Solid-state imaging system and triangulation ranging method

Abstract

The invention discloses a solid-state imaging system and a triangulation ranging method.The solid-state imaging system comprises a light source and a sensor chip, and the light source responds to a light source enable signal to output a light signal; the sensor chip comprises a plurality of photosensitive elements and a change detection circuit coupled with the photosensitive elements, and the change detection circuit outputs a corresponding brightness change event based on a comparison result of light intensity change of light collected by the photosensitive elements and a reference threshold value; the sensor chip generates a detection enable signal and synchronously outputs a light source enable signal, or the light source enable signal and the detection enable signal are synchronously output by an independently configured control unit. According to the invention, the DVS technology and the active light technology are combined, and the change detection circuit is controlled to detect the brightness change event when the brightness change is actively controlled synchronously, so that the influence of a static background on a solid-state imaging system can be effectively removed, and in the application of triangulation distance measurement, the distance measurement accuracy is improved. And the dynamic range and the frame frequency of the sensor chip for triangulation distance measurement are improved.

Description

Technical Field

[0001] This invention relates to the field of solid-state imaging, specifically to a solid-state imaging system and a triangulation method. Background Technology

[0002] Traditional triangulation ranging systems use a combination of linear photosensitive arrays and a light source. Distance is measured by illuminating the scene being measured with the light source; in this triangulation ranging system, the photosensitive array directly extracts the light signal.

[0003] However, there is a problem with uneven brightness in the tested scene, requiring a stronger light source for supplemental lighting to improve the signal-to-noise ratio. This increases system power consumption, and strong light is also detrimental to human eye safety. Furthermore, the signal generated by the photosensitive array is linearly proportional to the light intensity, resulting in a small dynamic range. Finally, there is another issue: since the optical signal is analog, it requires analog-to-digital (ADC) conversion. Typically, each chip has one ADC, leading to a relatively long ADC conversion time, which affects the frame rate.

[0004] Currently, DVS technology can significantly remove the influence of static background on the system's signal and achieve high dynamic range through logarithmic transformation. Furthermore, due to the built-in 1.5-bit ADC function of DVS, high-speed signal readout can also be achieved. While DVS technology has been widely researched and developed as a sensor for detecting changes in a scene, it has not yet been applied in conjunction with active light, thus failing to achieve accurate capture of the active light emission state. Summary of the Invention

[0005] To overcome the shortcomings of the above technologies, this invention provides a solid-state imaging system and a triangulation ranging method, which combines DVS technology and active light technology. When the brightness of the active light changes, the DVS circuit is controlled to detect the brightness change event, thereby effectively removing the influence of the static background on the system and improving the dynamic range and frame rate of the sensor chip used for triangulation ranging.

[0006] The technical solution adopted by the present invention to overcome its technical problems is as follows: The first aspect of the present invention proposes a solid-state imaging system, including a light source, the light source outputting a light signal in response to a light source enable signal; a sensor chip, the sensor chip including at least a plurality of photosensitive elements and a change detection circuit coupled to the photosensitive elements, the change detection circuit responding to a detection enable signal, for converting the photocurrent output by the light intensity collected by the photosensitive elements into a light intensity voltage, and outputting a change voltage based on a reference voltage and a light intensity voltage, and outputting a corresponding brightness change event according to the comparison result of the change voltage and a preset reference threshold; wherein, the sensor chip generates a detection enable signal and synchronously outputs a light source enable signal, or the light source enable signal and the detection enable signal are synchronously output by an independently configured control unit.

[0007] By synchronously outputting a light source enable signal and detecting the enable signal through a sensor chip, the light source is synchronously controlled to achieve active brightness changes. The change detection circuit is also controlled to detect brightness change events, thus synchronously achieving both active light control and detection. Furthermore, the light source enable signal and the detection enable signal can be synchronously controlled through an independently configured control unit.

[0008] Furthermore, the change detection circuit includes at least a current-to-voltage conversion unit, a change integration and reset unit, and a quantization unit coupled in sequence. The current-to-voltage conversion unit is coupled to a photosensitive element and is used to logarithmically transform the photocurrent output by the photosensitive element into a photointensity voltage. The change integration and reset unit is used to update and save a reference voltage based on a coupled external signal or a brightness change event, and to obtain and output a change voltage based on the difference between the current photointensity voltage and the reference voltage. The quantization unit is used to compare the change voltage with a preset reference threshold and output a corresponding brightness change event based on the comparison result.

[0009] The change detection circuit can be implemented using a DVS circuit.

[0010] Furthermore, the operating state of the change detection circuit is controlled based on the operating enable signal.

[0011] The operating enable signal and the detection enable signal can control the operating state of the change detection circuit individually or in combination.

[0012] Furthermore, the operation enable signal controls the change integration and reset unit of the change detection circuit, thereby controlling the operating state of the change detection circuit.

[0013] Furthermore, the enable signal controls the current-voltage conversion unit of the change detection circuit, thereby controlling the operating state of the change detection circuit.

[0014] Furthermore, the enable signal controls the quantization unit of the change detection circuit, thereby controlling the operating state of the change detection circuit.

[0015] The operating state of the change detection circuit is controlled by controlling the operating state of each functional module of the change detection circuit.

[0016] Furthermore, the sensor chip also includes a counter for recording the number of brightness change events.

[0017] A counter or counting circuit is set up to record the brightness change digital output signal, i.e., the brightness change event, output by the change detection circuit, so as to realize the quantitative counting of light intensity changes.

[0018] Furthermore, when the light intensity output by the light source changes from weak to strong, the change detection circuit synchronously receives the brightness change event output by the change detection circuit as a brightening event; when the light intensity output by the light source changes from strong to weak, the change detection circuit synchronously receives the brightness change event output by the change detection circuit as a dimming event.

[0019] Furthermore, the sensor chip also includes a memory used to synchronously read out brightness change events.

[0020] Furthermore, it also includes the integration of the change detection circuit and the reset of the reset unit after reading out the brightness change event.

[0021] Read out the completed brightness change event and reset it, memorize the current scene light intensity in real time, and filter out the next light intensity change that is not caused by the change of light source.

[0022] Another aspect of the present invention proposes a triangulation method based on the above-mentioned solid-state imaging system, characterized in that it specifically includes: the solid-state imaging system simultaneously turning on the light source enable signal and the detection enable signal; the sensor chip acquiring the brightness change of the light reflected by the object under test and outputting the brightness change event; and the sensor chip calculating the distance to the object under test based on several brightness change events.

[0023] The beneficial effects of this invention are:

[0024] 1. By combining DVS technology and active light technology, the system controls the DVS circuit to detect brightness change events when the active light brightness changes, thereby effectively removing the influence of static background on the system.

[0025] 2. By controlling the working state of the synchronous control change detection circuit and actively controlling the light source, the laser light is distinguished from the background light and the light that is moving and changing. The light intensity changes caused by moving objects are removed, and only the light intensity changes caused by the light source are collected.

[0026] 3. Reset the change detection circuit between each measurement to memorize the current scene light intensity in real time and filter out the light intensity changes that are not caused by changes in the light source in the next measurement;

[0027] 4. By quantitatively counting multiple changes in light intensity, the degree of change in the brightness of the light source can be obtained;

[0028] 5. By adopting DVS technology, the dynamic range of the sensor chip used in triangulation ranging is expanded, and the frame rate is improved;

[0029] 6. Combining DVS technology and active light technology, it is applied to triangulation ranging, which improves the dynamic range of the sensor chip used and eliminates the need for AD conversion, thereby increasing the frame rate and improving measurement accuracy and efficiency. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the solid-state imaging system according to an embodiment of the present invention;

[0031] Figure 2 This is a schematic block diagram of the change detection circuit according to an embodiment of the present invention;

[0032] Figure 3 For the corresponding Figure 1 Signal timing diagram of a solid-state imaging system;

[0033] Figure 4 This is a schematic diagram of a solid-state imaging system according to another embodiment of the present invention;

[0034] Figure 5 For the corresponding Figure 4 Signal timing diagram of a solid-state imaging system;

[0035] Figure 6 This is a block diagram illustrating the principle of the enable signal acting on the current-voltage conversion unit in an embodiment of the present invention.

[0036] Figure 7 This is a block diagram illustrating the principle of the enable signal acting on the variable integral and reset unit in an embodiment of the present invention.

[0037] Figure 8 This is a block diagram illustrating the principle of the enabling signal acting on the quantization unit in an embodiment of the present invention.

[0038] Figure 9 This is a principle block diagram illustrating another implementation of the operation enable signal acting on the quantization unit according to an embodiment of the present invention;

[0039] Figure 10 This is a block diagram illustrating the principle of the change detection circuit coupled to the memory in an embodiment of the present invention.

[0040] In the figure, 1-photosensitive element, 2-current-voltage conversion unit; 3-variable integration and reset unit; 4-quantization unit. Detailed Implementation

[0041] To facilitate a better understanding of the present invention by those skilled in the art, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following are merely exemplary and do not limit the scope of protection of the present invention.

[0042] like Figure 1 The diagram shown is a schematic representation of an embodiment of the solid-state imaging system of this application. The solid-state imaging system includes a light source and a sensor chip, wherein the sensor chip includes at least several photosensitive elements and couplings to the photosensitive elements, such as... Figure 2The change detection circuit shown is used to convert the photocurrent generated by the change in light intensity collected by the photosensitive element into a light intensity voltage in response to a detection enable signal. Based on a reference voltage and the light intensity voltage, it outputs a change voltage and, according to the comparison result between the change voltage and a preset reference threshold, outputs a corresponding brightness change event. The reference voltage corresponding to the reference light intensity is stored in the change detection circuit and can be updated based on the brightness change event fed back to the change detection circuit or based on a coupled external signal. The digital output signal of brightness is the brightness change event.

[0043] The light source responds to the light source enable signal emitted by the sensor chip and outputs a light signal. The sensor chip generates a detection enable signal and synchronously outputs a light source enable signal, which synchronously activates the change detection circuit. After the light signal output by the light source enable signal illuminates the object under test, the reflected light is received by the photosensitive element of the sensor chip. The change detection circuit logarithmically transforms the photocurrent generated by the light intensity collected by the photosensitive element into a light intensity voltage Vp. Based on the reference light intensity, it outputs a change voltage Vdiff based on the change in photocurrent and outputs a corresponding brightness change digital output signal 1 according to the comparison result of the change voltage and a preset reference threshold. The reference voltage corresponding to the reference light intensity is stored in the change detection circuit. The reference voltage is the voltage corresponding to the reference light intensity, which is the voltage stored across the first capacitor C1. When the change voltage exceeds the preset reference threshold, a corresponding brightness change digital output signal is output. The brightness change digital output signal is fed back to the change detection circuit, i.e., it is related to the light intensity. Figure 2 The ARST signal coupling shown updates the reference light intensity, which in turn updates the reference voltage. The updated reference voltage is the value of Vp when the brightness change digital output signal is fed back to the change detection circuit.

[0044] It should be noted that the collected light intensity includes both background light and light emitted by the light source. The light source control signal is not limited to pulse modulation, continuous wave modulation, or digital signal control enable, etc. The detection enable signal is... Figure 3 The control timing shown is relevant to the present invention. Figure 1 The principle of the solid-state imaging system shown is explained. The detection enable signal can be one or both of the following: brightness detection enable and darkness detection enable, such as... Figure 3 As shown, in one embodiment of the present invention, the light intensity can be detected from dark to bright by enabling the change detection circuit through the brightness detection enable signal, and the light intensity can be detected from bright to dark by enabling the change detection circuit through the dimming detection enable signal.

[0045] When the light source control signal is not turned on, the brightness detection enable signal is enabled. Its signal range is greater than the rising edge of the light source control signal. The light source control signal is turned on synchronously. The light source emits light slightly later than the light source control signal. The light source emits light to the object under test. At this time, the change detection circuit detects the change in brightness of the object under test from dark to bright, and generates the corresponding digital signal output 1. After the brightness change is detected, the brightness detection enable signal is turned off.

[0046] Before turning off the light source control signal, the dimming detection enable signal is turned on. Its signal range is longer than the falling edge of the light source control signal. The light source control signal is turned off synchronously. The light source cuts off slightly later than the turn-off time of the light source control signal. At this time, the change detection circuit detects the change in brightness of the object under test from bright to dark, and generates the corresponding digital signal output 0. After the brightness change is detected, the dimming detection enable signal is turned off.

[0047] In another embodiment of the invention, the solid-state imaging system further includes a control unit, such as... Figure 4 As shown, the control unit synchronously outputs a detection enable signal and a light source enable signal. Figure 5 The control timing shown is relevant to the present invention. Figure 4 The principle of the solid-state imaging system shown is explained.

[0048] Before the light source control signal is turned on, the detection enable signal is enabled and the light source control signal is turned on simultaneously. The signal range of the detection enable signal is greater than the rising edge of the light source control signal. The light source emits light slightly later than the light source control signal. The light source emits light to the object under test. At this time, the change detection circuit detects the change in brightness of the object under test from dark to bright, and generates the corresponding digital signal output 1. After the brightness change is detected, the detection enable signal is turned off.

[0049] Before turning off the light source control signal, the detection enable signal is turned on and the light source control signal is turned off simultaneously. The signal range of the detection enable signal is greater than the falling edge of the light source control signal. The light source cutoff time is slightly later than the turn-off time of the light source control signal. At this time, the change detection circuit detects the change in brightness of the object under test from bright to dark, and generates the corresponding digital signal output 0. After the brightness change is detected, the detection enable signal is turned off.

[0050] By actively synchronizing the operating state of the change detection circuit with the light source control signal, the laser can be distinguished from the background light and moving light.

[0051] In some embodiments, the operating state of the change detection circuit can also be controlled by an enable signal. The change detection circuit includes a current-to-voltage conversion unit 2, a change integration and reset unit 3, and a quantization unit 4, which are coupled in sequence. The current-to-voltage conversion unit 2 is coupled to the photosensitive element 1 and is used to logarithmically convert the photocurrent output by the photosensitive element 1 to a photointensity voltage Vp.

[0052] The variation integration and reset unit 3 is used to update and save the reference voltage based on the coupled external signal or brightness change event, and to obtain and output the variation voltage Vdiff based on the difference between the current light intensity voltage and the reference voltage.

[0053] Quantum unit 4 is used to compare the changing voltage with a preset reference threshold, and outputs a corresponding digital output signal of brightness change based on the comparison result. The digital output signal of brightness change corresponds to a brightening event or a darkening event.

[0054] like Figure 2 As shown, the enable signal controls the operation. Figure 2 The change detection circuit in the image contains a change integration and reset unit 3, i.e., the ARST reset signal, which controls the operating state of the change detection circuit. When the enable signal is disabled, the change detection circuit is in a continuous reset state and does not detect changes in light intensity.

[0055] It should be noted that the operating enable signal is the control signal that activates the entire change detection circuit, while the detection enable signal is the control signal that activates the brightness change detection circuit. The brightening detection enable signal and the dimming detection enable signal are independent signals that control the activation of the brightness increase detection function and the brightness decrease detection function, respectively. The detection enable signal, brightening detection enable signal, dimming detection enable signal, and operating enable signal can all be controlled by the control unit. One or more of them can be logically combined and connected to the change detection circuit in the sensor chip. Each change detection circuit can be dedicated, or some or all change detection circuits can share the same signal, thereby controlling the operating state of the change detection circuit.

[0056] In one embodiment of the present invention, the working enable signal is applied to... Figure 6 The current-to-voltage conversion unit shown controls the operating state of the change detection circuit. By cutting off the photocurrent, it is impossible to detect changes in light intensity.

[0057] Figure 6The illustrated current-to-voltage conversion unit is equipped with a switch controlled by an enable signal (EN). When the enable signal EN is active, the switch is turned off, and the current-to-voltage conversion unit logarithmically converts the photocurrent output from the photosensitive element into a photocurrent voltage (Vp). The back-end circuit outputs a changing voltage (Vdiff) based on the change in photocurrent. The quantization unit compares the output voltage Vdiff with an upper threshold and determines whether the change in brightness exceeds the upper threshold. If the change exceeds the upper threshold, the quantization unit detects a brightening event. If the change is equal to or less than the upper threshold, the comparator compares the changing voltage Vdiff with a lower threshold and determines whether the change in brightness is below the lower threshold. If the change is below the lower threshold, the quantization unit detects a darkening event. When the enable signal EN is disabled, the switch is turned on, and photocurrent conversion is not possible.

[0058] In yet another embodiment of the invention, the enable signal is applied to... Figure 7 The change integration and reset unit shown cuts off the light intensity voltage Vp, thereby cutting off the operation of the change detection circuit. A switch is located at the input of the change integration and reset unit. When the enable signal EN is enabled, the switch turns to the closed state, and the back-end circuit can normally output the change voltage Vdiff according to the light intensity voltage VP. When the enable signal EN is disabled, the switch turns to the open state, and the back-end circuit cannot output the change voltage Vdiff according to the light intensity voltage VP.

[0059] In one embodiment of the present invention, the working enable signal is applied to... Figure 8 and Figure 9 The quantization unit shown controls the operating state of the change detection circuit.

[0060] In some implementations, one switch is located at the ON change detection terminal of the quantization unit, and another switch is located at the OFF change detection terminal of the quantization unit. When the enable signal is disabled, the ON and OFF change detection terminals cannot compare the changed voltage Vdiff with a preset reference threshold. When the enable signal is enabled, the ON and OFF change detection terminals cannot compare the changed voltage Vdiff with the preset reference threshold, thus outputting a normal brightness change event based on the comparison result. It should be noted that, depending on the requirements of the change detection circuit, for example, if only the brightness increase detection function of the change detection circuit is required, then only the ON change detection terminal needs to be controlled separately.

[0061] In some other implementations, one end of the switch is coupled to the output terminal of the brightness change digital output signal, and the other end is coupled to ground. The EN signal controls the switch to close, and the brightness change digital output signal is coupled to ground. In this case, the change detection circuit cannot output the brightness change digital output signal normally.

[0062] It should be noted that the brightness detection enable signal and the darkness detection enable signal can also be applied to... Figure 8 and Figure 9 The two switches shown independently control the activation of the brightness increase detection function and the brightness decrease detection function, respectively.

[0063] In another embodiment of the invention, such as Figures 6-9 As shown, the digital signal output of the quantization unit is coupled to a counter to quantitatively count multiple changes in light intensity. Typically, 0s and 1s are counted individually. By quantitatively counting the changes in light intensity, the degree of brightness change can be obtained.

[0064] In another embodiment of the invention, such as Figure 10 As shown, the digital signal output of the quantization unit is coupled to a memory, which is used to synchronously read out brightness change events. When the light signal output by the light source changes from weak to strong, the change detection circuit synchronously receives the brightening event of the brightness change event; when the light signal output by the light source changes from strong to weak, the change detection circuit synchronously receives the darkening event of the brightness change event. After reading out the brightness change event, the reset unit of the change detection circuit is reset. The backend can generate pixel signals based on the brightness change events.

[0065] Between each measurement, the change detection circuit is integrated and reset by the reset unit to remove light intensity changes caused by moving objects. The light intensity changes collected are caused by the light source. After the previous reading is completed, the system is reset so that no additional brightness change events or ON / OFF information are generated. The current scene light intensity is memorized in real time, and light intensity changes that are not caused by changes in the light source are filtered out.

[0066] In another embodiment, with Figure 1Taking the triangulation method based on the aforementioned solid-state imaging system as an example, the laser triangulation method suffers from interference from ambient light when the brightness of the measured scene is uneven or the light intensity is high. This makes it difficult to calculate the true distance of the target based on the center position of the spot and the principles of laser triangulation. Therefore, the solid-state imaging system of this invention actively controls the emission or non-emission of the laser source and detects changes in the brightness of the light reflected from the target using a change detection circuit. This improves the dynamic range of light intensity generation and eliminates the need for AD conversion, increasing the frame rate. Consequently, the spot formed on the sensor chip becomes more obvious and concentrated, improving measurement accuracy and efficiency.

[0067] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on its differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. The systems and system embodiments described above are merely illustrative. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

Claims

1. A solid-state imaging system, characterized in that, At least including: A light source that outputs a light signal in response to a light source enable signal; The sensor chip includes at least several photosensitive elements and a change detection circuit coupled to the photosensitive elements. The change detection circuit responds to the detection enable signal and is used to convert the photocurrent output by the light intensity collected by the photosensitive element into a light intensity voltage, and output a change voltage based on the reference voltage and the light intensity voltage, and output a corresponding brightness change event according to the comparison result of the change voltage and the preset reference threshold. The sensor chip generates a detection enable signal and synchronously outputs a light source enable signal, or the light source enable signal and the detection enable signal are synchronously output by an independently configured control unit.

2. The solid-state imaging system according to claim 1, characterized in that, The change detection circuit includes at least a current-to-voltage conversion unit, a change integration and reset unit, and a quantization unit coupled in sequence. The current-to-voltage conversion unit is coupled to the photosensitive element and is used to logarithmically convert the photocurrent output by the photosensitive element into a photocurrent voltage. The change integration and reset unit is used to update and save the reference voltage based on the coupled external signal or brightness change event, and to obtain and output the change voltage based on the difference between the current light intensity voltage and the reference voltage. The quantization unit is used to compare the changing voltage with a preset reference threshold and output the corresponding brightness change event based on the comparison result.

3. A solid-state imaging system according to claim 2, characterized in that, The operating state of the change detection circuit is controlled based on the working enable signal.

4. A solid-state imaging system according to claim 3, characterized in that, The enable signal controls the change integration and reset unit of the change detection circuit, thereby controlling the operating state of the change detection circuit.

5. A solid-state imaging system according to claim 3, characterized in that, The enable signal controls the current-voltage conversion unit of the change detection circuit, thereby controlling the operating state of the change detection circuit.

6. A solid-state imaging system according to claim 3, characterized in that, The enable signal controls the quantization unit of the change detection circuit, thereby controlling the operating state of the change detection circuit.

7. A solid-state imaging system according to any one of claims 1-6, characterized in that, The sensor chip also includes a counter, which is used to record the number of brightening or darkening events of brightness change events.

8. A solid-state imaging system according to any one of claims 1-6, characterized in that, When the light intensity output by the light source changes from weak to strong, the change detection circuit synchronously receives the brightness change event output by the change detection circuit; when the light intensity output by the light source changes from strong to weak, the change detection circuit synchronously receives the brightness change event output by the change detection circuit.

9. A solid-state imaging system according to any one of claims 1-6, characterized in that, The sensor chip also includes a memory used to synchronously read out brightness change events.

10. A triangulation method based on the solid-state imaging system according to any one of claims 1-9, characterized in that, Specifically, it includes: The solid-state imaging system simultaneously activates the light source enable signal and the detection enable signal. The sensor chip collects the brightness changes of the light reflected from the object under test and outputs the brightness change event. The sensor chip calculates the distance to the object being measured based on several brightness change events.

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