JPS5832362B2 - camera viewfinder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical system for capturing a finder image of a camera.

When performing remote photography or the like in which the camera is operated at a location away from the location where the camera is installed, it is necessary to capture an image in order to check the image on the finder.

However, in a normal camera finder, the eyepoint is usually located 10 to 20 mm behind the eyepiece, and if a normal lens is used for imaging, mechanical interference between the street frame and the front frame of the imaging lens may occur. occurs.

Therefore, it becomes difficult to match the pupil position of the imaging lens and the eye point of the finder system, and as a result, the captured image may have insufficient light in the peripheral areas, or in the worst case, part of the image may be vignetted. Also occurs.

Figure 1 shows the above-mentioned state, where 1 is a photographing lens, 2 is a movable mirror, 3 is a film, 4 is a focusing plate, 5 is a condenser lens, 6 is a pentaprism, and 7 is an eyepiece. These constitute the optical system of a normal still camera.

Further, 8 is an imaging lens of an imaging device attached to the methyl camera, and 9 is an entrance pupil of this imaging lens.

P indicates the eye point of the eyepiece 7, which does not coincide with the entrance pupil 9 and causes the above-mentioned inconvenience.

On the other hand, if the focal length of the imaging lens is not appropriately selected, only a portion of the finder image may be captured, or a portion other than the peripheral image may be captured.

An object of the present invention is to obtain a good image in which the peripheral part does not become dark and a part of the image does not become keratinized.

For this purpose, the following conditions are set.

(1) The entrance pupil of the imaging lens must be within ±5 mm from the eye point of the camera's finder.

This condition (1) is a condition to ensure that the amount of light in the peripheral area of the image capturing screen is not insufficient, and FIG. 2 shows a case where such an eye point P and the entrance pupil 9 coincide.

Here, (+) is taken in the direction far from the viewfinder.

In practice, it may be more than 5 steps in the (-) direction.

If this condition (1) is not met, an insufficient amount of light in the periphery or a clutter will occur.

Also, as a second condition, as shown in Figure 3, here φF=image size of finder image.

fF: Combined focal length of finder eyepiece and condenser lens.

φ■: Image size of the imaging screen.

fI: Focal length of the imaging lens.

This (7) im2) is a condition for capturing a finder image in an appropriate size.

However, since the above condition is 100% satisfied, from a practical point of view, no problem will occur if it is within ±20%.

Furthermore, when the light flux exiting the eyepiece is adjusted afocal, the following relationship holds true. Therefore, if the aspect ratio of the viewfinder image is the same as that of the imaging screen, if f□ is selected as described above, the entire viewfinder image will be It is possible to image the range.

However, in reality, the light flux that exits the Niha Ibis is not afocal, and due to incidental conditions such as the difference in the aspect ratio of the screen and the simultaneous imaging of information outside the screen, the required fI is selected within the range of (2). It's satisfying.

An embodiment of the present invention will be described below with reference to FIG.

R in the figure: Radius of curvature of each lens refractive surface D: Axial thickness or air gap N of each lens: Refractive index (with respect to the d-line) v of each lens component glass:
Atsbe's number of each lens component glass If the distance on the optical axis between the camera's finder eye point and the entrance pupil of the imaging lens is O, then φF = 4197 fF-68,89669 φ knee 11.0 fI = 18.48713- or more The present invention is an effective optical system that satisfies the above-mentioned conditions and can capture a finder image well.

[Brief explanation of drawings]

FIG. 1 shows a case where the eye point does not match the entrance pupil when an imaging lens is attached to the optical system of a still camera, and FIG. 2 shows a case where they do. FIG. 3 is a diagram showing the relationship between φF, φ■, fF-fI. FIG. 4 is a configuration diagram and an optical path diagram of one embodiment. In the figure, 7...Eyepiece, P...-Eye point, 8...Imaging lens, 9...
This is the entrance pupil of the imaging lens.

Claims (1)

[Scope of Claims] 1. In a camera having a photographic lens and a finder optical system for observing a first object image formed by a light beam passing through the photographic lens, an image pickup device is provided on the viewing side of the finder optical system. a second object image from the first object image by the finder optical system and the imaging lens;
When capturing an object image and recording the first object image on a recording material disposed within the camera while observing the second object image, the imaging lens is positioned relative to the eye point of the finder optical system. The entrance pupil of is within +5 mm on the optical axis, and φF is the size of the first object image, fF is the focal length of the finder optical system, and φ■ is the size of the second object image. , wherein the finder optical system and the imaging lens are set so that fI is the focal length of the imaging lens.