JP2009239460A - Focus control method, distance measuring equipment, imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that deviation will arise in matching of an image and distance information when the distance information is acquired by picking up the image at a plurality of focusing positions. <P>SOLUTION: An imaging device comprises an optical block 1a including an imaging optical system, an image sensor 1c provided in the post-stage thereof, an optical block driver 1e for driving the optical block 1a, and a CPU 2a for extracting a pixel based on an image signal outputted from the image sensor at optical block driving, creating the image of an object by compounding focused pixels thus extracted, storing the focused pixels extracted by contrast determination in association with the information on photography distance to which the imaging optical system is focused, changing the focusing position by driving the imaging optical system, and controlling to drive other lens group provided independently from a lens group for changing the focusing position in the imaging optical system. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a focus control method, a distance measuring device, and an imaging device that correct a change in focal length when the focus position is changed, for example, when distance information is acquired by imaging at a plurality of focus positions.

  2. Description of the Related Art Conventionally, in an imaging apparatus such as a digital still camera or a digital video camera, distance information to a subject in a captured image (what associates a distance to an object in a captured image in pixel units) has been acquired. As this distance information, for example, a depth map is used. This “depth map” is distance information acquired by associating the distance to an object in an image in units of pixels.

  On the other hand, when acquiring an image while changing the in-focus position, only in-focus pixels are extracted in contrast determination. For example, Patent Document 1 discloses a technique for acquiring an image that is in focus in all depth directions by acquiring an image while changing the in-focus position and extracting only in-focus pixels in contrast determination. ing.

  However, when capturing distance information by capturing images at a plurality of in-focus positions, the focal length changes and the angle of view changes in a general optical system. There was a problem that errors would occur. To solve this, a calibration technique is also used, but the processing is complicated. Furthermore, although a technique for calculating distance information using this has been developed, it does not sufficiently suppress errors generated in the calculation process. There is also a problem that the processing load is heavy.

One means for solving these problems is to use a telecentric optical system. In general, the optical system focuses on its telecentricity,
・ Image side (image side) telecentric optical system
-Object side (object side) telecentric optical system
・ Both telecentric optics
・ Non-telecentric optics
Can be classified.

Among these, if the object side telecentric optical system and the both side telecentric optical system are used, it is possible to suppress the change in the angle of view (the shape change in the subject image) when the distance information is acquired by imaging at a plurality of focusing positions. . Therefore, it is possible to suppress an error that occurs in association between an image and distance information.
JP-A-6-311411

  However, in order to use the object side telecentric optical system, the principal ray and the optical axis must be made parallel on the object side by matching the exit pupil position and the image side (image plane side) focal position. In other words, there is a problem that it is difficult to realize with a device (for example, a digital camera) that prioritizes miniaturization due to large design constraints.

  Further, in order to use the double telecentric optical system, the principal ray and the optical axis are made parallel on the image plane side by matching the entrance pupil position with the front (object side) focal position. Then, the principal ray and the optical axis must be parallel on the object side by matching the exit pupil position and the rear (image plane side) focal position. For this reason, there is a problem that it is difficult to realize with a device (for example, a digital camera) that prioritizes miniaturization because design constraints are large.

  In particular, in recent years, there is a growing need for higher magnification and a smaller size of a zoom lens. In order to achieve this, it is difficult to add telecentricity to design constraints.

  Therefore, in the present invention, when acquiring distance information by imaging at a plurality of in-focus positions, the focal length changes and the angle of view changes in a general optical system. It is an object of the present invention to solve the problem that an error is caused in the association of.

  The focus control method according to the first aspect of the present invention determines a pixel contrast based on an image signal, generates distance information of a focused pixel based on a determination result of the contrast determination, The distance information is stored in association with the distance information. Then, at least one second lens group that is provided separately from the first lens group that changes the in-focus position and the in-focus position is changed between the movement amount of the first lens group and the effective focal length. Drive according to the amount of movement to keep the effective focal length constant according to the relationship with the amount of change.

  A distance measuring device according to a second aspect of the present invention generates a distance information of a focused pixel based on a determination result by a contrast determination unit that determines a pixel contrast based on an image signal, and a determination result by the contrast determination unit, Distance information generating means for storing the focused pixel and the distance information in association with each other is provided. In particular, at least one second lens group that is provided separately from the first lens group that changes the in-focus position and changes the in-focus position is used as the amount of movement of the first lens group. Lens driving means for driving according to the amount of movement for keeping the effective focal length constant according to the relationship with the amount of change in focal length.

  An image pickup apparatus according to a third aspect of the present invention includes an image pickup optical system, an image pickup element disposed behind the image pickup optical system, and lens driving means for driving the image pickup optical system. Then, a contrast determination unit that extracts pixels based on an image signal output from the image pickup device as the imaging optical system is driven by the lens driving unit, and a focused pixel extracted by the contrast determination unit are combined. Image generation means for generating an image of a subject is included. Furthermore, it has distance information generation means for storing the in-focus pixel extracted by the contrast determination means and information on the shooting distance at which the imaging optical system is focused by the lens driving means in association with each other. In particular, the lens driving unit changes the in-focus position and changes at least one other lens group provided separately from the in-focus position changing lens group for changing the in-focus position. In accordance with the relationship between the moving amount of the lens group and the change amount of the effective focal length, the driving is performed according to the moving amount for keeping the effective focal length constant.

  Therefore, according to the above first to third aspects, at least one second lens group provided separately from the first lens group that changes the in-focus position is driven, for example, an angle of view. The focus control is performed while the parameters are kept constant.

  According to the present invention, when acquiring distance information by imaging at a plurality of in-focus positions, the focal length changes and the angle of view changes in a general optical system. Thus, it is possible to provide a focus control method, a distance measuring device, and an imaging device that solve the problem that an error occurs in the association.

  The best mode for carrying out the present invention (hereinafter simply referred to as an embodiment) will be described below in detail with reference to the drawings.

  FIG. 1 shows a configuration when a distance measuring apparatus according to an embodiment of the present invention is applied to an imaging apparatus. As shown in FIG. 1, an imaging apparatus according to this embodiment includes a camera unit 1, a control unit 2, a camera DSP (Digital Signal Processor) 3, an SDRAM (Synchronous Dynamic Random Access Memory) 4, and a medium. An interface (hereinafter referred to as a medium I / F) 5, an operation unit 7, an LCD (Liquid Crystal Display) controller 8 and an LCD 9, and an external interface (hereinafter referred to as an external I / F) 10, and a recording medium 6 are attached and detached. It is possible.

  The recording medium 6 may be a so-called memory card using a semiconductor memory, an optical recording medium such as a recordable DVD (Digital Versatile Disk) or a recordable CD (Compact Disc), or a magnetic disk. .

  The camera unit 1 includes an optical block 1a, an aperture 1b, an imaging device 1c such as a CCD (Charge Coupled Device), an A / D conversion circuit 1d, an optical block driver 1e, an aperture driver 1f, an imaging device driver 1g, and timing generation. The circuit 1h, the drive part 1i, the detection part 1j, the blur detection part 1k, etc. are provided. Here, the optical block 1a includes a lens and an imaging optical system, and includes, for example, a focus mechanism, a shutter mechanism, a camera shake driving unit, and the like. A zoom lens is used as the lens in the optical block 1a.

  The control unit 2 is a microcomputer configured by connecting a CPU (Central Processing Unit) 2a, a RAM (Random Access Memory) 2b, a flash ROM (Read Only Memory) 2c, a clock circuit 2d, etc. through a system bus 2e, It controls the respective parts of the imaging apparatus of this embodiment.

  The RAM 2b is mainly used as a work area such as temporarily storing intermediate results of processing. The flash ROM 2c stores various programs executed by the CPU 2a, data necessary for processing, and the like. The clock circuit 2d can provide the current date, the current day of the week, and the current time, as well as the shooting date and time.

  At the time of image capturing, the optical block driver 1e forms a drive signal for operating the optical block 1a in accordance with the control from the control unit 2, and supplies the drive signal to the optical block 1a to provide the optical block 1a. The block 1a is operated. The optical block 1a captures an image of a subject in response to a drive signal from the optical block driver 1e and provides it to the image sensor 1c. In this case, the optical block driver 1e and the CPU 2a realize a lens driving function.

  The image pickup device 1c photoelectrically converts an image from the optical block 1a and outputs the image. The image pickup device 1c operates according to a drive signal from the image pickup device driver 1g, and captures an image of a subject from the optical block 1a. Further, based on the timing signal from the timing generation circuit 1h controlled by the control unit 2, the captured analog image data of the subject is supplied to the A / D conversion circuit 1d. The A / D conversion circuit 1d performs A / D conversion to form image data converted into a digital signal.

  The image data converted into the digital signal is supplied to the camera DSP 3. The camera DSP 3 performs camera signal processing such as AF (Auto Focus), AE (Auto Exposure), and AWB (Auto White Balance) on the image data supplied thereto. The image data adjusted in this way is compressed by a predetermined compression method, supplied to the recording medium 6 through the system bus 2e and the medium I / F 5, and recorded. When the camera DSP 3 performs a distance measuring operation under the control of the CPU 2a, it functions as a distance measuring device.

  The image data recorded on the recording medium 6 is read from the recording medium 6 through the medium I / F 5 in accordance with the operation input from the user received through the operation unit 7 including a touch panel and control keys. And supplied to the camera DSP3.

  The camera DSP 3 performs decompression processing (decompression processing) such as data compression on the image-compressed image data read from the recording medium 6 and supplied through the medium I / F 5, and the decompressed image data is stored in the system The data is supplied to the LCD controller 8 through the bus 2e. The LCD controller 8 forms an image signal to be supplied to the LCD 9 from the image data supplied thereto, and supplies this to the LCD 9. As a result, an image corresponding to the image data recorded on the recording medium 6 is displayed on the display screen of the LCD 9.

  It is also possible to connect to an external personal computer through the external I / F 10, receive image data from the personal computer, and record it on the recording medium 6. Further, the image data recorded on the recording medium 6 can be supplied to an external personal computer or the like through the external I / F 10.

  Further, by connecting a communication module to the external I / F 10, for example, it is possible to connect to a network such as the Internet, acquire various image data and other information through the network, and record them on the recording medium 6. Alternatively, the data recorded on the recording medium 6 can be transmitted to the intended destination through the network.

  The external I / F 10 may be provided as a wired interface such as IEEE (Institute of Electrical and Electronics Engineers) 1394 and USB (Universal Serial Bus). Alternatively, the external I / F 10 can be provided as a wireless interface using light or radio waves. That is, the external I / F 10 may be a wired or wireless interface.

The diaphragm 1b plays a role of adjusting the amount of incident light, and is driven and controlled by the diaphragm driver 1f so as to have a suitable diaphragm amount based on the detected diaphragm position and diaphragm shape. The optical block 1a also includes a filter that attenuates (adjusts) the amount of incident light, and the filter position is also driven and controlled by the optical block driver 1a.
With the above configuration, the CPU 2a determines the contrast of the pixel based on the image signal, generates the distance information of the focused pixel based on the determination result by the contrast determination unit, and sets the focused pixel and the distance information. Correspondingly stored in the RAM 2b, the focus position is changed, and at least one lens group provided separately from the lens group that changes the focus position is driven by the optical block driver 1e.

  FIG. 2 shows and describes an external configuration diagram of the digital camera when the imaging apparatus is applied to the digital camera. 2A is a perspective view of the digital camera viewed from the front, and FIG. 2B is a perspective view of the digital camera viewed from the rear. The digital camera 30 is provided with a lens 31, a shutter button 32, a menu button 33, an enter button 34, an exposure correction button 35, a touch panel 36, and a cross key 37. Buttons and the like are conceptually included in the operation unit 7.

FIG. 3 shows and describes the configuration of the optical system included in the optical block 1a.
As shown in FIG. 3, the optical system includes a positive first lens unit L1, a negative second lens unit L2, a positive third lens unit L3, and a positive fourth lens unit L4 in order from the object. The optical system is a zoom lens in which the first lens group L1 and the third lens group L3 are fixed, and the focal length is changed by moving the second lens group L2 and the fourth lens group L4.

  By moving the second lens unit L2 from the object side to the image plane side, zooming (magnification) from the Wide (wide angle) side to the Tele (telephoto) side is performed. From this viewpoint, the second lens unit L2 is also referred to as a zoom group. Further, by moving the fourth lens unit L4 in order to correct the imaging position that is shifted due to the movement of the second lens unit L2, the zooming operation is performed while maintaining the in-focus position. From this viewpoint, the fourth lens unit L4 is also referred to as a focus group.

  Separately, the fourth lens unit L4 is moved from the image plane side to the object side to focus from the Far (far view) side to the Near (near view) side. At this time, the moving range of the fourth lens unit L4 varies depending on the position of the second lens unit L2. That is, the moving range of the focus group changes for each zoom position.

  The optical system assumes that the principal ray is not parallel to the optical axis on the image side. That is, it is assumed that it is a non-telecentric optical system or an image side telecentric optical system (an optical system in which the optical axis and the principal ray are parallel on the image plane side). In general, the telecentric optical system refers to an optical system in which the entrance pupil or the exit pupil is in the focal plane of the optical system, and in particular, the case where the entrance pupil position coincides with the front focal position is referred to as an image side telecentric optical system.

  Even if the optical system is an object-side telecentric optical system (the optical axis and the principal ray are parallel on the object side), it is a both-side telecentric optical system (the principal ray is parallel to the optical axis on the object side and the image plane side). It doesn't matter. However, this is not necessary when performing focus control with the image pickup apparatus of this embodiment, and is rather unnecessary because it aims to suppress changes in field angle and subject image shape without using a telecentric optical system. You can say that.

  If the principal ray is not parallel to the optical axis when the focus group moves in the optical axis direction, the effective focal length changes to change the angle of view and the shape of the subject image. In the optical system employed by the imaging apparatus according to this embodiment, when focusing from the Far (distant view) side to the Near (near view) side by moving the fourth group from the image plane side to the object side, the effective focal length Becomes longer, the angle of view becomes narrower, and the subject image changes so as to appear larger.

  The flash ROM 2c or RAM 2b in FIG. 1 keeps the effective focal length constant according to the relationship between the movement amount of the focus group at each zoom position and the change amount of the effective focal length, as well as the movement range of the focus group at each zoom position. The amount of movement of the zoom group is stored. That is, the flash ROM 2c or the RAM 2b stores the amount by which the zoom group is moved in order to keep the effective focal length constant when the focus group is moved and to suppress the change in the angle of view and the shape change of the subject image. .

  FIG. 4 shows and describes the relationship between the zoom stroke and the focus stroke in the optical system of the imaging apparatus according to the first embodiment of the present invention. In this optical system, the focus movement range varies from infinity (∞) to the closest shooting distance (80 cm in this example) depending on the zoom position. That is, it is so-called electronic cam data, which is usually held in the RAM 2b, flash ROM 2c, etc. as electronic address data.

  At the wide-angle zoom position, the focus group is moved from infinity (∞) to the closest shooting distance (80 cm in this example) by moving the focus group at a position close to the image plane with a very short moving range. You can move the range.

  On the other hand, in the tele (zoom) side zoom position, if the focus group is close to the object side and is not moved within a moving range longer than the wide end, this is the distance from infinity (∞) to the closest shooting distance (this In the example, it is not possible to focus up to 80cm).

  In this optical system, it is possible to focus up to, for example, 1 cm on the Wide side (from the Wide end to a point slightly beyond Mid), but it is possible to guarantee the closest shooting distance over the entire zoom position. 80 cm. The numerical value of 80 cm is an example in the design matter, and the imaging and the acquisition of distance information according to the present embodiment are not limited to the numerical value of the shortest (closest) imaging distance of 80 cm.

  Next, FIG. 5 illustrates a method of associating the movement of the focus group with the movement of the zoom group in order to keep the effective focal length constant when the focus group is moved at each zoom position.

  By moving the focus group and the zoom group together along the characteristics of A1 to A7 (solid line), the focus position is maintained while keeping the effective focal length constant and suppressing the change in the angle of view / the change in the shape of the subject image. (Focus position / object plane position) can be changed.

  In particular, in the optical system employed by the imaging apparatus according to the present embodiment, when focusing from the Far (far view) side to the Near (near view) side by moving the fourth group from the image plane side to the object side, The effective focal length becomes longer, the angle of view becomes narrower, and the subject image changes so as to appear larger. Therefore, the positional relationship of each other is converted into address data in the flash ROM 2c or RAM 2b so that the zoom group is moved from the tele (telephoto) side to the wide (wide angle) side so as to cancel (compensate) the effective focal length that has become longer. I remember it.

  In FIG. 5, the movement of the focus group and the movement of the zoom group are shown by the characteristics A1 to A7 (solid line), but the table (data) holding method is not limited to this.

  For example, a focus position such as ∞ / 20m / 10m / 5m / 3m / 2m / 1.5m / 1.2m / 1m / 80cm starting from the point where the focus is at infinity (∞) at a certain zoom position (100mm) The position of the zoom group at is stored as address data (see Table 1).

  Such data is converted into address data and stored in the flash ROM 2c or RAM 2b within a range covering the entire zoom range (A1 to A7).

  Furthermore, the position of the focus group from the infinity (∞) to the shortest shooting distance and the position of the corresponding zoom group are stored as a table (data) starting from the distance at which focus was achieved during framing. Good.

  The position information that associates the movement of the focus group with the movement of the zoom group does not need to hold the positions of all the focus groups and the positions of the zoom group, and the flash ROM 2c (or RAM 2b) when moving in association with each other. It is also possible to interpolate the position information after reading the data stored in.

  That is, only by holding the data of A1 to A7, framing between A3 and A4, for example, can be performed by interpolating position information and performing focus control thereafter. By doing so, it is not necessary to store a large amount of position information, so that memory can be saved.

  Further, when obtaining distance information in units of pixels (or corresponding to pixels), it is possible to achieve both the correspondence between the distance information and the image with high accuracy and framing by a flexible zoom operation.

  In addition, information regarding a movable range in which the zoom group can be moved in association with the focus group is also stored in the flash ROM 2c (or RAM 2b), and the range in which the two groups can be moved in association with each other can be limited.

  At the position of A1 in this optical system (as shown in FIG. 4), if it is only the focus group, it can be sent up to 1 cm, but it exceeds the movable range of the zoom group that is moved to compensate for the effective focal length. Therefore, the movement of the focus group is limited to 80 cm. That is, the shortest shooting distance is set to 80 cm at this zoom position.

  At the positions A2 to A4, the zoom group can be moved so as to correspond to moving the focus group from infinity (∞) to 1 centimeter, and therefore the movement range of the focus group is not limited.

  Further, at the positions A5 to A7, the focus group cannot be sent closer than 80 cm. Therefore, at the zoom positions A5 to A7, the movement of the focus group is limited to infinity (∞) to 80 cm. That is, at the zoom position in this range, the shortest shooting distance is set to 80 cm.

  Since the movement of the focus group and the movement of the zoom group can be associated only in a narrower range at a position on the wide-angle side than A1, a narrower movement range (for example, the movement of the focus group is 2 m from infinity (∞). Limit).

  Similarly, even at a position on the telephoto side from A7, a narrower movement range (for example, movement of the focus group from 2 m to 80 cm) is limited.

  In order to enable natural imaging and distance information acquisition without making the user aware of this, in this imaging apparatus, the range in which the focus group and the zoom group can move in conjunction (that is, from infinity (∞) to 80 cm) ) Is limited between A1 and A7 to ensure the zooming range in the user operation. That is, the limit is set so that the zoom operation cannot be performed on the wide angle side from A1.

  Further, in the optical system employed by the imaging apparatus according to the present embodiment, the fourth lens unit L4 is moved from the image plane side to the object side to focus from the Far (far view) side to the Near (near view) side. In some cases, the effective focal length becomes longer, the angle of view becomes narrower, and the subject image changes so as to appear larger. Therefore, by moving the second lens unit L2 from the image plane side to the object side and performing zooming (magnification) from the Tele (telephoto) side to the Wide (wide angle) side, the effective focal length is shortened, Widen the angle of view and change it so that the subject image appears small. Thus, by moving the second lens unit L2 and the fourth lens unit L4 in association with each other, the effective focal length can be kept constant, the field angle can be kept constant, and the shape change of the subject image can be suppressed.

  In order to perform such an operation, when the fourth lens unit L4 moves from the image plane side to the object side, the second lens unit L2 must also be movable from the image plane side to the object side. Therefore, a zoom driving limit is set (between A1 and A7) at a position where the amount of movement of the second lens unit L2 necessary for correcting the change in the effective focal length due to the movement of the fourth lens unit L4 can be secured. . At this time, the focus drive is limited from infinity (∞) to 80 cm between A1 and A5 to A7, and is driven from infinity (∞) to 1 cm without limitation at other positions (A1 ′ to A5 ′). To do.

  If no limit is provided in advance, it is determined whether the second lens unit L2 is in a position having a sufficient movable range when the fourth lens unit L4 starts to move. If the second lens unit L2 is not in a position where the amount of movement of the second lens unit L2 necessary for correcting the change in effective focal length due to the movement of the fourth lens unit L4 is not a position, the second lens unit L2 can be secured. The amount of movement is secured by moving.

  That is, at the position of A1, when imaging and distance information acquisition are performed between infinity (∞) and 1 cm, the zoom group is outside the movable range of the zoom group, so the zoom group is moved to the position of A1 ′. . Then, the focus group is moved from infinity (∞) to 1 cm, and the zoom group is moved in conjunction with the focus group, thereby performing imaging and obtaining distance information.

  Further, at the position of A5, when imaging and distance information acquisition are performed between infinity (∞) and 1 cm, the focus group is outside the movable range of the focus group, so that the focus group can move to 1 cm. The zoom group is moved to the position of A5 ′. Then, the focus group is moved from infinity (∞) to 1 cm, and the zoom group is moved in conjunction with the focus group, thereby performing imaging and obtaining distance information.

  When these operations are performed, imaging and distance information acquisition are performed with a field angle setting different from zooming by a user operation. Therefore, when an attempt is made to capture and acquire distance information from infinity (∞) to 1 cm at the position of A1 or A5, a warning that “a depth map of up to 1 cm cannot be generated” is displayed on the LCD 9 To do. Thereby, zooming by a user operation may be promoted.

  Further, at the position of A1, it operates in a direction in which the angle of view becomes narrower. Therefore, a warning that “a depth map of up to 1 cm cannot be generated” is displayed on the LCD 9, and a frame indicating an angle of view corresponding to A 1 ′ is displayed on the screen of the LCD 9. Thereby, the user may be prompted to determine whether or not to change the zoom position.

  Next, with reference to a flowchart of FIG. 6, a processing procedure of imaging and distance information acquisition by the imaging device according to an embodiment of the present invention will be described. Part or all of this processing procedure also corresponds to the focus control method according to the present embodiment.

  The CPU 2a moves the fourth lens unit L4 from the image plane side to the object side, thereby changing the focus position from the Far (distant view) side to the Near (near view) side, and moving the second lens unit L2 to the fourth lens unit. In correspondence with the amount of movement of L4, the effective focal length (view angle / subject image) is moved from the image plane side to the object side so as to be kept constant (step S1).

  While changing the focus position in this way, the CPU 2a captures an image with the image sensor 1c, acquires images, and stores each image in the RAM 2b (step S2).

  The CPU 2a repeats steps S1 and S2 to acquire an image while changing the in-focus position from the Far (far view) side to the Near (near view) side, that is, from infinity (∞) to the shortest shooting distance. For example, an image is acquired for ∞ / 20m / 10m / 5m / 3m / 2m / 1.5m / 1.2m / 1m / 80cm and stored in the RAM 2b (step S3).

  Next, when the focus position change is completed (step S3 branches to Yes), the CPU 2a extracts only the focused pixel by contrast determination from each image stored in the RAM 2b (step S4), and the entire image is focused. The generated image is generated (step S5).

  When the CPU 2a determines the contrast in step S4, the CPU 2a stores the in-focus position (shooting distance) in association with the in-focus pixel in the RAM 2b, thereby storing the distance information (Depth Map) in units of pixels (or corresponding to the pixels). Is generated (step S6).

  The CPU 2a obtains the distance information as follows when the focused pixel is not obtained for the entire image in the contrast determination in step S4 (when the contrast detection is not successful). That is, for pixels for which focused pixels could not be obtained (hereinafter referred to as error pixels), if there are pixels that were able to obtain focused pixels on both sides close to each other, images obtained by acquiring these pixels are related to each other. The pixels at the error pixel positions are averaged. Thereby, the distance information is obtained by obtaining the pixel value of the error pixel and interpolating the distance information.

  The CPU 2a obtains the close in-focus pixel when there is no in-focus pixel on both sides of the error pixel (that is, the in-focus pixel is obtained only on one side). For the obtained image, the pixel at the position of the error pixel is substituted. Thereby, the pixel value and distance information of the error pixel are obtained.

  If in-focus pixels cannot be obtained by contrast judgment, the subject is often a flat wall with a low contrast or a dark image, so it is practical to use the above method without increasing the processing load. Obtain pixel values and distance information without any problems.

  In this way, the CPU 2a records the generated image and distance information (Depth Map) on the storage medium 5 via the medium I / F 5 (step S7). According to the above processing, when distance information is obtained in units of pixels (or corresponding to pixels), distance information can be associated with images with high accuracy.

Here, the processing procedure of FIG. 6 can be improved as follows.
Hereinafter, with reference to the flowchart of FIG. 7, another processing procedure of imaging and distance information acquisition by the imaging device according to the embodiment of the present invention will be described. Part or all of this processing procedure also corresponds to the focus control method according to the present embodiment.

  The CPU 2a moves the fourth lens unit L4 from the image plane side to the object side, thereby changing the focus position from the Far (distant view) side to the Near (near view) side, and moving the second lens unit L2 to the fourth lens unit. The effective focal length (view angle / subject image) is moved from the image plane side to the object side in correspondence with the amount of movement of L4 (step S11).

  Subsequently, the CPU 2a acquires images while changing the in-focus position, and stores each image in the RAM 2b (step S12). Then, the CPU 2a extracts only in-focus pixels from each stored image by contrast determination (step S13), generates an image in focus on the entire image, and stores it in the RAM 2b (step S14).

  When this contrast determination is performed, the CPU 2a stores the in-focus position (shooting distance) in the RAM 2b in association with the in-focus pixel, thereby generating distance information (Depth Map) in units of pixels (or corresponding to the pixels). (Step S15). Then, the CPU 2a acquires an image and stores it in the RAM 2b until focused pixels are obtained for the entire image (that is, all pixels constituting the image) by this contrast determination (step S16).

  The image and distance information (Depth Map) generated in steps S14 and S15 are not completed until a Yes determination is made in step S16. When step S16 is branched to Yes, the CPU 2a records the generated image and distance information (Depth Map) in the storage medium 6 via the medium I / F 5 (step S17). In this way, the processing ends with the number of times of imaging and the number of contrast determinations that are not wasted when imaging and distance information are acquired.

  The processing procedure in FIG. 6 can be changed as shown in FIG. That is, in the processing procedure of FIG. 8, the drive range is limited (limiter processing) at the initial initialization stage (step S21). Thus, control is performed so that both the focus group and the zoom group are appropriately driven within the movable range. The other processes in steps S22 to S28 are the same as those in steps S2 to S7 in FIG.

  Although the imaging apparatus according to the embodiment of the present invention has been described above, the direction in which the fourth lens group L4 and the second lens group L2 are driven is not limited to FIG.

  As shown in FIG. 9, the fourth lens unit L4 is driven from the Far (far view) side to the Near (near view) side, and the second lens unit L2 is driven from the Tele (telephoto) side to the Wide (wide angle) side. Also good. Alternatively, the fourth lens unit L4 may be driven from the Near (near view) side to the Far (far view) side, and the second lens unit L2 may be driven from the Wide (wide angle) side to the Tele (telephoto) side. In other words, it is needless to say that the operation may be reversed from that in FIG.

  Further, as a design matter of the optical system, for example, the change in the angle of view when the fourth lens unit L4 is driven from the Far (far view) side to the Near (near view) side is not limited to the above. When the optical axis and the principal ray are not parallel, the direction in which the angle of view changes depends on what angle is formed. In short, it is only necessary to control the zoom group to be driven so as to correct the change in the angle of view due to the driving of the focus group.

  Further, this embodiment is not limited to the four-group inner focus zoom lens optical system. Hereinafter, an improved example in which the fifth group inner focus zoom lens is applied will be described.

FIG. 10 shows a configuration example of a 5-group inner focus zoom lens.
As shown in FIG. 10, the optical system includes a positive first lens unit L1, a negative second lens unit L2, a positive third lens unit L3, a positive fourth lens unit L4, a positive unit in order from the object. Consists of a fifth lens unit L5. That is, in this optical system, the first lens group L1, the third lens group L3, and the fifth lens group L5 are fixed, and the zoom lens that changes the focal length by moving the second lens group L2 and the fourth lens group L4. It is a lens. Even in this optical system, the distance information and the image can be associated with high accuracy by using the above-described method relating to imaging and distance information acquisition.

FIG. 11 shows a configuration example of another 5-group inner focus zoom lens.
As shown in FIG. 11, the optical system includes, in order from the object, a positive first lens unit L1, a negative second lens unit L2, a positive third lens unit L3, a positive fourth lens unit L4, and a negative Consists of a fifth lens unit L5. That is, in this optical system, the first lens unit L1, the third lens unit L3, and the fifth lens unit L5 are fixed, and the focal length is changed by moving the second lens unit L2 and the fourth lens unit L4. This is a zoom lens. Even in this optical system, the distance information and the image can be associated with high accuracy by using the above-described method relating to imaging and distance information acquisition.

  Although not shown in FIGS. 3 and 9-11, as described above, the diaphragm 1b, the diaphragm driver 1f, the filter, the filter position detecting unit, the filter driving unit, and the like are arranged inside or behind the optical system of the optical block 1a. Even if it arrange | positions, it does not interfere in performing the imaging by the imaging device which concerns on this embodiment, and acquisition of distance information.

  In addition, an IR cut filter, a low-pass filter, and the like are generally provided in front of the image sensor 1c, but this also does not prevent the image capturing apparatus according to the present embodiment from performing image capturing and distance information acquisition. .

  For example, when an ND filter or an IR cut filter is taken in and out of the optical path, the optical path length changes. Therefore, in this case, when the optical filter is inserted into the optical path and when it is in the retracted state, the electronic cam data as shown in FIG. 4 and the focus as shown in FIG. Data indicating the movement direction and amount in which the group and the zoom group are associated with each other may be held in the RAM 2b or the like.

  When the focal length is varied by moving the optical element in and out of the optical axis or switching, it is necessary to hold the table as shown in FIGS. 4 and 5 in the RAM 2b or the like at each focal length. There is.

  Further, the method related to the imaging and the acquisition of distance information of the present proposal is not limited to the type of the lens (optical system). There are various focusing methods and zooming methods using a lens (optical system). Therefore, a preferred method will be described below.

Here, the following are known as focusing methods.
・ Full payout system
This is a method often used for single-focus lenses. A multi-threaded screw and a single-threaded screw are used, a key is attached, and the entire lens goes straight by rotating a ring with both intervening screws. ing.
・ Front ball feeding method
This is a method of focusing by changing the focal length of the lens group. In principle, it is a combination of two lenses, one with a plano-convex lens and a plano-concave lens. The rear group is fixed.
・ Inner focus method (inner focus / rear focus)
It is the same as the front-lens pay-out method in that the focal length is changed for focusing.
・ Floating method
This is a combination of the whole pay-out type and the inner focus type.

  Of these methods, the single-focal-lens total extension method changes the in-focus position by extending the entire optical system without changing the configuration of the entire optical system, but corrects the effective focal length when the entire optical system is extended. Since there is no means to do this, it is not possible to perform imaging and distance information acquisition by the imaging apparatus according to the present embodiment.

  In addition, even in the front lens payout method / inner focus method (inner focus / rear focus) in the single focus lens, there is no means for correcting the effective focal length when the front lens is extended, so that the imaging apparatus according to the present embodiment Imaging and distance information cannot be acquired.

  In the floating system for a single focus lens, the focusing position is changed by extending the entire optical system (lens), but the floating lens group is used as a means for correcting the effective focal length when the entire optical system is extended. Can do. That is, it can be said that the floating method is preferable for performing imaging and distance information acquisition by the imaging apparatus according to the present embodiment in a single focus lens.

  In the zoom lens, the entire extension system / front lens extension system is such that either the overall extension / front lens extension is a means for changing the in-focus position, that is, a means for changing the focal length of the optical system. 2 is a means for correcting a change in focal length when the zoom (magnification) means changes the focus position by b. Therefore, it is possible to perform imaging and distance information acquisition by the imaging apparatus according to the present embodiment.

  The inner focus method (inner focus / rear focus) in the zoom lens corresponds to the fourth group inner focus zoom lens in the present embodiment, so that the image pickup apparatus according to the present embodiment and the acquisition of distance information can be performed. it can.

  It is also possible to change the focal position by driving the inner focus group, and to correct the focal length change by the entire extension or the front lens extension.

  Although the zoom lens is not called a floating system, it has means for changing the in-focus position and means for correcting the effective focal length. Therefore, the imaging and distance information by the imaging apparatus according to the present embodiment is provided. Can be obtained.

  In addition to the above, various zoom methods such as two-group zoom have been disclosed and implemented. What kind of zoom method is used for imaging and distance information acquisition by the imaging apparatus according to the present embodiment? Even if there is, there is no problem.

  Further, in recent years, there has been a growing demand for higher magnification and smaller size of zoom lenses in small imaging devices such as digital cameras and digital video cameras. In this respect, the whole payout method and the front ball payout method are disadvantageous in reducing the size of the entire apparatus because the drive unit is large. Therefore, an inner focus zoom lens is preferable in the implementation of the present embodiment.

  According to the embodiment of the present invention described in detail above, the following effects are produced.

  That is, when the lens is driven, by driving at least one other group (including the entire payout and front ball payout as described above) together with the focus group, the focus position (focus position / It is possible to correct the focal length change when the focus position is changed. This makes it possible to suppress changes in the angle of view / changes in the shape of the subject image when the in-focus position is changed. Therefore, imaging is performed in units of pixels (or corresponding to pixels) by imaging at a plurality of in-focus positions. When obtaining the distance information, the distance information and the image can be associated with high accuracy.

  When the distance information is acquired by imaging at a plurality of in-focus positions, the distance information and the image can be associated with high accuracy even using a general (that is, non-telecentric) optical system.

  Even if a general (that is, non-telecentric) optical system is used, the distance information and the image can be correlated with high accuracy without using image processing such as coordinate transformation. The distance information can be associated with the image without increasing the processing load. Note that some microscopes / digital microscopes use non-telecentric optical systems and associate distance information with images by image processing, but these are also applicable.

  Even if a general (that is, non-telecentric) optical system is used, the distance information and the image can be associated with high accuracy, so that a small-sized imaging such as a digital camera or a digital video camera can be performed. Also in the apparatus, distance information can be obtained and utilized. Some microscopes / digital microscopes and the like use a telecentric optical system, but are also applicable to these.

  By limiting the driving range of the optical system so that driving for changing the in-focus position and driving of at least one other group can be performed, distance information and images can be associated with each other reliably. An imaging device that can be provided can be provided.

  When driving to change the in-focus position, it is determined whether it is at a position where at least one other group can be driven, and driving to a position where a driving range can be secured is ensured. An imaging apparatus capable of associating distance information with an image can be provided.

  The present invention is not limited to the above-described embodiment, and various improvements and modifications can be made without departing from the spirit of the present invention. For example, the present invention can be implemented as a program related to the processing described above and a recording medium that records the program.

It is a block diagram which shows the structure of the imaging device which employ | adopted the distance measuring device which concerns on one embodiment of this invention. (A) And (b) is a general | schematic block diagram of the imaging device which employ | adopted the distance measuring device which concerns on one embodiment of this invention. It is a figure explaining the structure and drive system of an imaging optical system. It is a figure which shows the general relationship between a zoom stroke and a focus stroke. It is a figure which shows the relationship between the zoom stroke and the focus stroke which the focus control method etc. which concern on one embodiment of this invention employ | adopt. It is a flowchart which shows the process sequence by the imaging device which employ | adopted the distance measuring device which concerns on one embodiment of this invention. It is a flowchart which shows the other process sequence by the imaging device which employ | adopted the distance measuring device which concerns on one embodiment of this invention. It is a flowchart which shows the further another processing procedure by the imaging device which employ | adopted the distance measuring device which concerns on one embodiment of this invention. It is a figure explaining the structure and drive system of an imaging optical system. It is a figure explaining the other structure and drive system of an imaging optical system. It is a figure explaining the further another structure and drive system of an imaging optical system.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Camera part, 1a ... Optical block, 1b ... Aperture, 1c ... Imaging device, 1d ... A / D conversion circuit, 1e ... Optical block driver, 1f ... Aperture driver, 1g ... Imaging device driver, 1h ... Timing Generation circuit, 1i ... detection unit, 1j ... drive unit, 1k ... blur detection unit, 2 ... control unit, 2a ... CPU, 2b ... RAM, 2c ... flash ROM, 2d ... clock circuit, 2e ... system bus, 3 ... camera DSP, 3a ... AF / AE / AWB, 3b ... compression / decompression unit, 3c ... SDRAM controller, 4 ... SDRAM, 5 ... media I / F, 6 ... recording medium, 7 ... operating unit, 8 ... LCD controller, 9 ... LCD, 10 ... External I / F

Claims (14)

Determining a pixel contrast based on an image signal;
Generating the distance information of the focused pixel based on the determination result of the contrast determination, and storing the focused pixel and the distance information in association with each other;
While changing the in-focus position, at least one second lens group provided separately from the first lens group for changing the in-focus position is used to change the amount of movement of the first lens group and the effective focal length. And a step of driving according to an amount of movement for keeping the effective focal length constant according to the relationship with the amount of change. The focus control method according to claim 1, further comprising a step of driving the second lens group so as to correct a change in an effective focal length that is generated when driving to change the focus position. The focus control method according to claim 1, further comprising a step of driving the second lens group so that an angle of view is constant when driving to change the focus position. The focus control method according to claim 1, further comprising a step of limiting a driving range so that driving for changing the in-focus position and driving of the second lens group can be performed. 2. The method of driving to a position where a driving range can be secured by determining whether the second lens group is in a position where driving can be performed when driving for changing the in-focus position is performed. The focus control method described in 1. Contrast determination means for determining the contrast of a pixel based on an image signal;
Based on the determination result by the contrast determination unit, the distance information of the focused pixel is generated, and the distance information generating unit that stores the focused pixel and the distance information in association with each other;
While changing the in-focus position, at least one second lens group provided separately from the first lens group for changing the in-focus position is used to change the amount of movement of the first lens group and the effective focal length. A distance measuring device comprising: lens driving means for driving according to an amount of movement for keeping the effective focal length constant according to the relationship with the amount of change. The distance measuring device according to claim 6, wherein the lens driving unit drives the second lens group so as to correct a change in an effective focal length that is generated when driving to change the in-focus position. The distance measuring device according to claim 6, wherein the lens driving unit drives the second lens group so that an angle of view becomes constant when driving to change the in-focus position. The distance measuring device according to claim 6, wherein the lens driving unit limits a driving range so that driving for changing the in-focus position and driving of the second lens group can be performed. The lens driving means drives to a position where a driving range can be ensured by determining whether the second lens group is in a position where the second lens group can be driven when driving for changing the in-focus position. The distance measuring device according to claim 6. An imaging optical system;
An image sensor disposed behind the imaging optical system;
Lens driving means for driving the imaging optical system;
Contrast determination means for extracting pixels based on an image signal output from the image pickup device in accordance with driving of the imaging optical system by the lens driving means;
Image generating means for generating an image of a subject by combining the focused pixels extracted by the contrast determining means;
Distance information generating means for storing the in-focus pixel extracted by the contrast determining means and information on the shooting distance at which the imaging optical system is focused by the lens driving means;
The lens driving means changes the in-focus position, and at least one other lens group provided separately from the in-focus position changing lens group for changing the in-focus position is used as the in-focus position changing lens. An imaging device that is driven according to a movement amount for keeping the effective focal length constant according to a relationship between a movement amount of the group and a change amount of the effective focal length. The imaging optical system includes a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group in order from the object, and the first lens group and the third lens group. The imaging apparatus according to claim 11, wherein the zoom lens is fixed and changes a focal length by moving the second lens group and the fourth lens group. The imaging optical system includes, in order from the object, a positive first lens group, a negative second lens group, a positive third lens group, a positive fourth lens group, and a positive fifth lens group, and the first lens 12. The zoom lens according to claim 11, wherein the zoom lens is configured such that a group, the third lens group, and the fifth lens group are fixed, and a focal length is changed by moving the second lens group and the fourth lens group. Imaging device. The imaging optical system includes, in order from the object, a positive first lens group, a negative second lens group, a positive third lens group, a positive fourth lens group, and a negative fifth lens group, and the first lens 12. The zoom lens according to claim 11, wherein the zoom lens is configured such that a group, the third lens group, and the fifth lens group are fixed, and a focal length is changed by moving the second lens group and the fourth lens group. Imaging device.

Images