JP2000089337A - Display device within finder picture plane for camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device within a finder picture plane for a camera performing ideal display luminance control within a picture plane by more strictly calculating the brightness of a finder picture plane than in the conventional manner. SOLUTION: This display device is provided with an interchangeable photographing lens, an interchangeable focusing glass 11 provided on the focal plane of a finder, a photometric element 16 performing the photometry of light from an object, and a light emitting body 15 forming a display picture within the finder picture plane, and the finder picture and the display picture are superposed to be observed. In this case, the light emitting state of the light emitting body 15 is controlled in accordance with a photometric value by the element 16, the open aperture F-number information of the mounted photographing lens, and correction information based on the diffusion characteristic of the mounted focusing glass 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device in a finder screen of a camera which performs high-luminance display in a finder screen.

[0002]

2. Description of the Related Art Conventionally, in a single-lens reflex camera in particular, for example, a shutter speed, an F number, and the like are displayed outside a viewfinder screen by a light emitting element such as an LED. In this case, the display luminance of the off-screen display is changed based only on the photometric value obtained by the photometric means of the camera in order to maintain the balance with the brightness in the finder screen.

[0003]

However, when a high-brightness display such as a bright frame is performed in the finder screen to indicate, for example, an auto-focusing distance measurement area, the dynamic brightness (brightness) in the finder screen is increased. Since the range is wide, it is necessary to considerably and finely change the display luminance as compared with the above-mentioned off-screen display.

In other words, the brightness of the viewfinder screen varies greatly depending on the subject, and also varies depending on the open F-number of the photographic lens to be exchanged even with the same photometric value. However, if a display method in which the display luminance is merely changed based only on the photometric value by the photometric means is adopted, the control for performing the display in the viewfinder screen becomes insufficient, and the brightness of the screen and the display luminance are not sufficiently controlled. The balance may not be attained, and the display may be very difficult for the photographer to see.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a finder in-screen display device for a camera which calculates the brightness of a finder screen more strictly than before and performs ideal in-screen display brightness control. The purpose is to do.

[0006]

In order to achieve the above object, the present invention provides an interchangeable photographing lens, an interchangeable focusing plate provided on a finder focal plane, and a photometric means for measuring light from a subject. And a luminous body that forms a display image in a finder screen, wherein the finder image and the display image are superimposed and can be observed. The light emitting state of the luminous body is controlled in accordance with the open F number information and correction information based on the diffusion characteristics of the mounted reticle.

[0007] The luminous state of the luminous body to be controlled is
The configuration is a light emission luminance or a drive duty ratio.

Further, when the reticle is replaced with a reticle having a different diffusion characteristic, there is provided a detecting means for detecting this, and correction information based on the diffusion characteristic is changed based on a detection result.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side sectional view schematically showing a finder optical system according to one embodiment of the present invention. In the figure, reference numeral 11 provided at the lowermost part is provided on a finder focal plane and projects a subject image from a photographic optical system (not shown), a condenser lens 12 above the condenser plate, and a condenser lens 13 above the condenser lens. Is a pentaprism, and 14 on the right side is an eyepiece optical system. 15 at the upper left of the pentaprism 13 is L
A light-emitting element such as an ED, and 16 at the upper right is a photometric element.

In the above configuration, light from the subject image projected on the focusing screen 11 passes through the inside of the pentaprism 13 as shown by an optical path A indicated by a dashed line, and is connected to an eyepiece optical system 14.
And observed by a photographer (not shown). on the other hand,
Similarly, light from the subject image enters the prism 17 through another path inside the pentaprism 13 as shown by an optical path B represented by a solid line, and is guided to the photometric element 16. Further, light from the light emitting body 15 is expressed by an optical path C represented by a solid line,
The light passes through the pentaprism 13 through the condenser lens 18 and the prism 19 and is guided to the eyepiece optical system 14, which is also observed by a photographer (not shown).

Here, the pentaprism 13 and the prism 1
9, a half mirror is formed, whereby light from the subject image (optical path A) and light from the luminous body 15 (optical path C) are combined, and a double image is taken (superimposed). Becomes The light from the light-emitting body 15 performs a bright frame-like high-brightness display at the center of the finder screen as shown in FIG. This represents, for example, the distance measurement areas 1, 2, and 3 from the left. In the figure, only this high-luminance display is taken out and shown. Normally, as shown in FIG. 3, a ranging frame 20 representing the entire ranging area is shown in the center of the finder screen. This shows a marking groove provided on the focusing screen 11.

FIG. 4 shows the positional relationship between the distance measuring frame 20 and the distance measuring areas 1 to 3. Actually, only the distance measurement area corresponding to the subject whose distance has been automatically measured, or the distance measurement area set by the photographer and automatically measured is displayed. Specifically, as shown in FIGS. 5 to 7, only the distance measurement areas 1, 2, and 3 are displayed.

FIGS. 8 and 9 are views showing the surface of the reticle 11, showing a standard reticle and an exchange reticle, respectively. These have different diffusion characteristics of the diffusion surface 11a on which the subject image is projected, and can be used interchangeably for convenience in photographing. On one side in front of each focusing screen 11, a knob 11b for attaching and detaching to and from a camera body (not shown) is provided. The projection 11c is provided only on one side on the right side of the exchange reticle shown in FIG. Thereby, the type of the reticle 11 is distinguished.

FIG. 10 is a front sectional view schematically showing a mounting mechanism of the focusing screen 11. FIG. 2 illustrates a state in which an exchange reticle is attached. As shown in the figure, a reticle 11 is provided at the lowermost part, and this is a reticle holder 2.
1 is attached. A condenser lens 12 is provided above the pentaprism, and a pentaprism 13 is further provided above the condenser lens 12. These are attached to a finder base plate 22. A reticle detection switch 23 is provided on the right side of the reticle holder 21 to detect the type of the reticle 11.

The procedure for mounting the reticle 11 is as follows. First, a photographic lens (interchangeable lens) (not shown) on the lower front side of the figure is removed, and the reticle holder 21 is viewed from the front while the reticle holder 21 is looking through the camera body. The plate 11 is inserted into the reticle holder 21, and then the knob 11b shown in FIG.
It is done by picking and lifting. At this time, the reticle detection switch 23 is operated by the projection 11c provided on the exchange reticle.

More specifically, as shown in an enlarged view of the reticle detection switch 23 and its surroundings in FIG.
As a result, the contact piece 23a of the reticle detection switch 23 is pushed up and separated from the contact piece 23b, so that the reticle detection switch 23 is turned off. As a result, it is detected that the replacement reticle is attached. When the standard reticle is attached, the projection 23c does not exist, so that the contact piece 23a remains in contact with the contact piece 23b, and the reticle detection switch 23 is kept on.

FIG. 12 is a graph showing the relationship between the open AV of the taking lens and the finder brightness D. Here, the open AV refers to the AV (Aperture Val) when the aperture of the taking lens (interchangeable lens) having each F number (FNO.) Is opened.
ue), and is represented by AV = 2 log ₂ (FNO.). By the way, AV = 1, 2, 3, 4, 5, and 6 correspond to F1.4, F2, F2.8, F4, F5.6, and F, respectively.
8 is supported. The finder brightness D indicates the amount of decrease in brightness when the standard focusing screen is mounted and the aperture of the photographing lens at F1.4 is opened as a reference, and is expressed in units EV.

In the figure, as shown in the legend, a curve obtained by connecting the measured values indicated by ◆ when the standard reticle is attached, a solid line obtained by linearly approximating the curve, and ■ when the exchange reticle is attached.
Are drawn together with a curve obtained by joining the actually measured values and a broken line obtained by linearly approximating the curve. As shown in the figure, when each of the focusing screens is mounted, when the open AV is a small value, the finder brightness hardly changes, but after a certain value, the brightness rapidly decreases. These relationships are established when the photometric value of the photometric element 16 is constant. Such a relationship is approximated by a straight line with a polygonal line as shown in FIG. As described above, by performing the linear approximation, it is possible to calculate the finder brightness with a simple operation and with sufficient practicality.

FIG. 13 is a flowchart showing a procedure for calculating the finder brightness based on the above-described linear approximation and calculating the display brightness in the distance measurement area by the light emitting body 15 based on the calculation result. In the figure, when the calculation is started, first, in step # 5, it is determined whether or not the reticle detection switch 23 (represented by SSW) is off. If it is determined that the camera is mounted, the process proceeds to step # 10.

In step # 10, the AV is 3.75.
It is determined whether or not: This is because, as shown in FIG. 12, in the linear approximation when the standard focusing screen is mounted, the open AV when the finder brightness D becomes 0 is obtained.
It comes from the range. The value of the open AV is transmitted from the attached photographing lens (interchangeable lens) to the camera body. If the AV is not less than 3.75, the process proceeds to step # 15.

In step # 15, as described herein, the finder brightness D is calculated based on the equation representing the shaded area a in the linear approximation when the standard reticle is mounted as shown in FIG. You. That is, opening A in this range
D is obtained by substituting the value of V. Also, in step # 10, if the AV is 3.75 or less,
The process proceeds to step # 20, where D = 0 as described above.

On the other hand, in step # 5,
ff, and if it is determined that the interchangeable reticle is attached, the process proceeds to step # 25. In step # 25, it is determined whether or not the AV is 2.625 or less. This is because, as shown in FIG. 12, in the linear approximation when the exchange reticle is attached, the finder brightness D is-
It comes from the range of the open AV when it becomes 0.125. The value of the open AV is transmitted from the attached photographing lens (interchangeable lens) to the camera body. If the AV is not equal to or less than 2.625, the process proceeds to step # 30.

In step # 30, as described herein, the finder brightness D is calculated based on the equation representing the shaded portion b in the linear approximation when the exchange reticle is attached as shown in FIG. You. That is, opening A in this range
D is obtained by substituting the value of V. If it is determined in step # 25 that the AV is equal to or less than 2.625, the process proceeds to step # 35, where D = −0.
125.

When the finder brightness D is obtained as described above, the process proceeds to step # 40, for example, a switch (see FIG. 2 and the like) for switching the distance measuring areas 1 to 3 to a mode in which the photographer himself selects. It is determined whether or not the AFSW (represented by AFSW, not shown) is off. In step # 45, the photometric element output BVC at the position corresponding to the automatically selected distance measuring area
By adding the finder brightness D to n ′, that is, subtracting the amount of decrease in brightness, the finder brightness BVfn after correction in the distance measurement area is obtained.

Here, the positional relationship between the distance measuring area and the photometric element in this embodiment will be described. As shown in FIG. 14, on the finder screen, the numbers (1) to (13) of the respective cells in the photometric element 16 are displayed. (6), (7) and (8)
Distance measurement areas 1, 2, 3 indicated by 5 correspond to each other. That is, in the equation described in step # 45, the cell numbers n '= 6, 7, and 8 of the photometric elements correspond to the numbers n = 1, 2, and 3 of the distance measuring areas, respectively.

At step # 40, AFSW is turned off.
If the mode is not f but on and the photographer selects the ranging area, the process proceeds to step # 50. In step # 50, the average value of the outputs of the respective photometric elements corresponding to the distance measurement area is determined and set as BVave. However, in the equation described here, n is the number of distance measurement areas, and in the present embodiment, n = 3. Then, the process proceeds to step # 55, in which the finder brightness D is added to the average value BVave of the photometric element outputs, that is, the amount of decrease in brightness is subtracted, thereby obtaining the corrected finder brightness BVfn in the distance measurement area. Can be

As a result, the brightness of the display of each distance measuring area in the finder screen becomes uniform. This is because, in the mode in which the photographer selects the ranging area, when the ranging area is frequently switched, the display brightness of the ranging area is also switched corresponding to the finder brightness in each ranging area. In this case, the photographer gives a sense of incongruity (the eyes flicker).

When the corrected finder brightness BVfn is obtained as described above, the process proceeds to step # 60, where the driving of the light emitter 15 is performed based on the quadratic function of BVfn as described herein. The duty ratio is obtained by logarithm,
End the calculation. Alternatively, the light emission luminance of the light emitting body 15 may be obtained. FIG. 15 is an example of a graph showing the relationship between BVfn and the duty ratio. Here, assuming that BVfn on the horizontal axis is a variable x and the duty ratio on the vertical axis is a variable y, the quadratic function shown in FIG. The duty ratio here is a value obtained by converting the logarithm of the base of 2 to an EV.

Another example of obtaining the duty ratio from BVfn is shown in Table 1 below. This is BVfn
The table of the duty ratio corresponding to the predetermined range is created in advance, and the brightness of the display in the finder screen is determined based on the table.

[0030]

[Table 1]

[0031]

As described above, according to the present invention,
Calculates the brightness of the viewfinder screen more strictly than before,
It is possible to provide a finder in-screen display device for a camera that performs ideal in-screen display brightness control.

[Brief description of the drawings]

FIG. 1 is a side sectional view schematically showing a finder optical system.

FIG. 2 is a diagram showing a state in which high-luminance display is performed on a finder screen.

FIG. 3 is a view showing a state in which a distance measurement frame is displayed on a finder screen.

FIG. 4 is a diagram showing a positional relationship between a ranging frame and a ranging area.

FIG. 5 is a diagram showing a state in which a distance measurement area 1 is displayed on a finder screen.

FIG. 6 is a view showing a state in which a distance measurement area 2 is displayed on a finder screen.

FIG. 7 is a diagram showing a state in which a distance measurement area 3 is displayed on a finder screen.

FIG. 8 is a diagram showing the surface of a standard reticle.

FIG. 9 is a diagram showing the surface of an exchange reticle.

FIG. 10 is a front sectional view schematically showing a focusing mechanism of the focusing screen.

FIG. 11 is an enlarged view showing a reticle detection switch and its periphery.

FIG. 12 is a graph showing the relationship between open AV and viewfinder brightness.

FIG. 13 is a flowchart showing a procedure for calculating viewfinder brightness and display brightness.

FIG. 14 is a view for explaining a positional correspondence between a distance measuring area and a photometric element.

FIG. 15 is an example of a graph showing a relationship between BVfn and a duty ratio.

[Explanation of symbols]

 1-3 Distance measuring area 11 Focusing plate 12, 18 Condenser lens 13 Pentaprism 14 Eyepiece optical system 15 Light emitting body 16 Photometric element 17, 19 Prism 20 Distance measuring frame 21 Focusing plate holder 22 Viewfinder base plate 23 Focusing plate detecting switch

Claims (3)

[Claims] An interchangeable photographing lens, an interchangeable focusing plate provided on a finder focal plane, a light meter for measuring light from a subject, and a light emitter for forming a display image in a finder screen. And a display device in a finder screen of a camera that enables observation by superimposing a finder image and the display image, wherein a photometric value by the photometric unit, open F-number information of the mounted photographing lens, and the mounted A display device in a finder screen of a camera, wherein a light emitting state of the light emitting body is controlled according to correction information based on diffusion characteristics of the focusing screen. 2. The display device according to claim 1, wherein the light emission state of the light emitter to be controlled is light emission luminance or a drive duty ratio. 3. When the reticle is replaced with a reticle having a different diffusion characteristic, detection means for detecting the change is provided, and correction information based on the diffusion characteristic is changed based on a detection result. A display device in a finder screen of a camera according to claim 1 or 2.