Time of flight sensing system, image sensor

Abstract

The present invention may provide an image sensor mounted on a Time-of-Flight (TOF) sensing system, comprising a pixel array that generates a charge corresponding to received light and includes a plurality of pixels arranged according to a plurality of rows and a plurality of columns, and a first driving unit that supplies a control signal to a plurality of pixels through a plurality of columns, wherein the first driving unit can supply a control signal to one of an odd column and an even column among a plurality of columns.

Description

Technology Field

[0001] The present invention relates to a Time of Flight (TOF) type sensing system, and more specifically, to a device for improving the resolution or precision of a sensing system. Background Technology

[0003] Time of Flight (TOF) is a method of calculating distance by measuring the flight time of light or signals, that is, the time it takes for light or signals to be emitted and reflected back from an object. A TOF camera is a camera that uses the TOF method to output an image containing information about the depth of an object based on the distance between the object and the camera. While conventional cameras output 2D images showing the color and shape of objects, TOF cameras can output 3D images showing not only the color and shape of objects but also their depth. The problem to be solved

[0005] Embodiments of the present invention provide a device capable of avoiding distortion of information obtained from each pixel due to a difference in distance between a pixel included in a pixel array within an image sensor used in a Time of Flight (TOF) sensing system and a driver driving the pixel array.

[0006] In addition, the present invention can provide a device that enables a driving voltage output from a driving unit to be transmitted in a sequence capable of compensating for the difference in distance between the driving unit and each pixel to a pixel array comprising a plurality of pixels arranged based on rows and columns within a Time-of-Flight (TOF) sensing system.

[0007] In addition, the present invention can provide a device in which a single driving unit supplies a driving voltage every two columns so as to compensate for differences in operation between pixels caused by delays, resistance, etc., that occur during the process of transmitting the driving voltage output from the driving unit as the size of the image sensor included in the Time-of-Flight (TOF) sensing system increases.

[0008] The technical problems to be solved by the present invention are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which the present invention belongs from the description below. means of solving the problem

[0010] The present invention provides a Time of Flight (TOF) sensing system and an image sensor.

[0011] An image sensor mounted on a Time-of-Flight (TOF) sensing system according to embodiments of the present invention generates a charge corresponding to received light and includes a pixel array comprising a plurality of pixels arranged according to a plurality of rows and a plurality of columns; and a first driving unit that supplies a control signal to the plurality of pixels through the plurality of columns, wherein the first driving unit can supply the control signal to one of an odd column and an even column among the plurality of columns.

[0012] In addition, when the first driving unit supplies the control signal to one end of the odd-numbered column, the other end of the odd-numbered column and one end of the even-numbered column may be connected, or when the first driving unit supplies the control signal to one end of the even-numbered column, the other end of the even-numbered column and one end of the odd-numbered column may be connected.

[0013] Additionally, the image sensor may further include a second driving unit that supplies the control signal to the other of the odd and even columns among the plurality of columns.

[0014] In addition, the first driving unit and the second driving unit may be positioned on opposite sides with respect to the pixel array.

[0015] In addition, the distance between each of the first driving unit and the second driving unit and the pixel array may be the same.

[0016] Additionally, the pixel includes one or more diodes and a number of transfer gates equal to the number of diodes, and the control signal can be supplied to the transfer gates.

[0017] Additionally, the pixel may include a first receiver that detects the received light in a first phase; and a second receiver that detects the received light in a second phase opposite to the first phase.

[0018] An image sensor mounted on a time-of-flight (TOF) sensing system according to other embodiments of the present invention may include: a pixel array comprising a plurality of pixels arranged according to a plurality of rows and a plurality of columns that generate a charge corresponding to received light; a first driving unit that supplies a first control signal through some of the plurality of columns; and a second driving unit that supplies a second control signal through a column among the plurality of columns to which the first control signal is not supplied.

[0019] Additionally, if the first control signal is transmitted through an odd column among the plurality of columns, the second control signal is transmitted through an even column among the plurality of columns, and if the first control signal is transmitted through an even column, the second control signal can be transmitted through an odd column.

[0020] In addition, the first control signal and the second control signal may be supplied alternately to the plurality of columns.

[0021] In addition, the first driving unit and the second driving unit may be positioned on opposite sides with respect to the pixel array.

[0022] Additionally, the pixel includes one or more diodes and a number of transfer gates equal to the number of diodes, and the control signal can be supplied to the transfer gates.

[0023] In addition, the image sensor may further include a signal converter that converts the charge information output from the pixel array into a digital signal.

[0024] A sensing system of the Time of Flight (TOF) method according to other embodiments of the present invention comprises: a transmitter that outputs light having a preset phase; an image sensor that receives reflected light reflected from an object by the light; and a signal processing unit that determines the distance to the object through the relationship between the light and the reflected light, wherein the image sensor generates charge information corresponding to the reflected light and comprises a pixel array including a plurality of pixels arranged according to a plurality of rows and a plurality of columns; a first driving unit that supplies a control signal to the plurality of pixels through the plurality of columns; and a signal conversion unit that converts the charge information output from the pixel array into a digital signal and transmits it to the signal processing unit, wherein the first driving unit may supply the control signal to one of an odd column and an even column among the plurality of columns.

[0025] In addition, when the first driving unit supplies the control signal to one end of the odd-numbered column, the other end of the odd-numbered column and one end of the even-numbered column may be connected, or when the first driving unit supplies the control signal to one end of the even-numbered column, the other end of the even-numbered column and one end of the odd-numbered column may be connected.

[0026] In addition, the image sensor may further include a second driving unit that supplies the control signal to the other of the odd and even columns among the plurality of columns.

[0027] In addition, the first driving unit and the second driving unit may be positioned on opposite sides with respect to the pixel array.

[0028] In addition, the distance between each of the first driving unit and the second driving unit and the pixel array may be the same.

[0029] Additionally, the pixel includes one or more diodes and a number of transfer gates equal to the number of diodes, and the control signal can be supplied to the transfer gates.

[0030] Additionally, the pixel may include a first receiver that detects the received light in a first phase; and a second receiver that detects the received light in a second phase opposite to the first phase.

[0031] The above embodiments of the present invention are merely some of the preferred embodiments of the present invention, and various embodiments reflecting the technical features of the present invention can be derived and understood by those skilled in the art based on the detailed description of the present invention to be described below. Effects of the invention

[0033] The effects of the device according to the present invention are described as follows.

[0034] A Time of Flight (TOF) sensing system according to embodiments of the present invention has the advantage of being able to measure the distance to an object more accurately and generate a three-dimensional image representing the depth of the object.

[0035] In addition, the present invention can compensate for the delay in driving voltage that occurs according to the position of a pixel that generates charge based on light reflected from an object and received, based on the order in which the driving voltage is transmitted, thereby providing a device that can generate a 3D image more effectively and quickly than compensating for the delay in driving voltage through a separate algorithm or signal processing method.

[0036] The effects obtainable from the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description below. Brief explanation of the drawing

[0038] FIG. 1 illustrates the operation of a Time of Flight (TOF) sensing system according to one embodiment of the present invention. FIG. 2 illustrates embodiments according to the operation of a time-of-flight (TOF) sensing system according to one embodiment of the present invention. FIG. 3 illustrates a first example of a time-of-flight (TOF) sensing system according to one embodiment of the present invention. FIG. 4 illustrates a second example of a time-of-flight (TOF) sensing system according to one embodiment of the present invention. FIG. 5 illustrates an example of pixels included in an image sensor mounted on a time-of-flight (TOF) sensing system according to one embodiment of the present invention. FIG. 6 illustrates the operation of an image sensor mounted on a time-of-flight (TOF) sensing system according to one embodiment of the present invention. FIG. 7 illustrates a method for estimating distance and determining the magnitude of a modulation signal in a time-of-flight (TOF) sensing system according to an embodiment of the present invention. FIG. 8 illustrates the delay occurring during the operation of an image sensor mounted on a time-of-flight (TOF) sensing system according to one embodiment of the present invention. FIGS. 9a to 9d illustrate an example for improving the delay occurring during the operation of an image sensor mounted on a Time-of-Flight (TOF) sensing system according to one embodiment of the present invention. Figure 10 illustrates the result of improved delay through the example described in Figures 9a to 9d. Specific details for implementing the invention

[0039] Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the following description, only the parts necessary for understanding the operation according to the present invention will be described, and the description of other parts will be omitted so as not to obscure the essence of the present invention.

[0040] Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

[0041] FIG. 1 illustrates the operation of a Time of Flight (TOF) sensing system according to one embodiment of the present invention.

[0042] Referring to FIG. 1, a time-of-flight (TOF) sensing system (110) can measure the distance to a target (20). The time-of-flight (TOF) sensing system (110) may include a transmitter (110) that outputs a modulated signal to measure the distance to a target (20), and a receiver (120) that receives a reflected signal that is reflected back from the target (20) by the modulated signal.

[0043] A Time-of-Flight (TOF) sensing system (110) can be one of the most important elements in the development of automation in various industrial fields and consumer markets. A device used by consumers can recognize the surrounding environment or the location of the device in the surrounding environment through the Time-of-Flight (TOF) sensing system (110). A camera including the Time-of-Flight (TOF) sensing system (110) can provide 3D vision technology by determining the color, shape, and distance of objects included in a 3D environment.

[0044] When a modulated signal output by a transmitter (110) within a Time-of-Flight (TOF) sensing system (110) emits a preset pattern into the surrounding environment and a reflected signal reflected from various objects and targets in the surrounding environment is received through a receiver (120), the distance can be determined through the correlation between the modulated signal and the reflected signal.

[0045] Ambient light can be a hindrance in the process of observing the relationship between a modulated signal and a reflected signal and determining distance based on that relationship. In particular, to obtain distance data under bright sunlight conditions or when high resolution is required, separate efforts may be necessary to eliminate interference (e.g., noise) caused by ambient light.

[0046] FIG. 2 illustrates embodiments of the operation of a Time-of-Flight (TOF) sensing system according to an embodiment of the present invention. Specifically, FIG. 2(a) illustrates an example in which a Time-of-Flight (TOF) sensing system measures a time difference or time delay between a modulated signal and a reflected signal, and FIG. 2(b) illustrates an example in which a Time-of-Flight (TOF) sensing system measures a phase difference or phase delay between a modulated signal and a reflected signal to estimate the time difference or time delay.

[0047] In the example of measuring the time difference or time delay between the modulated signal and the reflected signal described in FIG. 2(a), the round-trip time is directly measured after the modulated signal is output from the transmitter (110) described in FIG. 1, reflected by the target (20), and received by the receiver (120). Here, the modulated signal may have the form of a preset pulse. Since the intensity of the radiant light of the pulse is much greater than the intensity of the radiant light caused by other backgrounds, the method of measuring the time difference or time delay can be used outdoors and is easy to measure over long distances, making it easy to apply to LiDAR for autonomous vehicles. However, since a time-to-digital converter (TDC) that measures time very quickly is required, it is often expensive, and since time measurement cannot be performed on many pixels, the resolution may generally be low, and it can be mainly used for specific high-cost purposes such as satellites, space exploration, and national defense.

[0048] In the example described in Fig. 2(b) for measuring the phase difference or phase delay between a modulated signal and a reflected signal, the distance can be estimated through simple signal processing to measure the phase delay. This method is suitable for measuring relatively short distances within a few meters and is primarily used indoors. Since 3D images are obtained through optical signal processing within the sensor, miniaturization is easy, and it requires a small amount of computation while allowing for a high frame rate. Additionally, it can be easily implemented with a small installation space and relatively low cost. However, in the example of measuring phase difference or phase delay, the measurable distance may be limited. For instance, since the phase difference is used to measure distance, accurate measurement of objects located beyond one full cycle may be impossible (ambiguity problem).

[0049] FIG. 3 illustrates a first example of a Time of Flight (TOF) sensing system according to an embodiment of the present invention. Specifically, FIG. 3 may include an example of a Time of Flight (TOF) sensing system using a continuous wave modulation method. If the time of flight can be directly measured through a modulated signal and a reflected signal, the distance between the Time of Flight (TOF) sensing system (100A) and the target (20) can be easily determined using the speed of light (c). However, it is difficult to directly measure the accurate time of flight, and errors can easily occur. Here, the Time of Flight (TOF) sensing system using a continuous wave modulation method can measure the phase difference between the transmitted signal and the received signal. In particular, the cross-correlation between the received signal and the transmitted signal that the Time of Flight (TOF) sensing system can recognize can enable phase estimation directly related to distance when the modulation frequency is known.

[0050] Referring to FIG. 3, a first example (100A) of a time-of-flight (TOF) sensing system may include a transmitter (110), a receiver (120), a modulator (140), a demodulator (150), a signal processing unit (130), a signal conversion unit (160), a first lens unit (170), and a second lens unit (180).

[0051] The signal processing unit (130) can output data for the estimated distance after receiving a request for distance measurement from another device or user interface, etc., that is linked to a time-of-flight (TOF) method sensing system. In response to the received request, the signal processing unit (130) can drive the modulation unit (140). For example, the signal processing unit (130) can operate the modulation unit (140) by outputting a modulation control signal (MC) to the modulation unit (140).

[0052] In response to the output of the signal processing unit (130), the modulation unit (150) can generate a modulation signal to be output and radiated through the transmitter (110). According to an embodiment, the modulation unit (150) may include a modulation control unit (142) and a transmitter driving unit (144). The modulation control unit (142) may output a modulation period signal (FC) so that the transmitter (110) can generate a modulation signal that is distinguishable from the ambient light / environmental light described in FIG. 1. According to an embodiment, the transmitter (110) may include a light-emitting element (e.g., an emitting diode), and the modulation period signal (FC) output by the modulation unit (150) may be used as a driving signal to drive the light-emitting element. According to another embodiment, the modulation unit (140) may control the transmitter (110) so that the modulation signal generated by the transmitter (110) may have a preset frequency or a preset magnitude. To this end, the modulation control unit (142) can output a modulation period signal (FC) having a specific frequency or a specific phase to the transmitter (110).

[0053] The modulation control unit (142) included in the modulation unit (140) can receive a modulation control signal (MC) and generate a modulation period signal (FC) for generating various types of modulation signals. For example, through the modulation period signal (FC), the transmitter driving unit (144) can control the pulses of the light source or optical modulation element included in the transmitter (110). According to an embodiment, the modulation control unit (142) can control the light source or optical modulation element included in the transmitter (110) to output a modulation signal such as a triangular wave (e.g., a ramp waveform), a sine wave, a sinusoidal wave, or a square wave.

[0054] Meanwhile, due to driving errors and non-linearity of the light-emitting diode (LED) or laser diode (LD) included in the transmitter (110), it may be difficult for the transmitter (110) to generate a specific waveform, such as an ideal waveform like a pulse, a triangle wave, or a sine wave. For example, the light-emitting diode (LED) operates above a threshold current, and non-linearity and saturation of the output light power relative to the input current may occur even within the driving range. Additionally, the gain of the light modulation may not be linear within the driving range of the light-emitting diode (LED). In particular, when using high voltage or high current, the non-linearity or driving error of the light-emitting diode (LED) may increase depending on the design of the driving circuit. Such driving errors directly affect the distance information extraction results and may cause errors in the distance detected by the Time of Flight (TOF) method sensing system. Accordingly, the modulation control unit (142) within the modulation unit (140) may include complex additional algorithms and driving circuits to compensate for such errors.

[0055] The transmitter driving unit (144) can output a driving control signal (DC) for driving a light source or a light modulation element included in the transmitter (110). In response to the driving control signal (DC), the transmitter (110) can output a modulation signal. According to an embodiment, the transmitter (110) may include a laser diode, etc., capable of outputting light in response to a control signal by the modulation unit (140). The modulation signal output from the transmitter (110) may have a frequency belonging to the infrared or ultraviolet region, rather than the visible light region used to determine the color, shape, etc. of objects included in a three-dimensional environment. For example, the transmitter (110) may include a light-emitting diode (LED) or a laser diode (LD) that emits light of a specific wavelength (e.g., near-infrared light of 850 nm). In FIG. 3, the transmitter driving unit (144) is described as being included in the modulation unit (140), but according to the embodiment, the transmitter driving unit (144) may be included in the transmitter (110) which includes a light-emitting diode (LED) or a laser diode (LD). Also, according to another embodiment, the light-emitting diode (LED) or laser diode (LD) included in the transmitter (110) may be directly driven and controlled by the modulation control unit (142).

[0056] The modulation signal output from the transmitter (110) can be output to the outside of the sensing system (110A) through the first lens unit (170). The first lens unit (170) can be implemented in various ways depending on the purpose of use and operating environment of the Time-of-Flight (TOF) method sensing system. For example, the first lens unit (170) may output the modulation signal to a specific location or area, or may evenly emit the modulation signal to a preset area.

[0057] The reflected signal can be transmitted to the receiver (120) through the second lens unit (180). According to an embodiment, the second lens unit (180) can collect the reflected signal and transmit it to the receiver (120). Additionally, the second lens unit (180) may include at least one filter for receiving only the reflected signal that is reflected back by the target (20) as a modulated signal.

[0058] A receiver (120) may include a pixel array (126) in which a plurality of pixels capable of generating pixel information (PI), charge amount, or signal corresponding to the reflected signal are arranged in an array form. The pixel array (126) arranged in the receiver (120) may be controlled by a modulation unit (150) to output a plurality of pixel information (PI), charge amount, or signal to a signal conversion unit (160).

[0059] The modulation period signal (FC) output from the modulation control unit (142) within the modulation unit (140) may include information regarding the modulation signal output through the first lens unit (170). This modulation period signal (FC) may be input to the demodulation unit (150). The demodulation unit (150) may output a driving control signal (TC) for controlling the receiver (120) in response to the modulation period signal (FC). The demodulation unit (150) may determine different phases corresponding to the modulation period signal (FC). According to an embodiment, the phase conversion unit (152) may output phase information (PFC), such as 0 degrees or 180 degrees. In another embodiment, the phase conversion unit (152) within the demodulation unit (150) may output phase information (PFC), such as 90 degrees, 180 degrees, 270 degrees, or 360 degrees, to the driving unit (154). Corresponding to the phase of the modulation signal determined by the phase conversion unit (152), the driving unit (154) can transmit a driving control signal (TC) to the receiver (120). Here, the receiver (120) may include a pixel array (126). The reflected signal collected from the receiver (120) by the phase conversion unit (152) and the driving unit (154) within the demodulation unit (150) will be described in detail later with reference to FIGS. 6 and FIGS. 7. Through this, since the demodulation unit (250) already knows the characteristics of the modulation signal through the modulation period signal (FC), it can drive the receiver (120) through a phase shift to measure, collect, or determine the reflected signal.

[0060] The receiver (120) can be controlled by a driving control signal (TC) output from the modulation unit (150), and the demodulation unit (150) can generate a driving control signal (TC) in response to a modulation period signal (FC) for controlling the transmitter (110). The modulation and conversion unit (152) within the modulation unit (150) outputs a modulation phase signal (PFC) corresponding to the generated modulation period signal (FC), and the driving unit (154) can generate a driving control signal (TC) in response to the modulation phase signal (PFC). Here, the modulation phase signal (PFC) may include a plurality of signals having a preset phase difference. The driving unit (154) can output a driving control signal (TC) for driving a plurality of pixels within a pixel array (126) included in the receiver (120) in response to the modulation phase signal (PFC).

[0061] Pixel information (PI), charge information, charge amount, or signal output from the receiver (120) can be converted into data through the signal conversion unit (160). For example, the pixel information (PI), charge information, charge amount, or signal transmitted through the receiver (120) and the correlation unit (150) may be analog data (AD), and the output converted through the signal conversion unit (160) may be digital data (DD). The data (DD) converted by the signal conversion unit (160) is transmitted to the signal processing unit (130).

[0062] The signal processing unit (130) can estimate the distance between the Time of Flight (TOF) sensing system and the target (20) through a calculation process based on data transmitted from the signal conversion unit (160). The operation of the signal processing unit (130) will be described later based on FIGS. 6 and 7. Additionally, the depth of an object included in a pre-set area can be calculated based on the estimated distance information within the pre-set area. For example, if the distance between the Time of Flight (TOF) sensing system and the target (20) at a first position within the pre-set area is 3m and the distance between the Time of Flight (TOF) sensing system and the target (20) at a second position is 3.5m, the depth between the first position and the second position can be estimated as 50cm.

[0063] FIG. 4 illustrates a second example of a Time-of-Flight (TOF) sensing system according to an embodiment of the present invention. Compared to the example of a Time-of-Flight (TOF) sensing system described in FIG. 3, the Time-of-Flight (TOF) sensing system described in FIG. 4 may have a structure that can be used in a small device by simplifying the modulation signal.

[0064] Referring to FIG. 4, a second example (100B) of a time-of-flight (TOF) sensing system may include a transmitter (210), a receiver (220), a transmitter driving unit (244), a demodulator (250), a signal processing unit (230), a signal conversion unit (260), a first lens unit (270), and a second lens unit (280). According to the embodiment, the demodulator (250) may include a phase conversion unit (252) and a driving unit (254).

[0065] The components of the second example (100B) of the Time-of-Flight (TOF) sensing system described in FIG. 4 may be similar to the components of the first example (100A) of the Time-of-Flight (TOF) sensing system described in FIG. 3. For example, since there is no significant difference in function and role between the transmitter (210, 110), receiver (220, 120), demodulator (150, 250), first lens unit (270, 170), and second lens unit (280, 180), a detailed description is omitted in FIG. 4.

[0066] The signal processing unit (230) can output data for the estimated distance after receiving a request for distance measurement from another device or user interface, etc., that is linked to a time-of-flight (TOF) method sensing system. After receiving a request to obtain distance information, the signal processing unit (230) can transmit a modulation period signal (FC) having a modulation frequency to the transmitter driving unit (244). The transmitter driving unit (244) can output a modulation signal corresponding to the modulation period signal (FC).

[0067] Additionally, a modulation period signal (FC) having a modulation frequency output from the signal processing unit (230) can be input to the demodulation unit (250). The demodulation unit (250) can output a driving control signal (TC) for controlling the receiver (220) in response to the modulation period signal (FC). The demodulation unit (250) can determine different phases corresponding to the modulation period signal (FC). For example, the phase conversion unit (252) within the demodulation unit (250) can output phase information (PFC), such as 90 degrees, 180 degrees, 270 degrees, or 360 degrees, to the phase signal generation unit (240). In response to the phase of the modulation signal determined by the phase conversion unit (252), the driving unit (254) can transmit the driving control signal (TC) to the receiver (220). Here, the receiver (220) may include a pixel array (126). The reflected signal collected at the receiver (220) by the phase conversion unit (252) and the driving unit (254) within the demodulation unit (250) will be explained with reference to FIGS. 6 and 7.

[0068] Since the demodulator (250) already knows the characteristics of the modulation signal through the modulation period signal (FC), it can drive the receiver (220) through a phase shift to measure, collect, or determine the reflected signal.

[0069] The receiver (220) can measure, collect, or determine a reflected signal in response to a driving control signal (TC) transmitted from the demodulator (250) and output pixel information (PI). The pixel information (PI) is transmitted to the signal converter (260), and the signal converter (260) can output digital data (DD) to the signal processing unit (230). The signal processing unit (230) can calculate or acquire distance information based on the digital data (DD), and the operation of the signal processing unit (230) is explained with reference to FIGS. 6 and FIGS. 7.

[0070] According to an embodiment, a time-of-flight (TOF) sensing system (110A, 110B) may include various types of circuits and algorithms for generating a modulation signal output through a transmitter (110) and a driving signal for driving a pixel array (126) included in a receiver (120, 220) in response to the modulation signal.

[0071] The Time of Flight (TOF) sensing systems (110A, 110B) described in FIGS. 3 and 4 can be distinguished through a modulation control unit (142). According to an embodiment, the modulation control unit (142) can perform operations to reduce the diversity of the modulation signal output through the transmitter (110) and the error of the modulation signal. In the case of the Time of Flight (TOF) sensing system (110A) including the modulation control unit (142), the modulation signal can be diversified to facilitate distance measurement in a wider variety of environments. For example, if it is determined that there is a significant error in distance measurement in a specific environment, the signal processing unit (130) can control the modulation control unit (142) to output a modulation period signal (FC) to generate a modulation signal having a different form or different frequency through a modulation control signal (MC).

[0072] FIG. 5 illustrates an example of pixels included in an image sensor mounted on a time-of-flight (TOF) sensing system according to one embodiment of the present invention.

[0073] Referring to FIG. 5, the image sensor (520) may include a pixel array (126) comprising a plurality of pixels (128) and a driving unit (122) for driving the pixel array (126). Within the pixel array (126), a plurality of pixels (128) may be arranged according to a plurality of rows and a plurality of columns.

[0074] According to the embodiment, each of the plurality of pixels (128) may be implemented differently. A first example of a pixel (128A) may include one light receiving element (D) and one transmission gate (TG), and a second example of a pixel (128B) may include two light receiving elements (D1, D2) and two transmission gates (TG1, TG2).

[0075] In the case of the second example of a pixel (128B), there may be two nodes (or two taps) where photocharges are collected in one pixel, and there is an advantage that two transmission gates (TG1, TG2) can be controlled with signals having opposite phases. Additionally, controlling one pixel with two opposite phase signals rather than controlling two adjacent pixels with two opposite phase signals has the advantage of increasing the light-receiving area of ​​one pixel, which can be advantageous for increasing the resolution of the image sensor.

[0076] FIG. 6 illustrates the operation of an image sensor mounted on a time-of-flight (TOF) sensing system according to one embodiment of the present invention.

[0077] Referring to FIG. 6, each of the plurality of pixels (128) included in the image sensor mounted in the Time-of-Flight (TOF) sensing system may include a pair of receivers (312A, 328B). According to an embodiment, referring to FIG. 5 and FIG. 6, one pixel (128) may include a pair of receivers (312A, 328B), and two adjacent pixels (128) may be driven as a pair.

[0078] As described in FIGS. 1 to 4, a modulated signal output from a time-of-flight (TOF) sensing system can be received as a reflected signal after being reflected by a target (20).

[0079] A pair of receivers (312A, 328B) may include a first phase receiver (328A) and a second phase receiver (328B). The first phase receiver (328A) and the second phase receiver (328B) may be activated in opposite phases to detect a reflected signal (e.g., light or light).

[0080] The modulated signal can be configured such that the transmitter (110, 210) is turned on and output during half a cycle (pattern) for one cycle, and the transmitter (110, 210) is turned off and not output during the remaining half cycle (dotted line). After flying to the target (20), this modulated signal can be reflected by the target (20) and received by the receiver (120, 220). The reflected signal and the modulated signal received by the receiver (120, 220) may have a phase difference corresponding to the flight time.

[0081] The first phase receiver (328A) is activated during the half-cycle when the transmitter (110, 210) is turned on and a modulation signal is output, and the second phase receiver (328B) can be activated during the other half-cycle when the transmitter (110, 210) is turned off and no modulation signal is output.

[0082] When the reflected signal and the modulated signal have a phase difference as illustrated, the reflected signal may be partially received through the first phase receiver (328A) and the remainder received through the second phase receiver (328B). By comparing the amount of the reflected signal received through the first phase receiver (328A) with the amount of the reflected signal received through the second phase receiver (328B), the distance the reflected signal has traveled can be estimated.

[0083] For example, although not shown, it is assumed that the distance the modulated signal traveled is 0m. In this case, the amount of reflected signal received through the first phase receiver (328A) is 100%, and the amount of reflected signal received through the second phase receiver (328B) may be 0%.

[0084] The distance traveled by the modulated signal can correspond to the frequency (period) of the modulated signal and the speed of light. For example, assuming the frequency of the modulated signal is 1 Hz, the period of the modulated signal is 1 second. If the amount of reflected signal received through the first phase receiver (328A) is 0% and the amount of reflected signal received through the second phase receiver (328B) is 100%, the modulated signal can be estimated to have traveled for 0.5 seconds. At this time, assuming that the time the modulated signal traveled to the target and the time the reflected signal returned are the same, the distance between the Time of Flight (TOF) sensing system and the target can be determined by multiplying half the flight time, 0.25 seconds, by the speed of light.

[0085] FIG. 7 illustrates a method for estimating distance and a method for determining the magnitude of a modulation signal in a time-of-flight (TOF) sensing system according to an embodiment of the present invention. Referring to FIG. 6 and FIG. 7, the method for estimating distance and the method for determining the magnitude of a modulation signal may be an example of the internal operation of the signal processing unit (130, 230) described in FIG. 3 and FIG. 4.

[0086] Referring to FIG. 7, it is assumed that the modulated signal and the reflected signal have a phase difference (φ). As described in FIG. 1 to 4, the modulated signal output from the time-of-flight (TOF) sensing system can be received as a reflected signal after being reflected by the target (20).

[0087] For example, the modulation signal described in FIG. 7 can be understood as a signal generated by the transmitter (210) described in FIG. 4 and output through the first lens unit (270), and the reflection signal described in FIG. 7 can be understood as a signal transmitted to the receiver (220) through the second lens unit (280) described in FIG. 4.

[0088] A Time-of-Flight (TOF) sensing system can phase shift a modulated signal. For example, it can generate phase shifts of 0°, 90°, 180°, and 270°. As described in FIG. 6, 0° and 180°, and 90° and 270° are cases where the phases are opposite and can be received through a pair of receivers (120, 220).

[0089] For example, the phase shift signals (C1, C2, C3, C4) for distance measurement described in FIG. 7 can be understood as a driving control signal (TC) that is output from the demodulator (250) described in FIG. 4 and transmitted to the receiver (220).

[0090] Each amount of reflected signal (amount of charge generated according to light intensity) received corresponding to each phase shift (0°, 180°, 90°, 270°) may be Q1, Q2, Q3, and Q4. For example, the amount of reflected signal (Q1, Q2, Q3, Q4) described in FIG. 7 can be understood as pixel information (PI) output from the receiver (220) described in FIG. 4.

[0091] Based on this, the phase difference (φ) that can be determined by the signal processing unit (230) described in FIG. 4 can be determined by the following formula.

[0092]

[0093] Once the phase difference (φ) is determined, the speed of light (c) and the frequency (f) of the modulation signal mod Distance can be estimated in correspondence with ).

[0094]

[0095] In addition, the amplitude of the modulated signal can be estimated.

[0096]

[0097] Through the aforementioned method, a Time-of-Flight (TOF) sensing system can determine the frequency or amplitude of a modulated signal and estimate the distance to a target. Additionally, the frequency or amplitude of the modulated signal can be changed depending on the operating environment of the Time-of-Flight (TOF) sensing system.

[0098] Meanwhile, the operation of the aforementioned Time of Flight (TOF) sensing system can reduce the error in the estimable distance and increase the resolution as the amount of reflected signal received for each phase is accurately received after phase shifting of the modulated signal.

[0099] FIG. 8 illustrates the delay occurring during the operation of an image sensor mounted on a time-of-flight (TOF) sensing system according to one embodiment of the present invention.

[0100] Referring to FIG. 8, the image sensor (520) may include a pixel array (126) comprising a plurality of pixels and a driving unit (122) for driving the pixel array (126). Referring to FIG. 5, a plurality of pixels (128) may be arranged in a plurality of rows and a plurality of columns within the pixel array (126).

[0101] The driving unit (122) can supply a control signal (e.g., a preset voltage) to be transmitted to the transmission gate (TG, TG1, TG2, see FIG. 5) of each pixel. The driving unit (122) can determine the control signal supplied to each pixel in response to a clock signal (Clk) or a modulation signal.

[0102] Referring to FIG. 8, it is assumed that a control signal output from a driver (122) is supplied to the transmission gate of each pixel along one column within the pixel array (126). Ideally, the voltage supplied to the transmission gate of each pixel should be delivered to all pixels at the same time, but a delay (RC delay) may occur in the line delivering the voltage. Therefore, a time difference may occur between the voltage supplied to the transmission gate of the pixel closest to the driver (122) (TXnear) and the voltage supplied to the transmission gate of the pixel furthest from the driver (122) (TXfar). In this case, a difference occurs in the driving time of each pixel receiving the reflected signal, that is, the time of outputting the charge in response to the reflected signal.

[0103] Even if the reflection signals received by the pixel closest to the driving unit (122) in the pixel array (126) and the pixel furthest from the driving unit (122) are the same (same distance), if there is a difference in the driving time of each pixel depending on the position of the pixel, a problem may arise in which the distance estimated corresponding to the reflection signal received at each pixel differs, as described in FIGS. 6 and 7.

[0104] In particular, when attempting to estimate the distance more accurately through multiple stages (during multiple cycles of the modulated signal and the reflected signal), the difference in the amount of reflected signal that can be received by the pixel closest to the driving unit (122) within the pixel array (126) and the pixel furthest away can become increasingly larger. That is, the difference can become increasingly larger as the signals of each stage are integrated.

[0105]

[0106] Therefore, in Time-of-Flight (TOF) sensing systems, measuring over multiple periods to estimate a more accurate distance can actually lead to inaccurate distance estimations.

[0107] To address this problem, the resistance of the line transmitting the control signal (e.g., preset voltage) supplied to the transmission gate of each pixel can be reduced by increasing the line size to minimize delay. While this method is effective in reducing delay by lowering resistance, it may create a burden in microfabrication processes due to the need to increase the line size.

[0108] FIGS. 9a to 9d illustrate an example for improving the delay occurring during the operation of an image sensor mounted in a Time-of-Flight (TOF) sensing system according to an embodiment of the present invention. In FIGS. 9a to 9d, the order of pixels to which voltage is supplied is changed to compensate for the delay that occurs during the process of transmitting a control signal delivered by a driving unit through a line. Meanwhile, each pixel receiving the control signal delivered by the driving unit described in FIGS. 9a to 9d may include a plurality of receivers (e.g., a first phase receiver (328A) and a second phase receiver (328B), see FIG. 6) capable of outputting charge information corresponding to the received light at opposite phases of the control signal.

[0109] Referring to FIG. 9a, the voltage output from the driving unit (322A) can be supplied to one end of the odd-numbered column of the pixel array (326A), and then transmitted to the even-numbered column through a line extending from the other end of the odd-numbered column to the even-numbered column. In this case, a control signal can be supplied first to the transmission gate of the pixel closest to the driving unit (322A) in the odd-numbered column, and last to the transmission gate of the pixel closest to the driving unit (322A) in the even-numbered column. Additionally, a control signal can be supplied at an average time to the transmission gate of the pixel furthest from the driving unit (322A) in the odd-numbered column and the transmission gate of the pixel furthest from the driving unit (322A) in the even-numbered column. At this time, by integrating the pixels adjacent to the odd-numbered column and the even-numbered column, the delay caused by the driving time of the pixel varies depending on the position can be compensated for from the driving unit (322A) within the pixel array (326A), thereby resolving the problem that may occur.

[0110] Referring to FIG. 9b, the control signal output from the driving unit (322B) can be supplied to one end of the even column of the pixel array (326B), and then transmitted to the odd column through a line extending from the other end of the even column to the odd column. In this case, the control signal can be supplied first to the transmission gate of the pixel closest to the driving unit (322B) in the even column, and last to the transmission gate of the pixel closest to the driving unit (322B) in the odd column. Additionally, the control signal can be supplied at an average time to the transmission gate of the pixel furthest from the driving unit (322B) in the even column and the transmission gate of the pixel furthest from the driving unit (322B) in the odd column. At this time, by integrating the pixels adjacent to the odd and even columns, the delay caused by the driving time of the pixel varies depending on the position can be compensated for from the driving unit (322B) within the pixel array (326B), thereby resolving the problem.

[0111] Referring to FIG. 9c, a first driving unit (322C) and a second driving unit (324C) are placed on opposite sides (opposite sides) of a pixel array (326C). Specifically, the first driving unit (322C) and the second driving unit (324C) can supply control signals to the transmission gates of each pixel within the pixel array (326C) from opposite directions. The first driving unit (322C) can supply control signals to the odd-numbered rows of the pixel array (326C), and the second driving unit (324C) can supply control signals to the even-numbered rows of the pixel array (326C). Even if delays occur in the odd-numbered rows and even-numbered rows, the delays occurring according to the distance between the first driving unit (322C) and the second driving unit (324C) within the pixel array (326C) can be compensated by integrating pixels adjacent to the odd-numbered rows and even-numbered rows. At this time, the distance between the first driving unit (322C) and the second driving unit (324C), respectively, and the pixel array (326C) may be the same.

[0112] Referring to FIG. 9d, a first driving unit (322D) and a second driving unit (324D) are placed on opposite sides (opposite sides) of a pixel array (326D). Specifically, the first driving unit (322D) and the second driving unit (324D) can supply voltage to the transmission gate of each pixel within the pixel array (326D) from opposite directions. The first driving unit (322D) can supply a control signal to the even rows of the pixel array (326D), and the second driving unit (324D) can supply a control signal to the odd rows of the pixel array (326D). Even if delays occur in the even rows and odd rows, the pixels adjacent to the even rows and odd rows can be combined to compensate for the delays occurring depending on the distance from the first driving unit (322D) and the second driving unit (324D) within the pixel array (326C).

[0113] Figure 10 illustrates the result of improved delay through the example described in Figures 9a to 9d.

[0114] Referring to FIG. 10, even if there is a time difference between the voltage (TXnear) supplied to the transmission gate of the pixel closest to the driver and the voltage (TXfar) supplied to the transmission gate of the pixel furthest from the driver, the order of the pixels to which the voltage is supplied can be changed to compensate for the delay occurring in the line of the voltage delivered by the driver, as shown in FIG. 9a to 9d. In this case, substantially the same effect as integrating the signals of the two pixels corresponding to the voltage (TXnear) supplied to the transmission gate of the pixel closest to the driver and the voltage (TXfar) supplied to the transmission gate of the pixel furthest from the driver can occur.

[0115] In FIG. 10, it was explained that the driving time corresponding to the voltage (TXnear) supplied to the transmission gate of the pixel closest to the driving unit in the first cycle and the voltage (TXfar) supplied to the transmission gate of the pixel furthest from the driving unit in the second cycle are integrated, but the driving time corresponding to the voltage (TXnear) supplied to the transmission gate of the pixel closest to the driving unit and the voltage (TXfar) supplied to the transmission gate of the pixel furthest from the driving unit can be integrated for every cycle.

[0116] Therefore, as described in Fig. 8, the difference in driving time between the pixel closest to the driving unit and the pixel furthest from the driving unit does not gradually increase, and even if measured over multiple cycles, that is, even if the signals of each stage are integrated, the driving time can be the same without any difference according to the pixel position.

[0117]

[0118] Through this method, delays that may occur depending on the distance of the pixel position within the pixel array from the driving unit can be compensated, thereby resolving problems that may arise from variations in pixel driving time depending on the position.

[0119] Meanwhile, although specific embodiments have been described in the detailed description of the present invention, it is understood that various modifications are possible within the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims set forth below as well as equivalents thereof.

Claims

Claim 1 An image sensor mounted on a Time of Flight (TOF) type sensing system comprises: a pixel array including a plurality of pixels arranged according to a plurality of rows and a plurality of columns, which generates an electric charge corresponding to received light; and a first driving unit that supplies a control signal to the plurality of pixels through the plurality of columns, wherein the first driving unit supplies the control signal to one of an odd column and an even column among the plurality of columns, and the odd column and the even column are connected so that pixels adjacent to the odd column and the even column are connected, and when the first driving unit supplies the control signal to one end of the odd column, the other end of the odd column is connected to one end of the even column, or when the first driving unit supplies the control signal to one end of the even column, the other end of the even column is connected to one end of the odd column. Claim 2 delete Claim 3 An image sensor according to claim 1, further comprising a second driving unit that supplies the control signal to the other of the odd and even columns among the plurality of columns. Claim 4 In paragraph 3, the image sensor, wherein the first driving unit and the second driving unit are positioned on opposite sides with respect to the pixel array. Claim 5 In paragraph 3, the distance between each of the first driving unit and the second driving unit and the pixel array is the same, for the image sensor. Claim 6 An image sensor according to claim 1, wherein the pixel comprises one or more diodes and a number of transfer gates equal to the number of diodes, and the control signal is supplied to the transfer gates. Claim 7 An image sensor according to claim 1, wherein the pixel comprises: a first receiver that detects the received light in a first phase interval; and a second receiver that detects the received light in a second phase interval opposite to the first phase interval. Claim 8 An image sensor mounted on a Time of Flight (TOF) sensing system comprises: a pixel array including a plurality of pixels arranged according to a plurality of rows and a plurality of columns, which generate charge information corresponding to received light; a first driving unit that supplies a first control signal through one of an odd column and an even column in the pixel array; and a second driving unit that supplies a second control signal through the other of the odd column and an even column in the pixel array, wherein the first control signal and the second control signal are supplied from opposite directions. Claim 9 An image sensor according to claim 8, wherein if the first control signal is transmitted through an odd column among the plurality of columns, the second control signal is transmitted through an even column among the plurality of columns, and if the first control signal is transmitted through an even column, the second control signal is transmitted through an odd column. Claim 10 An image sensor according to claim 8, wherein the first control signal and the second control signal are alternately supplied to the plurality of columns. Claim 11 In claim 8, the image sensor, wherein the first driving unit and the second driving unit are positioned on opposite sides with respect to the pixel array. Claim 12 In claim 8, the pixel comprises one or more diodes and a number of transfer gates equal to the number of diodes, and the control signal is supplied to the transfer gates, an image sensor. Claim 13 An image sensor according to claim 8, further comprising a signal converter that converts the charge information output from the pixel array into a digital signal. Claim 14 A transmitter that outputs a modulated signal having a preset phase; an image sensor that receives a reflected signal reflected from a target by the modulated signal; and a signal processing unit that determines the distance to the target through the relationship between the modulated signal and the reflected signal, wherein the image sensor generates charge information corresponding to the reflected signal and includes a pixel array comprising a plurality of pixels arranged according to a plurality of rows and a plurality of columns; and a first driving unit that supplies a control signal to the plurality of pixels through the plurality of columns. A Time of Flight (TOF) type sensing system comprising a signal conversion unit that converts the charge information output from the pixel array into a digital signal and transmits it to the signal processing unit, wherein the first driving unit supplies the control signal to one of the odd and even columns among the plurality of columns, and the odd and even columns are connected so that pixels adjacent to the odd and even columns are connected, and when the first driving unit supplies the control signal to one end of the odd column, the other end of the odd column is connected to one end of the even column, or when the first driving unit supplies the control signal to one end of the even column, the other end of the even column is connected to one end of the odd column. Claim 15 delete Claim 16 In claim 14, the image sensor further comprises a second driving unit that supplies the control signal to the other of the odd and even columns among the plurality of columns, a time-of-flight (TOF) type sensing system. Claim 17 In claim 16, the first driving unit and the second driving unit are positioned on opposite sides with respect to the pixel array, in a time-of-flight (TOF) type sensing system. Claim 18 In claim 16, a time-of-flight (TOF) sensing system in which the distance between each of the first driving unit and the second driving unit is the same. Claim 19 In claim 14, the pixel comprises one or more diodes and a number of transfer gates equal to the number of diodes, and the control signal is supplied to the transfer gates, a time-of-flight (TOF) sensing system. Claim 20 In claim 14, the pixel comprises a first receiver that detects the reflected signal in a first phase interval; and a second receiver that detects the reflected signal in a second phase interval opposite to the first phase interval, in a time-of-flight (TOF) sensing system.

Images