JPH02181109A - Automatic focusing device for camera - Google Patents

Abstract

PURPOSE:To enable accurate focus detection by performing the focus detection in consideration of the best image plane position of a subject image which is displaced according to a control aperture value in film exposure. CONSTITUTION:This device has a means which receives a spherical aberration signal corresponding to the quantity of extension of a photographic lens 1 and a correction quantity generating means which outputs the difference (focus correction quantity) between the best image plane of subject light guided onto a film surface and the best image plane of subject light with an aperture equivalent F value according to the signal. Further, the device has a correction signal output means 17 which adds the quantity of defocusing and the quantity of focus correction together and a means which drives the photographic lens 1 so that the addition output is zero. Consequently, the focus detection which enables accurate in-focus photography is performed in film exposure.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic focus detection device for a camera that can accurately detect the focus of a photographic optical system.
(1) In conventional camera automatic focus detection devices, subject light is guided onto a photoelectric conversion means through a focus detection optical system, and the photographing optical system focuses on the film surface by the output of the photoelectric conversion means. There is something to detect whether or not. In particular, in a focus detection optical system that uses light that has passed through a photographic lens for focus detection, there is a predetermined aperture equivalent F value. In such an apparatus, the aperture equivalent F value of the focus detection optical system is always constant. However, the F value of the photographing optical system varies each time exposure is performed by manual control or automatic control, and the best image plane position changes depending on the F value controlled each time. Therefore, there is no problem if the aperture equivalent F value of the focus detection optical system matches the F value of the photographing optical system when the film is actually exposed, but if the two F values are different (this (with a high probability), even if focus is detected by the output of the photoelectric conversion means, the best image plane position of the photographic optical system and the film plane will deviate during exposure, making it difficult to achieve accurate focusing. I can't.

In other words, the conventional device has the drawback of not being able to perform accurate focus detection. Furthermore, conventional apparatuses that use a focus detection optical system separate from the photographic optical system also have the disadvantage that a phenomenon similar to the above occurs due to a change in the F value during exposure.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and to provide an automatic focus detection device for a camera that enables focus detection that enables accurately focused photography during film exposure.

Embodiments of the present invention will be described below based on the accompanying drawings.

FIG. 1 shows an example of a focus detection device.

This device passes light from two regions 1A and 1B symmetrical with respect to the optical axis in the exit pupil 11 of a photographic lens 1 through a lenslet array 6 arranged at a position 2 conjugate with the film plane.
The light is incident on a pair of self-scanning photoelectric element arrays 4 such as a COD type image sensor or an MO8 type image sensor, and focus detection is performed based on the phase difference between the output signals from these photoelectric element arrays 4. The light from the area i'A of the exit pupil 1' enters the A group (Ao...Ai -An) of the photoelectric element array 4, and the photoelectric element array 4
Since the light from the area i'B of the exit pupil 1' is incident on the B group (Bo-Bi-Bn) of , the output signal of each photoelectric element array group is the light coming from the corresponding area of the exit pupil. This is a signal representing the subject image created by Here, a surface 2 conjugate with the film surface serves as a focus detection surface.

As shown in FIG. 2, when in focus, the exit pupil 110
The two object images that pass through the two regions 1'A and 1'B and are formed at a position 2 conjugate to the film plane coincide on a plane perpendicular to the optical axis.

Therefore, the output signals of the A group of the photoelectric element array 4 and the output signals of the B group also match without deviation, as shown in FIG.

Next, as shown in Fig. 4, when the rear bin state is present, the exit pupil 1
2 created by passing through the two regions 1'A and 1'B of '
The positions of the two subject images are shifted at position 2, which is conjugate with the film plane.

Therefore, the output signals of group A and the output signals of group B of photoelectric element array 4 produce a phase difference d1 as shown in FIG.

Next, when the front is in focus as shown in Figure 6, the positions of the two subject images created by passing through the two areas 1°A and i'B of the exit pupil 1° are conjugate with the film plane. 2, a shift occurs in the opposite direction to that in the case of the rear pin described above.Therefore, the output signals of group A and the output signal of group B of the photoelectric element array 4 are different from those in the case of the rear pin as shown in FIG. Reverse phase difference d
2.

As described above, when the above-described focus detection device is used, the point where the phase difference between the output signals of group A and group B of the photoelectric element array 4 is ○ is detected as the in-focus state, and the sign of the phase difference is used to detect the point in focus. It is possible to detect pins and post-pins. Furthermore, by detecting the amount of phase difference dls a2, it is possible to detect the amount of defocus from the in-focus state in the front focus or back focus state.

FIG. 8 shows an example in which such a focus detection device is incorporated into a single-lens reflex camera.

The photographing lens 1 is an interchangeable lens that can be attached to and detached from the camera body 5. The quick return mirror 6 has a semi-transparent mirror in its center, and guides reflected light to the finder optical system 7, 8.9, and guides transmitted light to the submirror 10. The sub-mirror 1o includes a lenslet array 3 and a photoelectric conversion element array 4 arranged on the bottom of the camera body.
-6 transmitted light is guided. 2' indicates the film surface. The lenslet array 6 and the photoelectric conversion element array 4 are arranged at a position conjugate with the film surface 2" and in the vicinity thereof, as described above. Focus detection is performed with the aperture open, but the aperture of the focus detection optical system The equivalent F-number is set so that the light flux for focus detection will fit within the exit pupil of the interchangeable lens used when the aperture is open, or in other words, the focus detection light flux should be set so that vignetting is prevented by the exit pupil of the interchangeable lens used when the aperture is open. Therefore, this aperture equivalent F value remains constant even if the interchangeable lens changes.Strictly speaking, the aperture equivalent F value of the focus detection optical system is determined by the light receiving surface of each photoelectric conversion element. It is determined by the size, direction of the light receiving surface, distance from the lenslet array, etc.

Now, the interchangeable lens attached to the camera body 5 has spherical aberration as shown in FIG.
The value is FT, 2, and the aperture equivalent F of the focus detection optical system
Assume that the value (θ) is F8. If focus detection is performed with the aperture of interchangeable lens 1 open, the equivalent aperture F value of the focus detection optical system will be F regardless of the open F value of lens 1, F1.2.
Since the value is constant at 8, it is detected that the interchangeable lens 1 is in focus when the best image plane at this F number is on the focus detection surface 2. The focus detection plane 2 is the best image plane position at F8, that is, the position corresponding to al in FIG.
Focus detection will be performed at position l. When a shunter release operation is performed after detecting the in-focus state at such a position, driving of the photographic lens 1 is prohibited in conjunction with this operation, and the lens is held at that position. At the same time, the aperture of the photographic lens 1 is gradually narrowed down, and the best image plane position moves toward the paraxial image point 0 from the position a2, which was the best image plane at Fl,2. And the F number to obtain the proper exposure is F
56, the drive of this aperture is stopped when the aperture reaches F5.6. The best image plane position at that time is a
It is 3. While the photoelectric conversion element detects the best image plane position at F8, the aperture of the photographic lens is F5.6.
Therefore, a difference of (a3al) will occur on the optical axis between the best image plane position a3 at F5.6 and the best image plane position a1 at the time of focus detection. Of course, if the aperture is controlled to F8, the best image plane position at this time is al, and the best image plane positions at film exposure and focus detection coincide, and the best image of the photographing lens 1 is placed on the film 2. The subject will be focused and the image will be taken in precise focus. However, as mentioned above, if the F value differs during film exposure and focus detection, the best image plane position a3 of the photographic lens 1 will change from al to (a
3a+), and even though the in-focus state has been detected correctly, an accurately focused photograph cannot be taken during film exposure. This is true unless the F value of the photographic lens 1 is controlled to F8 during film exposure.

Next, a case will be described in which the interchangeable lens 1 is replaced with a different type of interchangeable lens. For example, assume that a newly installed interchangeable lens has a spherical aberration as shown in b in FIG. 9, and that the open F value of the interchangeable lens is Fj, 4. Of course, the aperture equivalent F value of the focus detection optical system is constant at F8. When the aberration curves are different in this way, if the lenslet array 3 and the photoelectric conversion element array 4 are fixed to the camera body 5, and the aperture equivalent F value of the focus detection optical system is constant at F8, the focus detection surface 2 The position where the best image plane is located is shown on the aberration diagram.

Therefore, on the aberration diagram in FIG. 9, the focus detection surface 2 is fixed at a position b1 shifted from the paraxial image point 0,
Focus detection will be performed at this position bl. Then, if you close down the aperture after detecting focus, it will be F as described above.
The best image plane position moves from position b2, which was the best image plane at T, 4, toward the paraxial image point 0, and the best image plane when the aperture is stopped at the F value that obtains the appropriate exposure. Position b3 is bl
The camera is shifted by (b3bl) from , and it is still not possible to take an accurately focused photograph. Furthermore, even if film exposure is performed at the same F-number for lenses with aberration curves a and b, the amount of deviation (a3a+) between the focus detection plane 2 and the best image plane position at the controlled F-number, b3bl) differs from lens to lens. In other words, when the aberration curves differ depending on the interchangeable lens, focus detection is performed in the same way, and even if the aperture is controlled to the same F number during film exposure, the best image plane positions a3 and b3 and the focus detection plane at the F number are the same. a1
, b, and the deviation amounts (a3-al) and (b3b+) will be different.

Furthermore, in order to enable focus detection even when various types of interchangeable lenses are attached to the camera body 5, the focus detection light flux must not be eclipsed when the various types of interchangeable lenses are in the open aperture state.

FIG. 10 is a diagram explaining this. In the same figure a
l represents the exit pupil of interchangeable lens a in the open state, bl represents the exit pupil of interchangeable lens b in the open state, C' represents the exit pupil of interchangeable lens C in the open state, and θ is the aperture of the focus detection optical system. This corresponds to the equivalent F value.

As can be seen from these, the aperture equivalent F value of the focus detection optical system inevitably becomes a large value. Therefore, the amount of out-of-focus during shooting as described in Figure 9 is controlled to a larger value as the aperture equivalent F-number of the focus detection optical system is set to a larger value, and the control F-number during film exposure is controlled to a smaller value. As a result, it becomes impossible to accurately focus on the film surface 2+.

These drawbacks can be solved by an electrical processing system provided in the camera body 5, which will be described next. In FIG. 11 showing the electrical processing system of the device described so far,
1 is a photographic lens movable in the optical axis direction, 3 is a lenslet array, and 4 is a photoelectric conversion element array. The lenslet array 5 and photoelectric conversion element array 4 are fixed to the bottom of the camera body 5 as shown in FIG.

The equivalent aperture F value of such a focus detection optical system is determined so that no matter what kind of interchangeable lens 1 is attached, the light from the exit pupil of the interchangeable lens 1 used will not be vignetted when the aperture is open. , remains constant even if the attached interchangeable lens changes. In the example described above, this aperture equivalent F value is F8. Therefore, the output of the photoelectric conversion element array 4 is always the output at F8 when the interchangeable lens 1 is in the open aperture state. The focus detection circuit 1 includes a photoelectric conversion element array 4
The phase difference dl between the output of group A and the output of group B
t d2 is detected.

The conversion circuit 12 receives the output of the focus detection circuit 11 and calculates how much the focus has shifted in the optical axis direction from a state where the phase difference is zero, that is, a state where the best image plane is on the focus detection surface 2. The A/D converter 13 A/D converts the output of the conversion circuit 12 and converts the amount of out-of-focus into a digital signal. Hereinafter, this will be referred to as the defocus detection amount.

The lens identification signal circuit 14 receives a signal from a signal bin provided on the interchangeable lens barrel, identifies what type of interchangeable lens attached to the camera body 5 is, and issues a signal according to the type of the interchangeable lens. . That is, if we explain using FIG. 9, the circuit 14 is a circuit for identifying whether the aberration curve of the attached lens takes the aberration curve a or the aberration curve b by receiving a signal from the signal bin. Yes, and generates a signal depending on the type of interchangeable lens. When the control aperture signal circuit 15 manually sets the F value,
It receives a signal from a signal bin provided on the interchangeable lens barrel and moves in conjunction with the aperture ring, and generates a signal corresponding to the manually controlled #F value. In addition, when automatically setting the F value for obtaining proper exposure using the automatic exposure control circuit in the camera body 5, a signal is received from this automatic exposure control circuit, and the automatic control F value is set automatically.
Generates a signal according to the value. In this way, signal circuit 1
5 generates a signal corresponding to the F value actually controlled during film exposure. Decoder 16 receives signals from signal circuits 14 and 15, and outputs address signals (digital signals) according to both signals. The storage circuit 17 stores the amount of deviation between the best image plane position of the interchangeable lens at the aperture equivalent F-number and the best image plane position at its control F-number, and receives the address signal from the decoder 16 and stores the deviation amount according to the amount of deviation. The output signal is output as a digital signal. To explain this with reference to FIG. 9, the memory circuit 17 is stored in a
) or (b3b+) is output as a digital signal.

Hereinafter, this output will be referred to as a focus correction amount depending on the interchangeable lens and the controlled aperture value. Note that this focus correction amount (a3nl), (
b3b+) remains approximately constant even if the photographing lens 1 moves along the optical axis direction (that is, even if the photographing magnification changes).

The correction circuit 18 receives each output from the A/D conversion circuit 13 and the storage circuit 17, and adds the re-outputs. In other words, this addition output is a signal corresponding to the amount of deviation between the focus detection plane 2 and the best image plane at the aperture equivalent F value of the subject image (defocus detection amount), and a signal corresponding to the amount of deviation between the focus detection plane 2 and the best image plane at the aperture equivalent F value of the subject image, and a signal corresponding to the amount of deviation between the best image plane at the aperture equivalent F value and the control F value. This is the sum of the signal (focus correction amount) corresponding to the amount of deviation from the best image plane, and in other words, it corresponds to the amount of lens drive to guide the best image plane onto the film plane 2' during film exposure. .

If the output of the correction circuit 18 is zero, it means that the film surface 21 is accurately focused, and the correction circuit 18
If the output is a digital output other than zero, film side 2
"It can be seen that the focus is not accurately focused on the top. In the initial state of focus detection, the counter 19 is reset, and the comparator circuit 20 receives the outputs of the correction circuit 18 and counter 19, and compares the output of the correction circuit 18. The display circuit 21 receives the output of the correction circuit 18 and drives the display element 22.

In this way, the display element 22 displays the amount of lens drive to accurately guide the best image plane during film exposure to 2° above the film plane. Motor control circuit 23 receives the output of comparator circuit 20 and drives motor 24 . The motor 24 drives the lens 1 in the optical axis direction. Of course the motor control circuit 25
also controls the rotational direction of the motor 24 by the signal from the comparator circuit 20, so that the best image plane during film exposure is film plane 2.
The lens 1 is driven in the direction closer to 1. Pulse generator 2
5 generates Tahalus in accordance with the movement of the lens 1, and the Cauzota 19 counts the output pulses of the pulse generator 25. The comparator circuit 20 compares the digital value of the correction circuit 18 with the count value of the counter 19, and when this count value matches the digital value of the correction circuit 18, it is in focus, that is, the best image plane at the time of film exposure is the film. It is determined that it has touched surface 2'.

The display circuit 21 receives the comparative output of the focus detection circuit 20 while the lens 1 is moving, and the display element 22 constantly displays the lens drive amount until the lens is in focus. When the in-focus state is obtained, this is displayed. Motor control circuit 2
5 stops the motor 24 when the in-focus state is obtained, that is, when the comparison output of the comparison circuit 20 becomes zep. Comparison circuit 2
0 transmits a reset signal to the counter 19 to return it to zero at the same time as the in-focus state, and the focus detection circuit 1
1 to start the focus detection operation again. In this way, the focus adjustment operation is finally performed to bring the subject into focus. After the photographer confirms the in-focus state by the display on the display element 22, if the photographer presses the button to enter the V-Z operation, the diaphragm inside the interchangeable lens barrel will be narrowed down from the open state to the predetermined F value. The quick return mirror 6 is amplified and the shutter curtain is moved.In this way, film exposure is performed.However, in this embodiment, the F value is adjusted depending on the interchangeable lens attached and the F value controlled during film exposure. Since the camera adjusts the camera so that the best image plane is on the film, you can always take pictures that are in precise focus.

In the embodiments so far, we have described a device that automatically obtains a focusing state, but it is possible to remove the motor control circuit 23 and motor 24 from this device and obtain a focusing state by manually operating the distance ring. You can also do this. In that case, display element 22
From the display, it is also possible to know the operating direction of the distance ring, that is, the direction in which the lens 1 should be moved.

In addition, a signal pin is provided on the lens barrel of each interchangeable lens that moves in conjunction with the amount of lens extension, and the output voltage is changed on the camera body 5 side in accordance with the amount of lens extension, similar to circuits 14 and 15. By providing a signal circuit and inputting the output of this signal circuit to the decoder 16, it is also possible to correct the out-of-focus caused by a change in the photographing magnification of the lens 1.

Further, in the above embodiment, when the interchangeable lens 1 is attached to the camera body, in order to determine what type of lens (what kind of aberration curve it has), A signal was transmitted to the camera body 5 through one signal pin provided on the lens barrel of the lens 1.

However, a signal pin for transmitting the focal length of the interchangeable lens and a signal pin for transmitting the open F value of the aperture are provided on the lens barrel of the interchangeable lens 1, and the signals from both signal bins are transmitted together to the camera body side. By combining both signals, it may be possible to identify what type of lens the attached interchangeable lens is. FIG. 12 shows such another embodiment. In FIG. 12Q, an open F value signal circuit 261i includes a variable resistor 26a that changes the resistance value by an open F value signal bin provided in the lens barrel of the interchangeable lens when the interchangeable lens is attached to the camera body 5. , outputs a voltage according to the aperture F value of the interchangeable lens. The focal length signal circuit 27 includes a variable resistor 27a whose resistance value is changed according to a focal length signal bin provided on the lens barrel of the interchangeable lens when the interchangeable lens is attached to the camera body 5, and the resistance value is changed according to the focal length of the interchangeable lens. Output voltage. The addition circuit 28 includes the open F value signal circuit 26 and the focal length signal circuit 2.
7 and outputs a signal similar to that of the lens identification signal circuit 14. That is, circuits 26, 27, and 28 are the 11th
This circuit corresponds to circuit 14 in the figure. The output of the adder circuit 28 is input to the decoder 16 and processed in the same manner as in the previous embodiment (see FIG. 11). In the case of this embodiment, lenses having the same focal length and aperture F value are considered to be the same type of lenses, and the amount of focus correction that is the output of the storage circuit 17 is the same.

Furthermore, regarding different types of interchangeable lenses whose aberration curves shown in FIG. 9 are very similar, it is conceivable to set the output of the circuit 14 to be a constant signal no matter which lens group is attached.

Of course, it goes without saying that the output of the circuit 14 will change for interchangeable lenses with completely different aberration curves.

In the embodiments described so far, correction is made so that the best image plane is located on the film plane when the aperture is controlled from an open state to a minimum aperture state during film exposure. However, the aperture-equivalent F-number of the focus detection optical system is set to be a large F-number, as in a double series. Therefore, the smaller the aperture is controlled to the F value, the greater the amount of defocus may become. Taking this into consideration, the correction as in the serious crime embodiment may be performed only when the aperture is controlled to be fully open or close to it.

In the embodiments described so far, focus is detected from a subject image formed by visible light, and the subject image formed by visible light is guided to a film surface, or focus is detected from a subject image formed by infrared light. This method is applied when guiding a subject image formed by infrared light onto the film surface. Next, a case will be described in which focus detection is performed using infrared light and a subject image formed using visible light is guided to the film surface.

When the photoelectric conversion element 4 has high sensitivity to infrared light, the focus detection circuit 11 enters the focused state when the best image plane of the infrared light contained in the transmitted light of the photographing lens 1 comes onto the focus detection surface 2. Detected. However, even if infrared light and visible light pass through the same optical system, the best image plane position will shift due to chromatic aberration due to the difference in wavelength. Therefore, Figure 11 or 12
Even if the apparatus shown in the figure is used as is, it is not possible to bring the best image plane of the visible light contained in the light transmitted through the photographing lens onto the film surface 2'.

Therefore, from the aberration curve a1 for infrared light and the aberration curve a for visible light of the attached lens as shown in Figure 13e, the best image plane position of infrared light at the aperture equivalent F value of the focus detection optical system (aperture equivalent If the F value is F8, a, '),
The relationship between the best image plane position of visible light (a3 if the control F value is F5.6) at each control F value during film exposure is determined, and the best image plane position of infrared light described in Eiif and the above visible light are determined. The deviation between each best image plane position ffi (, a, l +
83) should be calculated in advance. This amount is the focus correction amount. Of course, this focus correction amount is calculated for each interchangeable lens that can be attached to the camera body. The focus correction amount corresponding to each control F value for each interchangeable lens may be stored in advance in the storage circuit 17. By doing this, when the interchangeable lens 1 is attached to the camera body 5 and the F value to be controlled is determined, a signal identifying the interchangeable lens is sent from the lens identification signal circuit 14, and a control signal is sent from the control aperture signal circuit 15. The signals corresponding to the F values are transmitted to the decoder 16, and the decoder 16 uses the signals corresponding to both signals as address signals to send to the memory circuit 1.
7. In response to this address signal, the storage circuit 17 outputs, as a digital signal, an overtranslation focus correction amount (a'l+83) corresponding to the attached interchangeable lens and the controlled F value. - 10,000, the A/D conversion circuit 13, the amount of deviation between the focus detection surface 2 whose position is fixed on the camera body 5 and the best image plane of the aperture equivalent F value formed by infrared light;
That is, the detected amount of defocus is output as a digital signal. Therefore, from the output of the A/D conversion circuit 13 and the output of the memory circuit 17, the correction circuit 18 calculates the amount of deviation (focus (amount of misalignment detected) and an amount corresponding to the positional difference (aj+a3) between the best image plane for visible light at the control F value of the lens and the best image plane at the aperture equivalent F value for infrared light (focus correction amount) Add. In other words, the lens driving amount is calculated to determine how much lens 1 must be driven from the lens position at the time of focus detection so that the best image plane for visible light at the control F value is located on the film surface. be done. When the lens 1 moves by an amount corresponding to the second lens driving amount, the correction circuit 18 and the counter 19
The comparison circuit 20 detects that the two outputs match, the comparison circuit 20 detects that the focus state is reached, and the motor 24 stops. In this way, even when focus is detected using infrared light, the best image plane according to the control F value of visible light is always positioned on the film plane, allowing for accurately focused photography.

In this example, circuits 11, 12, .
13 detects the in-focus state regarding infrared light of the photographing optical system, and a memory circuit 17) outputs a focus correction amount based on the positional deviation of the best image plane between visible light and infrared light of the photographing optical system. I will do it. The correction circuit 18 receives these two signals and outputs a lens drive amount such that the best image plane of visible light is on the film surface.

In the explanations so far, we have used a so-called TTL type focus detection device that performs detection using the light transmitted through the photographic lens, but there is an optical system for focus detection that is separate from the photographic lens. Of course, a so-called external light type focus detection device may also be used. In this case, there is no equivalent aperture F value, but the position that is the basis of detection by the focus detection optical system, that is, the focus detection surface, is determined at a certain position depending on the configuration of the detection optical system (this is the first position). Figure 9 alkasu.

), the correction may be performed in consideration of the amount of movement of the best image plane that changes depending on the control F value of the lens. Of course, this is done for each interchangeable lens.

As described in detail above, according to the present invention, focus detection is performed in consideration of the best image plane position of the subject image, which is displaced in accordance with the control aperture value during film exposure. Therefore, accurate focus detection can be performed.

[Brief explanation of the drawing]

Figure 1 is a basic principle diagram for explaining one embodiment of the present invention, Figures 2 to 7 are diagrams explaining the focus detection state of the apparatus shown in Figure 1, and Figure 8 is the apparatus shown in Figure 1. Figure 9 is an aberration diagram of the interchangeable lens, and Figure 1 is the exit pupil of the interchangeable lens when the aperture is open and the equivalent aperture F value of the focus detection optical system. 11 is a block diagram of an electrical processing system that is an embodiment of the present invention, FIG. 12 is a block diagram of another embodiment of the present invention, and FIG. 15 is an infrared FIG. 3 is an aberration diagram showing the relationship between an aberration curve of light and an aberration curve of visible light. (Explanation of symbols of main parts)

Claims (1)

[Claims] 1. In a camera that guides the light transmitted through a photographing lens to a focus detection device having an F value equivalent to a predetermined aperture and detects the difference (defocus amount) between the best image plane of the subject light limited by the F value and the film conjugate plane, means for receiving a spherical aberration signal corresponding to the amount of extension of the photographing lens; and a difference between the best image plane of the subject light guided onto the film surface and the best image plane of the subject light having the aperture equivalent F value according to the signal; (amount of focus correction); correction signal output means that adds the focus deviation amount and the focus correction amount; and means for driving the photographic lens so that the added output becomes zero. An automatic focusing device for a camera characterized by: