Imaging device and driving method

Abstract

This imaging device is provided with: a plurality of pixels which each have a photoelectric conversion unit for converting incident light into an electric charge and which each generate a signal based on the electric charge; and a drive control unit that exposes the plurality of pixels. The drive control unit exposes the plurality of pixels so that the plurality of pixels generate: one or more first signals for representing a first signal value corresponding to an electric charge that is obtained by conversion by the photoelectric conversion unit during a period of an exposure pulse (A1) starting at a timing based on a light emission pulse (L); and one or more second signals for representing a second signal value corresponding to an electric charge that is obtained by conversion by the photoelectric conversion unit during a period of an exposure pulse (A2) starting at a timing based on the light emission pulse (L). The exposure pulse (A2) starts, on the basis of the light emission pulse (L), with a prescribed time difference from the start of the exposure pulse (A1). A pulse width (Tp1) of the exposure pulse (A1) and a pulse width (Tp2) of the exposure pulse (A2) are equal to each other, and are each shorter than a pulse width (TpL) of the light emission pulse (L).

Description

Imaging device and driving method

[0001] The present disclosure relates to an imaging device and a method for driving the imaging device.

[0002] Conventionally, imaging devices that generate distance images using an indirect TOF (Time of Flight) method have been known. In generating distance images using the indirect TOF method, for example, a light source emits light, which is reflected by an object, and the distance image is generated based on signals output by the pixels based on the reflected light.

[0003] Multipath light is a problem that reduces the distance measurement accuracy of the indirect TOF method. In contrast to direct-path reflected light, in which primary light from a light source directly hits the target and returns as is, multipath light hits an object other than the target one or more times, resulting in scattered secondary or higher-level light that hits the target and returns. Therefore, when multipath light occurs, the calculated distance to the target is farther than the actual distance. In particular, in distance measurement in a closed space, such as for endoscopic applications, the amount of multipath light increases, leading to greater distance measurement errors.

[0004] In order to reduce the effects of multipath light, Patent Document 1 discloses a distance measuring device that selects a combination of signal charges that is less affected by multipath light from among signal charges corresponding to two combinations of multiple exposure control signals whose phase difference is the same as the pulse width of pulsed light.

[0005] International Publication No. 2023 / 199804

[0006] The technology described in Patent Document 1 cannot reduce the influence of multipath light on the signal charges (signal values) themselves obtained by exposure according to multiple exposure control signals. Therefore, in order to reduce the influence of multipath light, the technology described in Patent Document 1 increases the number of exposures required to calculate the distance, and also complicates the calculation to calculate the distance from the signal charges obtained by exposure.

[0007] Therefore, the present disclosure provides an imaging device and the like that can acquire signal values ​​in which the influence of multipath light is reduced.

[0008] An imaging device according to one aspect of the present disclosure includes a plurality of pixels arranged in a matrix, each of the plurality of pixels having a photoelectric conversion unit that converts incident light into an electric charge and generating a signal based on the electric charge; and a drive control unit that exposes the plurality of pixels to light at a timing based on emission of pulsed light by a light source onto an object, in each of one or more frames, wherein the drive control unit exposes the plurality of pixels so that the plurality of pixels generate one or more first signals representing first signal values ​​corresponding to the electric charges converted by the photoelectric conversion unit in a first period that starts at a timing based on emission of the pulsed light by the light source, and one or more second signals representing second signal values ​​corresponding to the electric charges converted by the photoelectric conversion unit in a second period that starts at a timing based on emission of the pulsed light by the light source, the second period starting at a predetermined time difference from the start of the first period, based on emission of the pulsed light by the light source, and the lengths of the first period and the second period being equal to each other and shorter than a pulse width of the pulsed light.

[0009] A driving method according to one aspect of the present disclosure is a driving method for an imaging device including a plurality of pixels arranged in a matrix, each of the plurality of pixels having a photoelectric conversion unit that converts incident light into an electric charge, and a plurality of pixels that generate signals based on the electric charges, the driving method including exposing the plurality of pixels to light at a timing based on emission of pulsed light by a light source onto an object, in each of one or more frames, wherein exposing the plurality of pixels to light so that the plurality of pixels generate one or more first signals representing first signal values ​​corresponding to the electric charges converted by the photoelectric conversion unit in a first period that starts at a timing based on emission of the pulsed light by the light source, and one or more second signals representing second signal values ​​corresponding to the electric charges converted by the photoelectric conversion unit in a second period that starts at a timing based on emission of the pulsed light by the light source, the second period starting with a predetermined time difference from the start of the first period, and the lengths of the first period and the second period being equal to each other and shorter than a pulse width of the pulsed light.

[0010] According to the present disclosure, it is possible to provide an imaging device or the like that is capable of acquiring signal values ​​in which the influence of multipath light is reduced.

[0011] FIG. 1 is a time chart illustrating the influence of multipath light. FIG. 2 is a functional block diagram illustrating an example of the configuration of an imaging device according to an embodiment. FIG. 3 is a circuit diagram illustrating an example of the circuit configuration of a pixel according to an embodiment. FIG. 4 is a time chart illustrating a first example of a method for driving an imaging device according to an embodiment. FIG. 5 is a time chart illustrating another first example of a method for driving an imaging device according to an embodiment. FIG. 6 is a time chart illustrating a second example of a method for driving an imaging device according to an embodiment. FIG. 7 is a time chart illustrating another second example of a method for driving an imaging device according to an embodiment. FIG. 8 is a time chart illustrating a third example of a method for driving an imaging device according to an embodiment. FIG. 9 is an enlarged view of a first exposure pulse and a second exposure pulse in FIG. 8. FIG. 10 is a diagram illustrating signal values ​​obtained in a third example of a method for driving an imaging device according to an embodiment. FIG. 11 is a time chart illustrating a fourth example of a method for driving an imaging device according to an embodiment. FIG. 12 is a functional block diagram illustrating an example of a configuration of an imaging device according to a modified embodiment.

[0012] (How One Aspect of the Present Disclosure Was Achieved) Before specifically describing the embodiments of the present disclosure, the problems and the like that the inventors of the present invention have found will be described.

[0013] As described above, when generating a range image using the indirect TOF method, the influence of multipath light can cause the calculated distance to an object to be farther than the actual distance.

[0014] FIG. 1 is a time chart illustrating the effect of multipath light. FIG. 1 illustrates an example in which a pixel is exposed to light RL reflected by an object from pulsed light emitted from a light source based on an emission pulse L using a first exposure pulse A1x and a second exposure pulse A2x. FIG. 1 also illustrates a conventional method for driving an imaging device. In the example illustrated in FIG. 1, the pulse width TpL of the emission pulse L, the pulse width Tp1x of the first exposure pulse A1x, and the pulse width Tp2x of the second exposure pulse A2x are the same. Furthermore, the second exposure pulse A2x starts with a time difference of the pulse width TpL from the start of the first exposure pulse A1x. The direct-path reflected light RL reflected by the object enters the pixel with a time Td delay from the emission pulse L.

[0015] 1, a pixel of the imaging device is exposed based on a first exposure pulse A1x and a second exposure pulse A2x, and generates charges based on reflected light RL incident on the pixel. However, during pixel exposure, multi-path light MP also enters the pixel with a delay relative to the reflected light RL, and therefore charges based on the multi-path light MP are also generated in the pixel. Because the multi-path light MP is a component that enters the pixel with a delay relative to the reflected light RL, it causes an error in measuring the distance to the object.

[0016] Therefore, the inventors of the present application focused on a method of shortening the pulse width of pulsed light emitted to an object and the exposure period for exposing pixels in order to obtain signal values ​​with reduced influence of multipath light. By shortening the pulse width and exposure period of pulsed light, pixels are less likely to receive multipath light during exposure, making it possible to obtain signal values ​​with reduced influence of multipath light. For example, in the example shown in FIG. 1 , shortening the pulse width TpL of pulsed light and the exposure period reduces the amount of charge generated based on multipath light MP incident on pixels during exposure. Therefore, it is possible to obtain signal values ​​with reduced influence of multipath light.

[0017] On the other hand, this method has the problem that it is difficult to shorten the pulse width of the pulsed light sufficiently to sufficiently reduce the influence of multipath light due to insufficient responsiveness of the light source that emits the pulsed light.

[0018] Therefore, the inventors of the present application have focused on the need to obtain a signal value in which the influence of multipath light is reduced without shortening the pulse width of the pulsed light, and have arrived at one aspect of the present disclosure.

[0019] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0020] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, components, component placement and connection configurations, steps, and step sequences shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components not recited in independent claims are described as optional components. Each figure is a schematic diagram and is not necessarily an exact illustration. In each figure, substantially identical components are designated by the same reference numerals, and redundant descriptions may be omitted or simplified.

[0021] Furthermore, in this specification, terms indicating the relationship between elements, such as perpendicular, parallel, or coincident, terms indicating the shape of elements, such as circular or rectangular, and numerical ranges are not expressions that only express a strict meaning, but are expressions that also include a substantially equivalent range, for example, a difference of about a few percent.

[0022] Furthermore, in this specification, unless otherwise specified, ordinal numbers such as "first" and "second" do not refer to the number or order of components, etc., but are used for the purpose of avoiding confusion and distinguishing between components of the same type.

[0023] In addition, in this specification, "connection" between elements means electrical connection unless otherwise specified.

[0024] (Embodiment) An imaging device according to the present embodiment will be described below.

[0025] [Configuration] First, the configuration of the imaging device according to this embodiment will be described. Fig. 2 is a functional block diagram showing an example of the configuration of the imaging device 100 according to this embodiment. Fig. 3 is a circuit diagram showing an example of the circuit configuration of the pixel 22 according to this embodiment.

[0026] 2 , the imaging device 100 includes a light source 10, a solid-state imaging element 20, a drive control unit 30, and a distance calculation unit 40. The imaging device 100 is, for example, an imaging device that generates a distance image of an object. The imaging device 100 is not particularly limited in its application, but may be used in an endoscope system. As will be described later, the imaging device 100 is capable of acquiring signal values ​​in which the influence of multipath light is reduced, and is therefore particularly useful when capturing distance images in a closed space, such as in an endoscope system.

[0027] The light source 10 emits pulsed light to be irradiated onto an object in accordance with the timing indicated by the light emission pulse included in the input light emission control signal. The light source 10 includes a light emitting element, such as a light emitting diode or a laser element, that emits visible light or infrared light, and an optical system that receives the light from the light emitting element and controls the light distribution from the light emitting element.

[0028] The solid-state imaging element 20 is, for example, a charge coupled device (CCD) sensor or a complementary metal oxide semiconductor (CMOS) sensor. The solid-state imaging element 20 is, for example, a single-chip element. The solid-state imaging element 20 includes a pixel array 21 configured with a plurality of pixels 22 arranged in a matrix. The plurality of pixels 22 have, for example, the same configuration as each other. The number of pixels 22 shown in FIG. 2 is an example and is not particularly limited.

[0029] The pixels 22 generate signals based on incident light. Specifically, the pixels 22 convert incident light into electric charges and generate signals based on the converted electric charges.

[0030] 3, the pixel 22 includes a photoelectric conversion unit 23, a transfer transistor 24, a charge accumulation unit 25, a charge discharge transistor 26, a source follower transistor 27, a selection transistor 28, and a reset transistor 29. The transfer transistor 24, the charge accumulation unit 25, the charge discharge transistor 26, the source follower transistor 27, the selection transistor 28, and the reset transistor 29 are each, for example, an N-channel MOSFET (Metal Oxide Semiconductor FET). Note that the circuit configuration of the pixel 22 shown in FIG. 3 is merely an example and can be modified as appropriate.

[0031] The photoelectric conversion unit 23 generates electric charges by converting incident light incident on the pixel 22 into electric charges. The incident light incident on the pixel 22 includes, for example, pulsed light emitted from the light source 10 and reflected by an object. The photoelectric conversion unit 23 is composed of, for example, a photoelectric conversion element such as a photodiode. The photoelectric conversion unit 23 is connected to one of the source and drain of the transfer transistor 24 and one of the source and drain of the charge discharge transistor 26.

[0032] The transfer transistor 24 transfers the charges converted by the photoelectric conversion unit 23 from the photoelectric conversion unit 23 to the charge accumulation unit 25. The other of the source and drain of the transfer transistor 24 is connected to the charge accumulation unit 25. A transfer control signal TG that controls the on / off of the transfer transistor 24 is applied to the gate of the transfer transistor 24.

[0033] The charge accumulation unit 25 accumulates the charges converted by the photoelectric conversion unit 23 and transferred by the transfer transistor 24. Specifically, the charge accumulation unit 25 accumulates the charges converted by the photoelectric conversion unit 23 while the pixel 22 is exposed to light. The charge accumulation unit 25 is, for example, an impurity region formed on a semiconductor substrate and capable of being in a floating state. The charge accumulation unit 25 may also include wiring capacitance.

[0034] The charge discharging transistor 26 discharges the charge converted by the photoelectric conversion unit 23 to the outside of the pixel 22. A power supply voltage VDD is applied to the other of the source and drain of the charge discharging transistor 26. A charge discharging control signal PRS that controls the on / off of the charge discharging transistor 26 is applied to the gate of the charge discharging transistor 26.

[0035] The source follower transistor 27 outputs a signal corresponding to the potential of the charge storage unit 25. That is, the source follower transistor 27 reads out the charge stored in the charge storage unit 25. The gate of the source follower transistor 27 is connected to the charge storage unit 25. A power supply voltage VDD is applied to one of the source and drain of the source follower transistor 27. The other of the source and drain of the source follower transistor 27 is connected to one of the source and drain of the selection transistor 28, and the source follower transistor 27 outputs a signal corresponding to the potential of the charge storage unit 25 to the bit line BL via the selection transistor 28. The source follower transistor 27 forms a source follower circuit together with a current source connected to the bit line BL.

[0036] The other of the source and drain of the selection transistor 28 is connected to a bit line BL, which is a signal line through which a signal from the pixel 22 is output. A selection control signal SEL that controls the on / off of the selection transistor 28 is applied to the gate of the selection transistor 28. When the selection transistor 28 is turned on, charge is read out by the source follower transistor 27. The signal from the pixel 22 output to the bit line BL is converted into a digital signal by, for example, an AD conversion circuit (not shown) and input to the distance calculation unit 40.

[0037] The reset transistor 29 resets the potential of the charge storage unit 25. One of the source and drain of the reset transistor 29 is connected to the charge storage unit 25. The power supply voltage VDD is applied to the other of the source and drain of the reset transistor 29. A reset control signal RS that controls the on / off of the reset transistor 29 is applied to the gate of the reset transistor 29. When the reset transistor 29 is turned on, the potential of the charge storage unit 25 is reset to the power supply voltage VDD.

[0038] The transfer control signal TG, the charge discharge control signal PRS, the selection control signal SEL, and the reset control signal RS are generated by, for example, the drive control unit 30 .

[0039] Referring again to FIG. 2 , the drive control unit 30 controls the driving of the light source 10 and the solid-state imaging element 20. The drive control unit 30 outputs a light emission control signal to the light source 10 to cause the light source 10 to emit pulsed light. The light emission control signal includes, for example, a light emission pulse. The light emission pulse is a pulse that instructs the light source 10 to emit light, and indicates a period during which the light source 10 emits pulsed light. The drive control unit 30 also outputs an exposure control signal to each pixel 22 to expose each pixel 22 to light for a predetermined period. The exposure control signal includes, for example, an exposure pulse. The exposure pulse is a pulse that instructs the pixel 22 to expose, and indicates the exposure period of the pixel 22.

[0040] The drive control unit 30 exposes the plurality of pixels 22 to light in accordance with the exposure control signal, in each of one or more frames, at a timing based on the emission of pulsed light by the light source 10 to the object. As will be described in detail later, the drive control unit 30 exposes the plurality of pixels 22 so that the plurality of pixels 22 generate one or more first signals and one or more second signals. The one or more first signals are signals for representing first signal values ​​corresponding to the charges converted by the photoelectric conversion unit 23 during a first period that starts at a timing based on the emission of pulsed light by the light source 10 to the object. The one or more second signals are signals for representing second signal values ​​corresponding to the charges converted by the photoelectric conversion unit 23 during a second period that starts at a timing based on the emission of pulsed light by the light source 10 to the object.

[0041] Here, the second period starts a predetermined time difference from the start of the first period, based on the emission of pulsed light by the light source 10. As one example, the predetermined time difference is equal to the pulse width of the pulsed light. As another example, the predetermined time difference is shorter than the lengths of the first period and the second period. Furthermore, the lengths of the first period and the second period are equal to each other and shorter than the pulse width of the pulsed light emitted by the light source 10.

[0042] In this specification, a period during which the pixel 22 is exposed to light (also referred to as an "exposure period") refers to a period during which charge used to read out a signal from the pixel 22 is accumulated. Therefore, even if light is incident on the pixel 22 and charge is generated in the photoelectric conversion unit 23, if the signal is not used to read out the signal because the signal is discharged or the like, the pixel is considered to be non-exposed. For example, exposure refers to a state in which the charge discharge transistor 26 is off, so that the charge generated in the photoelectric conversion unit 23 is not discharged, and the transfer transistor 24 is on, so that charge is transferred from the photoelectric conversion unit 23 to the charge accumulation unit 25. In addition, during the exposure period of the pixel 22, the transfer transistor 24 does not need to be constantly on as long as the charge generated in the photoelectric conversion unit 23 is transferred to the charge accumulation unit 25 by the end of the exposure period.

[0043] The distance calculation unit 40 calculates the distance to the object irradiated with pulsed light from the light source 10 based on signals output from the plurality of pixels 22 of the solid-state imaging element 20. The distance calculation unit 40 calculates the distance to the object based on, for example, the one or more first signals and the one or more second signals. The distance calculation unit 40 generates a distance image indicating the calculated distance and outputs the image to the outside of the imaging device 100, for example.

[0044] The drive control unit 30 and the distance calculation unit 40 are processing circuits realized by, for example, a memory that stores a program and a processor that executes the program. Although shown as separate blocks in the block diagram, all or part of the drive control unit 30 and the distance calculation unit 40 may be configured with the same memory and processor. Furthermore, the drive control unit 30 and the distance calculation unit 40 may be dedicated logic circuits that perform predetermined processing. Furthermore, at least one of the drive control unit 30 and the distance calculation unit 40 may be provided within the solid-state imaging element 20.

[0045] [Driving Method] A driving method for the imaging device 100 according to this embodiment will be described below.

[0046] (1) First Example of Driving Method First, a first example of a driving method of the imaging device 100 according to the present embodiment will be described. Fig. 4 is a time chart for explaining the first example of a driving method of the imaging device 100 according to the present embodiment.

[0047] "Light emission pulse L" in Fig. 4 indicates the light emission pulse L in the light emission control signal output from the drive control unit 30 to the light source 10. Based on the light emission pulse L, the light source 10 emits pulsed light for the period from the rising edge to the falling edge of the light emission pulse L. Therefore, the pulse width TpL of the light emission pulse L can be said to be the pulse width of the pulsed light. Note that although the light emission pulse L is a rectangular wave in the example shown in Fig. 4, it may also be a triangular wave.

[0048] 4, the "first exposure pulse A1" indicates the first exposure pulse A1 output from the drive control unit 30 to the pixel 22. Specifically, the first exposure pulse A1 is applied to the gate of the transfer transistor 24 as a transfer control signal TG. This turns on the transfer transistor 24 during the period of the first exposure pulse A1, and the charge converted by the photoelectric conversion unit 23 is accumulated in the charge accumulation unit 25.

[0049] 4, the "second exposure pulse A2" indicates the second exposure pulse A2 output from the drive control unit 30 to the pixel 22. Specifically, the second exposure pulse A2 is applied to the gate of the transfer transistor 24 as a transfer control signal TG. This turns on the transfer transistor 24 during the period of the second exposure pulse A2, and the charge converted by the photoelectric conversion unit 23 is accumulated in the charge accumulation unit 25.

[0050] Although not shown, at the start of each of the exposure pulses, the charge drain transistor 26 is turned from off to on.

[0051] In addition, the "first exposure pulse A1" and "second exposure pulse A2" in Figure 4 also show the period during which the direct path reflected light RL of the pulsed light emitted from the light source 10 by the object and the multipath light MP are incident on the pixel 22.

[0052] 4, the first exposure pulse A1 is output from the drive control unit 30 in the first frame to a first pixel, which is one of the plurality of pixels 22. The second exposure pulse A2 is output from the drive control unit 30 to the pixel 22 in a frame different from or the same as that of the first exposure pulse A1.

[0053] When the second exposure pulse A2 is output in a frame different from that in which the first exposure pulse A1 is output, the second exposure pulse A2 is output from the drive control unit 30 to the first pixel in the second frame.

[0054] When the second exposure pulse A2 is output in the same frame as the first exposure pulse A1, the second exposure pulse A2 is output from the drive control unit 30 to a second pixel, which is another one of the multiple pixels 22, in the first frame.

[0055] Here, the first frame and the second frame are, for example, consecutive frames. Either the first frame or the second frame may be first. Furthermore, the first pixel and the second pixel are, for example, pixels adjacent to each other. The plurality of pixels 22 may include a plurality of first pixels and a plurality of second pixels. For example, the plurality of pixels 22 are arranged such that the first pixels and the second pixels alternate in at least one of the row direction and the column direction.

[0056] 4 shows one light emitting pulse L, one first exposure pulse A1, and one second exposure pulse A2. The drive control unit 30 may repeatedly output the light emitting pulse L, the first exposure pulse A1, and the second exposure pulse A2 multiple times in one frame.

[0057] In addition, when the pixel 22 has two transfer transistors 24 and two charge storage sections 25, the drive control section 30 can also output the first exposure pulse A1 and the second exposure pulse A2 to one pixel 22 in the same frame.

[0058] 4, the drive control unit 30 outputs a light emission pulse L to the light source 10. As a result, the light source 10 emits pulsed light that is irradiated onto an object during the period of the light emission pulse L. Direct path reflected light RL of the pulsed light reflected by the object enters the pixel 22 with a delay of time Td from the emission of the pulsed light by the light source 10, depending on the distance to the object. Furthermore, multipath light MP enters the pixel 22 with an even greater delay than the reflected light RL.

[0059] The drive control unit 30 also outputs a first exposure pulse A1 to the pixel 22. As a result, the drive control unit 30 exposes the pixel 22 during the period of the first exposure pulse A1, and causes the pixel 22 to generate a first exposure signal based on the charge generated during that period. The first exposure signal is a first signal that represents a first signal value corresponding to the charge converted by the photoelectric conversion unit 23 during the period of the first exposure pulse A1. The period of the first exposure pulse A1 is an example of a first period, and the pulse width Tp1 of the first exposure pulse A1 is an example of the length of the first period.

[0060] The drive control unit 30 also outputs a second exposure pulse A2 to the pixel 22. As a result, the drive control unit 30 exposes the pixel 22 during the period of the second exposure pulse A2, and causes the pixel 22 to generate a second exposure signal based on the charge generated during that period. The second exposure signal is a second signal that represents a second signal value corresponding to the charge converted by the photoelectric conversion unit 23 during the period of the second exposure pulse A2. The period of the second exposure pulse A2 is an example of a second period, and the pulse width Tp2 of the second exposure pulse A2 is an example of the length of the second period.

[0061] The first exposure pulse A1 and the second exposure pulse A2 each start at a timing based on the light emission pulse L. The pulse width Tp1 of the first exposure pulse A1 and the pulse width Tp2 of the second exposure pulse A2 are equal to each other and shorter than the pulse width TpL of the light emission pulse L. The pulse width Tp1 and the pulse width Tp2 are, for example, 0.5 times or less the pulse width TpL. There are no particular lower limits for the pulse width Tp1 and the pulse width Tp2 as long as the necessary distance measurement range can be ensured, but the pulse width Tp1 and the pulse width Tp2 may be 0.01 times or more or 0.1 times or more the pulse width TpL.

[0062] In the example shown in FIG. 4 , the first exposure pulse A1 starts simultaneously with the start of the light emission pulse L. Furthermore, the second exposure pulse A2 starts with a time difference between the start of the first exposure pulse A1 and the pulse width TpL of the light emission pulse L, using the light emission pulse L as the reference. More specifically, the second exposure pulse A2 starts with a delay of the pulse width TpL of the light emission pulse L from the start of the first exposure pulse A1, using the light emission pulse L as the reference. Note that the drive control unit 30 may output one or more additional exposure pulses to the pixel 22 after the second exposure pulse A2. In this case, the multiple exposure pulses including the first exposure pulse A1 and the second exposure pulse A2 start with a time difference of the pulse width TpL. This enables the ranging range of the imaging device 100 to be expanded.

[0063] The distance calculation unit 40 calculates the distance to the object based on the first exposure signal and the second exposure signal generated by the pixel 22. Because there is a phase difference between the first exposure pulse A1 and the second exposure pulse A2 equal to the pulse width TpL of the light emission pulse L, the signal component corresponding to the reflected light RL is distributed between the first exposure signal and the second exposure signal according to the time Td, which correlates with the distance to the object. In other words, the ratio between the magnitude of the first signal value and the magnitude of the second signal value corresponds to the time Td by which the reflected light RL is delayed relative to the light emission pulse L. Therefore, if the first signal value represented by the first exposure signal is a1, the second signal value represented by the second exposure signal is a2, and the speed of light is c, the distance Z to the object is calculated using the following formula (1). Note that since Tp1 = Tp2, Tp1 may be replaced with Tp2 in the following formula (1).

[0064]

[0065] In the example shown in FIG. 4 , the pulse width Tp1 of the first exposure pulse A1 is shorter than the pulse width TpL of the light emission pulse L, and the first exposure pulse A1 ends before the multipath light MP is incident on the pixel 22. In other words, the first signal value a1 does not include a component of the multipath light MP. Furthermore, the pulse width Tp2 of the second exposure pulse A2 is shorter than the pulse width TpL of the light emission pulse L. Therefore, although the second signal value a2 includes a component of the multipath light MP, the component of the multipath light MP in the second signal value a2 can be reduced. For example, in the conventional example shown in FIG. 1 , all of the multipath light MP after the reflected light RL no longer enters the pixel enters the pixel during exposure. On the other hand, in the example shown in FIG. 4 , only a portion of the multipath light MP after the reflected light RL no longer enters the pixel 22 enters the pixel 22 during exposure. In this way, by making the pulse width Tp1 and the pulse width Tp2 shorter than the pulse width TpL, the components of the multipath light MP in the first signal value a1 and the second signal value a2 can be reduced. Therefore, the imaging device 100 can acquire signal values ​​in which the influence of the multipath light MP is reduced. Furthermore, by reducing the influence of the multipath light MP, the imaging device 100 can improve the accuracy of the distance calculated by the distance calculation unit 40.

[0066] In the example shown in Fig. 4, the first exposure pulse A1 starts simultaneously with the start of the light emission pulse L, but this is not limited to this. Fig. 5 is a time chart for explaining another first example of a method for driving the imaging device 100 according to the present embodiment. In Fig. 5, the descriptions of the matters indicated by "light emission pulse L," "first exposure pulse A1," and "second exposure pulse A2" are the same as those in Fig. 4. The example of the driving method shown in Fig. 5 differs from the example of the driving method shown in Fig. 4 in that the first exposure pulse A1 and the second exposure pulse A2 start with a delay, without changing the time difference between the start of the first exposure pulse A1 and the start of the second exposure pulse A2.

[0067] 5, the first exposure pulse A1 starts a time T0 after the start of the light emission pulse L. The second exposure pulse A2 starts a pulse width TpL after the start of the first exposure pulse A1, with the light emission pulse L as the reference. This makes it possible to distribute the signal component corresponding to the reflected light RL between the first exposure signal and the second exposure signal, even when the distance to the object is long and the time Td is long. The distance calculation unit 40 calculates the distance Z by adding c×T0 / 2 to the above equation (1).

[0068] (2) Second Example of Driving Method Next, a second example of a driving method for the imaging device 100 according to the present embodiment will be described. The following description of the second example will focus on differences from the first example, and descriptions of commonalities will be omitted or simplified.

[0069] 6 is a time chart for explaining a second example of a method for driving the imaging device 100 according to the present embodiment. In FIG. 6, the description of the items indicated by "light emitting pulse L" is the same as in FIG.

[0070] 6, the "third exposure pulse A11" indicates the third exposure pulse A11 output from the drive control unit 30 to the pixel 22. Specifically, the third exposure pulse A11 is applied to the gate of the transfer transistor 24 as a transfer control signal TG. As a result, the transfer transistor 24 is turned on during the period of the third exposure pulse A11, and the charge converted by the photoelectric conversion unit 23 is accumulated in the charge accumulation unit 25.

[0071] 6 shows the fourth exposure pulse A12 output from the drive control unit 30 to the pixel 22. Specifically, the fourth exposure pulse A12 is applied to the gate of the transfer transistor 24 as a transfer control signal TG. This turns on the transfer transistor 24 during the period of the fourth exposure pulse A12, and the charge converted by the photoelectric conversion unit 23 is accumulated in the charge accumulation unit 25.

[0072] 6 shows the fifth exposure pulse A21 output from the drive control unit 30 to the pixel 22. Specifically, the fifth exposure pulse A21 is applied to the gate of the transfer transistor 24 as a transfer control signal TG. This turns on the transfer transistor 24 during the period of the fifth exposure pulse A21, and the charge converted by the photoelectric conversion unit 23 is accumulated in the charge accumulation unit 25.

[0073] 6 shows the sixth exposure pulse A22 output from the drive control unit 30 to the pixel 22. Specifically, the sixth exposure pulse A22 is applied to the gate of the transfer transistor 24 as a transfer control signal TG. This turns on the transfer transistor 24 during the period of the sixth exposure pulse A22, and the charge converted by the photoelectric conversion unit 23 is accumulated in the charge accumulation unit 25.

[0074] Although not shown, at the start of each of the exposure pulses, the charge drain transistor 26 is turned from off to on.

[0075] 6, the "third exposure pulse A11," "fourth exposure pulse A12," "fifth exposure pulse A21," and "sixth exposure pulse A22" also indicate the periods during which the direct path reflected light RL of the pulsed light emitted from the light source 10 by the object and the multipath light MP are incident on the pixel 22, as in FIG. 4.

[0076] 6, the third exposure pulse A11 is output from the drive control unit 30 in the first frame to a first pixel, which is one of the plurality of pixels 22. The third exposure pulse A11, the fourth exposure pulse A12, the fifth exposure pulse A21, and the sixth exposure pulse A22 are output from the drive control unit 30 to the pixel 22 in different frames or in the same frame.

[0077] When the third exposure pulse A11, the fourth exposure pulse A12, the fifth exposure pulse A21, and the sixth exposure pulse A22 are output in different frames, the fourth exposure pulse A12 is output from the drive control unit 30 to the first pixel in the second frame. In this case, the fifth exposure pulse A21 is output from the drive control unit 30 to the first pixel in the third frame. In this case, the sixth exposure pulse A22 is output from the drive control unit 30 to the first pixel in the fourth frame.

[0078] When the third exposure pulse A11, the fourth exposure pulse A12, the fifth exposure pulse A21, and the sixth exposure pulse A22 are output in the same frame, the fourth exposure pulse A12 is output from the drive control unit 30 in the first frame to a second pixel, which is another one of the plurality of pixels 22. In this case, the fifth exposure pulse A21 is output from the drive control unit 30 in the first frame to a third pixel, which is yet another one of the plurality of pixels 22. In this case, the sixth exposure pulse A22 is output from the drive control unit 30 in the first frame to a fourth pixel, which is yet another one of the plurality of pixels 22.

[0079] The first, second, third, and fourth frames are, for example, consecutive frames. The order of the first, second, third, and fourth frames is not particularly limited. The first, second, third, and fourth pixels are, for example, adjacent pixels. The plurality of pixels 22 may include a plurality of first pixels, a plurality of second pixels, a plurality of third pixels, and a plurality of fourth pixels. For example, the plurality of pixels 22 are arranged in the row and column directions as blocks of four pixels 22, each consisting of a first pixel, a second pixel, a third pixel, and a fourth pixel that are adjacent to each other.

[0080] Two of the third exposure pulse A11, the fourth exposure pulse A12, the fifth exposure pulse A21, and the sixth exposure pulse A22 may be output to two different pixels 22 in the same frame, and the remaining two may be output to the two pixels 22 in another frame. Furthermore, when a pixel 22 includes two transfer transistors 24 and two charge accumulation units 25, the drive control unit 30 may output two of the third exposure pulse A11, the fourth exposure pulse A12, the fifth exposure pulse A21, and the sixth exposure pulse A22, and the remaining two, to one pixel 22 over two frames.

[0081] 6 shows one light emitting pulse L, one third exposure pulse A11, one fourth exposure pulse A12, one fifth exposure pulse A21, and one sixth exposure pulse A22. The drive control unit 30 may repeatedly output the light emitting pulse L, the third exposure pulse A11, the fourth exposure pulse A12, the fifth exposure pulse A21, and the sixth exposure pulse A22 multiple times in one frame.

[0082] 6 , the drive control unit 30 outputs a third exposure pulse A11 to the pixel 22. As a result, the drive control unit 30 exposes the pixel 22 during the period of the third exposure pulse A11, causing the pixel 22 to generate a third exposure signal based on the charge generated during that period. The third exposure signal is one of one or more first signals representing a first signal value a1 corresponding to the charge converted by the photoelectric conversion unit 23 during the period of the first exposure pulse A1 in the first example. The period of the third exposure pulse A11 is an example of a third period, and the pulse width Tp3 of the third exposure pulse A11 is an example of the length of the third period.

[0083] The drive control unit 30 also outputs a fourth exposure pulse A12 to the pixel 22. As a result, the drive control unit 30 exposes the pixel 22 during the period of the fourth exposure pulse A12, and causes the pixel 22 to generate a fourth exposure signal based on the charge generated during that period. The fourth exposure signal is another one of one or more first signals representing a first signal value a1 corresponding to the charge converted by the photoelectric conversion unit 23 during the period of the first exposure pulse A1 in the first example. The period of the fourth exposure pulse A12 is an example of a fourth period, and the pulse width Tp4 of the fourth exposure pulse A12 is an example of the length of the fourth period.

[0084] The drive control unit 30 also outputs a fifth exposure pulse A21 to the pixel 22. As a result, the drive control unit 30 exposes the pixel 22 during the period of the fifth exposure pulse A21, and causes the pixel 22 to generate a fifth exposure signal based on the charge generated during that period. The fifth exposure signal is one of one or more second signals representing a second signal value a2 corresponding to the charge converted by the photoelectric conversion unit 23 during the period of the second exposure pulse A2 in the first example. The period of the fifth exposure pulse A21 is an example of a fifth period, and the pulse width Tp5 of the fifth exposure pulse A21 is an example of the length of the fifth period.

[0085] The drive control unit 30 also outputs a sixth exposure pulse A22 to the pixel 22. As a result, the drive control unit 30 exposes the pixel 22 during the period of the sixth exposure pulse A22, causing the pixel 22 to generate a sixth exposure signal based on the charge generated during that period. The sixth exposure signal is another one of the one or more second signals representing a second signal value a2 corresponding to the charge converted by the photoelectric conversion unit 23 during the period of the second exposure pulse A2 in the first example. The period of the sixth exposure pulse A22 is an example of a sixth period, and the pulse width Tp6 of the sixth exposure pulse A22 is an example of the length of the sixth period.

[0086] The pulse width Tp4 of the fourth exposure pulse A12 is shorter than the pulse width Tp3 of the third exposure pulse A11. Furthermore, the pulse widths Tp3 and Tp4 are longer than the pulse width Tp1 of the first exposure pulse A1 in the first example. Furthermore, with the light emission pulse L as the reference, the period of the third exposure pulse A11 and the period of the fourth exposure pulse A12 overlap so that their ends coincide, and the period where the period of the third exposure pulse A11 and the period of the fourth exposure pulse A12 do not overlap is the same as the period of the first exposure pulse A1 in the first example. In other words, with the light emission pulse L as the reference, the difference between the period of the third exposure pulse A11 and the period of the fourth exposure pulse A12 is the period of the first exposure pulse A1 shown in FIG. 4 .

[0087] Furthermore, the pulse width Tp6 of the sixth exposure pulse A22 is shorter than the pulse width Tp5 of the fifth exposure pulse A21. Furthermore, the pulse widths Tp5 and Tp6 are longer than the pulse width Tp2 of the second exposure pulse A2 in the first example. Furthermore, with the light emission pulse L as the reference, the periods of the fifth exposure pulse A21 and the sixth exposure pulse A22 overlap so that their ends coincide, and the period where the periods of the fifth exposure pulse A21 and the sixth exposure pulse A22 do not overlap is the same as the period of the second exposure pulse A2 in the first example. In other words, with the light emission pulse L as the reference, the difference between the periods of the fifth exposure pulse A21 and the sixth exposure pulse A22 is the period of the second exposure pulse A2 shown in FIG. 4 .

[0088] The third exposure pulse A11, fourth exposure pulse A12, fifth exposure pulse A21, and sixth exposure pulse A22 each start at a timing based on the light emission pulse L. In the example shown in Fig. 6, the third exposure pulse A11 starts simultaneously with the start of the light emission pulse L. The fourth exposure pulse A12 starts, based on the light emission pulse L, with a delay of the start of the third exposure pulse A11 by the pulse width Tp1 of the first exposure pulse A1 in the first example. The fifth exposure pulse A21 starts, based on the light emission pulse L, with a delay of the start of the third exposure pulse A11 by the pulse width TpL of the light emission pulse L. The sixth exposure pulse A22 starts, based on the light emission pulse L, with a delay of the start of the fifth exposure pulse A21 by the pulse width Tp2 of the second exposure pulse A2 in the first example.

[0089] 6, the pulse width Tp3 of the third exposure pulse A11 and the pulse width Tp5 of the fifth exposure pulse A21 are equal to each other. The pulse width Tp4 of the fourth exposure pulse A12 and the pulse width Tp6 of the sixth exposure pulse A22 are equal to each other. Note that, as long as the difference between the pulse widths Tp3 and Tp4 is equal to the pulse width Tp1, the lengths of the pulse widths Tp3 and Tp4 are not particularly limited. Similarly, as long as the difference between the pulse widths Tp5 and Tp6 is equal to the pulse width Tp2, the lengths of the pulse widths Tp5 and Tp6 are not particularly limited.

[0090] The distance calculation unit 40 calculates the distance to the object based on the third exposure signal, fourth exposure signal, fifth exposure signal, and sixth exposure signal generated by the pixel 22. Specifically, the difference between the signal value of the third exposure signal and the signal value of the fourth exposure signal is the first signal value a1 in the first example. The difference between the signal value of the fifth exposure signal and the signal value of the sixth exposure signal is the second signal value a2 in the second example. The difference between the pulse width Tp3 and the pulse width Tp4 is the pulse width Tp1 in the first example. Therefore, the distance calculation unit 40 can calculate the distance Z to the object using the above formula (1).

[0091] In the second example, the difference between the period of the third exposure pulse A11 and the period of the fourth exposure pulse A12 corresponds to the period of the first exposure pulse A1. Therefore, the pulse width Tp3 of the third exposure pulse A11 and the pulse width Tp4 of the fourth exposure pulse A12 can be made longer than the pulse width Tp1 of the first exposure pulse A1. Furthermore, the difference between the period of the fifth exposure pulse A21 and the period of the sixth exposure pulse A22 corresponds to the period of the second exposure pulse A2. Therefore, the pulse width Tp5 of the fifth exposure pulse A21 and the pulse width Tp6 of the sixth exposure pulse A22 can be made longer than the pulse width Tp2 of the second exposure pulse A2. To generate exposure pulses with short pulse widths, it is necessary to increase the size of the circuitry for supplying exposure pulses to the pixels 22. In the second example, as described above, the pulse widths Tp3, Tp4, Tp5, and Tp6 of the third exposure pulse A11, the fourth exposure pulse A12, the fifth exposure pulse A21, and the sixth exposure pulse A22 can be lengthened, thereby suppressing an increase in the circuit size for supplying the exposure pulses to the pixels 22. Furthermore, the third exposure signal, the fourth exposure signal, the fifth exposure signal, and the sixth exposure signal can represent the first signal value a1 and the second signal value a2 similar to those in the first example described above, so the imaging device 100 can acquire signal values ​​in which the influence of multipath light MP is reduced.

[0092] In the second example, the period of the third exposure pulse A11 and the period of the fourth exposure pulse A12 are not particularly limited as long as the difference between them is the period of the first exposure pulse A1. When the light emission pulse L is used as a reference, the period of the third exposure pulse A11 and the period of the fourth exposure pulse A12 may overlap so that their starts coincide instead of their ends coincide. Similarly, the period of the fifth exposure pulse A21 and the period of the sixth exposure pulse A22 are not particularly limited as long as the difference between them is the period of the second exposure pulse A2. When the light emission pulse L is used as a reference, the period of the fifth exposure pulse A21 and the period of the sixth exposure pulse A22 may overlap so that their starts coincide instead of their ends coincide.

[0093] Fig. 7 is a time chart for explaining another second example of a method for driving the imaging device 100 according to the present embodiment. In Fig. 7, the descriptions of the matters indicated by "light emitting pulse L," "third exposure pulse A11," "fourth exposure pulse A12," "fifth exposure pulse A21," and "sixth exposure pulse A22" are the same as those in Fig. 6. The example of the driving method shown in Fig. 7 differs from the example of the driving method shown in Fig. 6 in that the period of the fifth exposure pulse A21 and the period of the sixth exposure pulse A22 overlap so that their starts coincide with each other.

[0094] 7, the fifth exposure pulse A21 starts, using the light emission pulse L as the reference, with a delay from the start of the third exposure pulse A11 that is shorter than the pulse width TpL of the light emission pulse L. Furthermore, using the light emission pulse L as the reference, the period of the fifth exposure pulse A21 and the period of the sixth exposure pulse A22 overlap so that their starts coincide, and the period during which the period of the fifth exposure pulse A21 and the period of the sixth exposure pulse A22 do not overlap is the same as the period of the second exposure pulse A2 in the first example. In other words, similar to the example shown in FIG. 6, the difference between the period of the fifth exposure pulse A21 and the period of the sixth exposure pulse A22 is the period of the second exposure pulse A2.

[0095] 7, the start of the period of the fifth exposure pulse A21 and the period of the sixth exposure pulse A22 coincide with each other, so the end of the fifth exposure pulse A21 and the sixth exposure pulse A22 does not occur later than the end of the second exposure pulse A2 in the first example. In other words, the timing of the end of exposure of the pixel 22 can be advanced. This makes it possible to increase the frame rate.

[0096] (3) Third Example of Driving Method Next, a third example of the driving method of the imaging device 100 according to the present embodiment will be described. The following description of the third example will focus on the differences from the first and second examples, and the description of the commonalities will be omitted or simplified.

[0097] Fig. 8 is a time chart for explaining a third example of a method for driving image pickup device 100 according to the present embodiment. Fig. 9 is an enlarged view of first exposure pulse B1 and second exposure pulse B2 in Fig. 8. Fig. 10 is a diagram for explaining signal values ​​obtained in the third example of a method for driving image pickup device 100 according to the present embodiment.

[0098] The explanation of the matter indicated by "light emitting pulse L" in Figures 8 and 9 is the same as in Figure 4. Furthermore, the explanation of the matter indicated by "first exposure pulse B1" and "second exposure pulse B2" in Figures 8 and 9 can be explained by replacing the first exposure pulse A1 and the second exposure pulse A2 with the first exposure pulse B1 and the second exposure pulse B2, respectively, in the explanation of the matter indicated by "first exposure pulse A1" and "second exposure pulse A2" in Figure 4.

[0099] 8 and 9, the "first exposure pulse B1" and "second exposure pulse B2" also indicate the period during which the direct path reflected light RL of the pulsed light emitted from the light source 10 by the object and the multipath light MP are incident on the pixel 22, as in FIG. 4.

[0100] 4. The frames, pixels 22 and times at which the first exposure pulse B1 and the second exposure pulse B2 are output in FIGS. 8 and 9 are the same as those for the first exposure pulse A1 and the second exposure pulse A2 in FIG.

[0101] 8 and 9 , the drive control unit 30 outputs a first exposure pulse B1 to the pixel 22. As a result, the drive control unit 30 exposes the pixel 22 during the period of the first exposure pulse B1, and causes the pixel 22 to generate a first exposure signal based on the charge generated during that period. The first exposure signal is a first signal that represents a first signal value b1 that corresponds to the charge converted by the photoelectric conversion unit 23 during the period of the first exposure pulse B1. The period of the first exposure pulse B1 is an example of a first period, and the pulse width Tp11 of the first exposure pulse B1 is an example of the length of the first period.

[0102] The drive control unit 30 also outputs a second exposure pulse B2 to the pixel 22. As a result, the drive control unit 30 exposes the pixel 22 during the period of the second exposure pulse B2, and causes the pixel 22 to generate a second exposure signal based on the charge generated during that period. The second exposure signal is a second signal that represents a second signal value b2 that corresponds to the charge converted by the photoelectric conversion unit 23 during the period of the second exposure pulse B2. The period of the second exposure pulse B2 is an example of a second period, and the pulse width Tp12 of the second exposure pulse B2 is an example of the length of the second period.

[0103] The first exposure pulse B1 and the second exposure pulse B2 differ from the first exposure pulse A1 and the second exposure pulse A2 in the first example above in that the time difference between their start timings is different. Specifically, the first exposure pulse B1 and the second exposure pulse B2 each start at a timing based on the light emission pulse L. The pulse width Tp11 of the first exposure pulse B1 and the pulse width Tp12 of the second exposure pulse B2 are equal to each other and shorter than the pulse width TpL of the light emission pulse L. Hereinafter, the equal pulse width Tp11 of the first exposure pulse B1 and the pulse width Tp12 of the second exposure pulse B2 may be referred to as the pulse width Tp. The pulse width Tp is, for example, 0.5 times or less the pulse width TpL. The lower limits of the pulse width Tp11 and the pulse width Tp12 are not particularly limited as long as the necessary distance measurement range can be ensured, but the pulse width Tp11 and the pulse width Tp12 may be 0.01 times or more or 0.1 times or more the pulse width TpL.

[0104] In the examples shown in FIGS. 8 and 9 , the first exposure pulse B1 starts simultaneously with the start of the light emission pulse L. The second exposure pulse B2 starts with a time difference of half the pulse width Tp (=Tp / 2) from the first exposure pulse B1, based on the light emission pulse L. More specifically, the second exposure pulse B2 starts earlier than the start of the first exposure pulse B1 by half the pulse width Tp, based on the light emission pulse L. Note that the drive control unit 30 may output one or more additional exposure pulses to the pixel 22 after the first exposure pulse B1. In this case, the multiple exposure pulses including the first exposure pulse B1 and the second exposure pulse B2 start with a time difference of the pulse width Tp. This enables the ranging range of the imaging device 100 to be expanded.

[0105] The distance calculation unit 40 calculates the distance to the object based on the first exposure signal and the second exposure signal generated by the pixel 22. As shown in FIG. 9, subtracting the second signal value b2 from the first signal value b1 yields a differential signal value b1-b2 corresponding to the incident light that entered the pixel 22 during a time corresponding to half the pulse width Tp. Also, as shown in FIG. 10, doubling the differential signal value b1-b2 yields a total signal value d1 corresponding to the incident light that entered the pixel 22 during a time corresponding to the pulse width Tp. Furthermore, subtracting the first signal value b1 from the total signal value d1 yields a delayed signal value d2 corresponding to the incident light that entered the pixel 22 during a time corresponding to the time Td, which correlates with the distance to the object. From the above, the distance Z to the object is calculated using the following equation (2).

[0106]

[0107] In the examples shown in FIGS. 8 and 9 , the pulse width Tp11 of the first exposure pulse B1 and the pulse width Tp12 of the second exposure pulse B2 are shorter than the pulse width TpL of the light emission pulse L. Furthermore, because the time difference between the start of the first exposure pulse B1 and the start of the second exposure pulse B2 is half the pulse width Tp, the period of the first exposure pulse B1 and the period of the second exposure pulse B2 overlap. Therefore, in the examples shown in FIGS. 8 and 9 , the first exposure pulse B1 and the second exposure pulse B2 end before the multipath light MP enters the pixel 22. In other words, the first signal value b1 and the second signal value b2 do not contain components of the multipath light MP. In this way, the time difference between the start of the first exposure pulse B1 and the start of the second exposure pulse B2 is shorter than the pulse width Tp, which accelerates the end of exposure of the pixel 22. As a result, the multipath light MP, which enters the pixel 22 later than the reflected light RL, is less likely to enter the pixel 22 during exposure. Therefore, the components of the multipath light MP in the first signal value b1 and the second signal value b2 can be effectively reduced. Therefore, the imaging device 100 can acquire signal values ​​in which the influence of the multipath light MP is reduced. Furthermore, by reducing the influence of the multipath light MP, the imaging device 100 can improve the accuracy of the distance calculated by the distance calculation unit 40.

[0108] In the third example, the time difference between the start of the first exposure pulse B1 and the start of the second exposure pulse B2 is not limited to half the pulse width Tp, and is not particularly limited as long as it is shorter than the pulse width Tp. In the third example, the time difference between the start of the first exposure pulse B1 and the start of the second exposure pulse B2 may be 1 / N times the pulse width Tp, where N is an integer or decimal greater than 1. In this case, the total signal value d1 is obtained by multiplying the difference signal value b1-b2 by N. From the perspective of extending the distance measurement range, N may be 2 or more. In other words, the time difference between the start of the first exposure pulse B1 and the start of the second exposure pulse B2 may be less than half the pulse width Tp. Furthermore, from the perspective of distance measurement accuracy, N may be 4 or less.

[0109] 8 and 9, the first exposure pulse B1 starts simultaneously with the start of the light emitting pulse L, but this is not limiting. As in the example shown in Fig. 5, the first exposure pulse B1 may start with a delay from the start of the light emitting pulse L, without changing the time difference between the start of the first exposure pulse B1 and the start of the second exposure pulse B2.

[0110] (4) Fourth Example of Driving Method Next, a fourth example of the driving method of the imaging device 100 according to the present embodiment will be described. The following description of the fourth example will focus on the differences from the first to third examples, and the description of the commonalities will be omitted or simplified.

[0111] 11 is a time chart illustrating a fourth example of a method for driving the imaging device 100 according to the present embodiment. In FIG. 11, the description of the matters indicated by "light emitting pulse L" is the same as that in FIG. 4. Furthermore, the description of the matters indicated by "third exposure pulse B11," "fourth exposure pulse B12," "fifth exposure pulse B21," and "sixth exposure pulse B22" in FIG. 11 can be explained by replacing the third exposure pulse A11, the fourth exposure pulse A12, the fifth exposure pulse A21, and the sixth exposure pulse A22 in the description of the matters indicated by "third exposure pulse A11," "fourth exposure pulse A12," "fifth exposure pulse A21," and "sixth exposure pulse A22" in FIG. 8 with the third exposure pulse B11, the fourth exposure pulse B12, the fifth exposure pulse B21, and the sixth exposure pulse B22, respectively.

[0112] 4, the "third exposure pulse B11," "fourth exposure pulse B12," "fifth exposure pulse B21," and "sixth exposure pulse B22" in FIG. 11 also indicate the periods during which the direct path reflected light RL of the pulsed light emitted from the light source 10 by the object and the multipath light MP are incident on the pixel 22.

[0113] 6. Furthermore, the frames, pixels 22, and numbers of times at which the third exposure pulse B11, fourth exposure pulse B12, fifth exposure pulse B21, and sixth exposure pulse B22 in FIG. 11 are output are the same as those for the third exposure pulse A11, fourth exposure pulse A12, fifth exposure pulse A21, and sixth exposure pulse A22 in FIG. 6.

[0114] 11 , the drive control unit 30 outputs a third exposure pulse B11 to the pixel 22. As a result, the drive control unit 30 exposes the pixel 22 during the period of the third exposure pulse B11, causing the pixel 22 to generate a third exposure signal based on the charge generated during that period. The third exposure signal is one of one or more first signals representing a first signal value b1 corresponding to the charge converted by the photoelectric conversion unit 23 during the period of the first exposure pulse B1 in the third example. The period of the third exposure pulse B11 is an example of a third period, and the pulse width Tp13 of the third exposure pulse B11 is an example of the length of the third period.

[0115] The drive control unit 30 also outputs a fourth exposure pulse B12 to the pixel 22. As a result, the drive control unit 30 exposes the pixel 22 during the period of the fourth exposure pulse B12 and causes the pixel 22 to generate a fourth exposure signal based on the charge generated during that period. The fourth exposure signal is another one of one or more first signals that represent a first signal value b1 corresponding to the charge converted by the photoelectric conversion unit 23 during the period of the first exposure pulse B1 in the third example. The period of the fourth exposure pulse B12 is an example of a fourth period, and the pulse width Tp14 of the fourth exposure pulse B12 is an example of the length of the fourth period.

[0116] The drive control unit 30 also outputs a fifth exposure pulse B21 to the pixel 22. As a result, the drive control unit 30 exposes the pixel 22 during the period of the fifth exposure pulse B21, causing the pixel 22 to generate a fifth exposure signal based on the charge generated during that period. The fifth exposure signal is one of one or more second signals representing a second signal value b2 corresponding to the charge converted by the photoelectric conversion unit 23 during the period of the second exposure pulse B2 in the third example. The period of the fifth exposure pulse B21 is an example of a fifth period, and the pulse width Tp15 of the fifth exposure pulse B21 is an example of the length of the fifth period.

[0117] The drive control unit 30 also outputs a sixth exposure pulse B22 to the pixel 22. As a result, the drive control unit 30 exposes the pixel 22 during the period of the sixth exposure pulse B22 and causes the pixel 22 to generate a sixth exposure signal based on the charge generated during that period. The sixth exposure signal is another one of one or more second signals representing a second signal value b2 corresponding to the charge converted by the photoelectric conversion unit 23 during the period of the second exposure pulse B2 in the third example. The period of the sixth exposure pulse B22 is an example of a sixth period, and the pulse width Tp16 of the sixth exposure pulse B22 is an example of the length of the sixth period.

[0118] The pulse width Tp14 of the fourth exposure pulse B12 is shorter than the pulse width Tp13 of the third exposure pulse B11. Furthermore, the pulse widths Tp13 and Tp14 are longer than the pulse width Tp11 of the first exposure pulse B1 in the third example. Furthermore, with the light emission pulse L as the reference, the periods of the third exposure pulse B11 and the fourth exposure pulse B12 overlap so that their ends coincide, and the period during which the third exposure pulse B11 and the fourth exposure pulse B12 do not overlap is the same as the period of the first exposure pulse B1 in the third example. In other words, with the light emission pulse L as the reference, the difference between the period of the third exposure pulse B11 and the period of the fourth exposure pulse B12 is the period of the first exposure pulse B1 shown in FIG. 8 .

[0119] Furthermore, the pulse width Tp16 of the sixth exposure pulse B22 is shorter than the pulse width Tp15 of the fifth exposure pulse B21. Furthermore, the pulse widths Tp15 and Tp16 are longer than the pulse width Tp12 of the second exposure pulse B2 in the third example. Furthermore, with the light emission pulse L as the reference, the period of the fifth exposure pulse B21 and the period of the sixth exposure pulse B22 overlap so that their ends coincide, and the period where the period of the fifth exposure pulse B21 and the period of the sixth exposure pulse B22 do not overlap is the same as the period of the second exposure pulse B2 in the third example. In other words, with the light emission pulse L as the reference, the difference between the period of the fifth exposure pulse B21 and the period of the sixth exposure pulse B22 is the period of the second exposure pulse B2 shown in FIG. 8 .

[0120] The third exposure pulse B11, fourth exposure pulse B12, fifth exposure pulse B21, and sixth exposure pulse B22 each start at a timing based on the light emission pulse L. In the example shown in FIG. 11 , the third exposure pulse B11 starts simultaneously with the start of the light emission pulse L. The fourth exposure pulse B12 starts, based on the light emission pulse L, with a delay of the pulse width Tp11 of the first exposure pulse B1 in the third example from the start of the third exposure pulse B11. The fifth exposure pulse B21 starts earlier than the start of the third exposure pulse B11 by half the pulse width Tp (= Tp / 2) based on the light emission pulse L. The sixth exposure pulse B22 starts, based on the light emission pulse L, with a delay of the pulse width Tp12 of the second exposure pulse B2 in the third example from the start of the fifth exposure pulse B21.

[0121] 11 , the pulse width Tp13 of the third exposure pulse B11 and the pulse width Tp15 of the fifth exposure pulse B21 are equal to each other. The pulse width Tp14 of the fourth exposure pulse B12 and the pulse width Tp16 of the sixth exposure pulse B22 are equal to each other. As long as the difference between the pulse widths Tp13 and Tp14 is equal to the pulse width Tp11, the lengths of the pulse widths Tp13 and Tp14 are not particularly limited. Similarly, as long as the difference between the pulse widths Tp15 and Tp16 is equal to the pulse width Tp12, the lengths of the pulse widths Tp15 and Tp16 are not particularly limited.

[0122] The distance calculation unit 40 calculates the distance to the object based on the third exposure signal, fourth exposure signal, fifth exposure signal, and sixth exposure signal generated by the pixel 22. Specifically, the difference between the signal value of the third exposure signal and the signal value of the fourth exposure signal is the first signal value b1 in the third example. The difference between the signal value of the fifth exposure signal and the signal value of the sixth exposure signal is the second signal value b2 in the third example. The difference between the pulse width Tp13 and the pulse width Tp14 is the pulse width Tp11 (in other words, the pulse width Tp) in the third example. Therefore, as in the third example, the distance calculation unit 40 can calculate the distance Z to the object using the above formula (2) by determining the total signal value d1 and the delayed signal value d2 from the first signal value b1 and the second signal value b2.

[0123] In the fourth example, the difference between the period of the third exposure pulse B11 and the period of the fourth exposure pulse B12 corresponds to the period of the first exposure pulse B1. Therefore, the pulse width Tp13 of the third exposure pulse B11 and the pulse width Tp14 of the fourth exposure pulse B12 can be made longer than the pulse width Tp11 of the first exposure pulse B1. Furthermore, the difference between the period of the fifth exposure pulse B21 and the period of the sixth exposure pulse B22 corresponds to the period of the second exposure pulse B2. Therefore, the pulse width Tp15 of the fifth exposure pulse B21 and the pulse width Tp16 of the sixth exposure pulse B22 can be made longer than the pulse width Tp12 of the second exposure pulse B2. To generate exposure pulses with short pulse widths, it is necessary to increase the circuit scale for supplying exposure pulses to the pixels 22. In the fourth example, as described above, the pulse widths Tp13, Tp14, Tp15, and Tp16 of the third exposure pulse B11, the fourth exposure pulse B12, the fifth exposure pulse B21, and the sixth exposure pulse B22 can be lengthened, thereby suppressing an increase in the circuit size for supplying exposure pulses to the pixels 22. Furthermore, the third exposure signal, the fourth exposure signal, the fifth exposure signal, and the sixth exposure signal can represent the first signal value b1 and the second signal value b2 similar to those in the third example described above, so the imaging device 100 can acquire signal values ​​in which the influence of multipath light MP is reduced.

[0124] In the fourth example, the period of the third exposure pulse B11 and the period of the fourth exposure pulse B12 are not particularly limited as long as the difference between them is the period of the first exposure pulse B1. When the light emission pulse L is used as a reference, the period of the third exposure pulse B11 and the period of the fourth exposure pulse B12 may overlap so that their starts coincide instead of their ends coincide. Similarly, the period of the fifth exposure pulse B21 and the period of the sixth exposure pulse B22 are not particularly limited as long as the difference between them is the period of the second exposure pulse B2. When the light emission pulse L is used as a reference, the period of the fifth exposure pulse B21 and the period of the sixth exposure pulse B22 may overlap so that their starts coincide instead of their ends coincide.

[0125] [Modifications] Next, modifications of the present embodiment will be described. In the following modifications, an imaging device that performs the second or fourth example of the driving method described above will be described. In addition, in the following description of the modifications, differences from the present embodiment will be mainly described, and descriptions of commonalities will be omitted or simplified.

[0126] 12 is a functional block diagram showing an example of the configuration of an image pickup device 100A according to this modification. As shown in FIG. 12, the image pickup device 100A according to this modification is mainly different from the image pickup device 100 according to the embodiment in that it further includes a signal processing unit 50.

[0127] 12, the signal processing unit 50 is provided inside the solid-state imaging device 20. Note that the signal processing unit 50 may also be provided outside the solid-state imaging device 20.

[0128] The signal processing unit 50 generates a first differential signal representing a first signal value a1 or b1 based on the difference between the third exposure signal and the fourth exposure signal. The signal processing unit 50 generates the first differential signal, for example, by subtracting the AD-converted fourth exposure signal from the AD-converted third exposure signal. The signal processing unit 50 also generates a second differential signal representing a second signal value a2 or b2 based on the difference between the fifth exposure signal and the sixth exposure signal. The signal processing unit 50 generates the second differential signal, for example, by subtracting the AD-converted sixth exposure signal from the AD-converted fifth exposure signal. The signal processing unit 50 outputs the generated first differential signal and second differential signal to the distance calculation unit 40. The signal processing unit 50 may also generate the first differential signal and second differential signal using an analog signal before AD conversion.

[0129] The signal processing unit 50 is a processing circuit realized by, for example, a memory that stores a program and a processor that executes the program. The signal processing unit 50 may also be an analog circuit or a dedicated logic circuit that performs predetermined processing. Note that all or part of the drive control unit 30, distance calculation unit 40, and signal processing unit 50 may be configured using the same memory and processor.

[0130] (Others) While the imaging device and the driving method of the imaging device according to one or more aspects of the present disclosure have been described above based on the embodiments and modifications, the present disclosure is not limited to the embodiments. As long as they do not deviate from the spirit of the present disclosure, various modifications that a person skilled in the art can conceive of to each embodiment, or configurations constructed by combining components of different embodiments and modifications, may also be included within the scope of one or more aspects of the present disclosure.

[0131] For example, in the above-described embodiment and modified example, the imaging devices 100 and 100A include the light source 10, but this is not limiting. The imaging devices 100 and 100A may use an external light source without including the light source 10. In this case, a light emission control signal may be output to the external light source from the drive control unit 30, or a light emission control signal may be output from an external control unit.

[0132] Furthermore, for example, in the above-described embodiment and modified example, the image capturing devices 100 and 100A include the distance calculation unit 40, but this is not limiting. The image capturing devices 100 and 100A may not include the distance calculation unit 40, but may be devices that output a signal for calculating the distance to an object.

[0133] Furthermore, for example, in the above-described embodiment and modified example, the exposure period of the pixel 22 is defined by applying each exposure pulse as a transfer control signal TG to the gate of the transfer transistor 24, but this is not limited thereto. As long as the pixel 22 can output a signal based on the charge converted by the photoelectric conversion unit 23 during the exposure period, there are no particular limitations on how the pixel 22 is driven to define the exposure period. For example, the exposure period of the pixel 22 may start by switching the charge discharging transistor 26 from on to off while the transfer transistor 24 remains off. In this case, the exposure period of the pixel 22 ends when the transfer transistor 24 switches from off to on after the start of the exposure period, and the transfer transistor 24 switches off again.

[0134] In the above-described embodiment and modifications, each component may be realized by executing a software program suitable for that component, or by a program execution unit such as a processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0135] Furthermore, each component may be realized by hardware. Each component may be a circuit (or integrated circuit). These circuits may form a single circuit as a whole, or each may be a separate circuit. Furthermore, each of these circuits may be a general-purpose circuit or a dedicated circuit.

[0136] Furthermore, the general or specific aspects of the present disclosure may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, a computer program product, or a computer-readable recording medium such as a CD-ROM, or as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, a computer program product, and a recording medium.

[0137] For example, the present disclosure may be realized as an imaging device according to the above-described embodiment or modified example, as a control device that controls an imaging device, as a driving method for an imaging device that includes the steps (processing) described as the operation of the above-described imaging device, as a program for causing a computer to execute such a driving method for an imaging device, or as a computer-readable non-transitory recording medium on which such a program is recorded.

[0138] Below, examples of the imaging device and the driving method of the imaging device according to the present disclosure described based on the above embodiment and modified examples are shown. The imaging device and the driving method of the imaging device according to the present disclosure are not limited to the following examples.

[0139] For example, an imaging device according to a first aspect of the present disclosure includes: a plurality of pixels arranged in a matrix, each of the plurality of pixels having a photoelectric conversion unit that converts incident light into an electric charge and generates a signal based on the electric charge; and a drive control unit that exposes the plurality of pixels to light at a timing based on emission of pulsed light by a light source to an object, in each of one or more frames, wherein the drive control unit exposes the plurality of pixels so that the plurality of pixels generate one or more first signals representing first signal values ​​corresponding to the electric charges converted by the photoelectric conversion unit in a first period that starts at a timing based on emission of the pulsed light by the light source, and one or more second signals representing second signal values ​​corresponding to the electric charges converted by the photoelectric conversion unit in a second period that starts at a timing based on emission of the pulsed light by the light source, the second period starts at a predetermined time difference from the start of the first period, based on emission of the pulsed light by the light source, and the lengths of the first period and the second period are equal to each other and shorter than a pulse width of the pulsed light.

[0140] As a result, the multiple pixels generate one or more first signals representing first signal values ​​corresponding to the charges generated in the first period and one or more second signals representing second signal values ​​corresponding to the charges generated in the second period. Here, the lengths of the first period and the second period are shorter than the pulse width of the pulsed light. Therefore, it is possible to reduce the charges generated based on multipath light in the first period and the second period, and to reduce the multipath light components in the first signal value and the second signal value. Therefore, the imaging device according to this aspect can acquire signal values ​​in which the influence of multipath light is reduced.

[0141] Also, for example, an imaging device according to a second aspect of the present disclosure is the imaging device according to the first aspect, wherein the predetermined time difference is equal to the pulse width of the pulsed light.

[0142] As a result, the ratio between the first signal value and the second signal value corresponds to the delay time between the emission of pulsed light from the light source and the incidence of reflected light on the pixel, which allows the distance to the object to be calculated from the ratio between the first signal value and the second signal value, thereby simplifying the calculation required to calculate the distance to the object.

[0143] Also, for example, an imaging device according to a third aspect of the present disclosure is the imaging device according to the first aspect, wherein the predetermined time difference is shorter than the length of the first period and the length of the second period.

[0144] This causes the first period and the second period to overlap. Therefore, the time until both the first period and the second period end is shortened based on the emission of pulsed light from the light source, and multipath light that enters the pixel later than reflected light is less likely to enter the pixel during the first period and the second period. Therefore, the multipath light component in the first signal value and the second signal value can be further reduced.

[0145] Also, for example, an imaging device according to a fourth aspect of the present disclosure is the imaging device according to the third aspect, in which the predetermined time difference is equal to or less than half the length of the first period and the length of the second period.

[0146] This allows the distance measurement range to be extended.

[0147] Also, for example, an imaging device according to a fifth aspect of the present disclosure is an imaging device according to any one of the first to fourth aspects, wherein the drive control unit exposes each of one or more pixels of the plurality of pixels during the first period, causing each of the one or more pixels to generate a first exposure signal as the one or more first signals, and exposes each of one or more pixels of the plurality of pixels during the second period, causing each of the one or more pixels to generate a second exposure signal as the one or more second signals.

[0148] This allows the first exposure signal to be used as a signal representing the first signal value, and the second exposure signal to be used as a signal representing the second signal value, thereby simplifying the calculation required to calculate the distance to the object.

[0149] Also, for example, an imaging device according to a sixth aspect of the present disclosure is the imaging device according to the fifth aspect, wherein the plurality of pixels includes a first pixel, and the drive control unit exposes the first pixel for the first period in a first frame to cause the first pixel to generate the first exposure signal, and exposes the first pixel for the second period in a second frame to cause the first pixel to generate the second exposure signal.

[0150] This allows the first exposure signal and the second exposure signal to be generated in the pixel without reducing the resolution.

[0151] Also, for example, an imaging device according to a seventh aspect of the present disclosure is the imaging device according to the fifth aspect, wherein the plurality of pixels include a first pixel and a second pixel, and the drive control unit exposes the first pixel during the first period in the same frame to cause the first pixel to generate the first exposure signal, and exposes the second pixel during the second period to cause the second pixel to generate the second exposure signal.

[0152] This reduces the time required for the pixels to generate the first exposure signal and the second exposure signal.

[0153] Furthermore, for example, an imaging device according to an eighth aspect of the present disclosure is the imaging device according to any one of the first to fourth aspects, wherein the drive control unit exposes each of one or more pixels of the plurality of pixels for a third period starting at a timing based on emission of the pulsed light by the light source, and causes each of the one or more pixels to generate a third exposure signal as one of the one or more first signals; exposes each of the one or more pixels of the plurality of pixels for a fourth period starting at a timing based on emission of the pulsed light by the light source and shorter than the third period, and causes each of the one or more pixels to generate a fourth exposure signal as another one of the one or more first signals; and exposes each of the one or more pixels of the plurality of pixels for a fifth period starting at a timing based on emission of the pulsed light by the light source. and causing each of the one or more pixels to generate a fifth exposure signal as one of the one or more second signals, starting at a timing based on the emission of the pulsed light by the light source, and exposing each of the one or more pixels of the plurality of pixels for a sixth period that is shorter than the fifth period, and causing each of the one or more pixels to generate a sixth exposure signal as another one of the one or more second signals, wherein, when the emission of the pulsed light by the light source is used as a reference, the third period and the fourth period overlap so that either their starts or their ends coincide, and the period during which the third period and the fourth period do not overlap is the same as the first period, and the fifth period and the sixth period overlap so that either their starts or their ends coincide, and the period during which the fifth period and the sixth period do not overlap is the same as the second period.

[0154] This allows the period during which the pixels are exposed to light to be longer than the first and second periods. To generate a signal that instructs the pixels to perform short-term exposure, it is necessary to increase the circuit scale for supplying the signal to the pixels. In this embodiment, the period during which the pixels are exposed can be extended, thereby suppressing the increase in the circuit scale.

[0155] Also, for example, an imaging device according to a ninth aspect of the present disclosure is the imaging device according to the eighth aspect, wherein the plurality of pixels include a first pixel, and the drive control unit exposes the first pixel during the third period in a first frame to cause the first pixel to generate the third exposure signal, exposes the first pixel during the fourth period in a second frame to cause the first pixel to generate the fourth exposure signal, exposes the first pixel during the fifth period in a third frame to cause the first pixel to generate the fifth exposure signal, and exposes the first pixel during the sixth period in a fourth frame to cause the first pixel to generate the sixth exposure signal.

[0156] This allows the third exposure signal, the fourth exposure signal, the fifth exposure signal, and the sixth exposure signal to be generated in the pixel without reducing the resolution.

[0157] Also, for example, an imaging device according to a tenth aspect of the present disclosure is the imaging device according to the eighth aspect, wherein the plurality of pixels include a first pixel, a second pixel, a third pixel, and a fourth pixel, and the drive control unit, in the same frame, exposes the first pixel during the third period to cause the first pixel to generate the third exposure signal, exposes the second pixel during the fourth period to cause the second pixel to generate the fourth exposure signal, exposes the third pixel during the fifth period to cause the third pixel to generate the fifth exposure signal, and exposes the fourth pixel during the sixth period to cause the fourth pixel to generate the sixth exposure signal.

[0158] This reduces the time required for the pixels to generate the third exposure signal, the fourth exposure signal, the fifth exposure signal, and the sixth exposure signal.

[0159] Also, for example, an imaging device according to an eleventh aspect of the present disclosure is an imaging device according to any one of the eighth to tenth aspects, further comprising a signal processing unit that generates a first differential signal representing the first signal value based on the difference between the third exposure signal and the fourth exposure signal, and generates a second differential signal representing the second signal value based on the difference between the fifth exposure signal and the sixth exposure signal.

[0160] This allows the first differential signal and the second differential signal to be used to calculate the distance to the object.

[0161] Also, for example, an imaging device according to a twelfth aspect of the present disclosure is an imaging device according to any one of the first to eleventh aspects, further comprising a distance calculation unit that calculates a distance to the object based on the one or more first signals and the one or more second signals.

[0162] This allows the imaging device to output the distance to the object.

[0163] Furthermore, for example, a driving method according to a thirteenth aspect of the present disclosure is a driving method for an imaging device including a plurality of pixels arranged in a matrix, each of the plurality of pixels having a photoelectric conversion unit that converts incident light into electric charges, and a plurality of pixels that generate signals based on the electric charges, the driving method including exposing the plurality of pixels to light at a timing based on emission of pulsed light by a light source to an object, in each of one or more frames, wherein exposing the plurality of pixels to light so that the plurality of pixels generate one or more first signals representing first signal values ​​corresponding to the electric charges converted by the photoelectric conversion unit in a first period that starts at a timing based on the emission of the pulsed light by the light source, and one or more second signals representing second signal values ​​corresponding to the electric charges converted by the photoelectric conversion unit in a second period that starts at a timing based on the emission of the pulsed light by the light source, the second period starting with a predetermined time difference from the start of the first period, and lengths of the first period and the second period being equal to each other and shorter than a pulse width of the pulsed light.

[0164] As a result, the driving method according to this aspect can acquire signal values ​​in which the influence of multipath light is reduced, similar to the imaging device according to the first aspect.

[0165] The present disclosure can be used as an imaging device for obtaining a distance image of an object, and can be used in various applications such as an endoscope system.

[0166] REFERENCE SIGNS LIST 10 Light source 20 Solid-state imaging element 21 Pixel array 22 Pixel 23 Photoelectric conversion section 24 Transfer transistor 25 Charge storage section 26 Charge discharge transistor 27 Source follower transistor 28 Selection transistor 29 Reset transistor 30 Drive control section 40 Distance calculation section 50 Signal processing section 100, 100A Imaging device A1, B1 First exposure pulse A2, B2 Second exposure pulse A11, B11 Third exposure pulse A12, B12 Fourth exposure pulse A21, B21 Fifth exposure pulse A22, B22 Sixth exposure pulse BL Bit line MP Multi-path light RL Reflected light

Claims

1. An imaging device comprising: a plurality of pixels arranged in a matrix, each of the plurality of pixels having a photoelectric conversion unit that converts incident light into an electric charge and generating a signal based on the electric charge; and a drive control unit that exposes the plurality of pixels to light at a timing based on the emission of pulsed light by a light source to an object in each of one or more frames, wherein the drive control unit exposes the plurality of pixels so that the plurality of pixels generate one or more first signals for representing a first signal value corresponding to the electric charge converted by the photoelectric conversion unit in a first period starting at a timing based on the emission of the pulsed light by the light source, and one or more second signals for representing a second signal value corresponding to the electric charge converted by the photoelectric conversion unit in a second period starting at a timing based on the emission of the pulsed light by the light source, wherein the second period starts at a predetermined time difference from the start of the first period, based on the emission of the pulsed light by the light source, and the lengths of the first and second periods are equal to each other and shorter than the pulse width of the pulsed light.

2. The imaging device according to claim 1, wherein the predetermined time difference is equal to the pulse width of the pulsed light.

3. The imaging device according to claim 1, wherein the predetermined time difference is shorter than the length of the first period and the length of the second period.

4. The imaging device according to claim 3, wherein the predetermined time difference is equal to or less than half the length of the first period and the length of the second period.

5. An imaging device as described in any one of claims 1 to 4, wherein the drive control unit exposes each of one or more pixels of the plurality of pixels during the first period, causing each of the one or more pixels to generate a first exposure signal as the one or more first signals, and exposes each of one or more pixels of the plurality of pixels during the second period, causing each of the one or more pixels to generate a second exposure signal as the one or more second signals.

6. The imaging device of claim 5, wherein the plurality of pixels includes a first pixel, and the drive control unit exposes the first pixel during the first period in a first frame, causing the first pixel to generate the first exposure signal, and exposes the first pixel during the second period in a second frame, causing the first pixel to generate the second exposure signal.

7. The imaging device of claim 5, wherein the plurality of pixels include a first pixel and a second pixel, and the drive control unit, in a same frame, exposes the first pixel during the first period to cause the first pixel to generate the first exposure signal, and exposes the second pixel during the second period to cause the second pixel to generate the second exposure signal.

8. The drive control unit: exposes each of one or more pixels of the plurality of pixels for a third period starting with a timing based on the emission of the pulsed light by the light source, and causes each of the one or more pixels to generate a third exposure signal as one of the one or more first signals; exposes each of one or more pixels of the plurality of pixels for a fourth period starting with a timing based on the emission of the pulsed light by the light source and shorter than the third period, and causes each of the one or more pixels to generate a fourth exposure signal as another of the one or more first signals; exposes each of one or more pixels of the plurality of pixels for a fifth period starting with a timing based on the emission of the pulsed light by the light source, and causes each of the one or more pixels to generate a fifth exposure signal as one of the one or more second signals; exposes each of one or more pixels of the plurality of pixels for a sixth period starting with a timing based on the emission of the pulsed light by the light source and shorter than the fifth period, and causes each of the one or more pixels to generate a sixth exposure signal as another of the one or more second signals; 5. The imaging device of claim 1, wherein, when the emission of the pulsed light by the light source is used as a reference, the third period and the fourth period overlap such that either their starts or their ends coincide with each other, and a period in which the third period and the fourth period do not overlap is the same as the first period, and the fifth period and the sixth period overlap such that either their starts or their ends coincide with each other, and a period in which the fifth period and the sixth period do not overlap is the same as the second period.

9. The imaging device of claim 8, wherein the plurality of pixels include a first pixel, and the drive control unit: in a first frame, exposes the first pixel during the third period to cause the first pixel to generate the third exposure signal; in a second frame, exposes the first pixel during the fourth period to cause the first pixel to generate the fourth exposure signal; in a third frame, exposes the first pixel during the fifth period to cause the first pixel to generate the fifth exposure signal; and in a fourth frame, exposes the first pixel during the sixth period to cause the first pixel to generate the sixth exposure signal.

10. The imaging device of claim 8, wherein the plurality of pixels include a first pixel, a second pixel, a third pixel, and a fourth pixel, and the drive control unit, in the same frame, exposes the first pixel during the third period, causing the first pixel to generate the third exposure signal, exposes the second pixel during the fourth period, causing the second pixel to generate the fourth exposure signal, exposes the third pixel during the fifth period, causing the third pixel to generate the fifth exposure signal, and exposes the fourth pixel during the sixth period, causing the fourth pixel to generate the sixth exposure signal.

11. An imaging device as described in any one of claims 8 to 10, further comprising a signal processing unit that generates a first differential signal representing the first signal value based on the difference between the third exposure signal and the fourth exposure signal, and generates a second differential signal representing the second signal value based on the difference between the fifth exposure signal and the sixth exposure signal.

12. The imaging device according to any one of claims 1 to 11, further comprising a distance calculation unit that calculates a distance to the object based on the one or more first signals and the one or more second signals.

13. A method for driving an imaging device including a plurality of pixels arranged in a matrix, each of the plurality of pixels having a photoelectric conversion unit that converts incident light into an electric charge and a plurality of pixels that generate a signal based on the electric charge, the method including exposing the plurality of pixels to light at a timing based on emission of pulsed light by a light source to an object in each of one or more frames, wherein exposing the plurality of pixels to light such that the plurality of pixels generate one or more first signals representing a first signal value corresponding to the electric charge converted by the photoelectric conversion unit in a first period starting at a timing based on the emission of the pulsed light by the light source, and one or more second signals representing a second signal value corresponding to the electric charge converted by the photoelectric conversion unit in a second period starting at a timing based on the emission of the pulsed light by the light source, the second period starting with a predetermined time difference from the start of the first period, and the lengths of the first period and the second period being equal to each other and shorter than the pulse width of the pulsed light.

Images