JPH026430Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a zone-type autofocus detection device, and more particularly, to an improvement of the zone-type autofocus detection device that can detect the in-focus zone without the need for optical or electrical scanning means. .

Various types of zone autofocus detection methods have been proposed, including the extreme value method, double image matching method, and gravity method, and each method requires mechanical, optical, and electrical scanning means. and one which does not require any scanning means has been proposed.

Among these methods, methods that do not require any scanning means are very advantageous in terms of operation and design, but on the other hand,
The number of focus detection means increases in proportion to the number of zones, which poses problems in terms of economy and accuracy.

As a solution to these problems,
No. 138825 (corresponding U.S. Pat. No. 3,945,023), a light receiving element array receives light from a subject incident along a first optical path and a light receiving element array receives light from a subject incident along a second optical path. Depending on the light-receiving element array, the object image taken by the first optical path corresponds to the part of the object image taken by the second optical path, that is, the focus is determined by the amount of shift in the intensity distribution of these two object images. A zone type autofocus device that employs a double image matching method for position detection has been proposed.

However, this method, which has already been proposed, not only requires a large number of circuit elements for the detection circuit for detecting the amount of deviation in the intensity distribution, but also has the problem of erroneous alignment due to the subject pattern because it detects the amount of deviation in the intensity distribution. It may generate a focal signal.

Therefore, it is an object of the present invention to solve these conventional economic and accuracy problems and to provide an improved zone type autofocus detection device that is industrially highly practical.

The feature of this invention is that the reference subject image (imaged by an imaging optical system that coincides with the imaging optical axis) and the imaging optical axis are divided into multiple zones, and each of the divided zones A light-receiving element is provided to measure the brightness of each of the subject images, and the in-focus position is determined by checking the match between the reference subject's photometric value and other photometric values, that is, the match between the reference subject image and the image of each zone. This is a zone-type autofocus detection device designed to detect.

Hereinafter, the present invention will be described with reference to preferred embodiments of the accompanying drawings.

FIG. 1 is a diagram illustrating the principle of the zone type autofocus detection device of the present invention, and will be explained together with the signal processing circuit shown in FIG. 2, where the same components are denoted by the same reference numerals.

Lens L ₀ as an imaging optical system having an optical axis that coincides with the photographing optical axis (including an optical axis that substantially coincides with and parallel to the photographing optical axis, the same shall apply in the following description) and this lens A reference light-receiving means consisting of a light-receiving element _P0 that measures the brightness of a subject image formed by _L0 , has an optical axis that coincides with the photographing optical axis, and is located at a position spatially separated from the lens _L0 . arranged lens L ₁ and this lens
L ₁ and an auxiliary light receiving means consisting of a light receiving element _{P 1 for} measuring the subject brightness at d ₁ on the optical axis of the lens L ₀ out of the subject image formed by the lens L ₁ ; An auxiliary light receiving means consisting of a lens L ₂ and a light receiving element P ₂ for measuring the subject brightness on the optical axis (d ₂ not shown), and an auxiliary light receiving means for measuring the subject brightness on the optical axis (d ₃ not shown) of the lens L ₀ . An auxiliary light receiving means consisting of a lens L ₃ and a light receiving element P ₃ for photometry, and a lens L ₄ and a light receiving element P ₄ for measuring the subject brightness on the optical axis of the lens L ₀ (d ₄ not shown) Auxiliary light receiving means are provided respectively.

The number of these auxiliary light receiving means is determined by the number of zones to be focused, and is not limited to the number in this embodiment.

Further, the light receiving element groups P ₀ , P ₁ , P ₂ , P ₃ and
The output of P ₄ is preamplifier 1, 2, 3, 4 and 5
The output of the preamplifier 1 is limited to a predetermined level by a variable resistor 6 and provided as a reference voltage to each of the comparison circuits 11 to 14.

Further, the outputs of the preamplifiers 2 to 5 are limited by variable resistors 7 to 10 to the same level as the level provided by the variable resistor 6, and are applied to the input terminals of the comparison circuits 11 to 14, respectively.

With the above configuration, first, when there is a subject at _one point d on the photographing optical axis, the subject image on the photodetector P ₀ and the subject image on the photodetector P ₁ match, and these photodetectors
The photometric outputs of P ₀ and P ₁ will match, but
The image positions of the subject images on the light-receiving elements _P2 to _P4 are slightly shifted, and different photometric outputs are generated.

Therefore, in the signal processing circuit shown in FIG.
4 as a reference voltage, the output V ₁ of the comparator circuit 11 shows the minimum value (indicates zero voltage when the images match perfectly).

Furthermore, if there is a subject at _two points d on the photographing optical axis, the subject image on photodetector _P0 and the subject image on photodetector _P2 match, and the photometric outputs of these photodetectors _P0 and _P2 match. However, the light receiving elements P ₁ , P ₂
The image positions of the subject images on _P4 are slightly shifted, and different photometric outputs are produced.

Similarly, the output V ₂ of the comparator circuit 12 shows the minimum value.

Therefore, by detecting which of the outputs V ₁ to V ₄ of these comparison circuits 11 to 14 is the minimum, it is possible to determine in which zone the subject exists, and the in-focus zone can be easily detected. be.

FIG. 3 shows a front view of the above-described zone type autofocus detection device mounted on a compact camera, and shows an example in which it is arranged in a straight line above the photographic lens 32 and to the side of the viewfinder 31.

Here, an infrared light emitting unit 30 is provided, and is configured to operate in conjunction with, for example, the main switch 34 of the flash unit 33 when the subject is not bright enough, but it always emits light in conjunction with the release button 35. You may also do so.

Furthermore, in order to achieve a more compact configuration, it is desirable to convert the respective optical axes using reflective mirrors 40 to 45 and arrange the light receiving elements upward, as shown in FIG. Needless to say, it can be set in any way as long as it achieves the desired effect.

FIG. 5 is a perspective view showing another embodiment of the present invention, which will be described together with the front view shown in FIG. 6. Here, the zone type autofocus detection device is arranged on an arc around the photographing lens, and the reference light receiving means L ₀ and P ₀ shown in the above embodiment are provided for each zone.

Here, the light receiving means 51 and 51' are on the photographing optical axis.
The light-receiving elements are respectively arranged so that the photometric output is zero when the subject is present at _one point d, and the light-receiving means 52 and 52' are arranged so that the photometric output is zero when the subject is present at _two points d on the photographing optical axis. The light receiving elements are arranged so as to correspond to the respective zones, and similarly, the light receiving means 53 and 53' to 57 and 57' are arranged corresponding to the respective zones.

As described above, the number of sets of light receiving means is determined depending on the zone to be set, and is not limited to the number in this embodiment.

Therefore, the in-focus zone can be easily detected by determining which output shows the minimum value among the differential outputs of these sets of light receiving means.

By arranging the light receiving means on an arc around the photographic lens in this manner, it is possible to completely eliminate parallax, increase the number of zones, and achieve a highly accurate and compact configuration.

As is clear from the above explanation, the focus detection method of the present invention detects the coincidence of the outputs of the respective light receiving means, that is, the coincidence of images, by detecting the brightness, so regardless of the subject, the minimum value, that is, the focus signal In addition, even under illumination light with ripples such as a fluorescent lamp, the focus signal is canceled and focus detection can be performed with extremely high precision.

Furthermore, as a signal processing circuit, the preamplifier, comparison circuit, etc. need only be as many as the number of zones, making it extremely simple to configure, and making it easy to configure multiple zones. A focus detection device can be provided.

[Brief explanation of the drawing]

Fig. 1 is a diagram for explaining the principle of the zone type autofocus detection device of the present invention, Fig. 2 is a circuit wiring diagram showing the signal processing circuit, and Fig. 3 is a diagram showing the case where the device of the present invention is implemented in a compact camera. 4 is a sectional view showing another embodiment of the device of the present invention, FIG. 5 is a perspective view of the device of the present invention arranged around the photographic lens, and FIG. 6 is a cross-sectional view showing another embodiment of the device of the present invention. Each shows a front view. L ₀ to L ₄ ...imaging lens, P ₀ to P ₄ ...
Light receiving element, 1 to 5...Preamplifier, 6 to 10...Variable resistor, 11 to 14...Comparison circuit, 30...Infrared emitter, 31...Finder, 33...Flash device, 35...Release button,
40 to 45...Reflection mirror, 51 to 57
... Light receiving means, 51' to 57'... Light receiving means.

Claims (1)

[Scope of utility model registration request] The optical axis of the photographing lens is divided into a plurality of zones, and in order to measure the subject brightness of each divided zone in pairs, a pair of photometry means consisting of an imaging optical system and a light receiving element corresponding to the number of zones is photographed. The lens is arranged symmetrically across the optical axis of the lens, and is configured such that the zone in which the difference in photometric output of a pair of photometric means for measuring each zone is the minimum value is set as the focal position. Zone type auto focus detection device.