JP5597783B1 - Imaging device - Google Patents

Abstract

An image pickup apparatus capable of shooting a moving body with sufficiently high resolution without a low-sensitivity image sensor, a dark lens, a low light amount electronic flash or an electronic flash is provided.
An image sensor 112 on an actuator 109 is driven by a piezoelectric element 113 in the direction opposite to the moving direction of the article 104 in order to follow the moving speed of the article 104 on the belt conveyor 102. By physically removing the blurring of the image of the article 104 imaged on the image sensor 112, it is possible to use a low-sensitivity image sensor 112 or an imaging component such as the optical system 110 having a large F value to achieve high resolution. A still image can be obtained.
[Selection] Figure 1

Description

  The present invention relates to an imaging apparatus. More specifically, the present invention relates to an imaging device that captures a still image of an object that is moved by moving means such as a belt conveyor.

  Due to the high performance of image pickup devices and the advancement of image processing technology, industrial use image pickup devices having an image recognition function have become widespread. The imaging device photographs an article that is moved by a belt conveyor, a robot arm, or the like. The information processing apparatus connected to the imaging apparatus processes the still image data output from the imaging apparatus, thereby determining the quality of the article. Then, the article processing facility performs a predetermined process according to the determination result. By doing so, the imaging apparatus has effects such as improving the yield of production facilities.

JP 2012-161029 A

  When processing for temporarily stopping the belt conveyor for photographing is added, the yield is greatly affected. Therefore, an industrial imaging apparatus basically photographs an article moving on the belt conveyor without stopping the belt conveyor. Naturally, when the transfer speed of the belt conveyor is high, the photographed image is blurred. For this reason, the conventional imaging device uses a high-sensitivity imaging device, a small (bright) lens with a small F value, and a high-intensity electronic flash (strobe). Therefore, an imaging device for industrial use is expensive.

  As a technique for reducing the blurring of a still image, for example, a camera shake correction technique using image processing software as disclosed in Patent Document 1 is well known. However, since the processing of a program that implements this image correction technique is complicated, implementation is not easy.

  The present invention has been made in view of such a situation, and uses simple software and hardware to move at a sufficiently high resolution even without a low-sensitivity image sensor, a dark lens, a low-light electronic flash, or an electronic flash. An object of the present invention is to provide an imaging device capable of photographing a body.

In order to solve the above-described problem, an imaging device according to the present invention includes an imaging element that captures an article moving in a predetermined direction, an actuator provided with the imaging element, and a signal that generates image information from a signal output from the imaging element. A processing apparatus and an optical system that forms an image of an article on the imaging element interposed between the imaging element and the article. Furthermore, the actuator is provided with a piezoelectric element that drives the imaging element in the direction opposite to the moving direction of the article, and is connected to the signal processing apparatus and the piezoelectric element, and is connected to the imaging element based on image information obtained from the signal processing apparatus. By calculating the moving speed of the image of the article to be imaged, the actuator is driven and controlled by controlling the voltage applied to the piezoelectric element by PWM control so that the imaging element follows the movement of the image of the article. An actuator control device.

According to the present invention, it is possible to provide an image pickup apparatus capable of shooting a moving body with sufficiently high resolution without using a low-sensitivity image pickup element, a dark lens, a low light quantity electronic flash, or an electronic flash.
Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is the schematic of an industrial line containing the imaging device which concerns on this embodiment. It is a disassembled perspective view of a camera module. It is a front view of an actuator. It is a block diagram which shows the hardware constitutions of an actuator control apparatus, and a block diagram which shows the function of a signal processing apparatus and an actuator control apparatus. It is a block diagram of a drive control part. It is a time chart which shows an example of a PWM control pulse, a time chart which shows an example of a reset pulse, and a wave form diagram which shows an example of a drive voltage of a piezoelectric element.

FIG. 1 is a schematic diagram of an industrial line 101 including an imaging apparatus according to the present embodiment.
The belt conveyor 102 is driven by a motor 103 at a constant speed. A predetermined article 104 is placed on the belt conveyor 102. This article 104 is in the middle of manufacturing or in the middle of inspection after manufacturing.
In the vicinity of the belt conveyor 102, an imaging device 105 for photographing the article 104 is installed. The imaging device 105 includes a camera module 106, a signal processing device 107, and an actuator control device 108.

  The camera module 106 is provided and fixed on a base (not shown) fixed in the vicinity of the belt conveyor 102. The camera module 106 includes an actuator 109, an optical system 110 including a plurality of lenses, and a sensor substrate 111 fixed to the actuator 109. An image sensor 112 is provided on the sensor substrate 111. The optical system 110 causes the image sensor 112 to form an image of the article 104 on the belt conveyor 102. At this time, as is well known, the image is inverted vertically and horizontally. The actuator 109 is provided with a piezoelectric element 113, and the actuator 109 drives the imaging element 112 on the sensor substrate 111 by applying a predetermined voltage to the piezoelectric element 113. The driving direction is the moving direction of the image formed on the image sensor 112, which is the reverse of the moving direction (arrow V114) of the article 104 on the belt conveyor 102 (arrow V115).

  A signal processing device 107 is connected to the image sensor 112. The signal processing device 107 receives the output signal of the image sensor 112 and generates still image data. Still image data generated by the signal processing device 107 is output to a predetermined still image information processing device 116 such as an image recognition device. Still image data is also supplied to the actuator controller 108.

  The actuator control device 108 receives an external trigger signal generated from the control device or the like of the belt conveyor 102 from the external trigger input terminal 118, applies a voltage to the piezoelectric element 113, and passes on the actuator 109 through the piezoelectric element 113. It is a device that drives and controls the image sensor 112 at a predetermined speed. In other words, the image of the article 104 projected on the image sensor 112 is fixed by moving the image sensor 112 minutely according to the moving speed of the article 104 moving on the belt conveyor 102, thereby preventing blurring. If necessary, the strobe is illuminated by an external trigger signal obtained from the external trigger input terminal 118. In this embodiment, light emission control is performed on an LED strobe 117 using a white LED as an example. The strobe is not necessarily required depending on the moving speed of the belt conveyor 102 and the brightness of the environment where the image sensor 112 is installed. The external trigger signal is substantially the same as the still image shooting timing signal, and is also supplied to the still image information processing apparatus 116.

  In order to drive the piezoelectric element 113, it is necessary to apply a high voltage. On the other hand, the piezoelectric element 113 is displaced in proportion to the voltage, and a large force is generated in the piezoelectric element 113 with this displacement. For this reason, the piezoelectric element 113 is an optimal driving unit for moving the image sensor 112 quickly and minutely.

FIG. 2 is an exploded perspective view of the camera module 106.
FIG. 3 is a front view of the actuator 109.
The optical system 110 is fixed to the fixed portion 109 a at the periphery of the actuator 109 through the front panel 201. The sensor substrate 111 is fixed to the movable part 109 b at the center of the actuator 109. A piezoelectric element 113 is inserted between the movable portion 109b and the fixed portion 109a. When a voltage is applied to the piezoelectric element 113, the piezoelectric element 113 expands. Then, the movable portion 109b moves by the force of the piezoelectric element 113.

FIG. 4A is a block diagram illustrating a hardware configuration of the actuator control device 108.
FIG. 4B is a block diagram illustrating functions of the signal processing device 107 and the actuator control device 108.
As shown in FIG. 4A, the actuator control device 108 includes a known microcomputer. A CPU 301, ROM 302, and RAM 303 are connected to the bus 304. The bus 304 further includes an image interface 305 (denoted as “image I / F” in FIG. 4A), a first interface 306 (denoted as “first I / F” in FIG. 4A), and a second interface 307 (illustrated in FIG. 4A). 4A, indicated as “second I / F”).
The image interface 305 receives still image data from the signal processing device 107.
The first interface 306 is a serial interface to which an external trigger signal is input.
The second interface 307 is a serial interface that controls the switch circuit 308. The switch circuit 308 is a circuit including a MOSFET described later, and outputs an arbitrary voltage to the piezoelectric element 113 by PWM control based on the high voltage output from the switching power supply 309.

With reference to the block diagram of FIG. 4B, functions of the signal processing device 107 and the actuator control device 108 will be described.
The signal processing device 107 includes a driver 311 and an A / D converter 312 (denoted as “A / D” in FIG. 4B).
The driver 311 amplifies the signal from the image sensor 112. The A / D converter 312 converts the analog signal of the image sensor 112 into digital data.
The signal processing device 107 receives the output signal of the image sensor 112 and generates still image data. Still image data generated by the signal processing device 107 is output to a predetermined still image information processing device 116 such as an image recognition device.

The actuator control apparatus 108 having a known microcomputer includes an article speed calculation unit 313, a drive control unit 314, a switching power supply 309, and a smoothing capacitor C315.
The article speed calculation unit 313 calculates the speed of the image of the article 104 on the belt conveyor 102 reflected on the image sensor 112 based on the still image data continuously output from the signal processing device 107, and outputs the speed information of the image. To do.
The drive control unit 314 controls the high voltage generated by the switching power supply 309 by PWM control based on the external trigger signal and the image speed information of the article 104, and outputs a voltage for driving the piezoelectric element 113. The voltage output from the drive control unit 314 is smoothed by the smoothing capacitor C315 and applied to the piezoelectric element 113.

  Note that the article speed calculation unit 313 calculates the moving speed of the image of the article 104 shown on the image sensor 112, not the moving speed of the article 104. For example, an image of the article 104 shown in a plurality of consecutive frames is acquired from the image sensor 112, and the moving speed of the image is calculated from the image shift amount and the interframe time in the pixel unit of the image sensor 112. The actuator control device 108 drives the piezoelectric element 113 so that the image sensor 112 follows the moving speed of the image.

  The imaging apparatus 105 of the present embodiment assumes that the article 104 is driven at a constant speed. For this reason, the actuator control device 108 drives the piezoelectric element 113 at a constant speed in accordance with the movement of the image.

FIG. 5 is a block diagram of the drive control unit 314.
The PWM control unit 501 receives the trigger pulse and the speed information of the article 104 and outputs a PWM control pulse and a reset pulse.
The PWM control pulse is applied to the gate of a P-channel MOSFET 502 (hereinafter abbreviated as “PMOSFET”). The PMOSFET 502 whose source is connected to the switching power supply 309 functions as a high-side switch for the switching power supply 309.
The reset pulse is applied to the gate of an N-channel MOSFET 503 (hereinafter abbreviated as “NMOSFET”). The drain of the NMOSFET 503 is connected to the current limiting resistor R504. The other terminal of the current limiting resistor R504 is connected to the drain of the PMOSFET 502. The NMOSFET 503 functions as a low-side switch for the smoothing capacitor C315 and the piezoelectric element 113.
The NMOSFET 503 and the PMOSFET 502 in the drive control unit 314 are general usage examples, but are not necessarily limited thereto. For example, on / off of the switching power supply 309 may be controlled by applying a gate voltage higher than the voltage output from the switching power supply 309 to the NMOSFET.

In the block diagram showing the hardware configuration of the actuator control device 108 shown in FIG. 4A, the CPU 301, the ROM 302, the RAM 303, the bus 304, the image interface 305, the first interface 306, and the first interface 306 are excluded, except for the switch circuit 308 and the switching power supply 309. The second interface 307 constitutes the article speed calculation unit 313 in FIG. 4B and the PWM control unit 501 in FIG. That is, the article speed calculation unit 313 and the PWM control unit 501 are functions realized by a program executed by a microcomputer.
The switch circuit 308 in FIG. 4A corresponds to the PMOSFET 502, the NMOSFET 503, and the current limiting resistor R504 in FIG.

FIG. 6A is a time chart illustrating an example of a PWM control pulse.
FIG. 6B is a time chart illustrating an example of a reset pulse.
FIG. 6C is a waveform diagram illustrating an example of the drive voltage of the piezoelectric element 113.
As shown in FIG. 6A, the PWM control unit 501 first outputs a PWM control pulse with a reduced duty ratio from time t0, and gradually increases the duty ratio. Then, as shown in FIG. 6C, the voltage smoothed by the smoothing capacitor C315 has a triangular waveform in which the voltage rises linearly.
At time t1, the output of the PWM control pulse is stopped as shown in FIG. 6A, and the reset pulse is output as shown in FIG. 6B. Then, the electric charge accumulated in the smoothing capacitor C315 and the piezoelectric element 113 is discharged to the ground node through the current limiting resistor R504 and the NMOSFET 503.

  The PWM control unit 501 controls the time from the time point t0 to the time point t1 based on the speed information of the article 104, thereby causing the image sensor 112 to follow the image of the article 104. The exposure time required for the image sensor 112 to photograph the article 104 is, for example, 1/60 second that is a standard shutter time of a general electronic still camera. For this reason, the moving distance necessary for causing the image sensor 112 to follow the image of the article 104 may be a minimum distance of, for example, about several to several hundreds of micrometers.

As an example, a voltage of about 140 V at maximum is applied to the piezoelectric element 113 to drive the image sensor 112 to about 150 μm at maximum. By driving the image sensor 112 in synchronization with the moving speed of the article 104 on the belt conveyor 102, the exposure time (or exposure time) of the image sensor 112 can be increased.
For example, the ISO sensitivity of the image capturing apparatus 105 can be set to about 100 or 200 if the image can be taken without blurring at 1/60 second or 1/30 second that is a standard shutter time of a general electronic still camera. . That is, a low-cost image pickup device or optical system for consumer use can be adopted. If the captured still image is sufficiently bright, an illuminance sufficient for photographing can be secured by providing a fluorescent lamp or the like in the vicinity of the article 104 moving on the belt conveyor 102 without using the LED strobe 117. Further, when an optical system or an image sensor having the same performance as that of a conventional apparatus is used, the amount of light obtained at the time of photographing increases, so that the aperture of the optical system can be reduced more than before. That is, since the depth of field of the imaging device 105 increases, the still image becomes clearer.

  The time for which the electric charges accumulated in the smoothing capacitor C315 and the piezoelectric element 113 are completely discharged is determined by the time constant formed by the combined capacitance of the smoothing capacitor C315 and the piezoelectric element 113 and the current limiting resistor R504. The smoothing capacitor C315 needs to withstand a high voltage, but satisfies a sufficient smoothing performance with a small capacitance of about 0.027 μF. The capacitance of the piezoelectric element 113 is an extremely small capacitance of about several PF. Therefore, even if the resistance value of the current limiting resistor R504 is a carbon resistance of about 1 MΩ, it is sufficient because the flowing current is small.

  Unlike the electronic camera shake correction technology adopted in the consumer digital still camera, the image pickup apparatus 105 of the present embodiment mechanically drives the image pickup element 112 so that the subject (the article 104) and the image pickup element 112 are driven. This reduces blurring caused by a shift in the relative positional relationship between and. The mechanism of the imaging apparatus 105 utilizes the fact that the moving direction of the article 104 to be photographed is always constant. The imaging apparatus 105 obtains the moving speed of the article 104 from the imaging element 112 or the outside, calculates the moving speed of the image, and drives the imaging element 112 so as to follow the moving speed of the image. For this reason, the imaging device 105 can follow even if the speed of the belt conveyor 102 fluctuates. Therefore, unlike the electronic camera shake correction technology, the mounting is extremely easy. The microcomputer software may be executed by installing a program for detecting the moving speed of the article 104, detecting the presence of the article 104, and PWM drive control in an inexpensive one-chip microcomputer.

This embodiment can be applied as follows.
(1) In order to precisely detect the moving speed of the article 104, for example, a speed sensor made of a photo interrupter is provided on the belt conveyor 102 side, and the moving speed information of the article 104 is transferred to the moving speed information input terminal 401 in FIG. 4B. You may give to. In this case, since the photo interrupter directly detects the moving speed of the article 104, the article speed calculating unit 313 needs to convert this into an image moving speed (equal to the moving speed of the image sensor 112). Alternatively, the belt transfer speed on the belt conveyor 102, that is, the movement speed of the article 104, may be calculated from the rotation speed of the motor 103 that drives the belt conveyor 102 and applied to the movement speed information input terminal 401. As a means for detecting the rotation speed of the motor 103, various known techniques such as a tachometer generator can be used in addition to using a sensor built in the brushless motor. In this case, it is necessary to convert the rotational speed of the motor 103 into the moving speed of the belt conveyor 102 and further convert into the moving speed of the image, or directly convert the rotational speed of the motor 103 into the moving speed of the image.

  (2) The configuration of the drive control unit 314 in the actuator control device 108 is not necessarily limited to the PWM control by the PWM control unit 501. Control by ΔΣ (delta sigma) modulation that outputs a waveform similar to PWM may be performed. Further, a plurality of voltage sources that output different voltages may be arranged in parallel and switched by a switch.

  (3) In FIG. 1, the belt conveyor 102 is illustrated as a means for transferring the article 104, but the means for transferring the article 104 is not limited to the belt conveyor. For example, a robot arm is also a target. In the case of a robot arm that reciprocates or pauses, there are an acceleration area, a constant speed area, and a deceleration area in the movable area of the arm. Therefore, it is preferable that the imaging device 105 captures images within the constant speed area.

  (4) The scene to which the imaging apparatus 105 of this embodiment is applied is not limited to the industrial line 101 alone. It can also be applied to a car number automatic reading device that is installed on the road and automatically reads the car number plate. A high-sensitivity infrared camera and a powerful infrared strobe are used for the automobile number automatic reading device. By driving the imaging device 105 following the speed of the automobile, a clear license plate image with little blur can be obtained even if a low-sensitivity infrared camera or a weak infrared strobe is adopted. Lowering the price of an automobile number automatic reading device will greatly contribute to the safety of society.

In the present embodiment, the imaging device 105 is disclosed.
The imaging element 112 on the actuator 109 is driven by the piezoelectric element 113 in the direction opposite to the moving direction of the article 104 on the belt conveyor 102. By physically removing the blurring of the image of the article 104 imaged on the image sensor 112, using a low-cost image sensor such as the low-sensitivity image sensor 112 or the optical system 110 having a large F value, A high-resolution still image can be obtained.

  The embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and other modifications, Includes application examples.

  DESCRIPTION OF SYMBOLS 101 ... Industrial line, 102 ... Belt conveyor, 103 ... Motor, 104 ... Article, 105 ... Imaging device, 106 ... Camera module, 107 ... Signal processing device, 108 ... Actuator control device, 109 ... Actuator, 109a ... Fixed part, 109b DESCRIPTION OF SYMBOLS ... Movable part, 110 ... Optical system, 111 ... Sensor substrate, 112 ... Imaging element, 113 ... Piezoelectric element, 116 ... Still image information processing apparatus, 117 ... LED strobe, 201 ... Front panel, 301 ... CPU, 302 ... ROM, 303 ... RAM, 304 ... bus, 305 ... image interface, 306 ... first interface, 307 ... second interface, 308 ... switch circuit, 309 ... switching power supply, 311 ... driver, 312 ... A / D converter, 313 ... frame Memory, 313 ... Article speed Out portion, 314 ... drive controller, C315 ... smoothing capacitor, 401 ... traveling speed information input terminal, 501 ... PWM control unit, 502 ... PMOSFET, 503 ... NMOSFET, R504 ... current limiting resistor

Claims (1)

An image sensor for photographing an article moving in a predetermined direction;
An actuator provided with the image sensor;
A signal processing device that generates image information from a signal output by the imaging device;
An optical system that forms an image of the article on the imaging element interposed between the imaging element and the article;
A piezoelectric element that is provided in the actuator and drives the imaging element in a direction opposite to the moving direction of the article;
The imaging device is connected to the signal processing device and the piezoelectric element, and calculates the moving speed of the image of the article formed on the imaging device based on image information obtained from the signal processing device. An imaging apparatus comprising: an actuator control device that drives and controls the actuator by controlling a voltage applied to the piezoelectric element by PWM control so as to follow the movement of the image of the article .

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