JPS59129812A - Focusing detecting device - Google Patents

Abstract

PURPOSE:To decide focusing in any case of a visible light and an infrared ray by providing two view aperture of a visible light view aperture and an infrared light view aperture, and forming an image again by a common secondary image forming optical system. CONSTITUTION:The first view aperture 2a and the second view aperture 2b are provided in the vicinity of an expected image forming surface of a photographic lens 1. Also, a pupil splitting means 5 of the photographic lens 1 and a secondary image forming lens 6 are placed in the rear of the expected image forming surface, images formed by the photographic lens 1, which are formed in the vicinity of the first and the second view apertures 2a, 2b are formed again, and also, on a position for photodetecting these images, each one pair of the first and the second photoelectric converting element trains 8a, 8c and 8b, 8d corresponding to the first and the second view apertures 2a, 2b are provided. The first and the second optical filters having each different spectral transmittivity characteristic are placed in accordance with these photoelectric converting element trains, immediately before these photoelectric converting element trains 8a, 8c and 8b, 8d.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a so-called TTL type focus detection device for detecting focus using an imaging light beam from a photographing lens, for example in a -eye reflex camera.

A method that detects focus by receiving only reflected natural light from the subject is called a passive type. This passive type focus detection device functions well when the subject brightness is bright enough, but when the subject brightness becomes darker than the value, the amount of light incident on the light receiving sensor is insufficient and the function does not work. It becomes stable. In preparation for such a case, an auxiliary light source is installed on the camera body, and when the subject brightness is below the limit value, the auxiliary light source emits light to illuminate the subject.
A method of ensuring sufficient subject brightness for a focus detection device is also well known. However, although there is no problem when using visible light as the auxiliary light, there is a major problem when using infrared light as the auxiliary light. That is,
It is difficult to realize a practical focusing optical system that combines a focusing optical system that uses natural light from a bright object and a focusing optical system that uses infrared light for a dark object.

In general, in photographic lenses, there is a difference between the focus position for visible light and the focus position for infrared light, and it is difficult to take a well-focused photo unless you distinguish between visible light and infrared light and perform focus detection. I can't. Conventionally known focus detection devices that detect focus by distinguishing visible light from infrared light are: (1) focus detection for two types of light: visible light and infrared light; Equipment to prepare (2)
There is a focus detection device that realizes focus detection for two types of light by inserting and removing an infrared cut filter into and out of the focus detection device. In the former case (1), two types of optical systems must be prepared, and in the latter case (2), a mechanism for putting in and taking out the infrared cut filter is required, which is not practical.

An object of the present invention is to solve the above-mentioned problems and provide a focus detection device that can realize two types of focus detection, one for visible light and one for infrared light. First and second field apertures are provided near the intended image forming plane of the lens, a pupil dividing means and a secondary imaging optical system of the objective lens are arranged behind the intended image forming plane, and the first and second field apertures are arranged behind the intended image forming plane. at least one pair each of the first and second field apertures corresponding to the first and second field apertures at positions for re-forming images formed by the objective lens near the field apertures 2 and receiving these images; A photoelectric conversion element array is provided, and immediately before these first and second photoelectric conversion element arrays,
Corresponding to these photoelectric conversion element rows, the first. It is characterized in that a second optical filter having mutually different spectral transmittance characteristics is arranged.

The present invention will be explained in detail based on illustrated embodiments.

FIG. 1 shows a first embodiment of the present invention, in which a light shielding member 2, a light shielding member 2, A field lens 3, an aperture frame 4, a pupil divider 5, a secondary imaging lens 6, an optically transparent member 7, and a sensor substrate 8 are arranged. The light shielding member 2 has two rectangular field apertures 2a and 2b arranged in parallel, and the aperture frame 4 has two rectangular aperture frames 4a.

4b, and at the rear of these wedge prisms 5a, which have mutually different inclination angles and constitute a pupil divider 5,
5b is placed. In addition, the sensor board 8 has two
Two sets of line sensors 8a, 8b, 8c, 8d (8a
-8b) and (8c/8cl), and these sets are provided parallel to the field apertures 2a and 2b. The optically transparent member 7 immediately in front of the sensor substrate 8 has a first. A second dielectric multilayer R@7a, 7b is coated and the first
A first dielectric multilayer film 7a that transmits visible light and reflects infrared light immediately before the line sensors 8a and 8b of the set, and reflects visible light just before the second set of line sensors 8c and 8d. A second dielectric multilayer film 7a that transmits infrared light is arranged.

The light rays Ll and L2 from the subject that have passed through the photographic lens 1 are focused on one point of the field aperture 2a and reach the field lens 3, and the field lens 3 focuses the pupil of the photographic lens 1 in the vicinity of the pupil divider 5. Image. Therefore, the light ray L1 coming from one side of the pupil of the photographing lens 1 passes through the aperture frame 4a and enters the wedge prism 5a, where it is deflected to the left where it is thicker and sent to the line sensor 8a by the secondary imaging lens 6. Form an image. Similarly, the light ray L2 from the opposite pupil of the photographic lens 1 is deflected downward by the wedge prism 5b and is reflected by the line sensor 8.
The image is formed on b. The secondary imaging lens 6 has field apertures 2a, 2
b is the line sensor (8a -8) of the sensor board 8, respectively.
b) and (8c and 8d). In this way, one field aperture becomes two images separated left and right depending on the pupil position of the photographing lens l, and the sensor board 8
imaged on top. Therefore, the wedge prisms 5a and 5 are arranged so that the images of the two field apertures 2a and 2b do not overlap each other.
If the apex angle of b and the spacing between the field apertures 2a and 2b are designed, a total of four field aperture images are formed side by side in the left and right direction on the sensor substrate 8, and the line sensors 8a to 8d It is installed corresponding to two visual field images. Field of view aperture 2
The optical image formed on the lens a by the photographing lens 1 is re-imaged onto the line sensors 8a and 8b by the field lens 3, pupil splitter 5, and secondary imaging lens 6. Immediately before the line sensors 8a and 8b, there is a first sensor that transmits visible light.
Since the line sensors 8a and 8b are coated with a dielectric multilayer film 7a, the light intensity distribution of the subject image using visible light is refocused, and the output signals are supplied to the focus determination electric processing system, respectively. By determining the amount of lateral shift on the line sensors 8a and 8b, focus detection for the visible light image can be performed.

On the other hand, when performing focus detection using infrared light as auxiliary light, the line sensor 8C18d is
Only the infrared light of the upward optical image information is transmitted through the second dielectric multilayer film 7b, and an infrared light image within the viewing aperture 2b is re-imaged. Therefore, by supplying the output signal of the line sensor 8C18d to the focus determination electric processing system, it becomes possible to detect the focus on the infrared light image.

In this way, in the present embodiment, when the subject brightness is sufficiently bright, the output signals from the line sensors 8a and 8b are used when the subject brightness is not sufficient and the subject is illuminated with infrared light as auxiliary light. is line sensor 8C18d
It is only necessary to provide the output signals from the two to the focus determination electric processing system.

The second embodiment shown in FIG. 2 achieves the same functions as the first embodiment by changing the configurations of the pupil divider 5 and the secondary imaging lens 6. In this embodiment, the pupil splitter 5 consisting of wedge prisms 5a and 5b is omitted, and the secondary imaging lens 6 is a pair of imaging lenses 6a having a straight boundary part,
6b, which also serves as pupil dividing means.

FIG. 3 shows a third embodiment, in which the present invention is applied to an automatic focus detection optical system that operates effectively for photographic lenses l having a wide range of open F numbers. This embodiment basically has the configuration shown in FIG. 1, but the pupil divider 5 is used differently according to the difference in pupil area in the photographic lens 1, and the deflector 5c is for lenses with a bright F number, and the deflector 5c is for a lens with a bright F number, and Since the lens deflector 5d is divided into two parts, one visible light is divided into four field aperture images on the sensor substrate 8. Therefore, two viewing apertures 2a,
A total of eight field aperture images are obtained for the field aperture 2b, and line sensors 8a to 8h are arranged corresponding to each field aperture image.

A first dielectric multilayer film 7a that transmits visible light is arranged immediately before the line sensors 8a to 8d, and a second dielectric multilayer film that transmits infrared light is arranged immediately before the line sensors 8c to 8h. 7b is placed. In this embodiment, line sensors 8a to 8h are used as shown in the following table.

Type of light image F/N of photographic lens used
Line sensor visible light Bright 8a/8b Visible light Dark 8c*8d Infrared light Bright 8
e.8f Infrared light Dark 8g Pot 8h In each of these cases, the amount of image deviation is determined based on the output signals of the pair of line sensors shown on the right side, and a focus determination can be made.

As mentioned above, in general photographic lenses, the focus position for visible light and the focus position for infrared light are different. In order to make the focus detection device of the present invention work more effectively for strobe photography, etc., it is necessary to measure the difference in focus position between visible light and infrared light for each lens by adjusting the length of the signal pin or using a semiconductor memory, etc. This amount is stored in electronic memory, read from the camera body side, and after confirming focus with infrared light, move the photographing lens by the read amount to determine the planned focus using visible light. All that is required is for the camera body to perform control such as positioning the photographing lens on the gong, emitting strobe light, and taking a photograph.

In the present invention, since the visual field aperture 2a for visible light and the field aperture 02b for infrared light are slightly separated vertically, strictly speaking, the same part of the subject is photographed in the case of visible light and in the case of infrared light. However, if this interval is kept small, this will hardly be a problem in practice.

As explained above, in the focus detection device according to the present invention, the two field apertures, the visible light field aperture and the infrared light field aperture, are reimaged by a common secondary imaging optical system. , by using line sensors for visible light and infrared light, and simply switching the output signal supply from the line sensor to the focus judgment electric processing system, focus judgment can be made in cases where visible light and infrared light are off to the side. is also possible.

[Brief explanation of the drawing]

The drawings show embodiments of the focus detection device according to the present invention, FIG. 1 is a block diagram of the first embodiment, FIG. 2 is a block diagram of the second embodiment, and FIG. 3 is a block diagram of the third embodiment. It is a block diagram of an Example. 1 is a photographic lens, 2 is a light shielding member, 2a and 2b are field apertures, 3 is a field lens, 4.4a and 4b are aperture frames, 5 is a pupil divider, 5a and 5b are wedge prisms, 5C1
5d is a deflector, 6 is a secondary imaging lens, 6a, 6b are lenses, 7 is an optically transparent member, 7a, 7b is a dielectric multilayer film, 8
is a sensor board, and 8a to 8h are line sensors. Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] 1. A first lens near the intended imaging plane of the objective lens. A second field aperture is provided, an Ow1 dividing means of the objective lens and a secondary imaging optical system are arranged behind the planned image forming plane, and the first
, a first field aperture corresponding to the first and second field apertures at a position where images formed by the objective lens formed near the second field aperture are re-imaged and these images are received. At least one pair of second photoelectric conversion element arrays are provided, and immediately before these first and second photoelectric conversion element arrays, first and second different spectral arrays are provided corresponding to these photoelectric conversion element arrays. A focus detection device characterized by disposing an optical filter having transmittance characteristics. 2. The focus detection device 3 according to claim 1, wherein the first and second field apertures are rectangular and arranged in parallel, the first optical filter transmits visible light and transmits red light. 2. The focus detection device according to claim 1, wherein the second optical filter has a property of blocking external light, and the second optical filter has a property of blocking visible light and transmitting infrared light.