JPS61295521A - Focus detecting device - Google Patents

Abstract

PURPOSE:To increase the quantity of projected light while eliminating the influence of ghost and flare due to reflection between surfaces of a photographic lens by providing an optical stop system which has sectorial apertures right nearby an optical projection system. CONSTITUTION:A photometric circuit 55 outputs a signal on the basis of object brightness information obtained by a photodetecting element so that when the brightness of an outward field is lower than a specific level, an active AF mode is entered. A microcomputer 51 holds itself ready to turn on an LED 18. Further, the microcomputer outputs a signal for determining the passing area of light which is projected through the sectorial stop plate 30 to an electrooptic element 16 by referring to information in a ROM 54 arranged in the photographic lens 11. Focus detecting operation is started with a shutter release button, etc., and the information read out of the ROM 54 is updated according to the movement of the photographic lens 11, so that a light beam corresponding to flare and ghost is projected at every time. A light emitting circuit indicated by 56 controls the light emission timing of the LED 18 under the command of the microcomputer 51.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is a focus detection method that detects a focus position by projecting light onto a subject through a photographic lens and detecting the focus state by receiving the reflected light. Regarding equipment.

(Prior Art and its Problems) In general, an important element required for a focus detection device for an eye reflex camera is the ability to adapt to various interchangeable lenses having different open F-numbers and focal lengths.

It is also important to be able to perform focus detection regardless of the brightness of the outside world.

The present applicant has proposed a focus detection method that enables focus detection by introducing an auxiliary illumination device into a strobe and projecting light toward the subject when the outside world is dark (Japanese Patent Application No. 59-261194 No. 60-7686).

FIG. 8(a) and FIG. 8(b) show this focus detection method. In FIG. 8(a), 1 is a camera body, 2 is a photographic lens, and a subject image is received by a focus detection module 3. It automatically performs focus detection and focus adjustment.

The range defined by Su and SJl that is symmetrical with respect to the optical axis OA is the focus detection area.

An auxiliary illumination optical system 5 is provided in the strobe 4 that can be attached to this camera, and when it is dark such as at night, illumination light is projected from the auxiliary illumination optical system 5 onto the subject, and the reflected light is used to detect focus. It is configured to do this.

The illumination light is arranged at a distance B away from the optical axis OA of the photographic lens and inclined at an angle θ1, and emits light having a spread defined by nu, R, and 9. OB is the optical axis of illumination light.

In such a focus detection system, as shown in FIG. 8(b), the illumination light illuminates the focus detection area obliquely by the distance B between the illumination optical system and the focus detection optical system. Illuminable distance range (in Fig. 8(b), Lm
There is a natural limit to the range from in to L max (the range shown by the arrow). If we try to lengthen the distance range that can be illuminated, the irradiation angle of the illumination light must be widened accordingly, but this has the disadvantage that the subject distance at which focus can be detected becomes shorter.

Another major limitation is that focus detection cannot be performed when the strobe is not carried.

On the other hand, Japanese Patent Application Laid-open No. 54-155832 discloses that a lighting device is built into the camera body, and light is projected onto the subject side through a predetermined limited cross section of the photographic lens, and the light reflected by the subject is It is shown that the light passes through another limited cross section of the photographic lens and is received by a light receiving element to perform focus detection. In this case, the problem arises as to whether the projected light rays are affected by ghost or flare light due to inter-plane reflection of the photographing lens.

On the other hand, Japanese Patent Application Laid-Open No. 57-22210 discloses that the projection light from the light projection means is projected to the outside through a part of the photographic lens,
The light reflected by the subject and returned is received by the photoelectric light receiving means through another area of the photographic lens, and the light emitting optical axis and the light receiving optical axis are aligned with the main plane of the photographic lens.
2 shows a focus detection optical device that is set so as not to be point symmetrical with respect to the intersection between the principal plane and the tip axis of the photographic lens. This method eliminates the above-mentioned disadvantages. Further, by arranging the light emitting optical axis and the light receiving optical axis on the main surface so that they are not point symmetrical with respect to the optical axis of the photographing lens, ghosts and flares due to interplane reflection of the photographic lens are eliminated.

Here, since ghosts and flares caused by inter-plane reflections of the photographic lens are point symmetrical with respect to the optical axis of the photographic lens, settings can be made to avoid this relationship. What should be taken into consideration when applying this to a reflex camera is that the region in which ghosts and flares are symmetrical with respect to the optical axis of the photographing lens changes depending on changes in the configuration and extension amount of the photographic lens. In addition, with the active automatic focus detection method (hereinafter simply referred to as active AF), which projects light onto the subject from the camera side and uses the reflected light to adjust the focus, there is a natural limit to the distance at which the focus can be adjusted. , the passive automatic focus detection method (which does not have a limit on the detection range and adjusts the focus by relying on external light without projecting a projection light for focus detection) is not fully compatible with photographic lenses with long focal lengths. It would be wise to consider using it in combination with passive AF (hereinafter simply referred to as passive AF).

Furthermore, in either system, in order to effectively utilize the functions of a -eye reflex camera, it is necessary to have the ability to sufficiently adapt to various interchangeable lenses with different aperture f-numbers and focal lengths.

For this purpose, it is necessary for the light-receiving optical axis to look at an area extremely close to the photographic lens optical axis. However, when arranged in this way, as understood from the above, the active A
The purpose of the present invention is to prevent the effects of ghosts and flares caused by reflection between the surfaces of the photographic lens, increase the amount of projected light as much as possible, and increase the distance at which focus can be detected. An object of the present invention is to provide an extended focus detection device.

Another object of the present invention is to improve the configuration, open F value, and extension amount of the photographic lens during active AF.

It is an object of the present invention to provide a focus detection device that changes the aperture aperture of a light projecting optical system according to zooming or the like and is not affected by glare or flare caused by reflection between surfaces of a photographic lens.

(Means for Solving the Problem) The first invention of the present application has a light projecting means for projecting light from the rear of the photographing lens with the optical axis of the photographing lens off-axis, and A focal point that detects the focal state of the photographic lens by a light receiving means that receives an image formed by a secondary image forming means arranged in the light emitting means, and performs focus detection using the light emitted from the light projecting means and reflected from the subject. A detection device comprising a light projecting optical system disposed near a planned image forming surface of a photographing lens and an aperture optical system having a sector-shaped aperture disposed immediately adjacent to the light projecting optical system. It is a feature.

That is, in the first invention of the present application, since the aperture of the diaphragm optical system disposed in the immediate vicinity of the light projection optical system is formed in a fan shape, the effects of ghost and flare due to inter-plane reflection of the photographing lens can be avoided. First, the amount of projected light can be made as necessary and sufficient.

The second invention of the present application has a light projecting means for projecting light from the rear of the photographing lens off the optical axis of the photographing lens, and a secondary imaging means disposed behind the expected image forming plane of the photographing lens. A focus detection device that detects the focus state of a photographic lens by a light receiving means that receives a formed image, and performs focus detection using passive AF using external light and light emitted from the light projecting means and reflected from the subject. There is a light projection optical system disposed near the expected image forming surface of the photographic lens, an electro-optical element disposed in the immediate vicinity of this light projection optical system, and a light transmission area of this electro-optical element that is connected to the photographic lens. It is characterized by comprising a light transmitting area control means that changes according to information possessed by the light transmitting area.

That is, in the second invention of the present application, an electro-optical element is disposed in the immediate vicinity of a light projecting optical system disposed near the expected imaging plane of the photographic lens, and during active AF, the configuration of the photographic lens, the aperture F value, The transmission area of the electro-optical element is made variable according to the amount of extension, zooming, etc., and the aperture aperture of the projection optical system is changed to avoid the effects of ghosts and flare caused by inter-plane reflection of the photographic lens. It is.

” The first and second inventions of the present application are active A,
This was made based on the following consideration by the inventor of the present application regarding flare at F time.

Considerations regarding flare and ghost by the inventor of the present application will be explained using FIGS. 9 to 13.

FIG. 9 is an example of a focus detection optical system (light receiving system).

L is a photographing lens, F is its focal plane, and behind it is a focus detection optical system A. is located. Q and P are the masks placed on the lens curvature, respectively, and C is the COD
It is a light receiving element such as.

FIG. 10 is a view of FIG. 9 viewed from a 90' different direction.

The principle of focus adjustment is to measure the distance by detecting the correlated position of two images created by the subject light beams that have passed through the first and second parts of the photographic lens that sandwich the optical axis of the photographic lens. In FIG. 10, a condenser lens L is placed via a mask Q near a position equivalent to the focal plane F of the photographic lenses I and O.

Further, imaging lenses Lt and I-3 are arranged in two openings of the mask 1 behind the condenser lens L,
Left and right line sensors (see C in FIG. 9) using COD, for example, are interposed between the imaging planes 6, respectively. The image of the object to be focused is formed in front of the focal plane F, so-called re-imaging 8a, 9a of the line sensor area of the front bin image 7a approaches the optical axis OC, and conversely, the rear bin image 7a approaches the optical axis OC. Reimages 8b and 9b of the image 7b move away from each other from the optical axis OC.

In the case of focusing, the distance between two mutually corresponding points of re-imaging 8c and 9c of the image 7C has a specific size determined from the configuration of the optical system. Therefore, by converting the light distribution pattern of the image on the line sensor into electrical signals and determining their relative positional relationship, the distance to the object to be focused can be determined.

FIGS. 11(a) and 11(b) are examples of optical path diagrams of a light projection optical system for explaining flare and ghost caused by inter-plane reflection of a photographic lens. Note that to simplify the explanation, the projection optical system is omitted and only the light beams are shown.

The light projected from a point O on the focal plane on the optical axis OC of the photographic lens at an angle slightly tilted to the optical axis OC of the photographic lens L as shown in the figure is the optical axis L of the photographic lens. The light rays are reflected from each of the surfaces 1 to 11 and return toward the focal plane F, but in FIG.
The surface was shown. Further, FIG. 11(b) shows a ray of light returning toward the focal plane F after being reflected three times in the case where the number of reflecting surfaces is 6 - 1 - 6.

Since the light projected from one point 0 on the focal plane F is projected slightly tilted upward with respect to the optical axis OC of the photographing lens, the image of the flare light on the surface of the first mask Q is
As shown in FIG. It occurs point-symmetrically with respect to.

Note that in FIG. 12(a), each circle corresponds to flare light reflected from each surface of the photographic lens.

Although only the light beam reflected once is shown here, the same applies to the light beam reflected three times or more.

In addition, FIG. 12(b) shows the second mask (aperture mask) P
The figure shows an image of flare light on the surface of
, the flare light is greatly reduced. Second
On the surface of the mask P, the straight line j', to' and the area S+'+S! ' corresponds to the straight line j on the surface of the first mask Q and the region S1°S.

FIG. 13 shows how this flare light changes with different types of photographic lenses.

Similar to FIG. 12(b), this shows flare light on the surface of the aperture mass 72. Upper row? This figure shows the case where the photographic lens is extended at the flash position, and the bottom line shows the case at the closest position. The shape of flare light is quite different between a 50/1.7 standard lens (Nigauss type lens configuration) and a 35-105/3.5-4.5 zoom lens. Furthermore, even with the same 35-105/3.5-4.5 zoom lens, the zooming conditions vary greatly depending on the zooming state.

In the case of (L) (105 mm), the flare light is blocked by the aperture mask, but in the case of (S) (35 mm), the flare light is blocked by the aperture mask.
In m), there is a light ray passing through the aperture mask P. Furthermore, it changes slightly depending on the amount of payout.

In this way, if the aperture mask P is located in a region close to the optical axis OC, it will be greatly affected by fluctuations in flare light that occur during zooming and extension.

Therefore, the aperture aperture P of the second mask is as shown in FIG. 12(b).
As is clear from FIG. 13, there are photographing lenses L on the left and right sides of the optical axis OC. It is formed at a position as far away from the optical axis OC as possible within a region defined by the release F value of . On the other hand, the aperture aperture of the light projection optical system uses the second mask as a photographing lens. When projected onto the entrance pupil plane, it may be located within a fan-shaped area Sl between the two apertures P. In order to increase the amount of projected light as much as possible, the diaphragm aperture of the projection optical system may be fan-shaped in accordance with the shape of the region S1.

(Function) In the first invention of this morning, the light projecting means projects light onto the subject with the optical axis of the photographing lens removed from the rear of the photographing lens. The light projected onto the subject and reflected passes through the photographing lens and is imaged by the secondary imaging means. This image is received by the light receiving means and the focal state of the photographic lens is detected. A diaphragm optical system disposed in the immediate vicinity of the light projection optical system narrows down the amount of light projected from the light projection means to be as large as possible without being affected by ghosts or flares due to inter-plane reflection of the photographic lens.

In the second invention of the present application, the transmission area of the electro-optical element is controlled by the light transmission area control means according to information held by the photographing lens, and the amount of light projected from the light projecting means is narrowed down, Avoid being affected by ghosts and flares caused by inter-plane reflections.

(Example) Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of a single-lens reflex camera having a focus adjustment device that takes measures against the influence of flare light.

In FIG. 1, 10 is a camera body, 11 is an exchangeable photographing lens, and 12a and 12b are reflex mirrors, which reflect the light that has passed through the photographic lens 11 to the viewfinder, and also transmit some of the light. It also leads to the focus detection optical system 14. The reflex mirror 12a is
Move in the direction of arrow A. On the other hand, reflex mirror +
2b moves in the direction of arrow A and retreats. This is to prevent the optical path of the optical member 15 from being kicked.

Also, one is a light shielding member, reflex mirror = 12
After retracting, the mirror b rotates in the direction of the arrow to cover the reflex mirror 12b and prevent harmful reflected light from entering the film.

I3 is a total reflection mirror, 15 is an optical member disposed inside the camera body, and this optical member 15 includes an LED I
A half mirror 15a is provided which reflects the wavelength of light emitted from the mirror 8 and transmits visible light. Here, the angle of the half mirror 15a is formed so that the light beam emitted from the LED 18 passes through a point on the optical axis on the planned focal plane and is tilted at a slight angle with respect to the optical axis OC of the photographic lens. , LEDlB passes through a portion other than the optical axis of the photographic lens 11 and is projected to the outside. 1
7 is a light projecting lens for condensing and projecting the light emitted from the LED l 8, and 16 is an electro-optical element having a fan-shaped aperture aperture disposed immediately in front of the projecting lens.

FIG. 2 shows a detailed diagram of the focus detection optical system 14.

11 is a photographing lens; 21 is an aperture 21a disposed near the expected focal plane of the photographic lens 11 and elongated in the left-right direction;
What is the mask for? 22 is a condenser lens placed immediately after the mask 21. Reference numeral 23 denotes an aperture plate having two left and right elliptical apertures 23a and 23b, and secondary imaging lenses 27 and 28 are arranged behind it, and the light beams passing through the aperture are collected from a one-dimensional array such as a COD. The image is formed on the light receiving element 24. The light receiving element 24 is the aperture 23
The light rays passing through the optical paths 20a and 20b of the pupil plane 2 of the photographing lens 11 are received through the optical paths 20a and 23b, respectively.

Note that I5 is the optical member 15 in FIG.
It serves to deflect the light projected by the lens 11 toward a region on the pupil plane of the photographic lens 11 that is outside the optical paths 20a and 20b of the light receiving optical system.

FIG. 3 shows the relationship between the optical paths 20a and 20b of the light receiving optical system and the optical path 20c of the projecting optical system on the pupil plane of the photographing lens 11. The optical paths 20a and 20b of the light-receiving optical system are located in a region (angle θ indicated by dotted lines
2) area). Circle CR is the light receiving optical system 20a.

20b, and by configuring the projection light to pass through this circle, it is possible to use a dark lens with a large open F-number even when using an active AP, as with a passive AP. In addition, by making the projection optical path 20c fan-shaped as shown in FIG. 3, the amount of light passing through the circle CR is increased as much as possible, and the distance over which focus can be detected is extended.

Next, FIGS. 4(a) and 4(b) show the detailed configuration of the electro-optical element 16 having a fan-shaped diaphragm aperture in FIG.
).

In FIGS. 4(a) and 4(b), 30 is a fan-shaped aperture plate provided on the surface of the electro-optical element 16.

Reference numeral 31 denotes a colorless and transparent glass plate, and the fan-shaped aperture plate 30 described above is provided in close contact with the outer surface of the plate. Further, the inner surface of the glass plate 31 is coated with a fan-shaped transparent conductive film 32 as shown in FIG. are doing. This transparent conductive film 32 is connected to the fan-shaped aperture plate 3.
It is made somewhat smaller than the opening of 0. 33 is an electrochromic film such as tungsten oxide or iridium hydroxide, and 34 is an electrolyte.

For example, if the electrochromic film 33 is made of tungsten oxide, it is colored by setting the transparent electrode 32 in contact with it to a negative potential and applying electricity, and if it is made of iridium hydroxide, it is colored by setting it to a positive potential and applying electricity. .

36 is a colorless and transparent glass plate similar to the glass plate 31, and its inner surface is coated almost entirely with a transparent conductive film 35. This transparent conductive film 35 constitutes the other electrode of the electro-optical element.

FIG. 5 shows the spectral transmittance of the electro-optical element 16. Curve (1) is the characteristic when decolored, and curve (11) is the characteristic when colored.

Coloring mainly occurs due to increased absorption of near-infrared to red light, but when the wavelength of LEDI 8 for light projection is increased to 7.
If selected for the near-infrared region of 00 nm or more, this electro-optical element I
6 functions as a gloss in a colored state and a decolored state.

Therefore, current is applied between the transparent conductive films 32 and 35,
If it is in a colored state, light will be projected through area A of the sector-shaped diaphragm plate 30 in FIG. 4(a). On the other hand, in the decolorized state, light is projected through the entire fan-shaped area (A+B).

In addition, in FIG. 4(b), 37 to 40 are conductors, and 41 and 42 are sealing materials. Therefore, the transparent conductive film 3
In order to energize the conductors 2 and 35, the conductors 37 and 38 or the conductors 39 and 40 may be energized.

In this way, during active AP, by switching between the areas A and (A+B) of the light rays passing through the fan-shaped diaphragm plate 30, the effects of flare and ghosts due to inter-plane reflection of the photographing lens +1 are removed.

For example, in Figure 13, 50/1.7 and 35-10
When using the 5/3.5-4.5 (L) photographing lens 11, the focus is adjusted by the projected light passing through the area (A+B) of the sector-shaped diaphragm plate 30, and the 35-105/3.5- 4.5
When using the photographic lens (S), the fan-shaped aperture plate 30
By adjusting the focus using the projected light that passes through the area A, the projected light flux is determined and the effects of flare and ghosts are removed and the focus is adjusted.

This sacrifices the amount of projected light only for the photographic lens 11, where the effects of flare and ghost cannot be ignored.

As explained in Fig. 13, the appearance of flare and ghosts depends on the difference in the photographic lens 11, and also changes depending on the zooming and extension amount, so it is necessary to take these into consideration when switching. It is.

Figure 6 shows the emission wavelength (Ill
) and an infrared cut filter (m). This infrared cut filter (m is placed in the optical path of the focus detection optical system 14 and is used to cut infrared light. This is to reduce the shift in focal position due to chromatic aberration of the photographic lens [1.
This is why the wavelength is set to 70 Or+m.

FIG. 7 is a block diagram of the focus detection circuit. 50 is a focus detection circuit, and 51 is a microcomputer (hereinafter abbreviated as "microcomputer"), which calculates the output of the focus detection circuit 50 and drives a motor 53 by a lens drive circuit 52 to drive the photographing lens 11. The focus is adjusted. 54 is a ROM provided in the photographic lens 11.
1 (open F-number, focal length, amount of extension, amount of spherical aberration, etc.) is stored, and information on flare and ghost during active AP is also stored.

This flare and ghost information is read out each time according to the zooming or extension amount, and has the role of changing the aperture aperture of the electro-optical element 16. 5
Reference numeral 5 denotes a photometric circuit which outputs a signal to enter the active AP mode when the brightness of the outside world is lower than a certain level based on the subject brightness information measured by the light receiving element.

When this signal is output to the microcomputer 51, the microcomputer 51
Becomes ready to emit light at 1℃■)18. Furthermore, with reference to the information in the ROM 54 arranged in the photographing lens Jl, a signal is sent to the electro-optical element +6 to determine the passage area of the light to be projected after passing through the fan-shaped diaphragm plate 30 (see FIG. 4(a)). (See FIG. 4(a) and FIG. 4(b)).

The focus detection operation is started by touching a shutter button or the like, and the information read out from the ROM 54 is updated according to the movement of the photographic lens 11, and a light beam corresponding to flare or ghost is projected each time. , 56 is a light emitting circuit, which controls the light emitting timing of the LED+8 based on the command from the microcomputer 5.

57 is a display circuit that controls the lighting of the display element 58 based on the output information of the microcomputer 51 to indicate in-focus or out-of-focus status, and also provides information to the user when a photographing lens 11 that cannot perform active AP is attached. It serves to issue a warning signal to that effect. What is the photographic lens 11 in which active AF is not possible?
Even after taking the measures mentioned above, this lens still cannot remove flare and ghost.

In the embodiment shown in FIG. 1, the optical member 15 is configured to be detachable from the camera body 10, and the focusing plate can be replaced by removing the optical member 15.

(Effect of the invention) As is clear from the detailed description above, the first aspect of the present application
According to the invention, the aperture of the aperture of the projection optical system is fan-shaped,
Since the amount of light projected onto the subject from the light projecting means is increased within a range where the effects of ghost and flare due to inter-plane reflection of the photographic lens are prevented, the distance over which focus can be detected can be extended.

Further, according to the second invention of the present application, during active AP, the aperture of the diaphragm of the light projection optical system is made variable according to the information stored in the photographic lens, thereby eliminating the effects of interplane reflection and ghosting. Therefore, the number of usable photographic lenses can be increased in active A and F modes.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a single-lens reflex camera equipped with a focus detection device according to the present invention, Fig. 2 is a detailed diagram of the optical system of the focus detection device of the single-lens reflex camera shown in Fig. 1, and Fig. 3 is a light receiving optical system. An explanatory diagram showing the relationship between the optical path of the optical path and the optical path of the projection optical system on the photographing lens pupil plane, FIG. 4(a)
4(b) is a cross-sectional view of the diaphragm plate of FIG. 4(a) taken along the x-X line; FIG. 5 is an explanatory diagram of the spectral transmittance of the electrochromic material; The figure is an explanatory diagram showing the relationship between the emission wavelength of the LED and the infrared cut filter. FIG. 7 is a block diagram of the focus detection circuit. Figures 8(a) and 8(b) show the illumination distance range using a TTL interchangeable lens camera equipped with a conventional focus detection device, a strobe focus detection system with a built-in auxiliary illumination device, and an auxiliary illumination device, respectively. 9 and 10 are explanatory diagrams of the focus detection optical system of the focus detection device, respectively. 12(a) and 12(b) are images of flare light on the first mask surface and the second mask surface, respectively, in FIG. 9. FIG. 13 is an explanatory diagram that does not show changes in flare light due to the photographic lens. 14... Focus detection optical system, 16... Electro-optical element, 17... Light projecting lens, I8... L E D. 20a, 20b, 20cm--Optical path 21... Mask, 22... Condenser lens, 2
3... Aperture plate (23a, 23b... Aperture) 24...
・Photodetector, 27.28...Secondary imaging lens, 50・
...Focus detection circuit, 51 microcontroller. Patent Applicant Minolta Camera Co., Ltd. Agent Patent Attorney Aoyama Baka 2 @1 Figure 10/' Figure 2 Figure 3 Figure 5 - 15 Yasunaga + nml Figure 7 Go to Figure 10 LO5

Claims (2)

[Claims] (1) It has a light projection means that projects light from the rear of the photographic lens off the optical axis of the photographic lens, and the image formed by the secondary image forming means arranged behind the intended image forming plane of the photographic lens. A focus detection device that detects the focus state of a photographic lens using a light receiving means that receives light, and performs focus detection using light emitted from the light projecting means and reflected from the subject,
A focus detection device comprising: a light projection optical system disposed near a projected image forming surface of a photographing lens; and a diaphragm optical system having a fan-shaped aperture disposed immediately adjacent to the light projection optical system. . (2) It has a light projection means that projects light from the rear of the photographic lens off the optical axis of the photographic lens, and the image formed by the secondary image forming means arranged behind the intended image forming plane of the photographic lens. A focus detection device that detects the focus state of a photographic lens using a light receiving means that receives light, and performs focus detection using light emitted from the light projecting means and reflected from the subject,
The photographic lens has a light projection optical system disposed near a planned image forming surface of the photographic lens, an electro-optical element disposed in the immediate vicinity of the light projection optical system, and a light transmission area of the electro-optical element. 1. A focus detection device comprising: a light transmission area control means that changes the area according to information about the focus detection device.