Image sensing device and driving method thereof

Abstract

To provide an image sensing device capable of removing a noise generated when a distance information signal is generated, and an operation method thereof.SOLUTION: A unit pixel comprises a first pixel TAPA, a second pixel TAPB, and an equalization circuit EQ. A first sensing circuit P1 generates a first electric charge corresponding to a light signal on the basis of a first control signal MIXA. A second sensing circuit P2 generates a second electric charge corresponding to the light signal on the basis of a second control signal MIXB. The equalization circuit EQ equalizes noises generated in a plurality of pixels when the unit pixel performs a reset operation. A first transmission circuit TT1 transmits the first electric charge to a first electric charge storage circuit C1 on the basis of the transmission signal TX. A second transmission circuit TT2 transmits a second electric charge to a second electric charge storage circuit C2 on the basis of the transmission signal TX. An image processor cancels a reset noise on the basis of a first pixel signal PX1 and a second pixel signal PX2.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to semiconductor design technology, and more particularly to an image sensing device and method of operation thereof. [Background technology]

[0002] An image sensing device is a device that captures images using the properties of semiconductors that react to light. Image sensing devices can be broadly divided into image sensing devices that use a CCD (Charge Coupled Device) and image sensing devices that use a CMOS (Complementary Metal Oxide Semiconductor). In recent years, image sensing devices that use CMOS have become increasingly popular due to their advantage of being able to directly implement analog and digital control circuits on a single integrated circuit (IC). Summary of the Invention [Problem to be solved by the invention]

[0003] SUMMARY OF THE INVENTION Embodiments of the present invention provide an image sensing device and an operating method thereof that can eliminate (ie, cancel) noise that occurs when generating a depth information signal. [Means for solving the problem]

[0004] According to one aspect of the present invention, an image sensing device may include at least one unit pixel including a plurality of pixels for generating a plurality of pixel signals based on a plurality of control signals having different phases from each other, and an equalization circuit for equalizing noise generated in the plurality of pixels during a reset operation of the unit pixel.

[0005] The reset operation may include resetting a plurality of charge storage circuits provided in each of the plurality of pixels.

[0006] The equalization circuit may be commonly connected to the plurality of pixels.

[0007] The image sensing device may further include an image processor for processing the plurality of pixel signals through a subtraction operation.

[0008] According to another aspect of the present invention, an image sensing device may include: a first pixel including a first charge storage circuit, a first reset circuit for resetting the first charge storage circuit during a reset interval, and a first sensing circuit for transferring a first charge to the first charge storage circuit corresponding to a first control signal having a first phase during a transfer interval; a second pixel including a second charge storage circuit, a second reset circuit for resetting the second charge storage circuit during the reset interval, and a second sensing circuit for transferring a second charge to the second charge storage circuit corresponding to a second control signal having a second phase during the transfer interval; and an equalization circuit commonly connected to a first node between the first reset circuit and the first sensing circuit and a second node between the second reset circuit and the second sensing circuit.

[0009] The equalization circuit can electrically connect the first node and the second node during the reset interval, and electrically isolate the first node and the second node during the transmission interval.

[0010] The image sensing device may further include an image processor for subtracting first and second pixel signals generated from the first and second pixels, respectively, during a readout period.

[0011] The first pixel may further include a first selection circuit for generating a first pixel signal corresponding to the first charge during a readout interval, and the second pixel may further include a second selection circuit for generating a second pixel signal corresponding to the second charge during the readout interval.

[0012] According to yet another aspect of the present invention, a method for driving an image sensing device may include the steps of equalizing noise generated by first and second reset circuits provided in first and second pixels, respectively, based on a reset signal and an equalization signal; storing a first charge generated by a first sensing circuit provided in the first pixel in a first charge storage circuit provided in the first pixel based on a first control signal having a first phase and storing a second charge generated by a second sensing circuit provided in the second pixel in a second charge storage circuit provided in the second pixel based on a second control signal having a second phase; reading first and second pixel signals from the first and second pixels, respectively, corresponding to the first and second charges stored in the first and second charge storage circuits, based on a transfer signal; and generating a distance information signal in which the noise has been canceled out, based on the first and second pixel signals.

[0013] The step of generating the distance information signal can generate the distance information signal by subtracting the first and second pixel signals.

[0014] The equalization signal may be deactivated later than the reset signal.

[0015] The first control signal and the second control signal may have a phase difference of 180 degrees.

[0016] According to yet another aspect of the present invention, an image sensing device can include first and second pixels that alternately generate first and second pixel signals and generate first and second noises, respectively, when reset; an equalization circuit that equalizes the first and second noises by connecting the first and second pixels to each other when the first and second pixels are reset; and an image processor that performs subtraction processing on the first and second pixel signals.

[0017] Other features and advantages of the present invention will be more clearly understood from the following detailed description and drawings. [Effects of the Invention]

[0018] The present invention has an advantage that the signal-to-noise ratio of the distance information signal can be improved by removing (i.e., canceling) noise generated when generating the distance information signal. The signal-to-noise ratio of the distance information signal can be expected to be more significantly improved as the distance to the subject increases or the brightness of the subject decreases.

[0019] Furthermore, the embodiment of the present invention has the advantage that noise can be removed by simply adding a simple circuit within the unit pixel, thereby minimizing area loss of the unit pixel. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a block diagram illustrating the configuration of an image sensing device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a circuit diagram of the unit pixel illustrated in FIG. 1. [Figure 3] 2 is a timing chart for explaining the operation of the image sensing device shown in FIG. 1; DETAILED DESCRIPTION OF THE INVENTION

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the technical concept of the present invention.

[0022] Throughout this specification, when a part is described as being "connected" to another part, this includes not only "directly connected" but also "electrically connected" via another element therebetween. Furthermore, when a part is described as "including" or "comprising" a certain component, this does not mean that other components are excluded, but means that the part can further include or be comprised of other components, unless otherwise specified to the contrary. Furthermore, even if some components are described in the singular throughout this specification, it will be understood that the present invention is not limited thereto, and that the component may consist of a plurality of components.

[0023] The drawings of the present invention are illustrative in nature and are intended to eliminate ambiguity in the features of the present invention and to simply illustrate the technical configuration of the present invention, and detailed descriptions may not be provided.

[0024] Furthermore, one embodiment of the present invention may be embodied in one or more features of other embodiments according to the technical concept of the present invention.

[0025] FIG. 1 is a block diagram illustrating an image sensing device according to an embodiment of the present invention.

[0026] 1, the image sensing device 100 can generate a distance information signal TOF_OUT representing the depth of an object 200 using a time of flight (TOF) method. For example, the image sensing device 100 can generate the distance information signal TOF_OUT by detecting a phase difference between a first optical signal MS output to the object 200 and a second optical signal RS reflected from the object 200. For example, the image sensing device 100 can include an optical transmitter 110, an optical receiver 120, a row controller 130, a phase controller 140, a pixel array 150, and an image processor 160.

[0027] The optical transmitter 110 can output a first optical signal MS to the object 200. For example, the optical signal MS can be a periodic signal that toggles periodically.

[0028] The optical receiver 120 may receive a second optical signal RS reflected from the object 200. For example, the optical receiver 120 may filter noise, such as ambient light, from the second optical signal RS and provide a third optical signal RS' corresponding to the first optical signal MS to the pixel array 150.

[0029] The row controller 130 can generate multiple row control signals CTRLs for row-by-row control of the pixel array 150. For example, the row controller 130 can generate a first row control signal for controlling pixels arranged in a first row of the pixel array 150, and can generate an nth row control signal for controlling pixels arranged in an nth row of the pixel array 150 (where "n" is a natural number greater than 2).

[0030] The phase controller 140 can generate first and second control signals MIXA and MIXB having different phases from each other. For example, the first and second control signals MIXA and MIXB can have a phase difference of 180 degrees. The first and second control signals MIXA and MIXB can have the same period as the first optical signal MS, but one of the first and second control signals MIXA and MIXB can have the same phase as the first optical signal MS.

[0031] The pixel array 150 can generate a plurality of pixel signals PXs based on the third optical signal RS', a plurality of low control signals CTRLs, and first and second control signals MIXA and MIXB. The pixel array 150 can include at least one unit pixel for measuring a distance to the object 200. For example, the unit pixel can be selected based on the plurality of low control signals CTRLs and can generate first and second pixel signals PX1 and PX2 based on the first and second control signals MIXA and MIXB and the third optical signal RS'. In particular, the unit pixel can be controlled to generate the first and second pixel signals PX1 and PX2 such that the same noise is reflected in the first and second pixel signals PX1 and PX2 when generating the first and second pixel signals PX1 and PX2. The unit pixel will be described in more detail with reference to FIG. 2.

[0032] The image processor 160 can generate a distance information signal TOF_OUT representing the distance to the object 200 based on the plurality of pixel signals PXs. For example, the image processor 160 can generate the distance information signal TOF_OUT by performing a subtraction process on the first and second pixel signals PX1 and PX2. In particular, when the subtraction process is performed, noises similarly reflected in the first and second pixel signals PX1 and PX2 can be canceled out.

[0033] FIG. 2 shows a circuit diagram of the unit pixel illustrated in FIG.

[0034] As shown in FIG. 2, the unit pixel may include a first pixel TAPA, a second pixel TAPB, and an equalizing circuit EQ (operatively connecting the first and second pixels TAPA, TAPB).

[0035] The first pixel TAPA can generate a first pixel signal PX1 based on a reset signal RX, a transfer signal TX, a selection signal SX, and a first control signal MIXA, where the reset signal RX, the transfer signal TX, and the selection signal SX can be signals included in the plurality of row control signals CTRLs.

[0036] For example, the first pixel TAPA may include a first sensing circuit P1, a first reset circuit RT1, a first transfer circuit TT1, a first charge storage circuit C1, a first drive circuit DT1, and a first selection circuit ST1. The first sensing circuit P1 may be connected between a first node N1 and a low voltage end. The first sensing circuit P1 may generate a first charge corresponding to a third optical signal RS' based on a first control signal MIXA. The first sensing circuit P1 may include a photodiode. The first reset circuit RT1 may be connected between a high voltage end and the first node N1. The first reset circuit RT1 may reset the first sensing circuit P1 and the first charge storage node C1 based on a reset signal RX. The first transfer circuit TT1 may be connected between the first node N1 and a first floating diffusion node FD1. The first transfer circuit TT1 may reset the first charge storage circuit C1 based on a transfer signal TX and transfer the first charge generated from the first sensing circuit P1 to the first charge storage circuit C1. The first charge storage circuit C1 may be connected between the first floating diffusion node FD1 and the low voltage end. The first charge storage circuit C1 may be a parasitic capacitor. The first drive circuit DT1 may be connected between the high voltage end and a first selection circuit ST1. The first drive circuit DT1 may drive the first column line COL1 with a high voltage supplied via the high voltage end based on the voltage applied to the first floating diffusion node FD1. The first selection circuit ST1 may be connected between the first drive circuit DT1 and the first column line COL1. The first selection circuit ST1 may selectively connect the first drive circuit DT1 and the first column line COL1 based on a selection signal SX.

[0037] The second pixel TAPB can generate a second pixel signal PX2 based on the reset signal RX, the transmission signal TX, the selection signal SX, and the second control signal MIXB.

[0038] For example, the second pixel TAPB may include a second sensing circuit P2, a second reset circuit RT2, a second transfer circuit TT2, a second charge storage circuit C2, a second drive circuit DT2, and a second selection circuit ST2. The second sensing circuit P2 may be connected between the second node N2 and the low voltage end. The second sensing circuit P2 may generate a second charge corresponding to a third optical signal RS' based on a second control signal MIXB. The second sensing circuit P2 may include a photodiode. The second reset circuit RT2 may be connected between the high voltage end and the second node N2. The second reset circuit RT2 may reset the second sensing circuit P2 and the second charge storage node C2 based on a reset signal RX. The second transfer circuit TT2 may be connected between the second node N2 and a second floating diffusion node FD2. The second transfer circuit TT2 may reset the second charge storage circuit C2 based on a transfer signal TX and transfer the second charge generated from the second sensing circuit P2 to the second charge storage circuit C2. The second charge storage circuit C2 may be connected between the second floating diffusion node FD2 and the low voltage end. The second charge storage circuit C2 may be a parasitic capacitor. The second drive circuit DT2 may be connected between the high voltage end and a second selection circuit ST2. The second drive circuit DT2 may drive the second column line COL2 with a high voltage supplied via the high voltage end based on the voltage applied to the second floating diffusion node FD2. The second selection circuit ST2 may be connected between the second drive circuit DT2 and the second column line COL2. The second selection circuit ST2 may selectively connect the second drive circuit DT2 and the second column line COL2 based on a selection signal SX.

[0039] The equalization circuit EQ may be commonly connected to the first pixel TAPA and the second pixel TAPB. For example, the equalization circuit EQ may include a MOS transistor located between the first pixel TAPA and the second pixel TAPB. The MOS transistor may receive an equalization signal RXS at its gate terminal and have a source terminal and a drain terminal connected between a first node N1 and a second node N2. The equalization circuit EQ may selectively connect the first node N1 and the second node N2 based on the equalization signal RXS. For example, the equalization circuit EQ may electrically connect the first node N1 and the second node N2 when the equalization signal RXS is activated, and electrically separate the first node N1 and the second node N2 when the equalization signal RXS is deactivated. The equalization circuit EQ may equalize noise generated in the first and second pixels TAPA and TAPB by electrically connecting the first node N1 and the second node N2. For example, the equalization circuit EQ can equalize noise generated in the first and second pixels TAPA and TAPB during a reset operation of the unit pixel. The reset operation can be performed during a period in which a reset signal RX is activated. That is, the reset operation can be performed during a period in which a first reset circuit RT1 provided in the first pixel TAPA and a second reset circuit RT2 provided in the second pixel TAPB are enabled.

[0040] Hereinafter, the operation of the image sensing device 100 according to the embodiment of the present invention having the above-described configuration will be described.

[0041] FIG. 3 shows a timing diagram illustrating the operation of the image sensing device 100 according to the embodiment of the present invention.

[0042] 3, the first pixel TAPA and the second pixel TAPB may perform a reset operation during a reset period AA based on a reset signal RX and a transfer signal TX. For example, the first sensing circuit P1 included in the first pixel TAPA may be reset during an interval in which the reset signal RX is activated, and the first charge storage circuit C1 included in the first pixel TAPA may be reset during an interval in which the transfer signal TX is activated. In the embodiment of the present invention, the reset signal RX and the transfer signal TX are activated at the same time point, but this is not necessarily limited thereto. The reset signal RX and the transfer signal TX may be activated at different times.

[0043] The equalization circuit EQ can equalize noise generated by the first and second reset circuits RT1 and RT2 provided in the first and second pixels TAPA and TAPB, respectively, during the reset period AA based on the reset signal RX and the equalization signal RXS. The noise equalized by the equalization circuit EQ can be obtained by equalizing noise generated when the first reset circuit RT1 is turned off and noise generated when the second reset circuit RT2 is turned off. The equalized noise can be commonly reflected in the first and second charge storage circuits C1 and C2. To this end, the inactivation point of the equalization signal RXS is preferably later than the inactivation point of the reset signal RX. Therefore, the same reset noise can be applied to the first floating diffusion node FD1 and the second floating diffusion node FD2 during the reset period AA.

[0044] The first pixel TAPA may generate and store the first charge during a transmission interval BB based on a transmission signal TX, a first control signal MIXA, and a third optical signal RS'. For example, the first sensing circuit P1 may generate the first charge based on the first control signal MIXA and the third optical signal RS', and the first transmission circuit TT1 may transmit the first charge to the first charge storage circuit C1 based on the transmission signal TX. The second pixel TAPB may generate and store the second charge during a transmission interval BB based on the transmission signal TX and a second control signal MIXB. For example, the second sensing circuit P2 may generate the second charge based on the second control signal MIXB and the third optical signal RS', and the second transmission circuit TT2 may transmit the second charge to the second charge storage circuit C2 based on the transmission signal TX. The first control signal MIXA and the second control signal MIXB may have a phase difference of 180 degrees.

[0045] The first pixel TAPA can read out a first pixel signal PX1 corresponding to the first charge to the image processor 160 during the readout period CC based on the selection signal SX. For example, the first selection circuit ST1 can electrically connect the first driving circuit DT1 to the first column line COL1 based on the selection signal SX, and the first driving circuit DT1 can generate the first pixel signal PX1 by driving the first column line COL1 with the high voltage based on the voltage applied to the first floating diffusion node FD1. At this time, the first pixel signal PX1 can include the reset noise generated during the reset period AA. The second pixel TAPB can read out a second pixel signal PX2 corresponding to the second charge to the image processor 160 during the readout period CC based on the selection signal SX. For example, the second selection circuit ST2 may electrically connect the second driving circuit DT2 to the second column line COL2 based on the selection signal SX, and the second driving circuit DT2 may drive the second column line COL2 with the high voltage based on the voltage applied to the second floating diffusion node FD2 to generate the second pixel signal PX2. In this case, the second pixel signal PX2 may include the reset noise generated in the reset period AA.

[0046] The image processor 160 can generate a distance information signal TOF_OUT in which the reset noise has been cancelled based on the first and second pixel signals PX1 and PX2. For example, the image processor 160 can generate the distance information signal TOF_OUT by performing a subtraction process on the first and second pixel signals PX1 and PX2. In particular, the image processor 160 can cancel out the reset noise commonly included in the first and second pixel signals PX1 and PX2 by performing a subtraction process on the first and second pixel signals PX1 and PX2.

[0047] According to this embodiment of the present invention, there is an advantage that the noise generated in the first and second pixels can be equalized, thereby canceling out the noise when generating a distance information signal.

[0048] Although the technical concept of the present invention has been specifically described by the above-described embodiments, it should be noted that the above-described embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, those skilled in the art will understand that various embodiments are possible through various substitutions, modifications, and alterations within the scope of the technical concept of the present invention. [Explanation of symbols]

[0049] 100 Image sensing device 110 Light Transmitter 120 Optical Receiver 130 Low Controller 140 Phase Controller 150 pixel array 160 Image Processor

Claims

1. At least one unit pixel including a plurality of pixels for generating a plurality of pixel signals based on a plurality of control signals having different phases from each other; At least one equalization circuit that performs an equalization operation to equalize noise generated in the plurality of pixels while the unit pixel performs a reset operation; Equipped with An image sensing device, wherein an equalization interval in which the equalization operation is performed at least partially overlaps with a reset interval in which the reset operation is performed, and the equalization interval ends later than the reset interval.

2. The image sensing device of claim 1 , wherein the reset operation includes resetting a plurality of charge storage circuits provided in each of the plurality of pixels.

3. The image sensing device according to claim 1 , wherein the equalization circuit is commonly connected to the plurality of pixels.

4. The image sensing device of claim 1 , further comprising an image processor for processing the plurality of pixel signals via a subtraction operation.

5. a first pixel including: a first charge storage circuit that stores a first charge during a transfer interval; a first sensing circuit that generates the first charge based on a first control signal having a first phase during the transfer interval; and a first reset circuit that resets the first charge storage circuit and the first sensing circuit during a reset interval; a second pixel including: a second charge storage circuit that stores a second charge during the transfer interval; a second sensing circuit that generates the second charge based on a second control signal having a second phase during the transfer interval; and a second reset circuit that resets the second charge storage circuit and the second sensing circuit during the reset interval; an equalization circuit connected in common to a first node between the first reset circuit and the first sensing circuit and a second node between the second reset circuit and the second sensing circuit; An image sensing device comprising:

6. 6. The image sensing device of claim 5, wherein the equalization circuit electrically connects the first node and the second node during the reset period and electrically isolates the first node and the second node during the transfer period.

7. The image sensing device according to claim 5 , further comprising an image processor for subtracting first and second pixel signals generated from the first and second pixels, respectively, during a readout period.

8. the first pixel further comprises a first selection circuit for generating a first pixel signal corresponding to the first charge during a readout interval; The image sensing device of claim 5 , wherein the second pixel further comprises a second selection circuit for generating a second pixel signal corresponding to the second charge during the readout period.

9. A step of equalizing noise generated by first and second reset circuits provided in the first and second pixels, respectively, based on a reset signal and an equalization signal; storing a first charge generated by a first sensing circuit included in the first pixel based on a first control signal having a first phase in a first charge storage circuit included in the first pixel; storing a second charge generated by a second sensing circuit included in the second pixel based on a second control signal having a second phase in a second charge storage circuit included in the second pixel; reading out first and second pixel signals from the first and second pixels, respectively, corresponding to the first and second charges stored in the first and second charge storage circuits, based on a selection signal; generating a distance information signal in which the noise has been cancelled based on the first and second pixel signals; A driving method for an image sensing device comprising:

10. 10. The method of driving an image sensing device according to claim 9, wherein the step of generating the distance information signal generates the distance information signal by subtracting the first and second pixel signals.

11. 10. The method of claim 9, wherein the equalization signal is deactivated later than the reset signal.

12. The method for driving an image sensing device according to claim 9 , wherein the first control signal and the second control signal have a phase difference of 180 degrees.

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