JP2019028192A - Imaging device - Google Patents

Abstract

To provide an imaging device that makes it possible to correct offset errors occurring in gyro outputs even when photographers are operating cameras.SOLUTION: An imaging device has: angular velocity detection means that detects an angular velocity; correction means that corrects an offset component of angular velocity data acquired by the angular velocity detection means; frequency detection means that detects a frequency of the angular velocity data; and amplitude detection means that detects amplitude of the angular velocity data. When a frequency detected by the frequency detection means from the angular velocity data acquired after detecting prescribed actions falls within 5 to 15 Hz of a range, and the amplitude detected by the amplitude detection means is smaller than a prescribed range, the offset component of the angular velocity data is corrected by the correction means.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging apparatus, and more particularly to an imaging apparatus having an angular velocity detection function.

  2. Description of the Related Art Conventionally, a photographing method called panning is known as one of methods for photographing a moving subject. When the panning is performed, the moving subject is not shaken, but only the background is drawn (flowing), so that the movement and speed of the subject can be expressed.

  In panning, it is necessary to control the pan of the camera so as to follow the moving speed of the subject. The amount of background flow is determined by the camera pan control speed, focal length, and shutter speed.Since the pan speed and focal length are determined by the shooting environment of the subject, the photographer adjusts the shutter speed to adjust the background speed. The flow rate can be adjusted.

  The adjustment of the shutter speed largely depends on the skill of the photographer. However, Patent Document 1 automatically selects the optimum shutter speed based on the angular speed calculated from the angular speed detection means installed in the camera and the focal length information of the lens. Techniques to do this are disclosed.

  In general, the output of a gyro sensor may not be zero even when it is stationary, and an error from the output zero is called an offset error. If there is an offset error, the pan speed cannot be calculated accurately. For this reason, in order to correct the offset error, it is known to measure the offset error at the time of manufacture and store it in the device as a correction value in advance.

  Patent Document 2 proposes a method of determining a camera stationary state and calculating a correction value based on sensor output and temperature data at that time.

Japanese Patent Laying-Open No. 2015-102774 Japanese Patent Laying-Open No. 2015-179887

  However, in the conventional technique disclosed in Patent Document 2 described above, no reference is made to a method for determining a stationary state. When comparing a state in which a camera with an offset error is stationary and a state in which a camera without an offset error is operating at a constant angular velocity, the sensor output may be the same. The correction value is calculated when the main power is turned off, after a predetermined time has passed since the main power was turned off, or at a predetermined time, and a situation occurs in which an offset error occurs when the photographer operates the camera. Is not mentioned.

  Accordingly, an object of the present invention is to provide an imaging apparatus that can correct an offset error generated in a gyro output even when a photographer is operating a camera.

In order to achieve the above object, an imaging apparatus according to the present invention includes:
Angular velocity detecting means for detecting angular velocity;
Correction means for correcting the offset component of the angular velocity data acquired by the angular velocity detection means;
Frequency detection means for detecting the frequency of the angular velocity data;
Amplitude detecting means for detecting the amplitude of the angular velocity data;
Have
From the angular velocity data acquired after detecting a predetermined operation, when the frequency detected by the frequency detection means is in the range of 5 to 15 Hz, and the amplitude detected by the amplitude detection means is smaller than the predetermined range, The offset component of the angular velocity data is corrected by the correcting means.

  According to the imaging apparatus according to the present invention, the offset error of the angular velocity sensor can be corrected without impairing convenience.

It is the figure which showed an example of the operation | movement flow in a present Example. It is the figure which showed an example of the block diagram of the imaging device in a present Example. It is a figure for demonstrating the relationship between the imaging device and an angular velocity sensor detection axis in a present Example. It is a figure for demonstrating an example of the angular velocity sensor output and offset error in a present Example. It is a figure for demonstrating an example of the minute vibration of the muscle which arises in the angular velocity sensor output in a present Example.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 2 is a diagram showing the configuration of the electronic camera according to the embodiment of the present invention.

  The light from the subject incident through the optical lens 201 of the imaging device 200 is imaged on the imaging sensor 202 including a CMOS sensor or a CCD sensor. The subject image formed on the image sensor 202 is encoded into a digital signal by the AD conversion circuit 203 and then subjected to image processing such as noise reduction processing and white balance processing by the image processing circuit 204.

  Further, the image processing circuit 204 performs conversion into a digital image file such as a JPEG (Joint Photographic Experts Group) image format for recording in the recording memory 207. The image processing circuit 204 also generates VRAM image data to be displayed on the display circuit 213.

  A memory control circuit 205 is a circuit that controls transmission / reception of image data generated by the AD conversion circuit 203, the image processing circuit 204, and the like.

  The volatile memory 206 is a memory capable of high-speed reading and writing such as DDRSDAM, and is used as a workspace for image processing performed by the image processing circuit 204. Further, it is also used as a work space for temporarily storing output data of an angular velocity sensor 214 described later.

  The recording memory 207 is a recording device that can be attached to and detached from the imaging device 200 via a connection unit (not shown), and is a readable / writable recording medium such as an SD card or a CF card.

  The system control circuit 208 is a circuit that controls the imaging apparatus 200, and is, for example, a microcomputer with a built-in CPU or the like. The system control circuit 208 performs control according to a program stored in advance in the nonvolatile memory 209. The system control circuit 208 performs photometry control using the image data processed by the image processing circuit 204.

  The non-volatile memory 209 is a readable / writable memory such as a NOR flash ROM or an EEPROM, for example, in addition to the control program of the system control circuit 208, the characteristic data of the display circuit 213 and the image processing circuit 204 Also stored are image processing parameters for processing.

  The operation switch 210 is a switch for accepting a photographer's operation input, and includes a push switch, a slide switch, a dial switch, a capacitance switch, and the like. By operating the operation switch 210, it is possible to cause the imaging apparatus 200 to perform various operations. For example, when a shooting preparation switch is operated, the system control circuit 208 controls the distance measuring circuit (not shown) to control the imaging apparatus 200 to a state in which shooting is possible.

  The acceleration sensor 211 is a sensor capable of three-axis detection, which is configured by, for example, an IC having a MEMS structure. By calculating using the detection values of the respective axes, the tilt in the roll direction and the pitch direction of the imaging device 200 are calculated. It is possible to calculate the inclination in the yaw direction.

  The proximity sensor 212 is a sensor composed of a combination of, for example, an infrared LED and an infrared sensor, and is arranged near a finder unit (not shown) so as to detect whether the photographer is approaching the face. When the approach of the face is detected, the system control circuit 208 can prepare for photographing before the photographer's instruction is given, for example, by starting display control of an in-viewfinder display (not shown). Further, by turning off the display of the display circuit 213, it is possible to prevent the photographer from feeling dazzling and to save energy.

  The display circuit 213 is a display arranged on the back surface of the electronic camera 200, and is configured by an LCD (Liquid Crystal Display) or the like.

  The angular velocity sensor 214 is a gyro sensor capable of three-axis detection, which is constituted by, for example, an MEMS structure IC or the like. It is possible to calculate the roll turning speed, the pitch turning speed, and the yaw turning speed of the imaging apparatus 200 by calculating using the detection values of the respective axes.

  The relationship between the imaging device 200 and the angle detection axis will be described with reference to FIG.

  An axis parallel to the lens optical axis (not shown) is a roll axis, an axis parallel to the horizontal direction of the imaging apparatus 200 and perpendicular to the roll axis is a pitch axis, and an axis perpendicular to the roll axis and the pitch axis is a yaw axis. .

  In this embodiment, it is assumed that the resolution of the angular velocity sensor 214 is 256 / (deg / sec). For example, when the yaw axis sensor output is +256 LSB, the camera is turning at 1 deg / sec in the yaw direction.

  FIG. 4 is a schematic example showing the output of the yaw axis of the angular velocity sensor 214 in time series when the imaging device 200 is rotated in a predetermined manner. A solid line is a waveform example when there is no offset error in the output, and a broken line is a waveform example when the offset error is 768LSB in the output. The horizontal axis is time, and one of the vertical axes is a yaw axis output value of the angular velocity sensor 214, and the other is an axis obtained by converting the yaw axis output value into an angular velocity.

  The yaw axis output indicated by the solid line in FIG. 4 will be described. In order to simplify the explanation, it is assumed that the other roll axis outputs and pitch axis outputs are 0 LSB, that is, they are not turning.

  In the period T1, since the yaw axis output is 0LSB, it can be determined that the camera is stationary. In the period T2, since the yaw axis output increases, it can be determined that the camera has started turning in the yaw direction. In the period T3, since the yaw axis output is constant at 1280 LSB, it can be determined that the vehicle is turning at a constant angular velocity of 5 deg / s. In the period T4, since the yaw axis output decreases, it can be determined that the turning speed is slow. In the period T5, since the yaw axis output is 0LSB, it can be determined that the camera is stationary. In this way, it is possible to determine whether the camera is stationary or turning based on the output of the angular velocity sensor 214.

  On the other hand, in the graph shown by the broken line, since the yaw axis output indicates 768LSB in the period T1 and the period T5 when the camera is stationary due to the influence of the offset error, the imaging apparatus 200 turns at an angular velocity of 3 deg / s. The graph will be the same as if Also during the periods T2, T3, and T4, the output is the same as that of turning at an angular velocity faster than actual due to the influence of the offset error.

  FIG. 5 is an example of an actual waveform of the yaw axis output of the angular velocity sensor 214. In each figure, the horizontal axis represents time, and the vertical axis represents sensor output converted to angular velocity.

  FIG. 5A shows a state where the imaging apparatus 200 is fixed to a stable place such as a tripod, that is, a stationary state. In this example, it can be seen that the yaw axis output at rest has an offset error of about 3 [deg / s]. It can also be seen that the fluctuation component is small although there is an offset error.

  FIG. 5B shows a state where the photographer holds the imaging apparatus 200 and is ready for photographing. Similar to the stationary state of FIG. 5A, an offset error of about 3 [deg / s] can be confirmed, and a periodic vibration is observed. This is due to the minute vibration of the muscle of the photographer holding the hand, and generally has a frequency of about 5 to 15 [Hz].

  FIG. 5C shows an example of a state in which a pan operation is performed while the photographer is holding the imaging device 200. Compared to the case of FIG. 5B, the fluctuation of the waveform becomes larger due to the influence of the pan operation, and it becomes impossible to detect the minute vibration of the muscle.

  As described above, in general, in a state where the photographer holds the camera, in order to stabilize the camera as much as possible, it is easy to detect a minute vibration of the muscle. On the other hand, in panning and the like, the camera tends to become unstable, and it is difficult to detect minute vibrations of muscles.

  Therefore, the stationary state of the imaging apparatus 200 can be estimated depending on whether or not minute muscle vibration can be detected in the output of the angular velocity sensor 214.

  Hereinafter, a preferred embodiment of the present invention will be described with reference to FIG.

  FIG. 1 is a flowchart for explaining a case where a photographer holds a camera and performs a shooting preparation operation as an example of the present embodiment.

  The system control circuit 208 detects whether the SW1 button included in the operation switch 210 for starting a shooting preparation operation such as distance measurement or photometry is operated (S101). If it is detected that the SW1 button is turned on, the flow proceeds to S102. If it is not detected that the SW1 button is turned on, the flow of S101 is repeatedly executed.

  In S102, the system control circuit 208 communicates with the angular velocity sensor 214 to acquire angular velocity data.

  Next, the system control circuit 208 records the acquired angular velocity data in the volatile memory 206 (S103).

  Next, the system control circuit 208 determines whether a predetermined time has elapsed since the SW1 operation (S104). If the predetermined time has not elapsed, the flow returns to S102. In this way, the system control circuit 200 can acquire time-series data by recording the angular velocity data in the volatile memory 206 for a predetermined time. When a predetermined time elapses in S104, the process proceeds to S105.

  In S <b> 105, the system control circuit 208 calculates the frequency F of the angular velocity data recorded in the volatile memory 206. As a method for calculating the frequency F from the angular velocity data, for example, it is possible to detect a local peak of the angular velocity data, measure the time T between the peaks, and calculate the frequency F from the reciprocal thereof.

  Next, the system control circuit 208 confirms whether the frequency F is in the range of 5 to 15 Hz (S106).

  When the frequency F is not within the range of 5 to 15 Hz, the system control circuit 208 determines that the imaging apparatus 200 is in an unstable state, and does not calculate and correct the correction value of the angular velocity sensor 214. (S112).

  On the other hand, when the frequency F is in the range of 5 to 15 Hz, the process proceeds to the flow S107. The system control circuit 208 calculates the amplitude A from the recorded angular velocity data. As a method for calculating the amplitude A from the angular velocity data, for example, it is possible to detect a local negative peak adjacent to a local positive peak of the angular velocity data and calculate the amplitude A from the peak level difference.

  Next, the system control circuit 208 determines whether the amplitude A is within a predetermined range (S108). The predetermined range is, for example, a range of angular velocity assumed to be generated in the angular velocity sensor 214 when the photographer holds the imaging device 200, and is information recorded in the nonvolatile memory 209 in advance. Further, for example, a function of acquiring the amplitude from the acceleration data of the angular velocity sensor 214 when the photographer holds the imaging device 200 may be provided and arbitrarily recorded in the nonvolatile memory 209.

  When the system control circuit determines that the amplitude A is outside the predetermined range, the system control circuit proceeds to the flow of S112.

On the other hand, when it is determined that the amplitude A is within the predetermined range, the system control circuit 208 determines that the imaging apparatus 200 is stable (S109), and proceeds to the next flow. In S110, the system control circuit 208 calculates a correction value for correcting the offset error of the angular velocity sensor. As a method for calculating the correction value, for example, the correction value can be obtained from an average value Ω _AVE of angular velocity data recorded in the volatile memory 206 for a predetermined period. The system control circuit 208 corrects the output data of the angular velocity sensor 214 using the correction value calculated in S110 (S111).

  As described above, according to the offset error correction method of the angular velocity sensor output of the present invention, it is determined whether the vibration component generated in the angular velocity sensor is a minute vibration of the photographer's muscle, so that the imaging device 200 is in a stationary state. Can be determined.

  Further, in order to increase the accuracy of detecting minute vibrations of the photographer's muscle, the detection sensitivity of the angular velocity sensor 214 may be increased when the angular velocity sensor output is acquired in S102.

  In the embodiment, the SW1 button for starting operations such as distance measurement and photometry has been described as an operation for instructing the shooting preparation operation. However, other operations may be used. For example, an eyepiece operation on the finder of the photographer by the proximity sensor 212 may be used. For example, any combination of the above operations may be used.

200 imaging device, 202 imaging sensor, 203 AD conversion circuit,
204 image processing circuit, 208 system control circuit, 210 operation switch,
211 acceleration sensor, 212 proximity sensor, 213 display circuit,
214 Angular velocity sensor

Claims (4)

Angular velocity detection means (214) for detecting angular velocity;
Correction means (208) for correcting an offset component of the angular velocity data acquired by the angular velocity detection means;
Frequency detection means (208) for detecting the frequency of the angular velocity data;
Amplitude detecting means (208) for detecting the amplitude of the angular velocity data;
Have
From the angular velocity data acquired after detecting a predetermined motion, the frequency detected by the frequency detecting means (208) is in the range of 5 to 15 Hz, and the amplitude detected by the amplitude detecting means (208) is a predetermined value. An imaging apparatus characterized in that the offset component of the angular velocity data is corrected by the correcting means (208) when it is within the range. The imaging apparatus according to claim 1, wherein the predetermined operation is any one or a combination of a photometry instruction operation, a distance measurement instruction operation, and an eyepiece operation to the viewfinder. The predetermined range of the amplitude is stored in advance in the storage means (209) the amplitude acquired from the angular velocity data detected by the angular velocity detection means (214) when the photographer performs the predetermined operation according to claim 2. The imaging apparatus according to claim 1, wherein the imaging apparatus is stored. The image pickup apparatus according to any one of claims 1 to 3, wherein the angular velocity data acquired after detecting a predetermined operation controls the detection sensitivity of the angular velocity detection unit to be higher than normal.