographing apparatus, the viewing angle can be easily confirmed when the viewing angle is about 14 ° to 20 °.

If the condition (1) is satisfied and the lower limit of the condition (2) is exceeded, the viewing angle becomes narrow, and the size of the subject within the photographing range becomes small, making it difficult to understand the situation. If the value exceeds the upper limit of the condition (2), the size of the image display device becomes large, which is not preferable. In addition, the viewing angle becomes too wide, so that the photographing range cannot be checked quickly, so that it cannot be understood at a glance.

Further, in the photographing apparatus of the present invention, the reflection type image display device is capable of color display, and the observation optical system is configured to include at least one positive lens and at least one negative lens. Is preferred.

Since the observation optical system includes at least one positive lens and at least one negative lens, the chromatic aberration can be corrected well with a small number of components, and the principal point position can be easily controlled, and the observation can be performed. The principal point position can be determined in consideration of the distance between the observer-side surface of the optical system and the observer's pupil, the position of the image display device, and the viewing angle.

That is, by arranging the negative lens and the positive lens in order from the pupil side of the observer, the distance on the optical axis between the image display apparatus and the observer side of the observation optical system can be increased, and the luminous flux of the illumination system can be increased. The arrangement of the positive lens and the negative lens in this order from the observer's pupil side reduces the diagonal length of the display unit of the image display element while maintaining the viewing angle in a desired range, and performs imaging. The device can be miniaturized.

In the image pickup apparatus according to the present invention, a light beam from a light source is made incident on the image display element, and at least the first, second, and third light beams are emitted from the image display element and directed to the observation optical system. A prism having three surfaces is arranged, a light beam emitted from the illumination light enters the prism from the first surface, and the incident light beam exits from the second surface and is reflected by a (reflection-type) image display element. The light beam reflected by the display element is again incident on the prism from the second surface, is further reflected on the first surface, exits from the third surface, passes through the observation optical system, and is guided to the observation eye. It is desirable to make it.

That is, an image pickup apparatus according to another second configuration of the present invention comprises an image pickup optical system, an image pickup element for receiving a light beam from the image pickup optical system, an image display element for displaying an image, and an image pickup element for the image pickup element. A controller that converts image information into a signal that can be displayed on the image display element, a light source that is guided by the image display element and emits illumination light, and observation that guides an image displayed on the image display element to the observer's eyes. An optical system, wherein the image display element is a reflection type image display element, and the light source, the reflection type image display element and the observation optical system constitute an electronic view finder, and at least the first and the second in the electronic view finder.
A prism having three surfaces of a second surface and a third surface, the prism causing the light beam from the light source to enter the first surface, and causing the light beam incident from the first surface to exit from the second surface; The light beam emitted from the second surface is reflected by the reflection type image display device and made incident again from the second surface, and the light beam incident from the second surface is reflected at least on the first surface and then emitted from the third surface. This is configured to be guided to an observer's eye via an observation optical system, and further satisfy the above condition (1).

In general, it is necessary to separate the illumination light beam incident on the reflection type image display device from the light beam of the observation optical system. Further, by reducing the space between the surface of the observation optical system on the observer side and the reflective image display device, the size of the imaging device can be reduced.

Therefore, by arranging the prism as described above, the first reflection surface, which is a means for separating the illumination light beam and the observation light beam, and the number of times of reflection of the illumination light beam and the observation light beam inside the prism are increased. The illumination light is not attenuated, and the observation light flux is obtained while securing the optical path length between the observer side surface of the observation optical system and the reflection type image display element, which is necessary to satisfy the necessary viewing angle and eye relief. The passing space can be reduced.

The first surface of the prism is formed of a polarizing half mirror that transmits a light component in a specific polarization direction and reflects light in a polarization direction substantially perpendicular to the polarization direction. A display element using a twisted nematic liquid crystal is preferable.

Such a configuration is desirable because it allows efficient separation of the illumination light beam and the observation light beam.

If at least one of the entrance surface, the exit surface, and the reflection surface of the prism arranged in the above-described electronic viewfinder is a curved surface, a part of the power of the observation optical system can be borne by the curved surface. Although the system can be miniaturized, it is easy to make a prism if it is constituted only by a plane.

In the image pickup apparatus having the second configuration, it is preferable that the incident optical axis of the photographing optical system and the exit optical axis of the observation optical system are substantially parallel to each other for the same reason as in the first configuration.

Also in the second configuration, it is desirable that the condition (2) is satisfied, for the same reason as in the first configuration.

In the image pickup apparatus of the present invention, it is preferable that the photographing optical system has a zoom ratio of 7 or more and 20 or less.

When the zoom ratio of the photographing optical system is 7 or more, it is difficult to reduce the size by using a conventional optical real-image finder. Therefore, if an electronic viewfinder as in the present invention is used, even an imaging device having a zoom ratio of 7 or more can be configured to be small and effective. On the other hand, if the zoom ratio is less than 7, it is more desirable to mount an optical viewfinder than to mount an electronic viewfinder in consideration of the size and power consumption of the photographing device. Therefore,
In the image pickup apparatus of the present invention equipped with an electronic viewfinder, the zoom ratio of the photographing optical system is preferably 7 or more. If the zoom ratio of the photographing optical system exceeds 20, even if the holding is improved by using an electronic viewfinder, a blur that easily affects the image quality is likely to occur, and a liquid crystal display element for direct observation that does not have an observation optical system is used. An electronic viewfinder is more desirable.

Note that the zoom ratio for performing zooming by a so-called electronic zoom method that narrows the angle of view using a part of the information from the image sensor is not included in the zoom ratio of the original photographing optical system. That is, the number of pixels involved in image formation decreases with zooming on the telephoto side, the image quality becomes coarse, and the permissible blurring value increases.

For the above reasons, it is preferable to use an electronic viewfinder in the case of an image pickup apparatus having a zoom photographing optical system having an optical zoom ratio of 7 to 20 by the photographing optical system. Of course, an imaging device using the above-described electronic viewfinder may have an electronic zoom function.

In the image pickup apparatus of the present invention, it is preferable that the diagonal length of the image pickup device is not less than 3.5 mm and not more than 23 mm.

In a single-lens reflex camera, an observer observes a primary image formed by a photographing optical system. In this case, it is necessary to erect the image, that is, to invert the image right and left and up and down, respectively, and the position of the primary image is restricted by the layout of the photographing optical system.

If the effective diagonal length of the image pickup device is smaller than 3.5 mm, the image quality will be poor, and it is desirable to use a liquid crystal display device for direct viewing. If it exceeds 23 mm, a single-lens reflex type layout is more effective.

In the image pickup apparatus of the present invention, it is desirable that the effective image pickup area of the image pickup device satisfies the following condition (3). (3) 1.0 × 10 ⁻⁴ <p / d _I <6.0 × 10 ⁻⁴ where d _I is the diagonal length of the effective imaging area, and p is the center interval (image pitch) of horizontal pixels.

Condition (3) is a condition for the number of pixels in the horizontal direction for obtaining high image quality. It is considered that the resolution of the human eye is particularly high in the horizontal direction. If the value exceeds the upper limit of the condition (3), the image becomes coarse and cannot be said to be of high image quality. When the value exceeds the lower limit of the condition (3), the pixel becomes too small, and a sufficient light amount cannot be obtained. Further, the effect of improving image quality cannot be obtained due to the influence of diffraction. Alternatively, in order to obtain the required pixel size, the entire image sensor becomes large, and accordingly, the photographing optical system becomes large, and the image pickup apparatus becomes large. In addition, the size of the entire image pickup device such as a CCD greatly affects the cost of the image pickup device such as a CCD, which increases the cost.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the imaging apparatus according to the present invention will be described.

FIG. 1 is a diagram showing the configuration of a digital camera which is an example of the image pickup apparatus of the present invention.

In FIG. 1, reference numeral 10 denotes a digital camera which is an image pickup device, which includes an image pickup optical system 1, a filter 2, and an image pickup device 3.
, A controller 4, a built-in memory 5, an electronic viewfinder 6, and an interface 7.

In the above-described image pickup apparatus, light emitted from an object point forms an object image on a light receiving surface of an image pickup device 3 such as a CCD by a photographing optical system 1 composed of an optical element (a lens or the like). The image pickup device 3 is composed of a group of photoelectric conversion devices arranged regularly, and a filter 2 having a low-pass effect is disposed between the photographing optical system 1 and the image pickup device 3 in order to prevent a moiré phenomenon caused thereby. Further, an infrared cut filter for cutting infrared light may be provided.

The light beam incident on the image pickup device 3 is converted into an electric signal by the photoelectric conversion device and input to the controller 4. Signal processing such as gamma correction and image compression processing is performed by the controller 4 and output to the personal computer 9 or the like via the built-in memory 5 or the interface 7.

The controller 4 communicates with the reflection type image display device (not shown in FIG. 1), and captures an image via the electronic viewfinder 6 including the illumination type reflection type image display device system and the observation optical system. It is configured such that an observer can observe an image to be obtained or a photographed image. Further, image data can be sent from the built-in memory 5 to the auxiliary memory 8. On the other hand, the same image data is transmitted from the interface to the personal computer 9.
Can be sent to

FIG. 2 shows a configuration in the case where the imaging apparatus of the present invention is applied to a silver halide camera.

As shown in FIG. 2, a silver halide camera 20 equipped with an image pickup apparatus of the present invention comprises a photographing optical system 11 and a film 12.
, An objective lens 13 and an imaging device 14 such as a CCD,
Controller 15 and another second controller 16
And a built-in memory 5 and an electronic viewfinder 6 as in the digital camera of FIG.

The silver halide camera 20 shown in FIG. 2 forms an object image by forming a light beam from an object point on the film 12 by the photographing optical system 11.

The luminous flux emitted from the object point is imaged by another objective lens 13 different from the photographing optical system 11 so as to form a CC.
An object image is formed on the imaging device 14 such as D. The luminous flux incident on the image sensor 14 is converted into an electric signal by a photoelectric conversion element constituting the image sensor, and is converted into an electric signal by the first controller 15.
Is input to The first controller 15 performs signal processing such as gamma correction and image compression processing and sends the signal processing to the reflection type image display device. The electronic view finder 6 having a configuration including an illumination system, a reflection type image display device, and an observation optical system is provided. An image to be photographed via the camera can be observed by a photographer.

On the other hand, the photographer can observe the captured image using the information and the like stored in the built-in memory 5 by the controller 15.

The second controller 16 is for controlling the photographing optical system, and outputs information such as zooming and focusing of the photographing optical system to the first controller based on a signal from the second controller 16. The information may be recognized at 15 and adjusted according to the angle of view of the image displayed on the reflective image display device. Alternatively, information such as focusing of the photographing optical system may be recognized by the second controller, and correction of the range of the image displayed on the reflective display element (parallax correction) may be performed. Also, a signal from the first controller 15 is sent to the built-in memory 5 or an interface (not shown),
This may be output to a personal computer or the like.

The luminous flux of the photographing optical system is divided for a finder without using the objective lens 13, and an image is formed on an image pickup device 14 such as a CCD using the divided luminous flux for a finder. The observation may be performed based on the image.

The photographing optical system shown in FIGS. 1 and 2 is preferably a zoom lens having a zoom ratio of 7 or more, for example. It is further desirable that the zoom ratio is 20 or less.

It is desirable that the photographing optical system satisfies the following conditions. 0.5 mm <d _I <23 mm 1.0 × 10 ⁻⁴ <p / d _I <6.0 × 10 ⁻⁴

The digital camera of FIG. 1 described above or FIG.
The photographing optical system used in the silver halide camera shown in FIG.
It has the following data. f = 5.864 to 15.901 to 58.871, F / 2.80 to F / 3.26 to F / 3.68 2ω = 30.5 ° to 11.9 ° to 3.2 °, zoom ratio 10 r₁ = 59.315 d₁ = 1.42 n₁ = 1.84666 ν₁ = 23.78 r_Two = 27.477 d_Two = 6.07 n_Two = 1.67790 ν_Two = 55.34 r_Three = -4021.223 d_Three = 0.10 r_Four = 24.395 d_Four = 3.71 n_Three = 1.72916 ν_Three = 54.68 r_Five = 67.210 d_Five = D₁ (Variable) r₆ = 60.579 d₆ = 0.95 n_Four = 1.80610 ν_Four = 40.92 r₇ = 7.551 d₇ = 4.92 r₈ = -27.873 d₈ = 0.85 n_Five = 1.51633 ν_Five = 64.14 r₉ = 9.394 d₉ = 2.97 n₆ = 1.84666 ν₆ = 23.78 r_Ten= 30.690 d_Ten= D_Two (Variable) r₁₁= ∞ (aperture) d₁₁= D_Three (Variable) r₁₂= 13.716 (aspherical surface) d₁₂= 3.24 n₇ = 1.69350 ν₇ = 53.20 r₁₃= -220.124 d₁₃= 0.10 r₁₄= 6.966 d₁₄= 2.00 n₈ = 1.72342 ν₈ = 37.95 r_Fifteen= 24.874 d_Fifteen= 0.85 n₉ = 1.84666 ν₉ = 23.78 r₁₆= 5.372 d₁₆= D_Four (Variable) r₁₇= -28.096 d₁₇= 1.00 n_Ten= 1.80518 ν_Ten= 25.42 r₁₈= 105.630 d₁₈= 0.10 r₁₉= 9.700 (aspherical surface) d₁₉= 3.11 n₁₁= 1.58918 ν₁₁= 61.25 r₂₀= -13.116 d₂₀= D_Five (Variable) r_{twenty one}= ∞d_{twenty one}= 3.50 n₁₂= 1.51633 ν₁₂= 64.14 r_{twenty two}= ∞d_{twenty two}= 1.00 r_{twenty three}= ∞ (imaging surface) Aspheric coefficient (twelfth surface) k = 1.416, A_Four = -1.02903 × 10^-Four , A₆ = -4.90876 × 10^-7 A₈ = -3.41834 x 10^-8 (Section 19) k = 0.489, A_Four = -4.555746 x 10^-Four, A₆ = 0, A₈ = 0 f 5.864 15.901 58.871 D₁ 0.80 10.91 19.99 D_Two 20.94 10.77 2.20 D_Three 4.74 1.29 0.80 D_Four 3.75 5.42 11.17 D_Five 6.60 8.43 2.86 d_I10 mm, p; 35 μm, p / d_I= 3.5 × 10^-Four , D = 5.1mm where r₁ , R_Two , R_Three , ... is the half curvature of each surface of the lens
Diameter, d₁ , D_Two , D_Three,... Are the thickness of each lens and the sky
Qi interval, n₁ , N_Two , ... is the refractive index of each lens, ν₁ ,
ν_Two ,... Are Abbe numbers of each lens. This data etc.
Where r₁, R_Two , ..., d₁ , D_Two , ... etc.
The unit of the length is mm.

The aspherical surface in the above-described photographing optical system is expressed by the following equation when the optical axis direction is the x axis and the direction perpendicular to the optical axis is the y axis.

In the above equation, r is the radius of curvature of the reference spherical surface, and k, A ₄ , A ₆ and A ₈ are aspherical coefficients.

Next, the electronic viewfinder used in the present invention will be described.

FIG. 3 shows a typical example of an electronic viewfinder according to the present invention. In FIG.
Is an illumination optical system, 23 is an observation optical system, 24 is an observation optical system 2
3 is an optical axis, 25 is an observer's eye, 26 is an image display element, 2
Reference numeral 7 denotes a plane-parallel plate on which the polarization half mirror 28 is provided.

The finder having such a configuration is provided with the light source 2.
The illumination light from No. 1 is reflected by an illumination optical system 22 composed of a reflecting mirror and emitted in one direction (upward in the figure). The optical axis 24 of the observation optical system 23 is configured to intersect perpendicularly at substantially the center of the image display device.

The illumination light emitted from the light source 21 and reflected by the illumination optical system 22 constituted by a reflecting mirror and emitted in one direction has the center of the light beam substantially perpendicular to the optical axis 24 of the observation optical system 23. The light travels so as to intersect, and is reflected by the half mirror 28 toward the image display element 26.

The image display element 26 is a reflection type twisted nematic liquid crystal display element, and the twist angle of this display element is set to 45 °. The image display elements used in other embodiments described later with reference to FIGS. 4 to 6 are the same.

The image displayed on the reflective display element is
The light passes through a flat plate 27 provided with a polarization half mirror 28 and is observed by an observer via an observation optical system 23.

In the electronic viewfinder having such a configuration, when the polarization state of the illumination light emitted from the light source 21 is random, the illumination light becomes linearly polarized light of a certain polarization direction by the polarization half mirror 28, and the liquid crystal display element Illuminate 26. For example, the polarization half mirror 28 reflects the s-wave and
When the wave is set to be transmitted, the illumination light reflected on the half mirror surface 28 is an s-wave. The reflected illumination light that illuminates the liquid crystal display element 26, which is an image display element, passes through the pixel to which the voltage is applied, passes through the liquid crystal layer, and is reflected at a lower portion thereof, whereby the polarization direction is rotated by 90 ° and emitted. I do. Therefore, the image display device 2
The illumination light that has been modulated into 6 and emitted exits as a p-wave. The p-wave light enters the flat plate 27 again, and almost all of the light passes through the polarization half mirror and passes through the observation optical system 23.
And reaches the observer's eye 25 via.

As described above, the electronic viewfinder used in the present invention has a simple configuration, does not cause a small loss of the amount of light emitted from the light source 21, and is a small and lightweight finder that can effectively use light. I can do it. Further, the observer enlarges the image on the image display element 26 and perceives it as a virtual image by the operation of the observation optical system. In this case, the light beam emitted from the light source 21 is reflected by the polarization half mirror surface 28.
The illumination light path which is reflected by the image display element 26 and enters the image display element 26, and the light flux which is reflected by the image display element 26 passes through the polarization half mirror surface and is guided to the observer's eyes by the polarization half mirror surface It is desirable to configure the electronic viewfinder so as to form a reciprocating optical path between the electronic viewfinder and the image display element. With this configuration,
The illumination optical path inside the observation optical system can be used for both the forward path and the return path. Compared to the case where both optical paths are different optical paths inside the optical system, useless optical elements (transmission surface and reflection surface) and Space can be saved, and the imaging device can be made compact. It also helps prevent flare light.

In the finder shown in FIG. 3, the illumination optical system may be arranged in the optical system transmitting the half mirror, and the observation optical system may be arranged in the optical system reflecting the half mirror.

The viewing optical system 23 of the electronic viewfinder shown in FIG. 3 is constituted by a single positive lens having a focal length of 17 mm, an image display element having a display section having a diagonal length d of 5.1 mm, and a viewing angle. (2ω) is 13.7 ° in the horizontal direction and 1 in the vertical direction
The configuration was 0.4 ° and 17 ° in the diagonal direction, and a light beam having a diameter of 4 mm was guided to the pupil of the observer.

FIG. 4 shows a configuration similar to that of the electronic viewfinder shown in FIG. 3, in which the observation optical system 23 includes a negative lens L1 and a positive lens L2. This observation optical system also has a focal length of 17 mm and a diagonal length d of the image display element of 5.1 mm.

The electronic viewfinder shown in FIG. 4 uses a lens having one more observation optical system 23 as compared with the electronic viewfinder of FIG. 3, but the space of the electronic viewfinder can be reduced as is clear from the drawing. .

The observation optical system of the finder shown in FIG. 4 has a negative lens and a positive lens arranged from the image display element side. However, the image display element is separated from the observation optical system from the layout of the entire camera body. In the case of arrangement, a positive lens and a negative lens may be arranged in order from the image display element side.

In the viewfinders shown in FIGS. 3 and 4, an aspherical surface may be provided in the observation optical system.

FIG. 5 shows another example of the electronic viewfinder used in the image pickup apparatus according to the present invention, in which a prism is arranged in the viewfinder and a half mirror is provided on the prism. In the figure, reference numeral 30 denotes a prism having surfaces 31, 32, and 33. A polarization half mirror is provided on the surface 31, and the image display element 2 is provided near the surface 32 substantially parallel thereto.
6 are arranged, and the observation optical system 23 is
The optical axis 24 is arranged.

In the electronic viewfinder having the configuration shown in FIG. 5, the light beam emitted from the illumination optical system enters the prism 30 from the surface 31, and the illumination light beam emitted from the surface 32 almost perpendicularly to the surface is The light enters the image display element 26. The luminous flux emitted from the image display element 26 enters the surface almost perpendicularly from the surface 32, is reflected by the surface 31, and is further reflected by the surface 32.
And is emitted from the surface 33 almost perpendicularly to this surface. The light beam emitted from the prism 30 in this manner is
The light enters the eyeball 25 of the observer via the observation optical system 23 and is observed.

FIG. 6 shows another example of an electronic view finder using a prism, in which a half mirror is similarly applied to the prism. That is, the prism 40 is disposed in the finder, and the prism 40 has optical surfaces 41, 42, and 43, of which the polarizing half mirror is provided on the surface 41. In addition, the image display element 26 is disposed near the surface 42 substantially in parallel with the surface 42,
The surface 43 is disposed substantially perpendicular to the optical axis 24 of the observation optical system 23.

In the electronic viewfinder shown in FIG. 6, the light beam emitted from the illumination optical system
0, is totally reflected by the surface 43, and exits from the surface 42 almost perpendicularly to the surface to illuminate the image display element 26. The light beam emitted from the image display element 26 is incident on the surface again almost perpendicularly from the surface 42, is totally reflected by the surface 43, and is reflected by the surface 41.
Are reflected at the surface 42, and are totally reflected at the surface 42, and are emitted from the prism 40 from the surface 43 perpendicularly to this surface. The light emitted from the prism 40 is guided to the eyes of the observer via the observation optical system 23, and the observer observes the image.

The electronic viewfinder shown in FIG. 6 has a structure in which the light beam arranged in the viewfinder is bent a plurality of times, so that the space can be effectively used and the image pickup apparatus can be made smaller. In addition, since the light beam can pass almost perpendicularly to the entrance surface, the exit surface, and the exit surface to the observation optical system with respect to the image display element, asymmetric aberration hardly occurs.

In these electronic viewfinders including a prism, since the illumination light beam does not include image information, the light beam incident on the prism entrance surface from the illumination system does not need to be perpendicularly incident on the entrance surface. The light may be incident obliquely.

Further, power may be given to the entrance surface of the prism, which can contribute to aberration correction and downsizing of the finder. Further, by giving power to a surface other than the total reflection surface, aberration correction becomes easier.

In the above-described embodiment, a combination of a polarization half mirror and a reflection type twisted nematic liquid crystal display device has been described as an example, but the present invention is not limited to this. For example, a half mirror and another reflective liquid crystal display device may be used. However, considering the brightness of an image and the like, the configuration described in the embodiment is desirable.

Incidentally, in addition to the imaging device having the structure described in each claim of the claims, the structure described in each of the following claims can achieve the object of the present invention.

(1) The image pickup apparatus according to claim 1, wherein the reflective image display element is capable of color display, and the observation optical system includes at least one positive lens and at least one positive lens. An imaging device comprising: a plurality of negative lenses.

(2) The imaging apparatus according to claim 1, 2, or 3 or (1),
An electronic viewfinder including a light source, an image display device, and an observation optical system includes a prism having at least three surfaces, a first surface, a second surface, and a third surface, and illumination light emitted from the light source is transmitted to the first surface. The illumination light incident from the surface, the illumination light incident from the first surface is emitted from the second surface to illuminate the reflective image display element, and the light reflected by the reflective image display element is incident again from the second surface, An imaging apparatus characterized in that the light is emitted from at least a third surface after being reflected by at least a first surface, and is guided to an observer's eye via an observation optical system.

(3) In the imaging device described in the above item (2), the first surface of the prism is formed of a polarization half mirror that transmits light having a specific polarization direction and reflects light having a polarization direction substantially orthogonal to the specific polarization direction. An imaging apparatus, wherein the reflective image display element is an electronic display element using a reflective twisted nematic liquid crystal.

(4) In the image pickup apparatus according to claim 1, 2 or 3 or (1), (2) or (3), the zoom ratio of the photographing optical system is 7 to 20. An imaging apparatus, which is 20.

(5) In the image pickup apparatus according to claim 1, 2 or 3, or (1), (2), (3) or (4), the diagonal length of the image pickup element is An imaging device characterized by being 3.5 mm or more and 23 mm or less.

(6) The image pickup apparatus described in claims 1, 2 or 3 or (1), (2), (3) or (4), wherein the following condition (3) is satisfied: An imaging device, comprising: (3) 1.0 × 10 ⁻⁴ <p / d _I <6.0 × 10 ⁻⁴

[0089]

According to the present invention, by providing an electronic viewfinder using a reflection type image display device suitable for a silver halide camera or a digital camera, an observer can easily grasp the photographing range, and is small and blurred. It is possible to realize an imaging device capable of holding which is less likely to cause the problem.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a digital camera which is an example of an imaging apparatus of the present invention.

FIG. 2 is a diagram showing a configuration of a silver halide camera which is another example of the imaging apparatus of the present invention.

FIG. 3 is a diagram illustrating an example of an electronic viewfinder used in the imaging apparatus of the present invention.

FIG. 4 is a practical example of the viewfinder shown in FIG.

FIG. 5 is a diagram showing an example of an electronic viewfinder having a prism used in the image pickup apparatus of the present invention.

FIG. 6 is a diagram showing another example of an electronic viewfinder having a prism used in the imaging apparatus of the present invention.

FIG. 7 is a diagram showing a configuration of a photographing optical system used in the imaging apparatus of the present invention.

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Claims (3)

[Claims] An imaging device for receiving a light beam guided by the imaging optical system; an image display device for displaying an image; and image information obtained from the imaging device. A controller that converts the display light into a displayable signal, a light source that emits illumination light guided to the image display element, and an observation optical system that guides an image to an observer's eyes, wherein the image display element emits the illumination light An imaging apparatus, which is a reflection-type image display element that displays an image by reflected light, wherein a focal length f of the observation optical system satisfies the following condition (1). (1) 13mm <f <21mm 2. An incident optical axis of the photographing optical system and an emission optical axis of the observation optical system are substantially parallel, and a direction of a light beam incident on the photographing optical system and a direction of a light beam emerging from the observation optical system are different. 2. The imaging device according to claim 1, wherein the directions are substantially the same. 3. The imaging apparatus according to claim 1, wherein the following condition (2) is satisfied. (2) 4 mm <d <6 mm where d is the diagonal length of the display section of the image display device.