JP2009198975A - Focus adjustment device and focus adjustment method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a focus adjustment device surely bringing an infinity object into focus even in a state where a conversion lens is attached when performing operation to bring the infinity object into focus by mechanically operating an operation member to the end of an operable range. <P>SOLUTION: When the conversion lens is attached, a focus lens position where the infinity object is brought into focus is shifted in a close-range direction by a maximum change amount of the focus lens position where the infinity object is brought into focus estimated from the production error of the conversion lens. When a photographer performs operation to bring the infinity object into focus by mechanically operating a focus adjustment lens to the end of a drive feasible range by manual operation, the drive target position of the focus lens is shifted from an infinity end position recorded in a table. Thus, the infinity object is brought into focus. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a focus adjustment device to which a conversion lens can be attached and a focus adjustment method thereof.

  Conventionally, an imaging apparatus described in Patent Literature 1 has been proposed for focus adjustment by manual operation when a conversion lens is attached.

  This imaging apparatus has first, second, and third lens systems. In this imaging apparatus, the third lens system moves for focusing in response to a focus jump command from the first sensor that detects the mounting state of the first lens system. If the focus jump command is issued again before this operation is completed, the stored proportionality coefficient is used in the arithmetic circuit to calculate the movement amount or the moved position of the third lens system.

Further, the third lens system is moved by a focus jump command while the manual focus mode is set. When the focus jump command is issued again after the movement and before the movement of the third lens system by the zoom operation occurs, similarly, the stored proportionality coefficient is used in the arithmetic circuit, The amount of movement of the lens system or the position after the movement is calculated.
Japanese Patent No. 2900962

  However, the conventional focus adjusting apparatus has the following problems. It is disclosed that the movement amount of the focus lens and the position after the movement are changed by mounting a conversion lens (hereinafter also referred to as a converter). However, when performing an operation to focus on an object at infinity by mechanically operating the operating member to the end of the operable range, the target position of the focus lens is affected by the manufacturing error of the converter, etc. It is not mentioned that it will be changed to avoid it.

  Therefore, when a conversion lens is attached and the photographer performs an operation to focus on an object at infinity by mechanically operating the focus adjustment lens to the end of the driveable range by manual operation, There is a problem that the image is greatly out of focus.

  The present invention provides a focus adjustment device capable of reliably focusing even when a conversion lens is mounted when performing an operation of focusing on an object at infinity by operating an operation member to an end of an operable range, and An object of the present invention is to provide a method for adjusting the focus.

  In order to achieve the above object, the focus adjustment apparatus of the present invention has an imaging unit that photoelectrically converts a subject image formed by a photographing optical system to obtain an electrical image signal, and is photoelectrically converted by the imaging unit. A focus adjustment lens for adjusting the focus of the subject image, an operation driving means for driving the focus adjustment lens by operating an operation member, and a focus position for detecting a focus position from an image signal obtained by the imaging means A focus adjustment device having a detection means and a conversion lens that can be freely mounted, wherein the focus adjustment lens is driven to the end of the driveable range by operating the operation member to focus on an object at infinity. The drive target position of the focus adjustment lens is designed to be different between when the conversion lens is attached and when it is not attached.

  The focus adjustment method of the focus adjustment apparatus of the present invention includes an imaging unit that photoelectrically converts a subject image formed by a photographing optical system to obtain an electrical image signal, and a focus of the subject image photoelectrically converted by the imaging unit. A focus adjustment lens for adjusting the focus, an operation driving means for driving the focus adjustment lens by operating an operation member, and a focus position detection means for detecting a focus position from an image signal obtained by the imaging means. And when the focus adjustment lens is driven to the end of the driveable range by operating the operation member to focus on an object at infinity, the drive target position of the focus adjustment lens is the same as when the conversion lens is mounted. A focus adjustment method of a focus adjustment device designed at a position different from that at the time of attachment, wherein the focus adjustment device determines whether or not the conversion lens is attached. When the conversion lens is attached to the focus determination device, the focus determination device sets the driveable range of the focus adjustment lens to the driveable range when the conversion lens is attached, while the conversion lens is not And a setting step for setting the driveable range of the focus adjustment lens to the driveable range when the focus adjustment lens is not attached.

  In the focus adjustment device according to the first aspect of the present invention, the drive target position of the focus adjustment lens when the focus adjustment lens is driven to the end of the driveable range by operating the operation member to focus on a subject at infinity. , It was designed at different positions when the conversion lens is installed and not. As a result, when the photographer performs an operation to focus on an object at infinity by mechanically operating the operation member to the end of the operable range, it is ensured that the camera is focused even when the conversion lens is attached. Can be matched.

  In the focus adjustment apparatus according to claim 2, the amount of change in the position of the focus adjustment lens that focuses on the subject at the maximum infinite distance, which is expected from the manufacturing error of the conversion lens, from the time when the conversion lens is attached or not attached is the closest side. Was set to Thus, regardless of the manufacturing error of the conversion lens, when the conversion lens is mounted, the focus can be reliably adjusted.

  According to the focus adjustment device of the third aspect, the drivable range when the conversion lens is mounted can be set to an appropriate range.

  According to the focus adjustment device of the fourth aspect, the driveable range of the focus adjustment lens can be easily changed depending on whether or not the conversion lens is attached.

  According to the focus adjustment apparatus of the fifth aspect, it is possible to set an optimum drivable range of the focus adjustment lens according to the type of the conversion lens.

  In the focus adjustment device according to the sixth aspect, after the focus adjustment lens is driven to a rough focus position by operating the operation member, the focus position detection unit drives the focus adjustment lens while the focus adjustment lens is driven by the automatic drive unit. The focal position is detected. In this case, the range to be searched is set wider than when the conversion lens is mounted and not. Thereby, focusing ability improves.

  In the focus adjustment apparatus according to the seventh aspect, the focus position is usually detected from the image signal obtained by the image pickup means while the focus adjustment lens is driven by the automatic drive means. In this case, the range to be searched is set wider than when the conversion lens is mounted and not. Thereby, in the case of performing automatic focus adjustment, the focusing ability is improved.

  In the focus adjusting apparatus according to the eighth aspect, it is considered that the closest position where photographing can be performed is also shifted because the position corresponding to infinity when the conversion lens is mounted is shifted by design. That is, it is possible to prevent the adverse effect that the focus lens exceeds the driveable range and the optical performance or the like deteriorates by making the closest distance at which photography is possible when the conversion lens is attached different from that when the conversion lens is not attached.

  Embodiments of a focus adjustment apparatus and a focus adjustment method of the present invention will be described with reference to the drawings. The focus adjustment apparatus of this embodiment is applied to a compact digital camera that is an imaging apparatus.

[First Embodiment]
FIG. 1 is a block diagram illustrating a configuration of an imaging apparatus according to the first embodiment. The imaging apparatus 1 includes a zoom lens group 2, a focus lens group 3, and a diaphragm 4 that controls the amount of light flux that passes through a photographic optical system composed of these. A member 31a for attaching a conversion lens 35 for converting a focal length and a conversion lens attachment detection switch 34 are provided at the distal end portion of the photographing lens barrel 31 having the zoom lens group 2, the focus lens group 3, the diaphragm 4, and the like. It has been. The conversion lens 35 can be attached to the imaging apparatus 1 by the member 31a.

  A solid-state imaging device (hereinafter referred to as a CCD) 5 forms a subject image that has passed through a photographing optical system, and photoelectrically converts this to obtain an image signal. The imaging circuit 6 receives the electrical signal photoelectrically converted by the CCD 5 and performs various image processing to generate a predetermined image signal. The A / D conversion circuit 7 converts the analog image signal generated by the imaging circuit 6 into a digital image signal.

  A memory (VRAM) 8 is a buffer memory or the like that receives the output of the A / D conversion circuit 7 and temporarily stores a digital image signal. The D / A conversion circuit 9 reads out the image signal stored in the VRAM 8, converts it into an analog signal, and converts it into an image signal suitable for reproduction output. An image display device (hereinafter referred to as an LCD) 10 includes a liquid crystal display device (LCD) or the like, and displays this image signal.

  The storage memory 12 is a semiconductor memory or the like, and stores image data. The compression / expansion circuit 11 includes a compression circuit and an expansion circuit. The compression circuit reads the image signal temporarily stored in the VRAM 8 and applies compression processing and encoding processing to the image data so as to be suitable for storage in the storage memory 12. The decompression circuit performs a decoding process, a decompression process, and the like on the image data stored in the storage memory 12 so as to be suitable for reproduction display and the like.

  The AE processing circuit 13 receives the output from the A / D conversion circuit 7 and performs automatic exposure (AE) processing. The scan AF processing circuit 14 receives the output from the A / D conversion circuit 7 and performs automatic focus adjustment (AF) processing.

  The CPU 15 incorporates a calculation memory and controls the imaging device 1. A timing generator (hereinafter referred to as TG) 16 generates a predetermined timing signal. The CCD driver 17 drives the CCD 5. The aperture drive motor 21 drives the aperture 4.

  The first motor drive circuit 18 drives the aperture drive motor 21. The focus drive motor 22 drives a focus lens group (hereinafter also simply referred to as a focus lens) 3. The second motor drive circuit 19 drives the focus drive motor 22. The zoom drive motor 23 drives the zoom lens group 2. The third motor drive circuit 20 drives the zoom drive motor 23.

  The operation switch 24 includes various switch groups. The EEPROM 25 is an electrically rewritable read-only memory in which programs for performing various controls, data used for performing various operations, and the like are stored in advance.

  The battery 26 is a power source for the imaging apparatus 1. The switching circuit 27 controls the flash emission of the strobe light emitting unit 28. The display element 29 is an LED or the like, and performs a warning display or the like. The speaker 30 performs voice guidance and warning. The AF auxiliary light 33 is composed of a light source such as an LED. The AF auxiliary light driving circuit 32 drives the AF auxiliary light 33.

  Note that a fixed semiconductor memory such as a flash memory is used as the storage memory 12 which is a storage medium for image data and the like. Further, a semiconductor memory such as a card type flash memory which is formed in a card shape or a stick shape and is detachable from the image pickup apparatus is used. In addition, various forms such as a magnetic storage medium such as a hard disk and a flexible disk are used.

  As the operation switch 24, a main power switch for starting up the imaging apparatus 1 to supply power, a release switch for starting a shooting operation, a playback switch for starting a playback operation, and a zoom lens group 2 of the shooting optical system are moved. There are zoom switches for zooming.

  The release switch has a first stroke (hereinafter referred to as SW1) for generating an instruction signal for starting an AE process and an AF process performed prior to the photographing operation, and a second stroke (for generating an instruction signal for starting an actual exposure operation). Hereinafter, it is composed of a two-stage switch with SW2).

  An operation of the imaging apparatus configured as described above will be described. First, the light flux of the subject that has passed through the photographing lens barrel 31 of the image pickup apparatus 1 is adjusted on the light amount by the diaphragm 4 and then formed on the light receiving surface of the CCD 5. This subject image is converted into an electrical signal by photoelectric conversion of the CCD 5 and output to the imaging circuit 6. In the imaging circuit 6, various signal processing is performed on the input signal, and a predetermined image signal is generated.

  The image signal is output to the A / D conversion circuit 7 and converted into a digital signal (image data), and then the image data is temporarily stored in the VRAM 8. The image data stored in the VRAM 8 is output to the D / A conversion circuit 9. After being converted into an analog signal by the D / A conversion circuit 9 and converted into an image signal suitable for display, the image signal is displayed on the LCD 10 as an image.

  The image data stored in the VRAM 8 is also output to the compression / decompression circuit 11. After compression processing is performed by the compression circuit in the compression / decompression circuit 11, the image data is converted into image data suitable for storage and stored in the storage memory 12.

  Further, for example, when a regeneration switch (not shown) of the operation switches 24 is operated and turned on, the regeneration operation is started. In the reproduction operation, the image data compressed and stored in the storage memory 12 is output to the compression / expansion circuit 11, subjected to a decoding process or an expansion process in the expansion circuit in the compression / expansion circuit 11, and then stored in the VRAM 8. Output and temporarily stored.

  Further, this image data is output to the D / A conversion circuit 9, converted into an analog signal by the D / A conversion circuit 9, converted into an image signal suitable for display, and then displayed on the LCD 10 as an image. Is done.

  On the other hand, the image data digitized by the A / D conversion circuit 7 is output to the AE processing circuit 13 and the scan AF processing circuit 14 separately from the VRAM 8. When receiving the input digital image signal (image data), the AE processing circuit 13 performs arithmetic processing such as cumulative addition on the luminance value of the image data for one screen. Thereby, the AE evaluation value corresponding to the brightness of the subject is calculated. This AE evaluation value is output to the CPU 15.

  When the scan AF processing circuit 14 receives the input digital image signal, the high-frequency component of the image data is extracted through a high-pass filter or the like, and is further subjected to arithmetic processing such as cumulative addition, so that the contour component on the high frequency side is obtained. An AF evaluation value signal corresponding to the amount or the like is calculated. Specifically, the scan AF processing circuit 14 extracts a high-frequency component of image data corresponding to a partial area of the screen designated as the AF area through a high-pass filter, and further performs arithmetic processing such as cumulative addition. Thereby, an AF evaluation value signal corresponding to the contour component amount on the high frequency side and the like is calculated. The AF area may be a single central portion, a central portion and a plurality of locations adjacent thereto, or a plurality of discretely distributed locations.

  As described above, the scan AF processing circuit 14 serves as a high-frequency component detection unit that detects a predetermined high-frequency component from the image signal generated by the CCD 5 in the process of performing the AF process.

  In addition, a predetermined timing signal from the TG 16 is output to the CPU 15, the imaging circuit 6, and the CCD driver 17. The CPU 15 performs various controls in synchronization with this timing signal. The imaging circuit 6 receives the timing signal from the TG 16 and performs various image processing such as color signal separation in synchronization with the timing signal. The CCD driver 17 receives the timing signal of the TG 16 and drives the CCD 5 in synchronization with the timing signal.

  The CPU 15 controls the first motor drive circuit 18, the second motor drive circuit 19, and the third motor drive circuit 20, respectively. The first motor drive circuit 18, the second motor drive circuit 19, and the third motor drive circuit 20 are connected to the diaphragm 4, the focus lens group 3, and the zoom lens via the diaphragm drive motor 21, the focus drive motor 22, and the zoom drive motor 23. Drive group 2. That is, the CPU 15 controls the first motor drive circuit 18 based on the AE evaluation value calculated by the AE processing circuit 13 to drive the aperture drive motor 21 and adjust the aperture amount of the aperture 4 appropriately. I do. Further, the CPU 15 controls the second motor drive circuit 19 based on the AF evaluation value signal calculated by the scan AF processing circuit 14 to drive the focus drive motor 22 to move the focus lens group 3 to the in-focus position. AF control is performed. When manual focus is set, the CPU 15 performs the following operation. That is, when a focus drive instruction member (focus operation button) (not shown) of the operation switches 24 is operated, the CPU 15 controls the second motor drive circuit 19 in accordance with the operation amount to switch the focus drive motor 22. Driven to move the focus lens group 3. When a zoom switch (not shown) among the operation switches 24 is operated, the CPU 15 receives this and controls the third motor drive circuit 20 to drive the zoom drive motor 23 and to zoom lens group 2. Is moved to perform a zooming operation of the photographing optical system.

  2 and 3 are flowcharts showing the shooting operation procedure of the imaging apparatus 1. FIG. This control program is stored in the EEPROM 25 and executed by the CPU 15. This shooting operation sequence is executed when the main power switch of the imaging apparatus 1 is in the ON state and the operation mode of the imaging apparatus 1 is in the shooting (recording) mode.

  In the present embodiment, the operation of acquiring the AF evaluation value while driving the focus lens group 3 to a predetermined position is referred to as scanning, and the position interval of the focus lens when acquiring the AF evaluation value is referred to as scanning interval. To do. The number of AF evaluation values acquired is referred to as the number of scan points, and the range of acquiring AF evaluation values is referred to as the scan range.

  First, the CPU 15 displays an image that is transmitted through the taking lens barrel 31 and formed on the CCD 5 as an image on the LCD 10 (step S1). That is, the subject image formed on the CCD 5 is photoelectrically converted by the CCD 5 and converted into an electrical signal, and then output to the imaging circuit 6. In the imaging circuit 6, various types of signal processing are performed on the input signal, a predetermined image signal is generated, and then output to the A / D conversion circuit 7. The image signal is converted into a digital signal (image data) by the A / D conversion circuit 7, and the image data is temporarily stored in the VRAM 8. The image data stored in the VRAM 8 is output to the D / A conversion circuit 9. In the D / A conversion circuit 9, the image data is converted into an analog signal, and after being converted into an image signal suitable for display, the image signal is displayed on the LCD 10 as an image.

  Subsequently, the CPU 15 determines whether or not the manual focus mode (MF mode) is set (step S2). If the manual focus (MF) mode is not set, the CPU 15 confirms the state of the release switch (step S3).

  When it is confirmed that the release switch is operated by the photographer and SW1 (first stroke of the release switch) is turned on, the CPU 15 executes normal AE processing (step S4). On the other hand, when SW1 is in the off state, the CPU 15 returns to the process of step S2. After the process of S4, the CPU 15 performs a scan AF process (step S5). That is, the CPU 15 performs a scan AF process for detecting the in-focus position in step S5. The outline is demonstrated using FIG. 4, FIG.

  FIG. 4 is a diagram for explaining the scan AF operation. Scan AF is performed by obtaining the position of the focus lens group 3 where the high-frequency component is the largest among the image signals generated and output by the CCD 5.

  The CPU 15 controls the focus drive motor 22 via the second motor drive circuit 19, and the focus lens group 3 is set in each shooting mode from a position corresponding to infinity ("A" position in FIG. 4). Drive to a position corresponding to the closest distance ("B" position in FIG. 4).

  While driving the focus lens group 3, the CPU 15 acquires the output (AF evaluation value signal) of the scan AF processing circuit 14. When the driving of the focus lens group 3 is completed, the CPU 15 obtains a position (“C” position in FIG. 4) at which the focus evaluation value is maximized from the acquired AF evaluation value signal, and drives the focus lens group 3 to that position. To do.

  The process of acquiring the output of the scan AF processing circuit 14 is not performed at the stop positions of all the focus lens groups 3 in order to increase the speed of the scan AF, but is performed at predetermined steps. In this case, for example, the AF evaluation value signal may be acquired at points a1, a2, and a3 shown in FIG. In such a case, the in-focus position C is obtained by calculation from the point at which the AF evaluation value signal has the maximum value (here, a2 point) and the points before and after (here, points a1 and a3). .

  In this way, before the interpolation calculation is performed and the point at which the AF evaluation value signal becomes the maximum value (the point “C” in FIG. 4) is obtained, the reliability of the AF evaluation value signal is evaluated. When the reliability is sufficient, the CPU 15 actually obtains a point where the AF evaluation value signal becomes the maximum value, and performs AFOK display in step S6 described later. This AFOK display is performed by turning on the display element 29 and at the same time by displaying green frames on the LCD 10.

  Further, when the reliability of the AF evaluation value signal is low as a result of evaluating the reliability of the AF evaluation value signal in step S5, the CPU 15 does not perform processing for obtaining the point at which the AF evaluation value signal becomes the maximum value, and in step S6 described later. Perform AFNG display. The AFNG display is performed by displaying the yellow frame on the LCD 10 at the same time as the display element 29 blinks.

  FIG. 5 is a flowchart showing the processing procedure of scan AF in step S4. First, the CPU 15 moves the focus lens 3 to the scan start position at a speed faster than the speed during the scanning operation (step S51). In the present embodiment, the scan start position is set at one end of the set scan range.

  The CPU 15 stores the focus evaluation value of the area corresponding to the AF area set in the imaging area and the position of the focus lens 3 in a calculation memory (not shown) built in the CPU 15 (step S52).

  The CPU 15 checks whether or not the lens position is at the scan end position (step S53). Here, the scan end position is set at the other end of the set scan range. If the lens position is not at the scan end position, the CPU 15 drives the focus lens 3 and moves it by a predetermined amount in a predetermined direction (step S54). Then, the CPU 15 returns to the process of step S52. On the other hand, when the lens position is at the scan end position, the CPU 15 calculates the peak position of the focus lens corresponding to the position where the focus evaluation value is maximum from the focus evaluation value stored in step S52 and the lens position (step S52). S55). Thereafter, the CPU 15 returns to the main process.

  Note that the scan start position and the end position are set by referring to a table indicating the relationship between the focus lens position and the subject distance, which is created from the result of adjustment performed at the time of manufacturing the camera. Further, the table indicating the relationship between the focus lens position and the subject distance is created from the focus lens position at the time of in-focus obtained as a result of performing an autofocus (AF) operation at a plurality of distances when the camera is manufactured.

  From this table, the focus lens positions corresponding to the closest and infinity corresponding to the focal length set by the photographer are read out, and are set as the focus lens closest end position and the focus lens infinity end position, respectively. The focus lens position shifted from the focus lens position corresponding to the infinity end to the ultra-infinity side by a predetermined amount is set as the scan start position. A focus lens position shifted from the focus lens position corresponding to the closest end in a direction opposite to infinity by a predetermined amount is set as a scan end position. This predetermined amount is called an overscan amount. The AF evaluation value signal generated by the subject existing at the infinity end position or the close end position has an extreme value, and the focus lens is driven to a position where the extreme value is given, so that the infinity end position or the Make sure to focus on the subject at the near end. For this reason, an overscan amount is provided.

  After the scan AF process is performed in step S5, the CPU 15 performs AFOK display or AFNG display (step S6).

  The CPU 15 determines whether or not the ON state of SW1 (first stroke of the release switch) is maintained (step S7). If not, the CPU 15 returns to the process of step S1. On the other hand, if held, the CPU 15 confirms SW2 (second stroke of the release switch) (step S8).

  When SW2 is on, the CPU 15 initializes a continuous shooting counter for counting the number of continuous shots to a value 1 only when the continuous shooting mode is set (step S9). Thereafter, the CPU 15 executes actual exposure processing, and when the continuous shooting mode is set, the CPU 15 increases the value of the continuous shooting counter by +1 and simultaneously performs face detection (step S10).

  Since this face detection is for determining whether or not the prediction of the movement of the subject is correct, it is performed even when the face detection function is turned off by the photographer. An image used for face detection is an image immediately before exposure displayed on the EVF. The CPU 15 performs face detection and records whether or not detection is possible (whether or not face detection was possible). If the detection is possible, the CPU 15 also records the size of the detected face and the position on the screen.

  When the exposure processing and face detection are completed, the CPU 15 confirms SW2 (second release switch stroke) again (step S11). CPU15 returns to the process of step S7, when SW2 is OFF.

  On the other hand, when the ON state of SW2 is maintained in step S11, that is, when the continuous shooting mode is set, the CPU 15 performs AF processing (inter-continuous shooting AF processing) performed between the shootings. It performs (step S12). After the continuous shooting AF process is completed, the CPU 15 returns to the process of step S10 and executes the actual exposure process.

  This continuous shooting AF process is executed only when the continuous mode is set by the photographer. If the continuous mode is not set, the CPU 15 checks the state of SW2 in step S11 after the exposure processing in step S10 is completed. If the SW2 on state is maintained, the CPU 15 waits until the SW2 is turned off. To do.

  The continuous shooting AF process is a process for responding to the movement of the focus position of the subject during continuous shooting, and the focus position of the subject in the next shooting during continuous shooting is determined based on the focus position information so far. This is the processing to be sought. The details of this process are not directly related to the present invention, and are therefore omitted. Details and details are described in the specification and drawings of Japanese Patent Application No. 2006-210253.

  If the continuous mode is set and SW2 is turned off in step S8, the CPU 15 returns to the process of step S7 and waits until SW2 is turned on. However, if SW1 is turned off during this period, the CPU 15 returns to the process of step S1.

  When the manual focus (MF) mode is set in step S2, the CPU 15 determines whether or not the focus operation button, which is an operation member, has been operated by the photographer (steps S13 and S14). When being operated, the CPU 15 drives the focus lens in a predetermined direction by a predetermined amount.

  That is, the CPU 15 first determines whether or not the focus operation button for driving the focus lens 3 in the closest direction among the operation switches 24 has been operated (step S13). When being operated, the CPU 15 drives the focus lens toward the close end while checking whether the focus lens 3 has reached the close end (step S15). On the other hand, if not operated in S13, the CPU 15 determines whether or not the focus operation button for driving the focus lens 3 in the infinity direction among the operation switches 24 has been operated (step S14). If it is operated, the CPU 15 drives the focus lens toward the infinity end while checking whether the focus lens 3 has reached the infinity end (step S16). In addition, the process of step S13 to S16 is corresponded to the operation drive means as described in a claim.

  After the processing of S15 and S16, or when not operated in S14, the CPU 15 determines whether or not SW1 (first stroke of the release switch) is in an on state (step S17). When it is in the off state, the CPU 15 returns to the process of step S1.

  On the other hand, when it is in the ON state, the CPU 15 determines whether or not the execution of the safety MF is instructed (step S18). If not instructed, the CPU 15 proceeds to the process of step S8, and performs an exposure process according to the state of SW2.

  On the other hand, when execution of safety MF is not instructed in step S18, the CPU 15 performs safety MF processing (step S19). The safety MF is a scan AF processing circuit 14 that detects the in-focus position from the image signal generated by the image sensor (CCD 5) while driving the focus lens 3 after roughly focusing with manual focus. This is a process for focusing. That is, after the focus lens is driven to a rough focus position by manual focus, an operation of driving the focus lens to a detailed focus position by autofocus is performed.

  In the process of step S19, the CPU 15 first checks whether or not a conversion lens is attached, and if so, what kind is the type. When a teleconversion lens is attached, the focus search range is expanded compared to other cases. This is because when the teleconversion lens is mounted, the depth of field becomes shallow, and an error in focusing due to manual focus increases. Therefore, the enlargement ratio is a value proportional to the square of the change in focal length before and after the teleconversion lens is mounted. When the magnification of the teleconverter lens is 1.4 times, the enlargement ratio is doubled. The focusing ability is improved by making the focus search range wider when the teleconversion lens is attached than when it is not attached. As described above, in the process of S19, the CPU 15 detects the in-focus position from the image signal generated by the image pickup device while driving the focus lens within the set focus search range. After the end of this process, the CPU 15 proceeds to the process of step S8.

  FIG. 6 is a flowchart showing the focus lens driving procedure in steps S15 and S16. First, the CPU 15 determines whether or not the conversion lens 35 is attached (step S71). This determination is made by reading the output of the conversion lens attachment detection switch 34. In addition, the process of step S71 is equivalent to the mounting | wearing discrimination | determination means as described in a claim.

  When the conversion lens 35 is not attached, the CPU 15 sets the moving range of the focus lens at the time of manual focus (step S72). The setting of the movement range of the focus lens is performed by referring to a table showing the relationship between the focus lens position and the subject distance, which is created from the result of adjustment performed at the time of manufacturing the camera. Further, as described above, the table indicating the relationship between the focus lens position and the subject distance is created from the focus lens position at the time of focusing obtained by performing AF at a plurality of distances when manufacturing the camera. From this table, the focus lens positions corresponding to the closest and infinity corresponding to the focal length set by the photographer are read out, and are set as the focus lens closest end position and the focus lens infinity end position, respectively.

  As described above, the scan range at the time of the scan AF is also set from the focus lens positions corresponding to the closest and infinity corresponding to the focal length set by the photographer read from the table. In setting the scan range during scan AF, the focus lens position shifted from the focus lens position corresponding to the infinity end to the ultra-infinity side by a predetermined amount is set as the scan start position. The focus lens position shifted from the focus lens position corresponding to the closest end by a predetermined amount in the direction opposite to infinity is set as the scan end position. This predetermined amount is called an overscan amount. The AF evaluation value signal generated by the subject existing at the infinity end position or the closest end position has an extreme value, and the focus lens is driven to a position where the extreme value is given, so that the infinity end position or the Make sure to focus on the subject at the near end. For this reason, an overscan amount is provided.

  On the other hand, when the conversion lens is attached in step S71, the CPU 15 reads the output of the conversion lens attachment detection switch 34 to determine the type of the attached conversion lens (step S73).

  In the case of a compact digital camera, the conversion lenses that can be attached are limited by model. Usually, there is one type of teleconversion lens and one type of wide conversion lens. In rare cases, a plurality of teleconversion lenses and wide conversion lenses can be attached, and there are cases where only one type of teleconversion lens or wide conversion lens can be attached. Here, assuming a general case, a case where one type of teleconversion lens and one type of wide conversion lens can be attached will be described. Note that the processing in step S73 corresponds to the type determination means described in the claims.

  When the conversion lens attached in step S74 is a tele conversion lens, the CPU 15 obtains the focus lens closest end position and the focus lens infinite end position (step S74). For calculation of these positions, a table indicating the relationship between the focus lens position and the subject distance, which is created from the result of adjustment performed at the time of manufacturing the camera, and the design value of the teleconversion lens are used. In other words, the focus lens position corresponding to the closest distance and infinity corresponding to the focal length set by the photographer obtained by referring to the table is the distance between the closest distance and infinity obtained from the design value of the teleconversion lens. A position obtained by adding the shift amount of the focus lens position is obtained. The obtained position is the focus lens closest end position and the focus lens infinite end position.

  On the other hand, when the conversion lens attached in step S73 is a wide teleconversion lens, the CPU 15 sets the movement range of the focus lens during manual focus (step S75). In the process of step S75, as in the process of step S74, the CPU 15 obtains the focus lens closest end position and the focus lens infinity end position. For calculation of these positions, a table indicating the relationship between the focus lens position and the subject distance, which is created from the result of adjustment performed at the time of manufacturing the camera, and the design value of the wide conversion lens are used. That is, the focus lens position corresponding to the closest distance and infinity corresponding to the focal length set by the photographer obtained by referring to the table is the distance between the closest distance and infinity obtained from the design value of the wide conversion lens. A position obtained by adding the shift amount of the focus lens position is obtained. The obtained position is the focus lens closest end position and the focus lens infinite end position.

  The CPU 15 determines whether the drive direction of the focus lens 3 is the near side or the infinity side (step S76). As a result, when the drive direction is the close side, the CPU 15 determines whether or not the current focus lens position is the close end (step S77). If it is not the close end, the CPU 15 drives the focus lens 3 in the close direction by a predetermined amount (step S78). However, the CPU 15 drives the focus lens 3 to the close end when the predetermined end is exceeded when the predetermined amount is driven. After this, or when it is the closest end in step S77, the CPU 15 returns to the main processing.

  On the other hand, when the drive direction is the infinity side, the CPU 15 determines whether or not the current focus lens position is the infinity end (step S79). If it is not the infinity end, the CPU 15 drives the focus lens 3 in the infinity direction (step S80). However, if the infinity end is exceeded when the predetermined amount is driven, the CPU 15 drives the focus lens 3 to the infinity end. After this, or when it is the infinity end in step S79, the CPU 15 returns to the main processing. This predetermined amount is preferably set to a value that is about half of the focal depth at the focal length designated by the photographer.

  Here, the reason why the focus lens position is shifted in steps S74 and S75 will be described. FIG. 7 is a diagram showing the relationship between the focus lens position and the subject distance. FIG. 2A shows a case where a conversion lens (here, a teleconversion lens) is not attached. In the figure, it is represented by “Tele (no telecon)”. In this case, as shown in step S72, from the table showing the relationship between the focus lens position and the subject distance created at the time of manufacturing the camera, it corresponds to the nearest and infinity corresponding to the focal length set by the photographer. Read the focus lens position. Then, the read focus lens positions are set as the focus lens closest end position and the focus lens infinite end position (symbol a in the figure).

  In this case, if the photographer manually operates the focus adjustment lens to the end of the driveable range to focus on an object at infinity, the focus lens drive target position Is the infinity end position. This makes it possible to focus on an infinite subject.

  However, when a conversion lens (teleconversion lens) is attached, the infinity end position is determined as shown in step S72, and when the position is set as the focus lens drive target position, the object at infinity is focused. I can't. This is because the focus lens position that focuses on an object at infinity is set closer to the near distance side than the position when the conversion lens (teleconversion lens) has a manufacturing error in consideration of manufacturing errors. . When a conversion lens is mounted due to a manufacturing error of the conversion lens, the focal length of the lens and the camera body lens combined, the interval between the mounted conversion lens and the camera body, and the like change. Due to this change, the focus lens position for focusing on an object at infinity differs.

  FIG. 5B shows a case where the infinity focus position of the camera body lens matches the infinity focus position when the conversion lens is mounted in the design of the conversion lens (teleconversion lens). (In the figure, symbol b). In the figure, it is expressed as “design Tele∞ = telecon control∞”. When the conversion lens is manufactured according to the design value, there is no problem, but since a manufacturing error always occurs, the focus lens position for focusing on an object at infinity changes. In FIG. 4B, the range of the change is shown. Specifically, when the position of the focus lens that focuses on an object at infinity is shifted to the extreme infinity side, it is outside the drive limit of the focus lens (symbol c in the figure). In this case, a camera that cannot focus on a subject at infinity is created. Note that the focus lens position for focusing on an object at infinity changes even when it is shifted to the close side (symbol d in the figure).

  In order to avoid such a situation, as shown in FIG. 3C, the change in the focus lens position that focuses on the subject at the maximum infinite distance expected from the manufacturing error of the conversion lens is infinite in the closest direction. The focus lens position for focusing on a distant subject is shifted. In FIG. 7, the maximum shift position due to the manufacturing error of the conversion lens is the position of L (m) before the conversion lens is mounted (reference symbol e in the figure). In the figure, it is expressed as “Design Tele L (m) = Telecon ∞”.

  In this way, the focus lens position that focuses on an object at infinity is shifted in advance. For this reason, when the conversion lens is attached and the infinity end position recorded on the table created at the time of manufacturing the camera is set as the focus lens drive target position, it is impossible to focus on the infinity subject.

  Accordingly, as shown in FIG. 5C, the focus lens that focuses on the object at infinity in the closest direction by the change in the focus lens position that focuses on the maximum object at infinity that is expected from the manufacturing error of the conversion lens. The position is shifted. Accordingly, when the photographer manually operates the focus adjustment lens to the end of the driveable range to focus on an object at infinity, the drive target position of the focus lens is displayed on the table. Shift from the recorded infinity end position (symbol e in the figure). This makes it possible to focus on an infinite subject.

  Here, the design of the conversion lens is considered. In general, many conversion lenses are manufactured close to design values. Therefore, considering the depth, in many individuals, even when a conversion lens is attached, it is possible to focus on an object at infinity by mechanically operating the focus adjustment lens to the end of the driveable range by manual operation. become. However, for a very small number of individuals, the focus lens position for focusing on an object at infinity varies greatly due to a manufacturing error of the conversion lens, so that it cannot be focused by this operation.

  In this case, the above design avoids the problem of being out of focus with respect to an object at infinity, but as shown in FIG. 5C, the focus lens is driven as much as before the conversion lens is mounted, as shown in FIG. In some cases, the drive limit on the near side may be exceeded (reference symbol g in the figure). However, in the case of the close side, since it can be focused by moving away from the subject, this is not a big problem. However, when a teleconversion lens is mounted even with the same focus lens driving amount, the closest distance that can be photographed becomes far.

  In addition, as shown in FIG. 6C, when manufacturing errors are taken into account, in all individuals, scanning AF is performed from infinity to the closest distance that can be photographed with the conversion lens attached and the focal length changed. In order to focus, it is necessary to expand the scan range. That is, it can be seen that the scan range must be expanded by the amount of change in the focus lens position that focuses on an object at infinity due to a manufacturing error of the conversion lens. This will be described in detail in the second embodiment.

  In the first embodiment, when a photographer performs an operation of focusing on an object at infinity by mechanically operating the focus adjustment lens to the end of the drivable range by manual operation, the infinity hit position Is shifted by the design value from when the conversion lens is not attached. This makes it possible to focus even when the conversion lens is mounted. Note that the infinite contact position is the focus when the operation member (focus operation button) is operated to focus on an infinite subject by mechanically operating the operation member (focus operation button) to the end of the operable range. This is the lens drive target position.

  In addition, when performing focus in detail with the scan AF processing circuit 14 while driving the focus lens after roughly focusing with manual focus, the focus search range is not attached when the teleconversion lens is attached. Make it wider than time. Thereby, focusing ability improves. The scan AF processing circuit 14 detects the in-focus position from the image signal generated by the image sensor.

[Second Embodiment]
The imaging apparatus of the second embodiment is different from the first embodiment in that the scan range is widened by the change of the focus lens position for focusing on an object at infinity due to the manufacturing error of the conversion lens. . When the manufacturing error of the conversion lens occurs, this scan range is extended by using the scan AF from all the individuals to the closest distance that can be taken with the conversion lens attached and the focal length changed. Done for.

  Note that the configuration and operation of the imaging apparatus according to the second embodiment are substantially the same, and therefore different operations will be described here.

  FIG. 8 is a flowchart showing the processing procedure of scan AF in step S4 of the second embodiment. First, the CPU 15 sets a scan start position and an end position (step S51A). The setting of the scan start position and the end position is performed by referring to a table showing the relationship between the focus lens position and the subject distance created from the result of adjustment performed at the time of manufacturing the camera. As described above, the table indicating the relationship between the focus lens position and the subject distance is created from the focus lens position at the time of in-focus obtained by performing AF at a plurality of distances when the camera is manufactured. From this table, the focus lens positions corresponding to the closest and infinity corresponding to the focal length set by the photographer are read out, and are set as the focus lens closest end position and the focus lens infinity end position, respectively.

  The focus lens position shifted from the focus lens position corresponding to the infinity end to the ultra-infinity side by a predetermined amount is set as the scan start position. The focus lens position shifted from the focus lens position corresponding to the closest end by a predetermined amount in the direction opposite to infinity is set as the scan end position.

  This predetermined amount is called an overscan amount. This predetermined amount is obtained by driving the focus lens to a position where the AF evaluation value signal generated for the subject existing at the infinity end position or the close end position has an extreme value and gives the extreme value. This is provided to ensure that the subject is in focus.

  The CPU 15 determines whether or not a conversion lens is attached (step S51B). This determination is made by reading the output of the conversion lens attachment detection switch 34. If the conversion lens is not attached, the process proceeds to step S51. Scan AF processing is started. Since the processing after step S51 is the same as that of the first embodiment, the description thereof is omitted.

  On the other hand, when the conversion lens is attached, the CPU 15 determines whether or not the search is instructed by the closest focus lens position search instruction switch (not shown) among the operation switches 24 (step S51C). ). When the search is not instructed, the CPU 15 determines the scan end position set in S51A based on the design value of the conversion lens and the manufacturing error assumed in the design based on the type of the conversion lens detected in S51B. Is changed (step S51D).

  As described above, the focus lens position that focuses on the closest object that can be photographed at the set focal length is set closer to the near side than the position when the lens is not mounted in consideration of the manufacturing error of the conversion lens. It has been set (see FIG. 7C). Furthermore, this position varies due to manufacturing errors. Therefore, considering the variation, the focus lens position focused on the closest object that can be photographed located on the closest side (left side in the figure) is shifted in the opposite direction from the infinity side by the amount of overscan. The focus lens position is set as the scan end position. However, since the focus lens position may exceed the focus lens drive limit as shown in FIG. 7C, when the drive limit is exceeded, the overscan amount from the drive limit is infinite. The focus lens position shifted to the side is set as the scan end position.

  Then, based on the type of conversion lens detected in S51B, the CPU 15 changes the scan start position set in S51A based on the design value of the converged lens and the manufacturing error assumed in design (step). S51F). As shown in FIG. 7C, the focus lens position that focuses on the object at infinity is set closer to the near side than the position when the lens is not mounted in consideration of manufacturing errors. Furthermore, this position varies due to manufacturing errors. Therefore, considering the variation, the scan start position is the focus lens position shifted from the focus lens position focused on the infinity subject located on the most infinity side (right side in the figure) to the ultra infinity side by the overscan amount. And

  On the other hand, when the search is instructed in step S51C, the CPU 15 searches for the closest focus lens position and changes the scan end position (step S51E). This measures the position of the drive limit of the focus lens 3 by driving the focus lens 3 at a low speed so as not to damage the member and bringing it into contact with the drive limit on the closest end side. That is, the focus lens 3 is moved at a low speed, and the position is detected by a sensor. The position where the output of the sensor does not change even when the focus lens 3 is driven is the drive limit position.

  In step S51F, the CPU 15 changes the scan start position set in S51A based on the conversion lens detected in S51B and based on the design value of the conversion lens and the manufacturing error assumed in the design. To do.

  After the process of S51F, the CPU 15 proceeds to the process of step S51. As described above, the processes after step S51 are the same as those in the first embodiment, and thus the description thereof is omitted.

  In the second embodiment, when the focus position is detected from the image signal generated by the image sensor while driving the normal focus lens, the focus search range is set when the conversion lens is mounted and when the conversion lens is not mounted. Widening the focus also improves the focusing ability.

  Furthermore, in order to avoid the influence due to manufacturing errors and the like, the position corresponding to infinity when the conversion lens is mounted is shifted by design, so that the closest position where photographing can be performed is also shifted. Taking this into consideration, the focus lens can exceed the driveable range and the optical performance and the like are deteriorated by making the closest distance (the focus lens drive permission range) when the conversion lens is mounted different from that when the conversion lens is not mounted. It can prevent harmful effects.

  The present invention is not limited to the configuration of the above-described embodiment, and any configuration can be used as long as the functions shown in the claims or the functions of the configuration of the present embodiment can be achieved. Is also applicable.

  For example, in the above-described embodiment, a compact digital camera has been described as an example, but the present invention can also be applied to a digital video camera or a digital single-lens reflex camera (SLR).

It is a block diagram which shows the structure of the imaging device in 1st Embodiment. 4 is a flowchart illustrating a shooting operation procedure of the imaging apparatus 1. 3 is a flowchart illustrating a shooting operation procedure of the imaging apparatus 1 following FIG. 2. It is a figure explaining scan AF operation. It is a flowchart which shows the process sequence of the scan AF in step S4. It is a flowchart which shows the drive procedure of the focus lens in step S15 and S16. It is a figure which shows the relationship between a focus lens position and a to-be-photographed object distance. It is a flowchart which shows the process sequence of scan AF in step S4 of 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging device 3 Focus lens 14 Scan AF processing circuit 15 CPU
24 Operation switch 35 Conversion lens

Claims (9)

Imaging means for photoelectrically converting a subject image formed by the photographing optical system to obtain an electrical image signal, a focus adjustment lens for adjusting the focus of the subject image photoelectrically converted by the imaging means, and an operation member Focus adjustment that has an operation drive means for driving the focus adjustment lens by the operation and a focus position detection means for detecting a focus position from the image signal obtained by the imaging means, and a conversion lens can be mounted freely A device,
When the focus adjustment lens is driven to the end of the driveable range by operating the operation member to focus on an object at infinity, the drive target position of the focus adjustment lens is when the conversion lens is attached and when it is not attached The focus adjustment device is characterized by being designed at different positions.   The change of the position of the focus adjustment lens that focuses on the subject at the maximum infinite distance, which is expected from the manufacturing error of the conversion lens, from the drive target position when the conversion lens is mounted to the drive target position when the conversion lens is not mounted 2. The focus adjustment apparatus according to claim 1, wherein the focus adjustment apparatus is set to the closest side by an amount corresponding to the distance.   The focus adjustment apparatus according to claim 1, wherein a driveable range of the focus adjustment lens when the conversion lens is attached is different from a driveable range of the focus adjustment lens when the conversion lens is not attached. A wearing discriminating means for discriminating whether or not the conversion lens is worn;
When the conversion lens is attached, the driveable range of the focus adjustment lens is set to the driveable range when the conversion lens is attached, while when the conversion lens is not attached, the focus adjustment lens is driven. 4. The focus adjusting apparatus according to claim 3, further comprising setting means for setting a possible range to a drivable range when not attached. Having a type determining means for determining the type of the conversion lens;
5. The focus adjustment apparatus according to claim 4, wherein, when the conversion is attached, the setting unit sets the driveable range when the conversion lens is attached according to the type of the conversion lens. Automatic driving means for automatically driving the focusing lens;
After the focus adjustment lens is driven to a rough focus position by operating the operation member, the focus position detection is performed from the image signal obtained by the imaging means while the focus adjustment lens is driven by the automatic drive means. 2. The focus adjusting apparatus according to claim 1, wherein a range in which the means searches for detecting a detailed in-focus position is set wider when the conversion lens is mounted than when the conversion lens is not mounted. Automatic driving means for automatically driving the focusing lens;
While driving the focus adjustment lens by the automatic drive means, a range in which the focus position detection means searches for detecting the focus position from the image signal obtained by the imaging means, when the conversion lens is mounted, The focus adjusting apparatus according to claim 1, wherein the focus adjusting apparatus is set to be wider than when not attached.   When the conversion lens is mounted, the focus adjustment lens is driven to come into contact with the drive limit on the closest end side to detect the position of the focus adjustment lens, and the near end of the search range for the detected position The focus adjusting apparatus according to claim 7, wherein the focus adjusting apparatus is set as follows. Imaging means for photoelectrically converting a subject image formed by the photographing optical system to obtain an electrical image signal, a focus adjustment lens for adjusting the focus of the subject image photoelectrically converted by the imaging means, and an operation member An operation driving means for driving the focus adjustment lens by the operation and a focus position detecting means for detecting a focus position from the image signal obtained by the imaging means, and to focus on an infinite subject. Focus adjustment designed so that the drive target position of the focus adjustment lens is different between when the conversion lens is attached and when it is not attached when the focus adjustment lens is driven to the end of the driveable range by operating the operation member. A device focus adjustment method comprising:
A mounting determination step in which the focus adjustment device determines whether or not the conversion lens is mounted;
When the focus adjustment device is mounted with the conversion lens, the driveable range of the focus adjustment lens is set to the driveable range when the conversion lens is mounted, while the conversion lens is not mounted. And a setting step for setting the driveable range of the focus adjustment lens to the driveable range when the focus adjustment lens is not attached.

Images