JP2009053462A - Video camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a video camera having improved discrimination accuracy of focusing characteristics, then, having stabilized focusing operation. <P>SOLUTION: An image sensor 16 includes an imaging surface 16f on which an optical field image through a focusing lens 14 is irradiated, and repeatedly forms the field images. The position of the focusing lens 14 is repeatedly changed by a driver 18b between three points in parallel with the field image forming processing by the image sensor 16. The high-frequency AF evaluation values of the field image generated by the image sensor 16 are repeatedly detected by a high-frequency AF evaluation circuit 26a and a CPU 28 in parallel with the processing of changing the position of the focusing lens 14. Referring to the detected high-frequency AF evaluation values, the CPU 28 discriminates the focusing characteristics, and adjusts the focusing lens 14 at the focal point based on the discrimination result. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a video camera that adjusts the distance from an optical lens to an imaging surface by so-called continuous AF processing.

An example of this type of video camera is disclosed in Patent Document 1. According to this background art, whether the focus lens is in focus or not is determined by taking in an AF evaluation value while wobbling the focus lens. If it is determined that the focus lens is in focus, wobbling of the focus lens is stopped and a restart monitoring process routine is executed. When it is determined that the focus lens is out of focus, a mountain climbing operation in the direction determined based on the wobbling operation is performed.
JP-A-9-284632 [H04N 5/232, G02B 7/28, G03B 13/36]

  However, since two AF evaluation values are detected along with the wobbling operation, it is difficult to determine the focusing characteristic of the focus lens. As a result, the restart monitoring routine and the hill climbing operation are erroneously executed, and the focus adjustment operation may become unstable.

  Therefore, a main object of the present invention is to provide a video camera capable of stabilizing the focus adjustment operation.

  The video camera according to the invention of claim 1 (10: reference numeral corresponding to the embodiment; the same applies hereinafter) has an imaging surface (16f) on which an optical image of the object scene through the optical lens (14) is irradiated, The image pickup means (16) for repeatedly generating the object scene image, and the distance from the optical lens to the image pickup surface is N (N: an integer of 3 or more) in parallel with the object image generation process by the image pickup means. Change means (S31, S59 to S65) for repeatedly changing between, detection means (S25) for detecting the predetermined frequency component of the object scene image generated by the imaging means repeatedly in parallel with the change process of the change means, detection means The discriminating means (S91 to S95) for discriminating the focusing characteristic with reference to the predetermined frequency component detected by, and the distance from the optical lens to the imaging surface based on the discrimination result of the discriminating means to the distance corresponding to the focal point Adjustment means (S39) for adjustment is provided.

  The imaging means has an imaging surface on which an optical image of the scene that has passed through the optical lens is irradiated, and repeatedly generates the scene image. The distance from the optical lens to the imaging surface is repeatedly changed between N values (N: an integer of 3 or more) by the changing means in parallel with the generation process of the object scene image by the imaging means. The predetermined frequency component of the object scene image generated by the imaging unit is repeatedly detected by the detecting unit in parallel with the changing process of the changing unit. The discriminating unit discriminates the focusing characteristic with reference to the predetermined frequency component detected by the detecting unit. The adjusting unit adjusts the distance from the optical lens to the imaging surface based on the determination result of the determining unit to a distance corresponding to the focal point.

  By repeatedly changing the distance from the optical lens to the imaging surface between N values (N: an integer of 3 or more), N predetermined frequency components respectively corresponding to the N values are detected. Thereby, the accuracy of determining the focusing characteristic is improved, and the focus adjustment operation is stabilized.

  The video camera according to the invention of claim 2 is dependent on claim 1, and the changing means switches switching means (S59) that switches the distance changing direction alternately between the reduction direction and the enlargement direction, and the distance change amount is a period. Correction means (S61 to S65) for correcting automatically. Thereby, the distance from the optical lens to the imaging surface can be changed between three or more values.

  The video camera according to the invention of claim 3 is dependent on claim 1 or 2, and the discriminating means corresponds to the value of the predetermined frequency component detected corresponding to the value close to the median corresponding to the value close to the maximum value. First component amount discriminating means (S91) for discriminating whether or not the amount of the detected default frequency component is exceeded, and a value of the default frequency component detected corresponding to the value close to the median value being close to the minimum value The second component amount discriminating means (S93, S95) for discriminating whether or not it exceeds the amount of the predetermined frequency component detected corresponding to. As a result, the magnitude relationship between the amounts of the predetermined frequency components can be accurately determined.

  A video camera according to a fourth aspect of the invention is dependent on the third aspect, and measures the number of times that both the determination result of the first component amount determination means and the determination result of the second component amount determination means show a negative result. First measuring means (S99) and determining means (S127, S133, S) for determining the distance adjustment direction with reference to a specific luminance parameter when the number parameter based on the measurement result of the first measuring means satisfies the first predetermined condition. S135), and the adjustment means changes the distance from the optical lens to the imaging surface in the distance adjustment direction determined by the determination means.

  If the amount of the frequency component closer to the median is smaller than each of the amount of frequency component closer to the maximum value and the amount of frequency component closer to the minimum value, the distance from the optical lens to the imaging surface is reduced and from the optical lens The focal point exists in both directions in which the distance to the imaging surface is enlarged. The focal point to be searched is determined with reference to a specific luminance parameter.

  The video camera according to the invention of claim 5 is dependent on claim 4, and the number of pixels detecting means (S9, S11) for detecting the number of pixels having luminance corresponding to the light source from the object scene image generated by the imaging means. The specific luminance parameter corresponds to the number of pixels detected by the pixel number detection means.

  The video camera according to claim 6 is dependent on claim 4 or 5, wherein the determining means determines whether or not the number of pixels detected by the pixel number detecting means has reached a threshold value (S127), First direction determining means (S133) for determining the direction in which the distance from the optical lens to the imaging surface is reduced as the distance adjustment direction when the determination result of the pixel number determining means is affirmative, and the determination result of the pixel number determining means Includes a second direction determining means (S135) for determining, as a distance adjustment direction, a direction in which the distance from the optical lens to the imaging surface is enlarged when is negative.

  Therefore, when the object scene includes a light source, a focal point existing in the enlargement direction is searched. The focus is on a subject farther than the light source. On the other hand, when the object scene does not include a light source, a focal point existing in the reduction direction is searched. The focus is adjusted to a subject closer to the imaging surface.

  The video camera according to a seventh aspect of the invention is dependent on any one of the third to sixth aspects, wherein both the determination result of the first component amount determination unit and the determination result of the second component amount determination unit are positive. And a stop means (S121) for stopping the changing means and the adjusting means when the frequency parameter based on the measurement result of the second measuring means satisfies the second predetermined condition.

  If the amount of frequency components near the median is greater than each of the amount of frequency components near the maximum value and the amount of frequency components near the minimum value, the distance from the optical lens to the imaging surface is close to the distance corresponding to the focal point. . At this time, the changing means and the adjusting means are stopped.

  The video camera according to the invention of claim 8 is dependent on claim 7, and is a change that repeatedly determines whether or not the amount of change of the predetermined frequency component detected by the detection means exceeds a threshold value in relation to the stop process of the stop means. It further includes an amount determining means (S191, S197) and a restarting means (S199) for restarting the changing process of the changing means when the determination result of the change amount determining means is updated from a negative result to a positive result.

  A video camera according to the invention of claim 9 is dependent on any one of claims 1 to 8, and holding means (S77, S81,...) Holds predetermined frequency components detected by the detecting means for each value designated by the changing means. S85), and a exclusion means (S73) for excluding the predetermined frequency component detected by the detection means from the target of the holding means when the imaging surface is in a camera shake state, and the determination means is a predetermined value held by the holding means. The discrimination process is executed with reference to the frequency component.

  By excluding the frequency component detected when the imaging surface is in a camera shake state from the holding target of the holding unit, the focus adjustment is accurately performed based on the predetermined frequency component held by the holding unit.

  The imaging control program according to the invention of claim 10 has an imaging surface (16f) on which an optical image of the object scene that has passed through the optical lens (14) is irradiated, and an imaging means (16) that repeatedly generates the object scene image. The processor (28) of the video camera (10) equipped with the distance from the optical lens to the imaging surface is set to N (N: an integer of 3 or more) in parallel with the object field image generation processing by the imaging means. Change steps (S31, S59 to S65) that change repeatedly between

  A detection step (S25) for repeatedly detecting the predetermined frequency component of the object scene image generated by the imaging means in parallel with the changing process of the changing step, and by referring to the predetermined frequency component detected by the detecting step, the focusing characteristic is determined. Imaging control for executing the determining step (S91 to S95) for determining, and the adjusting step (S39) for adjusting the distance from the optical lens to the imaging surface to the distance corresponding to the focal point based on the determination result of the determining step It is a program.

  As in the first aspect of the invention, the focus adjustment operation can be stabilized.

  The image pickup control method according to the invention of claim 11 has an image pickup surface (16f) on which an optical image of the object scene passed through the optical lens (14) is irradiated, and an image pickup means (16) for repeatedly generating the object scene image. An imaging control method for a video camera (10) comprising: a distance N from an optical lens to an imaging surface in parallel with an object scene image generation process by an imaging means (N: an integer of 3 or more) Change step (S31, S59 to S65) for repeatedly changing between, detection step (S25) for repeatedly detecting the predetermined frequency component of the object scene image generated by the imaging means in parallel with the change process of the change step, detection A discrimination step (S91 to S95) for discriminating the focusing characteristic with reference to the predetermined frequency component detected in the step, and a distance corresponding to the focal point from the optical lens to the imaging surface based on the discrimination result of the discrimination step An adjustment step (S39) for adjusting to is provided.

  As in the first aspect of the invention, the focus adjustment operation can be stabilized.

  According to the present invention, by repeatedly changing the distance from the optical lens to the imaging surface between N (N: an integer of 3 or more) values, N predetermined frequencies respectively corresponding to the N values. Components are detected. Thereby, the accuracy of determining the focusing characteristic is improved, and the focus adjustment operation is stabilized.

  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.

  With reference to FIG. 1, the video camera 10 of this embodiment includes a zoom lens 12 and a focus lens 14. The optical image of the object scene is irradiated on the imaging surface 16f of the image sensor 16 through the zoom lens 12 and the focus lens 14, and subjected to photoelectric conversion. As a result, a charge representing the object scene image, that is, a raw image signal is generated.

  When the power is turned on, the moving image shooting process is started. At this time, the CPU 28 instructs the driver 18c to repeat exposure and charge reading. The driver 18c gives a plurality of timing signals to the image sensor 16 in order to perform the exposure operation of the imaging surface 16f and the read operation of the electric charge obtained thereby. The raw image signal generated on the imaging surface 16f is read in the order according to the raster scanning in response to the vertical synchronization signal Vsync generated once every 1/60 seconds. The raw image signal is output from the image sensor 16 at a frame rate of 60 fps.

  The raw image signal output from the image sensor 16 is subjected to a series of processes of correlated double sampling, automatic gain adjustment, and A / D conversion by the CDS / AGC / AD circuit 20. The signal processing circuit 22 performs processing such as white balance adjustment, color separation, and YUV conversion on the raw image data output from the CDS / AGC / AD circuit 20 and writes the YUV format image data to the SDRAM 36 through the memory control circuit 34. .

  The motion detection circuit 30 captures the raw image data output from the CDS / AGC / AD circuit 20 every 1/60 seconds, and detects a motion vector indicating camera shake of the imaging surface 16f based on the captured raw image data. . The detected motion vector is given to the CPU. The CPU 28 moves the extraction area EX assigned to the SDRAM 36 in the manner shown in FIG. 2 in the direction in which the motion vector is canceled (compensated).

  The LCD driver 38 reads partial image data belonging to the extraction area EX through the memory control circuit 34 every 1/60 seconds, and drives the LCD monitor 40 based on the read partial image data. As a result, a real-time moving image (through image) of the object scene is displayed on the monitor screen.

  The luminance evaluation circuit 24 evaluates the brightness (luminance) of the object scene every 1/60 seconds based on the Y data generated by the signal processing circuit 22. The CPU 28 adjusts the exposure amount of the image sensor 16 based on the luminance evaluation value obtained by the luminance evaluation circuit 24. As a result, the brightness of the through image displayed on the LCD monitor 40 is appropriately adjusted.

  The high frequency AF evaluation circuit 26a takes in the Y data belonging to the focus area FA shown in FIG. 2 or FIG. 3 among the Y data generated by the signal processing circuit 22, and converts the high frequency component of the fetched Y data to 1 / Integrate every 60 seconds. Similarly, the mid-range AF evaluation circuit 26b captures Y data belonging to the above-mentioned focus area FA among the Y data generated by the signal processing circuit 22, and converts the mid-frequency component of the captured Y data to 1/60 seconds. Integrate every time. As a result, the high frequency AF evaluation value is given from the high frequency AF evaluation circuit 26a to the CPU 28 every 1/60 seconds, and the middle frequency AF evaluation value is given from the middle frequency AF evaluation circuit 26b to the CPU 28 every 1/60 seconds. . The CPU 28 is also directly supplied with Y data generated by the signal processing circuit 22.

  The CPU 28 executes a continuous AF task based on the high frequency AF evaluation value and the mid frequency AF evaluation value given from the high frequency AF evaluation circuit 26a and the mid frequency AF evaluation circuit 26b. The position of the focus lens 14 in the optical axis direction is continuously changed by the driver 18 b under the control of the CPU 28. The CPU 28 also executes a light source determination task with reference to the Y data given from the signal processing circuit 22. Thus, it is determined, for example, every frame (= 1/60 second) whether or not a light source exists in the object scene. The determination result is reflected in the processing of the continuous AF task.

  When the zoom operation is executed by the key input device 32, the CPU 28 controls the driver 18a to move the zoom lens 12 in the optical axis direction. As a result, the magnification of the through image displayed on the LCD monitor 40 changes.

  When a recording start operation is performed by the key input device 32, the CPU 28 instructs the I / F 42 to perform a recording process. The I / F 42 reads partial image data belonging to the extraction area EX from the SDRAM 36 every 1/60 seconds through the memory control circuit 34, and creates a moving image file including the read partial image data on the recording medium 44. Such a recording process is ended in response to a recording end operation by the key input device 32.

  In the light source discrimination task, pixels in which Y data is saturated are detected from the pixels belonging to the focus area FA. The number of such saturated pixels is counted by the high luminance counter C0. If the count value of the high luminance counter C0 is less than the threshold value TH, the light source flag FLG is set to “0”, assuming that no light source exists in the object scene. On the other hand, if the count value of the high-intensity counter C0 is equal to or greater than the threshold value TH, the light source flag FLG is set to “1” because the light source exists in the object scene.

  The continuous AF task is roughly composed of a direction determination process, a hill climbing process, and a monitoring process. The direction determination process is a process for specifying the direction in which the focal point exists, that is, the in-focus direction. The hill-climbing 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 the focal point has changed due to the movement of the subject itself belonging to the focus area FA or the pan / tilt of the video camera 10.

The high-frequency AF evaluation value and the mid-frequency AF evaluation value are acquired from the high-frequency AF evaluation circuit 26a and the mid-range AF evaluation circuit 26b each time the vertical synchronization signal Vsync is generated, independently of these processes. A relative ratio is calculated. The high-frequency AF evaluation value, the mid-range AF evaluation value, and the relative ratio are referred to as necessary in each of the direction determination process, the hill climbing process, and the monitoring process.
[Equation 1]

  Relative ratio = high range AF evaluation value / mid range AF evaluation value

  In the direction determination process, every time the vertical synchronization signal Vsync is generated, the focus lens 14 is alternately displaced toward the close side and the infinite side. However, after the displacement amount is initially set to “L / 2”, every time the vertical synchronization signal Vsync is generated, “L” → “L / 2” → “L / 2” → “L” → “L / 2 ”→“ L / 2 ”→... That is, the amount of displacement is changed from “L / 2” to “L” at a rate of once every three frames, and the focus lens 14 is moved to the nearest position, the center position, and the infinite position in the manner shown in FIG. Displace between.

  The high-frequency AF evaluation value of the object scene image captured when the focus lens 14 is disposed at the close side position is set in the close side register R3, and is captured when the focus lens 14 is disposed at the center position. The high-frequency AF evaluation value of the object scene image is set in the central register R4, and the high-frequency AF evaluation value of the object scene image captured when the focus lens 14 is disposed at the infinite side position is the infinite side register R5. Set to

  Therefore, if the high-frequency AF evaluation value of the object scene image captured at time t * (*: 1, 2, 3,...) Is defined as “AFt *”, the focus lens 14 is displaced as shown in FIG. In this case, the high-frequency AF evaluation value AFt * is set in the closest register R3, the central register R4, and the infinite register R5 in the manner shown in FIG.

  However, when the motion vector output from the motion detection circuit 30 indicates camera shake of the imaging surface 16f, the above-described register setting process is prohibited. When camera shake occurs at times t5 to t6, the setting process of the high-frequency AF evaluation value AFt5 to the closest register R3 and the setting process of the high-frequency AF evaluation value AFt6 to the central register R4 are prohibited.

  The magnitude relationship between the high-frequency AF evaluation values set in the close side register R3, the central register R4, and the infinite side register R5 is determined every time the focus lens 14 is displaced in the designated direction, and the count of the vertex counter C6 is determined according to the determination result. The value is updated.

  When the high frequency AF evaluation value set in the central register R4 exceeds the high frequency AF evaluation value set in the closest register R3 and the high frequency AF evaluation value set in the infinite side register R5, the vertex counter C6 Incremented. The vertex counter C6 is also configured such that the high frequency AF evaluation value set in the central register R4 is equal to or less than the high frequency AF evaluation value set in the closest register R3 and the high frequency AF evaluation value set in the infinite side register R5. When decremented. Further, the vertex counter C6 is set to “0” when none of the above-mentioned cases are satisfied, that is, when the high-frequency AF evaluation value shows an increasing tendency or decreasing tendency from the closest side toward the infinity side.

  For example, as shown in FIG. 6, the high-frequency AF evaluation value and the mid-range AF evaluation value change like a mountain. 7A to 7C show a part of the characteristic curve of the high-frequency AF evaluation value shown in FIG. The vertex counter C6 is set to “0” when the focus lens 14 is displaced between the positions A1 to A3 shown in FIG. 7A, and the focus lens 14 is set between the positions B1 to B3 shown in FIG. 7B. Is incremented when the lens is displaced, and decremented when the focus lens 14 is displaced between the positions C1 to C3 shown in FIG.

  When the count value of the vertex counter C6 exceeds the threshold value B, the focus lens 14 is considered to be in focus, and the direction determination process is terminated and the monitoring process is started. When the count value of the vertex counter C6 falls below the threshold “−B”, a different direction is determined as the in-focus direction according to the determination result of the light source determination task. That is, if the light source flag FLG indicates “0”, the closest direction is determined as the focusing direction, and if the light source flag FLG indicates “1”, the infinite direction is determined as the focusing direction. The mountain climbing process is started after the in-focus direction is thus determined.

  Therefore, when shooting an object scene that does not include a light source as shown in FIG. 2, the focus is adjusted to the person H1 who is the subject closer to the imaging surface 16f. On the other hand, when shooting the object scene including the light source L as shown in FIG. 3, the focus is adjusted to the person H2 as a subject far from the imaging surface 16f.

  Note that the direction in which the distance from the focus lens 14 to the imaging surface 16f increases is the closest direction, and the direction in which the distance from the focus lens 14 to the imaging surface 16f decreases is the infinite direction.

  In the direction determination process, in parallel with the register setting process and the update process of the vertex counter C6, the high frequency AF evaluation value acquired in the previous frame (the previous high frequency AF evaluation value) and the high frequency acquired in the current frame. The magnitude relationship with the AF evaluation value (current high frequency AF evaluation value) 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 C1 is incremented. If the numerical value tends to increase toward the closest direction, the direction counter C1 is decremented. The infinite direction is assumed to be the in-focus direction by incrementing the direction counter C1, and the closest direction is assumed to be the in-focus direction by decrementing the direction counter C1.

  The direction counter C1 updated in this way is noted when the vertex counter C6 is greater than or equal to the threshold “−B” and less than or equal to the threshold B. When the count value of the direction counter C1 exceeds the threshold A, the infinite direction is determined as the in-focus direction. On the other hand, when the count value of the direction counter C1 falls below the threshold “−A”, the closest direction is determined as the in-focus direction.

  The execution number counter C2 is incremented every time the focus lens 14 is displaced in the direction determination process. If the count value of the execution counter C2 exceeds the threshold value M or N before the count value of the vertex counter C6 or the count value of the direction counter C1 matches the above-described condition, the in-focus direction is determined by the direction prediction process. In the direction prediction process, the closest direction is determined as the in-focus direction when the current position of the focus lens 14 is close to the infinite end, and the infinite direction is determined as the in-focus direction when the current position of the focus lens 14 is close to the close-up end. Is done.

  A relationship of N> M is established between the above threshold values M and N. When hand shake occurs, the threshold value M is compared with the count value of the execution number counter C2, and when hand shake does not occur, the threshold value N is compared with the count value of the execution number counter C2. The high frequency AF evaluation value at the time of occurrence of camera shake becomes lower than the high frequency AF evaluation value at the time of no camera shake due to deterioration of the high frequency component of the object scene image. For this reason, the relative ratio required when camera shake occurs is lower than the relative ratio required when camera shake does not occur. Therefore, specifically, the threshold value N is noted when the relative ratio exceeds the threshold value α, and the threshold value M is noted when the relative ratio is equal to or less than the threshold value α.

  In the hill-climbing process, the focus lens 14 is moved in the determined focusing direction, and the maximum high-frequency AF evaluation value among the high-frequency AF evaluation values detected by the high-frequency AF evaluation circuit 26a is stored in the maximum value register R1. Is set. When the set value of the maximum value register R1 exceeds the threshold value X and the subsequently detected high-frequency AF evaluation value falls below the set value of the maximum value register R1 three times in succession, the focus lens 14 exceeds the in-focus point. It is considered. The moving direction of the focus lens 14 is reversed, and the focus lens 14 is disposed at the focal point.

  When the set value of the maximum value register R1 is equal to or less than the threshold value X, the high-frequency AF evaluation value is continuously lower than the set value of the maximum value register R1 three times and the relative ratio exceeds the threshold value β, the in-focus direction Is considered to be opposite to the current direction of travel. The mountain climbing process is temporarily stopped and resumed after the moving direction is reversed.

  When the setting value of the maximum value register R1 is equal to or less than the threshold value X, the high-frequency AF evaluation value is continuously lower than the setting value of the maximum value register R1 three times and the relative ratio is equal to or less than the threshold value β. Is unknown, the direction determination process is restarted.

  In the monitoring process, it is determined whether or not the amount of change in the current high-frequency AF evaluation value from the set value of the maximum value register R1 exceeds K%. If the determination result is positive over a plurality of frames, it is considered that the in-focus FP has changed due to the movement of the subject itself belonging to the focus area FA or the pan / tilt of the video camera 10, and the direction determination process is restarted. .

  The CPU 28 executes a plurality of tasks including a light source determination task shown in FIG. 8 and a continuous AF processing task shown in FIGS. 9 to 18 in parallel. Note that control programs corresponding to these tasks are stored in the flash memory 46.

  Referring to FIG. 8, in step S1, the light source flag FLG is set to “0”, and in step S3, the high luminance counter C0 is set to “0”. In step S5, it is determined whether or not the vertical synchronization signal Vsync has been generated (whether 1V has elapsed since the processing in the previous step S3), and in step S7, whether or not the current pixel is the start pixel of the focus area FA. Is determined. If both steps S5 and S7 are YES, it is determined whether or not the Y data value of the current pixel is equal to the saturation value. If “NO” here, the process proceeds to a step S13 as it is. On the other hand, if YES, it is considered that the current pixel has a luminance corresponding to the light source, and the high luminance counter C0 is incremented in step S11, and then the process proceeds to step S13.

  In step S13, it is determined whether or not the current pixel is an end pixel of the focus area FA. If NO, the process returns to step S9. If YES, the process proceeds to step S15. In step S15, it is determined whether or not the count value of the high luminance counter C0 has reached the threshold value TH. If “YES” here, the scene is considered to include a light source, and the light source flag FLG is set to “1” in a step S17. On the other hand, if NO, the scene is regarded as not including a light source, and the light source flag FLG is set to “0” in step S19. When the process of step S17 or S19 is completed, the process returns to step S3.

  Referring to FIG. 9, in step S21, an initialization process is executed. Specifically, the number of movement steps is set to “0”, the operation mode is set to the direction determination mode, and the direction counter C1, the execution count counter C2, the closest counter C3, the central counter C4, the infinite counter C5, and Each count value of the vertex counter C6 is set to “0”. The number of movement steps indicates the number of steps that a stepping motor (not shown) provided in the driver 18b should be rotated in one lens movement process.

  When the vertical synchronization signal Vsync is generated, YES is determined in step S23, and the high-frequency AF evaluation value is acquired from the high-frequency AF evaluation circuit 26a in step S25, and the mid-range AF evaluation value is acquired in step S27. Get from. In step S29, the relative ratio is calculated according to the above-described equation 1. In step S31, the focus lens 14 is moved in the setting direction by the set number of movement steps. At the time when the first process is executed, the number of movement steps is “0”, and the movement direction is undetermined. As a result, the focus lens 14 continues to stop at the current position.

  In step S33, it is determined whether or not the current operation mode is the direction determination mode. In step S35, it is determined whether or not the operation mode is the hill-climbing mode. If YES in step S33, direction determination processing is executed in step S37. If YES in step S35, mountain climbing processing is executed in step S39. If NO in step S35, monitoring processing is executed in step S41. . When the process of step S37, S39 or S41 is completed, the process returns to step S23.

  The direction determination process in step S37 shown in FIG. 9 is executed according to the subroutine shown in FIGS. First, in step S51, it is determined whether or not the execution number counter C2 is “0”. If “YES” here, the moving direction of the focus lens 14 is set to the closest direction in a step S53. In step S55, the current high frequency AF evaluation value is held as the previous high frequency AF evaluation value. In the subsequent step S57, the setting of the moving direction of the focus lens 14 is reversed. That is, if the current moving direction is the close direction, the infinite direction is set as the moving direction, and if the current moving direction is the infinite direction, the close direction is set as the moving direction.

  In step S61, it is determined whether or not the current timing is a timing for reducing the lens movement amount. If YES, the movement step number is set to a step number corresponding to “L / 2” in step S63, while NO. If there is, the number of movement steps is set to the number of steps corresponding to “L” in step S65. The amount of movement of the focus lens 14 is initially set to “L / 2” and then “L” → “L / 2” → “L / 2” → “L” → every time the vertical synchronization signal Vsync is generated. It is updated in the manner of “L / 2” → “L / 2” →. The amount of movement is changed from “L / 2” to “L” at a rate of once every three frames, and the focus lens 14 moves between three points of the closest position, the center position, and the infinite position in the manner shown in FIG. Displace.

  When the process of step S63 or S65 is completed, the near side counter C3, the central counter C4 or the infinite side counter C5 is incremented in step S67. If the lens position after displacement is the near side position, the near side counter C3 is incremented, if the lens position after displacement is the center position, the center counter C4 is incremented, and the lens position after displacement is the infinite side position. For example, the infinite counter C5 is incremented.

  In step S69, it is determined whether or not the count value of the closest counter C3, the central counter C4, or the infinite counter C5 exceeds the threshold value γ. In step S73, it is determined based on the motion vector output from the motion detection circuit 30 whether or not the imaging surface 16f is in a shake state when the object scene image from which the current high-frequency AF evaluation value is detected is captured. .

  The process of step S69 is a process of determining whether or not the set value of the near side register R3, the central register R4 or the infinite side register R5 lacks reliability. If YES is determined here, the error process of step S71 is performed. After that, return to the upper level routine. If YES is determined in the step S73, it is assumed that the current high frequency AF evaluation value cannot be used as a reference for direction determination, and the process directly returns to the upper hierarchy routine. If NO is determined in step S69 and NO is determined in step S73, the position of the focus lens 14 when the scene image from which the current high-frequency AF evaluation value is detected is captured is determined in step S75.

  If the discrimination result indicates the near side position, the current high frequency AF evaluation value is set in the near side register R3 in step S77, and the near side counter C3 is set to "0" in step S79. If the discrimination result indicates the closest position, the current high frequency AF evaluation value is set in the central register R4 in step S81, and the central counter C4 is set to "0" in step S83. If the discrimination result indicates the closest position, the current high frequency AF evaluation value is set in the infinite register R5 in step S85, and the infinite counter C5 is set to "0" in step S87. When the process of step S79, S83 or S87 is completed, the process returns to the upper hierarchy routine.

  If NO is determined in step S51 shown in FIG. 10, it is determined in step S89 whether or not the count value of the execution number counter C2 is “3” or more. If “NO” here, the process proceeds to a step S103 as it is, whereas if “YES”, the process proceeds to a step S103 through steps S91 to S101.

  In step S91, it is determined whether or not the set value of the central register R4 exceeds the set value of the infinite register R5. In each of steps S93 and S95, whether or not the set value of the central register R4 exceeds the set value of the nearest register R3. Determine whether or not. If YES is determined in each of steps S91 and S93, the high frequency AF evaluation value is considered to change in the manner shown in FIG. 7B, and the vertex counter C6 is incremented in step S101. If NO is determined in each of steps S91 and S95, the high frequency AF evaluation value is considered to change in the manner shown in FIG. 7C, and the vertex counter C6 is decremented in step S99.

  If NO is determined in step S91 and YES is determined in step S95, the high frequency AF evaluation value is considered to change in the manner shown in FIG. 7A, and the vertex counter C6 is set to “0” in step S101. . If YES is determined in step S91 and NO is determined in step S93, the high frequency AF evaluation value is considered to change in a manner opposite to that shown in FIG. 7A, and the vertex counter C6 is set to “0” in step S101. Set.

  In step S103, it is determined whether or not the current moving direction is an infinite direction. If NO, the process proceeds to step S105, and if YES, the process proceeds to step S107. In both steps S105 and S107, it is determined whether or not the current high frequency AF evaluation value exceeds the previous high frequency AF evaluation value. However, regarding step S105, when the determination result is YES, the process proceeds to step S109, and when the determination result is NO, the process proceeds to step S111. On the other hand, for step S107, when the determination result is YES, the process proceeds to step S111, and when the determination result is NO, the process proceeds to step S109.

  In step S109, the direction counter C1 is decremented, and in step S111, the direction counter C1 is incremented. When the process of step S109 or S111 is completed, it is determined in step S113 whether or not the relative ratio calculated in step S29 exceeds the threshold value α. If “YES” here, the imaging surface 16f is determined not to be in a camera shake state, and the process proceeds to a step S115. If NO, the imaging surface 16f is assumed to be in the hand shake state, and the process proceeds to step S113.

  In step S115, it is determined whether or not the count value of the execution number counter C2 exceeds a threshold value N (N: for example, 20). In step S117, whether the count value of the execution number counter C2 exceeds a threshold value M (M: for example, 10). Determine whether or not. If YES in step S115 or S117, the process proceeds to step S139 through the direction prediction process in step S119. In step S139, the operation mode is set to the hill-climbing mode, the down counter C7 is set to “0”, and the maximum value register R1 is cleared. When the process of step S139 is completed, the routine returns to the upper hierarchy routine.

  On the other hand, if NO in step S115 or S117, it is determined in step S121 whether or not the count value of the vertex counter C6 exceeds the threshold value B, and whether or not the count value of the vertex counter C6 is less than the threshold value “−B”. Is determined in step S125. Further, it is determined in step S129 whether or not the count value of the direction counter C1 exceeds the threshold value A, and whether or not the count value of the direction counter C1 is less than the threshold value “−A” is determined in step S131. The numerical value B is “3”, for example, and the numerical value A is “5”, for example.

  If “YES” is determined in the step S121, the operation mode is set to the monitoring mode in a step S123, and then the process returns to the upper layer routine. If YES is determined in the step S125, it is determined whether or not the light source flag FLG is “1” in a step S127. If “YES” here, the infinite direction is regarded as the in-focus direction, and the moving direction is set to the infinite direction in step S133. On the other hand, if NO, the close direction is regarded as the in-focus direction, and the moving direction is set to the close direction in step S135. If YES in step S129, the process proceeds to step S133, and if YES in step S131, the process proceeds to step S135. If both steps S129 and S131 are NO, the process returns to step S55. When the process of step S133 or S135 is completed, the number of movement steps is set to a value of “1” or more in step S137, and then the process proceeds to step S139.

  The direction prediction process in step S119 shown in FIG. 13 is executed according to a subroutine shown in FIG. First, in step S141, it is determined whether or not the current position of the focus lens 14 is closer to the infinity side than the center of the movement range. If “YES” here, the close direction is regarded as the in-focus direction, and the moving direction is set to the close direction in step S143. On the other hand, if NO, the infinite direction is regarded as the in-focus direction, and the moving direction is set to the infinite direction in step S145. In step S147, the number of movement steps is set to a value of “1” or more, and then the process returns to the upper hierarchy routine.

  The mountain climbing process in step S39 shown in FIG. 9 is executed according to the subroutine shown in FIGS. In step S151, it is determined whether or not the current high frequency AF evaluation value exceeds the set value of the maximum value register R1. If YES here, the current high-frequency AF evaluation value is set in the maximum value register R1 in a step S153, and the down counter C7 is set to “0” in a step S155. If NO, the down counter C7 is incremented in step S157. When the process of step S155 or S157 is completed, it is determined in step S159 whether or not the count value of the down counter C7 is “2”.

  If “NO” here, the process proceeds to a step S163 as it is, whereas if “YES”, the current position of the focus lens 14 is registered in the lens position register R2 in a step S161, and then, the process proceeds to a step S163. In step S163, it is determined whether or not the count value of the down counter C7 exceeds “3”. If NO, the process returns to the upper layer routine. If YES, the set value of the maximum value register R1 exceeds the threshold value X. It is determined whether or not in step S165.

  If “YES” in the step S165, the focus lens 14 is regarded as having exceeded the focal point, and the moving direction is reversed in a step S167. In step S169, the focal point FP is specified based on the lens position registered in the lens position register R2, and the number of movement steps to the specified focal point FP is set. In step S171, the operation mode is set to the monitoring mode, and the count values of the down counter C7 and the monitoring counter C8 are set to “0”. When the process of step S171 is completed, the process returns to the upper-level routine.

  If NO is determined in step S165, the process proceeds to step S173 to stop the mountain climbing process. In step S173, it is determined whether or not the relative ratio calculated in step S29 exceeds a threshold value β. If YES is determined here, the moving direction of the focus lens 14 is considered to be opposite to the direction toward the in-focus point, the moving direction is reversed in step S175, and the number of moving steps is set to “1” or more in step S177. Set to the value of. In step S179, the down counter C7 is set to “0” and the maximum value register R1 is cleared. When the process of step S179 is completed, the process returns to the upper layer routine. As a result, the mountain climbing process is restarted.

  If NO is determined in both step S165 and step S173, the process proceeds to step S181, where the operation mode is set to the direction determination mode, and each of the direction counter C1 and the execution number counter C2 is set to “0”. When the process of step S181 is completed, the process returns to the upper layer routine. As a result, the direction determination process is restarted.

  The monitoring process in step S41 shown in FIG. 9 is executed according to a subroutine shown in FIG. First, in step S191, it is determined whether or not the amount of change in the current high frequency AF evaluation value from the set value of the maximum value register R1 exceeds K%. If “NO” here, the monitoring counter C8 is set to “0” in a step S193, while if “YES”, the monitoring counter C8 is incremented in a step S195. When the process of step S193 or S195 is completed, it is determined in step S197 whether or not the count value of the monitoring counter C8 exceeds the threshold value D. If “NO” here, the process returns to the upper hierarchy routine. If YES, the operation mode is set to the direction determination mode in step S199, each of the direction counter C1 and the execution number counter C2 is set to “0”, and then the process returns to the upper-level routine.

  As can be seen from the above description, the image sensor 16 has the imaging surface 16f on which the optical image of the object scene that has passed through the focus lens 14 is irradiated, and repeatedly generates the object scene image. The position of the focus lens 14 is repeatedly changed between three points by the driver 18b in parallel with the generation process of the object scene image by the image sensor 16 (S31, S59 to S65). The high-frequency AF evaluation value of the object scene image generated by the image sensor 16 is repeatedly detected by the high-frequency AF evaluation circuit 26a and the CPU 28 in parallel with the process of changing the position of the focus lens 14 (S25).

  The CPU 28 holds the detected high frequency AF evaluation value for each setting position of the focus lens 14 ((S77, S81, S85), and determines the focusing characteristic by referring to the held high frequency AF evaluation value ( S91 to S95), and the focus lens 14 is adjusted to the in-focus position based on the discrimination result (S39), however, the high-frequency AF evaluation value detected corresponding to the camera shake of the imaging surface 16f is determined from the holding target. Eliminated (S73).

  By repeatedly changing the position of the focus lens 14 between three points, three high-frequency AF evaluation values respectively corresponding to the three points are detected. This improves the accuracy of determining the focusing characteristic. Further, the high-frequency AF evaluation value detected corresponding to the camera shake of the imaging surface 16f is excluded from the holding target. The focus adjustment is accurately executed regardless of the camera shake of the imaging surface 16f. As a result, the focus adjustment operation is stabilized.

  Further, when the in-focus point exists in both the closest direction and the infinite direction, the moving direction of the focus lens 14 is determined by the presence or absence of the light source. That is, when the object scene includes a light source, a focal point existing in an infinite direction is searched. The focus is on a subject farther than the light source. On the other hand, when the object scene does not include a light source, a focal point existing in the closest direction is searched. The focus is adjusted to a subject closer to the imaging surface. As described above, the direction in which the distance from the focus lens 14 to the imaging surface 16f increases is the closest direction, and the direction in which the distance from the focus lens 14 to the imaging surface 16f decreases is the infinite direction. Thereby, good focus control is realized.

  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 focus lens 14 is displaced between three positions in the direction determination process, but the focus lens 14 may be displaced between four or more positions. Further, in this embodiment, 1/60 seconds is assumed as the generation cycle of the vertical synchronization signal Vsync, but the generation cycle is not limited to 1/60 seconds.

It is a block diagram which shows the structure of one Example of this invention. It is an illustration figure which shows an example of the to-be-photographed field caught by the imaging surface. It is an illustration figure which shows another example of the to-be-photographed field caught by the imaging surface. It is an illustration figure which shows an example of operation | movement of the focus lens at the time of direction determination. It is an illustration figure which shows an example of a register setting process. It is a graph which shows the relationship between a lens position and each of a high region AF evaluation value and a middle region AF evaluation value. (A) is an illustrative view showing a part of the characteristics of the high-frequency AF evaluation value, (B) is an illustrative view showing another part of the characteristics of the high-frequency AF evaluation value, and (C) is a high-frequency figure. It is an illustration figure which shows the other part of the characteristic of AF evaluation value. It is a flowchart which shows a part of operation | movement of CPU. It is a flowchart which shows another part of operation | movement of CPU. It is a flowchart which shows a part of other operation | movement of CPU. It is a flowchart which shows a part of others of operation | movement of CPU. It is a flowchart which shows another part of operation | movement of CPU. It is a flowchart which shows a part of other operation | movement of CPU. It is a flowchart which shows a part of others of operation | movement of CPU. It is a flowchart which shows another part of operation | movement of CPU. It is a flowchart which shows a part of other operation | movement of CPU. It is a flowchart which shows a part of others of operation | movement of CPU. It is a flowchart which shows another part of operation | movement of CPU.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Video camera 12 ... Zoom lens 14 ... Focus lens 16 ... Image sensor 26a ... High frequency AF evaluation circuit 26b ... Middle frequency AF evaluation circuit 28 ... CPU
30 ... Motion detection circuit

Claims (11)

An imaging means having an imaging surface on which an optical image of the scene through the optical lens is irradiated, and repeatedly generating the scene image;
Changing means for repeatedly changing the distance from the optical lens to the imaging surface between N values (N: an integer of 3 or more) in parallel with the generation process of the object scene image by the imaging means;
Detecting means for repeatedly detecting a predetermined frequency component of the object scene image generated by the imaging means in parallel with the changing process of the changing means;
A discriminating unit that discriminates a focusing characteristic with reference to a predetermined frequency component detected by the detecting unit; and a distance corresponding to a focal point that is a distance from the optical lens to the imaging surface based on a discrimination result of the discriminating unit. A video camera comprising adjusting means for adjusting to   The video camera according to claim 1, wherein the changing unit includes a switching unit that alternately switches a change direction of the distance between a reduction direction and an enlargement direction, and a correction unit that periodically corrects the change amount of the distance.   The determination means determines whether or not the amount of the predetermined frequency component detected corresponding to the value close to the median value exceeds the amount of the predetermined frequency component detected corresponding to the value close to the maximum value. Component amount determining means, and determining whether or not the amount of the predetermined frequency component detected corresponding to the value close to the median value exceeds the amount of the predetermined frequency component detected corresponding to the value close to the minimum value The video camera according to claim 1, further comprising a second component amount determination unit. First measurement means for measuring the number of times that both the determination result of the first component amount determination means and the determination result of the second component amount determination means show a negative result, and the measurement result of the first measurement means Determining means for determining a distance adjustment direction with reference to a specific luminance parameter when the number-of-times parameter based satisfies a first predetermined condition;
The video camera according to claim 3, wherein the adjustment unit changes a distance from the optical lens to the imaging surface in a distance adjustment direction determined by the determination unit. A pixel number detecting means for detecting the number of pixels having luminance corresponding to a light source from the object scene image generated by the imaging means;
The video camera according to claim 4, wherein the specific luminance parameter corresponds to the number of pixels detected by the pixel number detection unit.   The determining means determines whether or not the number of pixels detected by the number-of-pixels detecting means has reached a threshold value, and when the determination result of the number-of-pixels determining means is affirmative, from the optical lens A first direction determining unit that determines a direction in which a distance to the imaging surface is reduced as the distance adjustment direction; and a distance from the optical lens to the imaging surface when a determination result of the pixel number determining unit is negative The video camera according to claim 4, further comprising a second direction determining unit that determines a direction in which an image is enlarged as the distance adjustment direction. A second measuring unit that measures the number of times that both the discrimination result of the first component amount discriminating unit and the discrimination result of the second component amount discriminating unit are positive; and the number of times based on the measurement result of the second measuring unit The video camera according to claim 3, further comprising a stopping unit that stops the changing unit and the adjusting unit when a parameter satisfies a second predetermined condition. Change amount determination means for repeatedly determining whether or not the change amount of the predetermined frequency component detected by the detection means exceeds a threshold value in relation to the stop process of the stop means, and the determination result of the change amount determination means is negative The video camera according to claim 7, further comprising a restarting unit that restarts the changing process of the changing unit when an actual result is updated to a positive result. Holding means for holding the predetermined frequency component detected by the detecting means for each value designated by the changing means; and holding the predetermined frequency component detected by the detecting means when the imaging surface is in a camera shake state. It further includes an exclusion means for excluding from the attention target of the means,
9. The video camera according to claim 1, wherein the determination unit performs a determination process with reference to a predetermined frequency component held by the holding unit. In a processor of a video camera having an imaging surface on which an optical image of a scene that has passed through an optical lens is irradiated and having an imaging means that repeatedly generates a scene image,
A change step of repeatedly changing the distance from the optical lens to the imaging surface between N values (N: an integer of 3 or more) in parallel with the generation process of the object scene image by the imaging means;
A detection step of repeatedly detecting a predetermined frequency component of the object scene image generated by the imaging means in parallel with the changing process of the changing step;
A determination step of determining a focusing characteristic with reference to the predetermined frequency component detected in the detection step; and a distance corresponding to a focal point from the optical lens to the imaging surface based on the determination result of the determination step An imaging control program for executing an adjustment step for adjusting the image. An imaging control method for a video camera having an imaging surface on which an optical image of an object scene that has passed through an optical lens is irradiated and having an imaging means that repeatedly generates an object scene image,
A change step of repeatedly changing the distance from the optical lens to the imaging surface between N values (N: an integer of 3 or more) in parallel with the generation process of the object scene image by the imaging means;
A detection step of repeatedly detecting a predetermined frequency component of the object scene image generated by the imaging means in parallel with the changing process of the changing step;
A determination step of determining a focusing characteristic with reference to the predetermined frequency component detected in the detection step; and a distance corresponding to a focal point from the optical lens to the imaging surface based on the determination result of the determination step An imaging control method, comprising an adjustment step for adjusting to an image.

Images