JP2001305418A - Focus detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a charge storage time by using a photoelectric conversion signal near a calculation area when the value of a photoelectric conversion signal in the calculation area of an image sensor array is equal to or exceeding a saturation level. SOLUTION: Object light transmitted through a lens 91 is image-formed on the image sensor array 2 by a focus detecting optical system 1. The corresponding photoelectric conversion signal to the incident light quantity is outputted by the image sensor array 2 in accordance with an element position. A prescribed arithmetic operation is performed by using each signal level of plural photoelectric conversion signals outputted from plural pixel areas of the image sensor array 2 and each position of the pixel areas for outputting respective photoelectric conversion signals on the image sensor array 2. The charge storage time Tn is calculated by a storage time control part 4 by using the maximum value Dmax when the maximum value Dmax of the photoelectric conversion signals D[As] to D[Ae] of the elements As to Ae (Fig.4) is below the saturation level, on the other hand, when the value Dmax is equal to or exceeding the saturation level, the charge storage time Tn is calculated by the control part 4 by using the photoelectric conversion signal D[As-i] of an element (As-i)(Fig.4) positioned adjacently on the left side of the element As. The charge storage time Tn is set in the image sensor array 2 by the control part 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a focus detection device for an autofocus camera.

[0002]

2. Description of the Related Art There is known a focus detection device which receives a subject light by a photoelectric conversion element such as a CCD and detects a focus adjustment state of a photographing lens based on a photoelectric conversion signal output from the photoelectric conversion element. The output signal level of the photoelectric conversion element changes according to the amount of incident subject light. If the amount of incident subject light is too large, the output signal level is too high to saturate, and if the amount of subject light is too small, the output signal level is low and the signal is susceptible to noise. Therefore, the photoelectric conversion signal level is appropriately adjusted by changing the charge accumulation time of the photoelectric conversion element in accordance with the luminance of the subject. As a method of detecting the subject brightness,
There are a method of providing a dedicated sensor for luminance detection and a method of detecting the luminance of the subject from the output signal level of the photoelectric conversion element. Generally, providing a dedicated sensor leads to an increase in cost. Therefore, a method of detecting subject brightness from the output signal level of the photoelectric conversion element is used. For example, Japanese Patent Application Laid-Open No. Hei 2-113215 discloses a maximum output value of a light-receiving element output from a photoelectric conversion element during photoelectric conversion.
A focus detection device that calculates and calculates a charge accumulation time so as to be output as an appropriate value at the next photoelectric conversion and controls the charge accumulation time of the photoelectric conversion element is described.

[0003]

However, in the focus detection device according to the prior art described above, if the charge conversion time of the photoelectric conversion element is longer than a predetermined time and the photoelectric conversion signal is saturated, the focus detection time is not related to the charge storage time. The photoelectric conversion signal level is clipped to the saturation level. Therefore, the relationship between the charge accumulation time and the signal level is not understood, and there is a problem that the charge accumulation time after the next time cannot be properly controlled.

[0004] It is an object of the present invention to provide a focus detection device that appropriately controls the charge accumulation time even when the photoelectric conversion signal output from the photoelectric conversion element is saturated.

[0005]

The present invention will be described with reference to FIGS. 2 and 3 showing one embodiment. (1) The focus detection device according to the first aspect of the present invention includes a charge storage type photoelectric conversion element 2 that outputs a photoelectric conversion signal in accordance with a subject light incident through a photographing lens 91, and a photoelectric conversion element that converts the subject light. Optical means 1 leading to a predetermined area 2
A focus detection unit 3 for detecting a focus adjustment state of the photographing lens 91 based on a photoelectric conversion signal output from a region of the photoelectric conversion element 2; The above-mentioned object is achieved by providing the control unit 4 for controlling the charge accumulation time of the photoelectric conversion element 2 based on the conversion signal. (2) The invention according to claim 2 is the focus detection device according to claim 1, further comprising a judgment unit 4 for judging whether or not the photoelectric conversion signal is saturated. 4 does not determine the saturation, the photoelectric conversion element 2
The charge accumulation time is controlled based on the photoelectric conversion signal output from the area of the photoelectric conversion element. When the determination unit 4 determines the saturation, the charge storage time is controlled based on the photoelectric conversion signal output from the vicinity of the area of the photoelectric conversion element 2. Is controlled. (3) The focus detection device according to the third aspect of the present invention includes a charge storage type photoelectric conversion element 2 that outputs a photoelectric conversion signal in accordance with subject light incident through the photographing lens 91, Light flux limiting means 90 for limiting the light flux
0, 400, the optical means 300, 501, 502 for guiding the light beam onto the photoelectric conversion element 2, and the photoelectric conversion signal output from the first area of the photoelectric conversion element 2 corresponding to the light beam. Focus detection means 3 for detecting a focus adjustment state, and photoelectric conversion based on the photoelectric conversion signal output from the first area and the photoelectric conversion signal output from the second area of the photoelectric conversion element 2 corresponding to the periphery of the light beam. By providing the control means 4 for controlling the charge accumulation time of the element 2, the above-mentioned object is achieved. (4) According to a fourth aspect of the present invention, in the focus detection apparatus according to the third aspect, a determination unit 4 for determining whether the photoelectric conversion signal is saturated is further provided. When the determination unit 4 does not determine the saturation, the charge accumulation time is controlled based on the photoelectric conversion signal output from the first region. When the determination unit 4 determines the saturation, the photoelectric conversion signal output from the second region. The charge storage time is controlled based on (5) According to a fifth aspect of the present invention, in the focus detection device according to any one of the first to fourth aspects, the control means 4 determines the output value of the photoelectric conversion signal and the charge storage time during the previous photoelectric conversion. The charge storage time at the time of photoelectric conversion is obtained from the storage means 4 for storing, the ratio between the target output value of the photoelectric conversion signal and the output value stored in the storage means 4, and the charge storage time stored in the storage means 4. And a calculating means 4 for calculating.

[0006]

The level of the photoelectric conversion signal output from a predetermined area of the photoelectric conversion element used for focus detection is higher than the level of the photoelectric conversion signal output from the vicinity of the predetermined area. Therefore, the photoelectric conversion signal from the vicinity of the predetermined area is less likely to be saturated than the photoelectric conversion signal from the predetermined area. The present invention utilizes such a phenomenon to optimize the charge storage time of the photoelectric conversion element so that the level of the photoelectric conversion signal output from a predetermined area of the photoelectric conversion element is close to the saturation level. Set to a value.

In the section of the means for solving the above-mentioned problems, the present invention is associated with the drawings of the embodiments for easy understanding of the present invention, but the present invention is not limited to the embodiments. is not.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a single-lens reflex camera including a focus detection device according to an embodiment of the present invention. FIG.
Is a camera body 70 and a finder device 80.
And an interchangeable lens 90. The finder device 80 and the interchangeable lens 90 are each detachable from the camera body 70. The interchangeable lens 90 includes a lens 91 and an aperture 92
And built-in.

In FIG. 1, a camera body 70 includes a quick return mirror 71, a shutter 72, a photosensitive member 73, a finder mat 81, and a pentaprism 82.
, Eyepiece 83, prism 84, and imaging lens 8
5, the photometric photoelectric conversion element 86, and the focus detection device 36. The subject light incident on the camera body 70 through the interchangeable lens 90 before the release is transmitted to the finder device 80 by the quick return mirror 71 located at the position shown by the dotted line.
It is led to. This subject light forms an image on the finder mat 81 and also on the focus detection device 36. The subject light focused on the finder mat 81 is guided to the eyepiece 83 by the pentaprism 82.
The subject light that forms an image on the viewfinder mat 81 is
A subject image is also formed on the photometric photoelectric conversion element 86 through the prism 84 and the imaging lens 85.

The subject light that enters the camera body 70 after the release passes through a lower portion of a quick return mirror 71 that is rotated to a position shown by a solid line, and forms an image on a photosensitive member 73 such as a film via a shutter 72. .

When a release switch (not shown) is half-pressed in the camera shown in FIG. 1, a photometric operation for detecting the brightness of the subject is performed. The luminance of the subject is detected by using a detection signal output from the photometric photoelectric conversion element 86 using a CPU (not shown).
Done in The CPU controls all camera operations including the photometric operation. The CPU detects the subject brightness and performs a predetermined calculation using the detected brightness, whereby the control shutter time and the control aperture value at the time of shooting are calculated.

The focus detecting device 36 detects a focus adjustment state of the lens 91. FIG. 2 is a block diagram illustrating an outline of the focus detection device 36. The focus detection device 36 has a focus detection optical system 1, an image sensor array 2, a focus detection calculation unit 3, and an accumulation time control unit 4, and detects the focus adjustment state of the lens 91. The focus detection optical system 1 includes a lens 9
The subject light passing through 1 is imaged on the image sensor array 2. The image sensor array 2 is a charge accumulation type line sensor such as a CCD, and outputs a photoelectric conversion signal corresponding to an incident light amount in accordance with an element position. The focus detection calculation unit 3 outputs signal levels of a plurality of photoelectric conversion signals output from a plurality of pixel regions of the image sensor array 2,
A predetermined calculation is performed using the position of the pixel area on the image sensor array 2 that outputs each photoelectric conversion signal. The storage time control unit 4 controls the charge storage time of the image sensor array 2 using the signal level of the photoelectric conversion signal.

Referring to FIG. 3, the configuration of the focus detecting device 36 and the principle of the focus detecting operation will be described. Focus detection device 36
Is controlled by the above-mentioned CPU (not shown). The focus detection optical system 1 includes a field mask 900, a field lens 3
00, aperture mask 400, re-imaging lenses 501 and 5
02 or the like. Region 800 is the exit pupil of lens 91 (FIG. 1). The areas 801 and 802 are areas where images are projected back onto the area 800 by the field lens 300 at the openings 401 and 402 formed in the opening mask 400. The focus detection optical system 1 is provided with an infrared light cut filter 700. The light beams incident through the regions 801 and 802 are focused on the equivalent surface 600 of the photosensitive member 73 (FIG. 1), and then the infrared light cut filter 700, the field mask 900, the field lens 300, the opening 401, An image is formed on the regions 201 and 202 on the image sensor array 2 via the 402 and the re-imaging lenses 501 and 502, respectively.

The area 201 of the image sensor array 2
The pair of subject images formed on 202 approach each other in a so-called front focus state where the lens 91 forms a sharp image of the subject before (subject side) the equivalent surface 600 of the photosensitive member 73,
Conversely, they move away from each other in a so-called rear focus state in which a sharp image of the subject is formed after the equivalent surface 600 of the photosensitive member 73. Then, regions 201 and 202 of the image sensor array 2
When a subject image formed at a predetermined interval is formed, a sharp image of the subject is located on the equivalent surface 600 of the photosensitive member 73. That is, the pair of subject images relatively match.

The focus detection calculation unit 3 performs a predetermined calculation using a photoelectrically converted electric signal of a pair of subject images formed on the image sensor array 2 to determine a relative distance between the pair of subject images. Ask. When the relative distance between the pair of subject images is obtained, the focus adjustment state of the lens 91, that is, the position where a sharp image is formed by the interchangeable lens 90 is shifted in which direction and how far from the equivalent surface 600 of the photosensitive member 73. That is, the shift amount is obtained. In FIG. 3, the focus detection area is the area 2 of the image sensor array 2.
01 and 202 are back-projected by the re-imaging lenses 501 and 502 and correspond to portions that overlap near the equivalent surface 600 of the photosensitive member 73.

The control of the charge accumulation time of the image sensor array 2 will be described in detail. Each of the signal levels of the photoelectric conversion signals output from the plurality of pixels of the image sensor array 2 increases when the amount of light incident on the image sensor array 2 is large, and decreases when the amount of incident light is small. In addition, even if the amount of incident light is the same, it increases when the charge accumulation time is long, and decreases when the charge accumulation time is short. The amount of charge stored in the image sensor array 2 is
Since the charge is limited by the capacity of the capacitor in which the charge is stored, the stored charge does not exceed the capacity of the capacitor. Therefore, when the amount of light incident on the image sensor array 2 is large or the charge accumulation time is long, the signal level of the photoelectric conversion signal output from the image sensor array 2 is limited to a predetermined value. The predetermined value that is limited is called a saturation level.

The photoelectric conversion signal output from the image sensor array 2 has noise. Since noise exists irrespective of the signal level of the photoelectric conversion signal, increasing the photoelectric conversion signal level so as to approach the saturation level makes it less likely to be affected by the noise. Therefore, by controlling the charge storage time of the image sensor array 2 so as to increase the photoelectric conversion signal level as much as possible within a range not reaching the saturation level, control is performed so that the photoelectric conversion signal level is substantially constant regardless of the incident light amount. I do. This control is called auto gain control (AGC).

FIG. 4 is a diagram for explaining a photoelectric conversion signal output from the image sensor array 2. (a) is a diagram showing the element row n of the image sensor array 2, and (b) is an image sensor array 2 having a uniform brightness like white paper.
FIG. 9A is a diagram illustrating a photoelectric conversion signal D [n] output from an element row n in FIG. In FIG. 4B, the horizontal axis represents the element number, and the vertical axis represents the signal level. In FIG. 4A, the image sensor array 2 has M represented by elements 1 to M.
Element rows n. Among these, the range indicated by the element As to the element Ae corresponds to the region 201, and the range indicated by the element Bs to the element Be corresponds to the region 202. In FIG. 4B, the photoelectric conversion signal D is output from the region 201 and the region 202 of the element row n.
[As] to D [Ae] and D [Bs] to D [Be] are output. The above-described focus detection calculation unit 3 sets the photoelectric conversion signals D [As] to D [
The above-described calculation is performed using [Ae] and D [Bs] to D [Be].

In FIG. 4B, the region 2 of the element row n
The photoelectric conversion signal values output from areas other than 01 and the area 202 are 0. However, in the vicinity of the elements As, Ae, Bs, and Be, that is, the left side of the element As, the right side of the element Ae, the left side of the element Bs, and the right side of the element Be have diffraction and edge generated at the edges of the openings 401 and 402 in FIG. The output photoelectric conversion signal value changes stepwise due to lens aberration of the lens 91 (FIG. 1) and the focus detection optical system 1.

The storage time controller 4 of FIG. 2 calculates the next charge storage time Tn by the following equation (1).

Tn = Tp × Lr / Lp (1) where Tp is the charge storage time during the previous photoelectric conversion, Lr is the maximum value of the target photoelectric conversion signal D [n], and Lp is the previous charge storage. This is the maximum value of the photoelectric conversion signal D [n] output at that time.

According to the above equation (1), the previous signal level Lp
Is lower than the target signal level Lr, the charge storage time Tn is set to be longer than the previous charge storage time Tp in accordance with the ratio between Lr and Lp, and the signal level obtained by the storage based on the storage time Tn is the target signal level Lr. Can be expected to be approximately equal to Conversely, when the previous signal level Lp is higher than the target signal level Lr, the charge accumulation time Tn is set shorter than the previous charge accumulation time Tp in accordance with the ratio between Lr and Lp, and is obtained by accumulation based on the accumulation time Tn. The expected signal level can be expected to be approximately equal to the target signal level Lr. Note that the target signal level Lr is set to a value as large as possible within a range where the image sensor array 2 is not saturated.

If the previous signal level Lp is equal to or higher than the saturation level, the next charge accumulation time is calculated as follows.
FIG. 5 is an enlarged view of the vicinity of the element As in FIG.
(a) shows the photoelectric conversion signal when the maximum value of the output photoelectric conversion signal does not reach the saturation level indicated by the dotted line, and (b) shows the case where the subject brightness is twice as large as that of (a) FIG. 7C is a diagram illustrating a photoelectric conversion signal output when the subject luminance is four times as large as that illustrated in FIG. In (b) and (c), the maximum value of the photoelectric conversion signal has reached the saturation level. Note that the charge accumulation times in (a) to (c) are the same.

In FIG. 5A, the photoelectric conversion signal output from the element located on the right side of the element As has substantially the same signal level because the luminance of the subject is uniform. The element located on the left side of the element As corresponds to the light-shielding portion around the light beam passing through the opening 401, but is not completely in the light-shielded state due to the light wraparound caused by the above-described diffraction and lens aberration. Therefore, the light wraps closer to the element As, and the amount of light sneaking decreases as the distance from the element As decreases, and the light is gradually shielded. As a result, the signal level of the photoelectric conversion signal output from the image sensor array 2 gradually decreases as the distance from the element As changes from the element (As-1) to the element (As-4). The stepwise lowering of the signal level in the light shielding portion is common to the vicinity of the elements Ae, Bs, and Be.

The photoelectric conversion signal level in FIG. 5B is twice as large as the photoelectric conversion signal level in FIG. However, the photoelectric conversion signal output from the right side of the element (As-1) is clipped at the saturation level.
The output is not doubled as compared with (a). The photoelectric conversion signal level in FIG. 5C is twice as large as the photoelectric conversion signal level in FIG. However, the element
Since the photoelectric conversion signal output from the right side of (As-2) is clipped at the saturation level, the output is not doubled as compared with FIG. 5B.

On the other hand, in an element such as the element (As-4) and the element (As-3) which is located away from the element As, the amount of incident light is smaller than the amount of light incident on an element adjacent to the element As. Since it is small, the output photoelectric conversion signal is unlikely to reach the saturation level. Therefore, when the maximum value Lp of the photoelectric conversion signal D [n] obtained at the time of the previous charge accumulation is equal to or higher than the saturation level, the value of the photoelectric conversion signal output from the element located far from the element As is used. The next charge accumulation time is calculated by the following equation (2).

Tn = Tp × (Lr × Kb) / Lop (2) where Tp is the charge accumulation time at the previous photoelectric conversion, Lr is the maximum value of the target photoelectric conversion signal D [n], and Lop is The photoelectric conversion signal D [As-i] and the coefficient Kb output from the element (As-i) located away from the element As during the previous charge accumulation are the same as those of the element As and the element (As-i) in a state without saturation. ) Is the output ratio.

For example, when the photoelectric conversion signal at the time of the previous charge accumulation is shown in FIG. 5B, the photoelectric conversion signal at the next charge accumulation is the charge accumulation as shown in FIG. Consider the case of calculating time. In this case, the next charge accumulation time is calculated using the photoelectric conversion signal D [As-2] output from the element (As-2) not reaching the saturation level instead of the element As reaching the saturation level. Is calculated. The signal value output from the element (As-2) is 1 / the value of the signal output from the element As.
If it is twice, the next charge accumulation time Tn is
By setting the coefficient Kb = １ ／ in (2), it is possible to calculate a charge accumulation time that is 倍 times the previous charge accumulation time Tp.

When the charge accumulation time Tn of the image sensor array 2 is calculated by the accumulation time control unit 4 as described above,
The accumulation time control unit 4 sets the next charge accumulation time Tn, and causes the image sensor array 2 to accumulate charges.
The focus detection calculation unit 3 converts the photoelectrically converted signals D [As] to D [Ae] and D [Bs] to D [B
e] to perform the above-described calculation. 1, when the focus detection state of the lens 91 is detected by the focus detection device 36, the focus position of the lens 91 is adjusted by a lens driving device (not shown). Thereafter, when a release switch (not shown) is fully pressed, the quick return mirror 71 jumps up, and the aperture 92 is controlled to the control aperture value described above.
The shutter 72 is controlled by the above-described control shutter time to perform photographing.

The operation described above will be described with reference to the flowchart of FIG. FIG. 6 is a flowchart illustrating a processing procedure for determining a charge accumulation time when detecting a focus adjustment state. In step S1, when a release switch (not shown) is half-pressed, the processing in FIG. 6 is started. A predetermined value stored in a memory (not shown) in the accumulation time control unit 4 is read out and set as an initial value of the charge accumulation time Tn. In the following step S2, the accumulation time control unit 4
Sets the charge accumulation time Tn in the image sensor array 2 to accumulate electric charges, and proceeds to step S3. Step S
In 3, the storage time control unit 4 reads the photoelectric conversion signals D [1] to D [M] from the image sensor array 2. The read photoelectric conversion signals D [1] to D [M] are also sent to the focus detection calculation unit 3.

In step S4, the focus detection calculation unit 3
Are D [As] to D from among the photoelectric conversion signals D [1] to D [M].
The above-described calculation is performed using [Ae] and D [Bs] to D [Be], and the defocus amount of the lens 91 is obtained. In step S5, it is detected whether or not a command to stop the processing in FIG. 6 has been issued, and it is determined that the command has been issued (step S5).
6), and the process of FIG. 6 is ended. If it is determined that no output is made (negative determination in step S5), the process proceeds to step S6.

In step S6, the accumulation time control unit 4
, The charge accumulation time used in the accumulation operation in step S2 is set as the previous charge accumulation time Tp. Subsequent step S7
, The maximum value of the photoelectric conversion signals D [As] to D [Ae] is Dm
ax, and the process proceeds to step S8. In step S8, it is determined whether or not the maximum value Dmax is equal to or higher than the saturation level, and it is determined that the maximum value Dmax is equal to or higher than the saturation level (Yes in step S8).
11 and determine that it is less than the saturation level (step S8).
And the process proceeds to step S9. In step S9, Dmax is set as the photoelectric conversion signal Lp at the time of the previous charge accumulation, and the process proceeds to step S10. In step 10, the above equation
The charge accumulation time calculated in (1) is set as Tn, and the process returns to step S2.

On the other hand, in step S11, a counter
i is set to 1 and the process proceeds to step S12. Counter i
Is used to count the number of elements for determining the photoelectric conversion signal level near the element (As). Step S1
2, the photoelectric conversion signal D [As-i] output from the element (As-i)
i] is equal to or higher than the saturation level, and is determined to be equal to or higher than the saturation level (Yes in step S12) and step S1.
6 and determine that the level is lower than the saturation level (step S12).
And the process proceeds to step S13. Step S13
, The photoelectric conversion signal D [As-i] is set as the photoelectric conversion signal Lop at the time of the previous charge accumulation, and the process proceeds to step S14. In step 14, the output ratio Kb [i] stored in advance in a memory (not shown) in the accumulation time control unit 4 is read and set as Kb. In step S15, the charge accumulation time calculated by the above equation (2) is set to Tn, and the process returns to step S2.

In step S16, it is determined whether or not the counter i is 4, and if it is determined that it is 4 (affirmative determination in step S16), the process proceeds to step S17, where it is determined that it is not 4.
(No in step S16) and the process proceeds to step S18.
In step S17, the storage time control unit 4
A predetermined value Ck stored in a memory (not shown) is read out, and the time calculated by the following equation (3) is set as the next charge accumulation time Tn, and the process returns to step S2.

Tn = Tp × Ck (3) Here, Tp is the charge accumulation time at the time of the previous photoelectric conversion, and Ck is a coefficient less than 1, and is usually set to Ck <Kb [4].
According to the above equation (3), the next charge accumulation time Tn is reduced by a predetermined ratio from the previous charge accumulation time Tp.

In step S18, the value of the counter i is set to 1
The process returns to step S12.

According to the embodiment described above, the calculation area of the image sensor array 2 used for calculating the defocus amount in the focus detection calculation section 3, that is, the element As
When the maximum value Dmax of the photoelectric conversion signals D [As] to D [Ae] of A to Ae is less than the saturation level, the charge accumulation time Tn is calculated using Dmax. The charge storage time Tn is obtained using the photoelectric conversion signal D [As-i] of the neighboring element (As-i). Therefore, when Dmax becomes equal to or higher than the saturation level, the next charge accumulation time Tn can be calculated even if the relationship between the previous photoelectric conversion signal Lp and the previous charge accumulation time Tp is unknown. As a result, it is possible to increase the photoelectric conversion signal level within a range that does not exceed the saturation level. Therefore, it is possible to calculate the defocus amount while reducing the influence of noise.

In the above description, the photoelectric conversion signals D [As] to D [Ae] of the elements As to Ae of the image sensor array 2 and the photoelectric conversion signal D [of the element (As-i) near the left side of the element As. As-
i] is used to calculate the charge storage time Tn, but the photoelectric conversion signal D [Ae + i] of the element (Ae + i) near the right side of the element Ae
May be used to determine the charge storage time Tn.
It may be obtained by using the photoelectric conversion signals near both sides together. Also,
The photoelectric conversion signals D [Bs] to D [Be] of the elements Bs to Be, the photoelectric conversion signal D [Bs-i] of the element (Bs-i) near the left side of the element Bs, and the element near the right side of the element Be ( Be + i) photoelectric conversion signal D [Be +
i].

As described above, near the elements As, Ae, Bs, and Be, the photoelectric conversion signal values output on the left side of the element As, on the right side of the element Ae, on the left side of the element Bs, and on the right side of the element Be are stepwise. Changes to The coefficient Kb representing this change has an individual difference for each focus detection device 36 due to an assembly error of the focus detection optical system 1 or the like. Therefore, Kb [i] is measured in advance for each device and stored in the memory of the accumulation time control unit 4.

In the above description, the counter i is counted up to four, but it is not limited to four.

In the above description, the line sensor is used for the image sensor array 2. However, a surface sensor having a two-dimensional imaging area can be used. In this case, the openings 401 and 40 of the opening mask 400
The data on the line in the direction in which the two luminous fluxes 2 are arranged on the surface sensor is used.

Further, in the above description, the maximum value Dmax of the photoelectric conversion signals D [As] to D [Ae] of the elements As to Ae of the image sensor array 2 obtained in the previous accumulation is set to Lp. The photoelectric conversion signals D [As] to D obtained in the previous accumulation
The average value of [Ae] may be set to Lp.

The correspondence between each component in the claims and each component in the embodiment of the invention will be described. The image sensor array 2 is a photoelectric conversion element, the focus detection optical system 1 is an optical unit, the element is an element. As to Ae are in a predetermined area and a first area, the focus detection calculation unit 3 is in focus detection means, the accumulation time control unit 4 is in control means, determination means and storage means, and the elements (As-1) to (As -4) near the region and in the second region, the field mask 900 and the aperture mask 40
0 corresponds to the light beam limiting means, and the field lens 300 and the re-imaging lenses 501 and 502 correspond to the optical means, respectively.

[0041]

According to the present invention as described in detail above, the following effects can be obtained. (1) In the focus detecting device according to the first, second, and fifth aspects of the present invention, a predetermined area of the photoelectric conversion element used for detecting the focus adjustment state of the photographing lens and the photoelectric conversion output from the vicinity of this area. The charge accumulation time of the photoelectric conversion element is controlled based on the signal. Therefore, even when the level of the photoelectric conversion signal output from the predetermined area of the photoelectric conversion element is saturated, for example, when changing from a low-luminance object to a high-luminance object, the photoelectric conversion output from the vicinity of the predetermined area is saturated. The charge accumulation time can be controlled using the signal. As a result, faster than the prior art,
Since it becomes possible to appropriately control the charge accumulation time,
Missing a photo opportunity is prevented. (2) In particular, according to the second aspect of the present invention, when the photoelectric conversion signal is not saturated, the charge accumulation time is controlled using the photoelectric conversion signal output from the predetermined area, and the photoelectric conversion signal is When saturated, the charge accumulation time is controlled using the photoelectric conversion signal output from the vicinity of the predetermined area, so that the charge accumulation time is appropriately controlled regardless of whether the photoelectric conversion signal is saturated. can do. (3) In the focus detection device according to the third to fifth aspects of the present invention, the light is output from the first region of the photoelectric conversion element corresponding to the restricted light beam and the second region of the photoelectric conversion element corresponding to the periphery of the restricted light beam. The charge accumulation time of the photoelectric conversion element is controlled based on the photoelectric conversion signal. Therefore, even when the level of the photoelectric conversion signal output from the first area corresponding to the restricted light flux is saturated, for example, when changing from a low-luminance subject to a high-luminance subject, the second area corresponding to the periphery of the restricted light flux The charge accumulation time can be controlled using the photoelectric conversion signal of (1). As a result, it is possible to appropriately control the charge accumulation time faster than in the related art. (4) In particular, in the invention according to claim 4, when the photoelectric conversion signal is not saturated, the electric charge accumulation time is controlled using the photoelectric conversion signal output from the first area corresponding to the restricted light flux. When the photoelectric conversion signal is saturated, the charge accumulation time is controlled using the photoelectric conversion signal output from the second area corresponding to the periphery of the restricted light beam. , The charge accumulation time can be appropriately controlled.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a single-lens reflex camera including a focus detection device according to an embodiment.

FIG. 2 is a block diagram illustrating an outline of a focus detection device.

FIG. 3 is a diagram illustrating a configuration of a focus detection device and a principle of a focus detection operation.

4A and 4B are diagrams illustrating a photoelectric conversion signal output from an image sensor array, where FIG. 4A illustrates an element array of the image sensor array, and FIG. 4B illustrates a case where the brightness of a subject is uniform; FIG. 7 is a diagram illustrating a photoelectric conversion signal output from an element row of FIG.

FIG. 5 is an enlarged view of the vicinity of an element As in FIG.
(a) is a diagram showing the case where the maximum value of the photoelectric conversion signal has not reached the saturation level, (b) is a diagram showing the case where the subject luminance is twice as large as (a), (c) is (a) FIG. 7 is a diagram illustrating a case where the subject luminance is four times as large as that of FIG.

FIG. 6 is a flowchart illustrating a processing procedure for determining a charge accumulation time when a focus adjustment state is detected.

[Explanation of symbols]

1: focus detection optical system, 2: image sensor array, 3: focus detection calculation unit,
4 accumulation time control unit 36 focus detection device
91: photographing lens, 201, 202: area on image sensor array, 300: field lens,
400: Opening mask, 401, 402: Opening,
501, 502: Re-imaging lens, 900: Field mask, D
[As] to D [Ae]: photoelectric conversion signals in the area 201, D [Bs] to D
[Be]: photoelectric conversion signals in the area 202 D [As-1] to D [As-4]: photoelectric conversion signals near the left side of the element As

Claims (5)

[Claims] A charge storage type photoelectric conversion element for outputting a photoelectric conversion signal in response to a subject light incident through a photographing lens; an optical unit for guiding the subject light to a predetermined area of the photoelectric conversion element; Focus detection means for detecting a focus adjustment state of the photographing lens based on a photoelectric conversion signal output from the area of the photoelectric conversion element; and photoelectric conversion output from the area and the vicinity of the area of the photoelectric conversion element A focus detection device comprising: control means for controlling a charge accumulation time of the photoelectric conversion element based on a signal. 2. The focus detection device according to claim 1, further comprising a determination unit that determines whether the photoelectric conversion signal is saturated, wherein the control unit determines that the determination unit is saturated. When there is not, the charge accumulation time is controlled based on the photoelectric conversion signal output from the area of the photoelectric conversion element, and when the determination unit determines the saturation, the charge output time is output from the vicinity of the area of the photoelectric conversion element. Wherein the charge accumulation time is controlled based on a photoelectric conversion signal. 3. A charge-storage type photoelectric conversion element for outputting a photoelectric conversion signal in accordance with subject light incident through a photographing lens; light flux limiting means for limiting the subject light to a light flux in a predetermined area; Optical means for guiding the light onto the photoelectric conversion element; focus detection means for detecting a focus adjustment state of the imaging lens based on the photoelectric conversion signal output from the first area of the photoelectric conversion element corresponding to the light flux; Based on the photoelectric conversion signal output from the first area and the photoelectric conversion signal output from the second area of the photoelectric conversion element corresponding to the periphery of the light beam, to determine a charge accumulation time of the photoelectric conversion element. A focus detection device comprising: a control unit for controlling the focus detection device. 4. The focus detection device according to claim 3, further comprising a determination unit for determining whether the photoelectric conversion signal is saturated, wherein the control unit determines that the determination unit is saturated. When there is not, the charge accumulation time is controlled based on the photoelectric conversion signal output from the first area, and when the determination unit determines saturation, based on the photoelectric conversion signal output from the second area. A focus detection device for controlling the charge accumulation time by using the control circuit. 5. The focus detecting device according to claim 1, wherein said control means stores an output value of a photoelectric conversion signal and a charge accumulation time during a previous photoelectric conversion; Calculating means for calculating a charge storage time during photoelectric conversion from a ratio between a target output value of the conversion signal and the output value stored in the storage means, and the charge storage time stored in the storage means; A focus detection device, comprising: