JPS5910911A - Detector of focal position - Google Patents

Abstract

PURPOSE:To enable the detection of a focusing state up to a wide range of defocusing regions by disposing sensors before and behind an intended image- forming plane. CONSTITUTION:A photoelectric transducer array 72 which is the concrete element of a sensor 17 is disposed in coincidence with an intended image-forming plane 15, a photoelectric transducer array 71 is disposed near a photographing lens 14 from the plane 15, and a photoelectric transducer array 73 near the side opposite from the lens 14 from the plane 15, respectively. Part of the luminous fluxes past a convex lens 8 forms an image in the partial region on the array 73. This region corresponds to the position 18' nearer the side opposite from the photographing lens further from the array 73. The output values of the arrays 71, 72, 73 change respectively with respect to the extension length of the lens, and the detection of a focusing state is made possible by the largely defocused output signal for the partial region of the array 73.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a focusing position detecting device, and more particularly, to a focusing position detecting device that divides an imaging light beam from a photographing lens in a camera into, for example, three parts, and divides the imaging light beam into three parts, and divides the imaging beam into three parts, and divides the imaging beam into three parts, and divides the imaging light beam into three parts, and divides the imaging beam into three parts, and divides the imaging light beam from the imaging lens into three parts, and divides it into three parts, and divides it into three parts, and divides it into three parts, and divides it into three parts, and divides it into three parts, and divides it into three parts, and divides it into three parts, and divides it into three parts, and divides it into three parts, and divides it into three parts, and divides it into three parts, and divides it into three parts, and divides it into three parts, and divides it into three parts. The present invention relates to a focus position detection device that includes COD line sensors and the like at a total of three locations (Ω locations) and detects the in-focus state from a comparison of blur at these three locations.

Conventionally, as a device for detecting the in-focus state by disposing image sensors in front and behind the expected image forming plane of the optical system of a camera, for example, the Japanese Patent Application Laid-open Sho SS-/! shown in FIG. 7 has been used. ;! ;The focus position detection method proposed in 30g is known. / is the optical axis of the imaging light flux incident from a photographing lens (not shown), s is a quick return mirror that partially transmits the imaging light flux, 3
The submirror reflects the imaging light beam that has passed through the quick return mirror downward and guides it to the light splitter.

The light splitter divides the imaging light beam into three parts, each with a different imaging position.
The team is guided to three line sensors arranged on a plane on the board S. In this focus position detection method,
By electrically processing one output word from each line sensor, an output value corresponding to the amount of lens protrusion can be obtained as shown in FIG. The horizontal axis represents the amount of lens protrusion, and the vertical axis represents the output value from the line sensor after electrical processing. The output value from each line sensor is F, , F2, etc. for the lens extension amount. It changes like F3. In this focus position detection method, three output values are accurately identified in the area indicated by //, but three output values cannot be identified in the areas 7.2 and /3. There was a defect in that it became difficult to accurately determine the in-focus state. Furthermore, to overcome this defect, a focusing position detecting device as shown in FIG. 3 has been proposed by Japanese Patent Application Laid-Open No. 5-5-763/Ω. As shown schematically as an optical system, this device has sensors installed approximately equidistantly in front and behind the intended image formation plane 15.

The in-focus state is determined based on three signals from the sensor /7 and a third sensor /g provided further from the photographic lens than the sensor /7.

With such a configuration, the in-focus state can be determined up to a considerable defocus area using the third sensor/g. However, this device requires the sensor to be placed outside the sensor near the intended image plane, and the board on which the sensor is mounted is also large, making signal processing complicated.
The drawback was that the cost was high.

The present invention was proposed in order to eliminate the defects mentioned in -1-, and detects the in-focus state over a wider range of defocus areas by arranging sensors before and after the intended image plane in the camera. An object of the present invention is to provide a focusing position detection device for an optical system of a camera.

In order to achieve the above-mentioned object, the present invention divides the imaging light beam of the photographic lens into two or more parts, and
In a focus position detection device that detects the focus position of a photographing lens based on the output signals of more than one sensor LK, an image is formed on at least/a few of the sensors arranged before and after the expected image formation plane. A part of the subject image is focused at a position where the amount of defocus is larger than other areas of the subject image, and the subject image, which is in a large defocus state, is brought into focus using the output signal from that part of the image. The purpose is to make it possible to detect.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 7(a) is a side view of one embodiment of the present invention;
FIG. 7(b) is a plan view of the embodiment shown in FIG. 7(a).

6 in the figure is a light splitter that divides a part of the imaging light beam guided through a photographing lens (not shown), a quick return mirror, and a submirror into three parts, and arranges three images at different imaging positions on a plane. Sensor arranged on the board 7 /B, /7.
Photoelectric conversion element array 7/, 71 which is a specific element of 7g
．． 73. g is a convex lens for changing the imaging position of a partial area of the subject image formed on the photoelectric conversion element array 73; The luminous flux / incident from the subject image is transmitted to the beam splitter B / which constitutes the light splitter Otsu.
, 6, and each photoelectric conversion element array q
/:q, :a, guided by q3.

Note that Otsu 3 is a total reflection mirror that guides a part of the luminous flux split by the beam splitter Otsuno to the photoelectric conversion element array 73 . FIG. S is a layout diagram of the sensors constituting the embodiment of FIG. 7 (aJ (bl).

Photoelectric conversion element array 7 which is a specific element of sensor/7
2 is made to coincide with the planned image forming plane 1/S, the photoelectric conversion element array 7/ is moved from the planned image forming surface 15 toward the taking lens/q, and the photoelectric converting element array 73 is moved from the planned image forming surface 15 toward the taking lens/q. They are each arranged on the opposite side from the da. A portion of the light beam that has passed through the convex lens g forms an image on a partial area on the photoelectric conversion element array 73. This region corresponds to a position /g' in FIG. S, which is further opposite the photoelectric conversion element array 73 from the photoelectric conversion element array 73 with respect to the intended image forming plane /S.

In Japanese Patent Application Laid-open No. 31-5-73330g, seven light receiving elements are arranged before and after the intended focal plane of the optical system, and a third light receiving element is arranged at or near the intended focal plane, and three A method has already been proposed in which the output signal of the light receiving element is electrically processed to detect the focusing state of the optical system. In this embodiment, (*) is similarly electrically processed to obtain an output value corresponding to the defocus amount as shown in FIG.

In FIG. 4, the horizontal axis shows the lens extension amount, and the vertical axis shows the output value from each photoelectric conversion element array after processing. The output values from each photoelectric conversion element array 7/, 7, 2, 73 change as F, , F, , , F3 with respect to the lens extension amount. Even in the area indicated by /2, the in-focus state can be detected by the output signal of a largely defocused partial area of the photoelectric conversion element array 73. Further, since the output signal from area /2 near the focus position F is very small, it does not affect the output signal near the focus position. That is, in FIG. 4, at the focus position F, the waveform of F3 is not affected by the signal corresponding to the large deformation region provided in a part of the photoelectric conversion element array 73.

Next, a λ-th embodiment of the present invention will be described with reference to FIGS. 7(a) and 7(b). Light splitter 6, photoelectric conversion element array 7/? , 2.73 has the same configuration as the first embodiment. In this embodiment, the image forming position of a partial area of the subject to be imaged on the sensor/B (photoelectric conversion element array 7/) disposed closer to the photographing lens than the planned image forming plane/S is changed. Configure it as follows.

Therefore, a concave lens 9 is disposed in a part of the optical path of the subject image formed on the photoelectric conversion element array 7/. The partial area imaged by the photoelectric conversion element array 7/ through the concave lens is
As shown in FIG. S, this corresponds to the position /B' which is closer to the photographing lens than the sensor /B with respect to the expected image forming plane /S. As shown in FIG. 9, the output signal at this time becomes the output signal of a largely defocused partial region of the photoelectric conversion element array 7/ even in region /3, making it possible to detect the in-focus state.

It goes without saying that both the first and second embodiments of the present invention can be applied to the optical system of a camera, and as a means of changing the imaging position, the refractive index of the optical path part outside the lens can be changed. Alternatively, changes such as guiding the light to a different optical path and changing the optical path length are also possible.

The present invention increases the number of sensors by forming a large defocused image relative to the intended imaging plane in a partial area of the sensor arranged before and after the intended imaging plane as shown below. This has the effect that the in-focus state can be detected even when the subject image is largely defocused with respect to the intended imaging plane.

[Brief explanation of the drawing]

Fig. 7 is a schematic diagram of an optical system to which an image focus position detection device in a camera is applied, and Fig. Ω is an output of signals output from the three sensors of the focus position detection device in Fig. 7. A graph showing the relationship between the value and the lens extension amount of the output signal obtained by passing through the processing circuit, FIG. 3 is an explanatory diagram showing the arrangement position of the sensor in a conventional focusing position detection device, and FIG.
Figures (a) and (b) are explanatory diagrams of the optical system of the first embodiment of the present invention, and Figure S shows the arrangement positions of sensors constituting the embodiment of Figure 9 (a) (bl). An explanatory diagram, FIG. 4 is a graph showing the relationship between the output values of the signals output from the three sensors of the embodiment of FIG. 9 and the lens extension amount of the output signal obtained by passing through the processing circuit, Figure 7 (al (b)
9 is an explanatory diagram of the optical system of the first embodiment of the present invention, FIG. S is an explanatory diagram showing the arrangement position of the sensor configuring the embodiment of FIGS. are shown in Figure 7(a)(b)
9 is a graph showing the relationship between the output values of the signals output from the three sensors of the embodiment 1 and the lens extension amount of the output signal obtained by passing through the processing circuit. g. Convex lens, 9 ...Concave lens. /4'... Photographic lens. /Otsu, /7, 7g... - Sensor. Fig. 1 Fig. 2 Fig. 3 (a) Fig. 5

Claims (1)

[Scope of Claims] / A focusing position detection device that receives an imaging light beam from a lens with sensors arranged before and after a planned imaging plane and detects the position of the lens, at least one of the above sensors. A focusing position detection device characterized in that the two sensors optically make the imaging position of a subject image different in one area and in another area. A lens is disposed in a part of the optical path of the imaging light beam so that the imaging position of the object image is optically different between a part of the sensor and another part of the sensor. A focusing position detection device according to claim 1. 3. A concave lens is provided in a part of the optical path of the imaging light beam,
Claim No. Ω, characterized in that the imaging position of the subject is optically made different between a partial area and another area of at least one sensor disposed in front of the intended imaging plane. The focusing position detection device described in . q A convex lens is installed in a part of the optical path of the image-forming light beam, and the image-forming position of the subject is optically determined between a part of the sensor and another area of at least one sensor arranged behind the planned image-forming surface. A focusing position detecting device according to claim 1, characterized in that the focus position detecting device is configured to have a different focus position.