JP2000171685A - Focus detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily make a principal object in focus by reducing an effect exerted on a focus detecting action by light such as street light being harmful to the focus detecting action when a night scene is photographed. SOLUTION: This focus detector is constituted so that the charge storing time of a charge storage type photoelectric sensor in a focus detection part 12 is controlled by an integral control part 14. Besides, it is judged by a night scene harmful light judgement part 15 based on the output of the detection part 12 whether a noise light source exists in a prescribed area or not. When it is judged by the judgement part 15 that the noise light source exists in the prescribed area, the control part 14 is controlled so that the charge storing time more prolonged than the charge storing time is set or the re-storing of the charge storage type photoelectric sensor is executed while actuating an auxiliary light part 16 which can be actuated in the charge storing time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a focus detection device, and more particularly, to an automatic focus camera that automatically performs focus detection.

[0002]

2. Description of the Related Art Conventionally, many cameras having a night view mode have been developed. It is well known that even if the mode is not a night view shooting mode, a beautiful photograph can be taken by fixing the camera to a tripod and using long exposure.

Further, even a dark subject such as a night scene can be detected by a recent autofocus camera.

FIG. 15A is a view showing a scene in a viewfinder to be photographed. In this scene, a person 2 is standing in the foreground.
Is going to be taken as the main subject. The neon 4 of the background building 3 is on the left side of the person, and the background streetlight 6 is on the right side of the person 2. The AF target (distance measuring frame) 7 is composed of the person 2, the neon lights 4, and the streetlights 6.
And the surrounding area is a night view, so it is dark.

In general, when a night view is to be photographed, the scene shown in FIG. 15A is a common scene. That is, there is often a light source in the ranging frame 7, and the light source is often the light of a window of a building in the background or a streetlight, and it is rare that the inside of the ranging frame 7 is completely dark. is there. The same can be said for a case where there is no main subject in the foreground. In other words, it can be said that the light source in night view shooting often becomes a point light source unlike the daytime sun.

FIG. 15B shows sensor data obtained by imaging the scene shown in FIG. 15A with an AF sensor. The AF detection method is a known passive phase difference detection method, and indicates the outputs of the left and right sensor arrays, respectively. In FIG. 15B, the horizontal axis indicates the arrangement order of all pixels (64 elements), and the vertical axis indicates the sensor output. In the figure, the outputs of adjacent pixels are connected.

As can be seen from FIG. 15B, the image of a street lamp is a point light source for the AF sensor and is very bright, so that the image becomes a thin and steep image. Darker and the output is smaller. That is, since the difference in brightness is large, an output in which the image at the center of the dark portion is crushed is obtained. For example, it is known that the sensor output under backlight also becomes such.

When focus calculation is performed on the basis of such sensor output, a photograph may be out of focus on both the background and the person. This is due to the following two problems that the passive phase difference detection method originally has in principle.

(I) A backlit subject is hard to focus on the center image because the center image is destroyed. (Ii) If focus calculation is performed based on a steep image (an image like a point light source in which an image appears only in a few pixels), the calculation accuracy is reduced.

[0010] To solve the above problems (i) and (ii), the following prior arts are known.

For example, Japanese Patent Publication No. 6-7219 discloses that
There is disclosed a technology in which an AF sensor is arranged at a position slightly offset from an image forming plane of an AF optical system so as to exert an optical low-pass effect so that it is difficult to generate a sharp sensor output.

JP-A-5-264887 discloses a technique in which when a backlight condition is detected, the integration time of the AF sensor is extended so that an image of a dark portion is also output. That is, as shown in FIG. 15C, the image of the surrounding streetlight is saturated, but the image of the central person is clearly output to focus on the person. The integration time in the case of FIG. 15C is several times longer than that in the case of FIG.

Further, Japanese Patent Application Laid-Open No. Hei 7-199039 discloses a technique for emitting AF auxiliary light when a night scene mode for photographing a night scene is set.
That is, this is a technique in which an auxiliary light is applied to a person in front of the person to clearly output the image of the person and focus on the person.

[0014]

However, the above-mentioned prior art has the following problems.

The technique disclosed in Japanese Patent Publication No. 6-7219 is effective for a thin line subject, but is not effective for a point light source such as a street lamp as shown in FIG. ing. Conversely, it can be said that a point light source such as a street lamp becomes a very steep image to that extent. That is, there is a need for a technique for reducing the influence of a point light source on focus detection.

In JP-A-5-264887, since backlight under sunlight is to be detected,
There is a problem that the sensor output as shown in FIG. 15B cannot be determined to be backlight. That is, only when the output on both sides is larger than that at the center, it can be determined that the subject is backlit.

Further, in the above-mentioned Japanese Patent Application Laid-Open No. 7-199039, in the night scene mode, the auxiliary light of AF is always emitted, so that not only energy loss but also unnecessary scenes can be obtained.
That is, there is a problem that the night view mode is used under sunlight, or the auxiliary light is emitted even in a night view without harmful light for AF such as a street lamp.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has an object to reduce the influence of harmful light on the focus detection of a focus on a streetlight or the like in night view photographing and to facilitate focusing on a main subject. It is an object of the present invention to provide a focus detection device which can be used.

[0019]

According to the present invention, there is provided a focus detecting apparatus for detecting a focus adjustment state of a photographing lens with respect to an object in a predetermined area on a screen using a charge storage type photoelectric sensor. Control means for controlling the charge storage time of the photoelectric sensor; and determination means for determining whether or not a noise light source exists in the predetermined area based on the output of the charge storage photoelectric sensor. The control means sets a charge accumulation time longer than the charge accumulation time when the determination means determines that the noise light source exists in the predetermined area, or sets the charge accumulation time during the charge accumulation time. Re-accumulation of the charge accumulation type photoelectric sensor is performed while operating the operable auxiliary light.

According to the present invention, there is provided a focus detecting device for detecting a focus adjustment state of a photographing lens with respect to an object in a predetermined area in a screen by using a charge storage type photoelectric sensor. The charge accumulation time of the photoelectric sensor is controlled. Further, based on an output of the charge storage type photoelectric sensor, a determination unit determines whether or not a noise light source exists in the predetermined region. The control means sets a charge accumulation time longer than the charge accumulation time when the determination means determines that the noise light source is present in the predetermined area, or Control is performed so that the charge accumulation type photoelectric sensor is re-accumulated while operating the auxiliary light that can be operated during the accumulation time.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the concept of an automatic focus detection device according to an embodiment of the present invention.

In FIG. 1, a focus adjustment control unit 11 which controls the automatic focus adjustment includes a focus detection unit 12, a focus calculation unit 13, an integration control unit 14, and a night scene scene harmful light determination unit 15 , An auxiliary light unit 16 and a lens driving unit 17 are connected.

The focus detecting section 12 is constituted by an AF sensor which outputs a signal for focus detection. The focus calculation unit 13 is for calculating the defocus amount of the photographing lens based on the output of the focus detection unit 12. Then, the integration control unit 14 controls the focus detection unit 1.
2 controls the charge accumulation (integration) operation of the AF sensor to give an appropriate integration amount.

The night scene harmful light determining section 15 is a means for determining whether or not the focus detection signal contains harmful light for AF such as a street lamp. Auxiliary light section 16
Is for irradiating the subject with light to enable focus detection when the focus cannot be detected due to the low brightness of the subject. Further, the lens drive unit 17 is provided with the focus calculation unit 1.
The photographing lens is driven to the in-focus position based on the output of (3).

FIG. 2 is a block diagram showing the overall configuration of a camera to which the focus detection device of the present invention is applied.

First, the mechanical structure and the optical structure of the camera will be described.

In FIG. 2, a light beam from a subject (not shown) is divided into first lens group 21, second lens group 22, third lens group 23, fourth lens group 24, and fifth lens group 25. Then, the light passes through a five-group photographing lens 27 composed of

The first group lens 21 and the second group lens 2
In 2, focusing is performed. Then, at the same time as the third group lens 23 and the fourth group lens 24 are moved, the first group lens 21 and the second group lens 22 are driven by a cam structure (not shown) to prevent a focus movement during zooming. ing.

The main mirror 30 is a half mirror, and 70% of the amount of incident light is reflected toward the finder optical system 31. The finder optical system 31 includes a screen 32, a condenser lens 33, a prism 34, a mold roof mirror 35, and an eyepiece 36, and is observed by a photographer.

On the other hand, the remaining 30% of the incident light amount is transmitted through the main mirror 30 and reflected by the sub-mirror 39, and then the A
The light is guided to the F optical system 40. The AF optical system 40 includes:
The AF sensor 62 includes a field stop 41, an infrared cut filter 42, a condenser lens 43, a mirror 44, a re-imaging stop 45, and a re-imaging lens 46.
A light beam for focus detection is guided to the camera.

The main mirror 30 and the sub-mirror 39
Is retracted to the position shown by the broken line in the figure at the time of film exposure. The luminous flux of the subject that has passed through the photographing lens 27 is transmitted to a shutter 50 located behind the main mirror 30.
Is exposed to the film 51 while the camera is open.

Next, the electrical configuration of the camera will be described.

In FIG. 2, a camera control unit 55 as a camera control device includes a CPU 56 as a central processing unit.
And an interface IC 57 for controlling a series of operations of the camera.

The camera controller 55 includes an exposure controller 6
0, a film drive unit 61, an AF sensor 62, an aperture drive unit 63, a zoom control unit 64, an AF lens control unit 65, a photometry unit 66, a flash control unit 67, and a switch group 68 are connected. ing.

The exposure control section 66 includes a main mirror 30
Up and down and driving of the shutter 50 to control the exposure of the film 51. Also,
The film drive unit 61 controls the winding and rewinding of the film 51.

The AF sensor 62 includes photodiode arrays 62L and 62R, which are photoelectric conversion element arrays. Then, these photodiode arrays 62
The outputs of the L and 62R elements are output to the camera control unit 55 to perform focus detection.

The aperture driving section 63 drives the aperture 26 in the taking lens 27 to an appropriate aperture value. Further, the zoom control unit 64 is configured to drive the zoom lens group of the photographing lens 27 by the zoom motor 71 and control the zoom position by the encoder 72.

The AF lens controller 18 drives the focus lens group by the AF motor 73, and controls the position of the focus lens group by the encoder 74.

The photometric unit 66 is a sensor composed of a photodiode that generates an output according to the brightness of the subject (not shown), and is installed in the finder optical system 31, for example. In addition, the strobe control unit 67 controls a strobe that emits flash light to the subject, and according to the present invention, A
Since a strobe light is used for the auxiliary light of F, it also serves as an auxiliary light control unit.

The switch group 68 is composed of all switches on the camera pressed by the photographer, and includes a release button (not shown) and a photographing mode switch for setting a night scene mode. When the night view mode switch is pressed, the camera enters a mode in which an exposure operation suitable for night view shooting is performed.

FIG. 3 is a diagram showing the internal block configuration of the AF sensor 62.

In the figure, an AF sensor 62 includes photodiode arrays 62L and 62R and a pixel amplifier circuit (EA).
C) 77, a shift register (SR) 78, and a sensor control circuit (SCC) 79.

The photodiode arrays 62L and 62L
In 2R, electric charges are generated according to the amount of light incident on each photodiode. And the generated charge is
The signals are output to the pixel amplifier circuit 77 independently.

In the pixel amplifying circuit 77, the charges generated by the photodiodes of the photodiode arrays 62L and 62R are independently amplified, and a voltage signal for the generated charges is generated. In the pixel amplifier circuit 77,
A monitor output is generated according to the maximum value of the charges generated by each photodiode, that is, the output of the pixel amplifier circuit corresponding to the photodiode with the largest incident light amount, and is output to the monitor output terminal MDATA.

In the sensor control circuit 79, the CPU
Signals from 56 (CEN, RES, END, CLK)
, The operation inside the AFIC (not shown) is controlled.

Further, in the shift register 78, the CPU 5
In response to the clock signal CLK from 6, the outputs of the pixel amplifier circuits 77 corresponding to the respective photodiodes of the photodiode arrays 62L and 62R are sequentially output to the sensor data output terminal SDATA.

Next, the operation of the CPU 56 and the AF sensor 62 will be described with reference to the timing chart of FIG.

First, the reset signal R
When the ES is received, the sensor control circuit 79 initializes each block inside the AF sensor 62. At the same time, the accumulation operation by the photodiode arrays 62L and 62R and the pixel amplification circuit 77 is started.

During the accumulation operation, the pixel amplification circuit 77 outputs
A monitor signal corresponding to the level of charge accumulation is a monitor output MD.
Output to ATA. In the CPU 56, the monitor output MDATA is monitored as needed by an internal A / D converter. When the monitor output MDATA reaches a level at which an appropriate charge accumulation amount is reached, an accumulation end signal END is output to the AF sensor 62, and the integration operation is performed. Will be terminated.

Next, the read clock CLK is output to the AF sensor 62 by the CPU 56. In the shift register 78, the photodiode array 62L
And the output voltage of the pixel amplification circuit 77 corresponding to the accumulated charge of the photodiode of 62R is the sensor data output SDA
Output to TA sequentially. In the CPU 56, the sensor data output SDATA is sequentially A / D converted by a built-in A / D converter, and stored in the internal RAM.

As will be described later, the AF auxiliary light of the present invention uses a strobe light. When the focus cannot be detected due to the low brightness of the subject, as shown in FIG. 4, the strobe light is emitted in a pulsed manner during the integration operation to obtain a proper integration amount.

FIG. 5 is a diagram showing a detailed configuration of the flash control section 67 which also serves as an auxiliary light.

In FIG. 5, a DC / DC converter 81 for boosting the power supply voltage to a voltage at which a strobe can emit light is connected in parallel to the power supply E. And this D
The output of the C / DC converter 81 is connected to a main capacitor voltage measuring circuit 82 for measuring the voltage charged in the main capacitor MC.

The output of the DC / DC converter 81 is connected to a trigger circuit 83 for applying a trigger for light emission to a Xe (xenon) tube 86, and further stores light emission energy via a diode D1. The main capacitor MC is also connected.

The power supply E includes a Xe tube 86 that emits light by consuming energy of a main capacitor MC connected to the cathode of the diode D1 and a light emission amount control for controlling the light emission amount of the Xe tube 86. Circuits 84 are connected in series. Further, the light emission amount control circuit 84
Is connected to a power supply control circuit 85 for controlling the supply of the power E.

The control of the DC / DC converter 81, the main capacitor voltage measuring circuit 82, the trigger circuit 83, and the light emission amount control circuit 85 is performed by the CPU 56 via the interface IC 57.

Next, referring to the flowchart of FIG.
The operation of the entire camera according to the first embodiment will be described.

FIG. 6 is a flowchart of a main routine showing the operation of the entire camera according to the first embodiment of the present invention.

First, when a main switch (not shown) is turned on, the power is reset by the CPU 56 to start the operation, and in step S1, I / O port initialization, RAM initialization and the like are performed. Next, step S2
It is determined whether or not the first release switch (1RSW) is turned on.

A release switch (not shown) of the camera according to the present invention comprises a general two-stage switch.
The first release switch is turned on in the first stroke in the half-pressed state, and the camera performs operations such as AF and lens driving. Then, the second release switch (2R) is pressed in the second stroke when the release switch is fully pressed.
SW) is turned on to reach exposure.

If it is determined in step S2 that the first release switch is off, the process proceeds to step S10. On the other hand, if it is on, the process proceeds to step S3,
6 is operated to measure the brightness of the subject, and the aperture value and the shutter speed value for obtaining the proper exposure are calculated.

Then, in step S4, a subroutine "AF" is executed to detect the focus of the subject. Based on this focus detection, the focusing lens is driven to the in-focus position to focus on the subject. The details will be described later.

Subsequently, in step S5, this AF
As a result of the operation, it is determined whether or not focusing has been achieved. As will be described later, when AF is not possible due to low contrast or the like (determined by an undetectable flag), it is determined that focus is not achieved. Here, if the camera is not in focus, the process proceeds to step S9, and the process cannot shift to the exposure operation until the camera is in focus. On the other hand, if the camera is in focus, it is determined in step S6 whether the second release switch is on.

In step S6, if the second release switch has been turned off, the process returns to step S2. On the other hand, if the switch is turned on, the process proceeds to step S7, and based on the result calculated in step S3, the aperture 26, the main mirror 30, and the shutter 50 are controlled to perform an exposure operation.

When this exposure operation is completed, step S8
Then, the photographed film 51 is wound and fed to the position of the next frame, and a series of photographing operations ends. Then, in step S9, a not-shown display device L
After the CD and LED display operations are controlled, the process returns to step S2.

In step S10, the state of another switch is detected in response to the operation of any switch other than the first release switch and the second release switch. If none of the switches is turned on, the process proceeds to step S9. On the other hand, when there is a switch that is turned on, the process proceeds to step S11, and after performing a process corresponding to the switch, the process proceeds to step S9.

FIG. 7 is a flowchart for explaining the operation of the subroutine "AF" in step S4 in the flowchart of FIG.

First, in step S21, integration of the AF sensor 62 is started in accordance with the timing chart described in FIG. 4, and in step S22, counting of the integration time is also started.

Then, in step S23, MDATA
Is subjected to A / D conversion. Since MDATA indicates the integral amount, it is determined in step S24 whether MDATA is at an appropriate value. Here, if it has reached the appropriate value, the process proceeds to step S26, but if not, it is determined in step S25 whether or not the integration time has reached the limit value (for example, 200 ms). In this step S25, if the time has not reached the limit time, the process returns to the step S23.
Move to 3.

If it is determined in step S24 that MDATA has reached the appropriate value, the flow shifts to step S26 to store the variable ST1 of the integration time. Next, step S27
Then, the sensor data of all pixels is read into the RAM of the CPU 56.

Next, in step S28, it is determined whether or not a point light source serving as harmful light is included. The details will be described later. In subsequent step S29, when it is determined that no harmful light is included, the process proceeds to step S34, but when it is included, in steps S30 and S31, as in steps S21 and S22 described above. Starts integration. The integration here is based on the previous step S
Unlike the integration of S21 and S22, the integration time
Integration is several times longer than one.

Then, in step S32, it is determined whether or not the integration time has reached N times ST1. Here, step S is performed until the integration time reaches N times ST1.
While the process waits while the process 32 is being executed, the process proceeds to step S33 if the process has been reached. Incidentally, N is suitably about 3 to 7.

Next, as in step S27, the sensor data of all pixels is read into the RAM of the CPU 56 in step S33, and illuminance correction is performed in step S34. This illuminance correction is a known technique for correcting variations in sensor sensitivity and a decrease in peripheral light amount of the AF optical system.

Next, in step S35, a correlation operation of the central block is performed. This central block is shown in FIG.
FIG. 3B shows a block between the central portions of the left and right sensors shown in FIG. That is, the correlation operation in the central block is performed. Details of this will be described later.

Then, in step S36, as a result of the correlation operation, it is determined whether or not the focus cannot be detected. If the detection is not possible, the process proceeds to step S37, where the correlation calculation of the right block is performed. This right block is
FIG. 16B illustrates a block between right portions of left and right sensors illustrated in FIG. That is, the correlation operation in the right block is performed.

In the following step S38, it is determined whether or not the focus cannot be detected as a result of the correlation operation. If the detection is not possible, the process proceeds to step S39, where the correlation calculation of the left block is performed. The left block represents a block between the left parts of the left and right sensors shown in FIG. 15B. That is, the correlation operation in the left block is performed.

In step S40, it is determined whether or not the focus cannot be detected as a result of the correlation operation. here,
If it cannot be detected, it returns because all blocks cannot be detected.

On the other hand, steps S36, S38, S4
If detection is possible at any of 0, the process proceeds to step S41, where the defocus amount of the photographing lens 27 is calculated, and the aberration amount of the photographing lens 27 is corrected in the subsequent step S42. The aberration correction corrects a difference in the detected defocus amount due to a difference in the focal length of the photographing lens 27.

Next, in step S43, it is determined whether or not the taking lens 27 is already in focus. This is to determine whether or not the detected defocus amount is within a predetermined allowable value. Then, if the camera is already in focus, there is no need to drive the lens.
If out of focus, the process moves to step S44 to calculate the lens drive amount until focusing. Next, when the taking lens 27 is driven to the in-focus position in step S45, the process returns.

The above steps S41, S42, S4
4. The details of S45 are well-known techniques and are not directly related to the gist of the present invention, and thus description thereof is omitted.

As described above, even when harmful light is detected, by extending the integration time and performing reintegration, the person in front can be compared with the case of FIG. 15B in which the integration time is not extended. The image of the object other than the point light source included in FIG.
As shown in (c), the image is clearly output, and the person can be focused. That is, in the central block correlation calculation in step S35, a human image can be detected.

Next, referring to the flowchart of FIG.
The operation of the subroutine "center block correlation calculation" executed in step S35 of the flowchart of FIG. 7 will be described.

Here, the sensor data read in step S33 of the flowchart of FIG. 7 is expressed as a subject image signal L (I) of the left sensor and a subject image signal R (I) of the right sensor.

First, in steps S51 and S52, "5", "37", "5", and "8" are assigned to variables SL, SR, Fmin, and J, respectively, as initial values. The variable SL is a variable that stores the head number of the small block element row whose correlation is detected from the subject image signal L (I), and similarly, SR is the correlation detection from the subject image signal R (I). This is a variable for storing the head number of the small block element sequence to be executed. Fmin is a variable indicating the minimum correlation value. Further, J is a variable for counting the number of times small blocks have been shifted in the subject image signal L (I).

Then, in step S53, the correlation output F
(S) is calculated from the following equation (1).

[0087]

(Equation 1)

In this case, the number of elements in the small block is 27. The number of elements in the small block is determined by the size of the distance measurement frame displayed on the finder and the magnification of the detection optical system.

Subsequently, in step S54, the minimum value of the correlation output F (s) is detected. That is, F (s)
And Fmin are compared. Here, F (s) is Fmi
If n or more, the process moves to step S56, and F (s) becomes F
If it is smaller than min, the process moves to step S55.
In this step S55, F (s) is substituted for Fmin, and SL and SR at that time are stored as SLM and SRM, respectively.

In step S56, the variables SR and J are decremented, and in step S57, the correlation calculation is repeated until J = 0. That is, the small block position in the image L is fixed, and the small block position in the image R is 1
The correlation is obtained while shifting the elements one by one.

When J = 0 at step S57, 4 and 3 are added to SL and SR at step S58, respectively, and the correlation calculation is repeated at step S59 until SL = 29. That is, the correlation calculation is repeated while the number of elements of the small block in the image L is shifted by 4 elements.

As described above, the correlation calculation is performed efficiently,
The minimum value of the correlation output can be detected. The position of the small block indicating the minimum value of the correlation output indicates the positional relationship of the image signal having the highest correlation.

Then, in step S60, since the correlation is determined for the detected small block image signal having the highest correlation, the correlation output FM represented by the following equations (2) and (3) is obtained. FP is calculated.

[0094]

(Equation 2)

That is, the correlation output when the object image R is shifted by ± 1 element from the small block position showing the minimum correlation output is calculated. At this time, FM, F
The relationship between min and FP is as shown in FIGS. 9A and 9B. 9A and 9B, the horizontal axis represents the position of the photoelectric conversion element (element number from the left end), and the vertical axis represents the correlation output. If the correlation is high, the correlation output F
(S) becomes S ₀ = 0 at the point S ₀ . On the other hand, when the correlation is low, S ₀ = 0 is not established.

Assuming that the number of photoelectric conversion elements is 64 on one side by the above correlation operation, about 5 photoelectric conversion elements at both ends on the left and right sides are obtained.
This means that the correlation operation has been performed over almost the entire area excluding the elements.

Next, in step S61, correlation indexes SK and FS represented by the following equations are obtained to determine the correlation. When FM ≧ FP SK = (FP + Fmin) / (FM−Fmin) (4) FS = FM−Fmin (5) When FM <FP SK = (FM + Fmin) / (FP−Fmin) (6) FS = FP−Fmin (7) FIGS. 9A and 9B show only the case where FM ≧ FP.

The correlation index SK becomes SK = 1 when the correlation is high, and the higher the value, the lower the correlation. Further, the correlation index FS corresponds to the contrast of the small block image signal having the highest correlation, so that a larger value indicates a higher contrast.

Therefore, in steps S62 and S63, the values of the correlation indexes SK and FS are compared with predetermined values to determine whether or not the detected image shift amount is reliable. be able to. The above step S62,
If it is determined in any of S63 that the reliability is low, the flow shifts to step S64 to set an undetectable flag, and returns.

On the other hand, if it is determined that the reliability is high in any of steps S62 and S63, step S6
The flow returns to 5 to return after the undetectable flag is cleared. This undetectable flag is determined in step S36 of the above-described flowchart of FIG.

FIGS. 10 and 11 are conceptual diagrams of the harmful light determination in step S28 in the flowchart of FIG. FIG.
The sensor data shown in FIG. 15 is the same as that in FIG. 15B, and the sensor data shown in FIG.
It is the same as that of

The sensor data shown in FIG. 10 shows an example in which the influence of the harmful light on the focus detection is large.
As described above, the streetlight image is a point light source for the AF sensor and is very bright, so that the image becomes thin and steep. However, the image of the person is darker than the background streetlight and neon, and the output is small. That is, since the difference in brightness is large, the output of the image in the center of the dark portion is crushed, and the width of A and B in FIG. 10 is large, but the width of C is small, and the width of C is also large in the pixel pitch. It is about 3 pixels, though. Outputs a and b are small and c is very large. Such sensor data is detected, and it is determined that harmful light is present.

FIG. 11 shows sensor data when the integration time described in the first embodiment is extended. The width of A ', B' and C 'in FIG.
Are slightly larger than the width of A, B and C, but there is not much difference.
However, the outputs a 'and b' are much larger than a and b in FIG.

As described above, in the case of FIG. 11, the image of the street lamp is also steep and may cause harmful light. However, since the image of the person and the image of neon are clearly output, the influence of the harmful light on the focus detection is small. In such a case, it can be determined that there is no harmful light.

Next, the operation of the subroutine "harmful light judgment" in step S28 in FIG. 7 will be described with reference to the flowchart in FIG.

First, in step S71, a value at which the maximum output is obtained from all the pixels and the pixel are searched, and the value is set to Max. This corresponds to c in FIG. Next, in step S72, it is determined whether or not the above-mentioned Max is greater than a first threshold value.

If Max is not larger than the first threshold value, the flow shifts to step S81 to clear the harmful light flag and returns. That is, Max
If is not large to some extent, it is determined that it cannot be harmful light.

On the other hand, if Max is larger than the first threshold value, the flow shifts to step S73 to obtain the output of the pixel two pixels ahead of the pixel giving the maximum output, and sets the output as Maxp. . Further, in step S74,
The output of a pixel two pixels before the pixel giving the maximum output is obtained, and the output is set to Maxm.

Next, in step S75, Max
It is determined whether -Maxp is greater than a second threshold value. Here, if Max-Maxp is not larger than the second threshold value, the process proceeds to step S81. If it is larger, whether Max-Maxm is larger than the second threshold value in subsequent step S76. It is determined whether or not. Here, if Max-Maxm is not larger than the second threshold value, step S8
Move to 1. That is, it is detected that the sensor data changes sharply in the range of ± 2 pixels, and if the sensor data does not change sharply, it is determined that harmful light is not possible.

On the other hand, the above steps S75 and S76
In the case where Max-Maxp is larger than the second threshold value and Max-Maxm is also larger than the second threshold value, the process shifts to step S77 and the five pixels of the maximum output pixel ± 2 pixels , And the maximum output value is searched, and that value is set to Max '. Step S7
At 8, the minimum output value is searched except for 5 pixels of the maximum output pixel ± 2 pixels, and the value is set to Min '. Ma above
The values of x 'and Min' are shown in FIG.

Then, in step S79, Ma
It is determined whether x'-Min 'is greater than a third threshold value. Here, if Max'-Min 'is larger than the third threshold value, the process proceeds to step S81. That is, this is the same as determining the contrast of the output of the remaining pixels except for the five pixels of the maximum output pixels ± 2 pixels, and when the contrast of the output of the remaining pixels is high (Max′−Min ′ is large). Has the sensor data shown in FIG. 11, and it is determined that the influence of the harmful light on the focus detection is small.

On the other hand, when the contrast of the output of the remaining pixels is low (Max'-Min 'is small in step S79), the sensor data is as shown in FIG. Is determined to have a large effect on the image, and the process returns to step S80 after the harmful light flag is set.

Next, a second embodiment of the present invention will be described.

The second embodiment differs from the first embodiment only in the subroutine "harmful light judgment".
Since other configurations and operations are the same, only the subroutine of "harmful light determination" will be described.

The subroutine “judgmentary light judgment” of the second embodiment shown in FIG. 13 is a simplified version of that of the first embodiment.

The characteristic of the sensor data as shown in FIG. 10 is that the integration time is short. This is because integral control is performed so that a very bright image such as a point light source is not saturated. Therefore, even when the surroundings are dark, such as a night scene, when an image including a point light source is integrated, the integration is completed in about the same integration time as in a daytime scene.

Another feature is that the average value of all the pixels is relatively small because the outputs other than the point light source are small. In other words, there is an inconsistent feature that the average of the entire output is small even though the scene is a bright scene with a short integration time.

The second embodiment focuses on these features and simplifies harmful light determination.

FIG. 13 is a flowchart for explaining the operation of the subroutine "judgmentary light determination" in the second embodiment.

First, at step S91, the integration time ST1 stored at step S26 in the flowchart of FIG.
Is read. Then, in a step S92, it is determined whether or not the integration time is longer than a fourth threshold value.

If the integration time ST1 is longer than the fourth threshold value, the flow shifts to step S96.
After the harmful light flag is cleared, the routine returns. on the other hand,
If the integration time ST1 is shorter than the fourth threshold value in step S92, the process proceeds to step S93, and the average value of the outputs of all the pixels is obtained.

Next, in step S94, it is determined whether or not the average output is greater than a fifth threshold value. If the average output is greater than the fifth threshold value, the process proceeds to step S96. If the average output is smaller, the process proceeds to step S95, and the harmful light flag is set. Then, return.

With such a configuration, in the second embodiment, it is possible to detect the characteristic of the sensor data including the harmful light described above, which is simpler than that of the first embodiment. A subroutine "judging light judgment" can be executed.

In the above embodiment, when combined, more accurate judgment of harmful light is possible. That is, when the sensor data includes steep sensor data, and the contrast of the sensor data excluding the steep sensor data portion is low, the integration time is relatively short, and the average value of the entire output is relatively small, It may be determined that there is harmful light.

Next, a third embodiment of the present invention will be described.

In the third embodiment, only the subroutine "AF" is different from the first or second embodiment described above, and the other configuration and operation are the same.
Only the subroutine "F" will be described. In this case, the subroutine “judgment light determination” may be any of the flowcharts in FIGS. 12 and 13.

FIG. 14 is a flowchart for explaining the operation of the subroutine "AF" of the third embodiment.

The subroutine "A" of the third embodiment
F "is a step S31 in the flowchart of FIG.
Step S3 after the counting of the integration time is started
4 before the illuminance correction is executed.

Here, when harmful light is detected,
The auxiliary light unit 16 is controlled so that the auxiliary light is emitted and integrated again. In the present invention, a strobe is used as auxiliary light, and its configuration and time chart are as described with reference to FIGS.

That is, after the integration is started in step S111, the auxiliary light is emitted once in step S112. Then, in step S113, the value of MDATA is A / D converted.

Next, in step S114, it is determined whether or not the MDATA is at an appropriate value. Here, if MDATA has reached the appropriate value, step S11
Then, the process proceeds to step 6, where the sensor data is read.

However, if the MDATA has not reached the proper value, it is determined in the following step S115 whether or not the integration time has reached the limit value. Here, if the limit time has not been reached, the above step S
Returning to step 112, the auxiliary light is emitted. If it has reached, the process proceeds to step S116.

The processing operations of steps S101 to S111 and steps S117 to S128 are the same as steps S21 to S31 and steps S34 to S45 in the flowchart of FIG. .

As described above, even when the harmful light is detected, the auxiliary light is emitted and the reintegration is performed. As a result, as compared with the case shown in FIG. FIG. 1 shows an image of a subject other than a point light source including a person.
The output will be clearer as shown in 1,
Can focus on a person. That is, step S1
In the central block correlation operation of 18, a human image can be detected.

Although the embodiment of the present invention has been described above, it is needless to say that the present invention is not limited to the above-described embodiment, but can be modified without departing from the gist of the present invention. For example, the auxiliary light may be constituted by an LED or the like. Further, the above processing may be executed only when the night scene mode is selected, and may not be executed when any other mode is selected.

According to the above embodiment of the present invention,
The following configuration can be obtained.

(1) Focus detection means for outputting a focus detection signal according to the focus adjustment state of the taking lens, harmful light determination means for determining whether or not harmful light is included in the focus detection signal, When the harmful light is determined by the harmful light determination means to be included in the focus detection signal, control means is provided for controlling the focus detection means so as to remove the influence of the harmful light. Focus detection device.

(2) The focus detecting means includes an AF sensor composed of a photoelectric conversion element, and the control means determines that the harmful light determining means determines that harmful light is contained. The focus detection device according to the above (1), wherein control is performed to extend the accumulation time.

(3) Auxiliary light means for irradiating the subject with light is provided, and the control means controls the auxiliary light means to emit light when the harmful light determination means determines that the harmful light is contained. The focus detection device according to (1), wherein:

[0140]

As described above, according to the present invention, it is possible to reduce the influence of harmful light on focus detection for focus detection of a street lamp or the like in night view photography, and to facilitate focusing on a main subject. A focus detection device can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a concept of an automatic focus detection device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an overall configuration of a camera to which the focus detection device of the present invention is applied.

FIG. 3 is a diagram showing an internal block configuration of an AF sensor 62 of FIG. 2;

FIG. 4 is a flowchart illustrating operations of a CPU 56 and an AF sensor 62 in FIG.

FIG. 5 is a diagram showing a detailed configuration of a flash control unit 67 which also serves as an auxiliary light.

FIG. 6 is a flowchart of a main routine showing an operation of the entire camera according to the first embodiment of the present invention.

FIG. 7 is a flowchart illustrating an operation of a subroutine “AF” of step S4 in the flowchart of FIG. 6;

FIG. 8 is a flowchart illustrating an operation of a subroutine “center block correlation calculation” executed in step S35 of the flowchart of FIG. 7;

FIG. 9 is a diagram illustrating a relationship between a position of a photoelectric conversion element and a correlation output value.

FIG. 10 is a conceptual diagram of harmful light determination in step S28 of the flowchart in FIG. 7;

FIG. 11 is a conceptual diagram of harmful light determination in step S28 of the flowchart in FIG. 7;

FIG. 12 is a flowchart illustrating an operation of a subroutine “harmful light determination” in step S28 of FIG. 7;

FIG. 13 is a flowchart illustrating an operation of a subroutine “harmful light determination” according to the second embodiment of the present invention.

FIG. 14 is a flowchart illustrating an operation of a subroutine “AF” according to the third embodiment of the present invention.

15A is a diagram showing a scene in a viewfinder to be photographed, FIG. 15B is a diagram showing sensor data obtained by imaging the scene shown in FIG. 15A with an AF sensor, and FIG. 15C is a backlight state FIG. 9 is a diagram showing sensor data obtained by imaging the scene shown in FIG. 7A with the AF sensor in a state in which the technology of extending the integration time of the AF sensor to output an image of a dark portion when the image is detected is applied. is there.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Focus adjustment control part, 12 Focus detection part, 13 Focus operation part, 14 Integral control part, 15 Night scene harmful light judgment part, 16 Auxiliary light part, 17 Lens drive part, 27 Photo lens, 30 Main mirror, 31 Finder optics System, 39 sub-mirror, 40 AF optical system, 50 shutter, 51 film, 55 camera control unit, 56 CPU, 57 interface IC, 60 exposure control unit, 61 film drive unit, 62 AF sensor, 62L, 62R photodiode array, 63 Aperture drive unit, 64 zoom control unit, 65 AF lens control unit, 66 photometry unit, 67 strobe control unit, 68 switch group, 77 pixel amplifier circuit (EAC), 78 shift register (SR), 79 sensor control circuit (SCC) .

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoichiro Okumura 2-43-2 Hatagaya, Shibuya-ku, Tokyo F-term in Olympus Optical Industry Co., Ltd. (reference) 2H011 AA01 BA21 BB05 DA08 2H051 BA02 BA20 CD01 CE01 CE06 CE08 EB19

Claims (3)

[Claims] 1. A focus detection device for detecting a focus adjustment state of a photographic lens with respect to an object in a predetermined area in a screen using a charge accumulation type photoelectric sensor, wherein the charge accumulation time of the charge accumulation type photoelectric sensor is controlled. Control means for determining whether or not a noise light source is present in the predetermined area based on the output of the charge storage type photoelectric sensor. The control means includes: When it is determined that a noise light source is present in the predetermined area, a charge accumulation time that is longer than the charge accumulation time is set, or an auxiliary light that can be operated during the charge accumulation time is activated. A focus detection device for re-accumulating the charge accumulation type photoelectric sensor. 2. The charge accumulation type photoelectric sensor has a plurality of pixels, and the determination means determines a level difference between a pixel showing a maximum output of the plurality of pixels and a pixel adjacent to the pixel by a predetermined level. The focus detection apparatus according to claim 1, wherein it is determined whether or not the noise light source is present as compared with the focus detection apparatus. 3. The charge storage type photoelectric sensor has a plurality of pixels, and the determination means determines whether the noise light source is present based on a charge storage time and an average level of all pixels. The focus detection device according to claim 1, wherein: