Imaging apparatus

Abstract

To solve the problem in which, when realizing an electronic ND function using intermittent charge accumulation, accumulation may not occur during the set exposure period.SOLUTION: An imaging apparatus includes an imaging element capable of intermittent charge accumulation control and a setting unit that sets the shutter speed and electronic ND effect amount. The setting unit is configured to set an intermittent charge accumulation pattern so that the time from the start to the end of charge accumulation during intermittent charge accumulation is within a predetermined range relative to the set exposure period.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an imaging device. [Background technology]

[0002] In recent years, imaging devices such as home video cameras and digital still cameras have become widespread. These imaging devices are equipped with an electronic shutter shooting function that is quieter than mechanical shutter shooting and enables high-speed continuous shooting.

[0003] The global shutter method in the electronic shutter shooting function makes it possible to start and end charge accumulation all at once within the screen, allowing shooting to be performed without the so-called rolling shutter distortion. Also, as described in Patent Document 1, by performing charge accumulation intermittently, it is possible to realize an electronic ND function that shoots by reducing the amount of incident light compared to normal for the set exposure period. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2015-109503 Summary of the Invention [Problem to be solved by the invention]

[0005] In the method described in Patent Document 1, when capturing an image with reduced incident light intensity by intermittently accumulating charge within a charge accumulation period set by the user, there is a possibility that the image will be captured with an exposure period different from the one intended by the user. In such a case, the captured image will have a different impression from the image that the user originally intended to capture. [Means for solving the problem]

[0006] The imaging device of the present invention is characterized by having an imaging means for converting an optical image into an electrical signal, a setting means for setting an exposure period of the imaging means, and a control means for determining an intermittent charge accumulation pattern so that the timing from the start of the first charge accumulation to the end of the last charge accumulation when intermittent charge accumulation is performed by the imaging means to obtain a light reduction effect falls within a predetermined range, relative to the start and end timings of the exposure period set by the setting means. [Effects of the Invention]

[0007] According to the present invention, it is possible to acquire a photographed image based on a desired light reduction effect within a set exposure period. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram of an imaging apparatus according to an embodiment. [Figure 2] FIG. 2 is a circuit diagram showing a part of an image sensor according to an embodiment. [Figure 3] 10A and 10B are diagrams showing patterns of intermittent charge accumulation in the embodiment. [Figure 4] 10A and 10B are diagrams showing the allowable error range of accumulation time in intermittent charge accumulation in an embodiment. [Figure 5] 10A and 10B are diagrams illustrating the synchronization of intermittent charge accumulation with an imaging period in an embodiment. [Figure 6] 10A and 10B are diagrams illustrating gain compensation for intermittent charge accumulation in accordance with an imaging cycle in an embodiment. [Figure 7] FIG. 10 is a diagram showing a setting screen for an electronic ND function in the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Fig. 1 is a block diagram showing a schematic configuration of an image capturing apparatus 100 according to an embodiment of the present invention.

[0010] 1, a photographic lens 10 forms an optical image on an image sensor 14. A mechanical shutter 12 has an aperture function and can adjust the amount of light of the optical image that reaches the image sensor 14. The image sensor 14 converts the optical image into an electrical signal, and an A / D converter 16 converts the analog signal output from the image sensor 14 into a digital signal. The A / D converter 16 may be built into the image sensor 14.

[0011] The timing generation circuit 18 is controlled by the control circuit 22 and the system control circuit 50, and supplies clock signals and control signals to the image sensor 14 and the A / D converter 16. In addition to the mechanical shutter 12, in video shooting, the charge accumulation time can also be controlled by an electronic shutter that controls the reset timing 18 of the image sensor 14.

[0012] The image processing circuit 20 performs predetermined pixel interpolation processing and color conversion processing on image data supplied from the A / D converter 16 or the control circuit 22. An electronic zoom function is also realized by image cropping and magnification processing by the image processing circuit 20. Furthermore, the image processing circuit 20 performs predetermined arithmetic processing on the captured image data, and the calculation results obtained are used to perform auto white balance (AWB) processing by the TTL method.

[0013] The image data output from the A / D converter 16 is written into the memory 30 via the image processing circuit 20 and the control circuit 22. The display image data written into the memory 30 is supplied to the image display unit 28, which is composed of a TFT LCD or the like, via the control circuit 22 and displayed. If the captured image data is displayed sequentially on the image display unit 28, an electronic viewfinder function can be realized. The display on the image display unit 28 can be turned on / off as desired by instructions from the system control circuit 50, and turning the display off can significantly reduce the power consumption of the imaging device 100.

[0014] The memory 30 can also be used as a work area for the system control circuit 50. Program code executed by the system control circuit 50 is written to a non-volatile memory 31 configured with a Flash ROM or the like, and the system control circuit 50 executes the program code by sequentially reading it out.

[0015] In addition, the nonvolatile memory 31 has an area for storing system information and an area for storing user setting information, and various information and settings can be read and restored the next time the device is started up. The system control circuit 50 controls the overall operation of the imaging device 100 by sequentially reading and executing program codes written in the nonvolatile memory 31.

[0016] The compression / decompression circuit 32 reads the image data stored in the memory 30 and performs compression or decompression processing using adaptive discrete cosine transform (ADCT) or the like, and writes the processed image data back into the memory 30 .

[0017] The system control circuit 50 controls the image processing circuit 20 to perform predetermined calculations on the captured image data acquired by the TTL method, and then controls the exposure control unit 40 and the distance measurement control unit 42 to perform automatic exposure adjustment (AE) processing and autofocus (AF) processing, respectively, using the obtained calculation results.

[0018] The exposure control unit 40 adjusts the amount of light (exposure) incident on the image sensor 14 by controlling the aperture function of the mechanical shutter 12 based on the calculation results of the image processing circuit 20. It also controls the flash dimming function in conjunction with the flash 48.

[0019] The distance measurement control unit 42 performs focus control using the photographic lens 10 based on image data acquired by the TTL method. If the amount of light is insufficient when performing focus control, the flash 48 is made to emit light as AF auxiliary light.

[0020] The zoom control unit 44 controls optical zooming by the photographic lens 10 .

[0021] The mode dial 60 can be operated by the user to switch the power of the imaging device 100 on and off, and to switch between various shooting modes (automatic shooting, panoramic shooting, video shooting, etc.), and various function modes (playback, PC connection, etc.).

[0022] When the release button 62 is pressed halfway by a user, the first switch SW1 is turned on, and when SW1 is turned on, the system control unit 50 starts image capture preparation operations such as AF processing, AE processing, and AWB processing. When the release button 62 is pressed all the way, the second switch SW2 is turned on, and a series of image capture operations are performed.

[0023] In response to an instruction to start shooting, the image sensor 14 is exposed for the exposure time determined by the AE processing. When flash photography is performed, the amount of light to be emitted is determined by the flash pre-flash processing, and the flash is emitted during the exposure of the image sensor 14. When the exposure is completed, the captured image data that has been developed by the image processing circuit 20 and compressed by the compression / expansion circuit 32 is recorded on the recording medium 200.

[0024] The display changeover switch 66 can be operated by the user to instruct changeover of the display on the image display unit 28. For example, when taking a picture using the optical viewfinder 104, power consumption can be reduced by cutting off the current supply to the image display unit 28, which is made up of a TFT LCD or the like.

[0025] The operation unit 70 is used by the user to set various functions of the imaging device 100. For example, it includes a display menu button, a set button, a macro button, a multi-screen playback page break button, a flash setting button, a single shot / continuous shooting / self-timer switching button, etc. It may also include menu movement +- (plus / minus) buttons, playback image movement +- (plus / minus) buttons, a shooting image quality selection button, an exposure compensation button, a date / time setting button, etc.

[0026] The zoom switch 72, operated by the user to change the magnification of the captured image, consists of a telephoto switch that changes the angle of view to the telephoto side and a wide switch that changes it to the wide-angle side. Operating the zoom switch 72 causes the zoom control unit 44 to perform optical zooming of the photographic lens 10. It also allows the image processing circuit 20 to perform cropping of the captured image and electronic zooming of the angle of view using pixel interpolation and the like.

[0027] Each of these operation units may be configured as a single or a combination of various buttons, switches, rotary dials, touch panels, pointing devices using line-of-sight detection, voice recognition devices, and the like.

[0028] The thermistor 74 is a device that measures the temperature inside the imaging device 100. By placing the thermistor 74 near the imaging element 14, it is possible to measure the temperature of the imaging element 14. Since defective pixels in the image data output from the imaging element 14 are affected by temperature, defective pixel correction processing can be performed according to the temperature at the time of shooting.

[0029] The communication unit 110 is for performing various types of communication such as USB, IEEE1394, LAN, wireless communication, etc. By providing an antenna instead of the connector 112, the imaging device 100 can be connected to other devices via wireless communication.

[0030] The optical viewfinder 104 is used to optically observe and photograph a subject image without using the electronic viewfinder function of the image display unit 28 .

[0031] The interface 90 and connector 92 are electrically connected to and communicate with an interface 204 and connector 206 of a recording medium 200 such as a memory card or a hard disk. The recording medium 200 includes a recording unit 202 configured from a semiconductor memory, a magnetic disk, or the like.

[0032] 2 is an equivalent circuit diagram showing a part of the image sensor 14. The image sensor 14 has a large number of pixels arranged in a matrix, of which pixel 130 at row 1, column 1 (1,1) and pixel 131 at an arbitrary row m, column 1 (m,1) are shown. Note that pixel 130 and pixel 131 have similar configurations, and therefore the same components are assigned the same reference numerals.

[0033] In the pixels 130 and 131, when light is incident on a photodiode (PD) 500, which is a photoelectric conversion unit, a signal charge corresponding to the amount of incident light is generated by photoelectric conversion. The signal charge generated in the PD 500 is transferred to and held in a charge holding unit 507A by turning on a first transfer transistor 501A using a transfer pulse φTX1A.

[0034] Furthermore, by turning on the second transfer transistor 502A with a transfer pulse φTX2A, the signal charge held in the charge holding unit 507A is transferred to the floating diffusion region (FD) 508. Then, by turning on the selection transistor 506 with a selection pulse φSEL, the signal charge transferred to the FD 508 by the amplification transistor 505 is converted into a voltage signal according to the charge amount, and is output to the signal output line 523.

[0035] Thereafter, the third transfer transistor 503 is turned on by a transfer pulse φTX3, connecting the PD 500 to the power supply line 521 and discharging the residual charge. The reset transistor 504 and the second transfer transistor 502A are turned on by a reset pulse φRES and a transfer pulse φTX2A, connecting the FD 508 and the charge holding unit 507A to the power supply line 520 and discharging the residual charge. Note that each control pulse is sent from a vertical scanning circuit (not shown).

[0036] The imaging device 100 of this embodiment has an "electronic ND function" that controls the timing of charge accumulation in the imaging element 14 to obtain the same image signal as when the incident light on the imaging element 14 is reduced. In other words, by intermittently accumulating charges multiple times during the exposure period of one frame and collectively reading out the image signals obtained by the multiple charge accumulations, it is possible to obtain substantially the same effect as when the incident light is reduced.

[0037] 3 is a diagram showing a charge accumulation pattern when the electronic ND function is executed using the image sensor 14. Here, the exposure period Tv for one frame is 1 / 30 seconds, and an example is shown in which, based on the reference exposure period of 1 / 30 seconds, charge accumulation is performed intermittently to reduce the charge accumulation time to 1 / 4 and 1 / 16 of the exposure period.

[0038] If the intermittent charge accumulation pattern is determined based on a simple duty ratio, the final charge accumulation period in one frame may end before 1 / 30 seconds have elapsed, as shown in Figure 3(A). This deviation in the end timing of the charge accumulation period becomes even more pronounced when the charge accumulation period is reduced to 1 / 16. Therefore, as shown in Figure 3(B), the intermittent charge accumulation pattern is determined to match the reference exposure period of 1 / 30 seconds. This allows the end timing of the final charge accumulation period in one frame to be approximately the same as the 1 / 30 second exposure period.

[0039] 4 shows the allowable error range between the end timing of the last charge accumulation period in one frame and the elapsed timing of an exposure period of 1 / 30 seconds when intermittent charge accumulation is performed. Here, the exposure period Tv of one frame is 1 / 30 seconds, and the charge accumulation time can be set by the user in units of 1 / 3 Ev.

[0040] In this case, the charge accumulation period can be set in stages to 1 / 20 seconds, 1 / 25 seconds, 1 / 30 seconds, 1 / 40 seconds, and 1 / 50 seconds. If the exposure period of one frame is set to 1 / 30 seconds to reduce the discrepancy with the timing at which the exposure period of one frame elapses, the intermittent charge accumulation pattern is determined so that the end timing of the last charge accumulation period of one frame falls within a predetermined range. In other words, the intermittent charge accumulation pattern is determined so that the end timing falls within the range from when 1 / 25 seconds has elapsed to when 1 / 40 seconds has elapsed.

[0041] If the unit of charge accumulation period set by the user is 1 / 2 Ev, the intermittent charge accumulation pattern is determined so that the difference between the end timing of the last charge accumulation period of one frame and the elapsed timing of the exposure period of one frame falls within a range of 1 / 2 Ev. If the unit of charge accumulation period set by the user is 1 Ev, the intermittent charge accumulation pattern is determined so that the difference between the end timing of the last charge accumulation period of one frame and the elapsed timing of the exposure period of one frame falls within a range of 1 Ev.

[0042] FIG. 5 shows an example of synchronizing intermittent charge accumulation with the horizontal synchronization signal HD. In FIG. 5, the period indicated by the arrow labeled "ideal" indicates a set accumulation period. When performing intermittent charge accumulation, ideally, charge accumulation should begin at the start of the exposure period and end at the end of the exposure period within this period. However, charge accumulation by the image sensor 14 must be controlled to be synchronized with the horizontal synchronization signal HD, which controls the imaging operation.

[0043] Therefore, in this embodiment, an intermittent charge accumulation pattern shown as "period matching" is determined so that the timing of intermittent charge accumulation is shifted to coincide with the issuance timing of the horizontal synchronization signal HD that is closest to the ideal charge accumulation period. Here, charge accumulation is performed intermittently over four separate charge accumulation periods (A) to (D).

[0044] Since the ideal charge accumulation period (A) is slightly shifted from the timing of issuing the horizontal synchronization signal HD, the timing is shifted to the position of the charge accumulation period (A) indicated by period adjustment.

[0045] In addition, the ideal charge accumulation periods (B) and (C) are also shifted to the positions of the charge accumulation periods (B) and (C) shown in cycle alignment in order to match the timing of issuing the nearest horizontal synchronization signal HD.

[0046] If the ideal charge accumulation period (D) were to be synchronized with the issuance timing of the nearest horizontal synchronization signal HD, it would end after the end of the set exposure period. This results in a large time lag, but by synchronizing it with the issuance timing of the nearest horizontal synchronization signal HD, it is possible to complete charge accumulation within the set exposure period.

[0047] In this embodiment, an example has been described in which, when performing intermittent charge accumulation, each ideal charge accumulation period is adjusted to the closest issuance timing of the horizontal synchronization signal HD and controlled so that it always falls within the set exposure period. However, the present invention is not limited to this, and it is also possible to control the set exposure period so that it falls within the period between the start timing of the first intermittent charge accumulation period and the end timing of the last intermittent charge accumulation period.

[0048] FIG. 6 is a diagram showing an example in which intermittent charge accumulation is synchronized with the horizontal synchronization signal HD and gain compensation is performed.

[0049] This section explains the case where intermittent charge accumulation requires not only charge accumulation synchronized with the horizontal synchronization signal HD but also control so that the charge accumulation period is an integer multiple of the horizontal synchronization signal cycle. If the charge accumulation period is controlled so that it is an integer multiple of the horizontal synchronization signal cycle, the sum of the intermittent charge accumulation periods may be shorter than the charge accumulation period required to achieve the desired dimming effect for the set exposure period. In this case, the shortfall in the charge accumulation period is compensated for by signal amplification.

[0050] In this embodiment, we will explain the case where, when performing intermittent charge accumulation, each charge accumulation period needs to be set to a multiple of three with respect to the cycle of the horizontal synchronization signal HD. To perform four intermittent charge accumulations in synchronization with the horizontal synchronization signal HD in order to achieve the desired dimming effect, it is necessary to perform intermittent charge accumulation four times over a period four times the cycle of the horizontal synchronization signal HD (4HD period). Here, each charge accumulation period needs to be set to a multiple of three with respect to the cycle of the horizontal synchronization signal HD.

[0051] However, to perform intermittent charge accumulation over a charge accumulation period equal to 4HD x 4 = 16HD periods, charge accumulation over a period three times the cycle of the horizontal synchronization signal HD (3HD period) must be performed five times. However, since the resulting period is 3HD x 5 = 15HD periods, which means that there is a shortage of signal equivalent to charge accumulation over 1HD period, in this embodiment, the missing signal for 1HD is controlled to be compensated for by amplifying it. The gain required to compensate for 1HD of signal is Gain=16HD / 15HD≒1.067 times Therefore, by amplifying the signal by applying a gain using an amplifier circuit built into the image sensor 14 or the image processing circuit 20, an image signal with a desired dimming effect can be obtained.

[0052] Figure 7 shows the settings screen that allows the user to set the amount of light reduction for the electronic ND function. The electronic ND function requires the user to set the number of steps of light reduction depending on the shooting conditions. Figure 7(A) shows a display that is consistent with the notation used for general optical ND filters. Figure 7(B) shows the amount of light reduction for the electronic ND expressed in steps. The intermittent charge accumulation pattern is determined based on the settings on these settings screens, allowing shooting to be performed using the electronic ND function.

[0053] As described above, photography can be performed based on the desired light reduction effect within the set exposure period.

[0054] While the present invention has been described in detail above based on preferred embodiments thereof, the present invention is not limited to these specific embodiments, and various forms within the scope of the gist of the present invention are also included in the present invention. Furthermore, each of the above-described embodiments merely represents one embodiment of the present invention, and each embodiment can be combined as appropriate.

[0055] For example, in the above embodiment, the imaging device 100 is described as including the photographing lens 10, the image sensor 14, the system control unit 50, and the image display unit 28, but the present invention is not limited to this configuration. For example, it is also possible to realize an imaging system in which the imaging means (the photographing lens 10, the image sensor 14), the system control unit 50, and the display device are configured as separate entities, and are connected to each other so that they can communicate with each other.

[0056] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0057] The disclosure of this embodiment includes the following configuration.

[0058] (Configuration 1) an imaging means for converting an optical image into an electrical signal; a setting means for setting an exposure period of the imaging means; a control means for determining an intermittent charge accumulation pattern so that the timing from the start of the first charge accumulation to the end of the last charge accumulation when intermittent charge accumulation is performed by the imaging means to obtain a light-reducing effect falls within a predetermined range with respect to the start timing and end timing of the exposure period set by the setting means; An imaging device comprising:

[0059] (Configuration 2) The imaging device described in configuration 1, characterized in that the predetermined range is a range in which the difference between the end timing of the last charge accumulation period of one frame and the elapsed timing of the exposure period of one frame is a unit range set by the user for the charge accumulation period.

[0060] (Configuration 3) 3. The imaging device according to configuration 1 or 2, wherein the control means controls the imaging means to perform the intermittent charge accumulation in such a manner that each charge accumulation is performed in synchronization with a horizontal synchronization signal.

[0061] (Configuration 4) 4. The imaging device according to configuration 3, wherein the control means controls the intermittent charge accumulation by the imaging means so that the charge accumulation period of each charge accumulation is an integer multiple of the horizontal synchronization signal.

[0062] (Configuration 5) The imaging device according to configuration 4, wherein the control means controls to amplify signals to compensate for the shortage of the charge accumulation period when the sum of the charge accumulation periods when the imaging means performs the intermittent charge accumulation is shorter than the charge accumulation period required to obtain a desired dimming effect.

[0063] (Configuration 6) 6. The imaging device according to any one of configurations 1 to 5, wherein the control means determines the intermittent charge accumulation pattern in accordance with an amount of light reduction set by a user. [Explanation of symbols]

[0064] 14 Image sensor 18 Timing generator circuit 20 Image processing circuit 50 System control circuit

Claims

1. an imaging means for converting an optical image into an electrical signal; a setting means for setting an exposure period of the imaging means; a control means for determining an intermittent charge accumulation pattern so that the timing from the start of the first charge accumulation to the end of the last charge accumulation when intermittent charge accumulation is performed by the imaging means to obtain a light-reducing effect falls within a predetermined range with respect to the start timing and end timing of the exposure period set by the setting means; An imaging device comprising:

2. 2. The imaging device according to claim 1, wherein the predetermined range is a range of a difference between the end timing of the last charge accumulation period of one frame and the elapse timing of the exposure period of one frame set by a user in units of the charge accumulation period.

3. 2. The imaging device according to claim 1, wherein the control means controls the imaging means to perform the intermittent charge accumulation so that each charge accumulation is performed in synchronization with a horizontal synchronization signal.

4. 4. The imaging device according to claim 3, wherein the control means controls the intermittent charge accumulation by the imaging means so that the charge accumulation period of each charge accumulation is an integer multiple of the horizontal synchronization signal.

5. 5. The imaging device according to claim 4, wherein the control means controls to amplify signals to compensate for the shortage of the charge accumulation period when the sum of the charge accumulation periods when the imaging means performs the intermittent charge accumulation is shorter than the charge accumulation period required to obtain a desired light reduction effect.

6. 2. The image pickup apparatus according to claim 1, wherein the control means determines the intermittent charge accumulation pattern in accordance with an amount of light reduction set by a user.

Images