JP4211170B2 - Imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an imaging apparatus suitable for use in, for example, a consumer video camera or a digital still camera. Specifically, with a consumer video camera, etc., particularly good imaging in so-called excessively forward lighting where only the subject is illuminated or so-called backlighting where the subject is illuminated from behind. This makes it possible to perform exposure control and the like efficiently and accurately.
[0002]
[Prior art]
For example, the applicant of the present application has already obtained patent rights of Japanese Patent Nos. 2869976 and 2860996 as a technique for performing imaging with excessive forward light or backlight in a video camera. That is, the techniques disclosed in these patents detect, for example, the brightness of the signal imaged by the imaging means for each section obtained by arbitrarily dividing the imaging surface, and weight each according to the brightness of each of these sections. An average value, a maximum value, and the like are calculated after addition and the like, and the diaphragm mechanism and the like are controlled based on the average value and the maximum value.
[0003]
[Problems to be solved by the invention]
However, in the technique disclosed in this publication, a detection period of one field is required for one section in order to detect the brightness of the divided sections. In addition, in order to perform weighted addition to the brightness of each section and detect the average value, it is necessary to detect all the brightness of each of the above-mentioned divided sections. It will hang. Therefore, in order to perform the above-described control, the field period corresponding to the number of divisions described above is required for each detection, and the detection cannot be performed continuously with intermittent detection.
[0004]
Alternatively, in order to detect the maximum value of the above-described brightness, for example, the brightness for each of the divided sections described above is detected, and the maximum value is determined by comparing these detection values. In that case as well, it is necessary to detect the brightness of all the divided sections in the same manner as described above, and this requires a field period corresponding to the number of divisions. Therefore, in order to perform the control using the maximum value of the brightness described above, the time of the field period corresponding to the number of divisions described above is required for each detection, and the detection is intermittently performed and the control is performed continuously. It is something that cannot be done.
[0005]
On the other hand, for example, a method for detecting the brightness of all the sections simultaneously by providing detection means for the number of divisions described above is conceivable. However, in this method, for example, when applied to the inventions of the above-mentioned Patent Nos. 2869976 and 2860996, for example, nine configurations for the detection are required. For example, when such a configuration is realized by hardware, the circuit scale becomes extremely large. Also, when such a configuration is implemented by software, a large number of registers and the like necessary for processing are required, which increases the scale of the apparatus.
[0006]
By the way, for example, as shown in FIG. 7, the imaging surface is divided into three sections of an upper section A, a central section B, and a surrounding section C, and the brightness of these sections A to C is detected by three detection means. There has been proposed an apparatus for simultaneously detecting and controlling using a computer. That is, in this apparatus, for example, control is performed using values obtained by adding the brightness of the section A to 20%, the brightness of the section B to 100%, and the brightness of the section C to 60%. Thus, for example, priority is given to control such as exposure to the subject in the center, and imaging of the subject with respect to excessive forward light and backlight is performed favorably.
[0007]
However, in this configuration, since the positions and sizes of the sections A to C for detecting the brightness are fixed, for example, when the subject departs from the section B in the central portion, imaging with excessive forward light or backlight is performed. It will not be possible to do well. In addition, when the zoom lens is used on the wide side and the subject image is small and the ratio of the image in the central section B is low, it is possible to satisfactorily capture images with excessive forward light or backlight. It becomes impossible. On the other hand, for example, in order to move the section B in the center in accordance with the movement of the subject, an extremely complicated operation or the like is required.
[0008]
This application has been made in view of the above points, and the problem to be solved is that, for example, in the case of photographing with over-order light or backlight in a video camera, detection is not possible with a conventional apparatus. It is impossible to perform intermittent control intermittently, or the scale of the apparatus becomes large to perform continuous control, and a configuration that detects brightness by setting fixed sections In the case of taking it, for example, it was impossible to perform good imaging in a situation where a relatively small subject was moving around.
[0009]
[Means for Solving the Problems]
Therefore, in the present invention, the brightness of each section obtained by arbitrarily dividing the imaging surface of the imaging unit is detected by the first detection unit, and the section where the detected value indicates the maximum value or the minimum value is determined. The brightness of the determined section is detected by the second detection means and exposure control or the like is performed. According to this, a small subject is set by setting each section to a small size with a relatively small circuit scale. In addition, it is possible to perform good detection with respect to the image, and it is possible to perform imaging with excessive forward light and backlight well even in a situation where the subject moves around in a plurality of sections.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
That is, the present invention provides an image pickup means for performing image pickup by exposing image light from a subject, a signal conversion means for sample-holding and analog / digital conversion of a signal picked up by the image pickup means, and a signal conversion means for conversion. An image pickup apparatus comprising: a signal processing means for forming a video signal from the received signal, wherein the image pickup means performs exposure control of image pickup and / or performs signal gain control by the signal conversion means; and First detection means for detecting the brightness of the imaged signal for each section obtained by arbitrarily dividing the imaging surface, and the divided section in which the value detected by the first detection means indicates the maximum value or the minimum value. And a second detection means for detecting the brightness of the imaged signal of the section determined by the determination means, and the control means according to the detection output of the second detection means Dew at It is made by performing the control and / or gain control.
[0011]
Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing an embodiment of a video camera to which an imaging apparatus according to the present invention is applied.
[0012]
In FIG. 1, for example, image light 10 from a subject (not shown) is irradiated onto an image pickup surface of an image pickup element 14 made of, for example, a CCD through a zoom lens 11, a diaphragm mechanism 12, and a focus lens 13. The zoom lens 11 to the imaging element 14 constitute an imaging unit 100. Further, an image signal from the image sensor 14 is supplied to the analog / digital converter 17 through the sample hold circuit 15 and the variable gain amplifier 16. These sample and hold circuits 15 to analog / digital converter 17 constitute a signal conversion means 200.
[0013]
Further, the signal converted by the analog / digital converter 17 is supplied to the matrix constituting the signal processing means 300 for forming the video signal and the γ correction circuit 18, and the formed video signal is taken out to the output terminal 19. It is. The signal from the analog / digital converter 17 is also supplied to the brightness detection circuit 20 built in the signal processing means 300, and the brightness detection circuit 20 detects the level of the imaging signal from the imaging means 100. A signal from the brightness detection circuit 20 is supplied to a microcomputer 21 as system control means for the entire apparatus.
[0014]
Thereby, in the microcomputer 21, the level of the imaging signal in the imaging means 100 detected by the brightness detection circuit 20 is processed. Based on the calculation result, the diaphragm mechanism 12 and the variable gain amplifier 16 are controlled, and the accumulation time of the image sensor 14 is controlled through the timing generation circuit 22. In other words, by this control, exposure control of imaging by the imaging unit 100 and signal gain control by the signal conversion unit 200 are performed. In addition to this, exposure control of imaging by the imaging unit 100 can also be performed using a so-called ND filter or the like.
[0015]
Further, in accordance with a control signal from the microcomputer 21, the zoom lens 11 is driven in accordance with a user operation (not shown) and the focus lens 13 is controlled such as automatic focus adjustment. Further, a control signal from the microcomputer 21 is supplied to the matrix and γ correction circuit 18 to perform control such as white balance adjustment. Further, the control signal from the microcomputer 21 is also supplied to the brightness detection circuit 20, for example, for each of the sections A to H and the sections A 'to H' obtained by dividing the imaging surface of the image sensor 14 as shown in FIG. Brightness detection is performed.
[0016]
That is, from the microcomputer 21, for example, as indicated by arrows in FIG. 2 above, frames 0 and 1 for scanning each section are designated, and signals captured in the sections designated by the frames 0 and 1 are captured. Brightness is detected. For example, detection is performed using a detection period of one field. In this embodiment, frame 0 and frame 1 are designated at the same time, and detection is performed simultaneously using two detection means. As a result, two sections are detected in one field. Further, this detection signal is supplied to the microcomputer 21, and the section where the detection value indicates the maximum or minimum is determined.
[0017]
Further, from the microcomputer 21, the frame 2 of the determined section is specified, and the brightness of the signal imaged in the section specified by the frame 2 is detected. This detection is performed for each field. Then, this detection signal is supplied to the microcomputer 21, and in accordance with this detection signal, the above-described exposure control of imaging by the imaging unit 100 and / or the gain control of the signal by the signal conversion unit 200 are performed. Therefore, according to this embodiment, the determination of the section indicating the maximum or minimum is performed, for example, every 8 fields, and the brightness of the determined section is detected for each field.
[0018]
FIG. 3 shows a flowchart of an embodiment of processing performed by the microcomputer 21 described above. In FIG. 3, the start position of the field is determined at step [1]. When the start position is reached, serial communication with the signal processing means 300 is performed at step [2]. Then, in step [3], an evaluation value obtained by dividing the brightness detection values of the above-described frame 0, frame 1, and frame 2 by the area of the section corresponding to each frame is obtained. In step [4], the obtained evaluation value is stored in a corresponding array of a register (not shown).
[0019]
In step [5], it is determined whether frame 0 and frame 1 have scanned one screen. If “Yes” in which scanning for one screen has been performed, a section indicating the maximum or minimum of the evaluation value stored in the register is determined in step [6]. That is, according to the above-described embodiment, the determination of the section indicating the maximum or minimum is performed, for example, every 8 fields. In this step [6], for example, the determination of the section having the maximum evaluation value is executed by, for example, a subroutine shown in FIG. FIG. 4 shows a flowchart of an embodiment of this subroutine.
[0020]
In FIG. 4, first, in step [21], the value of each register [A-MAX] [A-MAX-No] [B-MAX] [B-MAX-No] [counter] is set to "0". Next, in step [22], the evaluation value stored in the array indicated by the value of the register [counter] in the frame 0 among the evaluation values stored in the register (not shown) is stored in the register [A]. The evaluation value stored in the array indicated by the value of the register [counter] in the frame 1 among the evaluation values stored in the register (not shown) is written in the register [B].
[0021]
In step [23], it is determined whether or not the value of the register [A] is larger than the value of the register [A-MAX]. If this determination is “Yes”, the value of the register [A] is written to the register [A-MAX] in step [24], and the value of the register [counter] is written to the register [A-MAX-No]. . If the determination in step [23] is "No", the process proceeds directly to the next step [25]. As a result, the registers [A-MAX] and [A-MAX-No] store the value and the array value of the position when the evaluation value increases.
[0022]
In step [25], it is determined whether the value of the register [B] is larger than the value of the register [B-MAX]. If this determination is "Yes", the value of the register [B] is written to the register [B-MAX] and the value of the register [counter] is written to the register [B-MAX-No] in step [26]. . Further, when the determination in step [25] is “No”, the process proceeds to the next step [27]. As a result, the registers [B-MAX] and [B-MAX-No] store the value and the value of the array of positions when the evaluation value increases.
[0023]
In step [27], the value of the register [counter] is incremented by "+1". In step [28], it is determined whether or not the value of the register [counter] is, for example, "8" or more. When this determination is “No”, the process returns to step [22], and the processes of steps [22] to [27] described above are repeated, for example, eight times in the above-described embodiment. Therefore, when the determination in step [28] is "Yes", the registers [A-MAX] [A-MAX-No] and [B-MAX] [B-MAX-No] have maximum evaluation values respectively. The value and the value of the array at that position are stored.
[0024]
In step [29], it is determined whether or not the value of the register [A-MAX] is larger than the value of the register [B-MAX]. When this determination is “Yes”, the frame 0 has the maximum brightness value in step [30], and the section of the maximum value is set as the position of the value of the register [A-MAX-No]. On the other hand, when the determination in step [29] is "No", in step [31] there is a maximum brightness value in frame 1, and the section of the maximum value is the register [B-MAX-No]. The position of the value of. Further, after this processing, the process is returned to the main routine.
[0025]
Therefore, in the main routine, the process proceeds to step [7] when step [6] is completed and when “No” in step [5] described above. In this step [7], the difference between the evaluation value of the frame 2 and the brightness target value is obtained. In step [8], control values to the timing generation circuit 22 and the like for determining the accumulation time of the diaphragm mechanism 12, the variable gain amplifier 16, and the image sensor 14 are determined from the difference from the obtained target value. Calculated.
[0026]
In step [9], the positions and sizes of the frames 0 and 1 corresponding to the next detected section are set using an arbitrary table or the like. In step [10], the position and size of the frame 2 corresponding to the section having the maximum brightness obtained in step [6] are set. In step [11], control values to the diaphragm mechanism 12, variable gain amplifier 16, timing generation circuit 22 and the like calculated in step [8] are output, and the process returns to step [1]. Accordingly, in the next field, processing is performed for frame 0, frame 1 and frame 2 set in steps [9] and [10] described above, and this processing is repeated in sequence.
[0027]
Thus, in this apparatus, for example, the detection of the frame 0 and the frame 1 is shown for the sections A to H and the sections A 'to H' shown in FIG. 2 for the vertical synchronizing signal (VD) shown in the upper part of FIG. [Frame 0] [Frame 1] is performed as shown in the item. The communication of the detected value from the signal processing means 300 to the microcomputer 21 and the communication for setting the frame 0 and the frame 1 from the microcomputer 21 to the signal processing means 300 are respectively shown as [serial communication 0] [serial communication]. 1] is performed. In addition, the arrow in a figure shows the direction of each communication and a character shows the communication content.
[0028]
Further, the microcomputer 21 sets the sections A to H and the sections A ′ to H ′ detected by the frame 0 and the frame 1 as shown in the items of “setting 0” and “setting 1”. Here, for example, the section B set at the left end of the drawing is communicated to the signal processing means 300 as a frame setting (B) in the next field, and further detection is performed in the next field. Communication is made to the microcomputer 21 in the next field. In this way, the detected value of the set section is obtained after three fields set by the microcomputer 21.
[0029]
For example, when the detection values (H) (H ') of the sections H and H' are supplied to the microcomputer 21, the detection values (A) to (H) (A ') to (H') up to that point The partition showing the maximum value of is determined. Further, the determined section is set as shown in the item [Setting 2], and this section is communicated to the signal processing means 300 as a frame setting as shown in the item [Serial communication 2] in the next field. Is done. As a result, the detection of the frame 2 is performed as shown in the item [frame 2] in the figure, and the detection values of the sections set after three fields where the setting has been made are obtained.
[0030]
In this way, according to this apparatus, for example, the brightness of each section obtained by multiplying the entire imaging surface by 16 fields by multiplying 8 fields is detected, and the brightness of each section from the third field is detected for the section where the maximum value is detected. Is detected. Based on this detection value, control values for the above-described aperture mechanism 12, variable gain amplifier 16, and timing generation circuit 22 for determining the accumulation time of the image sensor 14 are calculated. The exposure control and / or signal conversion means 300 performs signal gain control and the like.
[0031]
That is, according to this apparatus, since detection is performed using, for example, a section obtained by dividing the imaging surface into 16 parts, the brightness of the subject can be accurately captured even when the subject is relatively small. Further, by determining the section where the brightness is the maximum value, it is possible to follow the section where the detection is performed even in a situation where the subject moves around the plurality of sections. Further, since the brightness is detected in each field for the section where the brightness is the maximum value, the detection is continuously performed and the control without interruption can be performed.
[0032]
Furthermore, in the above-described embodiment, two first detection means for detecting the brightness of the 16 divided sections and one second detection means for detecting the brightness of the section showing the maximum value, a total of 3 Although detection is performed using a single detection means, this can be performed using, for example, the same configuration as the apparatus described with reference to FIG. On the other hand, it is also possible to use one first detection means and determine the section where the brightness is the maximum value every 16 fields. Alternatively, it is possible to make three first detection means and make the discrimination every 16/3 field, or further subdivide the section into 24 divisions.
[0033]
On the other hand, in the above-described embodiment, when the section where the brightness shows the maximum value changes, there is a delay of 11 fields at the maximum before the detection in that section is started. For this, for example, as shown in FIG. 6, detection is performed by enlarging the range of the section where the brightness is detected in the frame 2 around the above-described 16 divided sections A to H and A ′ to H ′. Can be. According to this, even if the section where the brightness is maximum is changed to the adjacent section, the detection can be continued, and the problem within the delay time until the detection in the section is started can be solved. Can do.
[0034]
That is, for example, by using the frame 2 shown in FIG. 6, when the same subject is moving, even if the subject moves to the adjacent section, the detection in the previous section is performed as long as it is within the above-described enlargement range. It can be carried out. Then, detection in the next section is started with a delay within 11 fields, and detection can be continued as long as the subject does not move at an excessively high speed. In addition, it is possible to give hysteresis to the switching of the sections, and for this reason, it is possible to perform stable detection even for an object on the boundary of the sections, for example.
[0035]
Furthermore, in the above-described embodiment, the maximum value of brightness is detected. This is effective, for example, in the case of detecting so-called over-order light in which only a subject is illuminated with strong illumination. That is, in this case, for the subject that is too bright in so-called over-order light, the above-described imaging exposure control and imaging control are performed by the imaging unit 100 so that the maximum value of the brightness becomes an appropriate size. The signal conversion means 300 performs signal gain control and the like. As a result, it is possible to satisfactorily photograph a subject placed in excessively forward light.
[0036]
On the other hand, for example, detection of so-called backlight that is illuminated from behind the subject can also be performed using the above-described apparatus. In that case, the minimum value of brightness is detected in the above-described frame 0, frame 1, and frame 2, respectively. In the detection, first, the value of the register [A-MAX] [B-MAX] is set to "FFh" (in the case of 8-bit data) in step [21] in FIG. ] [25], it is possible to determine whether the value of the register [A] [B] is smaller than the value of the register [A-MAX] [B-MAX]. As a result, exposure control or the like can be performed so that the brightness of a subject that is dark in so-called backlight is moderate.
[0037]
Therefore, in the above-described apparatus, the brightness of each section obtained by arbitrarily dividing the imaging surface of the imaging means is detected by the first detection means, and the section where the detected value indicates the maximum value or the minimum value is determined. By detecting the brightness of the determined section by the second detection means and performing exposure control or the like, it is possible to detect small subjects with a relatively small circuit scale by setting each section small. In addition, it is possible to perform imaging with excessive forward light and backlight even in a situation where the subject is moving around across a plurality of sections.
[0038]
For this reason, for example, when shooting with over-order light or backlight in a video camera, the conventional apparatus cannot perform continuous control with intermittent detection, or to perform continuous control. If the configuration is such that the scale of the device increases and the brightness is detected by setting fixed sections, for example, good imaging in a situation where a relatively small subject is moving around According to the present invention, these problems can be easily solved.
[0039]
Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
[0040]
【The invention's effect】
Therefore, according to the invention of claim 1, the brightness of each section obtained by arbitrarily dividing the imaging surface of the image pickup means is detected by the first detection means, and the detected value indicates the maximum value or the minimum value. The brightness of the determined section is detected by the second detection means and exposure control or the like is performed, so that each section can be set small with a relatively small circuit scale even for a small subject. In addition to being able to perform good detection, it is possible to perform imaging with excessive forward light and backlight well even in a situation where the subject is moving around a plurality of sections.
[0041]
For this reason, for example, when shooting with over-order light or backlight in a video camera, the conventional apparatus cannot perform continuous control with intermittent detection, or to perform continuous control. If the configuration is such that the scale of the device increases and the brightness is detected by setting fixed sections, for example, good imaging in a situation where a relatively small subject is moving around According to the present invention, these problems can be easily solved.
[0042]
Furthermore, according to the invention of claim 2, the exposure control in the image pickup means is performed by controlling the diaphragm mechanism provided in the image pickup means and / or the accumulation time of the image pickup means, so that it can be satisfactorily caused by over-order light and backlight. Imaging can be performed.
[0043]
According to the invention of claim 3, the brightness of the imaged signal for determining the section showing the maximum value or the minimum value is detected by sequentially scanning each divided section every predetermined period. The detection of the brightness of the picked-up signal for performing exposure control and / or gain control is performed repeatedly at a relatively small circuit scale by repeatedly performing the determined section every predetermined period. It is something that can be done.
[0044]
Further, according to the invention of claim 4, the brightness of the imaged signal for determining the section showing the maximum value or the minimum value is detected, and the plurality of divided sections are simultaneously imaged. By scanning different portions of the image pickup surface of the means in order for each predetermined period, it is possible to determine the section for detecting the brightness in a short time.
[0045]
According to the invention of claim 5, by detecting the brightness of the imaged signal for performing exposure control and / or gain control for a section arbitrarily enlarged around the determined section, Even when a zone for detecting the brightness includes a delay time and the zone for detecting the brightness changes, the brightness can be detected satisfactorily.
[0046]
According to the sixth aspect of the present invention, when the image pickup by the image pickup means is over-ordered light, the determination means determines the section showing the maximum value and performs exposure control and / or gain control, thereby This makes it possible to satisfactorily shoot a subject placed in light.
[0047]
According to the seventh aspect of the present invention, when the image pickup by the image pickup means is backlit, the section showing the minimum value is discriminated by the discrimination means and exposure control and / or gain control is performed, so that It is possible to satisfactorily shoot a dark subject.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an embodiment of an imaging apparatus to which the present invention is applied.
FIG. 2 is a diagram showing a section of an imaging surface for explanation.
FIG. 3 is a flowchart for explaining the operation.
FIG. 4 is a flowchart for explaining the operation.
FIG. 5 is a diagram for explaining the operation;
FIG. 6 is a diagram illustrating a section of an imaging surface for explanation.
FIG. 7 is a diagram illustrating a section of an imaging surface for explaining the related art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 100 ... Imaging means, 200 ... Signal conversion means, 300 ... Signal processing means, 10 ... Image light, 11 ... Zoom lens, 12 ... Aperture mechanism, 13 ... Focus lens, 14 ... Imaging element, 15 ... Sample hold circuit, 16 ... Variable gain amplifier, 17 ... analog / digital converter, 18 ... matrix and gamma correction circuit, 19 ... output terminal, 20 ... brightness detection circuit, 21 ... microcomputer, 22 ... timing generation circuit

Claims (7)

Imaging means for performing imaging by exposing image light from a subject;
Signal conversion means for sample-holding and analog / digital conversion of a signal imaged by the imaging means;
An image pickup apparatus comprising signal processing means for forming a video signal from the signal converted by the signal conversion means,
Control means for performing exposure control of imaging by the imaging means and / or for controlling signal gain by the signal converting means;
First detection means for detecting brightness of the imaged signal for each section obtained by arbitrarily dividing the imaging surface of the imaging means;
A discriminating means for discriminating the divided section in which the value detected by the first detecting means shows the maximum value or the minimum value;
Second detection means for detecting the brightness of the imaged signal of the section determined by the determination means;
Performing the exposure control and / or the gain control in the control means according to the detection output of the second detection means,
An imaging apparatus characterized by that. The imaging device according to claim 1,
An image pickup apparatus characterized in that the exposure control in the image pickup means is performed by controlling an aperture mechanism provided in the image pickup means and / or an accumulation time of the image pickup means. The imaging device according to claim 1,
The detection of the brightness of the imaged signal for determining the section showing the maximum value or the minimum value is performed by sequentially scanning each of the divided sections every predetermined period,
An image pickup apparatus, wherein the brightness of the imaged signal for performing the exposure control and / or the gain control is detected by repeating the determined section every predetermined period. The imaging device according to claim 3.
Detection of the brightness of the imaged signal for determining a section showing the maximum value or the minimum value is performed simultaneously with a plurality of the divided sections, and the plurality of sections are on the imaging surface of the imaging unit. An imaging apparatus, wherein different portions are scanned in order for each predetermined period. The imaging device according to claim 1,
An imaging apparatus, wherein brightness of the imaged signal for performing the exposure control and / or the gain control is detected for a section arbitrarily enlarged around the determined section. The imaging device according to claim 1,
An image pickup apparatus characterized in that when the image pick-up by the image pick-up means is excessively forward light, the exposure control and / or the gain control is performed by discriminating a section showing the maximum value by the determination means. The imaging device according to claim 1,
An image pickup apparatus, wherein when the image pick-up by the image pick-up means is backlit, the exposure control and / or the gain control is performed by discriminating a section showing the minimum value by the discrimination means.

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