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Analog Motion Detection Circuits Using Simple Edge Detection Circuits Based on the Vertebrate Retina
Analog Motion Detection Circuits Using Simple Edge Detection Circuits Based on the Vertebrate Retina Wan Nor Dalila binti Wan Mahmood, Siti Nur Ain binti Mehat and Kimihiro Nishio Electrical and Electronic Engineering, Tsuyama National College of Technology 624-1 Numa, Tsuyama, Okayama 708-8509, Japan (Tel: +81-868-24-8266; e-mail: nishio@ tsuyama-ct.ac.jp) Abstract: We proposed in this research novel analog motion detection circuits using previous proposed edge detection circuits based on the vertebrate retina, which is characterized by the wide dynamic range, low power consumption and compact structure. The structure of the proposed motion detection circuit becomes compact, which is designed mainly using 6 n-channel metal oxide semiconductor (nMOS) transistors and 2 capacitors. The simulation results with the simulation program with integrated circuit emphasis (SPICE) showed that the proposed circuit can generate the motion signal. By using this circuit, we can expect to realize the visual sensor in one chip, which is characterized by the high resolution, wide dynamic range and low power consumption. Keywords: motion detection, edge detection, image processing, retina, analog circuit, vision chip 1. INTRODUCTION A simple system for processing moving images in real time is required in the robot vision, the collision avoidance system and others. In order to satisfy this demand, many researchers proposed the motion detection circuits based on the biological vision system (Mead 1989 ; Moini 1999 ; Yamada et al. 2001). Because the circuits were proposed by mimicking the parallel processing function of the biological system, it is able to process moving images in real time. Such processing is difficult for typical image processing system constructed with digital computer. The motion detection circuit uses the edge detection circuit as a pre-processor, and detects the movement of the edge of the object (Yamada et al. 2001). Since the motion detection circuit is used in connection with the edge detection circuit, the area of the circuit becomes large, and the integrated circuit (one chip) of this circuit becomes low resolution. To solve this problem, we proposed the simplest circuit for edge detection (Nishio et al. 2008a). Each pixel circuit of complementary metal oxide semiconductor (CMOS) image sensors, to realize high resolution is designed with only nchannel metal oxide semiconductor (nMOS) transistors (Fossum 1997). The edge detection circuit consists of only nMOS transistors based on the structure of CMOS image sensor. We showed that the edge detection circuit (Nishio et al. 2008a) becomes half area compared with the circuit proposed by H. Yamada (2001), which was simple circuit. By using the circuit, it is able to realize the motion detection circuit, which is characterized by high resolution, in one chip. And the proposed edge detection circuit is characterized by the wide dynamic range against light intensity. Therefore, by
using this circuit, it is able to realize the motion detection circuit with wide dynamic range. In this study, we tried to propose and design the compact motion detection circuit, which can easily connect with the previous proposed edge detection circuit as the pre-processor. The proposed circuit for generating the motion signal was mainly constructed with 6 nMOS transistors and 2 capacitors. The results with the simulation program with integrated circuit emphasis (SPICE) showed that the proposed circuit can generate the motion signal. 2. EDGE DETECTION CIRCUIT The edge detection circuit (Nishio et al 2008a) is shown in Fig. 1. Two-dimensional array of the edge detection circuits is shown in Fig. 1(a). The unit circuit is constructed with a photodiode (PD) and a processing circuit. Each unit circuit is connected with neighboring unit circuits. Figure 1(b) shows a unit circuit. The photodiode is used as the input part and the PD generates the current Ip which is proportional light intensity. The voltage Vp is changed by Ip. Nodes a, b and c of this circuit corresponds to those of a, b, and c in Fig. 1(a), respectively. These nodes are connected with neighboring unit circuits. The output voltage Vout is represented by the following equation. Vout = Vp − Vh .
(1)
Since the current Ih is changed by Idif at the nearest edge position, the voltage Vh is also changed. At the nearest edge position, the variance of Vh is large. Then, Vout becomes large and the output current Iout becomes large. Thus, the circuit can detect edge positions. This edge detection circuit was evaluated by SPICE. Figure 1(c) shows the simulation result. The circuit was arranged to
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The output signal of the edge detection circuit in Fig. 1 is used as the input signal of the motion detection circuit. However, because the edge signal is a small current, the motion detection circuit has a problem of incorrect operation due to noise and device mismatches. Therefore, we tried to amplify (digitize) the edge signals.
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Fig. 1 Previous proposed edge detection circuit. (a) Network structure. (b) Unit circuit. (c) Simulation result obtained by SPICE.
46×50. The result is represented by the image. As a result, it was confirmed that this edge detection circuit operated normally. Since this edge detection circuit constructed with only nMOS transistors is simple structure, low resolution can be expected in case of designing the integrated circuit. Because it is confirmed that there is dynamic range of 5 decades, the circuit is characterized by the wide dynamic range against light intensity. The circuit is characterized by the low power consumption since all MOS transistors constructing the circuit are operated in the subthreshold region. The edge detection circuit is often used as a pre-processor for the image processing system. It is necessary to propose the simple motion detection circuit that can connect with this excellent edge detection circuit.
Recently, the circuit for digitizing the edge signal was proposed (Nishio et al. 2006 ; Yamada et al. 2001). Each unit circuit for edge detection was connected with each digitization circuit. The connected circuit could operate normally. However, the unit circuit connecting the edge detection circuit, the digitization circuit and the circuit for generating the motion signal became large area, and the resolution became low. Since the digitization circuit is designed by CMOS circuit, the connected circuit loses the advantage of simple structure of the edge detection circuit constructed with only nMOS transistors. Thus, we considered to connect a digitization circuit to multiple edge detection circuits. As an easy way, x-y scan using the CMOS image sensor is considered. Based on this way, to make the process easier, we propose the network which scans only one-dimensionally. The structure of the one-dimensional network is shown in Fig. 2(a). We decide to connect one amplifier (digitization circuit) to this one dimensional network constructed with edge detection circuits. When x-y unit circuits are arranged, y amps are needed. However, as compared with the approach of the previous motion detection circuit (Nishio et al. 2006 ; Yamada et al. 2001), the network structure is very simple. Each scan is controlled by the switches like CMOS image sensor. The signals of the network are shown in Fig. 2(b). Scanned edge signals are sequentially input to the amp. Simultaneously, digitized signal is sequentially input to the unit circuit for edge detection. We think that the motion detection circuit which inputs this digitized signal becomes simple structure. And, by designing the motion detection circuit constructed with only nMOS transistors like edge detection circuit, we think that the area of this circuit becomes small. 3.2 Model Figure 3 shows the transient response (Yamada et al. 2001) for motion detection. This transient response is shown based on the motion detection model in the vertebrate retina. Figure 3(a) shows the relationship between the unit circuit and the edge of the image. The edge passes on the unit circuit at velocity v. Figure 3(b) shows the transient response. When the edge passes on the unit circuit, the edge signal is generated. The retina generates the delay signal by this edge signal. The output signal like the signal constructed by the XOR circuit is generated. The pulse signal is generated when
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the edge moves on the unit circuit. Therefore, this pulsed signal is a motion signal. 3.3 Unit Circuit Figure 4 shows the structure of the proposed unit circuit for motion detection and the digitization circuit (amp) in Fig. 2(a). The edge detection circuit corresponds to the circuit in Fig. 1(b). The node d in Fig. 4 corresponds to that in Fig. 1(b). The nMOS transistor SW1 is a switch for controlling the scan. When V1 is about supply voltage VDD (=1), SW1 turns on, the output current of the edge detection circuit is input to the digitization circuit. Output terminals of other unit circuits are connected at node e. The current Ieout becomes more than the constant current Ith when the signal at edge from the circuit is input, and Veout becomes 0. Because Veout is input to CMOS inverter composed of pMOS transistor MP3 and nMOS transistor MN1. The voltage Vedge shows VDD (=1) when the signal at edge is input. Moreover, because Vedge is input to CMOS inverter composed of pMOS transistor MP4 and nMOS transistor MN2, the voltage Vdelay shows 0 when the signal at edge is input. Oppositely, Veout shows VDD(=1) when the signal at other position (at not edge) is input to digitization circuit , and Vdelay shows VDD (=1). Vedge and Vdelay are scanned by using nMOS transistors SW2 and SW3. When SW2 and SW3 turn on, Vedge and Vdelay are input. The latch circuit is constructed with capacitors C1 and
Fig. 3 Model for motion detection. (a) Relationship between the edge of the image and the unit circuit. (b) Transient response.
C2 and nMOS transistor SW4. The circuit like XOR is constructed with nMOS transistors Mm1 and Mm2. The input signal of Mm2 is latched voltage Vlatch of the first scanning. When the edge is projected on this unit circuit, Vlatch becomes about VDD (=1) and Mm2 turns on. Then, Vdelay is 0 and Mm1 turns off. Therefore, output current Iout is 0. If the edge moves when the signal of the next scan is input, the signal of delay becomes about VDD (=1). At this time, Mm1 turns on and Iout shows the constant current generated with Mm3 because Mm2 also turns on. Thus, this circuit is generated the constant current only when the edge moves on the unit circuit. 4. SIMULATION RESULTS 4.1 Simulation Condition The network for scanning edge signals and the proposed motion detection circuit were evaluated by SPICE. The model parameter of 1.5 μm CMOS technology (MOSIS, AMIS) was utilized in all simulations. The channel length and channel width of all transistors were set to 3 and 4.5 μm, respectively. In all simulations, the supply voltage was set to 5 V. 4.2 Network for Scanning Edge Signals It was confirmed whether the one-dimensional network in Fig. 2(a) operated normally. If one-dimensional network operates correctly we can believe that the whole network (two dimensional network) also operate normally. The network assumed that 50 edge detection circuits are arranged in onedimensionally was simulated. Ith was set to 20 nA.
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Fig. 4 Unit circuit for motion detection.
Figure 5(a) shows the provided input current (edge signal). Figure 5(b) shows the voltage of the clock for controlling the switches. Output voltages Vedge and Vdelay are shown in Figs. 5(c) and (d), respectively. Vedge showed about VDD when the input current was larger than Ith. Then, Vdelay showed about 0. We could confirm that the edge signals are sequentially output. Thus, the results with SPICE showed that the network operates normally. 4.3 Motion Detection Circuit We evaluated the proposed motion detection circuit by using SPICE. Vcon was set to the value that the current of 10 nA flows into Mm3. C1 and C2 are set to 10 pF and 1 pF, respectively. Figure 6 shows the relationship between the object and the unit circuits. It was assumed that the object passes on the unit circuit at the 100 μs.
Figure 7(a) shows the edge signal input to the unit1. Figure 7(b) shows the output current of unit1. In the moment that the edge of the object moves on the unit1, the circuit could generate the pulsed current (motion signal). The edge signal input to the unit2 is shown in Fig. 8(a). Figure 8(b) shows the output current of unit2. The circuit could generate the pulsed current when the edge of the object moves on the unit2. Figure 9(a) shows the edge signal input to the unit3. The output current of unit3 is shown in Fig. 9(b). The circuit could generate the pulsed current in the moment that the edge of the object moves on the unit3. Thus, it was clarified from the results with SPICE that the proposed circuits can generate motion signal. 5. DISCUSSION In this research, we proposed the novel motion detection circuit using the previous proposed edge detection circuit.
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Fig. 6 Relationship between unit circuits and edge of the image. 0
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The dynamic range against light intensity of this motion detection circuit is limited by the edge detection circuit at the first stage. The dynamic range of the edge detection circuit is about 5 decades (Nishio et al. 2008a). Before, we evaluated the circuit by SPICE. And the array of the circuits could detect edge positions of the image such as a soccer ball, a face and others with dynamic range of 5 decades. The dynamic range of the circuit by H. Yamada (2001) is about 3 decades. Thus, our circuit is characterized by the wide dynamic range. And our circuit is also characterized by low power consumption since all transistors constructing unit circuits are operated in the subthreshold region.
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The detection time of this motion detection circuit is determined by the width of movement signal. The width was about 8 μs. When the edge moves on the circuits for 8 μs or more. it is possible to generate the motion signal. Scan for one unit circuit was 8 μs. In case of one-dimentional network for 50 units, the time of scan was 400 μs. In future, we will propose the structure of 100×100 unit circuits. Based on the structure in Fig. 2(a), the structure of 100×100 unit circuits scan time becomes 800 μs. It is less than 1ms and faster than typical image processing system using present image sensor Input current (nA)
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Fig. 5 Simulation results of network for scanning edge signals. (a) Input current. (b) Voltages for controlling the switches. (c) Output voltage Vedge. (d) Output voltage Vdelay.
The unit circuit, as shown in Fig. 4, was constructed with only nMOS transistors by using the scanning function in Fig. 2. We can expect that the area of the unit circuit becomes half as compared with the circuit proposed by H. Yamada (2001).
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circuits. There was the problem of the large area and complex structure of the previous circuits. By using our circuits instead of previous circuits as the pre-processor, the realization of the simple circuit for collision avoidance and target tracking can be expected. Thus we can expect to realize the advanced vision chip by using our proposed circuit.
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In this study, the novel analog motion detection circuit was proposed by using previous proposed edge detection circuits, which is characterized by the wide dynamic range, low power consumption and compact structure. The proposed motion detection circuit was constructed with 6 nMOS transistors and 2 capacitors. The results with SPICE showed that the proposed circuit can generate the motion signal. The realization of the visual sensor in one chip, which is characterized by the high resolution, wide dynamic range and low power consumption can be expected by using the proposed circuits. REFERENCES
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(b) Fig. 9 Simulation results of unit3. (a) Input current. (b) Output current.
and previous proposed motion detection circuits (Mead 1989 ; Moini 1999 ; Yamada et al. 2001). Previously, we proposed the circuit for collision avoidance (Nishio et al. 2006, 2007) and the circuit for tracking the target (Nishio et al. 2008b). The previous proposed motion detection circuits were used as the pre-processor of these
Fossum, E. (1997), CMOS image sensors: Electronic cameraon-chip. IEEE Trans. Electron Devices, 44, 1689-1698. Mead, C. (1989) Analog VLSI and neural systems, Addison Wesley, Reading, MA. Moini, A. (1999), Vision chips, Kluwer Academic, Norwell, MA. Nishio, K., and Nakahara, H. (2008a) Simple Analog Metal Oxide Semiconductor Circuit for Edge Detection. Proc. of The Int. Conf. on Electrical Engineering 2008. Nishio, K., and Matsuzaka, K. (2008b) Target Tracking System Using Analog Circuit for Motion Detection. Proc. of 2008 IEEE Int. Conf. on Mechatronics and Automation, TC3-5. Nishio, K., Yonezu, H., and Furukawa, Y. (2007) Analog Vision Chip for Motion Detection of Approaching Object against Moving Background Based on Insect Visual System. Optical Review, 14, 111-119. Nishio, K., Yonezu, H., and Furukawa, Y. (2006) Analog Integrated Circuit for Detection of an Approaching Object with Simple-Shape Recognition Based on Lower Animal Vision. IEICE Trans. on Fundamentals of Electronics, Communications and Computer Sciences, E89-A, 416-427. Yamada, H., Miyashita, T., Ohtani, M., Nishio, K., Yonezu, H., and Furukawa, Y. (2001) Signal formation of imageedge motion based on biological retinal networks and implementation into an analog metal-oxide-silicon circuit. Optical Review, 8, 336-342.
using this circuit, it is able to realize the motion detection circuit with wide dynamic range. In this study, we tried to propose and design the compact motion detection circuit, which can easily connect with the previous proposed edge detection circuit as the pre-processor. The proposed circuit for generating the motion signal was mainly constructed with 6 nMOS transistors and 2 capacitors. The results with the simulation program with integrated circuit emphasis (SPICE) showed that the proposed circuit can generate the motion signal. 2. EDGE DETECTION CIRCUIT The edge detection circuit (Nishio et al 2008a) is shown in Fig. 1. Two-dimensional array of the edge detection circuits is shown in Fig. 1(a). The unit circuit is constructed with a photodiode (PD) and a processing circuit. Each unit circuit is connected with neighboring unit circuits. Figure 1(b) shows a unit circuit. The photodiode is used as the input part and the PD generates the current Ip which is proportional light intensity. The voltage Vp is changed by Ip. Nodes a, b and c of this circuit corresponds to those of a, b, and c in Fig. 1(a), respectively. These nodes are connected with neighboring unit circuits. The output voltage Vout is represented by the following equation. Vout = Vp − Vh .
(1)
Since the current Ih is changed by Idif at the nearest edge position, the voltage Vh is also changed. At the nearest edge position, the variance of Vh is large. Then, Vout becomes large and the output current Iout becomes large. Thus, the circuit can detect edge positions. This edge detection circuit was evaluated by SPICE. Figure 1(c) shows the simulation result. The circuit was arranged to
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The output signal of the edge detection circuit in Fig. 1 is used as the input signal of the motion detection circuit. However, because the edge signal is a small current, the motion detection circuit has a problem of incorrect operation due to noise and device mismatches. Therefore, we tried to amplify (digitize) the edge signals.
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Fig. 1 Previous proposed edge detection circuit. (a) Network structure. (b) Unit circuit. (c) Simulation result obtained by SPICE.
46×50. The result is represented by the image. As a result, it was confirmed that this edge detection circuit operated normally. Since this edge detection circuit constructed with only nMOS transistors is simple structure, low resolution can be expected in case of designing the integrated circuit. Because it is confirmed that there is dynamic range of 5 decades, the circuit is characterized by the wide dynamic range against light intensity. The circuit is characterized by the low power consumption since all MOS transistors constructing the circuit are operated in the subthreshold region. The edge detection circuit is often used as a pre-processor for the image processing system. It is necessary to propose the simple motion detection circuit that can connect with this excellent edge detection circuit.
Recently, the circuit for digitizing the edge signal was proposed (Nishio et al. 2006 ; Yamada et al. 2001). Each unit circuit for edge detection was connected with each digitization circuit. The connected circuit could operate normally. However, the unit circuit connecting the edge detection circuit, the digitization circuit and the circuit for generating the motion signal became large area, and the resolution became low. Since the digitization circuit is designed by CMOS circuit, the connected circuit loses the advantage of simple structure of the edge detection circuit constructed with only nMOS transistors. Thus, we considered to connect a digitization circuit to multiple edge detection circuits. As an easy way, x-y scan using the CMOS image sensor is considered. Based on this way, to make the process easier, we propose the network which scans only one-dimensionally. The structure of the one-dimensional network is shown in Fig. 2(a). We decide to connect one amplifier (digitization circuit) to this one dimensional network constructed with edge detection circuits. When x-y unit circuits are arranged, y amps are needed. However, as compared with the approach of the previous motion detection circuit (Nishio et al. 2006 ; Yamada et al. 2001), the network structure is very simple. Each scan is controlled by the switches like CMOS image sensor. The signals of the network are shown in Fig. 2(b). Scanned edge signals are sequentially input to the amp. Simultaneously, digitized signal is sequentially input to the unit circuit for edge detection. We think that the motion detection circuit which inputs this digitized signal becomes simple structure. And, by designing the motion detection circuit constructed with only nMOS transistors like edge detection circuit, we think that the area of this circuit becomes small. 3.2 Model Figure 3 shows the transient response (Yamada et al. 2001) for motion detection. This transient response is shown based on the motion detection model in the vertebrate retina. Figure 3(a) shows the relationship between the unit circuit and the edge of the image. The edge passes on the unit circuit at velocity v. Figure 3(b) shows the transient response. When the edge passes on the unit circuit, the edge signal is generated. The retina generates the delay signal by this edge signal. The output signal like the signal constructed by the XOR circuit is generated. The pulse signal is generated when
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the edge moves on the unit circuit. Therefore, this pulsed signal is a motion signal. 3.3 Unit Circuit Figure 4 shows the structure of the proposed unit circuit for motion detection and the digitization circuit (amp) in Fig. 2(a). The edge detection circuit corresponds to the circuit in Fig. 1(b). The node d in Fig. 4 corresponds to that in Fig. 1(b). The nMOS transistor SW1 is a switch for controlling the scan. When V1 is about supply voltage VDD (=1), SW1 turns on, the output current of the edge detection circuit is input to the digitization circuit. Output terminals of other unit circuits are connected at node e. The current Ieout becomes more than the constant current Ith when the signal at edge from the circuit is input, and Veout becomes 0. Because Veout is input to CMOS inverter composed of pMOS transistor MP3 and nMOS transistor MN1. The voltage Vedge shows VDD (=1) when the signal at edge is input. Moreover, because Vedge is input to CMOS inverter composed of pMOS transistor MP4 and nMOS transistor MN2, the voltage Vdelay shows 0 when the signal at edge is input. Oppositely, Veout shows VDD(=1) when the signal at other position (at not edge) is input to digitization circuit , and Vdelay shows VDD (=1). Vedge and Vdelay are scanned by using nMOS transistors SW2 and SW3. When SW2 and SW3 turn on, Vedge and Vdelay are input. The latch circuit is constructed with capacitors C1 and
Fig. 3 Model for motion detection. (a) Relationship between the edge of the image and the unit circuit. (b) Transient response.
C2 and nMOS transistor SW4. The circuit like XOR is constructed with nMOS transistors Mm1 and Mm2. The input signal of Mm2 is latched voltage Vlatch of the first scanning. When the edge is projected on this unit circuit, Vlatch becomes about VDD (=1) and Mm2 turns on. Then, Vdelay is 0 and Mm1 turns off. Therefore, output current Iout is 0. If the edge moves when the signal of the next scan is input, the signal of delay becomes about VDD (=1). At this time, Mm1 turns on and Iout shows the constant current generated with Mm3 because Mm2 also turns on. Thus, this circuit is generated the constant current only when the edge moves on the unit circuit. 4. SIMULATION RESULTS 4.1 Simulation Condition The network for scanning edge signals and the proposed motion detection circuit were evaluated by SPICE. The model parameter of 1.5 μm CMOS technology (MOSIS, AMIS) was utilized in all simulations. The channel length and channel width of all transistors were set to 3 and 4.5 μm, respectively. In all simulations, the supply voltage was set to 5 V. 4.2 Network for Scanning Edge Signals It was confirmed whether the one-dimensional network in Fig. 2(a) operated normally. If one-dimensional network operates correctly we can believe that the whole network (two dimensional network) also operate normally. The network assumed that 50 edge detection circuits are arranged in onedimensionally was simulated. Ith was set to 20 nA.
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Fig. 4 Unit circuit for motion detection.
Figure 5(a) shows the provided input current (edge signal). Figure 5(b) shows the voltage of the clock for controlling the switches. Output voltages Vedge and Vdelay are shown in Figs. 5(c) and (d), respectively. Vedge showed about VDD when the input current was larger than Ith. Then, Vdelay showed about 0. We could confirm that the edge signals are sequentially output. Thus, the results with SPICE showed that the network operates normally. 4.3 Motion Detection Circuit We evaluated the proposed motion detection circuit by using SPICE. Vcon was set to the value that the current of 10 nA flows into Mm3. C1 and C2 are set to 10 pF and 1 pF, respectively. Figure 6 shows the relationship between the object and the unit circuits. It was assumed that the object passes on the unit circuit at the 100 μs.
Figure 7(a) shows the edge signal input to the unit1. Figure 7(b) shows the output current of unit1. In the moment that the edge of the object moves on the unit1, the circuit could generate the pulsed current (motion signal). The edge signal input to the unit2 is shown in Fig. 8(a). Figure 8(b) shows the output current of unit2. The circuit could generate the pulsed current when the edge of the object moves on the unit2. Figure 9(a) shows the edge signal input to the unit3. The output current of unit3 is shown in Fig. 9(b). The circuit could generate the pulsed current in the moment that the edge of the object moves on the unit3. Thus, it was clarified from the results with SPICE that the proposed circuits can generate motion signal. 5. DISCUSSION In this research, we proposed the novel motion detection circuit using the previous proposed edge detection circuit.
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The dynamic range against light intensity of this motion detection circuit is limited by the edge detection circuit at the first stage. The dynamic range of the edge detection circuit is about 5 decades (Nishio et al. 2008a). Before, we evaluated the circuit by SPICE. And the array of the circuits could detect edge positions of the image such as a soccer ball, a face and others with dynamic range of 5 decades. The dynamic range of the circuit by H. Yamada (2001) is about 3 decades. Thus, our circuit is characterized by the wide dynamic range. And our circuit is also characterized by low power consumption since all transistors constructing unit circuits are operated in the subthreshold region.
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The detection time of this motion detection circuit is determined by the width of movement signal. The width was about 8 μs. When the edge moves on the circuits for 8 μs or more. it is possible to generate the motion signal. Scan for one unit circuit was 8 μs. In case of one-dimentional network for 50 units, the time of scan was 400 μs. In future, we will propose the structure of 100×100 unit circuits. Based on the structure in Fig. 2(a), the structure of 100×100 unit circuits scan time becomes 800 μs. It is less than 1ms and faster than typical image processing system using present image sensor Input current (nA)
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Fig. 5 Simulation results of network for scanning edge signals. (a) Input current. (b) Voltages for controlling the switches. (c) Output voltage Vedge. (d) Output voltage Vdelay.
The unit circuit, as shown in Fig. 4, was constructed with only nMOS transistors by using the scanning function in Fig. 2. We can expect that the area of the unit circuit becomes half as compared with the circuit proposed by H. Yamada (2001).
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circuits. There was the problem of the large area and complex structure of the previous circuits. By using our circuits instead of previous circuits as the pre-processor, the realization of the simple circuit for collision avoidance and target tracking can be expected. Thus we can expect to realize the advanced vision chip by using our proposed circuit.
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Fig. 8 Simulation results of unit2. (a) Input current. (b) Output current.
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In this study, the novel analog motion detection circuit was proposed by using previous proposed edge detection circuits, which is characterized by the wide dynamic range, low power consumption and compact structure. The proposed motion detection circuit was constructed with 6 nMOS transistors and 2 capacitors. The results with SPICE showed that the proposed circuit can generate the motion signal. The realization of the visual sensor in one chip, which is characterized by the high resolution, wide dynamic range and low power consumption can be expected by using the proposed circuits. REFERENCES
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6. CONCLUSIONS
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(b) Fig. 9 Simulation results of unit3. (a) Input current. (b) Output current.
and previous proposed motion detection circuits (Mead 1989 ; Moini 1999 ; Yamada et al. 2001). Previously, we proposed the circuit for collision avoidance (Nishio et al. 2006, 2007) and the circuit for tracking the target (Nishio et al. 2008b). The previous proposed motion detection circuits were used as the pre-processor of these
Fossum, E. (1997), CMOS image sensors: Electronic cameraon-chip. IEEE Trans. Electron Devices, 44, 1689-1698. Mead, C. (1989) Analog VLSI and neural systems, Addison Wesley, Reading, MA. Moini, A. (1999), Vision chips, Kluwer Academic, Norwell, MA. Nishio, K., and Nakahara, H. (2008a) Simple Analog Metal Oxide Semiconductor Circuit for Edge Detection. Proc. of The Int. Conf. on Electrical Engineering 2008. Nishio, K., and Matsuzaka, K. (2008b) Target Tracking System Using Analog Circuit for Motion Detection. Proc. of 2008 IEEE Int. Conf. on Mechatronics and Automation, TC3-5. Nishio, K., Yonezu, H., and Furukawa, Y. (2007) Analog Vision Chip for Motion Detection of Approaching Object against Moving Background Based on Insect Visual System. Optical Review, 14, 111-119. Nishio, K., Yonezu, H., and Furukawa, Y. (2006) Analog Integrated Circuit for Detection of an Approaching Object with Simple-Shape Recognition Based on Lower Animal Vision. IEICE Trans. on Fundamentals of Electronics, Communications and Computer Sciences, E89-A, 416-427. Yamada, H., Miyashita, T., Ohtani, M., Nishio, K., Yonezu, H., and Furukawa, Y. (2001) Signal formation of imageedge motion based on biological retinal networks and implementation into an analog metal-oxide-silicon circuit. Optical Review, 8, 336-342.