JP4612869B2 - Focus detection device, imaging device, and focusing method - Google Patents

Description

  The present invention relates to an imaging device, and more particularly, to an imaging device having a focus detection device that detects a focus state of an imaging optical system.

  Conventionally, a focus detection apparatus using a TTL (Through The Lens) phase difference method has been used to detect the focus state of an imaging lens of an imaging apparatus typified by a digital camera or a video camera. The TTL phase difference method divides the pupil of a photographing lens into a pair of regions, and detects the relative position change of a pair of images formed by a light beam passing through the divided pupil region, thereby focusing the imaging lens. Detect state.

  FIG. 7 is a schematic cross-sectional view showing a configuration of a conventional focus detection apparatus 1000. In FIG. 7, the field lens 1010 images the exit pupil of the imaging lens IL on the pupil plane of the pair of secondary imaging lenses 1020. Thereby, the light beam incident on the secondary imaging lens 1020 is emitted from regions of different positions having the same area on the exit pupil of the imaging lens IL. The secondary imaging lens 1020 re-images the aerial image formed by the imaging lens IL in the vicinity of the field lens 1010 on a pair of light receiving elements (photoelectric conversion elements) 1030.

  FIG. 8 is a diagram for explaining a relative position change of an image formed on the light receiving element 1030. FIG. 8A shows the case where the imaging lens IL is in focus (that is, the imaging point of the imaging lens IL is on the planned imaging plane), and FIG. If there is (that is, the imaging point of the imaging lens IL is in front of the planned imaging plane), FIG. 8C shows that the imaging lens IL is the rear pin (that is, the imaging point of the imaging lens IL is scheduled). This shows a case where the image forming surface is in the subsequent stage. In FIGS. 8B and 8C, the relative positions of the images are moved in the opposite directions with respect to the focused imaging position in FIG. 8A. That is, the direction of defocus and the amount of defocus (the amount of defocus) of the imaging lens IL are detected by detecting the moving direction of the relatively moving image and the amount of deviation of the relative position with reference to the imaging position in the focused state. ) Can be detected.

  An imaging lens generally includes aberrations such as chromatic aberration. If the wavelength of light is different, the imaging position of an aerial image formed near the field lens changes. Therefore, the imaging lens is configured to correct various aberrations in the visible light region of 400 nm to 700 nm. However, since the light receiving element for focus detection is generally a PN junction type photodiode having sensitivity from the visible light region to the near infrared region, the above-described focus detection device detects an accurate focus state. I can't. In the infrared light region, the chromatic aberration of the imaging lens is not corrected well, so the subject is illuminated with sunlight, the subject is illuminated with a light source with a low color temperature such as a tungsten lamp, or a fluorescent lamp, etc. Because the relative ratio of near-infrared light to visible light is different from when illuminating with a light source with a high color temperature, the position of the aerial image formed near the field lens changes. is there. Therefore, it is necessary to determine the light source that illuminates the subject and correct the focus detection error according to the determined light source. Although it is conceivable to use a focus detection light-receiving element having no sensitivity in the near-infrared region, a high-power near-infrared LED is used as an auxiliary light source for focus detection. The sensitivity of the light receiving element for use is preferably up to the near infrared region.

  In order to determine the light source, an image sensor that separates and detects the color of the light source is required. As for color detection by an image sensor, a method of separating and extracting colors using a color filter such as RGB is conventionally known. Patent Document 1 proposes an image sensor that can separate and detect the three primary colors RGB. The imaging device of Patent Document 1 uses the characteristics of silicon that has different depths of absorption depending on the wavelength of light, and extracts signals of each of the three primary colors from different depths of pixels at the same position using a triple well structure. be able to.

  FIG. 9 is a schematic cross-sectional view showing a configuration of an image sensor (light receiving element) 2000 proposed in Patent Document 1. In FIG. The image sensor 2000 has a triple structure, and is configured to extract light with a desired wavelength by forming a plurality of pn junctions in the depth direction. The image sensor 2000 includes a p-type semiconductor substrate 2100, a first coupling region 2200, a second coupling region 2300, and a third coupling region 2400.

  The first coupling region 2200 is an n-type well region formed on the p-type semiconductor substrate 2100, and has a depth to absorb light having a red wavelength (that is, the coupling depth is 1.5 μm to 3. 0 μm). The second coupling region 2300 is a p-type well region formed in the first coupling region 2200, and has a depth to absorb light having a green wavelength (that is, the coupling depth is 0.5 μm to 1 μm). .5 μm). The third coupling region 2400 is an n-type well region formed in the second coupling region 2300, and has a depth to absorb blue light (that is, the coupling depth is 0.2 μm to 0.5 μm). ).

  Ir represents a current generated from the first coupling region 2200, and is a photocurrent generated by absorbing light having a red wavelength. Ig represents a current generated from the second coupling region 2300, and is a photocurrent generated by absorbing light having a green wavelength. Ib indicates a current generated from the third coupling region 2400, and is a photocurrent generated by absorbing light having a blue wavelength.

  FIG. 10 is a graph showing the spectral sensitivity characteristics of the image sensor 2000. Referring to FIG. 10, the image sensor 2000 is not sharply color-separated as compared with the case where color separation is performed using an RGB color filter, but has different spectral sensitivity characteristics. It can be seen that the primary colors are separated.

  Further, a focus detection device that corrects a focus detection error due to the influence of an infrared light component of a light source using a detection element (light receiving element) having a structure similar to that of Patent Document 1 has been proposed (for example, Patent Document 2). reference.). FIG. 11 is a schematic perspective view showing the configuration of the focus detection device 3000 disclosed in Patent Document 2. As shown in FIG. The focus detection device 3000 includes an optical path dividing prism 3100, a substrate 3200, a first light receiving element array 3300, a second light receiving element array 3400, and a detection element 3500 for detecting the spectral characteristics of the light source. Have. The first light receiving element array 3300 and the second light receiving element array 3400 are arranged before and after the planned imaging plane of the imaging lens, that is, so that the in-focus state can be detected, so as to have different optical path lengths. The

  FIG. 12 is a schematic cross-sectional view showing the configuration of the detection element 3500. The detection element 3500 has a three-layer structure of silicon, and is formed of a first P region 3510, an N region 3520, and a second P region 3530. A first electrode 3512, a second electrode 3522, and a third electrode 3532 are provided in each region. As described above, silicon absorbs short-wavelength light in the vicinity of the surface and absorbs long-wavelength light in a deep portion. Accordingly, the first diode formed by the first P region 3510 and the N region 3520 has a peak sensitivity to light on the short wavelength side, and the first diode formed by the N region 3520 and the second P region 3530 is formed. The diode 2 has a sensitivity peak in light on the long wavelength side. FIG. 13 is a graph showing the spectral sensitivity characteristics of the detection element 3500, specifically, the relative sensitivity characteristics of the first diode and the second diode. The focus detection device 3000 uses the output ratio of two diodes having different sensitivity characteristics as shown in FIG. 13 to correct a focus detection error due to a difference in spectral characteristics of the light source (that is, the influence of the infrared light component). be able to.

As another technique, a solid-state imaging device having a multilayer (stacked) structure capable of detecting light other than RGB, for example, infrared light (IR) and ultraviolet light (UV) has also been proposed (for example, patents). Reference 3).
JP-T-2002-513145 Japanese Examined Patent Publication No. 1-45883 JP 2004-221506 A

  The image sensor disclosed in Patent Document 1 is a sensor for capturing a color image, and prevents generation of a false color signal without using a low-pass filter by taking out three primary colors from pixels at the same position. It becomes possible. However, Patent Document 1 does not describe any application such as discriminating a light source from signals of three primary colors, detecting a change in the focus detection state of the imaging optical system, and using it for correcting such a change. Moreover, although the solid-state image sensor currently disclosed by patent document 3 can detect infrared light, without using IR filter, about patent document 1, about utilizing this detection result for focus detection. Is not listed.

  Patent Document 2 describes that a spectral sensitivity characteristic of a light source is detected and a focus detection result is corrected according to the detected spectral sensitivity characteristic. However, as shown in FIG. 11, the detection element for detecting the light source (the spectral characteristic thereof) and the first and second light receiving element arrays for detecting the focus state are arranged at different positions, so that parallax occurs. The position where the subject is observed is strictly different. In the case where a plurality of light sources having different color temperatures are mixed, for example, in the case where the subject is illuminated indoors by a fluorescent lamp and there is an outdoor scene behind the back, the parallax between the detection element and the light receiving element array In addition, images illuminated with light sources having different color temperatures are captured in the respective elements. Therefore, the type of the light source actually incident on the detection element is erroneously detected, and the focus detection result cannot be corrected well (for example, the focus detection result is overcorrected or corrected in the reverse direction). Etc.) will occur. Such a problem cannot be prevented unless the parallax between the element that detects the light source (its spectral characteristics) and the element that detects the focus state is completely eliminated.

  Accordingly, an object of the present invention is to provide a focus detection apparatus and an imaging apparatus that can detect the focus state of the imaging optical system with high accuracy in response to light (light source) from a subject.

In order to achieve the above object, a focus detection apparatus according to one aspect of the present invention includes a light receiving element that divides a light beam from an imaging lens to form at least a pair of images and photoelectrically converts the at least a pair of images. And a focus detection device that detects a focus state of the imaging lens based on a signal from the light receiving element, wherein the light receiving element is sensitive to light in the first wavelength region in a depth direction at the same position. And a second light receiving region sensitive to light in a second wavelength region different from the first wavelength region, and a signal from the first light receiving region is predetermined. When the value is equal to or greater than the value, the focus state of the imaging lens is detected based on a signal from the first light receiving region.
A focus detection apparatus according to another aspect of the present invention includes a light receiving element that divides a light beam from an imaging lens to form at least a pair of images, and photoelectrically converts the at least pair of images. A focus detection device that detects a focus state of the imaging lens based on a signal, wherein the light receiving element is a first light receiving region having sensitivity to light in a first wavelength region in a depth direction at the same position. And a second light receiving region that is sensitive to light in a second wavelength region different from the first wavelength region, and a signal from the first light receiving region is a predetermined value or less, The focus state of the imaging lens is detected according to the ratio of the signal from the first light receiving area and the signal from the second light receiving area.
According to still another aspect of the present invention, a focus detection apparatus includes a light receiving element that divides a light flux from an imaging lens to form at least a pair of images, and photoelectrically converts the at least pair of images. The focus detection device detects the focus state of the imaging lens based on the signal of the first lens, wherein the light receiving element is sensitive to light in the first wavelength region in the same direction in the depth direction. And a second light receiving region sensitive to light in a second wavelength region different from the first wavelength region, and the subject is irradiated with auxiliary light for ensuring the brightness of the subject In this case, the focus state of the imaging lens is detected based on a signal from the second light receiving region.

Focusing method according to another aspect of the present invention divides the light beam from the imaging lens to form at least a pair of images, the a light receiving element for converting at least photoelectrically pair of images, the same position depth In the vertical direction, a first light receiving region having sensitivity to light in the first wavelength region and a second light receiving region having sensitivity to light in a second wavelength region different from the first wavelength region are provided. A focusing method that uses a light receiving element to focus a focus state of the imaging lens, and when a signal from the first light receiving area is equal to or greater than a predetermined value , and having a step of detecting the focus state of the imaging lens based on the signal, the step of driving the imaging lens according to the focus state.
A focusing method according to still another aspect of the present invention is a light receiving element that divides a light beam from an imaging lens to form at least a pair of images and photoelectrically converts the at least a pair of images, and has a depth at the same position. In the vertical direction, a first light receiving region having sensitivity to light in the first wavelength region and a second light receiving region having sensitivity to light in a second wavelength region different from the first wavelength region are provided. A focusing method that uses a light receiving element to focus a focus state of the imaging lens, and when a signal from the first light receiving region is equal to or less than a predetermined value, Detecting a focus state of the imaging lens based on a ratio between a signal and a signal from the second light receiving region, and driving the imaging lens in accordance with the focus state. .
A focusing method according to still another aspect of the present invention is a light receiving element that divides a light beam from an imaging lens to form at least a pair of images and photoelectrically converts the at least a pair of images, and has a depth at the same position. In the vertical direction, a first light receiving region having sensitivity to light in the first wavelength region and a second light receiving region having sensitivity to light in a second wavelength region different from the first wavelength region are provided. A focusing method for focusing a focus state of the imaging lens by using a light receiving element, wherein the second light receiving region is obtained when auxiliary light for ensuring the brightness of the subject is irradiated to the subject. And a step of detecting a focus state of the imaging lens based on a signal from the camera and a step of driving the imaging lens in accordance with the focus state.

  Further objects and other features of the present invention will become apparent from the preferred embodiments described below with reference to the accompanying drawings.

  ADVANTAGE OF THE INVENTION According to this invention, the focus detection apparatus and imaging device which can detect the focus state of an imaging optical system with high precision corresponding to the light (light source) from a to-be-photographed object can be provided.

  Hereinafter, an imaging apparatus according to an aspect of the present invention will be described with reference to the accompanying drawings. In addition, in each figure, the same reference number is attached | subjected about the same member and the overlapping description is abbreviate | omitted. FIG. 1 is a schematic cross-sectional view showing a configuration of an imaging apparatus 1 according to the present invention.

  The imaging apparatus 1 is an imaging apparatus that images light from a subject on an imaging element via an imaging lens and captures the subject. In this embodiment, the imaging apparatus 1 is embodied as a digital still camera.

  As shown in FIG. 1, the imaging device 1 includes an imaging lens 10, a main mirror 20, a finder optical system 30, a sub mirror 40, an imaging device 50, a focus detection device 60, auxiliary light means 70, and control. Part 80. The main mirror 20, the finder optical system 30, the sub mirror 40, the image sensor 50, the focus detection device 60, the auxiliary light means 70, and the control unit 80 constitute a camera body, and the image pickup lens 10 is connected via a mount unit (not shown). Detachable. Therefore, the imaging lens 10 is not necessarily a component of the imaging device 1.

  The imaging lens 10 is an interchangeable imaging lens for imaging a subject, and includes an imaging optical system including a focus adjustment lens. The focus (state) of the imaging lens 10 is adjusted by the control unit 80 described later via the focus adjustment lens.

  The main mirror 20 is composed of a semi-transparent mirror, reflects a part of the light transmitted through the imaging lens 10 and guides it to a focusing plate 32 described later, and a part of the light transmitted through the imaging lens 10. And is guided to a sub mirror 40 described later. The main mirror 20 is configured such that it can be inserted into and removed from the imaging optical path, and is disposed at a predetermined position on the imaging optical path during viewfinder observation, and retracts out of the imaging optical path during imaging.

  The viewfinder optical system 30 is an optical system for observing a subject to be imaged. In the present embodiment, the viewfinder optical system 30 includes a focusing screen 32, a pentaprism 34, and an eyepiece lens 36. In other words, the finder optical system 30 provides the user with a pseudo image of the subject to be captured.

  The focusing screen 32 diffuses the light (subject image) from the imaging lens 10 reflected by the main mirror 20 and emits it to the pentaprism 34. The pentaprism 34 includes two reflecting surfaces of 45 degrees with each other and two refracting surfaces perpendicular to the incident light and the emitted light. The pentaprism 34 reflects the light diffused by the focusing screen 32 and guides it to the eyepiece lens 36. The eyepiece 36 is also called an eyepiece, and has a function of finally connecting an image in the finder optical system 30. The eyepiece 36 enlarges the optical image, for example.

  The sub mirror 40 reflects the light transmitted through the main mirror 20 and guides it to the focus detection device 60. The sub mirror 40 is configured so as to be able to be inserted into and removed from the imaging optical path. The sub mirror 40 is disposed at a predetermined position on the imaging optical path during finder observation, and retracts outside the imaging optical path during imaging.

  The image sensor 50 has regularly arranged pixels, and has a function of receiving light from a subject imaged by the imaging lens 10 and converting it into an image signal (photoelectric conversion). The image sensor 50 is configured by, for example, an area (two-dimensional) sensor that converts received light into an electrical signal for each pixel, accumulates charges corresponding to the amount of received light, and reads the charges. The image sensor 50 is configured by a CMOS sensor or a CCD. The output signal from the image sensor 50 is subjected to predetermined processing in an image processing circuit (not shown) to become image data, and the image data is recorded on a recording medium such as a semiconductor memory, an optical disk, and a magnetic tape (not shown). The

  The focus detection device 60 detects the focus state of the imaging lens 10 using a TTL phase difference method. Specifically, the focus detection device 60 divides the light flux from the imaging lens 10 reflected by the sub-mirror 40 to form at least a pair of images, and based on signals obtained by photoelectrically converting the pair of images. The focus state of the imaging lens 10 is detected. In this embodiment, the focus detection device 60 includes a field lens, a secondary imaging lens, and a light receiving element 600 described later with reference to FIGS. 2 and 3. The field lens and the secondary imaging lens have the same functions and operations as those of the field lens and the secondary imaging lens shown in FIG. 7, and thus detailed description thereof is omitted here.

  FIG. 2 is a schematic block diagram showing the entire light receiving element 600 of the focus detection device 60. The light receiving element 600 has a function of photoelectrically converting a pair of images formed by the feel lens and the secondary imaging lens. In FIG. 2, reference numeral 610 denotes an AF linear circuit block. An AF linear circuit block 610, a photodiode array, and a signal processing circuit are included, and an A image portion 612 and a B image portion 614 are provided.

  The A image unit 612 includes a pair of visible light photodiode arrays and a photoelectric conversion circuit, and the B image unit 614 includes a pair of infrared light photodiode arrays and a photoelectric conversion circuit. It has a configuration used for phase difference passive autofocus. As shown in FIGS. 9 and 12, the photodiodes used in the A image portion 612 and the B image portion 614 have a plurality of PN junctions in the depth direction at the same position, and output light in different wavelength regions. Can be taken out. Therefore, there is no parallax between the visible light photodiode array and the infrared light photodiode array, and the position where light is detected (received) is the same. As a result, even when there are a plurality of types of light sources that illuminate the subject (that is, wavelengths of light that illuminate the subject), the types of light sources can be detected without being confused by background light or the like.

  In the present embodiment, the A image portion 612 and the B image portion 614 use the same photodiodes as those in FIG. 12, and the A image visible portion 612a and the B image visible portion 614a (first image) having sensitivity in the visible light region, respectively. Light receiving region), and an A image IR portion 612b and a B image IR portion 614b (second light receiving region) having sensitivity in the infrared light region. Further, the A image visible portion 612a, the B image visible portion 614a, the A image IR (infrared) portion 612b, and the B image IR portion 614b respectively store a photodiode and a photodiode that receive reflected light from an object. It consists of an amplifier that converts charges into voltage.

  In a phase difference type focus detection apparatus, reflected light from a subject is imaged on a photodiode by a pair of light receiving optical systems having parallax, and the distance (focal point) to the subject from the amount of deviation of the image. Alternatively, the defocus amount of the imaging lens 10 can be detected. The focus detection device 60 of this embodiment can detect the defocus amount for each of the visible light region and the infrared light region.

  Reference numeral 620 denotes an analog circuit block, which is based on an image signal from the AF linear circuit block 610, an AGC (auto gain control) circuit 621 for controlling the accumulation time of a visible light photodiode, and an infrared light photodiode. An AGC (auto gain control) circuit 622 that controls the accumulation time, a signal amplification circuit 623 that amplifies the image signals of the visible part and the IR part from the AF linear circuit block 610 at a predetermined amplification rate, and outputs them to the outside; The signal processing circuit of the linear circuit block 610 includes a reference voltage generation circuit 624 for supplying a bias voltage and various clamp voltages, and an intermediate voltage generation circuit 625.

  Reference numeral 630 denotes a digital circuit block, an I / O circuit 632 for connection to a control unit (microcomputer) 80 for controlling the light receiving element 610, and a TG (timing generator) for generating driving timing of the AF linear circuit block 610. Circuit 634.

  FIG. 3 is a block diagram showing the AF linear circuit block 610 in detail. In FIG. 3, only the visible portions 612a and 614a of the A image portion 612 and the B image portion 614 are illustrated. Since the IR units 612b and 614b have the same configuration as the visible units 612a and 614a, illustration and description thereof are omitted. In the present embodiment, the A image portion 612a is a reference portion, and the B image portion 614a is a reference portion.

Image portion 612a and the B-image portion 614a (AF linear circuit block 610A) includes a photodiode 612a ₁ and 614a ₁ of visible light for receiving reflected light from an object, the charges accumulated in the photodiode 612a ₁ and 614a ₁ a photoelectric conversion amplifier array 612a ₂ and 614a ₂ receives, receives the output of the photoelectric amplifier array 612a ₂ and 614a _2, noise removal for removing fixed pattern noise contained in the output of the photoelectric amplifier array 612a ₂ and 614a ₂ (FPN) Arrays 612 a ₃ and 614 a ₃ , maximum value detection circuit arrays 612 a ₄ and 614 a ₄ for detecting the maximum value of the image signal and outputting the maximum value output to the AGC circuit 621, and output of the image signal to the signal amplification circuit 623 Signal output circuit arrays 612a ₅ and 614a ₅ to The signal output circuit arrays 612a ₅ and 614a ₅ are configured by shift registers 612a ₆ and 614a ₆ for sequentially outputting the outputs of the signal output circuit arrays 612a ₅ and 614a ₅ to the signal amplifier circuit 323.

  Returning to FIG. 1, the auxiliary light means 70 has a function of projecting auxiliary light onto the subject and ensuring the brightness of the subject when the subject is insufficiently bright at the time of imaging. In the present embodiment, the auxiliary light means 70 is composed of a near-infrared LED having a large power.

  The control unit 80 controls the focus adjustment lens included in the imaging lens 10 based on the defocus direction and defocus amount of the imaging lens 10 detected by the focus detection device 60 and adjusts the focus of the imaging lens 10. Specifically, as will be described later, the control unit 80 calculates the driving amount of the focus adjustment lens based on the defocus direction and the defocus amount of the imaging lens 10, and the calculation result on the imaging lens side is not illustrated. To the department. The imaging lens side control unit drives the focus adjustment lens via a motor or the like based on the drive amount of the focus adjustment lens from the control unit 80.

  In the present embodiment, the control unit 80 controls the focus detection device 60. For example, as will be described later, the control unit 80 controls the focus detection operation of the focus detection device 60 and determines the focus state of the imaging lens 10 based on the focus states of the plurality of imaging lenses 10 acquired by the focus detection device 60. Determination means for determining, calculation means for calculating the driving amount of the focus adjustment lens, the ratio of the signals from the visible portions 612a and 614a of the light receiving element 600 and the signals from the IR portions 612b and 614b, and the like based on the focus state Function. In the present embodiment, the control unit 80 is provided in the imaging device 1, but may be provided in the focus detection device 60 independently of functions necessary for the focus detection operation described below.

  Here, the focus detection operation of the focus detection device 60 (control of the focus detection device 60 by the control unit 80) will be described with reference to FIG. FIG. 4 is a flowchart for explaining focus detection by the focus detection device 60.

  Referring to FIG. 4, the accumulation operation of light receiving element 610 shown in FIG. 2 is started (step 901). In the present embodiment, first, it is determined whether or not the accumulation operation of the visible parts 612a and 614a has been completed (step 902). If the accumulation operations of the visible parts 612a and 614a are completed, the accumulation time is recorded (step 903) and the image signal is read (step 907).

  Next, it is determined whether reading of the image signals of the visible portions 612a and 614a and the IR (infrared) portions 612b and 614b has been completed (step 908). If reading of the image signals of the IR units 612b and 614b has not been completed, it is determined whether or not the accumulation operation of the IR units 612b and 614b has been completed (step 904), as in step 902. If the accumulation operations of the IR units 612b and 614b have been completed, the accumulation time is recorded (step 903) and the image signal is read (step 907). On the other hand, if the accumulation operation of the IR units 612b and 614b has not ended, it is determined whether or not a predetermined time has elapsed since the accumulation operation of the light receiving element 610 was started (step 905). If the predetermined time has not elapsed, the accumulation operation of the light receiving element 610 is continued and the process returns to step 902. If the predetermined time has elapsed, the accumulation operation of the light receiving element 610 is forcibly stopped (step 906).

  When the reading of the image signals of the visible parts 612a and 614a and the IR (infrared) parts 612b and 614b is completed, based on the accumulation time recorded in step 903 and the image signal (output) read in step 907. Then, the respective signal amounts of the visible parts 612a and 614a and the IR parts 612b and 614b are calculated (step 909). For the signal amount, an output voltage converted into a predetermined accumulation time is calculated.

  Next, the predetermined determination voltage V0 is compared with the signal amounts of the visible portions 612a and 614a converted into a predetermined accumulation time (step 910). For example, the determination voltage V0 is set to an output voltage obtained with the brightness of EV14. Such brightness is set higher than that obtained with an artificial light source such as a fluorescent lamp. Therefore, it can be determined whether or not the accumulation operation is performed under sunlight.

  If the signal amounts of the visible portions 612a and 614a calculated in step 909 are larger than the predetermined determination voltage V0 (in this embodiment, if it is determined that the accumulation operation is performed under sunlight), the visible portions 612a and A known correlation calculation is performed from the image signal output of 614a, and the defocus direction and defocus amount (focus information) are calculated (step 911). Next, reliability is determined from the calculated signal amount of focus information, contrast, the degree of coincidence between the two visual fields, and the like (step 912). If the reliability is NG, it is determined that focus detection has failed (step 913), and the focus detection operation is terminated. On the other hand, when the reliability is OK, from the defocus amount and the defocus amount calculated in step 911, the optimal amount of focus adjustment lens extension (in the present embodiment, under sunlight) (driving amount). ) And the direction are calculated (step 914), and the focus detection operation is terminated.

  If the signal amounts of the visible portions 612a and 614a calculated in step 909 are smaller than the predetermined determination voltage V0, the defocus direction and defocus amount (focus information) are calculated from the image signal outputs of the visible portions 612a and 614a. Along with (Step 915), the direction of defocus and the amount of defocus (focus information) are calculated from the image signal outputs of the IR units 612b and 614b (Step 916). Next, the reliability is determined from the respective focus states of the visible portions 612a and 614a and the IR portions 612b and 614b (step 917). Such determination of reliability branches to three processes described below.

  First, when the reliability of the visible parts 612a and 614a is OK and the reliability of the IR parts 612b and 614b is NG, the parallax between the visible parts 612a and 614a and the IR parts 612b and 614b is completely the same. Therefore, it can be determined that the outputs of the IR units 612b and 614b have not reached a predetermined amount. Therefore, it can be determined as a light source such as a fluorescent lamp that hardly contains infrared light, and is optimal under a fluorescent lamp based on the defocus direction and defocus amount obtained from the visible parts 612a and 614a. The amount (drive amount) and direction of the focus adjustment lens so as to obtain a correct focus position are calculated (step 918), and the focus detection operation is terminated.

  When the reliability of the visible parts 612a and 614a is OK and the reliability of the IR parts 612b and 614b is OK, for example, a light source including a predetermined amount of infrared light, for example, a tungsten lamp is considered. The extension amount (drive amount) and direction of the focus adjustment lens are calculated from the units 612a and 614a and the IR units 612b and 614b, respectively (step 919). Next, the ratio between the signal amounts from the visible portions 612a and 614a and the signal amounts from the IR portions 612b and 614b is calculated, and the amount of extension of the focus adjustment lens calculated in step 919 is corrected based on the ratio (step 920). For example, if the ratio between the signal amount from the visible portions 612a and 614a and the signal amount from the IR portions 612b and 614b is 1: 1, it is calculated from the visible portions 612a and 614a and the IR portions 612b and 614b, respectively. Assuming that an actual focal point exists in the middle of the focal point, the extension amount of the focus adjustment lens is corrected. Specifically, as shown in FIG. 5, when the horizontal axis represents the color temperature of the light source and the vertical axis represents the focal position, the focal positions from the visible parts 612a and 614a and the IR parts 612b and 614b are determined according to the color temperature of the light source. The calculation result changes. For example, when the color temperature of the light source is low, that is, when the infrared light component increases, the calculation result indicates a front pin. Further, the error in the calculation result between the visible portions 612a and 614a and the IR portions 612b and 614b becomes larger as the color temperature is lower. Therefore, the driving amount of the focus adjustment lens calculated in step 919 can be corrected by Δ = α × δ. Here, Δ is a correction amount for correcting the driving amount of the focus adjustment lens, δ is a difference between the calculation results of the visible portions 612a and 614a and the calculation results of the IR portions 612b and 614b, and α varies depending on the chromatic aberration of the imaging lens 10. Value. Further, although it is possible to estimate the color temperature from the difference δ of the focus calculation results, it can also be estimated from the ratio P between the signal amounts from the visible portions 612a and 614a and the signal amounts from the IR portions 612b and 614b. Is possible. That is, it is presumed that the color temperature is higher as the value of P is smaller and the color temperature is lower as it is larger. Therefore, when the value of P is small, the correction of the extension amount of the focus adjustment lens is small, and when the value of P is large, the correction of the extension amount of the focus adjustment lens is increased.

  When the reliability of the visible parts 612a and 614a is NG and the reliability of the IR parts 612b and 614b is NG, focus detection using auxiliary light (step 921) is performed as described later.

  Hereinafter, the focus detection operation using the auxiliary light will be described with reference to FIG. FIG. 6 is a flowchart for explaining focus detection by auxiliary light in step 920 of FIG. First, the auxiliary light means 70 is used to project auxiliary light toward the subject (step 941), and the accumulation operation of the light receiving element 610 is started (step 942). At this time, since focus detection is performed using auxiliary light, only the IR units 612b and 614b need be accumulated.

  Next, it is determined whether or not the accumulation operation of the IR units 612b and 614b has been completed (step 943). If the accumulation operations of the IR units 612b and 614b have been completed, the accumulation time is recorded (step 944) and the image signal is read (step 945). On the other hand, if the accumulation operation of the IR units 612b and 614b is not completed, it is determined whether or not a predetermined time has elapsed since the accumulation operation was started (step 946). If the predetermined time has not elapsed, the accumulation operation is continued and the process returns to step 943. If the predetermined time has elapsed, the accumulation operation is forcibly stopped (step 947).

  When reading of the image signals of the IR units 612b and 614b is completed, the signal amounts of the IR units 612b and 614b are calculated based on the accumulation time recorded in step 944 and the image signal (output) read out in step 945. (Step 948). For the signal amount, an output voltage converted into a predetermined accumulation time is calculated.

  Next, a known correlation calculation is performed from the image signal outputs of the IR units 612b and 614b, and the defocus direction and defocus amount (focus information) are calculated (step 949). Further, reliability is determined from the calculated signal amount of focus information, contrast, and the degree of coincidence between the two fields of view (step 950). If the reliability is NG, it is determined that focus detection has failed (step 951), and the focus detection operation is terminated. On the other hand, when the reliability is OK, the optimal amount of extension (drive amount) and direction of the focus adjustment lens under the auxiliary light are calculated from the defocus direction and defocus amount calculated in step 949 (step 940). 952), the focus detection operation is terminated.

  As described above, the focus detection using the focus detection device 60 and the focus detection device 60 according to the present embodiment detects light signals having different wavelengths in the depth direction at the same position, thereby detecting focus information in different wavelength regions and Each luminance can be discriminated (detected). By correcting the focus information based on the detection result, the focus position can be accurately detected even when the types of light sources or a plurality of types of light sources are mixed. In addition, focus detection becomes impossible due to insufficient brightness and contrast of the subject, and even in the case where the focus is detected by projecting auxiliary light, the output in the depth direction suitable for the wavelength range of the auxiliary light to be used can be obtained. By detecting, the focus can be detected without being affected by light outside the wavelength region of the auxiliary light.

  The operation of the imaging apparatus 1 will be described. During viewfinder observation, the light transmitted through the imaging lens 10 is reflected by the main mirror 20, forms an image on the focusing screen 32, and is observed through the pentaprism 34 and the eyepiece lens 36. The light transmitted through the main mirror 20 is reflected by the sub mirror 40 and enters the focus detection device 60. As described above, the focus detection device 60 forms a pair or a plurality of pairs of images on the light receiving element 610 and detects the focus state of the imaging lens 10. Based on the detection result, the control unit 80 and the imaging lens side control unit (not shown) drive the focus lens included in the imaging lens 10 to obtain a focused state.

  On the other hand, at the time of imaging (when the recording image is acquired), the main mirror 20 and the sub mirror 40 are retracted from the imaging optical path, and the subject image formed by the imaging lens 10 is captured by the imaging element 50. The imaging device 1 detects the focus of the imaging lens 10 with high accuracy even when a plurality of light sources are mixed by the focus detection device 60, and based on the detection result, the focus of the imaging lens 10 is detected. Since they can be combined, a high-quality image can be taken.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist. For example, in the present embodiment, light in the visible region and light in the infrared region are detected based on outputs from two different depths, but outputs of three or more different wavelength regions such as RGB may be used. Good. In addition, focus detection using auxiliary light is not limited to light having a near-infrared wavelength, and a photodiode having optimum wavelength characteristics is appropriately formed according to the wavelength of auxiliary light selected. do it.

It is a schematic sectional drawing which shows the structure of the imaging device as 1 side surface of this invention. It is a schematic block diagram which shows the whole light receiving element of the focus detection apparatus shown in FIG. FIG. 3 is a block diagram showing in detail an AF linear circuit block shown in FIG. 2. It is a flowchart for demonstrating the focus detection by the focus detection apparatus shown in FIG. It is a figure for demonstrating correction | amendment of the drive amount of a focus adjustment lens. It is a flowchart for demonstrating the focus detection by the auxiliary light of step 920 of FIG. It is a schematic sectional drawing which shows the structure of the conventional focus detection apparatus. It is a figure for demonstrating the relative position change of the image imaged on the image pick-up element shown in FIG. It is a schematic sectional drawing which shows the structure of the conventional image pick-up element. It is a graph which shows the spectral sensitivity characteristic of the image pick-up element shown in FIG. It is a schematic perspective view which shows the structure of the conventional focus detection apparatus. It is a schematic sectional drawing which shows the structure of the detection element shown in FIG. It is a graph which shows the spectral sensitivity characteristic of the detection element shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging device 10 Imaging lens 50 Imaging device 60 Focus detection device 70 Auxiliary light means 80 Control part 610 AF linear circuit block 612 A image part 612a A image visible part 612b A image IR part 614 B image part 614a B image visible part 614b B Image IR unit 620 Analog circuit block 621 AGC circuit 622 AGC circuit 623 Signal amplification circuit 624 Reference voltage generation circuit 625 Intermediate voltage generation circuit 630 Digital circuit block 632 I / O circuit 634 TG circuit

Claims (8)

A light-receiving element that divides the light flux from the imaging lens to form at least a pair of images and photoelectrically converts the at least one pair of images, and detects a focus state of the imaging lens based on a signal from the light-receiving element A focus detection device,
The light receiving element is sensitive to light in a first wavelength region that is sensitive to light in a first wavelength region and light in a second wavelength region that is different from the first wavelength region in the depth direction at the same position. A second light receiving region having
If prior SL signal from the first light receiving area is equal to or larger than the predetermined value, the first focus and detects the focus state of the imaging lens based on a signal from the light receiving regions point detecting device . A light-receiving element that divides the light flux from the imaging lens to form at least a pair of images and photoelectrically converts the at least one pair of images, and detects a focus state of the imaging lens based on a signal from the light-receiving element A focus detection device,
The light receiving element is sensitive to light in a first wavelength region that is sensitive to light in a first wavelength region and light in a second wavelength region that is different from the first wavelength region in the depth direction at the same position. A second light receiving region having
If prior SL signal from the first light receiving area is equal to or less than the predetermined value, the focus state of the imaging lens according to the ratio between the signal from the signal and the second light receiving region from the first light receiving region you and detecting a focal point detection apparatus.   A light-receiving element that divides the light flux from the imaging lens to form at least a pair of images and photoelectrically converts the at least one pair of images, and detects a focus state of the imaging lens based on a signal from the light-receiving element A focus detection device,
  The light receiving element is sensitive to light in a first wavelength region that is sensitive to light in a first wavelength region and light in a second wavelength region that is different from the first wavelength region in the depth direction at the same position. A second light receiving region having
  A focus detection device that detects a focus state of the imaging lens based on a signal from the second light receiving region when auxiliary light for ensuring the brightness of the subject is irradiated on the subject. .   The first wavelength region is a visible light region;
  The focus detection apparatus according to claim 1, wherein the second wavelength region is an infrared light region.   An imaging device that captures a subject image via an imaging lens,
  The focus detection apparatus according to any one of claims 1 to 4,
  An image sensor that captures the subject image and outputs an image signal;
  An image pickup apparatus comprising: a recording control unit that controls the recording unit to record the image signal.   A light receiving element that divides a light flux from an imaging lens to form at least a pair of images and photoelectrically converts the at least a pair of images, and is sensitive to light in a first wavelength region in a depth direction at the same position. The focus state of the imaging lens is determined by using a light receiving element having a first light receiving region having a second light receiving region sensitive to light in a second wavelength region different from the first wavelength region. A focusing method for focusing,
  Detecting a focus state of the imaging lens based on a signal from the first light receiving area when a signal from the first light receiving area is equal to or greater than a predetermined value;
  And a step of driving the imaging lens in accordance with the focus state.   A light receiving element that divides a light flux from an imaging lens to form at least a pair of images and photoelectrically converts the at least a pair of images, and is sensitive to light in a first wavelength region in a depth direction at the same position. The focus state of the imaging lens is determined by using a light receiving element having a first light receiving region having a second light receiving region sensitive to light in a second wavelength region different from the first wavelength region. A focusing method for focusing,
  When the signal from the first light receiving area is equal to or less than a predetermined value, the focus state of the imaging lens is determined based on the ratio between the signal from the first light receiving area and the signal from the second light receiving area. Detecting step;
  And a step of driving the imaging lens in accordance with the focus state.   A light receiving element that divides a light flux from an imaging lens to form at least a pair of images and photoelectrically converts the at least a pair of images, and is sensitive to light in a first wavelength region in a depth direction at the same position. The focus state of the imaging lens is determined by using a light receiving element having a first light receiving region having a second light receiving region sensitive to light in a second wavelength region different from the first wavelength region. A focusing method for focusing,
  Detecting a focus state of the imaging lens based on a signal from the second light receiving region when auxiliary light for ensuring the brightness of the subject is irradiated on the subject;
  And a step of driving the imaging lens in accordance with the focus state.