JP2004117492A - Autofocus system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an autofocus system realizing the reduction of the scale of a circuit and power consumption by performing all or a part of autofocus processing using a plurality of imaging devices arranged at positions set at different optical path length by a single processing part in a time-division manner. <P>SOLUTION: The autofocus system is provided with three imaging devices A, B and C having different optical path length for the autofocus control of a television camera or the like. Required processing is performed to video signals outputted from the respective imaging devices in the time-division manner by an A/D converter 100, an HPF 52, a gate circuit 54 and an adder 56 so as to obtain a focus evaluated value showing the contrast of an image. A CPU 82 performs focusing by controlling a focus based on the focus evaluated value. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an autofocus system, and more particularly, to an autofocus system that performs autofocus by a contrast method using a plurality of image sensors having imaging surfaces arranged at positions having different optical path lengths.
[0002]
[Prior art]
Conventionally, there has been proposed a method of detecting a focus state (front focus, rear focus, focus) of a photographing lens by using a plurality of image pickup devices having image pickup surfaces at positions having different optical path lengths (for example, Patent Document 1, See Patent Documents 2, 3, and 4). For example, an optical path length of two focus state detection imaging elements that capture images in the same shooting range with respect to an imaging element that captures a video image (video imaging element) is longer than that of the video imaging element. Place it in a position that is shorter than the position. Then, high-frequency components are extracted from the images (video signals) captured by the focus state detection imaging devices, and based on the extracted high frequency components, the degree of focusing (image quality) on each imaging surface of the focus state detection imaging devices is determined. Are determined and compared. As a result, information on the focus state (focus information) on the imaging surface of the video imaging element, that is, which of the front focus, the rear focus, and the focus state is detected from the magnitude relationship of the focus evaluation values. By applying such a focus state detection method, it is possible to perform focus detection for autofocus, and it is possible to determine whether the subject is in focus or not, and to determine whether the subject is in focus before or after focus. There is an advantage that the reaction speed to the burning is fast.
[0003]
[Patent Document 1]
Japanese Patent Application No. 2001-168246
[0004]
[Patent Document 2]
Japanese Patent Application No. 2001-168247
[0005]
[Patent Document 3]
Japanese Patent Application 2001-168248
[0006]
[Patent Document 4]
Japanese Patent Application 2001-168249
[0007]
[Problems to be solved by the invention]
By the way, the focus evaluation value is obtained by performing the same processing on video signals from a plurality of focus state detecting image sensors. However, if the processing is performed in parallel by a processing circuit provided corresponding to each video signal, an image at the same time is obtained from each image sensor, and there is a case where there is flicker such as a fluorescent lamp, or the image moves on the screen. Although focus information from a subject can be processed with high accuracy, there is a disadvantage in that the circuit size and power consumption increase.
[0008]
The present invention has been made in view of such circumstances, and in an autofocus system that performs autofocusing of a contrast method using a plurality of imaging devices having imaging surfaces at positions having different optical path lengths, a video signal of each imaging device is provided. It is an object of the present invention to provide an auto-focus system for reducing the size and power consumption of a processing unit for obtaining focus information from the camera and reducing the cost.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, an image obtained by capturing a subject light incident on a photographing lens by a plurality of image sensors arranged at positions having different optical path lengths and obtaining the images by the respective image sensors. In an auto-focus system including a focus control unit that controls focus of the photographing lens based on a signal and automatically performs focusing, all of the same processing performed on each video signal from each of the imaging elements is performed. Alternatively, a single processing unit for processing a part of each video signal in a time-division manner is provided.
[0010]
Further, according to a second aspect of the present invention, in the first aspect of the present invention, the processing unit includes a frame for specifying a range to be focused within an angle of view of the photographing lens as an AF frame. A video signal to be processed is switched to a video signal from another image sensor every time processing of at least a video signal in the AF frame among video signals from one image sensor is completed.
[0011]
Further, according to a third aspect of the present invention, in the first aspect of the present invention, the frame that specifies a range to be focused within the angle of view of the photographing lens is set as an AF frame, and the processing unit includes one frame. Each time the processing of some of the video signals in the AF frame from one image sensor is completed, the video signal to be processed is switched to a video signal from another image sensor.
[0012]
According to a fourth aspect of the present invention, in the second or third aspect of the present invention, the image processing apparatus further includes a storage unit configured to store a video signal from each of the imaging elements, and the processing unit performs the same processing on each of the imaging elements. The video signal output at the time is read out from the storage means and processed.
[0013]
According to a fifth aspect of the present invention, in the third aspect of the invention, the switching of the video signal to be processed is performed based on a horizontal synchronization signal.
[0014]
According to a sixth aspect of the present invention, in the fifth aspect of the invention, the vertical synchronizing signal of the video signal from each of the image sensors is shifted by a predetermined time.
[0015]
According to the present invention, all or part of autofocus processing using a plurality of image sensors arranged at positions having different optical path lengths is performed by a single processing unit in a time-division manner, so that the circuit scale is reduced. And power consumption can be reduced.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of an autofocus system according to the present invention will be described in detail with reference to the accompanying drawings.
[0017]
FIG. 1 is a configuration diagram showing a configuration of a television camera system to which the present invention is applied. The television camera system shown in FIG. 1 includes a camera body 10, an interchangeable photographing lens 12, and the like. The camera body 10 captures a video for recording and reproduction, and outputs a video signal of a predetermined format to a recording medium. An image sensor (image sensor for video) for recording, a required circuit, and the like are built in. On the other hand, the taking lens 12 is detachably mounted on the front side of the camera body 10, and as shown in the figure, the optical system of the taking lens 12 has a fixed focus lens from the front end side as generally known. F ', a movable focus lens F, a zoom lens Z including a variable power system and a correction system, an iris I, and a relay lens (relay optical system) including a front relay lens R1 and a rear relay lens R2 are arranged. You. Note that the configuration of each lens in the drawing is simplified, and a lens group including a plurality of lenses may be represented by one lens.
[0018]
Also, as shown in the figure, on the optical path of the subject light between the front relay lens R1 and the rear relay lens R2 of the relay optical system, the inclination is substantially 45 degrees with respect to the optical axis O of the photographing lens 12, A half mirror 24 is provided to split the subject light for focus state detection from the subject light for video.
[0019]
Of the subject light incident from the front end side of the photographing lens 12, other than the light beam branched by the half mirror 24, that is, the subject light for video transmitted through the half mirror 24 is emitted from the rear end side of the photographing lens 12, The light enters the imaging unit 20 of the main body 10. Although the configuration of the imaging unit 20 is omitted, the subject light incident on the imaging unit 20 is separated into three colors of red light, green light, and blue light by, for example, a color separation optical system. Incident on the imaging surface of the imaging device for imaging). As a result, a color image for broadcast is captured. The focus plane 22 in the figure shows a position optically equivalent to the imaging plane of each imaging element on the optical axis O of the photographing lens 12.
[0020]
On the other hand, the subject light reflected by the half mirror 24 is guided to the focus state detecting imaging unit 26 along the optical axis O ′ substantially perpendicular to the optical axis O as the focus state detecting subject light. Here, the subject light is in a substantially parallel state between the front relay lens R1 and the rear relay lens R2, and the subject light reflected by the half mirror 24 is condensed having the same properties as the rear relay lens R2. Through the relay lens R3 for the focus state and enters the imaging unit 26 for focus state detection.
[0021]
FIG. 2 is a configuration diagram illustrating a configuration of the imaging unit 26 for detecting a focus state. As shown in the figure, the imaging unit 26 includes three prisms P1, P2, and P3 that constitute a light splitting optical system, and three imaging elements (two-dimensional CCDs) A, B, and C for detecting a focus state. . When the imaging devices A, B, and C are particularly distinguished from the video imaging device mounted on the camera body 10, they are referred to as focus state detection imaging devices A, B, and C.
[0022]
The subject light reflected by the half mirror 24 and traveling along the optical axis O 'as described above first enters the first prism P1 and is reflected and transmitted by the half mirror surface 40 of the first prism P1. Divided. The reflected light is incident on the imaging surface of the imaging device C. On the other hand, the transmitted light enters the second prism P2, and is further divided into reflected light and transmitted light by the half mirror surface 42 of the second prism P2. The reflected light is incident on the image sensor B. On the other hand, the transmitted light passes through the third prism P3 and enters the image sensor A. The subject light is split by the half mirror surface 40 of the first prism P1 and the half mirror surface 42 of the second prism P2 such that the amounts of the subject light incident on the image pickup devices A, B, and C are equal. Further, these imaging devices A, B, and C need not be those that capture color images, and are assumed to be CCDs that capture monochrome images in the present embodiment.
[0023]
When the optical axis of the subject light incident on each of the image sensors A, B, and C (the optical axis of each image sensor) is shown on the same straight line, the light enters each of the image sensors A, B, and C as shown in FIG. The optical path length of the image sensor B is the shortest, the optical path length of the image sensor C is the longest, and the optical path length of the image sensor A is intermediate between the optical path lengths of the image sensors B and C. Length. That is, the image pickup surfaces of the image pickup device B and the image pickup device C are arranged in parallel at the same distance before and after the image pickup surface of the image pickup device A. The imaging surface of the imaging device A has a conjugate relationship with the focus surface 22 (see FIG. 1) of the camera body 10, and the optical path length for the subject light incident on the imaging lens 12 is different from that of the video imaging device of the camera body 10. It matches the imaging plane. Note that the image sensor A is arranged so that the object surface of the image sensor of the image pickup device whose image plane is the image forming surface coincides with the object surface of the image sensor A of the image sensor that forms the image surface. The present invention is not limited to the case where the imaging surface of the imaging element for use and the optical path length match. Further, the light splitting optical system that splits the subject light into the image pickup devices A, B, and C is not limited to the configuration using the prisms P1 to P3 as described above.
[0024]
With the optical system configured as described above, the subject light split by the half mirror 24 out of the subject light incident on the photographing lens 12 is transmitted along the optical path arranged near a position conjugate with the focus plane 22 of the camera body 10. Images are picked up by three image sensors A, B and C having different lengths.
[0025]
Next, an outline of the control of the autofocus based on the focus state detection will be described. As illustrated in FIG. 1, images (video signals) captured by the focus state detection imaging elements A, B, and C are captured by the signal processing unit 28. The signal processing unit 28 focuses the focusing state of the photographing lens 12 on the focusing surface 22 of the camera body 10 based on the high-frequency components of the video signals acquired from the image sensors A, B, and C, as described later. The position (focus position) of the focus lens F is obtained. Then, a control signal for instructing movement of the focus lens F to the focus position is output to the focus motor drive circuit 30. The focus motor drive circuit 30 drives a focus motor (not shown), moves the focus lens F via a power transmission mechanism 32 including gears and the like, and sets the focus lens F to a focus position specified by the signal processing unit 28. . Autofocus control is performed by performing such processing continuously.
[0026]
Subsequently, a configuration of the signal processing unit 28 and a process of detecting a focus state will be described. FIG. 4 is a block diagram showing a configuration of the signal processing unit 28. The configuration of the signal processing unit 28 shown in FIG. 4 shows a basic configuration for explaining the processing content of the signal processing unit 28. For convenience, the configuration of FIG. The configuration according to will be described later. As shown in the figure, the image of the subject imaged by the focus state detection imaging devices A, B, and C is output as a video signal of a predetermined format, and is individually arranged for each of the imaging devices A, B, and C. A / D converters 50, 60, 70, high-pass filters (HPF) 52, 62, 72, gate circuits 54, 64, 74, and adders 56, 66, 76 for image sharpness (image contrast) And is input to the CPU 82.
[0027]
The processing up to obtaining the focus evaluation value will be described using a circuit arranged for the image sensor A. The video signal output from the image sensor A is, for example, approximately 1 / 15.75 kHz provided from the synchronization signal generation circuit 80. Is a luminance signal indicating the luminance of each pixel to which the horizontal synchronizing signal and the vertical synchronizing signal of about 1/60 Hz are added. The video signal is converted into a digital signal by the A / D converter 50, and then converted to a high-pass filter. (HPF) 52, and a high frequency component of the video signal is extracted. The signal of the high-frequency component extracted by the HPF 52 is next input to the gate circuit 54, and the video signal of one screen (one field) is within a predetermined AF frame to be subjected to autofocus (for example, a screen). Only the signal corresponding to the pixel in the (center portion) is extracted by the gate circuit 54. The AF frame is set at the center of the screen (angle of view of the photographing lens 12), for example, as shown in FIG. Then, the value of the signal in the AF frame for one screen extracted by the gate circuit 54 is added by the adder 56.
[0028]
As a result, the sum of the values of the high frequency components of the video signal in the AF frame is obtained, and the value obtained by the adder 56 is used as a focus evaluation value indicating the degree of sharpness of the image in the AF frame by the CPU 82. Read by.
[0029]
It should be noted that various synchronization signals are given from the synchronization signal generation circuit 80 shown in FIG. 9 to the respective circuits such as the imaging devices A, B, C, and the CPU 82, so that the processing of each circuit is synchronized. In the following description, the focus evaluation values obtained from the imaging devices A, B, and C are referred to as the focus evaluation values of the channels (ch) A, B, and C, respectively. In the signal processing unit 28, an EEPROM 84 and the like from which data can be read / written by the CPU 82 are arranged.
[0030]
Upon reading the focus evaluation values of chA, B, and C as described above, the CPU 82 detects the current focus state of the photographing lens 12 with respect to the focus surface 22 of the camera body 10 based on the focus evaluation values. FIG. 6 is a diagram showing the state of the focus evaluation value with respect to the focus position when a certain subject is photographed, with the horizontal axis representing the focus position of the photographing lens 12 and the vertical axis representing the focus evaluation value. A curve a shown by a solid line in the figure shows a focus evaluation value of chA obtained from the focus state detecting imaging element A at a position conjugate with the focus surface 22 of the camera body 10 with respect to the focus position. Curves b and c shown by the middle dotted lines show the focus evaluation values of chB and chC obtained from the focus state detection imaging elements B and C, respectively, with respect to the focus position.
[0031]
In the figure, the focus position F3 at which the focus evaluation value of chA indicated by the curve a is maximum (maximum) is the focus position, but the focus position of the photographing lens 12 is now set to the position of F1 in the figure. And In this case, the respective focus evaluation values of chA, chB, and chC are values corresponding to the focus position F1 by the curves a, b, and c. At this time, since at least the focus evaluation value of chB is larger than the focus evaluation value of chC, the focus position is set closer to the focus position F3 that is the focus position, that is, in the state of the front focus. You can see that there is.
[0032]
On the other hand, assuming that the focus position of the photographing lens 12 is set to the position of F2 in the figure, the focus evaluation values of chA, chB, and chC are values corresponding to the focus position F2 by curves a, b, and c. is there. In this case, since at least the focus evaluation value of chC is larger than the focus evaluation value of chB, the state where the focus position is set to the infinity side from the focus position F3 which is the focus position, that is, the state of the back focus It turns out that it is.
[0033]
Assuming that the focus position of the taking lens 12 is set to the focus position of F3 in the figure, the focus evaluation values of chA, chB, and chC are values corresponding to the focus position F3 by curves a, b, and c. is there. At this time, since the focus evaluation value of chB and the focus evaluation value of chC are equal, it is understood that the focus position is set to the focus position F3, that is, the focus state.
[0034]
As described above, based on the focus evaluation values of chA, chB, and chC obtained from each of the imaging devices A, B, and C, the focus state of the imaging lens 12 at the current focus position is set to the front focus, the rear focus, and the focus position. Any of the impatience can be detected. Then, in the present embodiment, the focus position at which focusing is performed is detected as follows based on the focal point values of chA, chB, and chC obtained from the three imaging elements A, B, and C.
[0035]
In FIG. 6, the curves a, b, and c indicating the distributions of the focus evaluation values of chA, chB, and chC have substantially the same shape. The focus evaluation value of chA at the focus position displaced by a predetermined shift amount from the position is shown. For example, in the curve a of the focus evaluation value of chA shown in FIG. 7, it is assumed that the focus position is set to F4 in the figure. At this time, the focus evaluation value of chA is the point P on the curve a. _A Shows the value of On the other hand, the focus evaluation value of chB is the point P on the curve a at the focus position F5 displaced by a predetermined shift amount toward infinity from the focus position F4. _B The focus evaluation value of chC is the point P on the curve a at the focus position F6 displaced by the predetermined shift amount to the close side from the focus position F4. _C Shows the value of Note that the difference between the focus position F4 and the focus position F5, that is, the shift amount for the focus evaluation value of chB is, for example, the focus position of the maximum point of the curve b and the focus position of the curve a and the maximum position of the curve a in FIG. The difference between the focus position F4 and the focus position F6, that is, the shift amount for the focus evaluation value of chC is equal to the difference between the focus position of the maximum point of the curve c and the focus position of the curve a and the maximum point of the curve a in FIG. Equal to position difference.
[0036]
On the other hand, the curve a can be approximated by a predetermined function (for example, a quadratic curve). Therefore, three points P of each chA, chB, chC _A , P _B , P _C , The curve a can be specifically specified from the focus evaluation value, and the in-focus position F3 at which the focus evaluation value becomes maximum in the curve a can be obtained.
[0037]
When the CPU 82 of FIG. 4 obtains the focus position at which focusing is performed based on the focus evaluation values of chA, B, and C as described above, it transmits a control signal to the focus motor drive circuit 30 so that the focus position is obtained. Then, the focus lens F is moved.
[0038]
Next, the configuration of the signal processing unit 28 in which the present invention is applied to the conventional configuration of the signal processing unit 28 shown in FIG. 4 will be described. FIG. 8 is a configuration diagram showing a first embodiment of the configuration of the signal processing unit 28 to which the present invention is applied. In FIG. 8, blocks denoted by the same reference numerals as those in the conventional configuration in FIG. 4 are blocks that perform the same or similar processing as in FIG. The first embodiment of FIG. 8 will be described in comparison with the conventional configuration of FIG. 4. In the conventional configuration, the video signals from the focus state detection imaging elements A, B, and C (hereinafter, video signals of chA, chB, and chC). Are processed in parallel by individual circuits to calculate the focus evaluation values of chA, chB, and chC. However, in the first embodiment of FIG. 8, the common processing units (circuits) are chA, chB, and chC. Are processed in a time-division manner.
[0039]
That is, the video signals of chA, chB, and chC are input to the A / D converter 100 having three channels. The A / D converter 100 performs A / D conversion processing on the chA, chB, and chC video signals by switching the channel for each field according to the vertical synchronization signal, and converts the chA, chB, and chC video signals into digital signals. Are sequentially output to the HPF 52 one field at a time. In this embodiment, it is assumed that the timings of the vertical synchronizing signals in the video signals of chA, chB, and chC match.
[0040]
For example, the A / D converter 100 converts the chA video signal from an analog signal to a digital signal in a period from a certain vertical synchronization signal (first vertical synchronization signal) to the next vertical synchronization signal (second vertical synchronization signal). And outputs it to the HPF 52, and then converts the chB video signal from an analog signal to a digital signal in the period from the second vertical synchronization signal to the next vertical synchronization signal (third vertical synchronization signal). Output to the HPF 52. Subsequently, during the period from the third vertical synchronizing signal to the next vertical synchronizing signal (fourth vertical synchronizing signal), the video signal of chC is converted from an analog signal to a digital signal and output to the HPF 52. By repeating the switching of the channels from the first vertical synchronization signal to the fourth vertical synchronization signal in this manner, the chA, chB, and chC video signals converted into digital signals are output to the HPF 52 one field at a time. Is done. In the A / D converter 100, the vertical synchronizing signal may be obtained directly from the synchronizing signal generation circuit 80, or may be obtained from video signals input from the respective image sensors A, B, and C.
[0041]
The high frequency components of the chA, chB, and chC video signals output from the A / D converter 100 to the HPF 52 are extracted by the HPF 52 in the same manner as described in the conventional configuration of FIG. As a result, only signals within the AF frame (see FIG. 5) are extracted and output. Then, the signal for one field output from the gate circuit 54 is added by the adder 56. As a result, the CPU 82 is given the focus evaluation values of chA, chB, and chC by switching the channels processed by the A / D converter 100 on a field-by-field basis.
[0042]
As described above, by processing the video signal of each channel in a time-division manner by the common processing unit, the circuit scale and power consumption of the signal processing unit 28 can be reduced. Particularly, the effect of sharing the large-scale HPF 52 for the processing of each channel is great.
[0043]
FIG. 9 is a configuration diagram showing a second form of the configuration of the signal processing unit 28 to which the present invention is applied. Note that blocks denoted by the same reference numerals as those in the conventional configuration in FIG. 4 and the first embodiment in FIG. 8 are blocks that perform the same or similar processing as in FIGS. 4 and 8. In the second embodiment of FIG. 9, the processing after the HPF 52 is the same as the processing after the HPF 52 in the first embodiment of FIG. On the other hand, in the second embodiment of FIG. 9, the video signals of chA, chB, and chC output from the respective image pickup devices A, B, and C are individually provided A / D signals similarly to the conventional configuration of FIG. The digital signals are converted by the converters 50, 60, 70. Thereafter, for example, video signals for one field output from the imaging devices A, B, and C at the same time are stored in SRAMs (Static Random Access Memory) 102, 104, and 106, respectively. The video signal for one field stored in each of the SRAMs 102, 104, and 106 is output to the HPF 52 in a predetermined order.
[0044]
For example, first, the video signal for one field of chA stored in the SRAM 102 is output to the HPF 52, and then the video signal for one field of chB stored in the SRAM 104 is output to the HPF 52. Next, the video signal for one field of chC stored in the SRAM 106 is output to the HPF 52. By storing the video signals output from the respective imaging devices A, B, and C at the same time in the memory in this manner, the video signals obtained by the imaging devices A, B, and C being captured at the same time are obtained. , The focus evaluation values of chA, chB, and chC can be obtained. That is, in the first embodiment of FIG. 8, since the real-time video signals output from the image sensors A, B, and C are processed in a time-division manner, images are captured by the image sensors A, B, and C at the same time. Although a focus evaluation value for an image cannot be obtained, a focus evaluation value for an image captured at the same time by each of the imaging elements A, B, and C can be obtained in the second embodiment of FIG.
[0045]
In the first embodiment of FIG. 8 and the second embodiment of FIG. 9, the channel is switched for each field and the video signal is processed by one processing unit. The channel may be switched each time the processing for the video signal in the necessary range, that is, the video signal in the AF frame (see FIG. 5) is completed. Further, the content of the time-division processing performed by one processing unit may be different from that of the first and second embodiments, and all or a part of the processing performed on the video signal is performed by the one processing unit. The present invention can be applied to the case of processing. In particular, there is an effect that only the processing of the HPF 52 is time-divisionally processed by one processing unit, and the other processing is performed by the individual processing unit for each channel.
[0046]
FIG. 10 is a configuration diagram showing a third mode of the configuration of the signal processing unit 28 to which the present invention is applied. Note that blocks denoted by the same reference numerals as those in the conventional configuration in FIG. 4 and the first embodiment in FIG. 8 are blocks that perform the same or similar processing as in FIGS. 4 and 8. The A / D converter 100 according to the first embodiment of FIG. 8 performs the A / D conversion process by switching the video signals of chA, chB, and chC for each field, but the A / D converter 100 according to the third embodiment of FIG. The / D converter 100 performs A / D conversion processing by switching the video signals of chA, chB, and chC every one horizontal scanning period. For example, when a video signal of chA is converted from an analog signal to a digital signal and output to the HPF 52 during a period from a certain horizontal synchronization signal (first horizontal synchronization signal) to the next horizontal synchronization signal (second horizontal synchronization signal). Next, during a period from the second horizontal synchronizing signal to the next horizontal synchronizing signal (third horizontal synchronizing signal), the chB video signal is converted from an analog signal to a digital signal and output to the HPF 52. Subsequently, during a period from the third horizontal synchronizing signal to the next horizontal synchronizing signal (fourth horizontal synchronizing signal), the video signal of chC is converted from an analog signal to a digital signal and output to the HPF 52. By repeating the switching of the channels from the first horizontal synchronization signal to the fourth horizontal synchronization signal in this manner, the video signals of chA, chB, and chC converted into the digital signals are supplied to the HPF 52 by one horizontal scanning period. Is output to
[0047]
As for the chA, chB, and chC video signals output from the A / D converter 100 for each horizontal scanning period, high-frequency components are extracted by the HPF 52 in the same manner as described in the conventional configuration of FIG. 54 extracts and outputs only signals within the AF frame (see FIG. 5). Then, the signal output from the gate circuit 54 after processing the video signal of chA is input to the adder 56, and the signal output from the gate circuit 54 after processing the video signal of chB and output Is input to the adder 66. The signal output from the gate circuit 54 after processing the video signal of chC is input to the adder 76. As a result, the signals for one field output from the gate circuit 54 are added by the adders 56, 66, and 76 respectively. The adder 56 adds the focus evaluation value of chA, and the adder 66 adds the focus evaluation value of chB. In the device 76, the focus evaluation value of chC is obtained. The focus evaluation values of chA, chB, and chC obtained by the adders 56, 66, and 76 are provided to the CPU 82 for each field.
[0048]
As described above, the video signal of each channel can be processed in a time-division manner for each horizontal scanning period by the common processing unit, and the circuit scale of the signal processing unit 28 can be reduced as in the first embodiment. .
[0049]
When the video signals of the respective channels are processed in a time-division manner for each horizontal scanning period as in the third embodiment, the positions of the horizontal scanning lines actually processed for the video signals of chA, chB, and chC are determined. different. Therefore, in order to prevent this, the time of the vertical synchronizing signal of each of the imaging devices A, B, and C is shifted by one horizontal scanning period in accordance with the order of channels processed by the A / D converter 100. The processing may be performed on the same horizontal scanning line position for the video signal of any channel. In other words, for the time-division processing, the timing of the vertical synchronization signal of the video signal is delayed by the time corresponding to the delay of the processing of the video signal of another channel with respect to the video signal of a certain channel. The scanning line positions that are not processed and the scanning line positions that are not processed may not be different for each channel.
[0050]
FIG. 11 is a configuration diagram showing a fourth mode of the configuration of the signal processing unit 28 to which the present invention is applied. Note that blocks denoted by the same reference numerals as those in the second embodiment in FIG. 9 and the third embodiment in FIG. 10 are blocks that perform the same or similar processing as in FIGS. 9 and 10. In the fourth embodiment of FIG. 11, the processing subsequent to the HPF 52 is the same as the processing subsequent to the HPF 52 in the third embodiment of FIG. On the other hand, in the fourth embodiment of FIG. 11, the video signals of chA, chB, and chC output from the image sensors A, B, and C are similar to those of the second embodiment of FIG. 9 (similar to the conventional configuration of FIG. 4). ) Are converted into digital signals by A / D converters 50, 60, and 70 provided individually. Thereafter, the video signals for one horizontal scanning period output from the imaging devices A, B, and C at the same time are stored in the SRAMs 102, 104, and 106, respectively. The video signals for one horizontal scanning period stored in each of the SRAMs 102, 104, and 106 are output to the HPF 52 in a predetermined order. It is assumed that the timings of the vertical synchronizing signals of the respective image sensors A, B, and C match.
[0051]
For example, first, a video signal for one horizontal scanning period of chA stored in the SRAM 102 is output to the HPF 52, and subsequently, a video signal for one horizontal scanning period of chB stored in the SRAM 104 is output to the HPF 52. Next, the video signal for one horizontal scanning period of chC stored in the SRAM 106 is output to the HPF 52. By storing the video signals output from the respective imaging devices A, B, and C at the same time in the memory in this manner, the video signals obtained by the imaging devices A, B, and C being captured at the same time are obtained. Thus, the focus evaluation values of chA, chB, and chC based on the video signal at the same horizontal scanning line position can be obtained.
[0052]
In the third embodiment shown in FIG. 10 and the fourth embodiment shown in FIG. 11, the video signal is processed by one processing unit by switching the channel every one horizontal scanning period. The channel may be switched at least each time the processing for the video signal in the necessary range, that is, the video signal in the AF frame (see FIG. 5) is completed. Further, the content of the time-division processing performed by one processing unit may be different from those of the third and fourth embodiments, and all or a part of the processing performed on the video signal is performed by the one processing unit. The present invention can be applied to the case of processing. In particular, there is an effect that only the processing of the HPF 52 is time-divisionally processed by one processing unit, and the other processing is performed by an individual processing unit for each channel.
[0053]
As described above, in the above-described embodiment, the case where the present invention is applied to the configuration of the signal processing unit 28 when three focus state detecting image pickup devices are provided has been described. The present invention can be applied not only to the case where the number of elements is three, but also to the case where there are plural elements.
[0054]
【The invention's effect】
As described above, according to the autofocus system according to the present invention, all or part of autofocus processing using a plurality of image sensors arranged at positions with different optical path lengths is time-shared by a single processing unit. Therefore, the circuit scale can be reduced, and the power consumption can be reduced.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a configuration of a television camera system to which the present invention is applied.
FIG. 2 is a configuration diagram illustrating a configuration of an imaging unit for detecting a focus state;
FIG. 3 is a diagram illustrating an image sensor for focus state detection on the same optical axis;
FIG. 4 is a block diagram illustrating a configuration of a signal processing unit that performs focus state detection processing.
FIG. 5 is a diagram illustrating an example of an AF frame with respect to a screen.
FIG. 6 is a diagram illustrating a state of a focus evaluation value in an image sensor for detecting a focus state with respect to a focus position when a certain subject is photographed.
FIG. 7 is an explanatory diagram used for explaining a focus state detection process performed by three focus state detection imaging elements;
FIG. 8 is a configuration diagram showing a first embodiment of the configuration of a signal processing unit to which the present invention has been applied.
FIG. 9 is a configuration diagram showing a second form of the configuration of the signal processing unit to which the present invention is applied;
FIG. 10 is a configuration diagram showing a third mode of the configuration of the signal processing unit to which the present invention is applied;
FIG. 11 is a configuration diagram showing a fourth mode of the configuration of the signal processing unit to which the present invention is applied;
[Explanation of symbols]
10 camera body, 12 photographing lens, F focus lens, R1 front relay lens, R2 rear relay lens, R3 relay lens, 24 half mirror, 26 imaging section, A, B, C imaging Elements, 28 signal processing unit, 30 focus motor drive circuit, 50, 60, 70, 100 A / D converter, 52, 62, 72 high-pass filter (HPF), 54, 64, 74 gate circuit, 56, 66, 76 ... adder, 80 ... synchronization signal generation circuit, 82 ... CPU, 102, 104, 106 ... SRAM

Claims (6)

Automatically adjusting the focus by controlling the focus of the photographing lens based on video signals obtained by the plurality of image sensors arranged at positions having different optical path lengths of the subject light incident on the photographing lens based on the image signals obtained by the respective image sensors. In an autofocus system provided with a focus control means performed by
An autofocus system comprising a single processing unit for processing all or a part of the same processing performed on each video signal from each of the imaging elements in a time-division manner for each video signal. . When a frame that specifies a range to be focused within the angle of view of the photographing lens is set as an AF frame, the processing unit performs processing on at least a video signal in the AF frame among video signals from one image sensor. 2. The autofocus system according to claim 1, wherein a video signal to be processed is switched to a video signal from another image sensor every time the processing is completed. The processing unit sets the frame that specifies the range to be focused within the angle of view of the photographing lens as an AF frame, and the processing unit may perform processing on some of the video signals in the AF frame from one image sensor. 2. The autofocus system according to claim 1, wherein a video signal to be processed is switched to a video signal from another image sensor every time the processing is completed. 3. The image processing apparatus according to claim 2, further comprising a storage unit configured to store a video signal from each of the imaging elements, wherein the processing unit reads out the video signal output from each of the imaging elements at the same time from the storage unit and processes the video signal. Or 3 autofocus system. 4. The autofocus system according to claim 3, wherein the switching of the video signal to be processed is performed based on a horizontal synchronization signal. 6. The autofocus system according to claim 5, wherein a vertical synchronizing signal of a video signal from each of said image sensors is shifted by a predetermined time.

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