JP2003156676A - Autofocusing camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent out-of-focus from occurring by contriving how to widen a multi AF range-finding range in an autofocusing camera. SOLUTION: The first range-finding range is decided on the basis of a zoom position detected by a zoom position detection part 9a. If the detected zoom position is a telephoto side, the luminance of a subject is decided (step S46). When deciding that the luminance of the subject is low, the range-finding range is set to the one wider by one step (step S47). When deciding that the luminance of the subject is not low, the range-finding range is not changed (step S48). If the detected zoom position is standard, the luminance of the subject is decided (step S49). When deciding that the luminance of the subject is low, the range- finding range is set to the one wider by one step (step S50). When deciding that the luminance of the subject is not low, the range-finding range is not changed (step S51). If the detected zoom position is a wide angle side, the range- finding range is not changed (step S52).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a camera with a multi-autofocus function capable of measuring a plurality of points on a photographic screen.

[0002]

2. Description of the Related Art Recently, in addition to a camera with a spot auto-focus (AF) function, which has one distance measuring point,
Many cameras, which are so-called "multi-AF" cameras, have the function of measuring distances at multiple points. According to this conventional multi-AF camera, it is possible to measure the distances at a plurality of points on the screen and to focus, so that the correct focus can be achieved regardless of the position of the main subject on the screen.

At present, the AF system of a camera is a "passive type" which utilizes the image signal as it is from a subject.
There is an "active type" in which a distance measuring auxiliary light is projected onto a subject from the camera side. In addition, passive type A
Even in the F camera, when the subject is in a dark place or when the contrast of the subject image is low, auxiliary light is projected from the camera side to make the subject brighter or to make the subject bright and dark. There is also one that improves the accuracy of distance measurement by performing active AF-like processing. Further, there is also known a technique for improving the reflected light detection accuracy by providing a stationary light removing function for removing a component (steady light) other than the auxiliary light or the light for distance measurement from the reflected light from the subject. .

[0004]

However, depending on the shooting scene, the main subject may be out of the range of the multi-AF, and in that case, correct focusing cannot be performed and out-of-focus photography may occur. there were. For example, there is a case where a person who is a main subject as shown in FIG. 4A exists in the peripheral portion of the screen, or a case where there are a plurality of persons who are main subjects in the peripheral area of the screen as shown in FIG. .

In such a case, it may be possible to prevent out-of-focus by widening the range-finding range, but if the range-finding range is blindly widened, it may be affected by image signals other than the main subject. Out of focus may occur. Therefore, there is a demand for a camera that does not become out of focus even if it is out of the range of multi-AF by devising the way of expanding the range.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an autofocus camera which does not cause out-of-focus by devising a way to widen the distance measurement range of multi-AF.

[0007]

In order to achieve the above object, the autofocus camera according to the present invention detects the image signal relating to the subject and the projecting means for projecting the distance measuring light toward the subject. A sensor array, and a determination means for determining whether or not light projection by the light projection means is necessary,
When the determination means determines that the light projection by the light projection means is necessary, the detection area of the image signal by the sensor array is expanded.

That is, the autofocus camera of the present invention widens the detection area of the sensor array when it is determined that auxiliary light should be projected onto a subject when measuring the subject in a scene such as a night view. By taking it, the main subject can be put in the detection area of the sensor array, and the image will not be out of focus. Further, the distance measuring light is projected onto the subject and the reflected light is used to measure the distance. Therefore, even if the detection area of the sensor array is widened, it is unlikely to be affected by image signals other than the main subject.

In order to achieve the above object, the autofocus camera according to the present invention comprises a light projecting means for projecting distance measuring light toward a subject, and a sensor array for detecting an image signal relating to the subject. A determination means for determining whether light projection by the light projection means is necessary, and a focal length detection means for detecting the focal length of the photographing lens,
When the determining unit determines that the light projecting unit needs to project light, the detection area of the image signal by the sensor array corresponds to a shorter focal length side than the focal length detected by the focal length detecting unit. It is characterized in that it is set in the area to be set.

That is, in the autofocus camera of the present invention, when measuring the distance to an object in a scene such as a night view, it is detected by the focal length detecting means when it is determined that auxiliary light should be projected onto the object. By making the detection area of the sensor array wide according to the focal length, the main subject can be placed in the detection area of the sensor array, so that an out-of-focus photograph cannot be obtained. Further, the distance measuring light is projected onto the subject and the reflected light is used to measure the distance. Therefore, even if the detection area of the sensor array is widened, it is unlikely to be affected by image signals other than the main subject.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a portion related to a distance measuring device of an autofocus camera according to an embodiment of the present invention.

In the present autofocus (AF) camera, sensor arrays 3a and 3b in which pixels for light receiving elements are arranged in parallel are provided so as to face an object O to be measured. Further, in order to form an image of the subject O on the sensor arrays 3a and 3b, two light receiving lenses 2a and 2b are provided in front of the sensor arrays 3a and 3b at positions separated by a focal length f. These two light-receiving lenses 2a and 2b are arranged with a distance corresponding to the parallax B, and are configured so that the subject distance L can be obtained by the well-known "triangulation principle".

Depending on the size of the subject distance L, the image of the subject O formed on the two sensor arrays 3a and 3b changes the relative position with respect to the optical axis of each lens. In order to detect this, the A / D conversion unit 6 outputs an integrated output from the sensor arrays 3a and 3b (however, here, an integration circuit is used for each sensor array 3).
It is included in the pixels forming a and 3b. ) Is converted into a digital signal, and then output to the arithmetic control unit (CPU) 1 including a one-chip microcomputer. The integration of the sensor arrays 3a and 3b at this time is controlled by the CPU 1 via the integration determination unit 7.

Next, in the CPU 1, the two sensor arrays 3
By comparing the digital image signals of a and 3b, the parallax B causes 2
After detecting the relative position difference between the two digital image signals, the subject distance L can be obtained based on the relative position difference. Therefore, the CPU 1 determines a pattern of an image according to a predetermined control program to determine whether or not the pattern of the image is suitable for distance measurement.
Correlation calculation unit 1 for detecting the relative position difference between two images
c, when the result of the image pattern determination by the pattern determination unit 1b is a low contrast pattern, a repetitive pattern, a monotone increasing / decreasing pattern, or the correlation calculating unit 1
When the degree of coincidence of the images when the relative position difference is detected by c is small, it has a function such as a reliability determination unit 1d that determines that the reliability of the distance measurement is low. That is, A / D
The digital image signal input from the conversion unit 6 is input to the pattern determination unit 1b and the pattern of the image is determined. Then, the first reliability determination is performed by the reliability determination unit 1d based on the determined image pattern, and the digital image data for which the reliability of the image pattern is determined to be high is processed by the correlation calculation unit 1c in the relative position. After the difference is calculated, the reliability determination unit 1d makes a second reliability determination. Then, the subject distance L is calculated in the controller 1a based on the relative position difference determined to have high reliability,
The control amount of the focusing unit 9 is determined by the calculated subject distance L.

Further, after the focus adjustment of the taking lens (not shown) is performed by the focusing section 9, the CPU 1 detects the input state of the release switch 8 and starts the exposure operation for the film (not shown). At this time, the strobe light emitting section 5 is controlled to emit light via the strobe section 5a according to the result of the light quantity determination section 1e. The strobe light emitting section 5 is also controlled to emit light as needed even during distance measurement.

Further, the distance measuring device of this AF camera is
The ambient light removing unit 4 which is a circuit for removing a light component caused by ambient light such as sunlight or artificial illumination illuminating the subject O from an image of the subject O detected when the camera performs distance measurement. And a light amount determination unit 1e that determines the brightness of the subject O based on the output results of the sensor arrays 3a and 3b. When it is determined that the brightness of the subject O is low based on the measurement result of the light amount determination unit 1e, the pulse width of the pulsed light projection by the strobe light emission unit 5 is determined according to the output of the light amount determination unit 1e at that time. And set the flash unit 5
The distance measurement light is projected from the object toward the object O to perform the distance measurement again. At the time of this re-ranging, the stationary light removing unit 4 removes the stationary light component to measure the distance.

Further, this AF camera has a zoom mechanism (not shown) for changing the focal length of the photographing optical system,
The zoom position detecting unit 9a for detecting the zoom position changing by the zoom mechanism uses the detected information as C
It is connected to PU1 so as to be notified. Further, this AF camera has an EEPROM 10 for storing an integrated voltage V _{INT and the} like which will be described later. Although the EEPROM is used as the storage device in the present embodiment, the storage device is not limited to this.

Next, the stationary light removing section will be described with reference to FIG. FIG. 2A shows an electric circuit diagram of a portion including a stationary light removing unit in the distance measuring device, and FIG. 2B shows a timing chart at the time of integration of a subject image.

The light receiving element 3a ₁ corresponds to one pixel forming the sensor arrays 3a and 3b for detecting image signals. Photocurrent I output from here according to the amount of incident light
_P is designed to flow to GND (ground) via the stationary light removal transistor 4a. At this time, the integrating amplifier 6a, the integrating capacitor 6b, the switch 6c, the switch 6
The current detector 4c controls the gate voltage of the stationary light removal transistor 4a so that the current does not flow in the integrating circuit composed of d and the like. This current detector 4c, switch 6c,
The switch 6d is controlled by the control unit 1a inside the CPU 1, and is turned on / off by a pulse signal from the CPU 1.
It is turned off.

The holding capacitor 4b is provided to fix the gate voltage. In this fixed state, for example, the strobe section 5a is caused to emit light so that the distance measuring light is projected onto the object O in a pulsed manner, and the current detecting section 4c
When is turned off, the voltage change across the capacitor 4b cannot respond to the rapid change in the pulsed light. When the switch 6d is turned on here, only the photocurrent corresponding to the pulsed light is input to the integrating circuit, and the output of the integrating amplifier 6a is a photoelectric conversion voltage (integrated voltage V _INT ) is output. Therefore, if the integrated voltage V _INT is A / D converted, the reflected light amount data (the digital image signal) corresponding to the reflected signal light can be detected. Then, the integrated voltage V _INT is previously stored in the EEPROM 10
When the predetermined voltage V _C stored in the CPU reaches the predetermined voltage V _C , the integration end signal is sent from the comparator for integration determination (the above-mentioned integration determination unit) 7 to the CPU.
It is output to 1. After receiving the integration end signal, the CPU 1 turns on the current detector 4c and turns off the switch 6d.
A pulse signal for outputting is output and the integration is completed. In the passive mode, which will be described later, the pulse signal output from the CPU 1 for ending the integration is not limited to the time when the integration end signal output from the comparator 7 is received, but the integration timing not shown inside the CPU 1 is also shown. It is also output when the timer reaches the predetermined time t _INT . Further, in the active mode, the pulse signal is output not when the predetermined time t _INT is reached but when the integration counter (not shown) inside the CPU 1 finishes integration a predetermined number of times n ₁ .

Further, in order to judge the brightness of the photographic scene, the current detector 4c is turned off, and the switch 6c is temporarily turned on as shown in FIG. 2 (B). pouring I _P, by measuring the integrated voltage _{V INT} after integration for the predetermined time _{t INT} EEPROM 1
Store at 0. Note that V _INT is generally used in bright scenes.
Is low and V _INT is high in a dark scene, so V
By measuring the _INT level, the light amount determination unit 1e can determine the brightness.

Next, the extension of the AF distance measuring range in the autofocus camera according to the embodiment will be described with reference to FIG.

FIG. 3A is a diagram showing a state in which the AF distance measuring range is changed according to the photographing angle of view of the camera.

Normally, the angle of view of the taking lens widens as the focal length decreases (toward the wide angle side). At this time, if the AF viewing angle is kept constant, the ratio of the AF viewing angle to the field angle of the taking lens decreases, and it becomes impossible to focus on the subject in the peripheral portion of the screen of the taking lens. .

In order to prevent this, in the autofocus camera of the present embodiment, even if the focal length changes due to the zoom mechanism (not shown) and the photographing field angle widens,
The ratio of the angle to be measured to the shooting angle of view is kept constant. That is, as shown in FIG. 3A, the zoom position detected by the zoom position detection unit 9a and the EEPROM
Using the predetermined value related to the focal length stored in 10 as the photographing field angle becomes wide angle side, the sensor array 3
a, 3b (in FIG. 3A, one of the two sensor arrays)
Only one is shown. By increasing the number of pixels used in (4), the AF distance measuring range is switched to three stages of A, B, and C, for example. Of course, these three stages may be other plural stages.

FIG. 3B shows the relationship between the focal length and the AF distance measuring range. Predetermined values f ₁ and f ₂ of the focal length are stored in the EEPROM ₁₀ as information relating to the focal length.
The focal length ranges corresponding to the AF distance measuring ranges A, B, and C are determined by these f ₁ and f ₂ (for example, in FIG. 3B, the range from the zoom position of 38 mm to f ₁ (WID
Range of E) from the distance measurement range C13, _{f 1} to _{f 2} (ST
ANDARD) measuring range B12, f ₂ to 105 mm
The range (TELE) up to is defined as the range-finding range A11. ). In this state, the AF distance measuring range can be determined in three stages depending on which range of the focal length shown in FIG. 3B the zoom position detected by the zoom position detecting unit 9a falls within.

Next, consideration will be given to shooting when a subject exists in the peripheral portion of the shooting range in a night scene as shown in FIG. 4 (A).

The photographing range 14 and the AF distance measuring range at that time when the photographing scene is low in brightness and the photographing lens is at the telephoto (TELE) position are as shown in FIG. 4A, for example.
At this time, since the main subject (for example, a person) has low brightness in the night scene, the strobe light emitting unit 5 is controlled to emit light as the auxiliary light for distance measurement, and the distance to the main subject is measured. At this time, as shown in FIG. 5, the image signal output from the area corresponding to the distance measuring range A11 of the sensor array 3a (the sensor array 3b is the same is omitted.) Is low as shown in FIG. If the contrast is present (the image signal related to the night view is removed as the stationary light), the accurate distance to the main subject cannot be calculated.

Therefore, in the present embodiment, when it is determined that the main subject is measured at a low luminance such as a night scene, the AF distance measuring range is measured as shown in FIG. 4B. Expand the range A11 to the range B12. In this way, since the main subject enters the range B12, the image signal as shown in FIG. 5B is obtained, and the distance of the main subject can be measured. It should be noted that if the distance measurement range is blindly expanded as described above, it will be affected by image signals other than the main subject, but the distance measurement light is projected onto the subject and the reflected light component is extracted. If the distance is measured in this way, the image signals other than the main subject are not affected.

Operation control of the autofocus camera according to the present embodiment equipped with the distance measuring device having the above configuration will be described with reference to FIGS. 6 to 10. In addition,
As a term used in the following description, a range-finding mode in which range-finding light is not used but a relative position difference based on an image signal of a range-finding object is referred to as a "passive mode". A distance measuring mode in which light is projected onto a subject using the light emitting unit 5 or the like to measure a distance will be referred to as an "active mode". Further, the autofocus camera of the present embodiment is a multi-AF camera that divides the detection areas of the sensor array 3a and the sensor array 3b into a plurality of areas for distance measurement.

FIG. 6 is a flowchart showing the main operation in AF control of the AF camera. First,
Pre-integration in the passive mode is performed for a predetermined time (step S1). Here, the pre-integration in step S1 will be described in more detail with reference to FIG.

FIG. 7A is a flowchart showing the pre-integration in step S1 of FIG. 6 in more detail. First, in the pre-integration in the passive mode, first, the strobe light emitting unit 5 is not projected and the switch 6d is used.
Is turned on and the current detector 4c is turned off in FIG.
The switch 6c is temporarily turned on at the timing as shown in (B).
N to reset the value of integration. The integration is started after the value of the integration is reset. It should be noted that this integration is performed for a predetermined time t _INT to obtain the image signal of the subject (step S1A). At the same time, the integrated voltage V _INT at this time
Is detected and stored in the EEPROM 10. As described above, since V _INT is generally low in a bright scene and V _INT is high in a dark scene, bright / dark determination can be performed by detecting this V _INT . Next, as determined in subject brightness, the detected _{V I NT} advance EEP
It is determined whether or not it is larger than the predetermined value _Vth stored in the ROM 10 (step S1B). In this determination, it is determined that the brightness is low when V _INT is larger than V _th (step S1C), and the brightness is medium and high when V _INT is V _th or less (step S1D). To do.

After the pre-integration in step S1 above, the CPU
1 determines whether or not the main subject is determined to have low brightness as a result of pre-integration (step S2). After it is determined that the main subject has low brightness, the CPU 1 performs a range-finding range setting process described later (step S3). Then, active AF is performed to project the auxiliary light from the strobe light emitting unit 5 to the subject, perform integration again, and perform distance measurement calculation (step S).
4). Next, it is determined whether or not the distance measurement by the active AF has succeeded (step S5). When the distance measurement is successful, the AF control is ended as it is. When the distance measurement by the active AF is not successful, the light amount AF using the reflected light amount is performed (step S6), and the AF control flow ends. It should be noted that this distance measurement method using the light amount AF utilizes that when the light is projected and the reflected light amount is examined, a large amount of light is reflected from a short-distance subject and a small amount of light is reflected from a long-distance subject. This is a distance measurement method that is effective for a subject without contrast. However, it is assumed that the reflectance of the subject is within a predetermined range.

Even after the main subject is judged not to have a low brightness in the brightness determination in step S2, the CPU 1 carries out a range-finding range setting process for setting an AF range-finding range at a position different from that in step S3 (step S3). S7). Then, the passive AF is performed to measure the distance based on the relative position difference due to the image signals of the subject output from the two sensor arrays 3a and 3b (step S8). Next, it is determined whether or not the distance measurement by the passive AF is successful (step S
9). When the distance measurement is successful, the AF control is ended as it is.

On the other hand, after it is determined that the distance measurement by the passive AF has not succeeded, the CPU 1 executes the distance measurement range setting process (step S10). Then, the active AF for performing the distance measurement calculation after projecting the auxiliary light from the strobe light emitting unit 5 to the subject and performing integration again is performed (step S11).
Then, it is determined whether or not the distance measurement by the active AF has succeeded (step S12). When the distance measurement is successful, the AF control flow is ended as it is. When the distance measurement is not successful, the light amount AF using the reflected light amount is performed (step S13), and then the AF control is ended.

Next, the passive AF processing in step S8 will be described with reference to FIG. Note that FIG. 8 (A)
Shows a flow chart for explaining the flow of the operation of the passive AF, and FIG. 8B shows a timing chart at the time of integration in the passive mode.

First, in order to measure the integration time, the CPU 1
An internal unillustrated integral time counting timer is started (step S20). Here, if the integration time is set too long, the user may miss the shooting timing. Therefore, the integration limit time is defined as the normal integration time. Therefore, when the integration time exceeds the integration limit time, the integration in the passive mode is immediately ended. The integration limit time is stored in the EEPROM 10, is read by the control unit 1a at the time of integration, and is compared with the time of the integration time measuring timer.

After the integration time counting timer is started in step S20, the switch 6c is temporarily turned on at the timing shown in FIG. 8B to reset the integration value, and integration is started (step S21). Next, the CPU 1 determines whether or not the time t _INT measured by the integration time measuring timer has _{exceeded the} integration limit time t _lim , or the integration voltage V _INT is the integration end voltage V _png (passive mode) previously stored in the EEPROM 10. Corresponding to the predetermined voltage V _C in FIG. 2) in FIG. 2) is determined (step S22). If t _INT has not passed t _lim and V _INT is not smaller than V _png , the integration is continued. On the other hand, t _INT is t
_{When lim} has elapsed or when V _INT becomes smaller than V _{png, the} integration is immediately ended (step S23) and the integration time counting timer is stopped (step S24). In the determination of step S22, the integration end timing is determined by the integration voltage in addition to the integration limit time described above.
If the integration continues even if _INT becomes lower than the integration end voltage V _png , the integration voltage V _INT will eventually be saturated, and the image signal of the main subject and the image signal around the main subject can be distinguished. This is because it becomes impossible to perform accurate distance measurement. The integrated voltage V
_{For INT} , the integrated voltage of the pixel with the largest incident light amount among the pixels of the sensor array within the predetermined AF range may be selected, or the integrated voltage of the pixel with the smallest incident light amount may be selected.

After the integration is completed, the CPU 1 determines that the integrated voltage V
_INTAnd integration end voltage V_pngAt the end of integration
Integrated voltage V_INTIs the integration end voltage V_pngLess than
It is determined whether or not (step S25). Integral limit
Time t_INTV has passed _INTIs V_pngThan
If the distance does not decrease, distance measurement fails (step S2
As 6), the passive mode AF process is completed and the main flow is completed.
Return to

When V _INT is smaller than V _png after the integration is completed, the relative position difference of the object image signal due to the parallax B of the two sensor arrays 3a and 3b is calculated in the correlation calculating section 1c, and Based on the result, the control unit 1a calculates the subject distance L from the principle of triangulation (step S27). Since the autofocus camera according to the present embodiment is a multi-AF camera, the distance measuring area that outputs the closest distance is selected from the plurality of subject distances L obtained for the plurality of distance measuring areas ( In step S28), the process returns to the main flow.

Next, step S4 and step S11 described above.
The active AF process will be described with reference to FIG. 9A shows a flowchart for explaining the flow of the active AF operation, and FIG. 9B shows a timing chart at the time of integration in the active mode.

First, the CPU 1 clears the counting variable n of an integration counter (not shown) for measuring the number of integrations in the active mode to 0 (step S30). Then, at the timing shown in FIG.
Integration is performed while projecting light (step S3).
1). At this time, as described above, the stationary light component is removed from the image signal of the subject by the operation of the stationary light removing unit 4.

When the flash emission ends, the CPU
1 indicates that the integrated voltage V _{INT at} that time is previously stored in the EEPROM 1
The integration end voltage V _ang stored in 0 (corresponding to the predetermined voltage V _C in FIG. 2 in the active mode).
It is determined whether or not it is smaller than (step S3
2). Then, when V _INT becomes smaller than V _ang , the integration ends (step S35). On the other hand, V
_{If INT} is larger than V _ang , the counting variable n is checked to determine whether the integration has been performed a predetermined number of times n ₁ (step S33). Even if the integration has already been performed n ₁ times, the integration is ended (step S35). yet,
If the integration has not been performed n ₁ times, the count variable n is incremented by 1 (step S34),
The process returns to step S31 and integration is performed again. Here, the upper limit of n ₁ is set for the number of integrations because energy is wasted when strobe light projection integration is performed more than necessary, leading to a loss in distance measuring operation time and the like.

After the integration is completed, the result P (a value obtained by dividing the integrated voltage V _INT by the number of integration times n) of integrating the reflected light quantity is considered from the integrated voltage V _INT output from the integration circuit in consideration of the number of integration times. The pattern of the result P obtained by obtaining (step S36) and integrating the reflected light amount in the pattern determination part 1b is determined (step S37). Then, based on the determined pattern, the CPU 1 determines whether or not triangulation can be performed (step S38). When it is determined that the triangulation cannot be performed, it is determined that the distance measurement has failed (step S39), the active AF process is terminated, and the process returns to the main flow.

On the other hand, when triangulation can be performed, the correlation calculating unit 1c calculates the relative position difference of the object image signal due to the parallax B of the two sensor arrays 3a and 3b, and based on the result, the control unit. In 1a, the subject distance L is calculated from the principle of triangulation (step S40). Here, since the autofocus camera of the present embodiment is a multi-AF camera, the distance measuring area that outputs the closest distance is selected from the plurality of subject distances obtained for the plurality of distance measuring areas ( Step S41) returns to the main flow.

Next, the above steps S3, S7 and S10.
The range-finding range setting process in FIG. 10 will be described with reference to FIG.

First, the CPU 1 has the zoom position detector 9a.
The zoom position detected by is determined (step S
45).

The determined zoom position is TEL in FIG.
In the case of E (the initial AF distance measuring range is the distance measuring range A11), the process proceeds to step S46, and it is determined whether or not the luminance is determined to be low in the luminance determination in step S2 of FIG. 6 (step S46). . When the brightness is not low, that is, when the brightness is medium and high, it is not necessary to change the AF range, so the range A11 is selected as the AF range (step S4).
7) Return to the main flow. On the other hand, when the brightness is low, A
As the F range-finding range, the range-finding range B12 which is a one-step wide AF range is selected (step S48), and the process returns to the main flow.

The determined zoom position is the STA of FIG.
In the case of NDARD (the initial AF distance measuring range is the distance measuring range B12), the process proceeds to step S49 and step S2.
It is determined whether or not the brightness is determined to be low in the brightness determination (step S49). When the brightness is not low, that is, when the brightness is medium or high, there is no need to change the AF range, so the range B12 is selected as the AF range (step S5).
0), return to the main flow. On the other hand, when the brightness is low, A
As the F range-finding range, the range-finding range C13 that is a one-step wide AF range is selected (step S51), and the process returns to the main flow.

The determined zoom position is the WID of FIG.
In the case of E (the initial AF distance measuring range is the distance measuring range C13), the process proceeds to step S52, and the AF distance measuring range is selected as the distance measuring range C13 regardless of the brightness (step S5).
2) Return to the main flow. In the case of WIDE, the reason why the distance measuring range C13 is selected regardless of the luminance is that the number of pixels of the sensor array is limited and the AF distance measuring range cannot be expanded beyond a predetermined range. If the number of pixels of the sensor array has a margin, it is needless to say that the AF distance measuring range can be widened even during WIDE.

As described above, according to the present embodiment, the autofocus function has a function of changing the range-finding range so as to always occupy a fixed ratio with respect to the photographing range in association with the focal length of the photographing lens. In the camera, even if the shooting scene is against the background of the night scene as shown in FIG. 4A and the main subject is off the center of the screen, the main subject is out of the range by expanding the range. It is possible to prevent the main subject from becoming out of focus by focusing on. Furthermore, even when shooting a scene in which two people are lined up against a background of a night view as shown in FIG. 11, it is possible to prevent the main object from being out of focus due to a lack of focus in the distance measuring range. it can. Also,
When the range is expanded, the subject is projected, the reflected light component from the subject is extracted, and the range is re-measured to eliminate the effect of image signals other than the main subject due to the range expansion. be able to.

Although the present invention has been described based on the embodiment above, the present invention is not limited to the above-mentioned embodiment, and various modifications and applications are possible within the scope of the gist of the present invention. Of course, of course. For example, in the present embodiment, the distance measuring device having two types of distance measuring modes, that is, the active mode and the passive mode, is used, but a distance measuring device having only one of the distance measuring modes may of course be used.

Here, the summary of the present invention includes the following in addition to those described in the claims.

(1) A projection unit for projecting distance measuring light to a subject corresponding to a subject image appearing in a photographic screen, and a sensor array for detecting an image signal relating to the subject are provided.
An autofocus camera, characterized in that the effective area of a sensor array is widened when light is projected by the light projecting means during autofocus.

(2) Projecting means for projecting distance measuring light to a subject corresponding to the subject image shown in the photographic screen, a sensor array for detecting an image signal relating to the subject, and a focal length of the photographing lens. And a focal length interlocking sensor area switching means for switching the effective area of the sensor array in synchronization with the detection result of the focal length detecting means. An autofocus camera, characterized in that, when light projection is required, the effective area of the sensor array is set to an effective area smaller than the actual focal length by the focal length interlocking sensor switching means.

[0057]

As described in detail above, according to the present invention,
In an auto-focus camera that has the function of changing the distance measuring range so that it always occupies a fixed proportion to the shooting range in conjunction with the focal length of the taking lens, by devising and expanding the distance measuring range at low brightness It is possible to provide an autofocus camera that can suppress the frequency of out-of-focus even when shooting a nightscape as a background.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a portion related to a distance measuring device of an autofocus camera according to an embodiment of the present invention.

FIG. 2A is a circuit diagram for explaining a configuration of a stationary light removing unit, and FIG. 2B is a diagram showing a timing chart at the time of integration of a subject image.

FIG. 3 is a diagram for explaining setting of an AF distance measuring range.

FIG. 4 is a diagram for explaining setting of an AF distance measuring range during a night view.

FIG. 5 is a diagram showing a relationship between an image signal of a subject and an AF distance measuring range during a night view.

FIG. 6 is a diagram showing a flowchart for explaining AF control of the autofocus camera according to the embodiment of the present invention.

FIG. 7 is a diagram for explaining pre-integration in the passive mode.

FIG. 8 is a diagram for explaining passive mode AF.

FIG. 9 is a diagram for explaining active mode AF.

FIG. 10 is a diagram showing a flowchart for explaining distance measuring range setting processing.

FIG. 11 is a diagram showing an example when two types of subjects exist in a night view.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 CPU 1a Control part 1b Pattern determination part 1c Correlation calculation part 1d Reliability determination part 1e Light intensity determination parts 2a, 2b Light receiving lenses 3a, 3b Sensor array 3a ₁ Light receiving element 4 Steady light removing part 4a Steady light removing transistor 4b Capacitor 4c Current Detecting section 5 Strobe light emitting section 5a Strobe section 6 A / D converting section 6a Integrating amplifier 6b Integrating capacitors 6c, 6d Switch 7 Integral determining section 8 Release switch 9 Focusing section 9a Zoom position detecting section 10 EEPROM

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02B 7/08 G03B 15/03 J 2H053 7/30 15/05 7/32 G02B 7/11 N G03B 13 / 36 A // G03B 15/03 B 15/05 G03B 3/00 AF term (reference) 2F065 AA06 BB05 CC16 DD09 FF09 GG08 JJ02 JJ05 JJ25 NN02 NN17 NN20 PP22 QQ03 QQ14 QQ23 QQ25 QQ28 QQ51 2F112 BA01 CA02A08 A09A08 A08A08A08A09A08 FA03 FA07 FA12 FA14 FA19 FA29 FA33 2H011 AA01 BA05 BA14 BB04 DA01 DA08 2H044 DA01 DA02 DC00 2H051 BB07 BB16 CB20 CC17 CC18 DA07 DA31 EB01 EB07 EB20 2H053 AA01 DA00

Claims (3)

[Claims] 1. A light projecting means for projecting distance measuring light toward an object, a sensor array for detecting an image signal relating to the object, and a judgment as to whether or not light projection by the light projecting means is necessary. An auto-focus camera, comprising: a determination unit that determines whether to project the image signal by the sensor array when the determination unit determines that light projection by the light projecting unit is necessary. 2. A light projecting means for projecting distance measuring light toward an object, a sensor array for detecting an image signal relating to the object, and a judgment as to whether or not light projection by the light projecting means is necessary. And a focal length detecting means for detecting the focal length of the photographing lens, wherein when the determining means determines that light projection by the light projecting means is necessary, the image signal of the sensor array An autofocus camera, characterized in that a detection area is set to an area corresponding to a shorter focal length side than a focal length detected by the focal length detecting means. 3. The auto according to claim 1, wherein the determining means determines that light emission by the light emitting means is necessary when the brightness of the subject is low. Focus camera.