JP6459165B2 - Focus detection device - Google Patents

Description

The present invention relates to a focus detection apparatus .

  Conventionally, a camera capable of capturing a visible light image and an infrared light image is known. For example, Patent Document 1 describes a camera that can use the “composite AF function” by operating an operation unit. The “composite AF function” of Patent Document 1 is a function of analyzing a subject image based on infrared light to determine a focus detection region and performing focus detection based on visible light.

JP 2010-62742 A

  The prior art has a problem that the desired subject is not always in focus.

The focus detection apparatus according to claim 1 is a focus detection apparatus that is used in an imaging apparatus and performs focus detection of a subject on which a pattern that reflects invisible light is formed, and the invisible light that has passed through a photographing optical system. A first photoelectric conversion unit that photoelectrically converts the first photoelectric conversion signal, a second photoelectric conversion unit that photoelectrically converts visible light that has passed through the photographing optical system and outputs a second photoelectric conversion signal, and the first photoelectric conversion unit. An imaging device in which a photoelectric conversion unit and the second photoelectric conversion unit are stacked, a first focus detection unit that detects a focus adjustment state based on the first photoelectric conversion signal, and a focus based on the second photoelectric conversion signal using a second focus detection unit for detecting modulation states, a detecting unit for detecting a pattern from the first photoelectric conversion signals, at least one of the detection result of said second focus detection unit and the first focus detection unit The focus of the photographic optical system And a focus adjustment unit that performs regulation.

  According to the present invention, it is possible to accurately focus on a desired subject.

It is a figure which illustrates the structure of the digital camera 1 by the 1st Embodiment of this invention. It is a figure which shows the outline | summary of the image pick-up element 21 which concerns on this embodiment. 3 is a diagram illustrating a pixel arrangement of an upper photoelectric conversion layer 31 and a lower photoelectric conversion layer 32. FIG. 2 is a diagram illustrating a part of a cross section of an image sensor 21. FIG. 3 is a diagram illustrating a circuit configuration of one pixel P (x, y) in the image sensor 21. FIG. It is a figure which shows an example of the pattern formed in the marker surface. 4 is a flowchart of an automatic focus adjustment process executed by a control unit 11. It is a figure which illustrates the structure of the digital camera 2 by the 2nd Embodiment of this invention. 5 is a flowchart of an automatic focus adjustment process executed by a control unit 111. It is a figure which illustrates the structure of the digital camera 3 by the 3rd Embodiment of this invention. It is a figure which shows the determination method of weight (alpha) by the calculating part 211g. 5 is a flowchart of an automatic focus adjustment process executed by a control unit 211.

(First embodiment)
FIG. 1 is a diagram illustrating the configuration of a digital camera 1 according to the first embodiment of the invention. The digital camera 1 includes a photographing optical system 10, a control unit 11, an imaging unit 12, an operation unit 13, an image processing unit 14, a liquid crystal monitor 15, and a buffer memory 16. In addition, a memory card 17 is attached to the digital camera 1.

  The photographic optical system 10 includes a plurality of lenses, and forms a subject image on an imaging surface of an imaging element 21 (described later). The plurality of lenses constituting the photographing optical system 10 include a focus lens that is driven in the optical axis direction in order to adjust the focus position. The focus lens is driven in the optical axis direction by an actuator (not shown) (for example, an ultrasonic motor).

  The control unit 11 includes a microprocessor and its peripheral circuits, and performs various controls of the digital camera 1 by executing a control program stored in a ROM (not shown). The control unit 11 functionally includes a focus adjustment unit 11a, a marker detection unit 11b, a marker selection unit 11c, and a priority order reading unit 11d. Each of these functional units is implemented in software by the control program described above. Each of these functional units can also be configured by an electronic circuit.

  The focus adjusting unit 11a adjusts the focus of the photographing optical system 10 based on an image signal output from an image sensor 21 (described later). The marker detection unit 11b detects a marker described later based on the infrared light component of the subject image formed by the photographing optical system 10. When the marker detection unit 11b detects a plurality of markers to be described later, the marker selection unit 11c selects any one of the plurality of markers. The priority order reading unit 11d reads the priority order of the subject to which the marker is attached from the markers described later.

  The imaging unit 12 includes an imaging device 21, an amplification circuit 22, and an AD conversion circuit 23. The image sensor 21 is composed of a plurality of pixels, receives a light beam from a subject via a photographing optical system (not shown), performs photoelectric conversion, and outputs an analog image signal. The amplifier circuit 22 amplifies the analog image signal output from the image sensor 21 with a predetermined amplification factor (gain) and outputs the amplified signal to the AD conversion circuit 23. The AD conversion circuit 23 performs AD conversion on the analog image signal and outputs a digital image signal. The control unit 11 stores the digital image signal output from the imaging unit 12 in the buffer memory 16.

  The digital image signal stored in the buffer memory 16 is subjected to various image processing in the image processing unit 14 and displayed on the liquid crystal monitor 15 or stored in the memory card 17. The memory card 17 is composed of a non-volatile flash memory or the like and is detachable from the digital camera 1.

  The operation unit 13 includes various operation buttons such as a release button, a mode switching button, and a power button, and is operated by a photographer. The operation unit 13 outputs an operation signal corresponding to the operation of each operation button by the photographer to the control unit 11. The image processing unit 14 is configured by an ASIC or the like. The image processing unit 14 performs various types of image processing such as interpolation, compression, and white balance on the image data captured by the imaging unit 12.

(Description of the image sensor 21)
FIG. 2 is a diagram showing an outline of the image sensor 21 according to the present embodiment. 2 shows a state in which the light incident side of the image sensor 21 is the upper side. Therefore, in the following description, the direction on the light incident side of the image sensor 21 is “upper” or “upper”, and the direction opposite to the light incident side is “lower” or “lower”. The image sensor 21 includes an upper photoelectric conversion layer 31 and a lower photoelectric conversion layer 32. The upper photoelectric conversion layer 31 and the lower photoelectric conversion layer 32 are stacked on the same optical path. The upper photoelectric conversion layer 31 is composed of an organic photoelectric film that absorbs (photoelectric conversion) light in a predetermined wavelength range (details will be described later). Light in a wavelength region that has not been absorbed (photoelectric conversion) by the upper photoelectric conversion layer 31 passes through the upper photoelectric conversion layer 31 and enters the lower photoelectric conversion layer 32, and is photoelectrically converted by the lower photoelectric conversion layer 32. The lower photoelectric conversion layer 32 performs photoelectric conversion using a photodiode.

  The upper photoelectric conversion layer 31 photoelectrically converts invisible light (for example, infrared light). The lower photoelectric conversion layer 32 photoelectrically converts visible light. The upper photoelectric conversion layer 31 and the lower photoelectric conversion layer 32 are formed on the same semiconductor substrate, and each pixel position corresponds to one to one. For example, the pixel in the first row and the first column of the upper photoelectric conversion layer 31 corresponds to the pixel in the first row and the first column of the lower photoelectric conversion layer 32.

  FIG. 3A is a diagram illustrating a pixel arrangement of the upper photoelectric conversion layer 31. In FIG. 3A, the horizontal direction is the x-axis, the vertical direction is the y-axis, and the coordinates of the pixel P are expressed as P (x, y). In the example of the upper photoelectric conversion layer 31 shown in FIG. 3A, each pixel is an organic photoelectric film that photoelectrically converts invisible light (infrared light). Then, light that is not received by each pixel, that is, visible light is transmitted. For example, the pixel P (1, 1) photoelectrically converts infrared light (IR) and transmits visible light.

  FIG. 3B is a diagram illustrating a pixel arrangement of the lower photoelectric conversion layer 32. Each pixel position shown in FIG. 3B is the same as that in FIG. For example, the pixel P (1, 1) of the lower photoelectric conversion layer 32 corresponds to the pixel P (1, 1) of the upper photoelectric conversion layer 31. In FIG. 3B, the lower photoelectric conversion layer 32 is provided with three color filters of red (R), green (G), and blue (B) in a so-called Bayer arrangement. Visible light that passes through the upper photoelectric conversion layer 31 (that is, light in a wavelength region other than invisible light that is absorbed and photoelectrically converted by the organic photoelectric film of the upper photoelectric conversion layer 31) is photoelectrically converted. Therefore, the lower photoelectric conversion layer 32 outputs an image signal of G and B color components for pixels in odd rows, and an image signal of R and G color components for each pixel in even rows. For example, a G component image signal is obtained at the pixel P (1, 1). Similarly, a B component image signal is obtained from the pixel P (2, 1), and an R component image signal is obtained from the pixel P (1, 2).

  Thus, in the imaging device 21 according to the present embodiment, the upper photoelectric conversion layer 31 formed of an organic photoelectric film serves as an infrared filter with respect to the lower photoelectric conversion layer 32. In the imaging device 21 according to the present embodiment, an image of an object by infrared light (infrared light image) can be acquired from the upper photoelectric conversion layer 31, and an image of the object by visible light from the lower photoelectric conversion layer 32. (RGB image composed of three colors of R, G, and B) can be acquired. In the following description, an image signal output from the upper photoelectric conversion layer 31 is referred to as an infrared light signal. The image signal output from the lower photoelectric conversion layer 32 is referred to as a visible light signal.

  FIG. 4 is a diagram illustrating a part of a cross section of the image sensor 21. As shown in FIG. 4, in the imaging element 21, a lower photoelectric conversion layer 32 formed on a silicon substrate and an upper photoelectric conversion layer 31 using an organic photoelectric film are stacked via a wiring layer 40. Above the upper photoelectric conversion layer 31, one microlens ML is formed for one pixel. Between the upper photoelectric conversion layer 31 and the lower photoelectric conversion layer 32, one color filter CF is formed for one pixel. For example, in the upper photoelectric conversion layer 31, the light receiving part PC (1,1) by the organic photoelectric film that constitutes the photoelectric conversion part of the pixel P (1,1) is the subject incident from the microlens ML (1,1). Visible light is transmitted by photoelectrically converting infrared light in the light. Of the visible light transmitted through the light receiving unit PC (1, 1), the G component transmits through the color filter CF (1, 1), and the R component and B component are shielded by the color filter CF (1, 1). In the lower photoelectric conversion layer 32, the photodiode PD (1, 1) constituting the pixel P (1, 1) receives and photoelectrically converts the G light transmitted through the color filter CF (1, 1).

  FIG. 5 is a diagram illustrating a circuit configuration of one pixel P (x, y) in the image sensor 21. The pixel P (x, y) includes a photodiode PD, a transfer transistor Tx, a reset transistor R2, an output transistor SF2, and a selection transistor SEL2 as a circuit for configuring the lower photoelectric conversion layer 32. The photodiode PD accumulates charges according to the amount of incident light. The transfer transistor Tx transfers the charge accumulated in the photodiode PD to the floating diffusion region (FD portion) on the output transistor SF2 side. The output transistor SF2 constitutes a current source PW2 and a source follower via the selection transistor SEL2, and outputs an electric signal corresponding to the electric charge accumulated in the FD section as an output signal OUT2 to the vertical signal line VLINE2. The reset transistor R2 resets the charge in the FD portion to the power supply voltage Vcc.

  Further, the pixel P (x, y) includes a light receiving unit PC using an organic photoelectric film, a reset transistor R1, an output transistor SF1, and a selection transistor SEL1 as a circuit for configuring the upper photoelectric conversion layer 31. The light receiving unit PC using an organic photoelectric film converts non-transmitted light into an electrical signal corresponding to the amount of light, and outputs a vertical signal line as an output signal OUT1 via a selection transistor SEL1 and an output transistor SF1 constituting a source follower. Output to VLINE1. The reset transistor R1 resets the output signal of the light receiving unit PC to the reference voltage Vref. Further, a high voltage Vpc is applied for the operation of the organic photoelectric film. Each transistor is composed of a MOSFET.

  Here, the operation of the circuit according to the lower photoelectric conversion layer 32 will be described. First, when the selection signal φSEL2 becomes “High”, the selection transistor SEL2 is turned on. Next, when the reset signal φR2 becomes “High”, the FD section resets the power supply voltage Vcc, and the output signal OUT2 also becomes a reset level. Then, after the reset signal φR2 becomes “Low”, the transfer signal φTx becomes “High”, the charge accumulated in the photodiode PD is transferred to the FD portion, and the output signal OUT2 changes according to the amount of charge. Start and stabilize. Then, the transfer signal φTx becomes “Low”, and the signal level of the output signal OUT2 read from the pixel to the vertical signal line VLINE2 is determined. The output signal OUT2 of each pixel read out to the vertical signal line VLINE2 is temporarily held for each row in a horizontal output circuit (not shown) and then output from the image sensor 21. In this way, a signal is read from each pixel of the lower photoelectric conversion layer 32 of the image sensor 21.

  The operation of the circuit relating to the upper photoelectric conversion layer 31 will be described. First, when the selection signal φSEL1 becomes “High”, the selection transistor SEL1 is turned on. Next, the reset signal φR1 becomes “High”, and the output signal OUT1 also becomes the reset level. Then, immediately after the reset signal φR1 becomes “Low”, the charge accumulation of the light receiving unit PC by the organic photoelectric film is started, and the output signal OUT1 changes according to the amount of charge. The output signal OUT1 is temporarily held for each row in a horizontal output circuit (not shown), and then output from the image sensor 21. In this way, a signal is read from each pixel of the upper photoelectric conversion layer 31 of the image sensor 21.

(Description of automatic focus adjustment process)
When the photographer performs a predetermined focus adjustment operation (for example, an operation of pressing the release button halfway), the control unit 11 executes a so-called contrast type automatic focus adjustment process. Briefly explaining the contrast type auto-focus adjustment process, a subject lens is picked up periodically while the focus lens is driven, the amount of contrast of the subject image at each position of the focus lens is examined, and the focus lens that maximizes the contrast amount This position is specified as the in-focus position.

  The focus adjustment unit 11a included in the control unit 11 can perform a contrast-type automatic focus adjustment process based on a visible light signal, that is, a subject image by visible light. When the photographer performs a focus adjustment operation, the control unit 11 causes the marker detection unit 11b to detect a marker described later. The focus adjustment unit 11a sets a focus detection area in the shooting screen according to the marker detection result. The focus adjustment unit 11a performs focus adjustment by calculating a focus evaluation value in the set focus detection area from the visible light signal.

(Description of marker)
The digital camera 1 of the present embodiment can perform focus adjustment using a marker. The marker has a predetermined pattern formed on the surface, and is affixed to the subject surface as a seal, for example, or printed on the subject surface. This pattern is formed to transmit visible light and reflect infrared light. That is, even if this marker is imaged by the lower photoelectric conversion layer 32, the above pattern does not appear in the visible light signal. On the other hand, when the upper photoelectric conversion layer 31 captures an image, the above pattern appears in the infrared light signal.

  FIG. 6 is a diagram illustrating an example of a pattern formed on the marker surface. A pattern 81 is formed on the surface of the marker 80. The marker 80 is formed of a material that transmits infrared light or visible light. The pattern 81 is formed of a material that transmits visible light and reflects infrared light with a constant reflectance.

  The pattern 81 has two roles. First, the pattern 81 is encoded with a numerical value representing a priority order in automatic focus adjustment of a subject (for example, a person, a building, etc.) to which this pattern is attached. This numerical value indicates, for example, that the higher the priority, the higher the priority of the subject. The priority order reading unit 11d decodes the pattern 81 detected by the marker detection unit 11b, and reads a numerical value representing the priority order.

  Next, the pattern 81 has a shape advantageous for focus detection. Specifically, the shape has features such as high contrast, clear edges, and low periodicity. The pattern 81 having such a characteristic has characteristics that are advantageous for focus detection, such as being able to detect contrast with a certain degree of reliability even when the focus is greatly deviated, and preventing false focusing. Have

  As described above, the pattern 81 included in the marker 80 has both a role of holding information related to the priority order of subjects and a role of assisting focus adjustment. When using the digital camera 1, the user previously forms a marker 80 on clothes, accessories, a building surface, or the like of a person to be focused. The marker detection unit 11b detects the pattern 81 from the infrared light signal by a method such as pattern matching. When one or more patterns 81 are detected, the priority order reading unit 11d reads the priority order of the subject to which the pattern 81 is attached from each of the patterns 81. The marker selection unit 11c selects the marker 80 having the highest priority read. The focus adjustment unit 11a performs automatic focus adjustment by setting a focus detection region at the position of the selected marker 80.

  For example, if the marker 80 is formed on the surface of the contact lens, it is possible to easily focus on the face of the person wearing the contact lens. In addition, if the marker 80 is formed on the signboard of the outdoor advertisement, the signboard can be easily focused. Since the marker 80 is formed of a material that transmits visible light, the marker 80 does not hinder the function of the contact lens and the visibility of the posted content of the outdoor advertisement.

  FIG. 7 is a flowchart of the automatic focus adjustment process executed by the control unit 11. The automatic focus adjustment process shown in FIG. 7 is included in a control program executed by the control unit 11. First, in step S100, the image sensor 21 captures a subject image. Thereby, a visible light signal is output from the upper photoelectric conversion layer 31 and an infrared light signal is output from the lower photoelectric conversion layer 32. In step S110, the marker detection unit 11b attempts to detect the marker 80 from the infrared light signal output by the imaging in step S100. In step S120, the control unit 11 determines whether or not the marker detection unit 11b has successfully detected at least one marker 80 in step S110.

  If no marker 80 is detected in step S120, the control unit 11 advances the process to step S170. On the other hand, when at least one marker 80 is detected, the control unit 11 advances the process to step S140. In step S140, the priority order reading unit 11d reads the priority order represented by the pattern of the marker 80 from the one or more markers 80 detected in step S110. In step S150, the marker selection unit 11c selects one marker 80 to be focused based on the priority order read in step S140. Specifically, the marker 80 with the highest priority is selected as a focus target. In step S160, the focus adjustment unit 11a sets a focus detection region at the position of the marker 80 selected in step S150. The focus detection area is set, for example, with the center of the marker 80 as the center position, and the size may be larger or smaller than the marker 80. In step S170, the focus adjustment unit 11a calculates a focus evaluation value (contrast value) in the focus detection region from the visible light signal output by the imaging in step S100. In step S180, the focus adjustment unit 11a drives the focus lens by a predetermined amount in a predetermined direction.

  The control part 11 performs the process shown in FIG. 7 periodically (for example, every 1/60 second). Thereby, a focus evaluation value corresponding to each position of the focus lens is obtained. Thereafter, the focus adjusting unit 11a drives the focus lens to the position of the focus lens where the focus evaluation value is maximized, that is, the focus position, and focuses on the target subject.

According to the digital camera according to the first embodiment described above, the following operational effects can be obtained.
(1) The upper photoelectric conversion layer 31 (first photoelectric conversion means) photoelectrically converts invisible light that has passed through the photographing optical system 10 and outputs an infrared light signal (first photoelectric conversion signal). The marker detection unit 11bb detects a marker 80 having a pattern 81 that reflects an invisible light beam and set in advance on the surface of the subject by detecting the pattern 81 from the infrared light signal. The focus adjusting unit 11a adjusts the focus of the photographing optical system 10 so that the subject on which the marker 80 is installed is focused. Since this is done, the desired subject can be accurately focused.

(2) The marker selection unit 11c selects any one of the plurality of markers 80 when the marker detection unit 11b detects the plurality of markers 80 installed on each of the plurality of subjects. When a plurality of markers 80 are detected by the marker detection unit 11b, the focus adjustment unit 11a performs focus adjustment so that the subject on which the marker 80 selected by the marker selection unit 11c is placed is in focus. Since it did in this way, even if it is a case where there are many subjects, it can focus on a desired subject exactly.

(3) The priority order reading unit 11d reads information related to the priority order of the subject specified by the marker 80 from each marker 80 detected by the marker detection unit 11b. The marker selection unit 11c selects the marker 80 from which the highest priority is read by the priority reading unit 11d as a focus target. Since it did in this way, even if it is a case where there are many subjects, it can focus on a desired subject exactly.

(4) The digital camera 1 includes the image sensor 21 in which an upper photoelectric conversion layer 31 and a lower photoelectric conversion layer 32 are stacked. The upper photoelectric conversion layer 31 transmits visible light, and the lower photoelectric conversion layer 32 photoelectrically converts visible light transmitted through the upper photoelectric conversion layer 31. Since it did in this way, an infrared-light cut filter can be abbreviate | omitted and the manufacturing cost of the digital camera 1 can be reduced. Further, the digital camera 1 can be downsized as compared with the case where two imaging elements for visible light and infrared light are mounted.

(Second Embodiment)
The digital camera 2 according to the second embodiment of the present invention will be described below. In the following description, differences from the digital camera 1 according to the first embodiment will be mainly described, and the same parts as those in the first embodiment are the same as those in the first embodiment. Reference numerals are assigned and description is omitted.

  FIG. 8 is a diagram illustrating the configuration of the digital camera 2 according to the second embodiment of the invention. The digital camera 2 has a configuration in which the control unit 11 of the digital camera 1 according to the first embodiment is replaced with a control unit 111. The control unit 111 has a configuration in which the focus adjustment unit 11a of the control unit 11 is replaced with a focus adjustment unit 111a, and a first focus detection unit 111e and a second focus detection unit 111f are further added.

  The first focus detection unit 111e performs focus detection based on the infrared light signal output from the upper photoelectric conversion layer 31. The second focus detection unit 111f performs focus detection based on the visible light signal output by the lower photoelectric conversion layer 32.

  The focus adjustment unit 11 a according to the first embodiment performs focus adjustment using the visible light signal output from the lower photoelectric conversion layer 32. On the other hand, the focus adjustment unit 111a according to the present embodiment uses one of the infrared light signal output from the upper photoelectric conversion layer 31 and the infrared light signal output from the lower photoelectric conversion layer 32 to focus. Make adjustments. The focus adjustment unit 111a determines which image signal to use according to the detection result of the marker 80 by the marker detection unit 11b.

  When the marker 80 is detected, the focus adjustment unit 111a uses the focus evaluation value detected from the infrared light signal by the first focus detection unit 111e. On the other hand, when the marker 80 is not detected, the focus evaluation value detected from the visible light signal by the second focus detection unit 111f is used. This is because the pattern 81 of the marker 80 has a shape advantageous for focus detection. Although it may be difficult to detect the contrast depending on the subject, the marker 80 always has a pattern 81 having a shape that can advantageously perform focus detection. Therefore, when the marker 80 is detected, the marker 80 is targeted. However, focus detection can be performed stably.

  FIG. 9 is a flowchart of an automatic focus adjustment process executed by the control unit 111. The automatic focus adjustment process shown in FIG. 9 is included in a control program executed by the control unit 111. First, in step S200, the image sensor 21 captures a subject image. Thereby, a visible light signal is output from the upper photoelectric conversion layer 31 and an infrared light signal is output from the lower photoelectric conversion layer 32. In step S210, the marker detection unit 11b attempts to detect the marker 80 from the infrared light signal output by the imaging in step S200. In step S220, the control unit 111 determines whether the marker detection unit 11b has successfully detected at least one marker 80 in step S210.

  If no marker 80 is detected in step S220, the controller 111 advances the process to step S230. In step S230, the second focus detection unit 111f performs focus detection from the visible light signal output by the imaging in step S200. That is, the focus evaluation value in the focus detection area is calculated. On the other hand, when at least one marker 80 is detected in step S220, the control unit 111 advances the process to step S240.

  In step S240, the priority order reading unit 11d reads the priority order represented by the pattern of the marker 80 from the one or more markers 80 detected in step S210. In step S250, the marker selection unit 11c selects one marker 80 to be focused based on the priority order read in step S240. Specifically, the marker 80 with the highest priority is selected as a focus target. In step S260, the focus adjustment unit 111a sets a focus detection region at the position of the marker 80 selected in step S250. In step S270, the first focus detection unit 111e performs focus detection from the infrared light signal output by the imaging in step S200. That is, the focus evaluation value in the focus detection area is calculated. In step S280, the focus adjustment unit 111a drives the focus lens by a predetermined amount in a predetermined direction.

  The control part 111 performs the process shown in FIG. 9 periodically (for example, every 1/60 second). Thereby, a focus evaluation value corresponding to each position of the focus lens is obtained. Thereafter, the focus adjusting unit 111a drives the focus lens to the position of the focus lens where the focus evaluation value is maximized, that is, the focus position, and focuses on the target subject.

According to the digital camera according to the second embodiment described above, the following operational effects can be obtained.
(1) The upper photoelectric conversion layer 31 (first photoelectric conversion means) photoelectrically converts invisible light that has passed through the photographing optical system 10 and outputs an infrared light signal (first photoelectric conversion signal). The marker detection unit 11b detects a marker 80 that has a pattern 81 that reflects invisible light and is previously set on the surface of the subject by detecting the pattern 81 from the infrared light signal. The focus adjustment unit 111a adjusts the focus of the photographing optical system 10 so that the subject on which the marker 80 is installed is focused. Since this is done, the desired subject can be accurately focused.

(2) The marker selection unit 11c selects any one of the plurality of markers 80 when the marker detection unit 11b detects the plurality of markers 80 installed on each of the plurality of subjects. When a plurality of markers 80 are detected by the marker detection unit 11b, the focus adjustment unit 111a performs focus adjustment so that the subject on which the marker 80 selected by the marker selection unit 11c is placed is in focus. Since it did in this way, even if it is a case where there are many subjects, it can focus on a desired subject exactly.

(3) The priority order reading unit 11d reads information related to the priority order of the subject specified by the marker 80 from each marker 80 detected by the marker detection unit 11b. The marker selection unit 11c selects the marker 80 from which the highest priority is read by the priority reading unit 11d as a focus target. Since it did in this way, even if it is a case where there are many subjects, it can focus on a desired subject exactly.

(4) The lower photoelectric conversion layer 32 (second photoelectric conversion means) photoelectrically converts visible light that has passed through the photographing optical system 10 and outputs a visible light signal (second photoelectric conversion signal). The first focus detection unit 111e performs focus detection based on the infrared light signal (first photoelectric conversion signal). The second focus detection unit 111f performs focus detection based on the visible light signal. The focus adjustment unit 111a performs focus adjustment of the photographing optical system 10 using at least one of the first focus detection unit 111e and the second focus detection unit 111f. As described above, since the infrared light signal and the visible light signal are selectively used, it is possible to perform focus adjustment with higher accuracy than in the case where focus adjustment is performed using only one image signal.

(5) When the marker 80 is detected by the marker detection unit 11b, the focus adjustment unit 111a adjusts the focus of the photographing optical system 10 using the focus detection result by the first focus detection unit 111e, and the marker detection unit 11b. When the marker 80 is not detected by the above, the focus adjustment of the photographing optical system 10 is performed using the focus detection result by the second focus detection unit 111f. As described above, since the infrared light signal and the visible light signal are selectively used, it is possible to perform focus adjustment with higher accuracy than in the case where focus adjustment is performed using only one image signal.

(6) The digital camera 2 includes the imaging device 21 in which an upper photoelectric conversion layer 31 and a lower photoelectric conversion layer 32 are stacked. The upper photoelectric conversion layer 31 transmits visible light, and the lower photoelectric conversion layer 32 photoelectrically converts visible light transmitted through the upper photoelectric conversion layer 31. Since it did in this way, an infrared-light cut filter can be abbreviate | omitted and the manufacturing cost of the digital camera 1 can be reduced. In addition, the digital camera 2 can be downsized compared to the case where two imaging elements for visible light and infrared light are mounted.

(Third embodiment)
Hereinafter, a digital camera 3 according to a third embodiment of the present invention will be described. In the following description, differences from the digital camera 1 according to the first embodiment will be mainly described, and the same parts as those in the first embodiment are the same as those in the first embodiment. Reference numerals are assigned and description is omitted.

  FIG. 10 is a diagram illustrating the configuration of the digital camera 3 according to the third embodiment of the invention. The digital camera 3 has a configuration in which the control unit 11 of the digital camera 1 according to the first embodiment is replaced with a control unit 211. The control unit 211 has a configuration in which the focus adjustment unit 11a of the control unit 11 is replaced with a focus adjustment unit 211a, and a first focus detection unit 111e, a second focus detection unit 111f, a calculation unit 211g, and a photometry unit 211h are added.

  The photometry unit 211 h measures the amount of light incident on the photographing optical system 10 from the subject based on the visible light signal output by the lower photoelectric conversion layer 32. For example, the amount of light from the subject is measured by adding the pixel outputs from the pixels of the lower photoelectric conversion layer 32 together. In addition to the lower photoelectric conversion layer 32, an illuminance sensor that detects the amount of light of the subject may be provided, and the amount of light may be measured using the output of the illuminance sensor.

  The calculation unit 211g calculates a weighted average of the focus detection result by the first focus detection unit 111e and the focus detection result by the second focus detection unit 111f based on the detection result of the marker 80 by the marker detection unit 11b.

  The focus adjustment unit 11 a according to the first embodiment performs focus adjustment using the visible light signal output from the lower photoelectric conversion layer 32. On the other hand, the focus adjustment unit 211a according to the present embodiment uses the marker detection unit 11b to generate the infrared light signal output from the upper photoelectric conversion layer 31 and the infrared light signal output from the lower photoelectric conversion layer 32. It is used for focus adjustment in combination according to the detection result of the marker 80.

The calculating unit 211g is a third weighting unit that weights the first in-focus position calculated by the first focus detecting unit 111e and the second in-focus position calculated by the second focus detecting unit 111f by the following equation (1). A focus position is generated.
C = α × A + (1−α) × B (1)

  Here, C is a third focus position, A is a first focus position specified from the first focus evaluation value, and B is a focus position specified from the second focus evaluation value. α is a weight and takes a value of 0 to 1. The larger α is, the greater the influence of infrared light at the third in-focus position, and the smaller α is, the greater the influence of visible light at the third in-focus position.

  FIG. 11 is a diagram illustrating a method of determining the weight α by the calculation unit 211g. The calculation unit 211g determines the value of the weight α based on the detection result of the marker 80 by the marker detection unit 11b and the light amount of the subject measured by the photometry unit 211h.

  When calculating the third in-focus position, the calculation unit 211g first determines whether or not the marker 80 is detected by the marker detection unit 11b. If the marker 80 has been detected, the subject light quantity is applied to the marker usage coefficient graph shown in FIG. 11A to determine the weight α. On the other hand, when the marker 80 is not detected, the subject light quantity is applied to the marker nonuse coefficient graph shown in FIG.

  The marker usage coefficient graph shown in FIG. 11A is configured to weight the first in-focus position more heavily than the marker non-use coefficient graph shown in FIG. This is because the marker 80 having the pattern 81 having a shape advantageous for focus detection is utilized by focus adjustment.

  In addition, the marker usage coefficient graph shown in FIG. 11A is configured so that the first in-focus position is heavily weighted in the case of low illuminance, and the second in-focus position is heavily weighted in the case of high illuminance. Yes. This is because infrared light tends to have a larger light quantity than visible light even in a low illuminance environment.

  In the marker nonuse coefficient graph shown in FIG. 11B, as in the marker use coefficient graph shown in FIG. 11A, the first in-focus position is heavily weighted in the case of low illuminance, and in the case of high illuminance. Is configured to heavily weight the second in-focus position. On the other hand, the marker nonuse coefficient graph shown in FIG. 11B is configured so that the weight of the first in-focus position becomes smaller under medium illuminance than the marker use coefficient graph shown in FIG. Has been. This is because the marker 80 does not exist, and it is not necessary to actively use infrared light unless the illumination is low.

  FIG. 12 is a flowchart of the automatic focus adjustment process executed by the control unit 211. The automatic focus adjustment process illustrated in FIG. 12 is included in a control program executed by the control unit 211. First, in step S300, the image sensor 21 captures a subject image. Thereby, a visible light signal is output from the upper photoelectric conversion layer 31 and an infrared light signal is output from the lower photoelectric conversion layer 32. In step S305, the photometry unit 211h measures the amount of light of the subject from the visible light signal output by the imaging in step S300.

  In step S310, the marker detection unit 11b attempts to detect the marker 80 from the infrared light signal output by the imaging in step S300. In step S320, the control unit 211 determines whether or not the marker detection unit 11b has successfully detected at least one marker 80 in step S310.

  If no marker 80 is detected in step S320, the control unit 211 advances the process to step S330. In step S330, the computing unit 211g applies the subject light amount measured in step S305 to the marker nonuse coefficient graph shown in FIG.

  On the other hand, when at least one marker 80 is detected in step S320, the control unit 211 advances the process to step S340. In step S340, the priority order reading unit 11d reads the priority order represented by the pattern of the marker 80 from the one or more markers 80 detected in step S310. In step S350, the marker selection unit 11c selects one marker 80 to be focused based on the priority order read in step S340. Specifically, the marker 80 with the highest priority is selected as a focus target. In step S360, the focus adjustment unit 211a sets a focus detection region at the position of the marker 80 selected in step S350. In step S370, the calculation unit 211g applies the subject light amount measured in step S305 to the marker usage coefficient graph shown in FIG.

  In step S372, the first focus detection unit 111e calculates a first focus evaluation value in the focus detection region from the infrared light signal output by the imaging in step S300. In step S374, the second focus detection unit 111f calculates a second focus evaluation value in the focus detection region from the visible light signal output by the imaging in step S300. In step S376, the control unit 211 determines whether the focus detection calculation is completed, that is, whether the maximum position of the first focus evaluation value and the maximum position of the second focus evaluation value are found. If the focus detection calculation has not been completed, the control unit 211 advances the process to step S380. In step S380, the focus adjustment unit 211a drives the focus lens by a predetermined amount in a predetermined direction. In step S381, the image sensor 21 captures a subject image. Thereafter, the process proceeds to step S372. On the other hand, when the focus detection calculation has been completed in step S376, the control unit 211 advances the process to step S382.

  In step S382, the first focus detection unit 111e identifies the first focus position, which is the position of the focus lens at which the first focus evaluation value is maximized, from the first focus evaluation values corresponding to the various focus lens positions. To do. Similarly, in step S384, the second focus detection unit 111f determines the second focus that is the position of the focus lens at which the second focus evaluation value is maximized from the second focus evaluation values corresponding to the positions of various focus lenses. Identify the location. Here, the shift of the imaging position between visible light and infrared light may be corrected. That is, when the focus lens is at the same position, a certain shift occurs in the imaging position between the visible light and the infrared light. Therefore, the specified second focus position may be shifted by this shift amount.

  In step S386, the calculation unit 211g calculates the first focus position specified in step S382, the second focus position specified in step S384, and the weight α determined in step S330 or step S370 using the above formula. Substituting into (1), the third in-focus position is calculated. In step S388, the focus adjusting unit 211a drives the focus lens to the third in-focus position calculated in step S386, and focuses on the target subject.

According to the digital camera according to the third embodiment described above, the following operational effects can be obtained.
(1) The upper photoelectric conversion layer 31 (first photoelectric conversion means) photoelectrically converts invisible light that has passed through the photographing optical system 10 and outputs an infrared light signal (first photoelectric conversion signal). The marker detection unit 11b detects a marker 80 that has a pattern 81 that reflects invisible light and is previously set on the surface of the subject by detecting the pattern 81 from the infrared light signal. The focus adjustment unit 211a adjusts the focus of the photographing optical system 10 so that the subject on which the marker 80 is installed is focused. Since this is done, the desired subject can be accurately focused.

(2) The marker selection unit 11c selects any one of the plurality of markers 80 when the plurality of markers 80 are detected by the marker detection unit 11b. When a plurality of markers 80 are detected by the marker detection unit 11b, the focus adjustment unit 211a performs focus adjustment so that the subject on which the marker 80 selected by the marker selection unit 11c is placed is in focus. Since it did in this way, even if it is a case where there are many subjects, it can focus on a desired subject exactly.

(3) The priority order reading unit 11d reads information related to the priority order of the subject specified by the marker 80 from each marker 80 detected by the marker detection unit 11b. The marker selection unit 11c selects the marker 80 from which the highest priority is read by the priority reading unit 11d as a focus target. Since it did in this way, even if it is a case where there are many subjects, it can focus on a desired subject exactly.

(4) The lower photoelectric conversion layer 32 (second photoelectric conversion means) photoelectrically converts visible light that has passed through the photographing optical system 10 and outputs a visible light signal (second photoelectric conversion signal). The first focus detection unit 111e performs focus detection based on the infrared light signal (first photoelectric conversion signal). The second focus detection unit 111f performs focus detection based on the visible light signal. The focus adjustment unit 211a performs focus adjustment of the photographing optical system 10 using at least one of the focus detection result by the first focus detection unit 111e and the focus detection result by the second focus detection unit 111f. As described above, since the infrared light signal and the visible light signal are selectively used, it is possible to perform focus adjustment with higher accuracy than in the case where focus adjustment is performed using only one image signal.

(5) The focus adjustment unit 211a adjusts the focus of the photographing optical system 10 by combining the first focus evaluation value and the second focus evaluation value based on the detection result of the marker 80 by the marker detection unit 11b. Since it did in this way, it becomes possible to perform highly accurate focus adjustment which combined infrared light and visible light.

(6) The computing unit 211g computes a third in-focus position that is a weighted average of the first in-focus position and the second in-focus position based on the detection result of the marker 80 by the marker detection unit 11b. The focus adjustment unit 211a adjusts the focus of the photographing optical system 10 based on the third focus position. Since it did in this way, it becomes possible to perform highly accurate focus adjustment which combined infrared light and visible light.

(7) The calculation unit 211g assigns a greater weight to the first in-focus position when the marker 80 is detected by the marker detection unit 11b than when the marker 80 is not detected by the marker detection unit 11b. To calculate the third in-focus position. Since it did in this way, it becomes possible to utilize the marker 80 as much as possible, and to perform a highly accurate focus adjustment.

(8) The photometry unit 211h measures the amount of light incident on the photographing optical system 10 from the subject. The calculation unit 211g calculates the third focus position by assigning a larger weight to the first focus position as the light amount measured by the photometry unit 211h is smaller. Since it did in this way, the precision of the focus adjustment in a dark environment improves.

(9) The digital camera 3 includes the imaging device 21 in which the upper photoelectric conversion layer 31 and the lower photoelectric conversion layer 32 are stacked. The upper photoelectric conversion layer 31 transmits visible light, and the lower photoelectric conversion layer 32 photoelectrically converts visible light transmitted through the upper photoelectric conversion layer 31. Since it did in this way, an infrared-light cut filter can be abbreviate | omitted and the manufacturing cost of the digital camera 1 can be reduced. In addition, the digital camera 3 can be downsized as compared with the case where two imaging elements for visible light and infrared light are mounted.

  The following modifications are also within the scope of the present invention, and one or a plurality of modifications can be combined with the above-described embodiment.

(Modification 1)
In the first embodiment, so-called contrast-type automatic focus adjustment control using visible light is performed, but other types of automatic focus adjustment control may be adopted. For example, automatic focus adjustment control using a so-called phase difference detection method for detecting a focus adjustment state from a phase difference between a pair of light beams that have passed through a pair of pupil regions of the photographing optical system 10 may be executed using visible light. Good. In addition, the above-described automatic focus adjustment control using the contrast method or the phase difference detection method can be executed using invisible light such as infrared light instead of visible light. Similarly, in the second and third embodiments, it is possible to use phase difference detection type automatic focus adjustment control.

(Modification 2)
The marker selection unit 11c may select the marker 80 to be focused based on information other than the priority order embedded in the marker 80. For example, when a plurality of markers 80 are detected, the marker 80 having the shortest distance from the digital camera, that is, the position closest to the digital camera may be selected.

(Modification 3)
The focus adjustment units 11a, 111a, and 211a may perform so-called subject tracking. For example, while the photographer maintains the release switch in the half-pressed state, the focus adjustment units 11a, 111a, and 211a repeatedly adjust the focus of the imaging optical system 10 with respect to the marker 80 according to the movement of the marker 80. It may be. In this way, it is possible to reliably track the same subject as compared to the conventional subject tracking.

(Modification 4)
In each of the above-described embodiments, the digital camera 1 using the imaging element 21 in which the upper photoelectric conversion layer 31 that photoelectrically converts infrared light and transmits visible light and the lower photoelectric conversion layer 32 that photoelectrically converts visible light are stacked. 2 and 3 have been described. The stacking order may be reversed. For example, an imaging element that photoelectrically converts visible light into the upper layer and transmits infrared light may be provided in the upper layer, and an imaging element that photoelectrically converts infrared light may be used in the lower layer. Two imaging elements may be used instead of the two photoelectric conversion layers. For example, subject light can be divided by a pellicle mirror or the like, and each of the divided subject light can be incident on these two image pickup devices.

(Modification 5)
The digital camera 1 may be provided with an infrared light irradiation device so that the subject is irradiated with infrared light when the marker detection unit 11b detects the marker. By doing in this way, the detection accuracy of a marker can be improved.

(Modification 6)
The shape of the marker 80, the content of information embedded in the pattern 81, the method of embedding information in the pattern 81, and the like are not limited to those exemplified in the above-described embodiment, and may be anything.

  Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other embodiments conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1, 2, 3 ... Digital camera 11, 111, 211 ... Control part, 11a, 111a, 211a ... Focus adjustment part, 11b ... Marker detection part, 11c ... Marker selection part, 11d ... Priority order reading part, 21 ... Imaging Element 31 ... Upper photoelectric conversion layer 32 ... Lower photoelectric conversion layer 111e ... First focus detection unit 111f ... Second focus detection unit 211g ... Calculation unit 211h ... Photometry unit

Claims (10)

A focus detection device that is used in an imaging device and performs focus detection of a subject on which a pattern that reflects invisible light is formed on a surface,
A first photoelectric conversion unit that photoelectrically converts invisible light that has passed through the imaging optical system and outputs a first photoelectric conversion signal;
A second photoelectric conversion unit that photoelectrically converts visible light that has passed through the imaging optical system and outputs a second photoelectric conversion signal;
An imaging device in which the first photoelectric conversion unit and the second photoelectric conversion unit are stacked;
A first focus detection unit that detects a focus adjustment state based on the first photoelectric conversion signal;
A second focus detector for detecting a focus adjustment state based on the second photoelectric conversion signal;
A detection unit for detecting the pattern from the first photoelectric conversion signal;
A focus adjustment unit that performs focus adjustment of the photographing optical system using a detection result of at least one of the first focus detection unit and the second focus detection unit;
A focus detection apparatus . The focus detection apparatus according to claim 1,
A selection unit that selects any one of the plurality of patterns when the detection unit detects a plurality of the patterns of each of the plurality of subjects;
The focus adjustment device, wherein the focus adjustment unit performs focus adjustment so that the subject having the one pattern selected by the selection unit is in focus when the detection unit detects the plurality of patterns. The focus detection apparatus according to claim 2,
A priority order reading unit that reads information on the priority order of the subject specified by the pattern from each of the patterns detected by the detection unit;
The focus detection apparatus , wherein the selection unit selects the pattern from which the highest priority is read by the priority reading unit. In the focus detection apparatus according to any one of claims 1 to 3,
When the pattern is detected by the detection unit, the focus adjustment unit adjusts the focus of the photographing optical system using the first focus detection unit, and the pattern is not detected by the detection unit. A focus detection device for adjusting the focus of the photographing optical system using the second focus detection unit. In the focus detection apparatus according to any one of claims 1 to 3,
The focus adjustment unit is configured to adjust the focus of the photographing optical system by combining the first focus detection unit and the second focus detection unit based on the detection result of the pattern by the detection unit . The focus detection apparatus according to claim 5,
A calculation unit that calculates a weighted average of the focus detection result by the first focus detection unit and the focus detection result by the second focus detection unit based on the detection result of the pattern by the detection unit;
The focus adjustment unit is a focus detection device that performs focus adjustment of the photographing optical system based on the weighted average calculated by the calculation unit . The focus detection apparatus according to claim 6,
The arithmetic unit assigns a greater weight to the focus detection result of the first focus detection unit when the pattern is detected by the detection unit than when the pattern is not detected by the detection unit. And a focus detection device for calculating the weighted average. In the focus detection apparatus according to claim 6 or 7,
A photometric unit that measures the amount of light incident on the photographing optical system from the subject,
The focus detection device that calculates the weighted average by assigning a larger weight to a focus detection result by the first focus detection unit as the light amount measured by the photometry unit is smaller. In the focus detection apparatus according to any one of claims 1 to 8,
The imaging device is a focus detection device in which the second photoelectric conversion unit is stacked on a light incident side of the first photoelectric conversion unit. In the focus detection apparatus according to any one of claims 1 to 8,
The imaging device is a focus detection device in which the first photoelectric conversion unit is stacked on a light incident side of the second photoelectric conversion unit.

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