JP2003140024A - Focus detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To calculate the most suitable exposure value even in the case that a part of an image sensor output overflows by utilizing the output of a focus detecting image sensor for light measurement. SOLUTION: A range of photoelectric transducers which should be used for photometric value calculation, out of a plurality of photoelectric transducers of the image sensor is determined in accordance with the output signal of the image sensor, and a photometric value is calculated on the basis of outputs of photoelectric transducers within the range. Thus a range of photoelectric transducers of which the picture signals have overflowed can be excluded, and the output of the focus detecting image sensor is utilized for light measurement to calculate the most suitable exposure value.

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 detecting a focus adjustment state of a photographing optical system.

[0002]

2. Description of the Related Art A subject image formed by a focus detection optical system is received by a charge storage type photoelectric conversion device (hereinafter referred to as an image sensor), an output of the image sensor is arithmetically processed, and a planned focal plane of a photographing optical system. There is known an automatic focus adjusting device for a camera which detects a defocus amount of a subject image surface with respect to the, and drives a photographing lens according to the defocus amount to focus an image pickup optical system.

In this type of automatic focusing apparatus, whether or not the defocus amount can be detected and the reliability of the defocus amount as the detection result depend largely on the high contrast of the light luminance distribution of the object. Therefore, it is necessary to optimally reflect the contrast of the subject in the output of the image sensor. For example, for a subject having a light intensity distribution as shown in FIG. 7A, it is desirable that the image sensor output as shown in FIG. 7C be obtained. In FIG. 7, Vsat represents the saturation voltage level of the photoelectric conversion element.

However, when the accumulation time is short, the contrast of the image sensor output becomes low as shown in FIG. 7 (b). On the contrary, if the accumulation time is long, the original contrast of the image sensor output is lost as shown in FIG. Therefore, it is necessary to obtain an image sensor output of an appropriate size, and for that purpose, charge must be accumulated at an appropriate accumulation time.

In order to obtain an appropriate charge storage time, the peak value of the image sensor output in the next charge storage operation becomes an appropriate value based on the storage time in the previous charge storage operation and the image sensor output. There is a method of calculating a specific accumulation time. For example, it is assumed that the image sensor output as shown in FIG. 7B is obtained, the accumulation time at that time is Tb, and the image sensor peak output is Vb. In this case, in the next charge accumulation operation, as shown in FIG.
To obtain an appropriate image sensor output as shown in (c), the charge storage time

## EQU1 ## Tc = (Vc / Vb) .Tb. Here, Vc is a target value, and Vc = A · Vs
At and A are positive numbers less than 1, and the "appropriate size" of the image sensor output is determined by the size of A. If A is small, the contrast of the image sensor output will always be low, and conversely, if A is large, the image sensor output will be saturated immediately with a slight change in the brightness of the subject. However, it is assumed that the above-mentioned image sensor output does not include noise components such as dark current. This method will be referred to as AGC (Auto Gain Contro
ll).

By the way, not all the image sensor outputs obtained by the above control are always used for the focus detection calculation. For example, in a shooting scene in which a person stands in front of a group of buildings as shown in FIG.
When the image sensor receives the light flux from the subject that has passed through 1, the image sensor output has a high frequency as shown in FIG. 8B. Hereinafter, such a subject is referred to as a high frequency subject. In FIG. 8B, Vsat indicates the saturation level of the image sensor output, a1 and a3 indicate the peripheral area of the image sensor, and a2 indicates the central area of the image sensor. In such a case, the defocus amount can be sufficiently detected only by the pixel output in a relatively narrow range in the central portion of the image sensor. When focus detection calculation is performed using the pixel output of the entire range of the image sensor,
When the defocus amount of the surrounding subject such as the background is greatly different, it causes an error.

However, in a scene where a distant mountain range is photographed as shown in FIG. 9A, when the image sensor receives the light flux from the subject that has passed through the focus detection area 31, the image sensor output is as shown in FIG. It becomes a low frequency as shown in b). Hereinafter, such a subject is referred to as a low frequency subject. In FIG. 9B, Vsat indicates the saturation level of the image sensor output, a1 and a3 indicate the peripheral area of the image sensor, and a2 indicates the central area of the image sensor. In the case of a low-frequency subject, focus detection calculation cannot be performed because only a part of data in a low-frequency cycle can be obtained by only outputting pixels in a narrow range. In such a case, it is necessary to perform focus detection calculation using the pixel outputs of the entire range of the image sensor. Therefore, there is a method in which the focus detection calculation is first performed with the pixel output in the central portion of the image sensor, and the focus detection calculation is redone with the pixel output in the entire range when the calculation result is not obtained or the reliability of the calculation result is low. In such a case, AGC is performed using the pixel output at the center of the image sensor.

On the other hand, there is known a photometric device for a camera which measures the illuminance of a light flux from a subject on the film surface in order to expose a subject image on a film or the like. In a general camera photometric device, a mirror is inserted into the photographic optical system only during non-exposure to guide the light flux from the subject to a diffusing plate installed on the film equivalent surface, and a part of the light flux diffused by the diffusing plate is used. The illuminance is measured by measuring with a photoelectric conversion device. An SPD (Silicon Photo Diode) is often used as a photoelectric conversion device for photometry.

However, the photometric device of a camera is generally built in the viewfinder section, and when taking a picture without mounting the viewfinder on the camera or when mounting a viewfinder not equipped with the photometric device on the camera. This photo metering function cannot be used with.

In order to solve such a problem, a method of utilizing the output of an image sensor for focus detection for photometry has been proposed (for example, see Japanese Patent Laid-Open No. 6-175186). The photometric sensor receives light beams from a wide range of the object field, but the focus detection image sensor is a line sensor, and thus receives light beams from a very small range of the object field. Therefore, when the pixel output of the focus detection image sensor is used for photometry, it is desirable to perform the photometric calculation based on the pixel output of the entire range of the image sensor as much as possible.

[0011]

The photometric sensor has an SP.
A non-accumulation type photoelectric conversion device such as a D (Silicon Photo Diode) is often used. In this non-accumulation type photoelectric conversion device, the actual brightness of the object scene and the sensor output have a one-to-one correspondence in the detectable brightness range. Therefore, if the output of the photometric sensor has reached the overflow level, it can be recognized that the subject brightness is brighter than the detection limit, and the exposure should be controlled to the minimum. vice versa,
When the photometric sensor output is 0, it can be recognized that the subject brightness is darker than the detection limit, and the exposure should be controlled to the maximum.

On the other hand, the focus detection image sensor has C
A charge storage type photoelectric conversion device such as a CD sensor is often used. This charge storage type photoelectric conversion device is
1: 1 between the actual brightness of the scene and the image sensor output
Does not correspond to. Even if the scene is dark, the image sensor output may overflow if the charge accumulation time is lengthened, and conversely, if the charge accumulation time is shortened even if the scene is bright, the image sensor output becomes almost zero. .

Now, consider a shooting scene in which a person is on the bright window side of a dark room as shown in FIG. When the image sensor receives the light flux from the subject that has passed through the focus detection area 31 and the AGC control is performed in the central portion of the image sensor, the background is high in brightness, so that the peripheral portion of the image sensor has a waveform as shown in FIG. The pixel output in the range a1 overflows. However, the pixel output in the central area a2 of the image sensor corresponding to the main subject is at an optimum level, and the focus detection device can focus on this main subject.

However, the range a around the image sensor
It is not clear whether the bright background corresponding to 1 overflows because it is 4 times as bright as the main subject corresponding to the sensor central range a2 where the optimum pixel output is obtained, or because it is 10 times brighter than the main subject. Therefore, if a photometric calculation is performed based on the overflowed pixel output in the peripheral area a1 of the image sensor, an accurate luminance value cannot be calculated. In such a case, if AGC control is performed using the pixel outputs of the entire range a1 to a3 of the image sensor, the pixel output of the main subject corresponding to the sensor central range a2 is small as shown in FIG. 6B. Therefore, focus detection cannot be performed.

It is an object of the present invention to utilize the output of the image sensor for focus detection for photometry and calculate an optimum exposure value even when a part of the output of the image sensor overflows.

[0016]

According to a first aspect of the invention, an image sensor having a plurality of photoelectric conversion elements, which outputs an image signal according to a light intensity distribution of a subject image, and a light flux from the subject. A focus detection optical system for forming a subject image on the image sensor, focus detection calculation means for calculating the focus adjustment state of the photographing optical system based on the output signal of the image sensor, In a focus detection device including a photometric calculation unit that calculates a photometric value based on the output signal of the image sensor, the photometric calculation unit is an output signal of the image sensor from among a plurality of photoelectric conversion elements of the image sensor. The range used for the photometric value calculation is determined in accordance with the above, and the photometric value is calculated based on the output of the photoelectric conversion element included in the range. (2) In the focus detection device of the second aspect, the photometric calculation means determines a range in which the output of the image sensor does not exceed a predetermined value as a range used for the photometric value calculation. (3) In the focus detection device of claim 3, the photometric calculation means separates the plurality of photoelectric conversion elements included in the image sensor from a central portion near the optical axis of the focus detection optical system and the optical axis. When the range is divided into the peripheral part and the photoelectric conversion element whose output exceeds a predetermined value is not in the central part range and is in the peripheral part range, based on the output of the photoelectric conversion elements included in the central part range. The photometric value is calculated. (4) In the focus detection device according to claim 4, the photometric calculation means separates the plurality of photoelectric conversion elements included in the image sensor from a central portion near the optical axis of the focus detection optical system and the optical axis. When the photoelectric conversion element whose output is greater than a predetermined value is in the central area, the photometry is performed based on the outputs of the photoelectric conversion elements included in both the central area and the peripheral area. When the value is calculated and the photoelectric conversion element whose output exceeds a predetermined value is not in any of the central portion and the peripheral portion, the photoelectric conversion elements included in both the central portion and the peripheral portion are included. The photometric value is calculated based on the output. (5) In the focus detection device of the fifth aspect, the predetermined value is the saturation level of the photoelectric conversion element of the image sensor.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of one embodiment, and FIG. 2 shows the arrangement of focus detection areas of one embodiment.
As shown in FIG. 2 (a), the focus detection device according to the embodiment has five focus detection regions 21 to 25 set in the central part and the left, right, upper, and lower peripheral parts in the photographing screen, and Focus detection of the taking lens can be performed in the detection areas 21 to 25. In this embodiment, a pair of line image sensors as shown in FIG. 2B are provided corresponding to the respective focus detection areas 21 to 25. The line image sensor is an image sensor in which a plurality of pixels (photoelectric conversion elements) are arranged in one row, and is simply referred to as an image sensor in this specification. In the pair of image sensors shown in FIG. 2B, a2 and b2 are called the central area of the sensor, and a1, a3, b1, b3 are called the peripheral area of the sensor.

In this embodiment, a line image sensor in which a plurality of pixels (photoelectric conversion elements) are arranged in one line will be described as an example. However, a plurality of pixels are arranged two-dimensionally. The present invention can also be applied to an area image sensor.

In FIG. 1, each focus detection area 2 described above is used.
Light fluxes from the subjects within 1 to 25 pass through the objective lens 1 and the focus detection optical system 2 and are imaged on the image sensors 3a to 3e corresponding to the focus detection areas 21 to 25.
Each of the image sensors 3a to 3e is composed of a pair of line image sensors as shown in FIG. 2 (b). The output of the image sensor group 3 is A / D converted by the A / D converter 4 and then sent to the calculator 5.

The calculation section 5 is provided with a focus detection calculation section 6, an image sensor photometric value calculation section 7 and a focus detection area automatic selection section 8. The focus detection calculation unit 6 performs focus detection calculation based on the outputs of the image sensors 3a to 3e A / D by the A / D conversion unit 4, and the focus detection regions 21 to 21.
The defocus amount of 25 is calculated. The image sensor photometric value calculation unit 7 calculates the photometric value based on the control data and outputs of the image sensors 3a to 3e.

The focus detection area manual selection unit 12 is an operation member for the photographer to select an arbitrary area from the five focus detection areas 21 to 25. The focus detection area automatic selection unit 8 of the calculation unit 5 detects a focus to be a lens drive target based on the focus detection area selected by the focus detection area manual selection unit 12 and the calculation result by the focus detection calculation unit 6. Automatically select the area. Image sensor drive controller 9
Drives and controls the image sensor group 3 based on the output of the calculation unit 5. Further, the lens drive control unit 10 drives the motor 11 based on the defocus amount calculated by the calculation unit 5 to drive the objective lens 1 in focus.

The photometric sensor 13 is installed in a finder section of a camera (not shown), receives a light beam from a subject, photoelectrically converts it, and outputs it. The output of the photometric sensor 13 is A / D
After being A / D converted by the conversion unit 14, it is sent to the photometric sensor photometric value calculation unit 15. Photometric sensor Photometric value calculator 15
Calculates the photometric value based on the output of the photometric sensor 13. Further, the photometric sensor presence / absence detection unit 16 detects the presence / absence of the photometric sensor 13 and sends the detection result to the exposure control unit 17. The exposure control unit 17 calculates an exposure value based on the outputs of the image sensor photometric value calculation unit 7, the photometric sensor photometric value calculation unit 15 and the photometric sensor presence / absence detection unit 16, and the aperture (not shown) of the objective lens 1 or the shutter. Control the speed.

The focus detection calculation unit 6, the image sensor photometric value calculation unit 7, the focus detection area automatic selection unit 8, the photometric sensor photometric value calculation unit 15, and the exposure control unit 17 of the calculation unit 5 are single or plural. It is composed of the microcomputer and peripheral parts such as memory, and is realized by the software form of the microcomputer.

FIG. 3 is a flow chart showing a focus detection processing program, and FIG. 4 is a flow chart showing a photometric value calculation subroutine. The operation of one embodiment will be described with reference to these flowcharts. When the release button (not shown) of the camera is half-pressed, the focus detection apparatus according to the embodiment starts executing the focus detection processing program shown in FIG.

In step 11 of FIG. 3, the calculation section 5 gives the image sensor drive control section 9 initial data such as the initial value T0 of the charge storage time T of each of the image sensors 3a to 3e. The initial value T0 of the charge storage time T
May be an appropriate predetermined value, or may be the shortest accumulation time so that the output of the image sensor is not saturated when the subject is bright. In step 12, the image sensor drive control unit 9 performs the charge accumulation operation of the image sensor group 3 according to the given accumulation time T (T0 for the first time).

In step 13, the calculation section 5 requests the reading of the image sensor output of the area selected by the focus detection area manual selection section 12. When the photographer manually selects, for example, the focus detection area 21 in FIG. 2A, the selection number [i] (= 3a to 3e) of the image sensor is 3a. The image sensor drive controller 9 reads the pixel data of the image sensor [i] according to the request of the calculator 5.

In the following step 14, the arithmetic unit 5 outputs the read output of the image sensor [i] to the central areas a2, b2 of the image sensor and the peripheral areas a1, a3, b1 ,.
It is confirmed whether or not it overflows at b3. In this specification, for example, as shown in FIG. 6A, the photoelectric conversion element output of the image sensor is at the saturation level Vsat.
The state of exceeding is called overflow. For example, if there is an overflow pixel in one of the sensor central range a2 and b2, it is determined that the sensor central range has overflowed. Further, if there is an overflow pixel in any one of the sensor peripheral area a1, a3, b1, b3, it is determined that the sensor peripheral area overflows. In step 15, the calculation unit 5 determines the entire range a of the read image sensor output.
The peak values in 1, a2, a3, b1, b2, b3 and the peak values in the central range a2, b2 are detected.
In this specification, the peak value in the entire range of the image sensor is called the full range peak value, and the peak value in the central part of the image sensor is called the central part peak value.

In step 16, the calculation section 5 confirms whether or not there is a focus detection request for the read output of the image sensor [i]. The focus detection calculation is performed on the image sensor [i] corresponding to the focus detection area manually selected by the photographer. In step 17, the focus detection calculation unit 6 performs focus detection calculation, and in the following step 18, it is determined whether or not focus detection was possible, and whether or not the focus detection result is reliable. When a reliable focus detection result is obtained, the focus detection area automatic selection unit 8 sets the selection area by the focus detection area manual selection unit 12 as the automatic selection area, and the process proceeds to step 19. In step 19, the lens drive control unit 10 determines the motor 11 based on the focus detection result.
To drive the objective lens 1 in focus. On the other hand, if a reliable focus detection result is not obtained in step 18, the lens drive is not performed and the process proceeds to step 20.

In step 20, the presence / absence of the photometric sensor 13 is detected by the photometric sensor presence / absence detection unit 16. If the photometric sensor 13 is present, the output of the photometric sensor 13 is A / D converted by the A / D conversion unit 14 and sent to the photometric sensor photometric value calculation unit 15. Photometric sensor Photometric value calculator 1
5 is the exposure control unit 17 which indicates the photometric value of the photometric sensor as the calculation result.
Output to. The exposure control unit 17 determines the aperture (not shown) of the objective lens 1 based on the photometric value of the photometric sensor, and also determines the shutter speed of the shutter that shields the image recording member such as the film or the area / image sensor. . On the other hand, if it is determined in step 20 that there is no photometric sensor, the process proceeds to step 21, and the image sensor photometric value calculation unit 7 executes the subroutine shown in FIG.
Calculates the photometric value based on the image sensor output. This photometric value calculation processing will be described later.

In step 22, it is confirmed whether or not the focus detection processing described above has been completed for all the image sensors 3a to 3e. If there is an image sensor for which focus detection processing remains, the process returns to step 13 and The focus detection process is repeated. At the stage where the focus detection processing is started and the focus detection of the manually selected area is completed, the focus detection processing for other focus detection areas is not yet completed, so step 1
Return to 3. In steps 13 to 15, the image sensor output corresponding to another focus detection area is read to detect the overflow, the full range peak value, and the central peak value.

In step 16, the arithmetic unit 5 confirms whether or not there is a focus detection request for the read output of the image sensor [i]. Here, if the focus detection result is not obtained in the manually selected focus detection area, it is necessary to perform the focus detection calculation in another focus detection area, so the focus detection request is issued. Further, after performing the first charge accumulation control after starting the focus detection processing, if a focus detection result is obtained in the manually selected focus detection area, it is not necessary to perform focus detection calculation in another focus detection area. Since there is no focus detection request, no focus detection request is issued to the image sensor corresponding to another focus detection area. Further, after performing the second charge accumulation control after starting the focus detection processing, it is confirmed whether or not the manually selected area captures the same subject as in the previous focus detection operation. Predicted defocus based on the result of the focus detection operation up to the previous time, that is, whether the main subject is still with respect to the camera, how fast it is moving, how fast the lens is driven, etc. If it is close to the amount, it can be determined that the same subject as in the previous focus detection process is captured. However, when the predicted defocus amount and the defocus amount of the current calculation result are significantly different, it is considered that the main subject to be captured is removed from the focus detection area. In that case, a focus detection request is issued to the image sensor corresponding to another focus detection area.

In this way, when the focus detection area which is considered to capture the main subject is found, the focus detection area automatic selection unit 8 sets the area as the automatic selection area.
If there is a focus detection request, the process proceeds to step 17 as in the previous focus detection process, and if there is no focus detection request, the process proceeds to step 20. In steps 20 to 21, the presence or absence of the photometric sensor is confirmed as described above, and if the photometric sensor is not present, the photometric value is calculated based on the image sensor output.

In step 22, it is confirmed whether or not the processing for all the image sensors 3a to 3e is completed,
When the processing for all the image sensors 3a to 3e is completed, the process proceeds to step 23. In step 23, the calculation unit 5 calculates the next charge accumulation time for each of the image sensors 3a to 3e based on the central peak value and the charge accumulation time during the previous charge accumulation operation. Then step 1
Returning to step 2, the next charge accumulation operation and focus detection processing is performed.

Next, the photometric value calculation processing in the image sensor photometric value calculation section 7 will be described with reference to FIG. In step 21, it is judged whether or not the focus detection auxiliary light is on, or whether there is an interrupt that interrupts the accumulation during charge accumulation. If the auxiliary light is on or there is an interrupt, the routine proceeds to step 22. When the subject is dark and the image sensor output cannot be obtained sufficiently, or when long charge storage time is required to obtain sufficient output and the response of the focus detection operation deteriorates, the focus detection auxiliary A light (not shown) is turned on to illuminate the subject. But,
Since accurate luminance cannot be obtained for a subject illuminated by turning on the auxiliary light, the photometric value is not calculated based on the image sensor output when the focus detecting auxiliary light is on. Further, when the charge accumulation is interrupted by the exposure operation to the image recording member, the calculation of the photometric value based on the image sensor output is not similarly performed. The processing 1 of step 22 is to end the subroutine without performing photometric value calculation, that is, without doing anything.

On the other hand, if the auxiliary light is not turned on and there is no interruption for interrupting the charge accumulation, the process proceeds to step 23, and the entire range a1, a2, a of the image sensor [i] is
It is confirmed whether or not an overflow pixel is found in 3, b1, b2, b3. If there is no overflow pixel, the process proceeds to step 24, and the full range peak value is compared with the noise level. When the peak value of the entire range is larger than the noise level, the process proceeds to step 26 and the process 2 is performed.
That is, when there is no overflow pixel in the entire range of the image sensor [i], the photometric value is calculated based on the pixel output of the entire range. On the other hand, if the full range peak value of the image sensor [i] is smaller than the noise level, step 25.
Proceed to and check if the charge storage time is the longest. If it is the longest, the image sensor output cannot be increased even if the charge storage time is further lengthened, so the routine proceeds to step 26, where the photometric value is calculated. On the contrary, if the charge storage time is not the longest, there is a possibility that an appropriate image sensor output can be obtained by further increasing the charge storage time, and the process proceeds to step 27 to perform the process 1. That is, the photometric value is not calculated.

If there is an overflow pixel in step 23, the process proceeds to step 28, and it is confirmed whether or not there is an overflow pixel in the central areas a2 and b2 of the image sensor [i]. If there are no overflow pixels in the sensor central areas a2 and b2, the process proceeds to step 29,
The central peak value is compared with the noise level. If the central peak value is larger than the noise level, the process proceeds to step 31 and process 3 is performed. That is, when there is an overflow pixel only in the peripheral portion of the image sensor [i], the photometric value is calculated based on the pixel output of the central range a2, b2 of the image sensor [i]. On the other hand, if the central peak value is smaller than the noise level, the process proceeds to step 30 and it is confirmed whether the charge storage time is the longest. If the charge storage time is the longest, the output of the image sensor cannot be increased even if the charge storage time is further lengthened. Therefore, the process proceeds to step 31 to calculate the photometric value. If the accumulation time is not the maximum, there is a possibility that an appropriate image sensor output can be obtained by further increasing the charge accumulation time. Therefore, the processing proceeds to step 27 and processing 1 is performed. That is, the photometric value is not calculated.

If overflow pixels are found in the central areas a2, b2 of the image sensor [i] in step 28, the process proceeds to step 32, and it is confirmed whether or not the charge storage time is the shortest. If the charge storage time is the shortest, the output of the image sensor cannot be reduced even if the charge storage time is further shortened, and therefore the process proceeds to step 33 to calculate the photometric value. That is, when there is an overflow pixel in the central area of the image sensor, the photometric value is calculated based on the pixel output of the entire area of the image sensor [i]. If the charge storage time is not the shortest, it may be possible to obtain an appropriate image sensor output by further shortening the charge storage time.
The process proceeds to step 4 and the process 1 is performed. That is, the photometric value is not calculated. After the photometric value is calculated based on the image sensor output as described above, the process returns to the focus detection processing program shown in FIG.

Finally, a method of calculating a photometric value based on the image sensor output will be described. Image sensor
When the photometric value is calculated based on the pixel output of the entire range of [i], the average value of the pixel output of the entire range is calculated and substituted into Vavg [i]. Also, the central area a of the image sensor [i]
When the photometric value is calculated based on the pixel outputs of 2 and b2, the pixel output average value of the sensor central range a2 and b2 is calculated and substituted into Vavg [i]. Further, when the charge storage time at this time is Tx [i] and the offset of the device is Ofs, the image sensor photometric value AFBV [i] is obtained by the following equation.

## EQU00002 ## AFBV [i] = log ₂ (Vavg [i] / Tx [i]) + Ofs

As described above, the image sensors 3a to 3e
From a plurality of photoelectric conversion elements of, determine the range used for the photometric value calculation according to the image signal of the image sensor output,
Since the photometric value is calculated based on the output of the photoelectric conversion element included in that range, the range of the photoelectric conversion element in which the image signal overflows can be excluded, and the output of the focus detection image sensor is used for photometry. The optimum exposure value can be calculated using this.

Correspondence between the constituent elements of the claims and the constituent elements of the embodiment is as follows. That is,
The image sensors 3a to 3e are image sensors, the focus detection optical system 2 is a focus detection optical system, and the focus detection calculation unit 6
Represents the focus detection calculation means, and the image sensor photometric value calculation section 7 constitutes the photometry calculation means.

In the above-described embodiment, when the photoelectric conversion element output exceeds the saturation level Vsat, that is, when the photoelectric conversion element output overflows, the range including the photoelectric conversion element is excluded and the photometric value is excluded. However, if a predetermined level lower than the saturation level Vsat of the photoelectric conversion element is provided and the output of the photoelectric conversion element exceeds the predetermined level, the range including the photoelectric conversion element is excluded. The photometric value may be calculated.

[0042]

As described above, according to the present invention, for example, the range of the photoelectric conversion element in which the image signal overflows can be excluded, and the output of the focus detection image sensor can be used for photometry to obtain the optimum exposure. The value can be calculated.

[Brief description of drawings]

FIG. 1 is a diagram showing an arrangement of focus detection areas and area division of a pair of line image sensors according to an embodiment.

FIG. 2 is a diagram showing a configuration of an embodiment.

FIG. 3 is a flowchart showing a focus detection processing program according to an embodiment.

FIG. 4 is a flowchart showing a photometric value calculation subroutine of one embodiment.

FIG. 5 is a diagram showing a scene in which a person is on a bright window side of a dark room.

FIG. 6 shows an image sensor output (a) in the case where AGC is performed using the pixel output at the center of the image sensor for the object field shown in FIG. 5, and the AGC is performed using the pixel output in the entire range of the image sensor. It is a figure which shows the image sensor output (b) at the time of performing.

FIG. 7 is a diagram showing a relationship between a subject contrast and an image sensor output.

FIG. 8 is a diagram showing a shooting scene (a) when a person is standing in front of a building and an image sensor output (b) in such a shooting scene.

FIG. 9 is a diagram showing a low frequency object (a) and an image sensor output (b) of such a low frequency object.

[Explanation of symbols]

1 Objective lens 2 Focus detection optical system 3 image sensor group 3a-3e image sensor 4 A / D converter 5 computing section 6 Focus detection calculation unit 7 Image sensor metering value calculator 8 Focus detection area automatic selection unit 9 Image sensor drive controller 10 Lens drive controller 11 motors 12 Focus detection area manual selection section 13 Photometric sensor 14 A / D converter 15 Photometric sensor Photometric value calculator 16 Photometric sensor presence detector 17 Exposure control section 21-25 Focus detection area

Claims (5)

[Claims] 1. An image sensor having a plurality of photoelectric conversion elements, which outputs an image signal according to a light intensity distribution of a subject image, and a light flux from the subject is guided to the image sensor, and the subject image is formed on the image sensor. A focus detection optical system for forming an image, focus detection calculation means for calculating the focus adjustment state of the photographing optical system based on the output signal of the image sensor, and photometry for calculating a photometric value based on the output signal of the image sensor. In the focus detection device including a calculation means, the photometric calculation means determines a range to be used for the photometric value calculation according to an output signal of the image sensor from among the plurality of photoelectric conversion elements of the image sensor, A focus detection device, which calculates a photometric value based on an output of a photoelectric conversion element included in a range. 2. The focus detection device according to claim 1, wherein the photometric calculation means determines a range in which the output of the image sensor does not exceed a predetermined value as a range used for the photometric value calculation. Detection device. 3. The focus detection device according to claim 1, wherein the photometric calculation means includes a plurality of photoelectric conversion elements included in the image sensor, a central portion near an optical axis of the focus detection optical system, and the optical sensor. When the photoelectric conversion element whose output exceeds a predetermined value is not in the central area range and is in the peripheral area, the area of the photoelectric conversion element included in the central area is divided into a peripheral area distant from the axis. A focus detection device characterized by calculating a photometric value based on an output. 4. The focus detection device according to claim 1, wherein the photometric calculation means includes a plurality of photoelectric conversion elements included in the image sensor, a central portion near an optical axis of the focus detection optical system, and the optical sensor. When the range is divided into the peripheral part away from the axis and the output exceeds the predetermined value in the central part range, the output of the photoelectric conversion elements included in both the central part and the peripheral part. If there is no photoelectric conversion element whose output level exceeds a predetermined value in any of the central portion and the peripheral portion, it is included in both the central portion and the peripheral portion. A focus detection device, which calculates a photometric value based on the output of a photoelectric conversion element. 5. The focus detection device according to claim 2, wherein the predetermined value is a saturation level of a photoelectric conversion element of the image sensor.