JP3639542B2 - Focus determination device and focus determination method for video camera with autofocus function - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a focus determination device and a focus determination method for a video camera with an autofocus function.
[0002]
[Prior art]
In an autofocus camera manufacturing process, there is an inspection apparatus disclosed in, for example, Japanese Patent Application Laid-Open No. 10-39195, as an inspection apparatus having an automatic focus adjustment function that can reduce inspection time with space saving and high accuracy.
[0003]
FIG. 10 shows the configuration of the inspection apparatus disclosed in Japanese Patent Laid-Open No. 10-39195.
[0004]
This inspection apparatus performs an automatic focusing function inspection of an AF single-lens reflex camera 33 including an AF mechanism that optically detects an image of the chart 41 and a camera lens 32 that operates according to the position of the detected image. The apparatus includes a base unit 20 on which the AF single-lens reflex camera 33 is mounted, a measurement lens 31 disposed between the chart 41 and the camera lens 32, and a front focal point of the measurement lens 31. A chart axis stage 42 that moves the chart 41 and a rotation amount detector 51 that detects the rotation amount of the distance ring of the camera lens 32 are configured to rotate the operation amount of the camera lens 32 according to the movement amount of the chart 41. This is a method of detecting by the quantity detector 51.
[0005]
[Problems to be solved by the invention]
Since the inspection apparatus disclosed in Japanese Patent Laid-Open No. 10-39195 is an inspection apparatus dedicated to a film type camera, the focus detection is also the lens rotation position detection and is not affected by the change in the illuminance of the chart.
[0006]
However, when used for a video camera with an autofocus function, since the defocus amount of the video camera is detected at the frequency component level of the video signal, the video output also changes due to a change in illuminance. As a result, since the detection level changes in proportion, there is a problem that the illuminance slightly changes when the illumination or the chart around the inspection apparatus moves on the stage.
[0007]
Also, the focus level after following the subject at each distance stops the tracking function, and the inspector changes the focus level of the subject reflected on the TV monitor by turning the distance ring of the video camera left and right by a small amount by hand. There is a problem that it is necessary to visually determine whether or not the best focus is within an allowable range.
[0008]
Here, the focus determination of the video camera with an autofocus function is conventionally performed by arranging a subject in a form as shown in FIG. 11, for example. In this case, each distance (1 m, After focusing on one of the subjects (5 m and 10 m), it is necessary to manually turn the distance ring of the video camera to find the best focus position. Moreover, it is necessary to shake the video camera according to the subject at each distance.
[0009]
The present invention has been made to solve the above problems, and a conventional series of operations in which an inspector manually searches for the best focus position by turning the distance ring and inspects it is simplified. The purpose of the present invention is to provide a focus determination device and a determination method for a video camera that can greatly improve measurement accuracy and have a high inspection speed by suppressing illuminance change due to movement of the chart.
[0010]
[Means for Solving the Problems]
The present invention is a focus determination device used for performing a focus determination inspection at the time of autofocus tracking in a production process of a video camera with an autofocus function, and includes a pseudo subject (chart) and a light source for illumination. an inspection device unit, before Symbol comprises means for moving control the position of the pseudo object, along with make pseudo to the inspection apparatus portion of each distance of an object to be used for focus determination of a video camera to be measured, the position of each distance The pseudo subject is moved by a minute amount in the front-rear direction, and the focus position for each distance is inspected from the signal from the control unit of the video camera to be measured .
[0011]
According to the focus determination device of the present invention, it is possible to make each distance of the subject in the inspection apparatus unit in a pseudo manner, and to perform the inspection of the best focus position for each distance by moving the position of the pseudo subject. The confirmation of defocusing at a finite distance at a plurality of positions followed by the autofocus lens can be determined without shaking the video camera to the subject at each distance and without manually turning the distance ring of the video camera.
[0012]
In the focus determination device of the present invention, it is preferable that the entire inspection device unit is covered with a dark black box whose inner surface is matte. By covering the inspection device with a dark box, it is possible to determine the focus that is not affected by the external illumination conditions.
[0013]
In the focus determination apparatus of the present invention, it is preferable to illuminate a pseudo subject built in the inspection apparatus unit with a ring illuminator. When a ring illuminator is used to illuminate the pseudo subject, it is not necessary to adjust the illuminance level for each movement position when the pseudo subject is moved.
[0014]
Examples of the pseudo subject used in the focus determination device of the present invention include a Siemens chart or an Inmega chart.
[0015]
The focus determination method of the present invention is a method for determining the focus of a video camera with an autofocus function using the focus determination apparatus having the above-described characteristics, and the pseudo subject is minutely moved in the front-rear direction at each distance position. It is characterized in that a focus determination inspection is performed by obtaining a best focus position within the operation range in the front-rear direction from a signal from the control unit of the video camera to be measured when it is moved by an amount .
[0016]
In the focus determination method of the present invention, a moving speed when the pseudo subject is moved by a minute amount in the front-rear direction at the position of each distance is made faster than the autofocus follow-up speed of the video camera.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0018]
FIG. 1 is an overall configuration diagram of an embodiment of a focus determination apparatus of the present invention.
[0019]
The focus determination apparatus in FIG. 1 is an apparatus whose inspection target is a video camera unit 14, a personal computer that performs control of the inspection apparatus unit 15 and control of the inspection apparatus unit 15 and calculation of defocus amount data from the video camera unit 14. It is comprised by the control part 11.
[0020]
The inspection device unit 15 includes a chart 2 as a pseudo finite distance subject, a ring illuminator 3, a magnifying lens 4, a stage 12, an illumination cover 13, and the like.
[0021]
Unlike the film camera inspection device, the inspection device unit 15 uses the output data of the frequency component in the video signal from the image obtained by imaging the chart 2 as a defocus amount for focus determination.
[0022]
In the present embodiment, since the illuminance of the chart 2 is affected by the data of the defocus amount, the inner surface of the inspection apparatus unit 15 is shielded from external light. Cover with 1. Further, the ring illuminator 3 is fixed to the stage 12 of the chart 2 at an appropriate distance so that the chart 2 is always maintained at a constant illuminance by illumination by the ring illuminator 3 (for example, a fluorescent lamp circle line). . At this time, the center of the ring illuminator 3 is placed on the optical axis 16 (the optical axis of the magnifying lens 4) so that the entire chart 2 is uniformly irradiated, and light from the ring illuminator 3 leaks to the video camera unit 14 side. The lighting cover 13 is attached so that there is not. By adopting this method, measurement accuracy is improved even in inspection work in a relatively bright or dark work place.
[0023]
The stage 12 of the inspection apparatus unit 15 is provided to be movable back and forth in a direction parallel to the optical axis 16. The stage 12 includes a moving mechanism (not shown) composed of, for example, a ball screw and a motor, and moves in the front-rear direction (in the direction of the arrow in FIG. 1) according to a signal from the personal computer control unit 11. It is configured. As the stage 12 moves, the chart 2 and the ring illuminator 3 move back and forth on the optical axis 16.
[0024]
A video output from the video camera unit 14 to be measured and defocus amount data from the camera DSP (DIGITAL SIGNAL PROCESSOR) unit 8 are sent to the personal computer control unit 11.
[0025]
The camera microcomputer control unit 7 incorporated in the video camera unit 14 to be measured is set to the test mode, and the personal computer control unit 11 instructs the inspection device unit 15 to indicate each position (X1, X2, X3) of the chart 2. Control. The camera lens control unit 6 detects the auto focus operation for each distance, the distance ring 5 is activated, and the operation of the camera lens unit 10 is stopped.
[0026]
In this embodiment, in order to find the best focus position, the chart 2 is moved at a high speed by a minute amount in the front-rear direction at each distance. At this time, based on the defocus amount data from the video camera unit 14, the best focus position within the front and rear operation range is calculated, and the reference value (how much the defocus amount peak value is shifted from the position of the chart 2) is calculated. Value).
[0027]
2 and 3 show the relationship of the back-and-forth movement of the chart 2 at each distance (X1 to X3) as a trajectory.
[0028]
In FIGS. 2 and 3, for example, when moving from X3 (for example, 10 m) to X2 (for example, 5 m) (low speed), the autofocus of the video camera unit 14 follows. Autofocus does not follow when moving (high speed).
[0029]
The defocus amount from the video camera unit 14 changes corresponding to the movement amount of the chart 2. The focus determination is performed by calculating how many mm the best focus position of the change range is from the center of X1 (for example, 1 m), X2 or X3.
[0030]
Specifically, the position data of the personal computer control unit 11 and the best point signal signal-processed by an analog digital board (not shown) built in the personal computer control unit 11 are added, and the position calculated by the calculation is best. It is determined that the focus position is Xp, the focus position of the video camera is Xc, and Xp−Xc = ΔX is the focus shift amount.
[0031]
Here, the focus determination inspection after autofocus tracking of a conventional video camera is aimed at the chart 2 at a certain distance X1, and when the autofocus function is operated, the camera lens 10 immediately reacts to focus on the chart 2 of X1. Combine. At that time, it is inspected where the focus is exactly with respect to the center distance X1. At the time of this inspection, the autofocus mode is removed, and a predetermined minute amount is turned by hand from the center to the left and right directions to read the scale of the distance ring 5 at a position where the pattern of the chart 2 of the video image is clear. It is done by the method.
[0032]
When this is performed in the present embodiment, the chart 2 at a certain distance X1 is focused by the autofocus function of the video camera unit 14, and then the chart 2 is moved in the front-rear direction by a minute amount at the position X1. This is the same as the operation of turning the distance ring 5 to the left and right in the conventional manner. In addition, the autofocus function does not respond to a chart that moves faster than a certain speed, and the tracking circuit (not shown) built in the camera does not react. Does not work. This is the same as the operation of removing the autofocus mode performed in the conventional method. Accordingly, the movement of turning the distance ring 5 can be eliminated by moving the chart 2 back and forth at high speed during the focus determination inspection.
[0033]
Further, in the present embodiment, when the chart 2 is shot by the video camera unit 14, the Siemens chart 19 (the chart design is a black wedge-shaped design with large black and white contrast) as shown in FIG. The condition that the high frequency component is easily superimposed on the luminance signal in the video camera unit 14 is created.
[0034]
There are two types of symbols in Chart 2, as shown in FIG. One of them is an Inmega chart 18 (FIG. 4A) as a chart that makes it easy to extract the frequency component that is the basis of the defocus amount signal from the video camera unit 14, and the other is to extract the frequency component further. FIG. 4B is a Siemens chart 19 (FIG. 4B) that is easy to determine the best focus even if the inspector looks at the picture taken.
[0035]
In this embodiment, the image of the chart 2 that has entered through the camera lens 10 of the video camera unit 14 is converted into a video signal (color signal) and passes through the CCD encoder unit 9 that encodes the color signal and the luminance signal. A signal which is input to the camera DSP unit 8 and from which the frequency component of the luminance signal in the camera DSP unit 8 is separated is extracted. The signal (a part of this signal is used for the autofocus function used in the camera lens control unit 6) is input to the analog-digital board of the personal computer control unit 11 as a defocus amount and converted into a digital signal. The relationship between the movement distance of the chart 2 and the focus position is calculated and determined. This is the same as the operation in which the inspector looks at the video monitor, determines the best focus position from the focus change amount of the chart 2 and reads the scale of the distance ring 5 in the conventional video camera determination method.
[0036]
FIG. 5 is a perspective view showing the internal structure of the inspection apparatus unit 15.
[0037]
As described above, in the present embodiment, among the functional components constituting the inspection apparatus unit 15, the whole excluding the magnifying lens 4 on the video camera unit 14 side is covered with the dark box 1 and shielded from outside light. Yes.
[0038]
Further, in order to prevent the illuminance of the chart 2 from being changed due to light fluctuations and further to prevent the illuminance from being changed by movement of the chart 2, the chart of the ring illuminator 3 installed at a certain distance in front of the chart 2 is provided. The illumination cover 13 is attached so that the output light of the ring illuminator 3 does not directly affect the video camera unit 14. In FIG. 5, the ring illuminator 3 is illustrated as being shifted from the illumination cover 13, but in reality, the ring illuminator 3 is accommodated in the illumination cover 13. By making the illumination light source of the chart 2 into a ring shape as in the present embodiment, the imaging of the chart 2 on the optical axis 16 is not hindered. The illumination light source may be a point light source arranged in a ring shape.
[0039]
6 and 7 are flowcharts showing the operation of this embodiment.
[0040]
The personal computer control unit 11 receives the defocus signal from the video camera unit 14, and the program operates and calculates to determine the focus, and controls the movement operation of the chart 2. The processing operation will be described below.
[0041]
Step S1: The program of the personal computer control unit 11 is activated.
[0042]
Step S2: Input conditions for operating the inspection apparatus unit 15 and inspection determination value data.
[0043]
Step S3: The chart 2 (subject) is moved to the origin position in order to prepare for focus determination.
[0044]
Step S4: When a preparation start signal is input from a conveyor (not shown) of a production line of a video camera with an autofocus function, a focus determination inspection operation is started.
[0045]
Step S5: The chart 2 moves to a predetermined distance X3 by the control from the personal computer control unit 11.
[0046]
Step 6: After following the chart 2 at the position X3 by the autofocus function of the video camera unit 14, the tracking operation is stopped.
[0047]
Step 7: After stopping at the predetermined distance X3, after a predetermined time, the chart 2 is moved back and forth by a predetermined minute amount around the position of X3 and returned to X3.
[0048]
Step 8: The personal computer control unit 11 receives the defocus amount data from the video camera unit 14 during the operation of step S7, calculates the peak focus position from the data, and determines the defocus amount.
[0049]
Step S9: The chart 2 stops moving to a predetermined distance X2 by the control from the personal computer control unit 11.
[0050]
Step S10: After the tracking operation by the autofocus function of the video camera unit 14, it stops. When the chart 2 is stopped in this step, the defocus amount matches the focus defocus amount of the video camera unit 14 as shown in FIG.
[0051]
Step S11: After stopping at a predetermined distance X2, a predetermined minute amount is moved back and forth around the position of X2 after a predetermined time and returned to X2.
[0052]
Specifically, after the chart 2 stops at the distance X2, as shown in FIG. 3A, the chart 2 first moves toward the video camera unit 14 (to the left in FIG. 3A). Next, the chart 2 moves in the opposite direction (moves in the right direction in the figure), returns to the position of Xc (= X2) again through the peak position via the best focus position. During this time, the video camera performs a focus search operation as shown in FIG. The best focus position Xp of the chart 2 coincides with the peak value of the defocus amount. The time from step 10 to step 11 is about 1 second.
[0053]
Step S12: The personal computer control unit 11 receives defocus amount data from the video camera unit 14 during the operation of step S11, and calculates the peak focus position from the data to determine the focus shift amount.
[0054]
Step S13: The chart 2 moves to a predetermined distance X1 by the control from the personal computer controller 11, and stops.
[0055]
Step S14: After the tracking operation by the autofocus function of the video camera unit 14, the operation is stopped.
[0056]
Step S15: After stopping at a predetermined distance X1, a predetermined minute amount is moved back and forth around the position of X1 after a predetermined time and returned to X1.
[0057]
Step S16: During the operation in step S15, the personal computer control unit 11 receives the defocus amount data from the video camera unit 14, calculates the peak focus position from the data, and determines the focus shift amount.
[0058]
Step S17: Accumulation data for a predetermined distance X3 to X1 is stored, and comprehensive determination is performed.
[0059]
Step S18: A pass or fail mark is displayed on the table carrying the video camera to be inspected for the next work process based on the comprehensive determination result.
[0060]
In the above processing, the specific processing of step S7 (back and forth movement at distance X3) and step S15 (back and forth movement at distance X1) has been described in step S11 (back and forth movement at distance X2). Same as processing.
[0061]
FIG. 8 is an optical principle diagram showing the relationship between the position of the chart 2 as a pseudo subject and the chart 17 of a long-distance point to be inspected (an imaginary position that does not actually exist).
[0062]
As can be seen from this figure, in the present embodiment, a chart 17 of far-distance points to be inspected by the video camera unit 14 can be made in a pseudo manner within the focal length of the magnifying lens 4. Therefore, viewing the pseudo distance chart 2 from the video camera unit 14 through the magnifying lens 4 is the same as viewing the actual far distance point chart 17.
[0063]
According to the above embodiment, each distance of the subject is artificially created in the inspection apparatus unit 15, and as shown in FIG. 9, three finite distances (1 m, 5 m, 10 m) followed by the autofocus lens are obtained. ) Can be determined without shaking the video camera to the subject at each distance. Further, since the best focus position for each distance is inspected by moving the chart 2 back and forth, there is no need to manually turn the distance ring of the video camera.
[0064]
In addition, space saving can be achieved as compared with the conventional determination method shown in FIG. For example, in the past, an actual distance of a subject distance of 10 m was required, but in the present embodiment, a lens with f = 1000 mm is used as the magnifying lens, so that a total distance of 1.5 m is sufficient, and a great saving is achieved. Space can be achieved.
[0065]
【The invention's effect】
As described above, according to the present invention, each distance of a subject can be created in a pseudo manner in the inspection apparatus unit, and the best focus position for each distance can be inspected by moving the position of the pseudo subject. Therefore, it is possible to automatically determine whether the autofocus lens has followed the focus at a limited distance at a finite distance without shaking the video camera to the subject at each distance and manually turning the distance ring of the video camera. Can do. Further, it is not necessary to artificially measure the defocus amount of the chart displayed on the television monitor in the conventional work for the defocus amount of the video camera.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an embodiment of the present invention.
FIG. 2 is a diagram showing the movement of the chart at each distance in the embodiment of the present invention.
FIG. 3 is an enlarged view of a portion A in FIG. 2 and a diagram (b) showing a defocus amount on the video camera side corresponding to the movement of the chart.
FIG. 4 is a diagram showing an example of a chart used in the embodiment of the present invention.
FIG. 5 is a perspective view showing an internal structure of the inspection apparatus unit according to the embodiment of FIG. 1;
FIG. 6 is a flowchart showing the operation of the embodiment of the present invention.
FIG. 7 is a flowchart showing the same operation.
FIG. 8 is a diagram showing an optical principle of an embodiment of the present invention.
FIG. 9 is an operation explanatory diagram of the embodiment of the present invention.
FIG. 10 is an overall configuration diagram of a conventional inspection apparatus.
FIG. 11 is a diagram illustrating a problem of a conventional focus determination method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Dark box 2 Chart 3 Ring illuminator 4 Magnifying lens 5 Distance ring 6 Camera lens control part 7 Camera microcomputer control part 8 Camera DSP part 9 CCD encoder part 10 Camera lens part 11 Personal computer control part 12 Stage 13 Illumination cover 14 Video camera part 15 Inspection unit 16 Optical axis

Claims (6)

In the production process of video cameras with autofocus function,
A focus determination device used to perform a focus determination test during autofocus tracking,
An inspection device unit pseudo object and the light source for illumination has been built, before Symbol comprises means for moving control the position of the pseudo object, the respective distances of the object to be used for focus determination of a video camera under test to the test device portion In addition to making it pseudo, the pseudo subject is moved by a minute amount in the front-rear direction at the position of each distance, and the focus position for each distance is inspected from the signal from the control unit of the video camera for measurement. A focus determination device for a video camera with an autofocus function, characterized by being configured .   2. The focus determination apparatus for a video camera with an autofocus function according to claim 1, wherein the entire inspection apparatus section is covered with a black box with a matte black surface.   3. The focus determination device for a video camera with an autofocus function according to claim 1, wherein the light source is a ring illuminator.  4. The focus determination device for a video camera with an autofocus function according to claim 1, wherein the pseudo subject is a Siemens chart or an Inmega chart. A method for determining the focus of a video camera with an autofocus function using the focus determination device according to claim 1,
When the pseudo subject is moved by a minute amount in the front-rear direction at the position of each distance, the best focus position in the front-rear direction operation range is obtained from the signal from the control unit of the video camera for measurement. A method for determining a focus of a video camera with an autofocus function, wherein the determination is performed. 6. The video with an autofocus function according to claim 5, wherein a moving speed when the pseudo subject is moved by a minute amount in the front-rear direction at each distance position is faster than an autofocus following speed of the video camera. Camera focus determination method.

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