JPH02183239A - Camera - Google Patents

Abstract

PURPOSE:To make the range finding frame in a finder meet a range finding spot position by providing an objective optical system which is variable in power at part of a real-image finder, a half-mirror which has wavelength selectivity in the optical path of the objective optical system, and a light emitting means behind the half-mirror. CONSTITUTION:The wavelength-selective mirror 14 which transmits or reflects visible light and reflects or transmits infrared light is interposed between the variable power lens 12 and ocular 16 of the real-image finder optical system to split the optical path of the visible light and the optical path of the infrared light. Then the triple light emitting means 41 is arranged on the focal plane on the optical path side of the infrared light and spot light is projected on a subject through the finder optical system. Here, the objective optical system is variable in magnification, so the projection angle of an IRED 41 varies according to the zooming of the finder and the ratio is equal to variation in the finder magnification. Consequently, the relation between the range finding frame and the spot light is held invariably constant irrelevantly to telephoto-wide angle switching.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a camera, more specifically, a camera that projects infrared light from a plurality of infrared light emitting diodes (hereinafter abbreviated as IRED) toward a subject. The present invention relates to a so-called active type multi-point distance measuring camera that automatically measures the distance to a subject by receiving reflected light from the subject and drives the lens to a focused point.

[Prior Art] As is well known, distance detection devices used in compact cameras, etc., project infrared light through a light projection lens toward a subject located in the center of the screen. The reflected light from the subject is received by the semiconductor device detection device through a light-receiving lens provided a certain distance away from the object, that is, the baseline length, and the distance to the object is determined based on the incident position, so-called infrared light projection. An active triangular nJ distance system is adopted.

However, when shooting using this method, if the main subject is not in the direction of the light projection, that is, in the center of the screen,
The distance detection device detects other objects or the background, i.e.
j distance, resulting in an out-of-focus photo of the main subject (hereinafter referred to as an out-of-focus photo). Therefore,
The screen position where the dP1 distance of the object is possible is limited to the center.

Therefore, a multi-point distance measuring method has been put into practical use in which a plurality of light projection signals for the n1 distance are used to measure a plurality of 1llll distance positions within the finder.

Even in cameras equipped with such distance detection devices,
In recent years, photographic lenses have become increasingly zoomed and telephoto wide, and the magnification of the finder has come to change in accordance with the focal length of the photographic lens. However, in this case, although the angle of view of the finder changes, the projection optical system remains fixed.

[Problems to be Solved by the Invention] However, for such a finder whose angle of view changes in conjunction with changes in the focal length of a photographic lens with a variable focal length, the CJ distance projection optical system remains fixed. In this case, the position of the spot light relative to the viewfinder field of view changes due to zooming, and the position of the focal length frame and the spot light are not constant, resulting in the following inconvenience.

That is, as shown in FIG. 11, a real image finder 6, a light projection lens 2, and three IREDs 41a.

The relationship between the light beams projected and received by the light projection optical system consisting of 41b and 41c is as follows. IRED41a, 4
The light emitted from 1b and 41c is condensed by the projection lens 2 and projected toward a subject (not shown) at a projection angle θ3. The reflected light reflected from the subject enters the real image finder 6, but at this time, if the photographic lens has a variable focal length, such as a tele/wide switching type or a zoomable photographic lens, the same size film surface is used. The size of the subject image captured in each case is different, that is, the angle of view is different. In other words, since the projection optical system is fixed, the projection angle θ3 is a constant value, for example 14 degrees, but on the camera side, when the camera is telephoto, the subject image is magnified, so the luminous flux with the width of the incident angle θ2 is When the lens is wide, the angle is wide, so a light beam having a width of the incident angle θ1 will be incident on a screen of the same size.

Therefore, on the finder screen shown in Figure 12,
iP entering the n1 range frame 32 of the finder field frame 31
The spot light position used for I-distance is 34°35.36 at the spot light receiving position indicated by the black dot in wide mode, but when switched to the telephoto side, the spot light receiving position is 33° indicated by the white circle in the figure. .35', it becomes 37. The center spot light receiving position 35.35' is the first spot light receiving position 35.35'.
IRED41 in the center of the three IRED41 in Figure 1
Since it corresponds to b, it is the same as the spot light reception position in the case of 1 point AL 11 distance, but even in the case of 1 point AL distance method, if the projection optical system is fixed, the spot diameter with respect to the viewfinder field of view will change, It becomes difficult to make the A111 distance fracture 32 small.

In order to solve this problem, there is a method in which the projection optical system is variable in magnification in accordance with the viewfinder, but this increases the cost considerably and also leaves problems in terms of space.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems and provide a camera capable of multi-point distance measurement using a variable focus active AF method, in which the ΔIIJ range frame and the nJ range spot position in the finder match. be.

[Means and effects for solving the problems] The camera of the present invention includes a distance detection device that emits light toward a subject and detects the distance by receiving the reflected light, and a photographic lens with a variable focal length. In a camera having a real image finder that changes the angle of view in conjunction with changes in the focal length of the camera, the light projection system of the distance detection device includes a variable magnification objective optical system that is a part of the real image finder; A half mirror with wavelength selectivity inserted into the optical path of the objective optical system; and a light emitting device disposed in the optical path behind the half mirror to emit light to be projected onto a subject via the objective optical system. It is characterized by having and ζ.

[Example] Prior to describing specific examples of the present invention, the second
The principle of single-point distance measurement using the active method will be explained using the figures, and the principle of multi-point distance measurement using the active method and its electric circuit system will be explained using FIGS. 3 and 4.

FIG. 2 is a configuration diagram showing the arrangement of the optical system, etc. in one-point distance measurement, and the light emitted by IREDI is transmitted through the projection lens 2.
The reflected light is focused and irradiated toward the subject 3, and the reflected light is imaged by a light receiving lens 4 onto a well-known position detection device (hereinafter abbreviated as PSD) 5 made of a semiconductor.

When the optical axis of the light-receiving lens 4 is aligned with the center line of the PSD 5 and this is set as the origin, the reflected light incident position is X, and the distance between the principal points of the light-emitting lens 2 and the light-receiving lens 4, that is, the baseline length is 81 If the focal length of the light-receiving lens 4 is f, then the subject distance g is (1-s・f/x (1)
is given by

The photocurrent 1.1 generated in the PSD 5 is both proportional to the incident light intensity, but the photocurrent ratio 1 t /I 2 does not depend on the incident light intensity and is determined only by the incident light position X. Therefore, if the photocurrent 1 t /I 2 of the PSD 5 is determined, the subject distance g is uniquely determined.

In Fig. 2 above, in order to simplify the explanation of the al distance principle of the active triangulation distance measuring method, a configuration is used that performs a simple one-point distance, but when this is applied to three-point distance measurement, the optical system etc. The configuration is shown in Figure 3.

In FIG. 3, three PSDs are connected to three IREDs 41a, 41b, and 41c constituting three IREDs 41.
Three PSDs 44a make up 44.

44b, 44c are used, and three IRED41
The distance measuring infrared beams 47a, 47b, 47c from a, 4lb, 41c are directed toward the subject by the projecting lens 2, and each beam reflected from the subject is directed to the three PSDs 44a, 44b by the light receiving lens 4.

The light is incident on the corresponding PSD of 44c.

The reason why the PSD is divided into three is to minimize the influence of incident light from other directions during negative point distance measurement, thereby improving the S/N ratio.

FIG. 4 is a block diagram of an electric circuit showing an example of a distance detection device to which the three IREDs and three PSDs are connected.

The distance detection device is IRED41a, 4 lb.

A driver 27 that selects light emission from 41c, and a selection circuit that selects photocurrent signals output from PSDs 44a, 44b, and 44c that are optically paired with selected IREDs 41a, 41b, and 41c, and outputs them to the next stage. 21a, 21
b% selection circuit 21a.

21b, an IV conversion circuit 22a22b that performs IV conversion on the photocurrent signal outputted from 21b and converts it into a voltage signal; an effective subject light component by removing a background light component from the voltage signal;
In other words, the change detection circuit 23a detects only the change.
23 bs A difference signal output circuit 24 that detects the difference between the above changes, a sum signal output circuit 25 that detects the sum, a ratio calculation circuit 26 that calculates the ratio between the sum and the difference, and a control circuit 28 that sequentially controls these. It is configured. Here, the output of the ratio calculation circuit 26 becomes a signal corresponding to the subject distance, and since there are three points, three types of signals are output. The main CPU of the camera (not shown) determines which one of them to select as the distance signal.

Next, specific examples of the present invention will be described. In the present invention, the optical path of the light projecting optical system is arranged in parallel with the optical path of the real-image type finder optical system, so the first embodiment of the present invention will be described using FIG. 1 showing the optical arrangement of the finder optical system. The main parts of the camera will be explained.

First, the outline is that a wavelength selective mirror 14 that transmits or reflects visible light and reflects or transmits infrared light is inserted between the variable magnification system of the real image finder optical system and the eyepiece to change the optical path of visible light. and splits the optical path of infrared light. Three IREDs 41 are arranged at the focal point on the optical path side of the infrared light, and the spot light is projected onto the subject through the finder optical system. - Also, as will be described later, the width of the PSD is variable according to zooming.

Next, the details will be explained. Objective lens 11° variable magnification lens 12. The objective optical system consisting of the correction lens 13, the finder optical system consisting of the Porro prism 15, and the eyepiece 16 uses a real image type zoom finder whose objective system has variable magnification. In the optical path of the objective system, a wavelength-selective mirror 14 that reflects only infrared light is provided from the first imaging plane to the objective lens side, and the optical path of the infrared light is divided, and an IRE is placed at the imaging position of the infrared light optical path.
Triple IRED41 consisting of D41a, 41b, 41c
to be placed.

In such a configuration, visible light is not reflected by the wavelength selective mirror 14 and is guided to the pupil 17, so that it is used as a normal finder.

On the other hand, the infrared light from the I-RED 41 is reflected by the wavelength selective mirror 14 and projected onto the subject through the objective optical system. Here, since the objective optical system is variable in magnification, the projection angle of the I RED 41 will also change in accordance with the zooming of the finder, and the ratio will be the same as the change in finder magnification.

The above-mentioned FIG. 1' shows an example in the wide-angle mode, but since the IRED projection angle naturally changes in the telephoto mode, FIG. 5 shows the lens position and the light projection angle θ5 in the telephoto mode.

In this way, during telephoto mode, the projection angle changes from θ in FIG. 1 to θ5 as the lens position of the variable magnification system moves. As a result, the projection spot position on the ranging frame 32 shown in FIG. is the same for both wide and telephoto.

Further, as for the wavelength selective mirror 14 used in the first embodiment shown in FIGS. 1 and 5 above, a normal half mirror without wavelength selectivity can be used, but the light amount is 1/1/2, respectively. 2, so it is more advantageous to select the wavelength.

FIG. 6 is an optical layout diagram in which I REDs are arranged side by side in the finder optical system of a camera showing a second embodiment of the present invention. In this second embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and their explanations will be omitted. This second embodiment differs greatly from the first embodiment in that the imaging position of the objective system is provided behind the first reflecting surface of the Porro prism 15, and this first reflecting surface is connected to the wavelength selective mirror 15.
4a. In this case, the wavelength selective mirror 1
4a transmits the infrared light from the I RED 41 through the prism 18 and reflects the visible light, and an example of the transmittance 1 reflectance is shown in FIG.

According to the second embodiment, since the optical path of the infrared light is straight and there is no reflective object, the variation in the light projection position is reduced compared to the first embodiment, and the distance measurement accuracy is improved.

Next, an example of the light receiving system will be described. Unlike the light emitting system, the light receiving system focuses on the spot on the finder's ranging frame 32.
(see Figure 12) has no effect. Therefore, it is advantageous in terms of cost to use a fixed optical system. In that case, as shown in FIG. 8, the imaging positions on the PSDs 44a, 44b, and 44c change due to zooming, so the shape of the PSD is changed so that the central PSD 44b is narrower, as shown in FIG.
Widen the PSDs 44a and 44c on both sides. Then,
From three I REDs (not shown), the projection angle θ is set at wide angle.
The light spots projected at the projection angle θ5 during telephoto are reflected by the subject and then imaged one by one on the PSDs 44a, 44b 44c via the light receiving lens 4. Since the relationship between the IRED and PSD pair remains unchanged, the distance measuring circuit shown in FIG. 4 can be applied.

By the way, the IRED used in Figures 3 and 8 above
41a, 41b, 41c and PSD44a.

44b and 44c each form a pair,
Basically, even one wide PSD can be used. However, the problem in this case is that the signal current output from the PSD is limited even if three PSDs are used as shown in Figures 3 and 8 above, or when one wide PSD is used.
The same is true even if an SD is used, but the photocurrent due to the steady light component reflected from the background, that is, the noise component, increases by twice the area ratio when using one wide PSD, so the S/N of the signal increases.
This means that the ratio decreases.

By the way, the PSD requires the most width when in wide mode, and the required width is the minimum when in tele mode. Moreover, this telephoto mode requires the most precision.

Therefore, if the width of the PSE (PSE) is changed by zooming so that it is wide when wide and narrow when telephoto, the S/N ratio during telephoto does not need to drop much.

Figure 9 shows the width of the three PSDs constituting the light receiving system based on this idea, contrary to Figure 8 above.
This is an example in which the SD 44d is wide and the PSD 44e on both sides are narrow, and the circuit configuration in this case is shown in FIG. In FIGS. 9 and 10, the same components as in FIGS. 8 and 4 are designated by the same reference numerals, and their explanations will be omitted.

The major difference between FIG. 10 and FIG. 4 is that the selection of PSD is changed by zooming. That is, in the tele mode, only the PSD 44d of the PSDs shown in FIG. 9 is connected to output the signal, and in the wide mode, the PSD 44e is connected in parallel with the PSD 44d to output the signal as one wide PSD. Colleni Yotte, IRED41a,
41b.

The image of 41c is received and a signal is output.

Therefore, the control circuit 28 uses the zooming information to
Switch s that connects SD44d and PSD44e in parallel
It is configured to control w and sw2.

Further, in this case, it is sufficient to switch the light receiving element only when changing the focal length, that is, when switching between tele and wide, and there is no need to switch the light receiving element together with the selection of the IRED.

Conventionally, each time the IRED and PSD were switched, the steady light component differed, so the change detection circuit required stabilization time, but according to the present invention, this is not necessary and
It is also possible to shorten the 1ll distance time.

In each of the above embodiments, a method for distance measurement at three points has been described, but if one pair of I RED and PSD out of three IREDs and three PSDs is used, it can be used for one point distance measurement method. Needless to say.

It goes without saying that the present invention can also be applied to multi-point distance measurement of three points or more.

[Effects of the Invention] As explained above, according to the present invention, the projected light spot position and spot diameter change in accordance with the zooming of the finder without taking up much space or increasing costs. The relationship between the distance frame and the spotlight
It can always be kept constant regardless of wide switching. Further, by making the width of the PSD variable in accordance with zooming, a number of remarkable effects such as shortening the distance measurement time without impairing the distance measurement accuracy are exhibited.

[Brief explanation of the drawing]

FIG. 1 is a side view showing a finder optical system and a light projection optical system in a camera according to a first embodiment of the present invention, and FIGS. 2 and 3 are active triangulation systems applied to the camera according to the present invention. This is a diagram explaining the principle of distance.
The figures are optical layout diagrams each showing the case of 3-point distance measurement, Figure 4 is a block system diagram showing an example of an electric circuit that embodies the 3-point +1-1 distance in Figure 3 above, and Figure 5 is ,
FIG. 6 is a perspective view showing the finder optical system and light projection optical system in the camera according to the second embodiment of the present invention; FIG. 7 is a perspective view showing the optical system shown in FIG. The characteristic line diagram showing an example of the transmittance and reflectance of the wavelength selective mirror in FIG. 6, and FIG. 8 are the characteristic diagrams shown in FIG. Three series of P used in the second embodiment
FIGS. 9 and 10, which are perspective views schematically showing the incident optical path to the SD, are the same as those shown in FIGS. 1, 5, and 6 of the present invention.
．． An optical layout diagram and a block system diagram of the drive circuit respectively showing other examples of the triple PSD used in the second embodiment, and Figures 11 and 12 show the projection spot by the conventional projection optical system. FIG. 2 is an optical path diagram and a layout diagram within the field of view of the finder when displayed on the distance measuring frame of a real image finder. ３・・・・・・・・・・・・Subject 6・・・・・・・・・Real image finder 11.1
2.13... Objective optical system 14...
...Wavelength selective mirror (half mirror with wavelength selectivity) 41a. 41b. 41, c...I RED (light emitting means) 44a. 4b 44C3 44d. 4e ・・・・・・・・・PSD (light receiving means)

Claims (2)

[Claims] (1) A distance detection device that emits light toward the subject and detects the distance by receiving the reflected light, and a real image that changes the angle of view in conjunction with changes in the focal length of the variable focal length photographing lens. In the camera having a type finder, the light projection system of the distance detection device includes a variable magnification objective optical system which is a part of the real image type finder, and a wavelength selective optical system inserted into the optical path of this objective optical system. What is claimed is: 1. A camera comprising: a half mirror; and a light emitting unit disposed in an optical path behind the half mirror and emitting light to be projected onto a subject via the objective optical system. (2) A distance detection device that emits light toward the subject and detects the distance by receiving the reflected light, and a real image that changes the angle of view in conjunction with changes in the focal length of the variable focal length photographing lens. In a camera having a type finder, the electrode is provided near the imaging point of the lens that receives the reflected light from the subject, and changes the width in the direction perpendicular to the electrode in conjunction with changes in the focal length of the photographic lens. A camera characterized in that it is provided with a light-receiving means.