JPH06175012A - Focus detector for camera - Google Patents

Abstract

PURPOSE:To reduce power cosumption and to eliminate an unpleasant feeling given to an observer by efficiently performing finder display expressing the line-of-sight direction of a photographer and the driving of a lens. CONSTITUTION:A CPU 18 generates a 1st output signal in accordance with the line-of-sight direction in the visual field frame of the finder of a camera. When the output signal from the CPU 18 is an almost fixed value for a specified time or more, a lens driving circuit 8 drives the lens in order to adjust focus in the line-of-sight direction in accordance with the output signal. A temporal low-pass filter is applied to the output signal from the CPU 18, and a liquid crystal display part 21 displays the visual field frame nearly aligned with the line-of-sight direction in accordance with the output signal in the visual field frame of the finder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus detecting device for a camera, which adjusts a focus on a desired subject within a viewfinder frame of the camera.

[0002]

2. Description of the Related Art Conventionally, there has been proposed a technique for detecting the line-of-sight direction of a photographer looking into a viewfinder and performing various operations of a camera based on the line-of-sight information.

For example, Japanese Patent Application Laid-Open No. 4-190177 discloses a technique of displaying a line-of-sight region in a predetermined range substantially matching the line-of-sight direction on a viewfinder field frame and detecting the focus of a subject within the field-of-view region. There is. This technique detects a line-of-sight direction in a viewfinder frame of a camera, displays a line-of-sight region in a predetermined range substantially matching the line-of-sight direction on the field-of-view frame, and detects a focus of a subject in the line-of-sight region. Is. As described above, this technique is characterized in that the focus detection is performed based on the output within the predetermined range in the line-of-sight direction of the screen.

[0004]

However, in the technique disclosed in Japanese Patent Laid-Open No. 4-190177, the index indicating the direction of the line of sight faithfully according to the slight movement of the line of sight is displayed in the viewfinder frame. , The display makes the photographer feel uncomfortable.

Further, in the above technique, since the focus is always focused on the position of the index, the lens is driven every time the position of the index changes, so that the movement of the lens drive is wasteful and power consumption is further reduced. It also invites an increase.

The present invention has been made in view of the above problems, and it is an object of the present invention to reduce power consumption and observe by efficiently performing viewfinder display showing the photographer's line-of-sight direction and lens driving. Discomfort to a person may be eliminated, and a desired subject may be quickly and properly focused.

[0007]

In order to achieve the above object, the focus detection device for a camera according to the first aspect of the present invention is a first focus detection device according to the direction of the line of sight of the photographer in the viewfinder frame of the camera. First output means for generating an output signal, and lens driving means for driving a lens to focus in the line-of-sight direction according to the output signal when the output signal of the first output means is substantially constant for a predetermined time or longer. A display means for applying a temporal low-pass filter to the output signal of the first output means; and a display for displaying a visual field frame substantially coincident with the line-of-sight direction corresponding to the output signal of the filter means in the finder visual field frame. And means.

The focus detecting device for a camera according to the second aspect includes first output means for generating a first output signal according to the line-of-sight direction of the photographer in the viewfinder frame of the camera, and the first output means. When the output signal of the output means is substantially constant for a predetermined time or longer, the lens drive means for driving the lens to focus in the line-of-sight direction according to the output signal, and the lens drive means while driving the lens, And a control means for stopping the driving when the output signal of the first output means changes by a predetermined amount or more.

[0009]

That is, in the focus detecting device for a camera according to the first aspect of the present invention, the first output means generates the first output signal in accordance with the line-of-sight direction of the photographer within the viewfinder frame of the camera, When the output signal of the first output means is substantially constant for a predetermined time or longer, the lens driving means drives the lens to focus in the line-of-sight direction according to the output signal. And
The filter means applies a temporal low-pass filter to the output signal of the first output means, and the display means displays in the viewfinder field frame a visual field frame that substantially matches the line-of-sight direction corresponding to the output signal of the filter means. .

Further, in the camera focus detection device according to the second aspect, the first output means generates the first output signal according to the direction of the line of sight of the photographer within the viewfinder frame of the camera, and the lens driving means. When the output signal of the first output means is substantially constant for a predetermined time or longer, the lens is driven to focus in the line-of-sight direction according to the output signal. And
The control means stops the driving when the output signal of the first output means changes by a predetermined amount or more while the lens is being driven by the lens driving means.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block configuration diagram schematically showing the configuration of an automatic focusing (AF) camera to which the focus detection device of the present invention is applied.

As shown in the figure, the line-of-sight direction detecting sensor 15 is connected to a CPU 18 via an A / D converter 17, and the CPU 18 is provided with a line-of-sight detection start switch SW3. Further, the CPU 18 uses the sensor driver 16 to detect the line-of-sight direction sensor 1
5 and is also connected to the liquid crystal display unit 21 via the liquid crystal driver 20. And this CPU 18
Is also connected to the A / D converter 17 and the CPU 6.

Then, the photographing lens 1 and the focus detection optical system 2
The area image sensor 3 that receives a subject image incident via the is connected to the CPU 6 via the A / D converter 5, and the CPU 6 is connected to the area image sensor 3 via the sensor driver 4. With A /
It is also connected to the D converter 5. And this CP
U6 is connected to the liquid crystal display unit 12 via the liquid crystal driver 11, and is also connected to the lens drive circuit 8 for controlling the motor 9 and the exposure control circuit 13. further,
The CPU 6 includes an information input unit 14 and a photo interrupter 1
0 and the lens ROM 7 are also connected. And this C
The PU 6 is provided with a camera operation start switch SW1 and a release switch SW2. And CPU
A timer 19 is built in the device 18.

In such a structure, the area image sensor 3 photoelectrically converts the image formed by the focus detection optical system 2 into an electric signal, and the driver 4 drives and controls the area image sensor 3. It is a thing. The A / D converter 5 converts the analog output from the area image sensor 3 into a digital signal and outputs the digital signal to the CPU 6. The CPU 6 controls the entire camera other than the detection of the line-of-sight direction. Based on the output of the area image sensor 3, the subject distance is calculated, the aperture value and shutter speed are displayed, and the exposure is controlled.

Further, the lens ROM 7 is provided in the lens barrel, and stores various data necessary for focus detection such as the F number of the taking lens 1 and the conversion coefficient for obtaining the defocus amount from the image shift amount. To do. The lens driving circuit 8 moves the position of the photographing lens 1 by driving the motor 9 under the control of the CPU 6.

Usually, in the AF operation of detecting the subject distance and driving the taking lens 1 based on the distance information, it is necessary to feed back the driving amount of the taking lens 1 to the CPU 6. In this case, it is general that the moving amount of the photographing lens 1 actually moved is substituted by the rotation speed of the drive motor 9. Then, the photointerrupter 10 detects this rotation speed.

Further, the CPU 6 selects a signal of a predetermined area which substantially coincides with the line-of-sight direction in the viewfinder field frame from the photoelectric conversion output signal of the area image sensor 3, and defocuses the object within the predetermined area. In addition to averaging the sensor output signals in the predetermined area to obtain the average brightness Bv, the apex operation is performed together with the information such as the film sensitivity Sv, the shutter speed Tv, and the aperture value Av input from the information input unit 14. , Shutter speed Tv and aperture value Av are obtained. The shutter speed Tv and the aperture value Av are displayed on the liquid crystal display 12 via the liquid crystal driver 11.

Further, the timer 19 built in the CPU 18 is for measuring an accurate time, and the line-of-sight direction detecting sensor 15 converts an image formed by the line-of-sight direction detecting optical system into an electric signal. Photoelectric conversion.
The sensor driver 16 drives the line-of-sight direction detecting sensor 15, and the analog output signal of the line-of-sight direction detecting sensor 15 is converted into a digital signal by the A / D converter 17 and stored in the RAM in the CPU 18. To be done.

The CPU 18 is responsible for the overall control for detecting the line-of-sight direction. For example, the line-of-sight detection sensor 15 is provided.
Calculates the line-of-sight direction based on the output signal of, or displays the field-of-view frame in the finder field-of-view frame in a region substantially matching the line-of-sight direction. Then, this field frame is displayed on the liquid crystal display unit 21 via the liquid crystal driver 20, for example, as shown in FIG.
It is displayed as shown in (b). Next, FIG. 3 is an optical layout diagram showing in detail the optical system of the embodiment.

In the figure, the focus detection optical system 2 is
It is composed of a half mirror 32 provided between a front lens group 31 and a rear lens group 34 of the taking lens 1, a field lens 33, and a visual field transmission optical system 47 including a diaphragm, an optical axis tilt prism, and the like. The visual field transmission optical system 47
Is configured to divide the guided light flux into two by pupil division and form two images Ia and Ib on the area image sensor 3.

Then, a parallel light beam is produced from the infrared LED 42 through the lens 41, and the parallel light beam enters the eye 100 through the dichroic mirrors 40 and 39. Then, the light reflected by the eye 100 is reflected by the dichroic mirror 3.
An image is picked up by the sensor 44 through the lenses 9, 40 and the lens 43, and the line-of-sight direction is calculated.

In this way, the taking lens 31 and the main mirror 3
It is possible to detect the position of the gazing point observed by the photographer via the 5, slot 36, pentaprism 38, and dichroic mirror 39. In the figure, 45 is a shutter and 46 is a film. Here, the principle of focus detection in the present invention will be described. In the present embodiment, a phase difference method for obtaining the object distance from the interval between the two images Ia and Ib by dividing the pupil is adopted. That is, the taking lens 1
The light fluxes that have passed through the front group lens 31 and the half mirror 32 are split by the visual field transmission optical system 47, and are imaged as Ia and Ib on the area image sensor 3, respectively.

In this case, for example, at the time of focusing, FIG.
, The two images Ia, I
b is imaged at a predetermined interval fa. Further, when the subject is in focus before this focusing, the two images Ia and Ia as shown in FIG.
The spacing fb of b is narrower than the spacing at the time of merging. Furthermore, when the subject is in focus and the subject is back-focused, as shown in FIG.
As shown in, the distance fc between the two images Ia and Ib is wider than the distance fa at the time of focusing.

Therefore, the distance to the object can be calculated by calculating the distance between these two images Ia and Ib. The above is the principle of focus detection by the phase difference method. Next, regarding the principle of the gaze direction detection, for example, Japanese Patent Application Laid-Open Nos. 2-5 and 2-65834, or the Institute of Electronics and Communication Engineers technical report PRU88-73, PP17-
24.

These are methods for detecting the direction of the line of sight from the combination of the pupil of the eye and the corneal reflection image (first Purkinje image) or the combination of the iris and the corneal reflection image, and are attracting attention as a method of instructing the gazing point. Note that FIG. 4 shows an example of output waveforms of the corneal reflection image of the eye, the pupil, and the iris.

For example, FIG. 6 shows a corneal reflection image when the parallel light flux L enters the eye and the eye is looking at the center (solid line).
That is, it is a diagram showing the positional relationship between the first Purkinje image P and the first Purkinje image P ′ when the eye is looking in the direction of the angle θ (dotted line).

In the figure, the virtual images P and P'can be located at a distance of about r / 2 from the corneal surface, where r is the radius of curvature of the cornea. The movement of the eye is performed with the center C of the eyeball as the center of rotation. Then, when the eyeball rotates by θ _x , the center of the cornea moves from O to O ', and the image of the parallel light flux moves laterally by ￣ OCsin θ _x … (1) to reach the position of I'. become. ￣ OC is about 6 mm, so when θ = 5 °, the amount of change is about 0.5.
mm. As shown in FIG. 4, assuming that the x-coordinate of the pupil edge is x ₁ and x ₂ , the coordinate x of the center position C of the pupil is x.
_c is expressed as x _c = (x ₁ + x ₂ ) / 2 (2). Further, assuming that the x coordinate of the position P of the first Purkinje image is x _p , in the range where the rotation angle θ is small,

[0028]

[Equation 1] The relationship is established.

Actually, x _c and x _p are obtained by performing image processing on an image projected on the line-of-sight direction detection sensor 15 as shown in FIG. 4 through the line-of-sight detection optical system (magnification β). can get. By rewriting these x _c and x _p as x _c ′ and x _p ′,

[0030]

[Equation 2] Therefore, the vertical rotation angle θ _y can be obtained in exactly the same manner. If these θ _x and θ _y are known, the center coordinates (x, y) of the field frame that coincides with the line-of-sight direction in the finder field can be obtained from the finder optical system α magnification. Less than,
The operation of the focus detection apparatus according to this embodiment will be described with reference to the flowcharts of FIGS. 7 and 8 are flowcharts showing the operation of the CPU 18.

When the operation is started (step S100),
First, the CPU 18 causes the liquid crystal display unit 12 to display the AF visual field area in the center of the screen (step S101), and then determines whether or not the visual axis detection is started, specifically, the switch S.
It is detected whether W3 is pressed (step S10).
2).

When the line-of-sight detection is started, the flags and constants to be used are initialized. That is, "0" is stored in FLAG1, "1" is stored in i, and "0" is stored in N (step S103). Subsequently, the output signal of the line-of-sight detection sensor 15 is A / D converted (step S104),
The digital data is stored in the RAM in the CPU 18 (step S105).

Subsequently, the timer counter 19 built in the CPU 18 is reset and the timer counter is started at the same time (step S106). Then, the coordinates (x, y) in the line-of-sight direction are calculated according to the above-described principle, and x is stored in the memory Mepy.
In (1), y is stored in the memory Mepy (1) (steps S107 and S108).

Then, it is determined whether FLAG1 is "0" (step S109). This step S10
9, when FLAG1 is “0”, the memory Mepx (1), in which the line-of-sight direction data is stored,
The contents of Mepy (1) are stored in the memory Mepx (0), Mep.
Transfer to y (0) (step S119), store "1" in FLAG1, and proceed to the next step S120 (step S115).

On the other hand, in step S109, F
When LAG1 is “1”, the calculated line-of-sight direction data (Mepx (1), Mepy (1)) is calculated as the previously calculated line-of-sight direction data (Mepx (0), Mepy).
(0)) and it is determined whether or not there is a change of a predetermined amount or more (step S110). That is, with α as a constant, it is determined whether or not (Mepx (0) −α) ≦ (Mepx (1)) ≦ (Mepx (0) + α) (5).

Then, when the relation of the above equation (5) is established, it is recognized that the line-of-sight direction in the left-right direction (hereinafter, referred to as x direction) has not changed, and similarly, the vertical direction (hereinafter, referred to as y direction). The change in the line-of-sight direction of (YES) is determined. Then, as in the above formula (5), when (Mepy (0) −α) ≦ (Mepy (1)) ≦ (Mepy (0) + α) (6), the line-of-sight direction in the y direction also changes. It is recognized that it is not (step S116).

In this way, when it is recognized that the line-of-sight direction has not changed in either the x-direction or the y-direction, the content TIME of the timer counter is determined (step S117), and if the TIME is longer than the predetermined time t1, the CPU 6 is interrupted. The signal INT1 is transmitted (step S118). And
When the CPU 6 receives the interrupt signal INT1 from the CPU 18, the CPU 6 temporarily suspends the operation up to that point and branches to the interrupt routine INT1.

As shown in FIG. 10, when the interrupt routine "INT1" is entered (step S301), the interrupt by the interrupt signal INT1 is prohibited (step S302). This is because the interrupt stuff may overflow if the interrupt acceptance state is left. Next, line-of-sight direction data (Mepx,
Receives Mepy) and stores it in memory (step S
303).

Then, after the interruption prohibition of INT1 is released (step S304) and the address of the interruption staff is initialized (step S305), the interrupt ruling "INT
The process returns from "1" to continue the operation of the main program (step S306).

Now, when returning to the main program, the CPU 18 then instructs the CPU 6 to obtain the sight line direction data (Mep).
x (1), Mepy (1)) is transmitted. That is, CP
U6 receives the line-of-sight direction data only when the line-of-sight direction data has not changed for a predetermined time t1 or more, and focuses on an object in the viewfinder field frame that substantially matches the line-of-sight direction (step S119).

On the other hand, in S110 and S116 described above,
When the line of sight in the x and y directions is changing, the CPU 6
The interrupt signal INT2 is transmitted to (step S11
1). When the CPU 6 receives the interrupt signal INT2 from the CPU 18, the CPU 6 branches to the interrupt routine "INT2".

As shown in FIG. 11, when the interrupt routine "INT2" is entered (step S401), first the IN
The interruption of T2 is prohibited (step S402). Then, after the lens driving is stopped (step S403), the interruption inhibition by the interruption signal INT2 is released (step S404). Then, after initializing the interrupt stack (step S405), the interrupt routine is returned to the main program. This prevents unnecessary lens driving (step S40).
6).

Now, when returning to the main program, the line-of-sight direction data (Mepx (1), Mepy (1)) is transferred to the memories Mepx (0), Mepy (0), respectively (step S112), and the timer 19 is set. When it is reset again, the timer is started at the same time (step S11).
3).

The FLAG1 is checked in step S109 because comparison with the previous data is required in steps S110 and S116, but there is no previous data at the start of the CPU 18. The above is the operation for determining the AF visual field area for driving the lens.

Here, the eyeball is constantly moving slightly, and even if the user is looking at a certain direction, it may be unintentional and instantaneous, or the line-of-sight direction may change greatly. If the visual field frame is displayed in accordance with the movement of the eyeball, the display flickers so that it is difficult to see.

Therefore, after step S120, the time-average moving average (low-pass filter) in the line-of-sight direction is taken to smoothly and smoothly display the field frame. That is, the program after step S120 is a program for determining the visual field coordinates for displaying the visual field frame of the AF visual field area.

In step S120, the content of the constant counter N is first incremented. This N is a counter for detecting how many times the line-of-sight direction data has been updated since the line-of-sight direction detection was started. That is, when the moving average calculation is performed, a correct result cannot be obtained until the number of data (5 in this embodiment) necessary for performing the moving average calculation is prepared. At this time, the line-of-sight direction data for moving average calculation is updated. That is, the Mepx is stored in the memory Mepx (i).
The contents of (i-1) are stored in Mepy (i) as Mepy (i-
The contents of 1) are transferred (i = 1 to 5) (step S12).
1 to S123). Then, if the content of the counter N is not "5", the process returns to step S107, and if the content (N) of N is 5, the moving average is calculated.

[0048]

[Equation 3]

Is calculated, and the memories Mdspx and Mdsp
Store in dspy (steps S124, S12)
5). Since Mdspx and Mdspy are the coordinates of the visual field frame indicating the line-of-sight direction, the line-of-sight direction display position is updated using these (step S126). Then, CPU
It is determined whether or not the flag signal FLAG2 connected to 6 is "1". When the FLAG2 is normally released with "0", "1" is transmitted from the CPU 6 (step S
127).

If FLAG2 is "1" in step S127, it is subsequently determined whether FLA3 is "1" (step S128). This FLAG3 is CPU6
It is normally “0” when connected to the
U6 sets FLAG3 to "0". If FLAG3 is "1" in step S128, the process returns to step S100 (step S129). Next, FIG. 9 is a flowchart showing the operation of the CPU 6.

When the operation is started (step S200),
It is determined whether or not the start switch SW1 is turned on (step S201). And the start switch S
If W1 is pressed, the line-of-sight direction data memory Mep
Initialize x and Mepy (line-of-sight direction data in the x and y directions, respectively).

Here, the sight line direction data (γ, 7) corresponding to the visual field frame at the center of the screen shown in FIG. 2A is stored in the memories Mepx and Mepy. Therefore, when the line-of-sight direction data is not transmitted from the CPU 18, the object in the visual field frame at the center position of the screen is focused (step S2).
02).

Then, the output signal of the area image sensor 3 is A / D converted (step S203). Then, the sensor output signal in the visual field region determined by Mepx and Mepy is selected (step S204), and the average brightness BV of the sensor output signal is calculated (step S205). Further, the film sensitivity S input by the information input unit 14
Apex calculation (BV + SV = AV + TV) is performed using V, aperture value AV, and shutter speed TV (step S206).

Then, the shutter speed TV and the aperture value AV obtained by the apex operation are displayed on the liquid crystal display 12 (step S207). Further, based on the above-described principle, the sensor output signal of the visual field determined by Mepx and Mepy is used to calculate the defocus amount with respect to the object existing in the visual field, that is, the focus position shift amount from the focus matching position ( Step S208).

Then, the lens drive amount is calculated (step S209), and a signal is sent to the motor 9 to drive the lens by a predetermined amount (step S210). Then, when the lens driving is completed, the state of the release switch SW2 is subsequently checked to determine whether or not the release is performed. If the release switch SW2 is open, it is determined that the release is not made, the process returns to step S203, and the above program is repeated.

If the release switch SW2 is closed in step S212, "1" is output to FLAG2 connected to the CPU 18 and "0" is output to FLAG3 (step S213). Then, the exposure control is performed (step S214), and when the exposure control ends (step S215), the FLAG3 connected to the CPU 18 is connected.
"1" to FLAG2 and "0" to FLAG2 (step S
216). Thus, the process returns to step S203, and the same operation is repeated.

As described above in detail, in the focus detecting apparatus for a camera of the present invention, in the focus detecting apparatus for focusing in the line-of-sight direction substantially matching the line-of-sight direction in the viewfinder field, the field-of-view frame substantially matching the line-of-sight direction is set. , It is possible to stably display in the viewfinder field frame without being affected by the slight movement of the line of sight.

Further, the lens drive for focusing on the object in the visual field frame which substantially coincides with the line-of-sight direction can be smoothly performed without being influenced by the slight movement of the line-of-sight or a large instantaneous change.

[0059]

According to the present invention, by efficiently performing the finder display showing the line of sight of the photographer, driving the lens, etc., the power consumption is reduced and the discomfort given to the observer is eliminated, and further, it is desired. It is possible to provide a focus detection device for a camera that quickly and appropriately focuses an object to be captured.

[Brief description of drawings]

FIG. 1 is a block configuration diagram schematically showing a configuration of an AF camera to which a focus detection device of the present invention is applied.

2A and 2B are diagrams showing an example of a finder display.

FIG. 3 is an optical layout diagram showing in detail an optical system of the focus detection device according to the embodiment.

FIG. 4 shows an example of output waveforms of a corneal reflection image of an eye, a pupil, and an iris.

5A to 5C are diagrams for explaining the principle of focus detection.

FIG. 6 is a diagram showing a positional relationship in which a first Purkinje image is formed.

FIG. 7 is a flowchart showing the operation of the CPU 18.

FIG. 8 is a flowchart showing the operation of the CPU 18.

FIG. 9 is a flowchart showing the operation of the CPU 6.

FIG. 10 is a flowchart showing the operation of an interrupt routine “INT1”.

FIG. 11 is a flowchart showing an operation of an interrupt routine “INT2”.

[Explanation of symbols]

1 ... Photographing lens, 2 ... Focus detection optical system, 3 ... Area image sensor, 4 ... Sensor driver, 5 ... A / D converter, 6 ... CPU, 7 ... Lens ROM, 8 ... Lens drive circuit, 9 ... Motor, 10 ... Photointerpler, 11 ... Liquid crystal driver, 12 ... Liquid crystal display section, 13 ... Exposure control circuit, 1
4 ... Information input part, 15 ... Sensor for detecting gaze direction, 16 ...
Sensor driver, 17 ... A / D converter, 18 ... CP
U, 19 ... Timer, 20 ... Liquid crystal driver, 21 ... Liquid crystal display section.

[Procedure amendment]

[Submission date] March 23, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0030

[Correction method] Change

[Correction content]

[0030]

[Equation 2] Therefore, the vertical rotation angle θ _y can be obtained in exactly the same manner. If these θ _x and θ _y are known, the center coordinates (x, y) of the field frame that coincides with the line-of-sight direction in the finder field can be obtained from the finder optical system α magnification. Less than,
The operation of the focus detection apparatus according to this embodiment will be described with reference to the flowcharts of FIGS. 7 and 8 are flowcharts showing the operation of the CPU 18.

Claims (2)

[Claims] 1. A first output means for generating a first output signal according to a line-of-sight direction of a photographer in a viewfinder frame of a camera, and an output signal of the first output means is substantially constant for a predetermined time or longer. At this time, the lens driving means for driving the lens for focusing in the line-of-sight direction corresponding to the output signal, the filter means for applying a temporal low-pass filter to the output signal of the first output means, and the filter means A focus detecting device for a camera, comprising: a display unit that displays a field frame that substantially matches the line-of-sight direction corresponding to the output signal in the finder field frame. 2. A first output means for generating a first output signal according to a photographer's line-of-sight direction within a viewfinder frame of a camera; and an output signal of the first output means for a predetermined time or more. At a constant time, the lens drive means for driving the lens to focus in the line-of-sight direction according to the output signal, and the output signal of the first output means changed by a predetermined amount or more while the lens was being driven by the lens drive means. A focus detecting device for a camera, comprising: a control unit that sometimes stops the driving.