JP2010258616A - Video camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a video camera which suppresses a deterioration in image quality when reproducing a plurality of recorded field images in a period shorter than a recording period. <P>SOLUTION: An image sensor 16 has an imaging surface for catching a field through a focus lens 14 and generates a field image. An I/F 38 records the field image generated by the image sensor 16 in a recording medium 40 in each designated period. A CPU 26 adjusts a distance from the focus lens 14 to the imaging surface under a continuous AF task each time motion occurs in the field. The CPU 26 also controls a response characteristic of a distance adjustment operation so as to be decreased more as the length of the designated period is increased under a setting control task. The deterioration in image quality when reproducing the plurality of recorded field images in the period shorter than the recording period, is suppressed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a video camera, and more particularly to a video camera that records an object scene image generated by an imaging unit on a recording medium at a specified period.

  An example of this type of camera is disclosed in Patent Document 1. According to this background art, when the interval shooting mode is selected, the scene is shot every minute, for example. Imaging parameters such as focus are set to one of a locked state and an unlocked state. While the imaging parameter value set in the locked state is common for each shooting, the imaging parameter value set in the unlocked state may be different for each shooting.

  When the designated number of times of shooting is completed, the object scene image of the number of frames corresponding to the designated number of times is stored in the movie file, and the cycle information indicating a cycle shorter than the recording cycle (= 1/15 seconds, for example) is described in the movie file Is done. The object scene image stored in the moving image file is reproduced in a cycle according to the cycle information described in the moving image file.

JP 2001-298893 A

  In the background art, the imaging parameter can be set only in one of a locked state and an unlocked state. For this reason, when the recorded object scene image is reproduced at a cycle shorter than the recording cycle, the image quality may be noticeably deteriorated.

  Therefore, a main object of the present invention is to provide a video camera capable of suppressing deterioration in image quality when a plurality of recorded scene images are reproduced with a cycle shorter than the recording cycle.

  The video camera according to the present invention (10: reference numeral corresponding to the embodiment; hereinafter the same) has an imaging surface for capturing the object scene through the focus lens (12), and generates an object image (16). Recording means (S11, S27) for recording the object scene image generated by the image pickup means for each specified period; adjustment means (S85) for adjusting the distance from the focus lens to the image pickup surface every time the object scene moves , S87), and control means (S41, S47, S51) for controlling the response characteristics of the adjusting means so as to decrease as the length of the designated period increases.

  Preferably, there is further provided clipping means (50) for cutting out a scene image belonging to the specified area among the scene images generated by the imaging means, and the adjustment means is based on the scene image cut out by the clipping means. The parameter that executes the adjustment process and defines the response characteristic of the adjustment means includes the size of the designated area.

  Preferably, the adjusting means determines whether the duration of the movement that has occurred in the object scene has reached a threshold value (S167), and the determination result of the determining means is a positive result from a negative result Including a starting means (S169) for starting the distance adjusting operation when updated, and a parameter defining a response characteristic of the adjusting means includes a threshold value.

  Preferably, the adjustment means includes a detection means (S75) for detecting a high-frequency component of the object scene image generated by the imaging means for the distance adjustment operation, and the parameter defining the response characteristic of the adjustment means activates the detection means. Including the waiting time until

  Preferably, setting means (28m) for setting the designated period to the first period corresponding to the first recording mode and setting the designated period to a second period longer than the first period corresponding to the second recording mode Is further provided.

  An imaging control program according to the present invention is provided in a processor (26) of a video camera (10) having an imaging surface for capturing an object scene through a focus lens (12) and including an imaging means (16) for generating an object scene image. A recording step (S11, S27) for recording the scene image generated by the imaging means for each specified period, and an adjustment step (S85) for adjusting the distance from the focus lens to the imaging surface every time a motion occurs in the scene. , S87) and a control step (S41, S47, S51) for controlling the response characteristics of the adjustment step so as to decrease as the length of the designated period increases.

  The imaging control method according to the present invention is an imaging control executed by a video camera (10) having an imaging surface for capturing an object scene through a focus lens (12) and including an imaging means (16) for generating an object scene image. A recording step (S11, S27) for recording an object scene image generated by an image pickup means for each specified period, and adjusting a distance from a focus lens to an image pickup surface each time a motion occurs in the object scene An adjustment step (S85, S87) and a control step (S41, S47, S51) for controlling the response characteristic of the adjustment step so as to decrease as the length of the designated period increases are provided.

  According to this invention, the response characteristic of the adjusting means is reduced as the length of the designated period increases. Therefore, the fluctuation amount of the distance from the focus lens to the imaging surface due to the movement of the object field becomes smaller as the recording cycle becomes longer. That is, when a slight motion or a temporary motion occurs in the object scene, the distance variation when the recording cycle is long is smaller than the distance variation when the recording cycle is short. As a result, it is possible to suppress deterioration in image quality when a plurality of recorded scene images are reproduced with a cycle shorter than the recording cycle.

  The above object, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

It is a block diagram which shows the basic composition of this invention. It is a block diagram which shows the structure of one Example of this invention. (A) is a timing chart showing an example of the recording operation in the normal mode, and (B) is a timing chart showing an example of the recording operation in the interval mode. It is an illustration figure which shows an example of the structure of the moving image file produced on a recording medium. It is an illustration figure which shows an example of the allocation state of the evaluation area and AF area in an imaging surface. FIG. 3 is a block diagram illustrating an example of a configuration of an AF evaluation circuit applied to the embodiment in FIG. 2. 6 is a graph showing an example of frequency characteristics indicated by the HPF of the embodiment. It is a graph which shows an example of the change of the focus evaluation value with respect to a lens position. It is a graph which shows an example of the change of the relative ratio with respect to a lens position. It is an illustration figure which shows an example of operation | movement of the focus lens at the time of direction determination. It is a flowchart which shows a part of operation | movement of CPU applied to the FIG. 2 Example. It is a flowchart which shows a part of other operation | movement of CPU applied to the FIG. 2 Example. FIG. 11 is a flowchart showing still another portion of behavior of the CPU applied to the embodiment in FIG. 2; FIG. 10 is a flowchart showing yet another portion of behavior of the CPU applied to the embodiment in FIG. 2; It is a flowchart which shows a part of other operation | movement of CPU applied to the FIG. 2 Example. FIG. 11 is a flowchart showing still another portion of behavior of the CPU applied to the embodiment in FIG. 2; FIG. 10 is a flowchart showing yet another portion of behavior of the CPU applied to the embodiment in FIG. 2; It is a flowchart which shows a part of other operation | movement of CPU applied to the FIG. 2 Example. FIG. 11 is a flowchart showing still another portion of behavior of the CPU applied to the embodiment in FIG. 2; FIG. 10 is a flowchart showing yet another portion of behavior of the CPU applied to the embodiment in FIG. 2; It is a flowchart which shows a part of other operation | movement of CPU applied to the FIG. 2 Example. FIG. 11 is a flowchart showing still another portion of behavior of the CPU applied to the embodiment in FIG. 2; FIG. 10 is a flowchart showing yet another portion of behavior of the CPU applied to the embodiment in FIG. 2; It is an illustration figure which shows another example of operation | movement of the focus lens at the time of direction determination.

Embodiments of the present invention will be described below with reference to the drawings.
[Basic configuration]

  Referring to FIG. 1, the video camera of the present invention is basically configured as follows. The imaging means 2 has an imaging surface that captures the scene through the focus lens 1 and generates a scene image. The recording unit 3 records the object scene image generated by the imaging unit 2 for each designated period. The adjusting means 4 adjusts the distance from the focus lens 1 to the imaging surface every time a motion occurs in the object scene. The control means 5 controls the response characteristic of the adjustment means 4 so as to decrease as the length of the designated period increases.

By reducing the response characteristic of the adjusting unit as the length of the designated period increases, the amount of fluctuation in the distance from the focus lens 1 to the imaging surface due to the movement of the object field becomes smaller as the recording period becomes longer. That is, when a slight motion or a temporary motion occurs in the object scene, the distance variation when the recording cycle is long is smaller than the distance variation when the recording cycle is short. As a result, it is possible to suppress deterioration in image quality when a plurality of recorded scene images are reproduced with a cycle shorter than the recording cycle.
[Example]

  Referring to FIG. 2, the video camera 10 of this embodiment includes a zoom lens 12 and a focus lens 14 driven by drivers 18a and 18b, respectively. The optical image of the object scene is irradiated on the imaging surface of the image sensor 16 through the zoom lens 12 and the focus lens 14 and subjected to photoelectric conversion. As a result, charges representing the object scene image are generated on the imaging surface.

  When the power is turned on, the CPU 26 activates the driver 18c under the imaging task for moving image capture processing. In response to the vertical synchronization signal Vsync generated every 1/60 seconds, the driver 18c exposes the imaging surface and reads out the charges generated on the imaging surface in a raster scanning manner. From the image sensor 16, raw image data representing the object scene is output at a frame rate of 60 fps.

  The signal processing circuit 20 performs processing such as white balance adjustment, color separation, and YUV conversion on the raw image data output from the image sensor 16, and the created YUV format image data is sent to the SDRAM 32 through the memory control circuit 30. Write. The LCD driver 34 reads the image data stored in the SDRAM 32 through the memory control circuit 30 and drives the LCD monitor 36 based on the read image data. As a result, a real-time moving image (through image) of the object scene is displayed on the monitor screen.

  The recording mode is set to either the normal mode or the interval mode by operating the mode key 28m. Referring to FIGS. 3A and 3B, the normal mode is a mode in which image data is recorded at a rate of 1 frame per 1/60 seconds, and the interval mode is, for example, at a rate of 1 frame per 5 seconds. In this mode, image data is recorded. Note that the recording cycle in the interval mode can be adjusted in a range exceeding 1/60 seconds.

  In both the normal mode and the interval mode, a moving image file having the structure shown in FIG. 4 is created, and 1/60 second reproduction period information is described in the file header. Therefore, the image data stored in the moving image file is reproduced at a frame rate of 60 fps regardless of the mode.

  When a recording start operation is performed toward the key input device 28 with the normal mode set, the CPU 26 instructs the I / F 38 to create and open a file. The I / F 38 newly creates a moving image file in the recording medium 40 and opens the created moving image file.

  Subsequently, the CPU 26 instructs the I / F 38 to execute the recording process every time the vertical synchronization signal Vsync is generated. The I / F 38 reads out one frame of image data stored in the SDRAM 32 through the memory control circuit 30 and writes the read image data into a moving image file in a compressed state. When a recording end operation is performed toward the key input device 28, the CPU 286 is instructed to close the file to the I / F 38. The I / F 38 stops reading the image data and closes the moving image file in the open state.

  When a recording start operation is performed with the interval mode set, the CPU 26 instructs the I / F 38 to create and open a file, as described above. As a result, a new moving image file is prepared in the recording medium 40 in an open state. Subsequently, the CPU 38 instructs the I / F 38 to execute the recording process every time the recording cycle comes. Image data is read from the SDRAM 32 at a rate of 1 frame per 5 seconds and written to an open moving image file. When the recording end operation is performed, the CPU 26 instructs the I / F 38 to close the file. As a result, reading of the image data is stopped and the moving image file in the open state is closed.

  When the zoom operation is executed by the key input device 28, the CPU 26 moves the zoom lens 12 in the optical axis direction under the zoom & AE control task. As a result, the magnification of the through image displayed on the LCD monitor 36 changes.

  Referring to FIG. 5, an evaluation area EVA is allocated at the center of the imaging surface. The evaluation area EVA is divided into 16 parts in each of the vertical direction and the horizontal direction. Therefore, the evaluation area EVA corresponds to a set of a total of 256 divided areas.

  The AE evaluation circuit 22 defines the entire evaluation area EVA as an AE area, and integrates Y data belonging to the AE area among Y data output from the signal processing circuit 20 in response to the vertical synchronization signal Vsync. . The integrated value is output from the AE evaluation circuit 22 as an AE evaluation value every time the vertical synchronization signal Vsync is generated.

  The CPU 26 repeatedly captures the AE evaluation value output from the AE evaluation circuit 24 under the zoom & AE control task, and adjusts the exposure amount of the image sensor 16 based on the captured AE evaluation value. As a result, the brightness of the through image displayed on the LCD monitor 36 is appropriately adjusted.

  Referring to FIG. 5 again, areas F_L, F_M, and F_S having different sizes are assigned to the center of the imaging surface. The size of the area F_L is the same as the size of the evaluation area EVA, the size of the area F_M is smaller than the size of the area F_L, and the size of the area F_S is smaller than the size of the area F_M.

  Under the AF setting control task, the CPU 26 defines any one of such areas F_L, F_M, and F_S as an AF area. Specifically, in the period before the recording start operation and the period after the recording end operation, the area F_M is defined as the AF area. When a recording start operation is performed with the interval mode selected, the area F_L is defined as the AF area.

  When a recording start operation is performed in a state where the normal mode is selected, the definition of the AF area is changed depending on whether or not a zoom operation is performed or whether or not a pan / tilt operation is performed on the imaging surface. That is, the AF area is changed from the area F_M to the area F_S during the zoom operation period, and is changed from the area F_M to the area F_L during the pan / tilt period of the imaging surface.

  The AF evaluation circuit 24 cuts out a part of the Y data belonging to the AF area thus defined from the output of the signal processing circuit 20, and among the cut out Y data, the frequency component higher than the cutoff frequency CF_L and the cutoff frequency CF_H Are individually integrated in response to the vertical synchronization signal Vsync.

  An integrated value of frequency components exceeding the cutoff frequency CF_L is output from the AF evaluation circuit 24 as a focus evaluation value AF_L. The integral value of the frequency component exceeding the cutoff frequency CF_H is output from the AF evaluation circuit 24 as the focus evaluation value AF_H.

  The CPU 26 captures the focus evaluation values AF_L and AF_H output in this way under a continuous AF task, and continuously adjusts the position of the focus lens 12 based on the captured focus evaluation values AF_L and AF_H.

  The AF evaluation circuit 24 is configured as shown in FIG. The Y data output from the signal processing circuit 20 is given to the clipping circuit 50. The cutout circuit 50 cuts out Y data belonging to the AF area from the given Y data, and inputs the cut out Y data to the HPFs 52a and 52b. The HPF 52a extracts a frequency component that exceeds the cutoff frequency CF_L from the input Y data, and the HPF 52b extracts a frequency component that exceeds the cutoff frequency CF_H from the input Y data.

  The frequency component extracted by the HPF 52a is integrated by the integration circuit 54a every time the vertical synchronization signal Vsync is generated. The frequency component extracted by the HPF 52b is also integrated by the integrating circuit 54b every time the vertical synchronization signal Vsync is generated. As a result, the focus evaluation value AF_L is output from the integration circuit 54a, and the focus evaluation value AF_H is output from the integration circuit 54b.

  Referring to FIG. 7, HPF 52a shows a frequency characteristic corresponding to curve Kf_L, and HPF 52b shows a frequency characteristic corresponding to curve Kf_H. Therefore, when the focus evaluation value AF_L draws the curve Cf_L shown in FIG. 8 with respect to the position of the focus lens 14, the focus evaluation value AF_H draws the curve Cf_H shown in FIG. The change in Cf_H with respect to, that is, the relative ratio between the focus evaluation values AF_L and AF_H is represented by a curve CV1 shown in FIG.

  The continuous AF task is roughly composed of direction determination processing, search processing, and monitoring processing. The direction determination process is a process for specifying the direction in which the focal point exists, that is, the in-focus direction. The search process is a process of searching for a focal point by moving the focus lens 14 in the specified in-focus direction. The monitoring process is a process for monitoring whether or not a motion has occurred in the object scene.

The focus evaluation values AF_L and AF_H are repeatedly acquired from the AF evaluation circuit 24 independently of these processes, and are referred to for the relative ratio RT calculation process according to Equation 1. The focus evaluation values AF_L and AF_H and the relative ratio RT are referred to as necessary in each of the direction determination process, the search process, and the monitoring process.
[Equation 1]

  RT = AF_H / AF_L

  In the direction determination process, the movement amount of the focus lens 14 is set to “W_S”, and the movement direction of the focus lens 14 is reversed every time the vertical synchronization signal Vsync is generated twice. As a result, the focus lens 14 is displaced between the three points of the closest position, the center position, and the infinite position in the manner shown in FIG.

  The focus evaluation value AF_H detected when the focus lens 14 is disposed at the close side position is set in the close side register R1. Further, the focus evaluation value AF_H detected when the focus lens 14 is disposed at the center position is set in the center register R2. Further, the focus evaluation value AF_H detected when the focus lens 14 is disposed at the infinite side position is set in the infinite side register R3.

  The magnitude relationship between the focus evaluation values AF_H set in the near side register R1, the center register R2, and the infinite side register R3 is determined every time the focus lens 14 is displaced in the designated direction, and the count value of the vertex counter C1 is determined according to the determination result. Is updated.

  The vertex counter C1 is incremented when the focus evaluation value AF_H set in the central register R2 exceeds both the focus evaluation value AF_H set in the closest register R1 and the focus evaluation value AF_H set in the infinite register R3. When this condition is not satisfied, “0” is set.

  Therefore, the vertex counter C1 is incremented when the focus lens 14 is finely moved near the focal point, and maintains “0” when the focus lens 14 is finely moved at a position away from the focal point. When the count value of the vertex counter C1 exceeds the threshold value A, the focus lens 14 is considered to be in focus, and the direction determination process is terminated and the monitoring process is started.

  In the direction determination process, in parallel with the register setting process and the update process of the vertex counter C1, the focus evaluation value AF_H acquired in the previous frame (previous focus evaluation value AF_H) and the focus evaluation value AF_H acquired in the current frame. A magnitude relationship with (current focus evaluation value AF_H) is determined.

  This determination process is also executed each time the focus lens 14 is displaced in the designated direction. If the numerical value tends to increase toward the infinite direction, the direction counter C2 is incremented. If the numerical value tends to increase toward the closest direction, the direction counter C2 is decremented.

  When the count value of the vertex counter C1 indicates “0”, such a count value of the direction counter C2 is noticed. When the count value of the direction counter C2 exceeds the threshold B, the infinite direction is determined as the in-focus direction. On the other hand, when the count value of the direction counter C2 falls below the threshold “−B”, the closest direction is determined as the in-focus direction. When the in-focus direction is determined in this way, the direction determination process is ended, and the search process is started. Note that the direction in which the distance from the focus lens 14 to the imaging surface increases is the closest direction, and the direction in which the distance from the focus lens 14 to the imaging surface decreases is the infinite direction.

  In the search process, the focus lens 14 is moved in the determined in-focus direction, and the maximum value of the focus evaluation value AF_H detected by the AF evaluation circuit 24 is set in the maximum value register R4. The down counter C4 is set to “0” in response to the update of the maximum value register R4, and is incremented every time the focus evaluation value AF_H detected thereafter falls below the set value of the maximum value register R4. When the count value of the down counter C4 exceeds the threshold value C, the focus lens 14 is considered to have exceeded the focal point. The moving direction of the focus lens 14 is reversed, and the focus lens 14 is disposed at the focal point.

  In the monitoring process, it is determined with reference to the relative ratio RT or the focus evaluation value AF_H whether or not a motion has occurred in the object scene. This determination process is executed every time the vertical synchronization signal Vsync is generated. The monitoring counter C5 is incremented when the determination result is affirmative, and is set to “0” when the determination result is negative. When the count value of the monitoring counter C5 exceeds the monitoring time SVT, the direction determination process is restarted after the standby time WT has elapsed.

  The monitoring time SVT and the standby time WT are adjusted as follows under the AF setting control task. That is, in the period from the recording start operation to the recording end operation under the interval mode, the time Tsv_L is set as the monitoring time SVT, and the time Twt_L is set as the standby time WT. In other periods, the time Tsv_S is set as the monitoring time SVT, and the time Twt_S is set as the standby time WT. Here, the time Tsv_S is shorter than the time Tsv_L, and the time Twt_S is shorter than the time Twt_L. The monitoring time SVT is based on the number of times the vertical synchronization signal Vsync is generated.

  The CPU 26 includes an imaging task shown in FIGS. 11 to 12, a zoom & AE control task shown in FIG. 13, an AF setting control task shown in FIGS. 14 to 15, and a continuous AF processing task shown in FIGS. Run multiple tasks in parallel. Note that control programs corresponding to these tasks are stored in the flash memory 46.

  Referring to FIG. 11, in step S1, a moving image capturing process is executed. As a result, a through image representing the scene is displayed on the LCD monitor 36. In step S3, it is determined whether or not a recording start operation has been performed. In step S5, it is determined whether the recording mode is set to the normal mode or the interval mode. If the recording mode is set to the normal mode, the process proceeds to step S7, and if the recording mode is set to the interval mode, the process proceeds to step S17.

  In step S7, the I / F 38 is instructed to create and open a file. As a result, a moving image file is newly created in the recording medium 40, and the created moving image file is opened. In step S9, it is determined whether or not the vertical synchronization signal Vsync is generated. When the determination result is updated from NO to YES, the I / F 38 is commanded to execute the recording process in step S11. The I / F 38 reads out one frame of image data stored in the SDRAM 32 through the memory control circuit 30 and writes the read image data into a moving image file in a compressed state.

  In step S13, it is determined whether or not a recording end operation has been performed. If the determination result is NO, the process returns to step S9. If the determination result is YES, the I / F 38 is instructed to close the file. Accordingly, the process of step S11 is repeatedly executed until a recording end operation is performed, whereby a plurality of frames of image data are accumulated in the moving image file. When the recording end operation is performed, the moving image file in the open state is closed. When the process of step S15 is completed, the process returns to step S3.

  In step S17, processing similar to that in step S7 is executed, and in step S19, the recording cycle is set to 5 seconds, for example. In step S21, it is determined whether or not a recording end operation has been performed. In step S23, it is determined whether or not a recording cycle has come. If “YES” in the step S23, the same process as the step S11 is executed in a step S27, and then the process returns to the step S21. If “YES” in the step S21, the same process as the step S15 is executed in a step S25, and then the process returns to the step S3.

  Referring to FIG. 13, in step S31, it is determined whether or not a zoom operation has been performed. In step S33, it is determined whether or not a vertical synchronization signal Vsync has been generated. If “YES” in the step S31, the zoom lens 12 is moved in the optical axis direction in a step S35, and thereafter, the process returns to the step S31. If “YES” in the step S33, exposure adjustment based on the AE evaluation value is performed in a step S37, and thereafter, the process returns to the step S31.

  Referring to FIG. 14, in step S41, area F_M is set as an AF area, time Tsv_S is set as monitoring time SVT, and time Twt_S is set as standby time WT. When the recording start operation is performed, YES is determined in step S43, and it is determined in step S45 whether the recording mode is set to the normal mode or the interval mode. If the recording mode is set to the normal mode, the process proceeds to step S47, and if the recording mode is set to the interval mode, the process proceeds to step S53.

  In step S47, area F_L is set as an AF area, time Tsv_L is set as monitoring time SVT, and time Twt_L is set as standby time WT. In a succeeding step S49, it is determined whether or not a recording end operation has been performed. When the determination result is updated from NO to YES, in step S51, the same process as in step S41 described above is performed, and then the process returns to step S43.

  In step S53, it is determined whether or not the zoom operation is being performed. In step S55, it is determined whether or not the imaging surface is being panned / tilted. If “YES” in the step S53, the process proceeds to a step S57 to set the area F_S as an AF area. If “YES” in the step S55, the process proceeds to a step S59 to set the area F_L as an AF area. If both step S53 and S55 are NO, area F_M is set as an AF area in step S61. When the process of step S57, S59 or S61 is completed, it is determined in step S63 whether or not a recording end operation has been performed. If a determination result is NO, it will return to Step S53, and if a determination result is YES, it will transfer to Step S51.

  Referring to FIG. 16, an initialization process is executed in step S71. The operation mode is set to the direction determination mode, and the count values of the vertex counter C1, the direction counter C2, and the execution number counter C3 are set to “0”. The lens movement amount is set to “0”.

  When the vertical synchronization signal Vsync is generated, YES is determined in step S73, and focus evaluation values AF_L and AF_H are acquired from the AF evaluation circuit 24 in step S75. In step S77, the relative ratio RT is calculated according to the above equation 1. In step S79, the focus lens 14 is moved in the setting direction by the set lens movement amount. At the time when the first process is executed, the lens movement amount is “0” and the movement direction is undetermined. Accordingly, the focus lens 14 continues to stop at the current position.

  In step S81, it is determined whether or not the current operation mode is the direction determination mode. In step S83, it is determined whether or not the operation mode is the search mode. If YES in step S81, a direction determination process is executed in step S85. If YES in step S83, a search process is executed in step S87. If NO in step S83, a monitoring process is executed in step S89. . When the process of step S85, S87 or S89 is completed, the process returns to step S73.

  The direction determination process in step S85 shown in FIG. 17 is executed according to a subroutine shown in FIGS. First, the lens movement amount is set to “W_S” in step S90, and it is determined in step S91 whether or not the execution number counter C3 is “0”. If the determination result is YES, the process proceeds to step S93, and the moving direction of the focus lens 14 is set to the closest direction. Subsequently, the current focus evaluation value AF_H is saved as the previous focus evaluation value AF_H in step S95, and the execution number counter C3 is incremented in step S97. In step S99, the current focus evaluation value AF_H is set in the central register R2, and the near side register R1 and the infinite side register R3 are cleared. When the process of step S99 is completed, the process returns to the upper layer routine.

  If NO is determined in the step S91, it is determined in a step S101 whether or not the count value of the execution number counter C3 is “3” or more. If the determination result is NO, the process proceeds to step S113, and if the determination result is YES, the process proceeds to step S103.

  In step S103, it is determined whether or not the set value of the central register R2 is larger than either the set value of the infinite register R1 or the close register R3. If the determination result is YES, the focus lens 14 is considered to be present in the vicinity of the in-focus position, and the vertex counter C1 is incremented in step S105. On the other hand, if the determination result is NO, the focus lens 14 is considered to be present at a position away from the in-focus position, and the vertex counter C1 is set to “0” in step S107. When the process of step S105 is completed, the process proceeds to step S109. When the process of step S107 is completed, the process proceeds to step S113.

  In step S109, it is determined whether or not the count value of the vertex counter C1 exceeds the threshold A. If the determination result is YES, the process proceeds to step S111. If the determination result is NO, the process proceeds to step S113. In step S111, the operation mode is set to the monitoring mode, and the monitoring counter is set to “0”. When the process of step S111 is completed, the process returns to the upper-level routine.

  In step S113, the direction counter C2 is incremented or decremented with reference to the magnitude relationship between the current focus evaluation value AF_H and the previous focus evaluation value AF_H.

  The direction counter C2 indicates that the current movement direction is an infinite direction and the current focus evaluation value AF_H exceeds the previous focus evaluation value AF_H, or the current movement direction is the closest direction and the current focus evaluation value AF_H is the previous focus evaluation value AF_H. Incremented when:

  The direction counter C2 also determines whether the current movement direction is an infinite direction and the current focus evaluation value AF_H is less than or equal to the previous focus evaluation value AF_H, or the current movement direction is the closest direction and the current focus evaluation value AF_H is the previous focus evaluation. It is decremented when it exceeds the value AF_H.

  When the process of step S113 is completed, it is determined in step S115 whether or not the count value of the direction counter C2 exceeds the threshold value B, and whether or not the count value of the direction counter C2 is less than the threshold value “−B” is determined in step S1117. Determine.

  If “YES” is determined in the step S115, the infinite direction is regarded as the in-focus direction, and the moving direction is set to the infinite direction in a step S119. If “YES” is determined in the step S117, the close direction is regarded as the in-focus direction, and the moving direction is set to the close direction in a step S121. When the process of step S119 or S121 is completed, the process proceeds to step S123. In step S123, the operation mode is set to the search mode, the down counter C4 is set to “0”, and the maximum value register R4 is cleared. When the process of step S123 is completed, the process returns to the upper layer routine.

  If both steps S115 and S117 are NO, the process proceeds to step S125, and the current focus evaluation value AF_H is saved as the previous focus evaluation value AF_H. When the saving process is completed, the execution number counter C3 is incremented in step S127, and it is determined in step S129 whether or not the reversal timing of the moving direction has come. If the determination result is NO, the process proceeds to step S133 as it is, and if the determination result is YES, the moving direction is reversed in step S131 and then the process proceeds to step S133.

  The inversion timing comes every time the vertical synchronization signal Vsync is generated twice. If the current moving direction is the closest direction, the infinite direction is set as the next moving direction, and if the current moving direction is the infinite direction, the close direction is set as the next moving direction. Therefore, the focus lens 14 is displaced in the manner shown in FIG. 10 between the three points of the close side position, the center position, and the infinite side position.

  In step S133, the current focus evaluation value AF_H is set in any one of the near side register R1, the central register R2, and the infinite side register R3. The current focus evaluation value AF_H is set in the near side register R1 when the current position of the focus lens 14 is the near side position, is set in the center register R2 when the current position of the focus lens 14 is the center position, and the focus lens When the current position of 14 is the infinite side position, it is set in the infinite side register R3. When the process of step S133 is completed, the process returns to the upper layer routine.

  The search process in step S89 shown in FIG. 17 is executed according to a subroutine shown in FIG. First, in step S140, the lens movement amount is set to “W_L” which is larger than the above-mentioned “W_S”. In step S141, it is determined whether or not the current focus evaluation value AF_H exceeds the set value of the maximum value register R4. If the determination result is YES, the current focus evaluation value AF_H is set in the maximum value register R4 in step S143, and the down counter C4 is set to “0” in step S145. On the other hand, if the determination result is NO, the down counter C4 is incremented in a step S147. When the process of step S145 or S147 is completed, it is determined in step S149 whether or not the count value of the down counter exceeds the threshold value C.

  If the determination result is NO, it is assumed that the focus lens 14 has not yet exceeded the in-focus point, and the process directly returns to the upper hierarchy routine. If the determination result is YES, the focus lens 14 is regarded as having exceeded the in-focus point, and the moving direction of the focus lens 14 is reversed in step S151. In step S153, the distance corresponding to the threshold C is regarded as the distance to the focal point, and this distance is set as the lens movement amount. In the subsequent step S155, the operation mode is set to the monitoring mode, and the monitoring counter C5 is set to “0”. When the process of step S155 is completed, the process returns to the upper layer routine.

  The monitoring process in step S89 shown in FIG. 17 is executed according to a subroutine shown in FIG. In step S161, it is determined with reference to the relative ratio RT or the focus evaluation value AF_H whether or not a motion has occurred in the object scene. If the determination result is YES, the monitoring counter C5 is incremented in step S163, while if the determination result is NO, the monitoring counter C5 is set to “0” in step S165.

  In step S167, it is determined whether or not the count value of the monitoring counter C5 exceeds the monitoring time SVT. If the determination result is NO, the process returns to the upper hierarchy routine. If the determination result is YES, an initialization process similar to the above-described step S71 is executed in step S169, and a standby process corresponding to the standby time WT is executed in step S171. When the standby time WT elapses, the routine returns to the upper-level routine.

  As can be seen from the above description, the image sensor 16 has an imaging surface that captures the scene through the focus lens 14 and generates a scene image. The I / F 38 records the object scene image generated by the image sensor 16 on the recording medium 40 for each specified period. The CPU 26 adjusts the distance from the focus lens 14 to the imaging surface every time a motion occurs in the object scene (S85, S87).

  The distance adjustment process is started when the duration of the movement of the object scene reaches the monitoring time SVT and the waiting time WT has elapsed. Further, the distance from the focus lens 14 to the imaging surface is adjusted with reference to the high frequency component of the object scene image belonging to the AF area. Accordingly, the response characteristic of the distance adjustment process changes by increasing or decreasing the AF area, the monitoring time SVT, or the standby time WT.

  The CPU 26 increases the size of the AF area, the monitoring time SVT and the standby time WT as the length of the designated period increases (S41, S47, S51). As a result, the response characteristic of the distance adjustment process is reduced as the designated period is extended.

  By reducing the response characteristic of the distance adjustment process as the length of the designated period increases, the amount of change in the distance from the focus lens 14 to the imaging surface due to the movement of the object field becomes smaller as the recording period becomes longer. . That is, when a slight motion or a temporary motion occurs in the object scene, the distance variation when the recording cycle is long is smaller than the distance variation when the recording cycle is short. As a result, it is possible to suppress deterioration in image quality when a plurality of recorded scene images are reproduced with a cycle shorter than the recording cycle.

  In this embodiment, the focus lens 14 is moved in the optical axis direction for focus adjustment, but the image sensor 16 is moved in the optical axis direction instead of the focus lens 14 or together with the focus lens 14. Also good.

  In this embodiment, the AF area is fixed to the area AF_L in the interval mode. However, the area AF_L is divided into areas AF_L1, AFL_2, AF_L3,... Having different sizes and the AF area is changed between the areas AF_L1, AFL_2, AF_L3,... According to the length of the recording cycle in the interval mode. It may be.

  Further, in this embodiment, the values of all parameters of the AF area, the monitoring time SVT and the standby time WT are increased in response to the recording start operation under the interval mode. However, the number of parameters to be increased may be changed according to the length of the recording cycle in the interval mode. That is, if the recording cycle in the interval mode is short, only a part of the AF area, the monitoring time SVT and the standby time WT is increased. If the recording cycle in the interval mode is long, all of the AF area, the monitoring time SVT and the standby time WT are increased. You may make it increase.

  In this embodiment, the lens movement amount set in step S153 of FIG. 22 is continuously enabled even in the monitoring mode, and the focus lens 14 slightly vibrates even in the monitoring mode. However, in the monitoring mode, the amount of minute vibration may be suppressed or the minute vibration may be stopped.

  In this embodiment, the focus lens 14 is moved in the direction shown in FIG. 10 in the direction determination mode. Instead, the focus lens 14 may be moved in the manner shown in FIG. .

DESCRIPTION OF SYMBOLS 10 ... Video camera 12 ... Zoom lens 14 ... Focus lens 16 ... Image sensor 22 ... AE evaluation circuit 24 ... AF evaluation circuit 26 ... CPU
28 ... Key input device

Claims (7)

An imaging means having an imaging surface for capturing an object scene through a focus lens and generating an object scene image;
Recording means for recording the object scene image generated by the imaging means for each specified period;
An adjustment unit that adjusts the distance from the focus lens to the imaging surface every time movement occurs in the object field, and a response characteristic of the adjustment unit that decreases as the length of the specified period increases. A video camera comprising control means. A cutting-out unit that cuts out the object scene image belonging to the specified area among the object scene images generated by the imaging unit;
The adjustment means executes an adjustment process based on the object scene image cut out by the cut-out means,
The video camera according to claim 1, wherein the parameter defining the response characteristic of the adjusting unit includes a size of the designated area. The adjusting means determines whether or not the duration of the motion that has occurred in the object scene has reached a threshold, and the determination result of the determining means is updated from a negative result to a positive result. Including starting means for starting the distance adjustment operation when
The video camera according to claim 1, wherein a parameter that defines a response characteristic of the adjusting unit includes a magnitude of the threshold value. The adjusting means includes a detecting means for detecting a high frequency component of the object scene image generated by the imaging means for a distance adjusting operation,
4. The video camera according to claim 1, wherein the parameter defining the response characteristic of the adjusting unit includes a waiting time until the detecting unit is activated.   Setting means is further provided for setting the designated period to the first period corresponding to the first recording mode, and setting the designated period to a second period longer than the first period corresponding to the second recording mode. The video camera according to claim 1. A processor of a video camera having an imaging surface for capturing an object scene through a focus lens and having an imaging means for generating an object scene image,
A recording step of recording the object scene image generated by the imaging means for each specified period;
An adjustment step for adjusting the distance from the focus lens to the imaging surface every time movement occurs in the object field, and a response characteristic of the adjustment step so as to decrease as the length of the specified period increases. An imaging control program for executing a control step. An imaging control method executed by a video camera having an imaging surface for capturing an object scene through a focus lens and having an imaging means for generating an object scene image,
A recording step of recording the object scene image generated by the imaging means for each specified period;
An adjustment step for adjusting the distance from the focus lens to the imaging surface every time movement occurs in the object field, and a response characteristic of the adjustment step so as to decrease as the length of the specified period increases. An imaging control method comprising a control step.

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