JPH0614241A - Electronic zoom device - Google Patents

Abstract

PURPOSE:To attain a precise automatic focusing by a simple constitution to any object including a horizontal line or an oblique line by operating an electronic zoom by using a virtual picture element information on the scanning locus in a direction crossing a horizontal scanning direction. CONSTITUTION:An image pickup processing circuit 3 processes a signal from an imager 2, outputs it through a switch 4 to a recording system, and writes a luminance signal Y through an A/D converter 5 in a field memory 6. Next, virtual picture information is calculated, and a video signal which is rotated only at a prescribed angle is read from the memory 6 by the control of a read control circuit 15. The video signal is interpolated by an interpolation coefficient K by an interpolation processing circuit 7, and supplied through a BPF 13 and an integration circuit 14 to a microcomputer 12 as an evaluation value indicating a focusing level. The computer 12 drives an AF motor driver 17 based on the evaluation value, and allows it to operate a focusing operation.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic zoom device,
In particular, the present invention relates to an electronic zoom device that enables highly accurate automatic focusing on any subject during zooming. In recent years, automatic focusing (AF) based on a video signal obtained from an imager without using a separate sensor,
Automatic exposure adjustment (AE), automatic white balance (AW
A technique for performing B) and the like by digital processing has become common. As such an automatic focusing method, the high frequency components of the video signal in the focusing target area are digitally integrated, and the obtained value is used as an evaluation value indicating the degree of focusing, and this evaluation value is the maximum. There is a method of driving and controlling the AF motor so that The extraction of the high frequency component of the video signal is performed using a bandpass filter. As described above, the conventional automatic focusing control is performed based on the integrated value of the high frequency component of the video signal obtained from the imager. However, in such an automatic focusing method, since a high frequency component of a video signal of pixels in the horizontal direction is extracted, a high level high frequency component is obtained when the subject is a vertical line, but when the subject is a diagonal line. The high frequency component level decreases, and in the case of a horizontal line, high frequency components cannot be obtained,
High-precision focusing control is not possible. For example, if the subject is
In the case of the vertical line A shown in Fig. 15A, the video signal obtained from the imager has a sharp fall and rise as shown by A1 in Fig. 15A, and the signal after passing through the bandpass filter is also high like A2. It becomes a level. However,
When the subject is a slanted line as shown in B of FIG. 14, the imager output does not have a steep level change as in B1 of FIG. The signal level is lowered and the focusing accuracy is lowered. Further, in the case of a horizontal line object as shown in FIG. 14C, the imager output has only the DC component C1, and the output does not appear in the bandpass filter like C2 in FIG. The above also applies to a device having an electronic zoom operation function. As described above, in the conventional automatic focusing method, highly accurate focusing control cannot be performed when the subject is close to a diagonal line or a horizontal line. For a horizontal line subject, a bandpass filter for high-frequency component extraction is configured by a vertical filter, and a sharp level change is obtained as shown by D1 in FIG. 14, and a high level like D2 is obtained as a bandpass filter output. However, in that case, the 1H delay means is required, so that not only the circuit configuration scale becomes large, but also a problem that the shaded object cannot be dealt with occurs. Also, a technology has been proposed for rotating the entire optical system by an optimum angle with respect to an oblique line or a horizontal line object (Japanese Patent Publication No. 58-708), but the problem is that the optical system rotation mechanism is complicated and becomes large. Also occurs. The above-mentioned problem is also the same in the electronic zoom device having the electronic zoom function, and it becomes a particularly remarkable problem that the scale of the circuit and the like is further increased in addition to the functional unit for the electronic zoom. . Therefore, an object of the present invention is to realize an electronic zoom device capable of highly accurate automatic focusing with any structure including a horizontal line and a diagonal line with a simple structure. In order to solve the above-mentioned problems, the electronic zoom apparatus according to the present invention effectively scans the focusing target area in a direction intersecting the normal horizontal scanning direction. In addition, virtual pixel information that represents virtual pixel information that substantially represents a virtual pixel located on the scanning locus based on real pixel information in the raster that at least partially includes the focusing target area or this area. The calculation means and the virtual pixel information obtained by the virtual pixel information calculation means are used at least partially to effectively scan the target area to be focused in a direction intersecting the normal horizontal scanning direction. An automatic focusing means that uses information related to the range component as a focusing evaluation value,
And an electronic zoom unit that performs an electronic zoom by at least partially using the virtual pixel information obtained by the virtual pixel information calculation unit. According to the present invention, virtual pixel information on the scanning locus for effectively scanning in the direction intersecting the normal horizontal scanning direction is calculated based on the actual pixel information in the raster. Using the virtual pixel information obtained in this way, the automatic focusing operation and the electronic zooming operation are performed by applying the information related to the high frequency component in the image information obtained by the scanning in the above direction as the focusing evaluation value. . Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an electronic zoom device according to the present invention. In the present embodiment, the tilted subject image video signal is electrically rotated to the optimum angle (vertical direction), and high-accuracy high-frequency component extraction is always possible. For example, the original image shown in FIG. 2A is rotated by an appropriate angle to obtain images (B) to (F) at desired angles.
In (B), the original image (A) is rotated to obtain a subject image original image having an angle surrounded by a thick frame. At this time, the shaded area is a portion that does not exist in the original image, but since the subject image exists in the substantially central portion, no problem occurs. Also, the original image portion that extends beyond the thick frame is deleted. This embodiment uses an electronic zoom circuit,
In order to obtain a suitable focus evaluation value for vertical and diagonal lines as well, the above-described rotation processing is performed and the focus operation is performed. In FIG. 1, a subject image formed on an imager 2 such as a CCD via an optical system 1 is converted into an electric signal and input to an image pickup process circuit 3. The imaging process circuit 3 subjects the signal from the imager 2 to known signal processing, and outputs a video signal to the recording system via the terminal 4a of the switch 4. The luminance Y signal from the imaging process circuit 3 is converted into a digital signal by the A / D converter 5 and written in the field memory 6. Various synchronizing signals are generated from the SSG circuit 10 to drive the timing generator circuit 9 to control the operation of the imager 2,
The operation timing of the imaging process circuit 3 is controlled and the writing timing of the field memory 6 is controlled via the write control circuit 11. Under control of the address signal Add, a video signal rotated by a predetermined angle is read from the field memory 6 under the control of the address signal Add, subjected to interpolation processing by an interpolation coefficient K, and then D The signal is converted into an analog signal by the / A converter 8 and output to the recording system via the terminal 4b of the changeover switch 4. The signal interpolated by the interpolating circuit 7 is
The high-pass component is extracted by the bandpass filter 13, and the integrated value obtained by the integrating circuit 14 is supplied to the microcomputer 12 as an evaluation value indicating the degree of focus. Microcomputer 12
Drives the AF motor driver 17 based on the evaluation value to perform the focusing operation. The microcomputer 12 sends to the read control circuit 15 a control signal for rotating the subject image from the imager 2 by a predetermined angle. The principle of address conversion for controlling the rotation of the subject image will be described with reference to FIG. Figure 3
An address positional relationship when a thick line image is obtained by oblique scanning by rotating an original image indicated by a thin line by θ is shown. In the figure, white circles represent real pixels stored in the memory, and black circles represent virtual pixels read from the memory. Each address position P
(00), P (10), P (20), P (01), P
(11), P (21), P (02), P (12), P
(22) Corresponding pixel data is written in the field memory 6, and the pixel data at these address positions are used to rotate by θ with respect to the position P (00) as the corresponding address position Q ( 10), Q (20), Q
(01), Q (11), Q (21), ... Are obtained and sent to the field memory 6 as the address signal Add. For example, the address position Q (1
The virtual pixel addresses of 0), Q (20), Q (01), Q (11) are obtained as follows from the relationship shown in the figure. Q (10): x ... P (00) + cos θ y ... P (00) + sin θ Q (20): x ... P (00) +2 cos θ = P (10) +2 cos θ-1 y ... P (00) +2 sin θ = P (10 ) +2 sin θ Q (01): x ... P (00) -sin θ y ... P (00) + cos θ Q (11): x ... P (00) -sin θ + cos θ = P (01) -sin θ + cos θ y ... P (00) + cos θ + sin θ = P (01) + cos θ + sin θ−1 FIG. 4 shows an example of a circuit for generating the X address. A pixel address to be read first, 0 in this example, is set in the XST register 151X, and XW
XW = cos θ shown in FIG. 3 is generated from the register 152X and X shown in FIG. 3 is generated from the X0 register 153X.
0 = −sin θ has been generated. The output of the adder 154X is delayed by one clock (for one pixel) by the delay device 156X. The adder 154X adds the cos θ from the XW register 152X and the output from the delay device 156X.
The output of the delay device 156X is added to the output (0 in this example) from the XST register 151X in the adder 158X. The delay device 157X outputs the output of the adder 155X to 1
Delay by H. The adder 155X is the X0 register 15
The −sin θ from 3X and the output from the delay device 157X are added. The adder 159X adds the output of the delay device 157X and the output of the adder 158X and outputs the result as an X address signal. FIG. 5 shows an example of a circuit for generating a Y address signal similar to that shown in FIG. YST register 151Y
Is set to 0, and from the YW register 152Y, as shown in FIG.
YW = sin θ is generated, and Y0 register 153 is generated.
From Y, Y0 = cos θ shown in FIG. 3 is generated. The output of the adder 154Y is delayed by one clock (one pixel) by the delay device 156Y. The adder 154Y adds sin θ from the YW register 152Y and the output from the delay device 156Y. The output of the delay device 156Y is YST
The output (0 in this example) from the register 151Y is added by the adder 158Y. The delay device 157Y delays the output of the adder 155Y by 1H. Adder 155Y
Is the cos θ from the Y0 register 153Y and the delay unit 1
57Y and the output from 57Y are added. The adder 159Y adds the output of the delay device 157Y and the output of the adder 158Y and outputs the result as a Y address signal. FIG. 6 shows the principle of address conversion shown in FIG. 3 and the aspect ratio of 3 to 4 shown in FIG. 7 (768 pixels, 2
(40 lines), an address conversion diagram when rotated by 30 degrees is shown. In this case, as shown in FIG. 7, one pixel has a horizontal and vertical size of 2.4: 1. At this time, XST = 0 XW = 0.866 X
0 = −2.4 × 0.5 YST = 0 YW = 0.5 / 2.4 Y0 = 0.8
66, and as is clear from the figure, the general formula expressing the X address Xmn and the Y address Ymn when the number of pixels is m and the number of lines is n is as follows. Xmn = XST + m * XW + n * X0 Ymn = YST + m * YW + n * Y0 For example, the address (coordinates) of the 0th line (n = 0) is (XY) = (0,0), (0.866,0.208) ，
(1.732, 0.417), ... In the first line (n = 1), (XY) = (− 1.2, 0.866), (−0.33)
4, 1.074), (0.532, 1.28), ... Here, the integer part of each address is the address Add,
It is clear from the figure that the fractional part indicates the interpolation coefficient K. It should be noted that the calculation of the information representing the virtual pixel described above may be performed based on the real pixel information in the focusing target area or the raster that at least partially includes this area. In the embodiment shown in FIG. 1, the functional unit for calculating the virtual pixel information so that the screen is effectively scanned in the direction intersecting the horizontal scanning direction is operated in response to the operation of the zoom switch 18. It is also a functional unit for electronic zoom operation when the mom motor driver 16 is driven. In FIG. 8, the actual pixel address P (0
0), P (10), P (20), P (30), P (0
1), P (11), P (21), P (31) and virtual pixel addresses Q (00), Q (10), Q (2) after zooming.
0), Q (30), Q (40), Q (01), Q (1
1), Q (21), Q (31), and Q (41) are shown. At this time, XW and Y0 are constant values, and X0 and YW are 0. Interpolation processing for extracting high-frequency components with higher accuracy by using the band-pass filter in FIG. 1, that is, calculation of virtual pixel information is preferably a four-point weighted average method as shown in FIG. 9, for example. . The address position Q to be read from the memory is determined by defining X1 and X2 as shown in the figure, and the four surrounding points P (11), P (21), P (1
2), using the weighted average of P (22), it is calculated by the following formula. Q = (1-Ky) X1 + Ky * X2 X1 = (1-Kx) P (11) + KxP (21) X2 = (1-Kx) P (12) + KxP (22) Therefore, Q = (1-Kx) ( 1-Ky) P (11) + Kx (1-Ky) P (21) + Ky (1-Kx) P (12) + Kx · Ky · P (22) (1) The operation of the formula (1) is one cycle. 4 pixel address P in
This can be realized by reading (11), P (21), P (12), and P (22) at the same time. The simultaneous reading of the four pixels can be performed using a memory configuration as shown in FIG. 10, for example. In the example shown in FIG. 10, even columns are arranged so that four pixels can be read by supplying an address once.
Even row dedicated memory (A), odd column, even row dedicated memory (B), even column, odd row dedicated memory (C) and odd column,
Four independent memories of the odd row memory (D) are provided. FIG. 11 shows an address generating circuit for reading data from a memory for performing the operation by the above-mentioned four-point weighted averaging circuit, which is a column address 0 to 9 bits and a row address 0 to 7 bits to an odd column memory column. An address, a column address for even column memory, a row address for odd row memory, and a row address for even row memory are generated. 0 for column address
The bits are output as the select signal HSEL and added by the adder 251 with bits 1 to 9. 1 to
9 bits become the column address for the odd column memory, and the adder 2
The output of 51 becomes the column address for even column memory. Similarly, 0 bit of the row address is output as the select signal VSEL and is added by the adder 252 with 1 to 7 bits. Bits 1 to 7 become the row address for the odd row memory, and the output of the adder 252 becomes the row address for the even row memory. FIG. 12 shows an example of a circuit for performing the 4-point weighted average calculation shown in the equation (1) using the read data read from the memory. In FIG. 12, the selectors 253 and 254 are the select signals HS obtained in FIG.
When EL is "H", the "H" terminal is selected, and when it is "L", the "L" terminal is selected, and the selector 261 similarly selects the corresponding terminal by the select signal VSEL. Even-numbered-column even-row read data and odd-numbered-column even-row read data are input to the selector 253, and the selector 254 receives
Even-numbered column odd-row read data and odd-numbered column odd-row read data are input. The two outputs from the selector 253 are multiplied by the coefficients (1-K
x) and Kx are multiplied. The outputs of the multipliers 255 and 256 are added by the adder 257 and output to the 2-input terminal (L, H) of the selector 261. On the other hand, the two outputs from the selector 254 are multiplied by the coefficients (1-Kx) and Kx by the multipliers 258 and 259, respectively. Multiplier 258
The outputs of and 259 are added by the adder 260 and output to the other two input terminals (L, H) of the selector 261. The two outputs from the selector 261 are X1 and X2 described above, and the multipliers 262 and 263 respectively output the coefficient (1-K
x) and Kx are multiplied. The outputs of the multipliers 262 and 263 are added by the adder 264 to obtain the interpolated data Q. In the examples of FIGS. 11 and 12, the select signal is necessary because, as shown in FIG. 13, four address points to be selected are generated according to the four patterns # 1 to # 4. In this example, pattern # 2 is shown. As described above, according to the electronic zoom device of the present invention, the functional section relating to the electronic zoom operation,
A function unit for always enabling highly accurate focus control is used for any subject image in any tilted state, and both functions are satisfied while the configuration is greatly simplified.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an electronic zoom device according to the present invention. FIG. 2 is a diagram for explaining the principle of an automatic focusing method in the electronic zoom device according to the present invention. FIG. 3 is an address generation principle diagram showing an image rotation principle in the embodiment of the present invention. FIG. 4 is a circuit diagram for generating an X address according to the principle diagram shown in FIG. FIG. 5 is a circuit diagram for generating a Y address according to the principle diagram shown in FIG. FIG. 6 is a diagram showing an address generation principle when the principle shown in FIG. 3 is applied to actual image rotation. 7 is an image configuration diagram which is a basis of the principle diagram shown in FIG. FIG. 8 is a diagram showing a principle of an electronic zoom operation in the embodiment of the present invention. FIG. 9 is a principle diagram of performing interpolation processing by an interpolation processing circuit 7 according to an embodiment of the present invention by a 4-point weighted average calculation. 10 is a block diagram of a memory used to perform the interpolation process shown in FIG. 9. FIG. 11 is a circuit diagram showing an example of a memory read address generation circuit used in the interpolation processing shown in FIG. 9; 12 is a circuit diagram showing an example of the interpolation processing shown in FIG. 13 is a diagram showing an example of an even / odd combination of four points selected in the interpolation processing shown in FIG. FIG. 14 is a diagram showing vertical, horizontal, and diagonal subject images. FIG. 15 is a diagram showing changes in high-frequency components obtained from a bandpass filter in a conventional apparatus for each subject shown in FIG. [Explanation of Codes] 1 Optical system 2 Imager 3 Imaging process circuit 4 Changeover switch 5 A / D converter 6 Field memory 7 Interpolation processing circuit 8 D / A
Converter 9 Timing generator circuit 10 SSG circuit 11 Write control circuit 12 Microcomputer 13 Bandpass filter 14 Integration circuit 15 Read control circuit 16 Zoom motor driver 17 AF motor driver 18 Zoom switch

Claims (1)

Claims: In order to effectively scan the focusing target area in a direction that intersects a normal horizontal scanning direction, virtual pixel information representing virtual pixels located substantially on the scanning locus is provided as described above. A focusing target area or a virtual pixel information calculating unit that calculates based on real pixel information in the raster that at least partially includes this area, and the virtual pixel information by the virtual pixel information calculating section is used at least partially. An automatic focusing unit that uses, as a focus evaluation value, information related to a high frequency component in video information obtained by effectively scanning a target area in a direction that intersects a normal horizontal scanning direction, and the virtual pixel information. An electronic zoom device comprising: an electronic zoom unit that performs an electronic zoom by at least partially using the virtual pixel information calculated by the calculation unit.