JP5320857B2 - Focus adjustment device and imaging device - Google Patents

Description

  The present invention relates to a technique related to a plurality of focus detection areas set in a screen of an optical system, so-called multi-point AF technique. More specifically, the present invention relates to a focus detection device, a focus adjustment device, an imaging device, and a camera system.

Conventionally, there has been known a camera that detects a focus adjustment state of an optical system with respect to a plurality of focus detection areas set in a screen of the optical system.
JP 2005-173280 A

However, when the output of the signal obtained for the focus detection region selected as the focus adjustment target is small, there is a problem that the focus detection accuracy is lowered.
For example, when the auxiliary light is projected onto the subject and the focus is detected, and the brightness of the auxiliary light for each focus detection area is different, the brightness of the auxiliary light for the selected focus detection area is dark. In some cases, the output of the obtained signal is small and false focusing occurs.

According to a first aspect of the present invention, there is provided the focus adjustment apparatus according to the first aspect , wherein the first area is irradiated with illumination light having a predetermined luminance including a predetermined pattern used for the focus adjustment control, and the second area includes the predetermined luminance used for the focus adjustment control. A light irradiating unit that irradiates the subject with illumination light so that high-intensity illumination light is irradiated, a plurality of focus detection areas set in the photographing screen, and at least one of the plurality of focus detection areas Whether the selection unit to be selected and the focus detection area selected by the selection unit are the first focus detection area corresponding to the first area or the second focus detection area corresponding to the second area A first light receiving unit that receives a light beam corresponding to the first focus detection area, a second light receiving unit that receives a light beam corresponding to the second focus detection area, and the first light receiving unit. And before Is supplied the output of the second light receiving portion detects a focus adjustment state of the focus detection area selected in the selecting section by the phase difference detection method, focusing of the focusing control based on the detection result of the focus adjustment state And a control unit that controls the focus adjustment unit. The control unit selects the first focus detection area by the determination unit when the subject is irradiated by the light irradiation unit . When it is determined that the focus adjustment state is determined, the focus adjustment state is controlled based on the focus adjustment state of the second focus detection area not selected by the selection unit using the output of the second light receiving unit. Once in, it controls the focusing unit to perform focusing control based on the focus adjustment state of the first focus detection area selected in the selecting section by using the output of the first light receiving portion, Previous When the determination unit determines that the second focus detection area is selected, the focus adjustment state of the first focus detection area before performing focus adjustment control based on the focus adjustment state of the second focus detection area. The focus adjustment unit is controlled not to perform focus adjustment control based on the above .

  According to the present invention, even when a plurality of focus detection positions are set, false focusing can be eliminated and reliable focusing can be realized.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<Embodiment 1>
FIG. 1 is a configuration diagram showing a single-lens reflex camera to which the present invention is applied. In this figure, 2 is an imaging lens, 4 is a main mirror, 6 is a sub mirror, 8 is a focusing screen, 10 is a pentaprism, 12 is a finder, and 14 is an imaging device. Reference numeral 16 denotes a CCD line sensor used as an AF sensor, 18 denotes a microcomputer for performing AF calculation / control and AF auxiliary light projection control, 20 denotes a lens driving motor, and 22 denotes an EEPROM used as a nonvolatile memory. Reference numeral 25 denotes an AF auxiliary light projection unit that projects the AF auxiliary light pattern shown in FIG. In the present embodiment, the AF auxiliary light projection unit 25 is attached to an external strobe, and projects an AF auxiliary pattern, which will be described later, onto a subject located within a specified distance from the closest distance at which flash photography is possible. . Of course, the AF auxiliary light projection unit 25 can be incorporated into the single-lens reflex camera body.

  FIG. 2 is a diagram showing an AF auxiliary light pattern (luminance pattern) projected from the AF auxiliary light projection unit 25 onto the subject. As shown in the figure, the entire AF auxiliary light pattern is formed of a plurality of sets of pattern units. One set of pattern units (see FIG. 3B) is composed of four line-shaped bright portions and three line-shaped dark portions sandwiched between the line-shaped bright portions. In order to make maximum use of the light amount of the limited light source (LED), the auxiliary light pattern to be projected has a luminance difference as shown in FIG. In other words, in order to increase the reach of auxiliary light in an AF area that is frequently used, the AF auxiliary light projection unit 30 causes the high-luminance pattern unit group to have a cross shape at the center of the screen 200. An AF auxiliary light pattern is projected. In the other portions, the AF auxiliary light projection unit 30 projects the AF auxiliary light pattern so that the low-luminance pattern units are arranged in a tile shape.

  As described above, among the AF auxiliary light patterns projected from the AF auxiliary light projection unit 25, the cross-shaped high-luminance pattern unit group is located at the substantially central portion in the screen 200. That is, when an AF auxiliary light pattern is projected onto a subject (target) within the range where flash photography is possible, the high-intensity pattern unit group reflected from the subject (target) is positioned at the approximate center of the imaging screen. The projection direction of the AF auxiliary light pattern is set in advance.

  FIG. 3A is an explanatory diagram illustrating the principle of the AF auxiliary light projection unit 25. In this figure, 30 is an LED light source, 32 is a slit pattern plate, 34 is a projection lens, 36 is a dividing plate, and 38 is a subject (target) surface. The dividing plate 36 is a prism that refracts light that has passed through the slit pattern plate 32 in a plurality of directions, and a detailed configuration thereof will be described later with reference to FIG.

  FIG. 3B shows a slit portion (cutout region) and a light shielding portion when the slit pattern plate 32 is viewed from the LED light source 30 side. Instead of the LED light source 30 and the slit pattern plate 32, an LED having a light emission pattern similar to that of the pattern unit can be used.

  In FIG. 3A, the slit pattern formed by the slit pattern plate 32 is arranged in the vertical direction (Y-axis direction) by the action of the dividing plate 36. As a result, a high-luminance pattern unit and a low-luminance pattern unit are projected in a tile shape in the Y-axis direction. That is, as shown in a range AX in FIG. 2, a high-luminance pattern unit is arranged in the central portion of the photographing screen 200, and a low-luminance pattern unit is arranged in the other portions.

FIG. 4A is a view of the dividing plate 36 as seen from the LED light source 30 side. FIG. 4B shows an AA ′ section, a BB ′ section, a CC ′ section, a DD ′ section, and an EE ′ section of the dividing plate 36. As shown in the figure, the width _{W C} of the plane including the C-C 'cross section in which the center of the divider plate 36 is the largest, other widths _{W A, W B, W D} , sufficiently in comparison with _{W E} Widely set. As a result, a high-luminance pattern unit is projected on AX of the photographing screen 200 (see FIG. 2). Since the other AA ′ cross section, BB ′ cross section, DD ′ cross section, and EE ′ cross section have the inclination angles θa, θb, θc, and θd shown in FIG. The low luminance pattern units are arranged one above the other according to the surfaces having the respective inclination angles.

  The above description is about the range AX in FIG. 2, but the description is omitted because it is the same for other regions. However, the high luminance pattern units (vertical stripe patterns) arranged in the vertical direction (Y-axis direction) of the shooting screen are projected in a time-sharing manner after the horizontal stripe pattern described above is projected.

  FIG. 5 is a diagram showing the arrangement of CCD line sensors superimposed on the arrangement of so-called multi-point AF areas. The area of 5 rows and 3 columns in the center of the figure is a cross sensor where the images of the vertical CCD line sensor and the horizontal CCD line sensor intersect. All other areas are vertical CCD line sensors. Therefore, as apparent from the overlap of the AF auxiliary light pattern shown in FIG. 2 with this figure, the vertical stripe pattern is detected by the horizontal CCD line sensor for the 5 × 3 region in the center, and the other regions are detected. Detects a horizontal stripe pattern with a vertical CCD line sensor. Next, the principle of detecting this horizontal stripe pattern will be described with reference to FIGS.

  FIG. 6 is an explanatory diagram showing the positional relationship between the horizontal stripe pattern projected by the AF auxiliary light projection unit 25 and the vertical CCD line sensor that detects the horizontal stripe pattern. As is clear from this figure, the high-intensity horizontal stripe pattern corresponds to the AF area at the center, and the low-intensity horizontal stripe pattern corresponds to the four upper and lower AF areas. FIG. 7 schematically shows an output signal from the vertical CCD line sensor in this corresponding state.

  The output signal waveform of the vertical CCD line sensor is drawn on the right side of FIG. Among these waveforms, the output signal having the maximum amplitude is the output from the sensor that receives the horizontal stripe pattern with high luminance. The other line sensor output signals correspond to the low-brightness horizontal stripe pattern, as is apparent from comparison with FIG. In other words, a signal with high contrast is obtained from a sensor that receives a horizontal stripe pattern with high luminance, and a signal with low contrast is obtained from a sensor that receives a horizontal stripe pattern with low luminance.

  However, when a correlation calculation for focus detection is performed based on a signal with low contrast, the signal waveform appears to have periodicity, and false focusing may be caused by a so-called periodic shift waveform. Therefore, in the first embodiment, as shown on the left side of FIG. 7, correlation calculation for defocus amount calculation is first performed using the entire range (= temporary calculation range). The correlation calculation here refers to the correlation amount at each shift position while relatively shifting a pair of output signal sequences corresponding to the set focus detection calculation range by a predetermined amount within a preset shift range. This means that the focus adjustment state of the taking lens is detected based on the shift position that is calculated and gives the minimum correlation amount.

  The principle of the correlation calculation and the reliability determination of the correlation calculation accompanied by the interpolation process will be outlined below.

  FIG. 8 is an explanatory diagram showing an outline of the focus detection principle by the phase difference detection method. A light beam incident from the region 101 of the photographing lens 100 passes through the field mask 200, the field lens 300, the aperture opening 401, and the re-imaging lens 501, and a plurality of photoelectric conversion elements that generate an output corresponding to the incident intensity are formed in a one-dimensional manner. The image is formed on the image sensor array A arranged in a row. Similarly, the light beam incident from the region 102 of the photographing lens 100 passes through the field mask 200, the field lens 300, the aperture opening 402, and the re-imaging lens 502 and forms an image on the image sensor array B.

  A pair of subject images formed on the image sensor arrays A and B are separated from each other in a so-called front pin state in which the photographing lens 100 forms a sharp image of the subject before the planned focal plane, and conversely the planned focal plane. In the so-called rear pin state in which the sharp image of the subject is connected behind the object, they are close to each other, and the subject images on the image sensor arrays A and B are relatively coincident at the time of the so-called in-focus state that connects the sharp image of the subject to the planned focal plane. To do. Therefore, the pair of subject images are photoelectrically converted by the image sensor arrays A and B to be converted into electric signals, and these signals are subjected to arithmetic processing to obtain a relative positional shift amount between the pair of subject images. The focus adjustment state of the photographic lens 100, here, the distance away from the in-focus state and its direction (hereinafter referred to as defocus amount) can be known. The projected images by the re-imaging lenses 501 and 502 in the image sensor arrays A and B are overlapped in the vicinity of the planned focal plane, and this area becomes a focus detection area.

The calculation processing procedure for obtaining the defocus amount is as follows. Now, each of the image sensor arrays A and B is composed of a plurality of photoelectric conversion elements, and a plurality of output signal strings a [1],. . . , A [n], b [1],. . . Assume that b [n] is output (see FIGS. 9A and 9B). Then, the correlation calculation is performed while the data in a predetermined range of the pair of output signal sequences is relatively shifted by L by predetermined data. If the maximum shift number is lmax, the range of L is from −1max to lmax. Specifically, the correlation amount C [L] is calculated by Equation 1.

Here, Σ represents a total operation of i = k to r. In Equation 1, L is an integer corresponding to the shift amount of the data string as described above. The first term k and the last term r are changed depending on the shift amount L as shown in Equation 2, for example.

  Here, k0 and r0 are the first term and the last term when the shift amount L is zero. As the shift amount L changes, the ranges used for the correlation calculation of the A column and the B column shift in opposite directions. Note that there is a method in which the initial term k and the final term r are constant regardless of the shift amount L. In this case, the range used for the correlation calculation of one column is always constant, and only the other column is shifted.

  Since the relative positional shift amount is the shift amount L when the pair of data coincides with each other, the shift amount that gives the minimum correlation amount is detected from the correlation amount C [L] thus obtained. The defocus amount is obtained by multiplying the optical system shown in FIG. 8 by a constant determined by the pitch width of the photoelectric conversion elements of the image sensor array. Therefore, the larger the maximum shift number lmax, the greater the defocus amount that can be detected.

The correlation amount C [L] is a discrete value as shown in FIG. 9C, and the minimum unit of defocus amount that can be detected is limited by the pitch width of the photoelectric conversion elements in the image sensor arrays A and B. Will be. Therefore, by performing an interpolation operation based on the discrete correlation amount C [L], a true minimum value Cex can be newly calculated, and precise focus detection can be performed. As shown in FIG. 10, this is achieved by using a correlation value C [l], which is a minimum value, and correlation values C [l + 1], C [l-1] in shift amounts on both sides of the correlation value C [l-1]. And a deviation amount Ls that gives this is calculated by Equations 3 and 4.

In Expression 3, MAX {Ca, Cb} means that the larger one of Ca and Cb is selected. The defocus amount DF is calculated from the deviation amount Ls by Equation 5.

  In Equation 5, Kf is a constant determined by the pitch width of the photoelectric conversion elements of the optical system and the image sensor array shown in FIG.

It is necessary to determine whether the defocus amount obtained in this way truly indicates the defocus amount or due to fluctuation of the correlation amount due to noise or the like. When the condition shown in Equation 6 is satisfied, the defocus amount Is trusted.

  E1 and G1 in Equation 6 are predetermined threshold values. The numerical value E indicates how the correlation amount changes, and is a value that depends on the contrast of the subject. The larger the value, the higher the contrast and the higher the reliability. Cex is a difference when a pair of data most closely matches, and is originally 0. However, due to the influence of noise and the occurrence of parallax between the region 101 and the region 102, a slight difference occurs between the pair of subject images, so that it does not become zero. Since the influence of noise and the difference between the subject images is smaller as the subject contrast is higher, Cex / E is used as a numerical value representing the degree of coincidence between a pair of data. Of course, the closer Cex / E is to 0, the higher the degree of coincidence of the pair of data and the higher the reliability.

  In some cases, the contrast for one of the pair of data is calculated instead of the numerical value E, and the reliability determination is performed using the contrast. If it is determined that there is reliability, the photographing lens 100 is driven or displayed based on the defocus amount DF.

  The correlation calculation, interpolation calculation, and condition determination of Formulas 1 to 6 described so far are collectively referred to as “focus detection calculation”. In addition, when the photographing lens 100 is in focus, it is common to configure the focus detection device so that a pair of data matches when the shift amount L is almost zero, so that the image of the subject is A in the image sensor array. If the lens is not formed in the range from the first term k0 to the last term r0 in the row B, the photographic lens 100 cannot be focused on the subject. Therefore, the region for focus detection is determined by the first term k0 and the last term r0. Therefore, the data range from the first term k0 to the last term r0 is the “calculation range”. A region corresponding to the calculation range on the photographing screen is a focus detection region, and the photographer can focus the photographing lens on a desired subject by capturing the subject in the focus detection region.

  FIG. 11 is a flowchart showing a focus detection procedure according to the first embodiment. Each step described below is executed by the microcomputer 18 of FIG.

In step S01, accumulation of the CCD line sensor is started.
In step S02, it is determined based on the output level of the CCD line sensor whether or not irradiation with AF auxiliary light (see FIGS. 1 and 2) is necessary. If it is determined that AF auxiliary light irradiation is necessary, the process proceeds to step S03. On the other hand, if a negative determination is made, the control proceeds to step S21 described later.

In step S03, it is determined whether or not the AF area belongs to line C in FIG. Note that the same applies to the six columns in FIG. As a result of the determination, if it is determined not to belong to the C row (NO), the process proceeds to the next step S04. On the other hand, when it determines with belonging to C line (YES), the process after step S13 is performed.
In step S04, the provisional calculation range shown in FIG. 7 is set. That is, a range including all the normal calculation ranges A to E is set as a temporary calculation range. The provisional calculation range may be a range including a plurality of calculation ranges including a calculation range C that receives reflected light of high-luminance auxiliary light.
In step S05, a temporary reliability determination threshold is set in association with the correlation calculation based on the temporary calculation range. As described above, the reliability determination threshold values are values E1 and G1 (see Equation 6) for determining the reliability of the correlation calculation result. In general, since the reliability of the correlation calculation decreases as the calculation range becomes wider, a value larger than the reliability determination threshold value in the normal correlation calculation is set as the temporary reliability determination threshold value.

In step S06, the AF auxiliary light is turned on.
In step S07, new accumulation of the CCD line sensor is executed.
In step S08, the above-described “focus detection calculation” is executed based on the set temporary calculation range. That is, the defocus amount is calculated by performing correlation calculation, so-called three-point interpolation calculation, and reliability determination. Note that, as a result of the reliability determination of the correlation calculation, when a reliable defocus amount cannot be calculated, the AF process is terminated (not shown).
In step S09, 350 μm is set as the defocus amount determination threshold Th1, and the absolute value | def | of the defocus amount calculated in step S08 is compared. As a result, when | def | <Th1 is not satisfied, the process proceeds to step S10.
In step S10, the rotation amount of the lens drive motor 20 is calculated so that | def | becomes smaller, and the lens drive by the lens drive motor 20 is performed based on the calculation result. On the other hand, when | def | <Th1 is satisfied, the process proceeds to step S11.

In step S11, the calculation range is returned to the normal calculation range (that is, the original calculation range conventionally performed).
In step S12, the temporary reliability determination threshold set in step S05 is returned to the normal reliability determination threshold.
In step S13, accumulation of the CCD line sensor is executed.
In step S14, “focus detection calculation” is executed. Since this “focus detection calculation” is as described in step S08, description thereof is omitted. Similarly, when the reliable defocus amount cannot be calculated as a result of the reliability determination of the correlation calculation, the AF process is terminated (not shown).
In step S15, focus determination is performed. That is, a value (50 μm to 100 μm) satisfying Th1> Th2 is set as the focus determination threshold Th2, and comparison is made with the absolute value | def | of the defocus amount calculated in step S14. As a result, when | def | <Th2 is not satisfied, the process proceeds to step S16.
In step S16, the rotation amount of the lens drive motor 20 is calculated so that | def | becomes smaller, and the lens drive by the lens drive motor 20 is performed based on the calculation result. On the other hand, when | def | <Th2 is satisfied, the AF auxiliary light is turned off in step S17, and then the AF process is terminated.

If a negative determination is made in step S02 described above, AF processing is performed without turning on the AF auxiliary light. That is, CCD storage is executed in step S21, and “focus detection calculation” is executed in step S22. In step S23, focus determination is performed. As the focus determination threshold Th2, a value satisfying Th1> Th2 (50 μm to 100 μm) is set, and compared with the absolute value | def | of the defocus amount calculated in step S22. As a result, when | def | <Th2 is not satisfied, the process proceeds to step S24.
In step S24, the rotation amount of the lens drive motor 20 is calculated so that | def | becomes smaller, and the lens drive by the lens drive motor 20 is performed based on the calculation result. On the other hand, when | def | <Th2 is satisfied, the AF process is terminated.

-Actions and effects of the first embodiment-
(1) When focus light is detected by projecting auxiliary light onto a subject, if the brightness of the auxiliary light for each focus detection area is different, the brightness of the auxiliary light for the selected focus detection area is dark. In this case, the output of the obtained signal is reduced, and as a result, false focusing may occur. However, according to the first embodiment, such false focusing can be avoided.
(2) In the first embodiment, when the selected AF area does not correspond to the high-luminance AF auxiliary light, the focus is selected by selecting the range including the AF area corresponding to the high-luminance auxiliary light as the calculation range. Perform detection calculation and execute coarse adjustment. As a result, the inconvenience of falling into false focus can be avoided.

<Embodiment 2>
In the first embodiment described above, when the AF area does not belong to the C row or the 6th column (see FIG. 5), a wide calculation range is set as the temporary calculation range (see FIG. 7). In Embodiment 2, focus detection calculation for coarse adjustment is performed without changing the size of the calculation range.
The system configuration for implementing the second embodiment (FIG. 1) and the AF auxiliary light pattern (FIG. 2) are the same as those of the first embodiment. Furthermore, since it is applicable similarly about FIGS. 3-6, description is abbreviate | omitted.

  FIG. 12 is a flowchart showing a focus detection procedure according to the second embodiment. Each step described below is executed by the microcomputer 18 of FIG.

In step S31, accumulation of the CCD line sensor is started.
In step S32, based on the output level of the CCD line sensor, it is determined whether or not irradiation with AF auxiliary light (see FIGS. 1 and 2) is necessary. If it is determined that AF auxiliary light irradiation is necessary, the process proceeds to step S33. On the other hand, if a negative determination is made, the control proceeds to step S51 described later.

In step S33, it is determined whether or not the AF area belongs to line C in FIG. Note that the same applies to the six columns in FIG. As a result of the determination, if it is determined not to belong to the C row (NO), the process proceeds to the next step S34. On the other hand, when it determines with belonging to C line (YES), the process after step S42 is performed.
In step S34, line C is set as a temporary calculation range. That is, in the second embodiment, a wide temporary calculation range (entire range) as shown in FIG. 7 is not set. Therefore, as shown in step S05 of FIG. 11, there is no need to set a reliability determination threshold value for determining the reliability of the correlation calculation result.

In step S35, the AF auxiliary light is turned on.
In step S36, new accumulation of the CCD line sensor is executed.
In step S37, the above-described “focus detection calculation” is executed based on the set temporary calculation range (= C rows). That is, the defocus amount is calculated by performing correlation calculation, so-called three-point interpolation calculation, and reliability determination. Note that, as a result of the reliability determination of the correlation calculation, when a reliable defocus amount cannot be calculated, the AF process is terminated (not shown).
In step S38, 350 μm is set as the defocus amount determination threshold Th1, and the absolute value | def | of the defocus amount calculated in step S37 is compared. As a result, when | def | <Th1 is not satisfied, the process proceeds to step S39.
In step S39, the rotation amount of the lens drive motor 20 is calculated so that | def | becomes smaller, and the lens drive by the lens drive motor 20 is performed based on the calculation result. On the other hand, when | def | <Th1 is satisfied, the process proceeds to step S40.

In step S40, the calculation range is returned to the normal calculation range (that is, the original calculation range conventionally performed).
In step S42, accumulation of the CCD line sensor is executed.
In step S43, “focus detection calculation” is executed. Since this “focus detection calculation” is as described in the first embodiment, a description thereof will be omitted. Similarly, when the reliable defocus amount cannot be calculated as a result of the reliability determination of the correlation calculation, the AF process is terminated (not shown).
In step S44, focus determination is performed. That is, a value (50 μm to 100 μm) that satisfies Th1> Th2 is set as the focus determination threshold Th2, and comparison is made with the absolute value | def | of the defocus amount calculated in step S43. As a result, when | def | <Th2 is not satisfied, the process proceeds to step S45.
In step S45, the rotation amount of the lens drive motor 20 is calculated so that | def | becomes smaller, and the lens drive by the lens drive motor 20 is performed based on the calculation result. On the other hand, when | def | <Th2 is satisfied, the AF auxiliary light is turned off in step S46, and then the AF process is terminated.

If a negative determination is made in step S32 described above, AF processing is performed without turning on the AF auxiliary light. That is, CCD storage is executed in step S51, and "focus detection calculation" is executed in step S52. In step S53, focus determination is performed. As the focus determination threshold Th2, a value satisfying Th1> Th2 (50 μm to 100 μm) is set, and compared with the absolute value | def | of the defocus amount calculated in step S52. As a result, when | def | <Th2 is not satisfied, the process proceeds to step S54.
In step S54, the rotation amount of the lens drive motor 20 is calculated so that | def | becomes smaller, and the lens drive by the lens drive motor 20 is performed based on the calculation result. On the other hand, when | def | <Th2 is satisfied, the AF process is terminated.

-Actions and effects of the second embodiment-
(1) In the second embodiment, when the selected AF area does not correspond to the high-luminance AF auxiliary light, the AF area corresponding to the high-luminance AF auxiliary light is selected, and temporary focus detection is performed. Coarse adjustment is performed by performing an operation. As a result, the inconvenience of falling into false focus can be avoided.
(2) In the second embodiment, when row C or column 6 (an area corresponding to high-luminance AF auxiliary light) is not selected as the AF area, AF corresponding to high-luminance AF auxiliary light is selected. The area is selected and a temporary calculation is executed, but the size of the calculation range is the same as the conventional one. As a result, calculation processing can be simplified and calculation time can be shortened.

-Modification-
(1) In the first and second embodiments, the dedicated AF sensor 16 is used, but it is also possible to use an imaging and focus detection means. Hereinafter, this modification will be described with reference to FIGS.
In the modification described here, by using an imaging and focus detection unit having an imaging function and a focus detection function of a pupil division phase difference detection method, and a focus detection unit having a focus detection function of a pupil division phase difference detection method, Realizes highly accurate focus adjustment with high responsiveness.
FIG. 13 shows a digital still camera as a modification. The digital still camera 201 includes an interchangeable lens 202 and a camera body 203, and the interchangeable lens 202 is attached to the camera body 203 via a mount unit 204. The interchangeable lens 202 includes an objective lens 209, a zooming lens 208, a focusing lens 210, a diaphragm 211, and a lens drive control circuit 206. The lens drive control circuit 206 includes a CPU and a drive circuit (not shown), controls the driving of the focusing lens 210 and the aperture 211, detects the states of the zooming lens 208, the focusing lens 210 and the aperture 211, and communicates with a body CPU 214 described later. To transmit / receive lens information and focus adjustment information. On the other hand, the camera body 203 includes an imaging device 207 having a focus detection sensor, a body CPU 214, an LCD driver 215, an LCD (EVF) 216, an eyepiece 217, a memory card 219, a drive control circuit 220, an external operation member 221 and the like. Yes. The image sensor 207 incorporates a plurality of re-imaging type focus detection units (not shown) for performing focus detection at a plurality of focus detection positions, and provides the focus detection function and imaging function of the interchangeable lens 202. Have. The imaging element 207 has imaging pixels arranged in a two-dimensional manner, and a focus detection pixel array is incorporated in a portion corresponding to a plurality of focus detection positions.
The body CPU 214 performs read control of output from the image sensor 207, communication with the lens drive control circuit 206 (transmission / reception of lens information / focus adjustment information), focus detection and focus adjustment control of the interchangeable lens 202, imaging control during imaging, Controls the operation of the entire digital still camera. The body CPU 214 and the lens drive control circuit 206 exchange various information such as lens information and a defocus amount for driving the focusing lens via an electrical contact part 213 provided in the mount part 204. The LCD 216 functions as a liquid crystal viewfinder (EVF: electronic viewfinder), and the LCD driver 215 drives the LCD 216 to display various information such as a captured image and imaging conditions. The photographer can visually recognize the information through the eyepiece 217. The memory card 219 is an image storage for storing and storing image signals. The drive control circuit 220 includes a camera control circuit such as a timer, and the external operation member 221 includes an operation member used for various operations and settings of the digital camera such as a shutter button. The subject image formed on the image sensor 207 through the interchangeable lens 202 is photoelectrically converted by the image sensor 207, and the output is sent to the body CPU 214. On the other hand, the subject image formed on the image sensor 207 through the interchangeable lens 202 is
Photoelectric conversion is performed by the imaging pixels incorporated in the imaging element 207, and the output is sent to the body CPU 214. The body CPU 214 performs focus detection calculation based on the output of the focus detection pixel array of the image sensor 207, calculates the focus adjustment state of the interchangeable lens 202, that is, the defocus amount, and sends this defocus amount to the lens drive control circuit 206. send. The body CPU 214 stores the image signal generated based on the output of the imaging pixel in the memory card 219, and performs photometry of the object scene based on the output of the imaging pixel and the focus detection pixel to calculate the luminance. . Further, the body CPU 214 sends an image signal to the LCD driver 215 and causes the LCD 216 to display an image. Furthermore, the body CPU 214 switches and activates various controls in response to signals from the drive control circuit 220, and switches and activates various controls according to the switching of the external operation member 221 and the operation state. A CPU (not shown) of the lens drive control circuit 206 changes the lens information according to the focusing state, zooming state, aperture setting state, and the like. Specifically, the positions of the zooming lens 208 and the focusing lens 210 and the position of the aperture 211 are monitored, and the lens information is calculated according to the monitor information, or according to the monitor information from a lookup table prepared in advance. Select the lens information. Further, the lens drive control circuit 206 calculates a lens drive amount based on the received defocus amount, and drives the focusing lens 210 to a focal point based on the lens drive amount.

  FIG. 14 is a front view showing a detailed configuration of the image sensor 207. As shown in FIG. 14A, the imaging element 207 has an imaging pixel 310 arranged two-dimensionally, and focus detection pixels 311 are arranged as shown in the figure corresponding to five focus detection positions. Has been. As shown in FIG. 14B, the imaging pixel 310 includes the microlens 10 and the photoelectric conversion unit 11 for imaging, and the focus detection pixel 311 includes the microlens 10 and focus detection as shown in FIG. A pair of photoelectric conversion units 12 and 13 is provided.

  FIG. 15 is a cross-sectional view of the imaging pixel 310. In the imaging pixel 310, the microlens 10 is disposed in front of the imaging photoelectric conversion unit 11, and the photoelectric conversion unit 11 is projected forward by the microlens 10. The photoelectric conversion unit 11 is formed on the semiconductor circuit substrate 29. FIG. 16 is a cross-sectional view of the focus detection pixel 311. In the focus detection pixel 311, the microlens 10 is disposed in front of the focus detection photoelectric conversion units 12 and 13, and the photoelectric conversion units 12 and 13 are projected forward by the microlens 10. The photoelectric conversion units 12 and 13 are formed on the same semiconductor circuit substrate 29. The microlens 10 disposed in front of the imaging pixel 310 and the focus detection pixel 311 is disposed on the planned focal plane of the interchangeable lens 202.

  (2) In the second embodiment, the AF auxiliary light pattern having high luminance is associated with the C row and the 6th column (see FIG. 5), but the present invention is not limited to such a configuration. That is, the first light receiving means is a first array of photoelectric conversion element arrays in which a plurality of photoelectric conversion elements are arrayed, receives reflected light from a target onto which illumination light having a first luminance is projected, and receives second light. The light receiving means is a second array different from the first array of photoelectric conversion element arrays and receives reflected light from a target onto which the second illumination light having a luminance higher than the first luminance is projected. When the light quantity of the light beam received by the first light receiving means is smaller than the light quantity of the light flux received by the second light receiving means, the photoelectric conversion element array corresponding to the second array closest to the first array is used. It is possible to detect the focus adjustment state based on the obtained light reception signal.

(3) The first and second embodiments have been described on the assumption that the AF auxiliary light pattern is irradiated. However, the present invention can also be applied to the case where the AF auxiliary light pattern is not irradiated. That is, in the embodiment shown in FIG. 6, the correspondence relationship between the two types of luminance patterns and the AF area has been premised, but it is also possible to perform processing focusing on the amount of light flux received by the light receiving means.
More specifically, when the light amount of the light beam received by one light receiving unit is smaller than the light amount of the light beam received by the other light receiving unit, the focus adjustment of the optical system is performed based on the light reception signal obtained by the other light receiving unit. It is also possible to detect the state.
Here, when detecting the focus adjustment state of the optical system, the focus is based on the light reception signal obtained by at least one of the one light receiving means and the other light receiving means, as in the first and second embodiments. It is possible to detect the adjustment state. One light receiving means is a light receiving means for receiving a light beam corresponding to the first focus detection position set in the screen by the optical system, out of the light beams via the optical system. The other light receiving means is a light receiving means for receiving a light beam corresponding to a second focal position in a screen different from the first focus detection position out of the light flux through the optical system.

The above description is merely an example, and the present invention is not limited to the above-described embodiments and modifications unless the features of the present invention are impaired.
It is also possible to combine the embodiment and one of the modified examples, or to combine the embodiment and a plurality of modified examples.
It is possible to combine the modified examples in any way.
Furthermore, other forms conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

It is a block diagram which shows the single-lens reflex camera to which this invention is applied. It is a figure which shows AF auxiliary light pattern. It is explanatory drawing which shows the principle of AF auxiliary light projection part. It is a figure which shows the structure of a division board. It is a figure which shows the relationship between multipoint AF area arrangement | positioning and CCD line sensor arrangement | positioning. It is explanatory drawing which shows the positional relationship of the horizontal stripe pattern projected by AF auxiliary light projection part, and the vertical CCD line sensor which detects a horizontal stripe pattern. It is a figure which shows the calculation range by Embodiment 1, and the output signal of a CCD line sensor. It is explanatory drawing which shows the outline | summary of the focus detection principle by a phase difference detection system. It is a figure for demonstrating a correlation calculation. It is a figure for demonstrating a correlation calculation. 3 is a flowchart illustrating a focus detection procedure according to the first embodiment. 10 is a flowchart illustrating a focus detection procedure according to the second embodiment. It is a figure which shows the modification of this invention. It is a figure which shows the modification of this invention. It is a figure which shows the modification of this invention. It is a figure which shows the modification of this invention.

Explanation of symbols

2 Imaging lens 4 Main mirror 6 Sub mirror 8 Focus plate 10 Penta prism 12 Finder 14 Imaging element 16 AF sensor 18 Microcomputer 20 Lens drive motor 22 EEPROM
25 AF auxiliary light projection unit

Claims (8)

The first area is irradiated with illumination light having a predetermined brightness including a predetermined pattern used for focus adjustment control, and the second area is irradiated with illumination light having a brightness higher than the predetermined brightness including the predetermined pattern used for focus adjustment control. a light irradiation unit for irradiating illumination light to the subject as,
Multiple focus detection areas set in the shooting screen,
A selector for selecting at least one of the plurality of focus detection areas;
A determination unit that determines whether the focus detection area selected by the selection unit is a first focus detection area corresponding to the first area or a second focus detection area corresponding to the second area; ,
A first light receiving portion for receiving a light beam corresponding to the first focus detection area;
A second light receiving unit for receiving a light beam corresponding to the second focus detection area;
The outputs of the first light receiving unit and the second light receiving unit are supplied, the focus adjustment state of the focus detection area selected by the selection unit is detected by a phase difference detection method, and based on the detection result of the focus adjustment state A focus adjustment unit for controlling the focus adjustment;
A control unit for controlling the focus adjustment unit,
The control unit uses the output of the second light receiving unit when the determination unit determines that the first focus detection area is selected when the subject is irradiated by the light irradiation unit . The focus adjustment control is performed based on the focus adjustment state of the second focus detection area that is not selected by the selection unit, and the focus adjustment state becomes a predetermined state, and then the output of the first light receiving unit is used. Controlling the focus adjustment unit to perform focus adjustment control based on a focus adjustment state of the first focus detection area selected by the selection unit ;
When the determination unit determines that the second focus detection area is selected, the focus adjustment of the first focus detection area is performed before performing the focus adjustment control based on the focus adjustment state of the second focus detection area. A focus adjustment device that controls the focus adjustment unit so as not to perform focus adjustment control based on a state . The focus adjustment device according to claim 1, comprising:
In the case where the light irradiation unit is irradiating the subject and the control unit determines that the first focus detection area is selected by the determination unit, the control unit focuses only on the second focus detection area. A focus adjustment apparatus that performs focus adjustment control based on a focus adjustment state of the first focus detection area selected by the selection unit after performing focus adjustment control using the adjustment state. The focus adjustment device according to claim 1, comprising:
In the case where the subject is irradiated by the light irradiation unit , the control unit determines that the first focus detection area is selected by the determination unit, and the first focus detection area and the first focus detection area. The focus adjustment control is performed based on the focus adjustment state of the first focus detection area selected by the selection unit after performing the focus adjustment control using the focus adjustment state of the two focus detection area. Adjusting device. The focus adjustment device according to claim 3,
When the focus adjustment control is performed using the focus adjustment states of the first focus detection area and the second focus detection area, the control unit uses the first threshold value to determine whether the defocus amount is reliable. When the focus adjustment control is performed based on the focus adjustment state of the first focus detection area selected by the selection unit, the focus adjustment of the first focus detection area and the second focus detection area is performed. Whether or not the defocus amount is reliable is determined using a second threshold value smaller than the first threshold value so that it is less likely to be determined that the focus adjustment control is performed using the state. A focusing device characterized by that. The focus adjustment device according to any one of claims 1 to 4,
A first light receiving unit that receives a light beam corresponding to the first focus detection area and outputs a first light reception signal, and a second light receiving unit that receives a light beam corresponding to the second focus detection area and outputs a second light reception signal. A line sensor having
The focus adjustment device, wherein the focus adjustment unit detects a focus adjustment state using at least one of the first light reception signal and the second light reception signal. The focus adjustment device according to claim 5, comprising:
The first focus detection area and the second focus detection area are provided along a predetermined direction,
The focus adjusting apparatus, wherein the first light receiving unit and the second light receiving unit are provided along the predetermined direction. The focus adjustment device according to claim 6, comprising:
A plurality of the first focus detection areas are provided along the predetermined direction;
The focus adjusting apparatus, wherein a plurality of the first light receiving units are provided along the predetermined direction. A focus adjustment device according to any one of claims 1 to 7,
An imaging apparatus comprising: an imaging unit that captures an image by the optical system.

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