JP2013034043A - Signal transmitter - Google Patents

Abstract

【Task】
In a system that optically transmits a signal from a rotating part that can rotate relative to a fixed part to the fixed part, fluctuations in the received light level due to optical axis misalignment are reduced.
[Solution]
The LED circuit (101) faces the photodiode (106) in a mechanism that rotatably supports the rotating part (122) with respect to the fixed part (121). In the measurement mode, the control unit (134) of the rotation unit (122) drives the LED circuit (101) with a constant current at a predetermined rotation angle position. The control unit (153) of the fixed unit (121) measures the light reception level at each rotation angle position from the output of the photodiode (106), and stores the angle dependency in the EEPROM (154). During rotation, the rotating unit (122) transmits the rotation angle position to the fixed unit (121). The control unit (153) of the fixed unit (121) controls the amplification factor of the amplification circuit (150) that amplifies the output of the photodiode (106) to an amplification factor corresponding to the rotation angle position.
[Selection] Figure 1

Description

  The present invention relates to a signal transmission device that transmits a signal via a rotation mechanism, and more specifically to a signal transmission device that transmits a signal between a fixed portion and a rotation portion of a rotation mechanism that can rotate endlessly. .

  Conventionally, in a device having a rotation mechanism that can rotate endlessly, signal transmission between the fixed portion and the rotation portion is based on a signal transmission method using a slip ring and optical coupling between the light emitting element and the light receiving element. Optical transmission systems are known.

  In the slip ring system, since the signal is transmitted while the fixed brush slides on the slip ring, the impedance rises due to noise generation due to mechanical contact or long-term continuous sliding. As a result, signal transmission performance deteriorates particularly in high-frequency transmission of video signals and the like.

  Since the optical transmission system has no mechanical contact, noise associated with the mechanical contact is not generated, and transmission performance is not deteriorated due to an increase in impedance. However, when the optical axis between the light emitting element and the light receiving element is displaced, the signal transmission performance deteriorates. In Patent Document 1, a hollow cylindrical light guide plate is provided between the light emitting element arranged in the rotating part and the light receiving element arranged in the fixed part so that the output light of the light emitting element is guided to the light receiving element regardless of the rotation. The structure which was made is described.

JP 2008-154207 A

  The configuration described in Patent Document 1 has a problem that the light guide plate on the hollow cylinder not only causes an increase in cost, but also increases the size of the apparatus.

  An object of this invention is to show the signal transmission apparatus of the optical transmission system which does not use a light-guide plate.

  A signal transmission device according to the present invention is a signal transmission device that transmits a signal from a rotating unit that is rotatable with respect to a fixed unit to the fixed unit, and is arranged in the rotating unit and transmits an optical signal that carries the signal. A light emitting element that outputs, a light receiving element that is disposed in the fixed portion and receives the optical signal, a receiving means that receives the signal from an output of the light receiving element, and a plurality of rotational positions of the rotating portion relative to the fixed portion And the storage means for storing the drive level of the light emitting element or the reception characteristic of the receiving means, and the drive of the light emitting element with reference to the storage means according to the current rotational position of the rotating part with respect to the fixed part And control means for controlling the level or the receiving characteristic of the receiving means so as to reduce a change according to the rotational position.

  According to the present invention, even when the optical axis relationship between the light-emitting element and the light-receiving element for light transmission varies due to the rotation of the rotating part, good light transmission can be realized.

1 shows a schematic block diagram of a turning camera incorporating an embodiment of the present invention. FIG. It is center sectional drawing which shows the turning structure of a turning camera. It is an example of a waveform when there exists a shift | offset | difference in the optical axis of LED and a photodiode. 1 is a schematic configuration diagram of a network camera system using the present embodiment. It is a flowchart which shows the processing content of the rotation part in a measurement mode, and a fixing | fixed part. It is a circuit example of an amplifier circuit. It is a circuit example of a peak hold circuit. It is a circuit example of a binarization circuit. 7 is a table showing the relationship between the resistance value and amplification factor of the amplifier circuit shown in FIG. 6. It is an example of the relationship between the input voltage and output voltage of an amplifier circuit. It is an example of a stored value of EEPROM. It is a flowchart which shows the processing content of the rotation part and fixed part with respect to a pan command. It is a circuit block diagram of the binarization circuit which changed the threshold voltage according to the rotation angle. This is an example of storage in the EEPROM 154 when the threshold voltage is changed according to the rotation angle. It is an example of an output waveform of the photodiode when the binary discrimination threshold is fixed and when it is changed depending on the rotation angle. It is a flowchart of the pan rotation process when the threshold voltage is changed according to the rotation angle. It is a circuit example of the LED circuit in the case of changing the drive current of LED depending on a rotation angle. This is an example of storage in the EEPROM 154 when the LED drive current is changed depending on the rotation angle. It is an example of an output waveform of the photodiode when the driving current of the LED is constant and when it is changed depending on the rotation angle. It is a schematic block diagram of the Example which has arrange | positioned the means to rotationally drive a rotation part, and a rotation position detection means to the fixing | fixed part. It is a schematic block diagram of the optical transmission system which added the optical transmission means from a fixing | fixed part to a rotation part.

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

  FIG. 1 shows a schematic block diagram of a turning camera incorporating an embodiment of the present invention. FIG. 4 shows a schematic configuration diagram of a network camera system using the present embodiment.

  Reference numeral 129 denotes a turning camera configured as shown in FIG. Reference numeral 121 denotes a fixed part of the turning camera 129, which is mounted on a wall or ceiling when used as a surveillance camera. A rotating unit 122 of the turning camera 129 rotates in the horizontal direction (pan direction) in response to a pan control command from the viewer 128 connected via the network 126. As will be described later, the rotating unit 122 can endlessly rotate about a predetermined axis of the fixed unit 121 as a rotation center.

  Reference numeral 123 denotes a photographing lens. The optical image obtained by the photographing lens 123 is photoelectrically converted, data-compressed, and optically transmitted from the rotating unit 122 to the fixed unit 121.

  A network connector 124 is connected to the network 126 via the network cable 125. The fixing unit 121 converts the video signal optically transmitted from the rotating unit 122 into a signal that can be transmitted over the network, and transmits the signal to the personal computer 128 via the network 126. The network cable 125 is connected to the network 126 via a hub (not shown). The network 126 includes, for example, the Internet.

  A personal computer (hereinafter abbreviated as a personal computer) 128 as a viewer for viewing images from the turning camera 129 is connected to the network 126 via a network cable 127. The personal computer 128 receives the compressed video signal from the turning camera 129 via the network 126 and displays it. Application software (viewer) for controlling the shooting direction of the turning camera 129 is installed in the personal computer 128. For example, the user can specify the imaging direction with a scroll bar in a window displayed by the viewer on the monitor screen of the personal computer 128. The viewer transmits a pan control command for instructing rotation in the designated shooting direction to the turning camera 129 via the network 126. The viewer displays an icon indicating the measurement mode, and the user selects an icon corresponding to the measurement mode to be designated. The viewer generates a measurement command corresponding to the selected icon and transmits it to the turning camera 129 via the network 126.

  FIG. 2 is a central sectional view showing a turning structure of the turning camera 129. FIG. 2A shows a case where the light axes of the light transmission system and the light receiving element of the slip ring coincide with each other. FIG. 2B shows a case where the optical axis of the light emitting element is inclined with respect to the light receiving element.

  In FIG. 2A, reference numerals 101 to 104 denote components in the rotating unit 122 of the turning structure. Reference numerals 105 to 109 indicated by hatching are components in the fixed portion 121 of the turning structure. The rotating part 122 has a structure that can rotate endlessly in the horizontal direction (pan direction) with respect to the fixed part 121.

  Reference numeral 101 denotes an LED circuit having a light emitting diode (LED) as a light emitting element, and generates an optical signal for carrying a compressed video signal from the rotating unit 122 in a band of about 100 MHz. Reference numeral 102 denotes a slip ring, which electrically connects the power line of the fixed part 121 and the power line of the rotating part 122. A control command such as a pan control command of about 100 kHz is superimposed on the power line of the fixed unit 121. By setting the frequency to about 100 kHz, the control command signal is stably transmitted from the fixed unit 121 to the rotating unit 122 via the slip ring 102.

  Reference numeral 103 denotes a mold part that supports the components arranged in the rotating unit 122. Reference numeral 104 denotes a printed circuit board of the rotating unit 122, on which electrical components that realize the functional blocks shown in FIG. 1 are mounted.

  Reference numeral 105 denotes a mold part of the fixed part 121, and supports the entire rotating part 122 by supporting the mold part 103 of the rotating part 122. The joint portion of the mold part 105 of the fixed part 121 and the mold part 103 of the rotating part 122 may be point-contacted with ribs so that the pan can be easily rotated. Moreover, you may make it the structure which reduces friction using a bearing.

  Reference numeral 106 denotes a photodiode as a light receiving element, which receives signal light output from the LED of the LED circuit 101 and converts it into an electrical signal. Reference numeral 107 denotes a light receiving surface of the photodiode 106.

  Reference numeral 108 denotes a printed circuit board of the fixing unit 121, on which electrical components that realize the functional blocks shown in FIG. 1 are mounted.

  Reference numeral 109 denotes a brush that is in sliding contact with the slip ring 102, and applies a power supply voltage and a control command from the fixing unit 121 to the slip ring 102.

  By adopting the rotating structure shown in FIG. 2A, the rotating unit 122 can perform endless rotation of 360 degrees or more with respect to the fixed unit 121, but can transmit signals and supply power at any rotation angle. Become.

  As shown in FIG. 2A, the LED circuit 101 is on the rotation center axis of the rotating unit 122, and outputs signal light toward the light receiving surface 107 of the photodiode 106 along the rotation center axis. Therefore, the output light of the LED circuit 101 enters the photodiode 106 regardless of the angle at which the rotating unit 122 rotates.

  In the cross-sectional view shown in FIG. 2B, the LED of the LED circuit 101 is mounted in an inclined state, and the mounting position of the photodiode 106 is shifted to the right. In this arrangement example, for example, the light receiving surface 107 of the photodiode 106 exists at an angular position 110 inclined to the right by about 40 degrees from the output optical axis of the LED circuit 101. Only a part of the output light of the LED circuit 101 enters the photodiode 106. In the LED circuit 101 used in the present embodiment, the amount of light is reduced by 60% at an inclination of 40 degrees.

  FIG. 2C shows the positional relationship between the LED of the LED circuit 101 and the photodiode 106 when the pan is rotated 180 ° in the case of the arrangement shown in FIG. The light receiving surface 107 of the photodiode 106 is positioned at an angular position 111 inclined about 20 degrees to the left from the output optical axis of the LED of the LED circuit 101. Due to the shifted incidence, the incident light amount of the photodiode 106 is reduced by, for example, about 30% compared to the case where the optical axis is aligned.

  FIG. 3A shows the output current of the photodiode 106 according to the pan rotation angle when a constant current is applied to the LED of the LED circuit 101. Reference numeral 170 denotes the output current of the photodiode 106 when the LED of the LED circuit 101 and the optical axis of the photodiode 106 are aligned as shown in FIG. Reference numeral 171 denotes the output current of the photodiode 106 when the LEDs of the LED circuit 101 and the optical axis of the photodiode 106 are tilted as shown in FIGS. The magnitude of the current 171 varies with respect to the pan angle, and is maximized at the position 172 and minimized at the position 173. The position 173 corresponds to, for example, the positional relationship shown in FIG. 2B, and the position 172 corresponds to the positional relationship shown in FIG.

  FIG. 3B shows an example of a change in the output current of the photodiode 106 at positions corresponding to the positions 172 and 173 when the LED of the LED circuit 101 is pulse-driven in the measurement mode. Reference numeral 175 denotes a measurement signal (pulse current) applied to the LED of the LED circuit 101. Reference numeral 176 denotes the output current of the photodiode 106 at the position 172. Reference numeral 177 denotes the output current of the photodiode 106 at the position 173.

  In the present embodiment, by adopting the following configuration, even when the output current level of the photodiode 106 fluctuates according to the pan angle position, optical transmission can be performed without any trouble. With reference to FIG. 1, the configuration and operation for that purpose will be described in detail.

  In the rotation unit 122, the imaging unit 130, which is a video signal generation unit, converts the optical image from the lens 123 into a video signal of a predetermined format. The imaging unit 130 includes an imaging device that converts an optical image into an image signal, and a camera signal processing circuit that performs known camera signal processing such as color balance adjustment and γ correction on an output image signal of the imaging device. The compression circuit 131 converts the video signal output from the imaging unit 130 into MPEG or H.264. The video is compressed by a moving image compression method such as H.264, and a packetized compressed video signal is generated. The packetized compressed video signal has a code END CODE indicating the end of the packet. The control unit 134 detects the end of each packet by the packet end code END CODE. In the following description, the output signal of the compression circuit 131 is expressed as a packet signal.

  The control unit 134 of the rotation unit 122 outputs pan angle information to the synthesis circuit 132 in response to a request from the fixing unit 121 or periodically. The synthesizing circuit 132 inserts the control / status signal from the control unit 134 between the packet signals from the compression circuit 131 and outputs it to the transmission circuit 133. That is, the synthesis circuit 132 is a time division multiplexing circuit that time division multiplexes the signal from the control unit 134 to the packet signal. However, when receiving the measurement signal 175 from the control unit 134 in the measurement mode, the synthesis circuit 132 prohibits the packet signal output and outputs only the measurement signal 175 to the transmission circuit 133.

  The transmission circuit 133 converts the output signal of the synthesis circuit 132 input in parallel into a serial signal and supplies the serial signal to the LED circuit 101. The LED circuit 101 converts the output signal of the transmission circuit 133 into an optical signal and emits it toward the photodiode 106.

  The power supply circuit 139 supplies a necessary power supply voltage to each part of the rotating unit 122 based on the power supplied from the power supply circuit 159 of the fixed unit 121 via the slip ring 102.

  The control unit 134 controls acceleration / deceleration of pan rotation by the pan rotation driving unit 136 in accordance with a pan control signal received from the fixing unit 121 via the slip ring 102. The control unit 134 controls pan rotation in accordance with the rotational position information from the rotational position detection mechanism 138, generates pan angle information, and transmits the pan angle information to the combining circuit 132. The control unit 134 also generates a measurement signal according to the measurement mode signal received from the fixing unit 121 via the slip ring 102 and supplies the measurement signal to the synthesis circuit 132. The storage unit 135 stores variables and the like necessary for the control of the control unit 134.

  The pan rotation driving unit 136 generates a pulse signal according to the control signal from the control unit 134, amplifies the current, and outputs the amplified signal to the pan rotation mechanism 137. The pan rotation mechanism 137 includes a pulse motor, and rotates the rotation unit 122 relative to the fixed unit 121 in accordance with a pulse signal from the pan rotation drive unit 136.

  The rotational position detection mechanism 138 includes a means for detecting the home position and a means for detecting the rotational position, and transmits position information corresponding to the pan rotation to the control unit 134.

  The configuration and basic operation of the fixing unit 121 will be described.

  The photodiode 106 receives the optical signal from the LED circuit 101 and outputs a corresponding electrical signal. The amplifier circuit 150 converts the output current of the photodiode 106 into a voltage, and amplifies the voltage with an amplification factor controlled by the control unit 153 according to the rotation angle. Details of the amplifier circuit 150 will be described later with reference to FIG.

  The peak hold circuit 151 converts the voltage of the output current of the photodiode 106 and detects the peak voltage. The reason why the peak voltage is detected is that, as shown in FIG. 3B, the output current of the photodiode 106 is a waveform obtained by integrating the pulse waveform. The peak hold circuit 151 supplies the detected peak voltage value to the control unit 153. Details of the peak hold circuit 151 will be described later with reference to FIG.

  The binarization circuit 152 binarizes the output signal of the amplifier circuit 150 with a predetermined threshold. The binarized signal generated by binarization is supplied to the pulse transformer 156 and the control unit 153. The control unit 153 controls the binarization circuit so that the generated binarization signal is not output to the pulse transformer 156 at the start of the measurement mode. Details of the binarization circuit 152 will be described later with reference to FIG.

  The control unit 153 stores the pan angle information transmitted from the rotation unit 122 in the measurement mode in the EEPROM 154. The controller 153 digitizes the peak voltage value output from the peak hold circuit 151 and calculates the amplification factor of the amplifier circuit 150. The control unit 153 stores the calculated amplification factor in the EEPROM 154 together with the rotation angle of the rotation unit 122. The control unit 153 also receives command signals such as pan control commands and measurement commands transmitted from the viewer 128 and transfers them to the signal superimposing circuit 158.

  The signal superimposing circuit 158 superimposes the command signal from the control unit 153 on the power source at a low frequency of about 100 KHz, and supplies the power signal to the slip ring 102 of the rotating unit 122 via the brush 109. Although the impedance of the slip ring 102 increases when used for a long time, if it is about 100 KHz, there is no problem in transmission.

  The pulse transformer 156 impedance-separates the binarized signal from the binarization circuit 152 and transfers it to the network connector 124. The pulse transformer 156 also impedance-separates a signal (for example, a command from the viewer) from the network connector 124 and transfers the signal to the reception PHY 157. A network cable 125 is connected to the network connector 124 and communicates with the viewer 128 via the network 126.

  The reception PHY 157 performs voltage conversion and serial / parallel conversion on the signal from the pulse transformer 156 and supplies the signal to the control unit 153.

  The power supply circuit 159 disposed in the fixing unit 121 supplies power to the circuit elements of the fixing unit 121 and supplies power to the rotating unit 122 via the signal superimposing circuit 158, the brush 109, and the slip ring 102. The brush 109 is in physical contact with the slip ring 102 and maintains an electrical connection with the slip ring 102 at all times.

  FIG. 6 shows details of the amplifier circuit 150 and an internal circuit of the control unit 153 related to the amplifier circuit 150.

  The photodiode 106 generates a current in the direction from the cathode CAT to the anode ANO when an optical signal from the LED of the LED circuit 101 enters. The resistor R9 converts the current generated in the photodiode 106 into a voltage. The DC coupling capacitor C5 removes the DC component of the generated voltage and transmits only the AC component to the operational amplifier A2. The circuit composed of the operational amplifier A2 and the resistors R5 to R8 constitutes a non-inverting amplifier circuit.

When the input voltage of the operational amplifier A2 is Vi2, and the combined resistance value of the resistors R5, R6, and R7 is Rp2, the output voltage Vo2 of the operational amplifier A2 is
Vo2 = (R8 + Rp2) / Rp2 × Vi2
It is represented by

  The port control register 185 of the control unit 153 controls on / off of the field effect transistors F5, F6, and F7. By this control, the amplification factor of the non-inverting amplifier circuit composed of the operational amplifier A2 can be changed. FIG. 9 shows the relationship between the resistance value and the amplification factor. Column 194 shows the resistances turned on (connected to ground) by field effect transistors F5, F6, F7. In FIG. 9, the resistance values of the resistors R5, R6, and R7 are R5 = 2KΩ, R6 = 3KΩ, and R7 = 4KΩ, respectively. A column 191 shows the value of the combined resistance Rp2. A column 192 shows the amplification factor of the non-inverting amplifier circuit. A column 193 indicates a range of the input voltage Vi2 detected by the peak hold circuit 151. The control unit 153 controls on / off of the field effect transistors F5, F6, and F7 so that the amplification factor shown in the column 192 is selected for the current range shown in the column 193.

  FIG. 10 shows the relationship between the input voltage Vi2 and the output voltage Vo2 when the amplification factor shown in the column 192 is used. When the input voltage is in the range of 30 mV to 120 mV, the output voltage Vo2 is in the range of 340 mV to 500 mV. The amplifier circuit 150 can output a voltage that can be binarized by the binarization circuit 152.

  The CPU 181 as a central processing circuit of the control unit 153 controls the control unit 153 itself and each unit by processing and executing micro instructions stored in the ROM 182 one after another. The ROM 182 stores microinstructions, and the RAM 183 stores variables used when the CPU 181 processes.

  A bus line 184 transmits data among the CPU 181, ROM 182, RAM 183, EEPROM 154, and port control register 185. The CPU 181 stores the control values for turning on / off the field effect transistors F5 to F7 in the port control register 185, thereby controlling the field effect transistors F5 to F7.

  In the EEPROM 154, amplification factors to be applied for a plurality of pan rotation angles are stored as one element of reception characteristics. FIG. 11 shows an example of values stored in the EEPROM 154. The EEPROM 154 stores the correspondence between the input voltage Vi2 and the resistance to be turned on in increments of 10 °.

  In the case where the input voltage Vi2 shows a distribution similar to that shown in the current 171 (FIG. 3), 57 mV at a rotation angle of 0 °, 65 mV at a rotation angle of 10 °, 90 mV at a rotation angle of 180 °, and a rotation angle of 350 °. Is assumed to be 65 mV. The amplification factors are 6.9, 6, 4.3, and 6 from the table shown in FIG. The resistors to be turned on are resistors R6 and R7 at 0 °, resistors R5 at 10 °, resistors R6 at 180 °, and resistors R5 at 350 °.

  The CPU 181 recalls the content stored in the EEPROM 154 and controls on / off of the field effect transistors F5 to F7 in order to obtain an amplification factor corresponding to the pan rotation angle.

  FIG. 7 shows a circuit example of the peak hold circuit 151. The resistor R1 and the capacitor C1 constitute an integrating circuit and remove noise generated at the cathode of the photodiode 106. The diode D1 causes a current to flow when the output of the operational amplifier A1 becomes higher than the output voltage 187, charges the capacitor C2, and increases the output voltage. The resistor R2 is a discharging resistor. The voltage 187 is a peak detection voltage value and is supplied to the control unit 153.

  The control unit 153 includes an AD converter 188 that converts the voltage value 187 into a digital value. The CPU 181 of the control unit 153 stores the output voltage value of the peak hold circuit 151 in the EEPROM 154 as a detection voltage corresponding to the rotation angle. “Detected voltage” in the table shown in FIG. 11 indicates a voltage value detected by the peak hold circuit 151.

  FIG. 8 shows a circuit example of the binarization circuit 152. The operational amplifier A11 outputs a high voltage when the output voltage of the amplifier circuit 150 is higher than the threshold voltage V10, and outputs a low voltage when the output voltage is lower than the threshold voltage V10. The resistors R10 and R11 are arranged to have a hysteresis characteristic.

  The output of the operational amplifier A11, that is, the binarized signal is supplied to the pulse transformer 156 via the switch SW10. The switch SW10 is controlled by the control unit 153 to be in a connected state or a closed state when transmitting a video signal, and to be in a non-connected state or an open state during a measurement mode or the like. In the measurement mode, since the output of the binarization circuit 152 does not indicate a video signal, the switch SW10 is opened or turned off. When SW10 is off, external output is prohibited.

  FIG. 5 is a flowchart showing the processing contents of the rotating unit 122 and the fixed unit 121 when an instruction to start the measurement mode is received from the viewer 128. The left side shows the process of the fixed unit 121, and the right side shows the process of the rotating unit 122.

  In step S200, the control unit 153 of the fixing unit 121 receives an instruction to start the measurement mode from the viewer 128 via the network. In step S201, the control unit 153 notifies the rotation unit 122 of the transition to the measurement mode. As described above, the control unit 153 generates a measurement command and transmits the measurement command to the control unit 134 of the rotating unit 122 via the signal superimposing circuit 158, the brush 109, and the slip ring 102.

  In step S202, the control unit 134 controls the imaging unit 130 and the compression circuit 131 to be in a stopped state so as not to output a video signal.

  In step S <b> 203, the fixed unit 121 transmits a home position command to the rotating unit 122.

  In step S207, the control unit 153 switches the switch SW10 to an open state so that the output signal of the binarization circuit 152 is not output to the network 126.

  When receiving the home position command, the control unit 134 of the rotation unit 122 rotates the pan rotation mechanism 137 in step S204.

  In step S205, the control unit 134 detects whether or not the home position has been reached based on the output of the rotational position detection mechanism 138. The control unit 134 repeats steps S204 and 205 until the home position is detected.

  When the home position is detected in step S205, in step S206, the control unit 134 generates a measurement signal 175 (FIG. 3B) and causes the LED circuit 101 to generate an optical signal. In the fixing unit 121, the photodiode 106 receives the optical signal from the LED circuit 101, photoelectrically converts it, and supplies it to the peak hold circuit 151. In step S208, the peak hold circuit 151 detects the peak voltage. The control unit 153 takes in the detected voltage value.

  In step S209, the control unit 153 stores the detected voltage corresponding to the rotation angle in the EEPROM 154 as shown in FIG.

  In step S210, the control unit 153 refers to the table shown in FIG. 9 and designates the amplification factor based on the detected voltage and the resistance to be turned on. For example, if the detected voltage is 57 mA, it is specified from the table shown in FIG. 9 that the resistors R6 and R7 are turned on.

  In step S211, the control unit 153 stores the designated resistance in the EEPROM 154 as shown in FIG. In step S212, the control unit 153 determines whether or not the pan angle is 350 degrees. If the pan angle is less than 350 degrees, the control unit 153 proceeds to step S213.

  In step S213, the control unit 153 generates a pan rotation command. In this embodiment, the pan rotation command is generated so that the pan rotation is performed by 10 degrees.

  By repeating step S208 to step S213, the control unit 153 completes a table showing the correspondence between the rotation angle, the detected voltage, and the designated resistance in the EEPROM 154 as shown in FIG.

  In step S214, the control unit 134 of the rotation unit 122 receives the pan rotation command and stops the measurement signal. In step S215, the control unit 134 rotates the pan rotation mechanism 137. In step S216, when detecting that the rotational position detection mechanism 138 has rotated 10 degrees, the control unit 134 stops the pan driving by the pan rotation mechanism 137, and returns to step S206 to output a measurement signal.

  The reason why the measurement signal is stopped in step S214 during pan rotation is to prevent erroneous detection in the peak hold circuit 151 of the fixed unit 121.

  In step S212, when the control unit 153 detects that the pan angle has reached 350 degrees, the control unit 153 proceeds to step S230 and transmits a measurement mode end notification to the rotation unit 122. In response to the measurement mode end notification, the control unit 134 of the rotating unit 122 stops the measurement signal in step S232. In step S234, the control unit 134 of the rotation unit 122 generates a measurement mode end signal and transmits the measurement mode end signal to the fixed unit 121 and the viewer 128. In step S235, the control unit 134 activates the image capturing unit 130 and the compression circuit 131 to enable output of a video signal.

  On the other hand, in step S233, the control unit 153 of the fixing unit 121 turns the SW 10 on. As a result, the fixing unit 121 can transmit a signal from the rotating unit 122 to the viewer 128 via the network 126.

  In this embodiment, the measurement mode is executed by a measurement command from the viewer 128, but may be executed when the turning camera 129 is turned on.

  FIG. 12 is a flowchart showing a processing procedure when the turning camera 129 receives a pan command from the viewer 128 via the network 126. The left side shows the process of the fixed unit 121, and the right side shows the process of the rotating unit 122.

  When the control unit 153 of the fixed unit 121 receives the pan command in step S250, the control unit 153 transfers the pan command to the control unit 134 of the rotation unit 122 in step S251.

  In step S252, the control unit 134 of the rotation unit 122 causes the pan rotation mechanism 137 to perform pan rotation according to the pan command. In step S253, the control unit 134 determines the end of the packet by detecting the packet end code END CODE of the packet signal output from the compression circuit 131. When the packet end code is detected, in step S269, the control unit 134 controls the compression circuit 131 so as to temporarily stop transmission of the packet signal generated by the compression circuit 131 to the synthesis circuit 132. The compression circuit 131 has storage means (not shown) inside, and temporarily holds a packet signal that is generated but not output.

  In step S254, the control unit 134 obtains position information from the rotational position detection mechanism 138 and generates pan angle information. In step S <b> 255, the control unit 134 transmits the generated pan angle information to the fixing unit 121.

  In step S256, the control unit 153 of the fixed unit 121 detects the code END CODE and determines the end of the packet. Specifically, the control unit 153 detects the code END CODE from the packet signal binarized by the binarization circuit 152.

  In step S257, the control unit 153 turns off SW10 of the binarization circuit 152. By turning off SW10, the pan angle information is not transmitted to the pulse transformer 156 and is therefore not output to the network 126.

  In step S258, the control unit 153 takes in the pan angle information transmitted from the rotation unit 122 in step S255. In step S259, the control unit 153 refers to the table stored in the EEPROM 154 according to the flow shown in FIG. 5, and designates a resistance corresponding to the pan angle. That is, the control unit 153 reads the control value (in this case, the amplification factor) corresponding to the current rotation position of the rotation unit 122 from the EEPROM 154.

  For example, when the pan angle is 0 °, the resistors R6 and R7 are designated according to FIG. In step S260, control unit 153 sets a predetermined value in port control register 185 so that the field effect transistor corresponding to the designated resistance is turned on. For example, when the resistors R6 and R7 are designated, the field effect transistors F6 and F7 are turned on.

  The amplifier circuit shown in FIG. 6 converts the output current of the photodiode 106 into a voltage and amplifies it with the amplification factor shown in FIG. For example, when the resistors R6 and R7 are turned on, the control unit 153 sets the gain 6.9 in the amplifier circuit shown in FIG.

  In step S261, the control unit 153 turns on SW10 of the binarization circuit 152.

  In step S262, the control unit 153 requests the rotation unit 122 for a packet. In response to this request, in step S263, the control unit 134 of the rotating unit 122 starts transmitting the packet signal suspended in step S269. In step S264, the control unit 153 of the fixed unit 121 starts receiving a packet from the rotating unit 122. In the fixing unit 121, the amplifier circuit 150 amplifies the received signal at an amplification factor according to the pan angle position. By setting the amplification factor, good signal transmission characteristics can be realized even if there is a deviation in the optical axis between the LED of the LED circuit 101 and the photodiode 106 as described with reference to FIGS. The fixing unit 121 transmits the video information transmitted in the received packet to the viewer 128 via the network 126.

  In step S265, the control unit 153 determines the end of the packet. The packet reception is continued until the packet transmission is completed.

  When the packet transmission ends, the control unit 153 turns off the SW10 of the binarization circuit 152 in step S266. On the other hand, in step S267, the control unit 134 of the rotating unit 122 determines the end of the packet as in step S265. The packet transmission is continued until the packet transmission is completed.

  When the packet transmission ends, in step S268, the control unit 134 determines whether or not to end the pan driving. That is, it is determined whether or not the rotation operation by the pan rotation mechanism 137 has been completed. If the rotation operation by the pan rotation mechanism 137 has not been completed, the control unit 134 returns to step S269 and executes generation and transmission of pan angle information, pan rotation, and transmission of a packet signal. If the rotation operation by the pan rotation mechanism 137 has ended, the control unit 134 transmits pan end information to the fixed unit 121 in step S270.

  In step S271, the control unit 153 of the fixing unit 121 determines reception of pan end information. When the pan end information has not been received, the control unit 153 repeats the processes of steps S258 to S271. That is, the amplification factor of the amplifier circuit 150 is adjusted according to the pan angle position, and the packet signal from the rotating unit 122 is received. On the other hand, when the pan end information is received, the control unit 153 turns on SW10 of the binarization circuit 152 in step S272. This is because the packet signal transmitted from the rotation unit 122 after the pan rotation is completed is repeatedly transmitted to the viewer 128 via the network 126.

  In the present embodiment, the power source and the command signal are transmitted from the fixed unit 121 to the rotating unit 122 using the slip ring 102 and the brush 109. However, a power supply and a command signal may be transmitted using a moving transformer.

  In this embodiment, the amplification factor corresponding to the pan angle is stored in the EEPROM 154 which is a nonvolatile memory as an element of the reception characteristics, but may be stored in a RAM which is a volatile memory. Alternatively, the measurement mode may be automatically executed when the turning camera is turned on / off, and the amplification factor corresponding to the pan angle may be stored in the volatile memory.

  An embodiment in which the binary discrimination threshold of the output signal of the photodiode 106 is changed according to the rotation angle will be described.

  FIG. 15A shows a timing chart when the binary discrimination threshold of the output signal of the photodiode is fixed. FIG. 15B shows a timing chart when the binary discrimination threshold of the output signal of the photodiode is changed depending on the rotation angle.

  In FIG. 15A, reference numeral 310 denotes a transmission signal or drive signal applied to the LED of the LED circuit 101. Reference numerals 311 and 312 denote signals obtained by converting the output current of the photodiode 106 into voltage. Reference numeral 311 denotes a signal waveform when the amount of light is large, and 312 denotes a signal waveform when the amount of light is small. Reference numerals 313 and 314 denote threshold voltages for binary discrimination of the signals 311 and 312. In FIG. 15A, the threshold voltages 313 and 314 are equal to each other, and are set to a substantially intermediate value with respect to the mark / space of the signal 313. In the example illustrated in FIG. 15A, the threshold voltage 314 is too high for the signal 312, and thus binary discrimination cannot be performed correctly.

  On the other hand, FIG. 15B shows a waveform example of this embodiment in which the threshold voltage is changed according to the rotation angle. In FIG. 15B, the threshold voltage is decreased as indicated by reference numeral 315 with respect to the rotation angle at which the output current of the photodiode 106 decreases. Thereby, the binarization circuit 152 can binarize the received signal correctly for any rotation angle of the rotation unit.

  FIG. 13 is a circuit configuration diagram of the binarization circuit 152 in which the threshold voltage is changed according to the rotation angle. The DA converter 301 of the control unit 153 generates a threshold voltage corresponding to the rotation angle and supplies it to the plus terminal of the operational amplifier A11.

  FIG. 14 shows an example of the contents stored in the EEPROM 154 in this embodiment. The detection voltage 303 corresponding to the rotation angle 302 is stored by the processing in the measurement mode described with reference to FIG. 5, and a voltage approximately in the middle of the detection voltage 303 is stored in the EEPROM 154 as the threshold voltage 304. In the present embodiment, the binary discrimination threshold corresponding to the rotation angle is stored in the EEPROM 154 as one element of the reception characteristic.

  FIG. 16 shows a flowchart of pan rotation processing in this embodiment. The left side shows the process of the fixed unit 121, and the right side shows the process of the rotating unit 122. Detailed description of the same processing as in FIG. 12 is omitted.

  In step S258, the fixing unit 121 receives the pan rotation angle from the rotation unit 122. In step S320, the control unit 153 specifies a threshold voltage corresponding to the pan angle stored in the EEPROM 154. For example, when the pan angle is 0 °, 28 mV is designated from the threshold voltage 304 (FIG. 14).

  In step S321, the control unit 153 supplies the designated threshold voltage from the DA converter 301 to the plus terminal of the operational amplifier A11. With this process, a threshold voltage corresponding to the rotation angle is set in the binarization circuit 152. As a result, even in the state of the output signal 312 shown in FIG.

  The configuration for changing the threshold value of the binarization circuit 152 according to the rotation angle may be combined with the configuration for controlling the amplification factor according to the rotation angle described in the first embodiment.

  An embodiment will be described in which the LED drive level of the LED circuit 101 is controlled in accordance with the rotation angle so that the received signal level is constant or substantially constant regardless of the rotation angle.

  FIG. 19A shows a timing chart when the LED drive level is constant regardless of the rotation angle. FIG. 19B shows a timing chart of the present embodiment in which the LED drive level is changed according to the rotation angle so that the received signal level is constant or substantially constant regardless of the rotation angle.

  In FIG. 19A, reference numeral 310 denotes a transmission signal or drive signal applied to the LED of the LED circuit 101. Reference numerals 311 and 312 denote signals obtained by converting the output current of the photodiode 106 into voltage. Reference numeral 311 denotes a signal waveform when the amount of light is large, and 312 denotes a signal waveform when the amount of light is small.

  In this embodiment, as indicated by a solid line 310 in FIG. 19B, the amplitude of the LED drive signal is increased as indicated by a broken line 360 at a rotation angle at which the received signal level becomes low. As a result, the received signal increases from the level indicated by reference numeral 312 to the level indicated by the broken line 361.

  FIG. 17 shows a circuit example of the LED circuit 101 of this embodiment. Reference numeral 350 denotes an LED. The transmission circuit 133 is connected to the output of the DA converter 352 of the control unit 134 via the LED 350 and the resistor R30. The control unit 134 can control the drive current flowing through the LED 350 by controlling the output voltage of the DA converter 352. For example, the output signal of the transmission circuit 133 is a 3V amplitude pulse signal. The LED 350 has a forward voltage of 0.6V, and the resistance value of the resistor R30 is 40Ω.

  FIG. 18 shows an example of the contents stored in the EEPROM 154. Similar to the first embodiment, the measurement mode (FIG. 5) is processed, and the detection voltage 354 corresponding to the rotation angle 353 is stored. The voltage value of the detection voltage 354 is a voltage value detected by the peak hold circuit 151 when the LED current is 24 mA.

  In the present embodiment, the control unit 134 determines the LED current 355 according to the detection voltage 354 so that the corrected voltage in the peak hold circuit 151 is about 120 mV. The control unit 134 determines the output voltage 356 of the DA converter 352 from the obtained LED current 355.

In the example shown in FIG. 18, when the rotation angle 353 is 0 °, the detection voltage is 57 mV. 57 mV is the result of detection by the peak hold circuit 151 with the LED current set to 24 mA, and the LED current 355 for setting the corrected voltage to 120 mV is:
120mV / 57mV × 24mA ≒ 50mA
Can be obtained.

Similarly, when the rotation angle 353 is 10 °, the detection voltage is 65 mV. The LED current 355 for setting the corrected detection voltage to 120 mV is:
120 mV / 65 mV × 24 mA≈44 mA
It becomes.

The output voltage 356 of the DA converter 352 is based on the LED current 355, the amplitude voltage of the output signal of the transmission circuit 133, 3.0 V, the LED forward voltage 0.6 V of the LED circuit 101, and the resistance value 40Ω of the resistor R30. Desired. That is,
Output voltage of DA converter = amplitude voltage 3.0V−forward voltage 0.6V−resistance 40Ω × LED current. For example, when the rotation angle is 0 °, the output voltage of the DA converter 352 is 3.0V−0.6V−40Ω × 0.05A = 0.4V.

  In the present embodiment, the output voltage of the DA converter 352 is thus determined and stored in the EEPROM 154.

  In this embodiment, the LED current 355 is stored in the EEPROM 154, but what is required for the pan rotation process is the output voltage of the DA converter. Therefore, storing the LED current 355 in the EEPROM 154 is not essential.

  The means for rotationally driving the rotating part and the rotational position detecting means may be arranged on the fixed part. FIG. 20 shows a schematic block diagram of a fourth embodiment of the present invention. In the present embodiment, means related to the rotation of the rotating unit 122a, specifically, a pan rotation driving unit 136a, a pan rotating mechanism 137a, and a rotation position detecting mechanism 138a are arranged in the fixed unit 121a. Since the pan rotation mechanism 137a, the pan rotation drive unit 136a, and the rotation position detection mechanism 138a are arranged in the fixed unit 121a, the control unit 153a of the fixed unit 121 can directly detect the pan rotation position.

  In this configuration, since it is not necessary to transmit the pan rotation position from the rotating unit to the fixed unit, the combining circuit 132 is not necessary in the rotating unit 122a.

  In the above embodiment, optical space transmission is adopted for signal transmission from the rotating portion to the fixed portion, but optical space transmission may also be adopted for signal transmission from the fixed portion to the rotating portion. FIG. 21 is a schematic configuration diagram of optical space transmission between the rotating unit and the fixed unit having such a configuration.

  In FIG. 21A, reference numeral 501 denotes an LED (first light emitting element) disposed in the rotating part. Reference numeral 502 denotes a photodiode (first light receiving element) disposed in the rotating unit. Reference numeral 503 denotes an LED (second light emitting element) disposed in the fixed portion. Reference numeral 504 denotes a photodiode (second light receiving element) disposed in the fixed portion. The LED 501 and the photodiode 504 face each other, and the LED 503 and the photodiode 502 face each other at a rotation angle position where the rotation unit is located.

  FIG. 21B shows the positional relationship between the LEDs 501 and 503 and the photodiodes 502 and 504 when the rotating part is rotated with respect to the fixed part by 180 degrees from the position shown in FIG. As shown in FIG. 21B, the LED 501 faces the LED 503 and the photodiode 502 faces the photodiode 504. Since the emission angles of the LEDs 501 and 503 are usually wide, as shown in FIG. 21B, a sufficiently strong optical signal is incident on the photodiodes 502 and 504 even if the outgoing optical axis and the received optical axis are shifted laterally. sell. As described in the above embodiment, bidirectional transmission by light can be realized by controlling the amplification factor, the threshold value, and / or the LED driving current according to the rotation angle.

  Although the embodiment of the network camera system using the turning camera has been described, the present invention can be applied to various devices having a rotation mechanism.

  Although preferred embodiments of the present invention have been described, the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist thereof.

Claims (8)

A signal transmission device for transmitting a signal from a rotating part rotatable relative to a fixed part to the fixed part,
A light emitting element that is disposed in the rotating unit and outputs an optical signal carrying the signal;
A light receiving element that is disposed in the fixed portion and receives the optical signal;
Receiving means for receiving the signal from the output of the light receiving element;
Storage means for storing drive levels of the light emitting elements or reception characteristics of the receiving means for a plurality of rotational positions of the rotating part relative to the fixed part;
The storage unit is referred to according to the current rotation position of the rotation unit with respect to the fixed unit, and the drive level of the light emitting element or the reception characteristic of the reception unit is less changed according to the rotation position And a control means for controlling the signal transmission apparatus.   The signal transmission apparatus according to claim 1, wherein the reception characteristic is an amplification factor of an amplification unit that amplifies an output signal of the light receiving element.   The signal transmission apparatus according to claim 1 or 2, wherein the reception unit includes a binarization unit, and the reception characteristic is a binary discrimination threshold of the binarization unit.   Furthermore, in the measurement mode, it comprises a measuring means for measuring the driving level of the light emitting element or the receiving characteristic of the receiving means for a plurality of rotational positions of the rotating part with respect to the fixed part, and storing it in the storage means. The signal transmission device according to claim 1, wherein the signal transmission device is a signal transmission device. The rotating unit includes an imaging unit, and the signal is a signal for carrying a video signal by the imaging unit,
5. The signal transmission apparatus according to claim 4, wherein the control unit prohibits external output of a reception signal by the reception unit in the measurement mode.   5. The rotating device according to claim 1, wherein the rotating unit includes a rotating mechanism that rotates the rotating unit with respect to the fixed unit, and a unit that outputs a signal indicating the rotating position as the signal. The signal transmission device according to claim 1.   The signal transmission device according to claim 1, wherein the rotation unit includes a unit that receives a command from an external device via a network.   The fixing unit includes a second light emitting element that generates an optical signal that conveys a signal to be transmitted to the rotating unit, and the rotating unit receives an optical signal output from the second light emitting element. The signal transmission device according to claim 1, further comprising a second light receiving element.

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