Patent Description:
Camera accessories include a master lens via which a subject image can be formed and an intermediate accessory that can be mounted between the master lens and a camera body (see <CIT>, hereinafter PTL1). In order to ensure that the master lens and the intermediate accessory are distinguishable from each other by the camera body, it is necessary in the related art to dispose terminals at the master lens in a quantity different from the number of terminals at the intermediate accessory.

Each of <CIT>, <CIT>, and <CIT> forms part of the state of the art relative to the present disclosure.

According to first aspect of the present invention, there is provided a camera accessory as recited in claim <NUM> below.

According to a second aspect of the present invention, there is provided a camera accessory as recited in claim <NUM> below.

The dependent claims define particular aspects of the claimed invention.

The following is an explanation of an embodiment of the present invention, given in reference to drawings.

In <FIG> showing a camera system <NUM> achieved in an embodiment of the present invention in a perspective, camera accessories are yet to be mounted at a camera body <NUM>. <FIG> is a block diagram of the essential structure of the camera system <NUM>.

The camera accessories in the embodiment include an interchangeable lens <NUM> used as a master lens and a teleconverter <NUM>, which is an intermediate accessory. The term "master lens" used in the description of the embodiment refers to a device mounted at the camera body <NUM>, via which a subject image can be formed. In addition, the term "master lens" used in the description of the embodiment refers to a device on the subject side of which another camera accessory in a communication-enabled state is not mounted. The term "intermediate accessory" used in the description of the embodiment refers to a device on the subject side of which another device can be mounted in a communication-enabled state. Such an intermediate accessory may be otherwise referred to as a non-master lens. A non-master lens is utilized in combination with the master lens.

A bayonet structure, adopted at a body-side mount and at a lens-side mount, makes it possible to couple the camera body <NUM> with a camera accessory and to couple a camera accessory with another camera accessory. This means that a body-side mount <NUM> at the camera body <NUM> and a front-side mount <NUM> disposed on the lens-side of the teleconverter <NUM> have shapes substantially identical to each other and that a lens-side mount <NUM> at the interchangeable lens <NUM> and a rear-side mount <NUM> disposed on the body-side of the teleconverter <NUM> have shapes substantially identical to each other. Thus, the interchangeable lens <NUM> can be directly mounted at the camera body <NUM> without the teleconverter <NUM> present between the camera body <NUM> and itself, and it can also be indirectly mounted at the camera body <NUM> via the teleconverter <NUM>. As the camera body <NUM> and a camera accessory become coupled with each other or a camera accessory becomes coupled with another camera accessory, terminals disposed at the mounts come into physical contact with each other, thereby achieving an electrical connection.

The interchangeable lens <NUM> includes the lens-side mount <NUM>, a lens-side control unit <NUM>, a lens-side communication unit <NUM>, a lens-side storage unit <NUM>, a lens-side source circuit <NUM>, an image-capturing optical system <NUM>, a lens drive unit <NUM> and an aperture drive unit <NUM>.

At the lens-side mount <NUM> having an annular shape, a lens-side terminal holding unit <NUM> is disposed. A plurality of lens-side terminals or contacts are disposed so as to form a circular arc centered on the optical axis at the lens-side terminal holding unit <NUM>. The plurality of lens-side terminals include, for instance, a mount detection terminal via which a signal indicating that the interchangeable lens <NUM> has been mounted at the camera body <NUM> is transmitted to the camera body <NUM>, a communication terminal via which communication is carried out between the interchangeable lens <NUM> and the camera body <NUM>, a power supply terminal via which electric power is provided from the camera body <NUM> to the interchangeable lens <NUM> and a ground terminal.

When the exchangeable lens <NUM> is mounted at the camera body <NUM> via the teleconverter <NUM>, signals and power provided via the various terminals are transmitted from the interchangeable lens <NUM> to the camera body <NUM> via the teleconverter <NUM>. In addition, when the interchangeable lens <NUM> is directly mounted at the camera body <NUM>, they are directly transmitted from the interchangeable lens <NUM> to the camera body <NUM>.

The lens-side control unit <NUM> is constituted with a microcomputer, its peripheral circuits and the like. The lens-side control unit <NUM> controls various components of the interchangeable lens <NUM> by executing a control program stored in the lens-side storage unit <NUM>. In addition, in response to a request issued from the camera body <NUM>, the lens-side control unit <NUM> reads out data stored in the lens-side storage unit <NUM> and transmits the data thus read out to the camera body <NUM> from the lens-side communication unit <NUM>, either via the teleconverter <NUM> or directly. The lens-side control unit <NUM> is connected to the lens-side communication unit <NUM>, the lens-side storage unit <NUM>, the lens drive unit <NUM> and the aperture drive unit <NUM>.

The lens-side communication unit <NUM> carries out specific communication, either via the teleconverter <NUM> or directly, with a body-side communication unit <NUM>, based upon an instruction issued by the body-side communication unit <NUM>. The lens-side communication unit <NUM> is connected with the lens-side control unit <NUM> and the communication terminal mentioned earlier. Through the communication carried out between the body-side communication unit <NUM> and the lens-side communication unit <NUM>, instructions, such as a drive instruction for driving a lens <NUM> and information requests including a transmission request for data stored in the lens-side storage unit <NUM>, which are to be described later, are transmitted from the camera body <NUM>, either via the teleconverter <NUM> or directly, to the interchangeable lens <NUM>. In addition, based upon an instruction issued from the body-side communication unit <NUM>, information indicating the state within the interchangeable lens <NUM>, e.g., the position to which the lens <NUM> has been moved, or data read out from the lens-side storage unit <NUM> are transmitted from the interchangeable lens <NUM>, either via the teleconverter <NUM> or directly, to the camera body <NUM>.

The lens-side storage unit <NUM> is constituted with a non-volatile storage medium. Data recording into and data readout from the lens-side storage unit <NUM> are controlled the lens-side control unit <NUM>. In addition to the control program executed by the lens-side control unit <NUM> and the like, data indicating the model name of the interchangeable lens <NUM> (may be otherwise referred to as model name information), data indicating the optical characteristics of the image-capturing optical system <NUM>, data indicating a device ID and the like can be stored in the lens-side storage unit <NUM>. A device ID, which is an identifier that enables the camera body <NUM> to identify a camera accessory mounted thereat, is data constituted with signs and the like used to specify a communication partner among camera accessories mounted at the camera body <NUM>. A device ID is transmitted from the camera body <NUM> each time the interchangeable lens <NUM> is mounted at the camera body <NUM> (or each time a mounted state is detected). The lens-side storage unit <NUM> is connected with the lens-side control unit <NUM>.

The source circuit <NUM> distributes electric power from the camera body <NUM> to the interchangeable lens <NUM> via the power supply terminal, to various components within the interchange lens <NUM>. The source circuit <NUM> is connected with the power supply terminal mentioned above.

The image-capturing optical system <NUM> forms a subject image onto an image-capturing surface either via the teleconverter <NUM> or directly. An optical axis O of the image-capturing optical system <NUM> is substantially in alignment with the centers of the lens-side mount <NUM>, the front-side mount <NUM> of the teleconverter <NUM>, the rear-side mount <NUM> of the teleconverter <NUM>, the body-side mount <NUM> and the image-capturing surface. The image-capturing optical system <NUM> is configured with a plurality of lenses <NUM> including, for instance, a focusing lens and a zoom lens, and an aperture <NUM>. At least one of the plurality of lenses <NUM> is structured so as to be allowed to move, either driven by the lens drive unit <NUM> or in response to a manual operation, along the optical axis O. The positions taken by the individual lenses along the optical axis O can be detected via an encoder or the like included in the lens drive unit <NUM>.

The amount of light to enter an image sensor <NUM> is adjusted via the aperture <NUM>. The aperture <NUM> is structured so as to be able to alter the aperture stop diameter (aperture number) as it is driven by the aperture drive unit <NUM> or in response to a manual operation. The aperture stop diameter at the aperture <NUM> can be detected via an encoder or the like included in the aperture drive unit <NUM>.

The lens drive unit <NUM> may be configured with, for instance, a motor and a lens drive mechanism. The lens drive unit <NUM> causes the focusing lens among the lenses <NUM> to move along the optical axis O based upon an instruction issued by the lens-side control unit <NUM>. The lens drive unit <NUM> is connected with the lens-side control unit <NUM>.

The aperture drive unit <NUM> is constituted with, for instance, a motor and an aperture drive mechanism. The aperture drive unit <NUM> alters the aperture stop diameter at the aperture <NUM> based upon an instruction issued by the lens-side control unit <NUM>. The aperture drive unit <NUM> is connected with the lens-side control unit <NUM>.

The teleconverter <NUM> includes the rear-side mount <NUM> that faces opposite the body-side mount <NUM> when the teleconverter <NUM> is mounted at the camera body <NUM>, the front-side mount <NUM> that faces opposite the lens-side mount <NUM> when the interchangeable lens <NUM> is mounted thereat, an accessory-side control/communication unit <NUM>, an accessory-side storage unit <NUM>, a switch <NUM>, an accessory-side source circuit <NUM> and a lens <NUM>.

At the rear-side mount <NUM>, a rear-side terminal holding unit <NUM> having a plurality of terminals or contacts disposed thereat so as to form a circular arc centered on the optical axis, is disposed. At the front-side mount <NUM>, a front-side terminal holding unit <NUM> having a plurality of terminals or contacts disposed thereat so as to form a circular arc centered on the optical axis, is disposed. The plurality of terminals disposed at the rear-side terminal holding unit <NUM> and at the front-side terminal holding unit <NUM> include a mount detection terminal via which a signal indicating that the camera accessory has been mounted is transmitted, a communication terminal via which the camera accessory carries out communication with the camera body <NUM>, a power supply terminal via which electric power is provided from the camera body <NUM> to the camera accessory and the ground terminal. The terminals included in the rear-side terminal holding unit <NUM> located on the rear-side (toward the camera body <NUM>) of the intermediate accessory are identical to the terminals included in the lens-side terminal holding unit <NUM> at the lens-side mount <NUM>. In addition, the terminals included in the front-side terminal holding unit <NUM> on the front side (toward the subject) of the intermediate accessory are identical to the terminals included in the body-side terminal holding unit <NUM> at the body-side mount <NUM>.

The accessory-side control/communication unit <NUM> is constituted with a microcomputer, a storage unit, their peripheral circuits and the like. The accessory-side control/communication unit <NUM> executes open/close control of the switch <NUM> by executing a control program stored in the accessory-side storage unit <NUM>. As the switch <NUM> is closed, electric power provided from the camera body <NUM> to the source circuit <NUM> is supplied to the interchangeable lens <NUM>, whereas as the switch <NUM> opens, the power supply to the interchangeable lens <NUM> is cut off. In addition, the accessory-side control/communication unit <NUM> carries out predetermined communication with the body-side communication unit <NUM>. Furthermore, in response to a request issued from the camera body <NUM>, the accessory-side control/communication unit <NUM> reads out data stored in the accessory-side storage unit <NUM> and transmits the data thus read out to the camera body <NUM>. Moreover, the accessory-side control/communication unit <NUM> controls operations, detections and the like executed in the teleconverter <NUM> in response to instructions issued from the camera body <NUM>. The accessory-side control/communication unit <NUM> is connected with the communication terminal and the switch <NUM> mentioned above.

Data recording into and data readout from the accessory-side storage unit <NUM> are controlled by the accessory-side control/communication unit <NUM>. In addition to the control program executed by the accessory-side control/communication unit <NUM> and the like, data indicating the model name of the teleconverter <NUM> (may otherwise be referred to as model name information), data indicating a device ID and the like can be stored in the accessory-side storage unit <NUM>. The accessory-side storage unit <NUM> is connected with the accessory-side control/communication unit <NUM>.

The switch <NUM> is a semiconductor switch element that may be constituted with, for instance, an FET (field effect transistor). An ON/OFF state at the switch <NUM> is controlled based upon a control signal input to the switch <NUM> from the accessory-side control/communication unit <NUM>. When the switch is in an OFF state, the contact point is open, whereas when the switch is in an ON state, the contact point is closed. The switch <NUM> enters an OFF state when a high-level (hereafter notated as an "H" level) control signal is not input thereto from the accessory-side control/communication unit <NUM> i.e., when a low-level (hereafter notated as an "L" level) control signal is input thereto, whereas it enters an ON state when an H level control signal is input thereto from the accessory-side control/communication unit <NUM>. The switch <NUM> is connected with the source circuit <NUM>, the power supply terminal among second terminals, and the accessory-side control/communication unit <NUM>.

The source circuit <NUM> distributes electric power provided to the teleconverter <NUM> via the body-side power supply terminal and the ground terminal, to the various components within the teleconverter <NUM> or to the interchangeable lens <NUM>. The source circuit <NUM> is connected to the power supply terminal and the switch <NUM>.

The lens <NUM> is a teleconverter lens that converts the focal length of the lenses <NUM> by, for instance, a factor of <NUM>. Thus, when the teleconverter <NUM> is mounted at the interchangeable lens <NUM>, the focal length of the interchangeable lens <NUM> is increased by a factor of <NUM> over the focal length achieved without the teleconverter <NUM> mounted thereat.

The camera body <NUM> includes the body-side mount <NUM>, a body-side control unit <NUM>, a body-side communication unit <NUM>, a source unit <NUM>, the image sensor <NUM>, a signal processing unit <NUM>, an operation member <NUM> and a display unit <NUM>.

The body-side terminal holding unit <NUM> is disposed at the body-side mount <NUM> having an annular shape. A plurality of body-side terminals are held in the body-side terminal holding unit <NUM>. The plurality of body-side terminals include, for instance, a mount detection terminal via which a signal indicating that the interchangeable lens <NUM> has been mounted at the camera body <NUM> is transmitted to the camera body <NUM> either via the teleconverter <NUM> or directly, a communication terminal via which communication is carried out between the camera body <NUM> and the teleconverter <NUM> or the interchangeable lens <NUM>, a power supply terminal via which electric power is provided from the camera body <NUM> to the teleconverter <NUM> or the interchangeable lens <NUM>, and a ground terminal.

The body-side control unit <NUM> is configured with a microcomputer, its peripheral circuits and the like. The body-side control unit <NUM> controls various components disposed inside the camera body <NUM> by executing a control program stored in a storage unit <NUM>. The body-side control unit <NUM> is connected with the body-side communication unit <NUM>, the source unit <NUM>, the image sensor <NUM>, the signal processing unit <NUM>, the operation member <NUM>, the display unit <NUM> and the mount detection terminal mentioned above.

The body-side control unit <NUM> includes the storage unit <NUM>. Data recording into and data readout from the storage unit <NUM> are controlled by the body-side control unit <NUM>. In addition to the control program executed by the body-side control unit <NUM> and the like, camera accessory model name information, data indicating the optical characteristics of camera accessories, and the like can be stored in the storage unit <NUM>. Furthermore, as a camera accessory is mounted, the body-side control unit <NUM> assigns a device ID, as will be explained later, and holds the device ID for temporary storage after it is transmitted to the camera accessory. The information indicating the device ID held by the body-side control unit <NUM> is erased in response to a power-off operation or as the camera accessory is dismounted.

The body-side communication unit <NUM> carries out the communication mentioned earlier with the lens-side communication unit <NUM> or with the accessory-side control/communication unit <NUM>. The body-side communication unit <NUM> is connected with the body-side control unit <NUM> and the communication terminal mentioned above.

The source unit <NUM> converts the voltage at a battery (not shown) to a voltage to be used at the various units of the camera system <NUM> and supplies the voltage resulting from the conversion to the various components in the camera body <NUM>, the interchangeable_lens <NUM> and the teleconverter <NUM>. The source unit <NUM> is able to switch on/off power supply to each power recipient in response to an instruction issued by the body-side control unit <NUM>. The source unit <NUM> is connected with the body-side control unit <NUM> and the power supply terminal mentioned above.

The image sensor <NUM> is a solid-state image sensor such as a CMOS image sensor or a CCD image sensor. In response to a control signal provided by the body-side control unit <NUM>, the image sensor <NUM> captures a subject image formed on the image-capturing surface and outputs an image-capturing signal. The image sensor <NUM> is connected with the body-side control unit <NUM> and the signal processing unit <NUM>.

The image sensor <NUM> includes pixels used for image generation (hereafter will be referred to as image-capturing pixels) and pixels used for focus detection (hereafter will be referred to as focus detection pixels). Signals generated at the image-capturing pixels (hereafter will be referred to as image-capturing pixel signals) are used by the signal processing unit <NUM>, which will be described later, for image data generation. In addition, signals generated at the focus detection pixels (hereafter will be referred to as focus detection pixel signals) are used by the signal processing unit <NUM>, which will be described later, for focus detection processing through which an image forming state achieved via the interchangeable lens <NUM>, i.e., the focus position, is detected.

The signal processing unit <NUM> generates image data by executing a predetermined image processing on the image-capturing pixel signals output from the image sensor <NUM>. The image data thus generated may be recorded into a storage medium (not shown) in a predetermined file format or may be used to display an image at the display unit <NUM>. The signal processing unit <NUM> is connected with the body-side control unit <NUM>, the image sensor <NUM> and the display unit <NUM>.

In addition, the signal processing unit <NUM> detects the focus position of the interchangeable lens <NUM> by using the focus detection pixel signals output from the image sensor <NUM> and calculates a defocus quantity. The signal processing unit <NUM> calculates the distance over which the focusing lens needs to move in order to reach the in-focus position based upon the defocus quantity it has calculated.

The operation member <NUM>, which includes a shutter release button, an operation switch and the like, is disposed at an exterior surface of the camera body <NUM>. The user operates the operation member <NUM> to issue a photographing instruction, a photographing condition setting instruction and the like. The operation member <NUM> transmits an operation signal corresponding to a user operation to the body-side control unit <NUM>.

The display unit <NUM> may be constituted with, for instance, a liquid crystal display panel. In response to an instruction issued by the body-side control unit <NUM>, the display unit <NUM> brings up on display an image based upon image data having undergone the processing in the signal processing unit <NUM>, an operation menu screen and the like. The display unit <NUM> is connected with the body-side control unit <NUM> and the signal processing unit <NUM>.

<FIG> is a circuit diagram schematically illustrating electrical connections among the camera body <NUM>, the teleconverter <NUM> and the interchangeable lens <NUM>. The arrows in <FIG> indicate signal flow.

The body-side terminal holding unit <NUM> at the body-side mount <NUM> holds the body-side terminals that include an LDET (B) terminal, a VBAT (B) terminal, a PGND (B) terminal, a V33 (B) terminal, a GND (B) terminal, an RDY (B) terminal, a DATAB (B) terminal, a CLK (B) terminal, a DATAL (B) terminal, an HCLK (B) terminal, and an HDATA (B) terminal. These <NUM> body-side terminals will be collectively referred to as a body-side terminal group. The individual terminals in the body-side terminal group are disposed in the order indicated in <FIG> by forming a circular arc centered on the central axis of the body-side mount unit <NUM>.

The lens-side terminal holding unit <NUM> at the lens-side mount <NUM> holds an LDET (L) terminal, a VBAT (L) terminal, a PGND (L) terminal, a V33 (L) terminal, a GND (L) terminal, an RDY (L) terminal, a DATAB (L) terminal, a CLK (L) terminal, a DATAL (L) terminal, an HCLK (L) terminal, and an HDATA (L) terminal. These <NUM> lens-side terminals will be collectively referred to as a lens-side terminal group. The individual terminals in the lens-side terminal group are disposed in the order indicated in <FIG> by forming a circular arc centered on the optical axis at the lens-side holding unit <NUM>.

A second terminal group held in the front-side terminal holding unit <NUM> at the teleconverter <NUM> is identical to the body-side terminal group and a first terminal group held in the rear-side terminal holding unit <NUM> at the teleconverter <NUM> is identical to the lens-side terminal group. <FIG> does not include an illustration of the individual terminals held in the rear-side terminal holding unit <NUM> and the front-side terminal holding unit <NUM>.

In addition, the accessory-side control/communication unit <NUM> is connected in parallel individually between the RDY (B) terminal at the camera body <NUM> and the RDY (L) terminal at the interchangeable lens <NUM>, between the DATAB (B) terminal at the camera body <NUM> and the DATAB (L) terminal at the interchangeable lens <NUM>, between the CLK (B) terminal at the camera body <NUM> and the CLK (L) terminal at the interchangeable lens <NUM>, and between the DATAL (B) terminal at the camera body <NUM> and the DATAL (L) terminal at the exchangeable lens <NUM>.

The RDY (B) terminal, the DATAB (B) terminal, the CLK (B) terminal, the DATAL (B) terminal, the HCLK (B) terminal, the HDATA (B) terminal, the RDY (L) terminal, the DATAB (L) terminal, the CLK (L) terminal, the DATAL (L) terminal, the HCLK (L) terminal and the HDATA (L) terminal are the communication terminals mentioned earlier. Among the communication terminals, the RDY (B) terminal, the DATAB (B) terminal, the CLK (B) terminal and the DATAL (B) terminal are used in command data communication, which will be explained later. In addition, the HCLK (B) terminal and the HDATA (B) terminal among the communication terminals are used in hotline communication, which will be explained later. The embodiment includes two communication systems, i.e., a command data communication system and a hotline communication system. The command data communication system and the hotline communication system are two different communication systems independent of each other.

The RDY (B) terminal, the DATAB (B) terminal, the CLK (B) terminal, the DATAL (B) terminal, the HCLK (B) terminal and the HDATA (B) terminal are each connected to the body-side control unit <NUM> via the body-side communication unit <NUM>. The RDY (L) terminal, the DATAB (L) terminal, the CLK (L) terminal, the DATAL (L) terminal, the HCLK (L) terminal and the HDATA (L) terminal are each connected to the lens-side control unit <NUM> via the lens-side communication unit <NUM>.

The RDY (B) terminal is an input terminal to which a signal from the RDY (L) terminal is input. A signal from the RDY (L) terminal at the interchangeable lens <NUM>, which indicates whether or not the interchangeable lens <NUM> is in a command data communication-enabled state (hereafter will be notated as an RDYL signal), is input to the RDY (B) terminal via the teleconverter <NUM>. In addition, a signal indicating whether or not the teleconverter <NUM> is in a command data communication-enabled state (hereafter will be notated as an RDYA signal) is input from the teleconverter <NUM> to the RDY (B) terminal. In a command data communication-enabled state, the lens-side control unit <NUM> shifts the potential of the RDYL signal from L level to H level and then back to L level. In a command data communication-enabled state, the accessory-side control/communication unit <NUM> shifts the potential of the RDYA signal from L level to H level and then back to L level. Upon receiving the RDYL signal or the RDYA signal, an RDYB signal is transmitted from the RDY (B) terminal to the body-side control unit <NUM> via the body-side communication unit <NUM>. Upon sensing that the potential of the RDYB signal has shifted from L level to H level and then back to L level, the body-side control unit <NUM> makes a decision as to whether or not the camera accessory specified by a device ID is in a command data communication-enabled state.

The lens-side control unit <NUM> is capable of switching the output through the RDY (L) terminal at the interchangeable lens <NUM> to a high impedance state. In addition, the accessory-side control/communication unit <NUM> is capable of switching the output through the RDY (L) terminal at the teleconverter <NUM> to a high impedance state. The term "high impedance state" is used to refer to a state in which the connection with the body-side communication unit <NUM> is substantially cut off. As the accessory-side control/communication unit <NUM> cuts off connection with the body-side communication unit <NUM>, the lens-side communication unit <NUM> becomes connected with the body-side communication unit <NUM>. In addition, as the lens-side communication unit <NUM> cuts off connection with the body-side communication unit <NUM>, the accessory-side control/communication unit <NUM> becomes connected with the body-side communication unit <NUM>. When the accessory-side control/communication unit <NUM> is connected with the body-side communication unit <NUM>, an RDYA signal from the teleconverter <NUM> is transmitted to the RDY (B) terminal at the camera body <NUM>. When the lens-side communication unit <NUM> is connected with the body-side communication unit <NUM>, the RDYL signal from the interchangeable lens <NUM> is transmitted to the RDY(B) terminal at the camera body <NUM>. The RDYA signal output by the accessory-side control/communication unit <NUM> is a signal generated by the accessory-side control/communication unit <NUM> through decision-making executed thereat. The RDYL signal output by the lens-side communication unit <NUM> is a signal generated by the lens-side control unit <NUM> through decision-making executed thereat.

Through the DATAB (B) terminal, a data signal (hereafter will be notated as a DATAB signal) is output to the DATAB (L) terminal at the interchangeable lens <NUM> or the teleconverter <NUM>. The DATAB (L) terminal is an input terminal at which the DATAB signal output through the DATAB (B) terminal is input. This means that a DATAB signal from the body-side communication unit <NUM> is input to the lens-side communication unit <NUM> or the accessory-side control/communication unit <NUM>.

The DATAL (B) terminal is an input terminal through which a signal from the DATAL (L) terminal is input. A data signal (hereafter will be notated as a DATAA signal) from the DATAL (L) terminal at the teleconverter <NUM> is input to the DATAL (B) terminal, or a data signal (hereafter will be notated as a DATAL signal) from the DATAL (L) terminal at the interchangeable lens <NUM> is input to the DATAL (B) terminal via the teleconverter <NUM>.

The lens-side communication unit <NUM> is capable of switching the output through the DATAL (L) terminal at the interchangeable lens <NUM> to a high impedance state. In addition, the accessory-side control/communication unit <NUM> is capable of switching the output through the DATAL (L) terminal at the teleconverter <NUM> to a high impedance state. When the accessory-side control/communication unit <NUM> is connected with the body-side communication unit <NUM>, the DATAA signal from the teleconverter <NUM> is transmitted to the DATAL (B) terminal at the camera body <NUM>. When the lens-side communication unit <NUM> is connected with the body-side communication unit <NUM>, the DATAL signal from the interchangeable lens <NUM> is transmitted to the DATAL (B) terminal at the camera body <NUM>. The DATAA signal output by the accessory-side control/communication unit <NUM> is a signal generated by the accessory-side control/communication unit <NUM> through decision-making executed thereat. The DATAL signal output by the lens-side communication unit <NUM> is a signal generated by the lens-side control unit <NUM> through decision-making executed thereat.

The CLK (B) terminal is an output terminal through which a clock signal (hereafter will be notated as a CLK signal) is output to a CLK (L) terminal. The CLK (L) terminal is an input terminal to which the CLK signal from the CLK (B) terminal is input. A CLK signal provided from the body-side communication unit <NUM> is input to the lens-side communication unit <NUM> via the teleconverter <NUM>. A CLK signal from the body-side communication unit <NUM> is input to the accessory-side control/communication unit <NUM>.

The HCLK (B) terminal is an input terminal through which a clock signal (hereafter will be notated as an HCLK signal) from the HCLK (L) terminal at the interchangeable lens <NUM> is input to the body-side communication unit <NUM>. The HCLK (L) terminal is an output terminal through which the HCLK signal is output to the HCLK (B) terminal.

The HDATA (B) terminal is an input terminal through which a data signal (hereafter will be notated as an HDATA signal) from the HDATA (L) terminal at the interchangeable lens <NUM> is input to the body-side communication unit <NUM>. The HDATA (L) terminal is an output terminal through which the HDATA signal is output to the HDATA (B) terminal.

The LDET (B) terminal is the mount detection terminal explained earlier. At the camera body <NUM>, the LDET (B) terminal is connected to the body-side control unit <NUM> via a resistor R2. Between the resistor R2 and the body-side control unit <NUM>, a source V33 provided from the source unit <NUM> is connected via a resistor R1.

At the interchangeable lens <NUM>, the LDET (L) terminal is connected (grounded) to a GND potential via a resistor R3. In addition, at the teleconverter <NUM>, the area located between the LDET (B) terminal and the LDET (L) terminal is not grounded. The embodiment will be described by assuming that the LDET (L) terminal is grounded at the master lens and that the area between the LDET (B) terminal and the LDET (L) terminal at the non-master lens is not grounded.

In such a structure, the LDET (B) terminal is pulled up within the camera body <NUM> and thus, takes the potential of the source V33 when the interchangeable lens <NUM> is not mounted. Once the interchangeable lens <NUM> is mounted, the LDET (L) terminal assuming the ground potential becomes connected to the pulled up LDET (B) terminal, thereby lowering the potential at the LDET (B) terminal. As a result, the camera body <NUM> is able to detect that the interchangeable lens <NUM> has been mounted. In addition, when only the teleconverter <NUM> is mounted but the interchangeable lens <NUM> is not mounted at the camera body <NUM>, the potential of the source V33 is sustained at the LDET (B) terminal.

The VBAT (B) terminal is a power supply terminal through which electric power is supplied to a camera accessory. The lens drive unit <NUM> and the aperture drive unit <NUM> are driven with electric power provided from the VBAT (B) terminal to the VBAT (L) terminal. The lens drive unit <NUM> and the aperture drive unit <NUM>, each having an actuator such as a motor, require a voltage higher than or a current greater than that of the electric power provided to the lens-side control unit <NUM>. In the following description, a voltage applied from the source unit <NUM> to the VBAT (B) terminal will be referred to as a drive system voltage. The PGND (B) terminal is a ground terminal corresponding to the VBAT (B) terminal. The PGND (B) terminal is connected with the PGND (L) terminal.

The V33 (B) terminal is also a power supply terminal through which electric power is provided to a camera accessory. The electric power provided from the V33 (B) terminal to the teleconverter <NUM> is distributed to the various components of the teleconverter <NUM>, such as the accessory-side control/communication unit <NUM>, via the source circuit <NUM>. In addition, electric power output from the source circuit <NUM> is provided to the V33 (L) terminal at the interchangeable lens <NUM> via the switch <NUM>. The electric power provided to the interchangeable lens <NUM> through the V33 (L) terminal is distributed to the various components of the interchangeable lens <NUM>, such as the lens-side control unit <NUM>, via the source circuit <NUM>.

The lens-side control unit <NUM>, connected to the V33 (B) terminal, operates at a voltage lower than or an electric current smaller than the drive system voltage. In the following description, the voltage applied from the source unit <NUM> to the V33 (B) terminal will be referred to as a circuit system voltage. The GND (B) terminal is a ground terminal corresponding to the V33 (B) terminal. The GND (B) terminal is connected with the GND (L) terminal at the interchangeable lens <NUM> via a signal line disposed within the teleconverter <NUM> as has been explained earlier.

It is to be noted that the direction of electric power supply is indicated with arrows in <FIG>. The electric power derived from the circuit system voltage (hereafter will be referred to as circuit system power) is also distributed, via the source unit <NUM>, to the various components disposed in the camera body <NUM>, such as the body-side control unit <NUM>.

The source circuit <NUM> and the switch <NUM> of the teleconverter <NUM> are inserted and connected in series between the V33 (B) terminal at the camera body <NUM> and V33 (L) terminal at the interchangeable lens <NUM>. When the switch <NUM> is in an ON state, the circuit system power is provided to the V33 (L) terminal via the source circuit <NUM>, whereas when the switch <NUM> is in an OFF state, circuit system power supply to the V33 (L) terminal is cut off. Since the circuit system power is provided to the accessory-side control/communication unit <NUM> at a point further on the upstream side relative to the switch <NUM>, the circuit system power supply is sustained regardless of the ON/OFF state of the switch <NUM>.

The switch <NUM> is controlled to sustain an open state until the device ID assignment command data communication (to be explained later) between the accessory-side control/communication unit <NUM> and the body-side communication unit <NUM> is completed after the accessory-side control/communication unit <NUM> is started up. Once the device ID assignment command data communication between the accessory-side control/communication unit <NUM> and the body-side communication unit <NUM> is completed, the switch <NUM> is controlled to take a closed state. As the switch <NUM> enters a closed state, the camera body <NUM> and a next camera accessory (the interchangeable lens <NUM> in this embodiment) become connected with each other, thereby starting circuit system power supply to the camera accessory.

At the interchangeable lens <NUM>, the VBAT (L) terminal is connected with a source circuit <NUM>. The output of the source circuit <NUM> and the PGND (L) terminal are connected to the lens drive unit <NUM> and the aperture drive unit <NUM>. In addition, the V33 (L) terminal is connected with the source circuit <NUM> as has been explained earlier. The output of the source terminal <NUM> and the GND (L) terminal are connected to the various components such as the lens-side control unit <NUM>.

Next, in reference to <FIG>, command data communication will be explained. Through command data communication, data signals can be transmitted/received bidirectionally between the lens-side control unit <NUM> and the body-side control unit <NUM>.

In the following description, a mode of utilization in which the interchangeable lens <NUM> is indirectly mounted at the camera body <NUM> via the teleconverter <NUM> will be referred to as a first utilization example and a mode of utilization in which the interchangeable lens <NUM> is directly mounted at the camera body <NUM> without the teleconverter <NUM> mounted between them will be referred to as a second utilization example. <FIG> is a chart indicating timing with which various signals may be provided in the second utilization example.

In the embodiment, two different types of command data communication, i.e., device ID assignment command data communication and regular command data communication, are carried out. The device ID assignment command data communication is command data communication through which the camera body <NUM> assigns a device ID to a camera accessory such as the interchangeable lens <NUM> or the teleconverter <NUM> mounted at the camera body <NUM>. The regular command data communication is command data communication executed after a device ID is assigned through the device ID assignment command data communication (see <FIG>).

Through a single session of command data communication, a single command packet <NUM> is transmitted from the camera body <NUM> to the camera accessory and then the camera body <NUM> and the camera accessory each transmit and receive a single data packet by exchanging data packets <NUM> and <NUM>.

The command packet <NUM> includes data expressing a request for model name information, data expressing a request for a discriminating signal used to determine whether the device is a master lens or a non-master lens, data indicating the device ID of the partner with which the particular command data communication is to be carried out, data expressing a request for information pertaining to the optical characteristics of the camera accessory, data indicating specific data to be transmitted in a subsequent data packet, data indicating the data length of the subsequent data packet and the like.

The data packet <NUM> transmitted from the camera body <NUM> to the camera accessory contains data indicating the extent to which a movable portion in the camera accessory is to be driven, data used to indicate the operating state within the camera body <NUM>, data indicating the device ID and the like.

The data packet <NUM> transmitted from the camera accessory to the camera body <NUM> contains data constituting the model name information for the camera accessory, data expressing a discriminating signal used to determine whether the camera accessory is a master lens or a non-master lens, data used to indicate the operating state of the movable portion in the camera accessory, data constituting information pertaining to the optical characteristics of the camera accessory, data indicating the magnification factor of the teleconverter <NUM>, data indicating the optical characteristics of a specific interchangeable lens having been mounted at the teleconverter <NUM> and the like.

While explanation is given below by referring to the example presented in <FIG> in which command data communication is carried out between the body-side communication unit <NUM> and the lens-side communication unit <NUM>, command data communication is likewise carried out between the body-side communication unit <NUM> and the accessory-side control/communication unit <NUM>. For command data communication carried out between the body-side communication unit <NUM> and the accessory-side control/communication unit <NUM>, the RDYL signal, the DATAL signal, and the lens-side communication unit <NUM> in the chart presented in <FIG> and in the description will be respectively replaced with the RDYA signal, the DATAA signal and the accessory-side control/communication unit <NUM>.

The lens-side communication unit <NUM> sets the potential of the RDYL signal to L level at the start of command data communication. In addition, upon deciding that a command data communication enabled condition is established, the lens-side communication unit <NUM> sustains the potential of the RDYL signal at L level. Under conditions in which command data communication cannot be carried out, the lens-side communication unit <NUM> sets the level of the RDYL signal to H level.

If the RDYL signal is at L level at a command data communication start (T1), the body-side communication unit <NUM> starts outputting a clock signal <NUM> to be used as a CLK signal. As a result, the clock signal <NUM> is transmitted from the camera body <NUM> to the interchangeable lens <NUM>. The frequency of the clock signal <NUM> may be, for instance, <NUM>.

The body-side communication unit <NUM> also outputs a command packet <NUM> to be used as a DATAB signal in synchronization with the clock signal <NUM>. In <FIG>, the command packet <NUM> is represented by the H level - L level switchover. Once transmission of the command packet <NUM> is completed, the body-side communication unit <NUM> ends the output of the clock signal <NUM>.

The lens-side control unit <NUM> makes a decision as to whether or not a communication error has occurred with respect to the command packet <NUM> by using an error detection signifier (e.g., checksum data) included in the command packet <NUM> having been received by the lens-side communication unit <NUM>. Upon deciding that no communication error has occurred, the lens-side communication unit <NUM> sets the RDYL signal to H level (T2). The lens-side control unit <NUM> then starts first control processing <NUM> based upon the command packet <NUM>.

Once the first control processing <NUM> executed by the lens-side control unit <NUM> is completed, the lens-side communication unit <NUM> is able to set the RDYL signal to L level (T3). As the level of the RDYL signal input to the body-side communication unit <NUM> shifts to L level, the body-side communication unit <NUM> outputs a clock signal <NUM> to be used as a CLK signal.

The body-side communication unit <NUM> also outputs a data packet <NUM> to be used as a DATAB signal in synchronization with the clock signal <NUM>. In <FIG>, the data packet <NUM> is represented by the H level - L level switchover. Once transmission of the data packet <NUM> of a predetermined data length is completed, the body-side communication unit <NUM> ends the output of the clock signal <NUM> (T4).

In response to the clock signal <NUM> input thereto, the lens-side communication unit <NUM> outputs a data packet <NUM> as a DATAL signal in synchronization with the clock signal <NUM>. In <FIG>, the data packet <NUM> is represented by the H level - L level switchover.

The lens-side control unit <NUM> makes a decision as to whether or not a communication error has occurred with respect to the data packet <NUM> by using an error detection signifier (e.g., checksum data) included in the data packet <NUM> having been received by the lens-side communication unit <NUM>. Upon deciding that no communication error has occurred, the lens-side communication unit <NUM> sets the RDYL signal to H level again (T4). The lens-side control unit <NUM> then starts second control processing <NUM> based upon the data packet <NUM>.

In <FIG> is a diagram presenting an example of a structure that may be adopted for the command packet <NUM>, whereas (b) is a diagram presenting an example of a structure that may be adopted for the data packets <NUM> and <NUM>. The command packet <NUM> and the data packets <NUM> and <NUM> each contain synchronization data as the header portion.

The command packet <NUM> is fixed-length data assuming, for instance, an eight-byte length overall. "Dev ID" <NUM> is fixed-length data that include the device ID of the communication partner. Since regular command data communication is executed following device ID assignment command data communication, a command packet <NUM> including the device ID of the communication partner is transmitted through the regular command data communication. Accordingly, data indicating the device ID of the communication partner are set as the "Dev ID" <NUM>. In device ID assignment command data communication, which is executed before a device ID is assigned, on the other hand, a command packet <NUM> is transmitted without specifying a communication partner device ID. A predetermined initial value is set as the "Dev ID" <NUM> in the command packet <NUM> transmitted in the device ID assignment command data communication, and the command packet <NUM> sustains the fixed length.

"CMD" <NUM> is fixed-length data expressing an instruction, a request or the like. The "CMD" <NUM> includes data expressing an instruction or a request issued from the camera body <NUM>. "Length" <NUM> is fixed-length data indicating the data length (i.e., the information volume) of a data packet <NUM> to be transmitted next. Since the data length of the subsequent data packet <NUM> is indicated in the command packet <NUM>, the receiving-side device (the interchangeable lens <NUM> or the teleconverter <NUM>) receiving the data packet <NUM> is able to end the reception of the data packet <NUM> by measuring the data length in reference to that indicated in the "Length" <NUM> after detecting the synchronization data.

The data packets <NUM> and <NUM> are each variable-length data including sets of data of m bytes indicated in the "Length" <NUM>. "DATA1" <NUM>, "DATA2" <NUM>. , "DATAn" m- <NUM> are separate sets of data each assuming a <NUM>-byte length. The information to be transmitted is divided into units of data, i.e., "DATA1" <NUM>, the "DATA2" <NUM>. , each assuming a single byte length. In a data packet <NUM> to be transmitted through device ID assignment command data communication, data indicating a device ID are set in, for instance, the "DATA1" <NUM>. In a data packet <NUM> to be transmitted through regular command data communication, data constituting information originating from the camera accessory are set in the "DATA1" <NUM>, the "DATA2" <NUM>. , the "DATAn" m - <NUM>.

Next, examples of the first control processing <NUM> and the second control processing <NUM> executed during the command data communication shown in <FIG> will be explained.

Assuming that the command packet <NUM> includes, for instance, a drive instruction for a lens <NUM>. The lens-side control unit <NUM> executes the first control processing <NUM> to generate a data packet <NUM> indicating that a drive instruction for a lens <NUM> has been received. Next, the lens-side control unit <NUM> executes the second control processing <NUM> so as to issue an instruction for the lens drive unit <NUM> to move the lens <NUM> by the extent indicated in the data packet <NUM>. As a result, the lens <NUM> moves along the optical axis O. In response to the drive instruction issued by the lens-side control unit <NUM> to the lens drive unit <NUM> so as to move the lens <NUM>, the lens-side communication unit <NUM> sets the RDYL signal to L level to indicate that the second control processing <NUM> is completed (T5).

Alternatively, assuming that the command packet <NUM> includes, for instance, a hotline communication start instruction. In such a case, the lens-side control unit <NUM> executes the first control processing <NUM> so as to generate a data packet <NUM> indicating that a hotline communication start instruction has been received. The lens-side control unit <NUM> then executes the second control processing <NUM> so as to output an instruction for starting a hotline communication to the lens-side communication unit <NUM> and then sets the RDYL signal to L level to indicate that the second control processing <NUM> is completed (T5).

Next, the flow of processing executed for command data communication when the teleconverter <NUM> is mounted as an accessory will be explained. <FIG> is a time chart illustrating the flow of processing for device ID assignment command data communication and for regular command data communication executed after a device ID is assigned. <FIG> shows, in order from top to bottom, an RDYB signal input to the camera body <NUM>, a DATAB signal output from the camera body <NUM>, an RDYA signal output from the accessory-side control/communication unit <NUM>, a DATAA signal output from the accessory-side control/communication unit <NUM>, an RDYL signal output from the lens-side control unit <NUM> and a DATAL signal output from the lens-side control unit <NUM>. In addition, time points are indicated along the horizontal axis in <FIG>. Reference signs having the prefix S in <FIG> are step numbers corresponding to the steps in the processing to be explained in reference to the flowcharts presented in <FIG> and <FIG>. <FIG> presents a flowchart of the processing executed for device ID assignment command data communication. <FIG> presents a flowchart of the processing executed for regular command data communication.

In an overview of the flow shown in <FIG>, during a period of time elapsing from a time point t10 through a time point t20, the camera body <NUM> is engaged in device ID assignment command data communication sequentially with the teleconverter <NUM> and with the interchangeable lens <NUM>. Then, during a time period including and extending beyond the time point t20, the camera body <NUM> is engaged in regular command data communication individually with the interchangeable lens <NUM> or the teleconverter <NUM>.

The body-side communication unit <NUM> carries out device ID assignment command data communication with the accessory-side control/communication unit <NUM> from the time point t10 through a time point t12 and carries out device ID assignment command data communication with the lens-side communication unit <NUM> from a time point <NUM> through the time point t20.

Upon detecting that a camera accessory has been mounted, the body-side control unit <NUM> engages in device ID assignment command data communication with each mounted camera accessory so as to individually assign device IDs to mounted camera accessories. In subsequent regular command data communication, the body-side control unit <NUM> specifies the device ID of the communication partner for each session of command data communication. It is to be noted that the body-side control unit <NUM> in the embodiment assigns a device ID each time a camera accessory mounted state is detected at the mount detection terminal or each time power is turned on. This means that even if a past device ID is held in the storage unit of the body-side control unit <NUM> prior to the device ID assignment command data communication, the communication will be carried out by reassigning a new device ID.

As the interchangeable lens <NUM> is mounted at the camera body <NUM> indirectly via the teleconverter <NUM>, the potential at the LDET (B) terminal becomes lower. The body-side control unit <NUM>, detecting that the potential at the LDET (B) terminal has become lower, provides circuit system power to the V33 (B) terminal at the teleconverter <NUM>. As a result, power is supplied to the accessory-side control/communication unit <NUM>, thereby starting up the accessory-side control/communication unit <NUM> at the time point t10. The accessory-side control/communication unit <NUM>, having been started up, shifts the RDYA signal from L level to H level and then back to L level (S410) so as to notify the camera body <NUM> that it has entered a reception-enabled state with respect to device ID assignment command data communication.

The body-side control unit <NUM>, having been notified by way of the RDYB signal that the teleconverter <NUM> is in a reception-enabled state, outputs the DATAB signal in synchronization with the clock signal <NUM> (S230). This DATAB signal contains a command packet <NUM>, which includes an assignment instruction with respect to device ID assignment to the teleconverter <NUM> and a request to the teleconverter <NUM> for a discriminating signal. The accessory-side control/communication unit <NUM>, having completed the first control processing <NUM> for the command packet <NUM>, shifts the RDYA signal from L level to H level and then back to L level (S425) so as to notify the camera body <NUM> that it is in a reception-enabled state. The body-side communication unit <NUM> outputs the DATAB signal in synchronization with the clock signal <NUM> (S240). The DATAB signal output at this time is a data packet <NUM> that includes the device ID (e.g., a device ID <NUM>) assigned to the teleconverter <NUM>. The accessory-side control/communication unit <NUM> having received the data packet <NUM> executes the second control processing <NUM> so as to store the device ID <NUM> into the storage unit <NUM> or hold the device ID <NUM> in the accessory-side control/communication unit <NUM>.

The accessory-side control/communication unit <NUM> outputs the DATAA signal in synchronization with the clock signal <NUM> (S430). This DATAA signal contains a data packet <NUM> that includes the discriminating signal, the model name information and the like corresponding to the teleconverter <NUM>. In the embodiment, the discriminating signal for the teleconverter <NUM> indicates that it is a non-master lens with, for instance, data "<NUM>" included in the area "DATA_1" <NUM>. Namely, the camera body <NUM>, having received the discriminating signal (<NUM>) from the teleconverter <NUM>, is able to recognize that another device (the interchangeable lens <NUM> in this example) can be mounted in a communication-enabled state on the subject side of the camera accessory (teleconverter <NUM>) with which the camera body <NUM> is currently in communication. The discriminating signal for the teleconverter <NUM> is stored in the storage unit <NUM>. In addition, the camera body <NUM> holds the device ID <NUM> it has assigned to the teleconverter <NUM> within the body-side control unit <NUM> by correlating it to the model name information received from the teleconverter <NUM>.

Having confirmed that the reception of the data packet <NUM> has been completed (S240) and that the transmission of the data packet <NUM> has been completed (S430), the accessory-side control/communication unit <NUM> abandons communication by shifting the RDYA signal from L level to H level and then back to L level (S445) and also cuts off the output of the RDYA signal and the DATAA signal at a time point (t12, S450) that occurs during a predetermined period of time following a time point t11 at which the RDYA signal shifts to L level. In addition, the accessory-side control/communication unit <NUM> turns on the switch <NUM>, i.e., connects the circuit system power provided from the source circuit <NUM> to the interchangeable lens <NUM> (S460).

With the circuit system power connected, power supply to the interchangeable lens <NUM> starts and the lens-side control unit <NUM> is started up at a time point t13. Once the lens-side control unit <NUM> is started up, the interchangeable lens <NUM> is able to engage in device ID assignment command data communication with the camera body <NUM> and the lens-side control unit <NUM> executes processing similar to the processing executed by the accessory-side control/communication unit from the time point t10 through the time point t12. In the embodiment, the discriminating signal for the interchangeable lens <NUM> indicates that it is a master lens with, for instance, data "<NUM>" included in the area "DATA_1" <NUM>. Namely, the camera body <NUM>, having received the discriminating signal (<NUM>) from the interchangeable lens <NUM>, is able to recognize that another device is not mounted in a communication-enabled state on the subject side of the camera accessory (interchangeable lens <NUM>) with which the camera body <NUM> is currently in communication. The discriminating signal for the interchangeable lens <NUM> is stored in the storage unit <NUM>. In addition, the camera body <NUM> assigns a device ID (e.g., device ID <NUM>) to the interchangeable lens <NUM> and holds information it has received from the interchangeable lens <NUM> (e.g., the model name information) and the device ID <NUM> assigned to the interchangeable lens <NUM> into the body-side control unit <NUM> by correlating them with each other. The interchangeable lens <NUM> also stores the assigned device ID <NUM> into the storage unit <NUM> or holds it in the lens-side control unit <NUM>. The body-side control unit <NUM>, having recognized, based upon the discriminating signal, that the device assigned with the device ID <NUM> is a master lens with no other device mounted in a communication-enabled state on the subject side thereof, ends the device ID assignment command data communication.

By executing device ID assignment command data communication as described above, the camera body <NUM> is able to assign device IDs to all the camera accessories mounted in a communication-enabled state and furthermore, is able to hold each device ID it has assigned in correspondence to the model name information it has obtained.

In the embodiment, during the time period elapsing from the time point t10 through the time point t12, the teleconverter <NUM> alone is provided with electric power and is able to engage in device ID assignment command data communication with the camera body <NUM>, so as to receive an instruction for device ID assignment and a request for the discriminating signal. However, the interchangeable lens <NUM>, which is not provided with electric power, cannot carry out device ID assignment command data communication with the camera body <NUM>, and thus does not receive a device ID assignment instruction or a request for the discriminating signal. This means that the accessory-side control/communication unit <NUM> alone is able to transmit the model name information and the discriminating signal corresponding to the subject device to the camera body <NUM>. In response, the camera body <NUM> assigns the device ID <NUM> to the teleconverter <NUM> and holds the information (e.g., the model name information) having been received from the teleconverter <NUM> and the device ID <NUM> assigned to the teleconverter <NUM> in association with each other at the body-side control unit <NUM>. The body-side control unit <NUM> is able to ascertain, based upon the discriminating signal, that the device to which the device ID <NUM> has been assigned is a non-master lens and that another device in a communication-enabled state can be mounted on the subject side thereof, and is thus able to start assignment of the next device ID <NUM>.

The body-side control unit <NUM> having completed the device ID assignment command data communication carries out regular command data communication over a period of time starting at the time point t20. Regular command data communication is carried out individually with either the interchangeable lens <NUM> or the teleconverter <NUM> specified by the camera body <NUM> as a communication partner.

In the example presented in <FIG>, the camera body <NUM> engages in regular command data communication with the teleconverter <NUM> from a time point t23 through a time point t32 and engages in regular command data communication with the interchangeable lens <NUM> over a period of time starting at t33.

The body-side communication unit <NUM>, detecting that the RDYB signal has shifted from L level to H level and then back to L level, outputs a DATAB signal in synchronization with the clock signal <NUM> (step S130). The DATAB signal output at this time contains a command packet <NUM> which includes an instruction or a request for the teleconverter <NUM>. This means that the command packet <NUM> includes the device ID <NUM> corresponding to the teleconverter <NUM>.

The command packet <NUM> is received at both the lens-side communication unit <NUM> and the accessory-side control/communication unit <NUM>. The lens-side communication unit <NUM>, having received the command packet <NUM>, detects that the device ID <NUM>, different from its own device ID <NUM> is included in the command packet <NUM> and cuts off the output of the RDYL signal and the DATAL signal over a predetermined length of time (through t33) starting at a time point t21 at which the reception of the command packet <NUM> is completed (S570). The lens-side communication unit <NUM> is able to ascertain the predetermined length of time over which the signal outputs are to be cut off, since the command packet <NUM> includes the data length of the subsequent data packet <NUM>.

The accessory-side control/communication unit <NUM>, having received the command packet <NUM>, senses that its own device ID <NUM> is included in the command packet <NUM> and sets the RDYA signal output and the DATAA signal output in a communication-enabled state within a predetermined length of time starting from the time point t21, at which the reception of the command packet <NUM> is completed (t23, S530). The accessory-side control/communication unit <NUM> shifts the RDYA signal from L level to H level and then back to L level (S540), so as to notify the camera body <NUM> that it is in a command data communication-enabled state and can therefore, receive the subsequent data packet <NUM>.

The body-side communication unit <NUM>, having been notified by the teleconverter <NUM> that it is in a reception-enabled state, outputs a DATAB signal in synchronization with the clock signal <NUM> (S140). The DATAB signal output at this time contains a data packet <NUM> which includes data and the like needed by the teleconverter <NUM> in order to execute an operation specified in the command packet <NUM>, the reception of which has been completed at the time point t21. The accessory-side control/communication unit <NUM> outputs a DATAA signal in synchronization with the clock signal <NUM> (S550). The DATAA signal output at this time contains a data packet <NUM>, which may include, for instance, information indicating the magnification factor with respect to the focal length of the teleconverter <NUM> and optical characteristics of the lens <NUM>, information indicating the optical characteristics of a specific interchangeable lens having been mounted, and the like.

Subsequently, as the RDYB signal shifts from L level to H level and then back to L level, the body-side communication unit <NUM> outputs a DATAB signal in synchronization with the clock signal <NUM> (S130). The DATAB signal output at this time contains a command packet <NUM> that includes the device ID <NUM> corresponding to the interchangeable lens <NUM>.

The command packet <NUM> is received at both the lens-side communication unit <NUM> and the accessory-side control/communication unit <NUM>. The accessory-side control/communication unit <NUM>, verifying that the device ID <NUM>, different from its own device ID <NUM> is included in the command packet <NUM>, cuts off the outputs of the RDYA signal and the DATAA signal within a predetermined length of time starting at a time point t31 at which the reception of the command packet <NUM> is completed (t32, S570). The lens-side communication unit <NUM> verifies that its own device ID <NUM> is included in the command packet <NUM> and sets the RDYL signal output and the DATAL signal output in a communication-enabled state within a predetermined length of time starting from the time point t31, at which the reception of the command packet <NUM> is completed (t33, S530). The lens-side communication unit <NUM> shifts the RDYL signal from L level to H level and then back to L level (S540), so as to notify the camera body <NUM> that it is in a reception-enabled state.

The body-side communication unit <NUM>, having been notified by the interchangeable lens <NUM> that it is in a reception-enabled state, outputs a DATAB signal in synchronization with the clock signal <NUM> (S140). The DATAB signal output at this time contains a data packet <NUM> which includes data and the like needed by the interchangeable lens <NUM> in order to execute an operation specified in the command packet <NUM>, the reception of which has been completed at the time point t31.

The lens-side communication unit <NUM> outputs at DATAL signal in synchronization with the clock signal <NUM> (S550). The DATAL signal output at this time contains a data packet <NUM>, which may include, for instance, information indicating the optical characteristics of the interchangeable lens <NUM> such as the focal length of the image-capturing optical system <NUM> thereof, information indicating the operating state of a movable portion and the like.

It is to be noted that in the second utilization example, the teleconverter <NUM> is not mounted and the interchangeable lens <NUM> is directly mounted at the camera body <NUM>. Under such circumstances, the processing at the time point t13 and beyond in <FIG> is executed for device ID assignment command data communication. In addition, the processing at the time point t33 and beyond in <FIG> is executed for regular command data communication. In the second utilization example, only one device ID (e.g., the device ID <NUM>) for the interchangeable lens <NUM> is assigned and a command packet transmitted from the camera body <NUM> invariably includes the device ID (device ID <NUM>). Consequently, the interchangeable lens <NUM> is able to receive all the command data output from the camera body <NUM>.

When a plurality of intermediate accessories, e.g., two intermediate accessories, are present between the interchangeable lens <NUM> and the camera body <NUM>, device ID assignment command data communication between a first intermediate accessory mounted at a position closer to the camera body <NUM>, and the camera body <NUM> is started ahead of device ID assignment command data communication with the interchangeable lens <NUM>. Once the device ID assignment command data communication with the first intermediate accessory is completed, device ID assignment command data communication with a second intermediate accessory mounted on the subject side (further away from the camera body <NUM>) of the first intermediate accessory, is started. Namely, device ID assignment command data communication is executed by switching to a new communication partner. Once device ID assignment command data communication with all the intermediate accessories mounted between the camera body <NUM> and the interchangeable lens <NUM> is carried out, device ID assignment command data communication between the camera body <NUM> and the interchangeable lens <NUM> is started.

In other words, when a plurality of intermediate accessories are present, device ID assignment command data communication is carried out by executing processing similar to that executed from the time point t10 through the time point <NUM> in <FIG>, repeatedly before the time point t13.

Next, in reference to <FIG>, the processing executed at the camera body <NUM> for device ID assignment command data communication will be explained.

Upon executing power-on processing in response to a power-on operation, the body-side control unit <NUM> starts device ID assignment command data communication as shown in <FIG>. In step S210, the body-side control unit <NUM> makes a decision as to whether or not the signal at the LDET (B) terminal is at L level, i.e., whether or not the interchangeable lens <NUM> is mounted. If the LDET (B) terminal is at L level, the body-side control unit <NUM> makes an affirmative decision in step S210 and the operation proceeds to step S220 to make a decision based upon a response from the interchangeable lens <NUM>. If, on the other hand, the LDET (B) terminal is at H level, the body-side control unit <NUM> makes a negative decision in step S210 and in this case, the operation waits for the interchangeable lens <NUM> to be mounted while repeatedly executing the processing in step S210.

In step S220, the body-side control unit <NUM> makes a decision as to whether or not the RDYB signal has shifted from L level to H level and then back to L level. Upon sensing such a shift in the RDYB signal, the body-side control unit <NUM> determines that the teleconverter <NUM> is in a reception-enabled state and accordingly, makes an affirmative decision in step S220 before the operation proceeds to step S230. If, on the other hand, the shift described above is not sensed, the body-side control unit <NUM> makes a negative decision in step S220 and repeatedly executes the processing in step S220.

In step S230, the body-side control unit <NUM> executes control for a command packet <NUM> to be transmitted through device ID assignment command data communication. In step S235, the body-side control unit <NUM> makes a decision as to whether or not a shift has occurred in the RDYB signal. If the body-side communication unit <NUM> senses a shift from L level to H level and then back to L level, the body-side control unit <NUM> determines that the teleconverter <NUM> is in a reception-enabled state and accordingly makes an affirmative decision in step S235 before the operation proceeds to step S240. If, on the other hand, the shift described above is not sensed, the body-side control unit <NUM> makes a negative decision in step S235 and repeatedly executes the processing in step S235.

In step S240, the body-side control unit <NUM> executes control for a data packet <NUM> to be transmitted through device ID assignment command data communication and for a data packet <NUM> from the camera accessory to be received through device ID assignment command data communication, before the operation proceeds to step S245. The data packet <NUM> includes data indicating a device ID. The data packet <NUM>, on the other hand, includes the discriminating signal and the model name information pertaining to the camera accessory.

In step S245, the body-side control unit <NUM> makes a decision as to whether or not a shift has occurred in the RDYB signal. Upon sensing that the RDYB signal has shifted from L level to H level and then back to L level, the body-side control unit <NUM> determines that the communication partner is in a reception-enabled state and accordingly, makes an affirmative decision in step S245 before the operation proceeds to step S250. If, on the other hand, the shift described above is not sensed, the body-side control unit <NUM> makes a negative decision in step S245 and repeatedly executes the processing in step S245.

In step S250, the body-side control unit <NUM> holds the device ID having been transmitted and the communication partner model name information in association with each other before the operation proceeds to step S260. Namely, the body-side control unit <NUM> stores information that includes the device ID <NUM>, having been set in the data packet <NUM> in step S240, and the "teleconverter <NUM>", indicating the communication partner, bundled together.

In step S260, the body-side control unit <NUM> makes a decision as to whether or not the discriminating signal indicates a master lens. In other words, the body-side control unit <NUM> makes a decision as to whether the discriminating signal indicates <NUM> or <NUM>. If the discriminating signal indicates a master lens (<NUM>), the body-side control unit <NUM> is able to determine that device IDs have been assigned to all the camera accessories mounted in a communication-enabled state, since another camera accessory in a communication-enabled state is never mounted on the subject side of the master lens in this embodiment. Upon making an affirmative decision in step S260, the body-side control unit <NUM> ends the device ID assignment command data communication shown in <FIG>. Once the device ID assignment command data communication ends, the operation proceeds to execute regular command data communication, as shown in <FIG>.

If the discriminating signal indicates a non-master lens (<NUM>), another camera accessory in a communication-enabled state may be mounted on the subject side of the non-master lens, and thus, the body-side control unit <NUM> cannot determine that device IDs have been assigned to all the camera accessories mounted in a communication-enabled state. The body-side control unit <NUM> thus makes a negative decision in step S260 and the operation returns to step S220. Once the operation returns to step S220, the body-side control unit <NUM> repeatedly executes processing similar to that explained earlier.

Next, in reference to <FIG>, the processing executed by the teleconverter <NUM> for device ID assignment command data communication will be explained.

The accessory-side control/communication unit <NUM>, having started up with circuit system power supplied thereto and having entered a reception-enabled state, shifts the RDYA signal from L level to H level and then back to L level in step S410, and then the operation proceeds to step S420.

In step S420, the accessory-side control/communication unit <NUM> receives the command packet <NUM> from the body-side communication unit <NUM> through the device ID assignment command data communication, before the operation proceeds to step S425. In step S425, the accessory-side control/communication unit <NUM> shifts the RDYA signal from L level to H level and then back to L level as it enters a reception-enabled state for receiving the next data packet <NUM>, before the operation proceeds to step S430.

In step S430, the accessory-side control/communication unit <NUM> receives the data packet <NUM> from the body-side communication unit <NUM> through the device ID assignment command data communication and also transmits a data packet <NUM> to the body-side communication unit <NUM>, before the operation proceeds to step S440.

In step S440, the accessory-side control/communication unit <NUM> stores the device ID, assigned to the teleconverter <NUM> by the camera body <NUM> in the data packet <NUM> received in step S430, into the storage unit <NUM>, and then the operation proceeds to step S445.

In step S445, the accessory-side control/communication unit <NUM> executes the first control processing <NUM> to complete storage of the device ID, and once it enters a reception-enabled state, it shifts the RDYA signal from L level to H level and then back to L level before the operation proceeds to step S450.

In step S450, the accessory-side control/communication unit <NUM> cuts off the outputs of the RDYA signal and the DATAA signal (sets them in a high impedance state) before the operation proceeds to step S460. In step S460, the accessory-side control/communication unit <NUM> turns on the switch <NUM>, i.e., provides circuit system power to the interchangeable lens <NUM>, thereby ending the device ID assignment command data communication executed as shown in <FIG>. Following the device ID assignment command data communication, the operation proceeds to execute the regular command data communication shown in <FIG>.

Next, in reference to <FIG>, the processing executed at the interchangeable lens <NUM> for device ID assignment command data communication will be explained.

The lens-side control unit <NUM>, having been started up with circuit system power supplied thereto and having entered a reception-enabled state, controls the lens-side communication unit <NUM> to shift the RDYL signal from L level to H level and then back to L level in step S310, and then the operation proceeds to step S320.

In step S320, the lens-side control unit <NUM> receives, via the lens-side communication unit <NUM>, the command packet <NUM> transmitted from the body-side communication unit <NUM> through the device ID assignment command data communication, before the operation proceeds to step S325. In step S325, the lens-side control unit <NUM> engages the lens-side communication unit <NUM> to shift the RDYL signal from L level to H level and then back to L level as it enters a reception-enabled state for receiving the subsequent data packet <NUM>, and then the operation proceeds to step S330.

In step S330, the lens-side control unit <NUM> receives, via the lens-side communication unit <NUM>, the data packet <NUM> transmitted from the body-side communication unit <NUM> through the device ID assignment command data communication and also transmits a data packet <NUM> to the body-side communication unit <NUM>, before the operation proceeds to step S340.

In step S340, the lens-side control unit <NUM> executes the first control processing <NUM>, to store the device ID assigned to the interchangeable lens <NUM> by the camera body <NUM> in the data packet <NUM> received in step S330, into the lens-side storage unit <NUM>, and then the operation proceeds to step S345.

In step S345, the lens-side control unit <NUM> completes storage of the device ID and then, as it enters a reception-enabled state, it engages the lens-side communication unit <NUM> to shift the RDYL signal from L level to H level and then back to L level to end the device ID assignment command data communication in <FIG>. Following the device ID assignment command data communication, the operation proceeds to execute the regular command data communication shown in <FIG>.

Next, the processing executed at the camera body <NUM> for regular command data communication will be explained in reference to <FIG>.

In step S <NUM>, the body-side control unit <NUM> selects a communication partner (i.e., a device ID) and then the operation proceeds to step S120. In this situation, communication partner device IDs are held in the body-side control unit <NUM>. When the body-side control unit <NUM> is to issue an instruction or a request to the teleconverter <NUM> for, for instance, drive control, or an error check within the teleconverter <NUM>, it will need to specify the teleconverter <NUM> as the communication partner and accordingly will select the device ID <NUM>. If, on the other hand, it is to issue an instruction or a request to the interchangeable lens <NUM> for, for instance, initialization through which a lens <NUM> is moved to its initial position via the lens drive unit <NUM>, drive control for the lens <NUM> via the lens drive unit <NUM> or an error check within the interchangeable lens, it will need to specify the interchangeable lens <NUM> as the communication partner and thus will select the device ID <NUM>.

In step S120, the body-side control unit <NUM> makes a decision as to whether or not the RDYB signal is at H level. Namely, the body-side control unit <NUM>, sensing that the RDYB signal has shifted from L level to H level and then back to L level following the end of device ID assignment processing or second control processing executed at the camera accessory, makes an affirmative decision in step S120 and the operation proceeds to step S130. If the shift described above is not detected in the signal, the body-side control unit <NUM> makes a negative decision in step S120 and repeatedly executes the processing in step S120.

The body-side control unit <NUM> executes control so as to transmit a command packet <NUM> for regular command data communication, before the operation proceeds to step S135. The command packet <NUM> transmitted at this time includes data specifying the device ID. In step S135, the body-side control unit <NUM> makes a decision as to whether or not a shift has occurred in the RDYB signal. The body-side control unit <NUM>, sensing that the RDYB signal has shifted from L level to H level and then back to L level, determines that the communication partner is in a reception-enabled state and accordingly makes an affirmative decision in step S135 before the operation proceeds to step S140. If, on the other hand, the shift described above is not detected, the body-side control unit <NUM> makes a negative decision in step S135 and repeatedly executes the processing in step S135.

In step S140, the body-side control unit <NUM> executes control so as to transmit a data packet <NUM> for regular command data communication and also to receive a data packet <NUM> from the communication partner camera accessory in regular command data communication, before the operation proceeds to step S145.

In step S145, the body-side control unit <NUM> makes a decision as to whether or not a shift has occurred in the RDYB signal. The body-side control unit <NUM>, sensing that the RDYB signal has shifted from L level to H level and then back to L level, determines that the communication partner is in a reception-enabled state and accordingly makes an affirmative decision in step S145 before the operation proceeds to step S150. If, on the other hand, the shift described above is not sensed, the body-side control unit <NUM> makes a negative decision in step S145 and repeatedly executes the processing in step S145.

In step S150, the body-side control unit <NUM> makes a decision as to whether or not to execute end processing. If, for instance, a power-off operation has been executed, the body-side control unit <NUM> makes an affirmative decision in step S150 and ends the regular command data communication in <FIG> by executing predetermined OFF processing. The device IDs stored in the storage unit <NUM> are erased during the OFF processing.

If end processing is not to be executed, the body-side control unit <NUM> makes a negative decision in step S150 and the operation returns to step S130. Once the operation returns to step S130, the body-side control unit <NUM> repeatedly executes processing similar to the processing described above. It is to be noted that the body-side control unit <NUM> may execute the processing in step S110 to select the communication partner before executing the processing in step S130.

Next, in reference to <FIG>, the processing executed at a camera accessory for regular command data communication will be explained. In the following description, the accessory-side control/communication unit <NUM> or the lens-side control unit <NUM> will be consistently referred to as a "camera accessory control unit".

In step S510, the camera accessory control unit receives a command packet <NUM> for regular command data communication from the body-side control unit <NUM> and then the operation proceeds to step S520.

In step S520, the camera accessory control unit makes a decision as to whether or not the device ID in the command packet <NUM> matches its own device ID. If the device ID included in the command packet <NUM> matches its own device ID, the camera accessory control unit makes an affirmative decision in step S520 and the operation proceeds to step S530. If, on the other hand, the command packet <NUM> does not include the matching device ID, the camera accessory control unit makes a negative decision in step S520 and the operation proceeds to step S570.

If the command packet <NUM> is addressed to itself, the camera accessory control unit sets the RDYA signal and DATAA signal outputs or an RDYL signal and a DATAL signal outputs in a communication-enabled state in step S530 before the operation proceeds to step S540. In step S540, the camera accessory control unit, determining that no error has occurred in reception of the command packet <NUM>, shifts the RDYA signal or the RDYL signal from L level to H level and then back to L level before the operation proceeds to step S545. In step S545, the camera accessory control unit starts the first control processing <NUM> based upon the command packet <NUM> and then the operation proceeds to step S550.

In step S550, the camera accessory control unit receives a data packet <NUM> from the body-side control unit <NUM> and transmits a data packet <NUM> to the body-side control unit <NUM> before the operation proceeds to step S560.

In step S560, the camera accessory control unit, determining that no error has occurred in reception of the data packet <NUM>, shifts the RDYA signal or the RDYL signal from L level to H level and then back to L level before the operation proceeds to step S565. In step S565, the camera accessory control unit starts second control processing <NUM> based upon the control details indicated in the data packet <NUM> and then the operation returns to step S510.

If the command packet <NUM> does not include the matching device ID, the camera accessory control unit makes a negative decision in step S520 and the operation proceeds to step S570. The camera accessory control unit cuts off the output of the RDYA signal or the RDYL signal and the output of the DATAA signal or the DATAL signal in step S570, and then the operation returns to step S510.

In the first utilization example and the second utilization example, the potential at the LDET (B) terminal is sustained at the level matching the potential of the source V33 without becoming lower when a non-master lens alone is mounted at the camera body <NUM> and thus, the camera body <NUM> does not detect that any camera accessory is mounted. In addition, in the first utilization example and the second utilization example, the body-side control unit <NUM> detects that the interchangeable lens <NUM> is mounted by sensing a decrease in the potential at the LDET (B) terminal and by detecting a mounted state via a lens mount/dismount detection pin (not shown) disposed at the body-side mount <NUM>.

As an alternative, the camera body <NUM> may detect that a camera accessory is mounted even when only a non-master lens is mounted and a master lens is not mounted.

In the following description, a utilization example in which power is turned on with the teleconverter <NUM> mounted at the camera body <NUM> and the interchangeable lens <NUM> is mounted later, will be explained as a third utilization example. In the third utilization example, the device ID assignment command data communication in step S220 and subsequent steps may be started when power is turned on at the camera body <NUM> and before the interchangeable lens <NUM> is mounted. In this case, a device ID can be assigned to the teleconverter <NUM> through processing executed from the time point t10 through the time point <NUM> with the teleconverter <NUM> alone mounted at the camera body <NUM> and once the interchangeable lens <NUM> is mounted subsequently, a device ID may be assigned to the interchangeable lens <NUM> alone through processing executed from the time point <NUM> through the time point t20.

The body-side control unit <NUM> carries out hotline communication with a master lens. The master lens (the interchangeable lens <NUM> in the embodiment) includes a movable member disposed therein and transmits information indicating the position and the state of movement of the movable member through hotline communication executed independently of command data communication. In hotline communication, a data signal (HDATA signal) and a clock signal (HCLK signal) are unidirectionally transmitted from the lens-side control unit <NUM> to the body-side control unit <NUM>.

Once a hotline communication start instruction is transmitted through command data communication from the camera body <NUM> to the interchangeable lens <NUM>, hotline data are transmitted through hotline communication from the lens-side communication unit <NUM> to the body-side communication unit <NUM> irrespective (independently) of command data communication until a hotline communication end instruction is transmitted from the camera body <NUM> to the interchangeable lens <NUM> through command data communication. The hotline data transmitted from the lens-side communication unit <NUM> to the body-side communication unit <NUM> may be information pertaining to conditions in the interchangeable lens <NUM> and may include position information indicating the position of the focusing lens among the lenses <NUM>, position information indicating the position of a blur correction lens and information indicating the focusing lens control state. Such information is notated as a lens signal <NUM> in <FIG>, in reference to which an explanation is provided below.

<FIG> is a chart presenting an example of timing with which hotline communication may be carried out between the body-side communication unit <NUM> and the lens-side communication unit <NUM>. Upon receiving a hotline communication start command through command data communication (T6), the lens-side control unit <NUM> starts data generation processing <NUM> to generate data related to lens information. The generation processing <NUM> is processing for obtaining information indicating the conditions at the interchangeable lens <NUM> at, for instance, a <NUM> sampling cycle and for generating a signal carrying the information thus obtained, i.e., the lens signal <NUM>.

Once the generation of the lens signal <NUM> by the lens-side control unit <NUM> is completed (T7), the lens-side communication unit <NUM> outputs a clock signal <NUM> through the HCLK (L) terminal. As a result, the clock signal <NUM> is transmitted from the interchangeable lens <NUM> to the camera body <NUM>. The frequency of the clock signal <NUM> may be, for instance, <NUM>.

The lens-side communication unit <NUM> outputs the lens signal <NUM> as an HDATA signal in synchronization with the clock signal <NUM>. In <FIG>, the lens signal <NUM> is represented by the corresponding H level - L level switchover. Once the transmission of the lens signal <NUM> is completed (T8), the lens-side communication unit <NUM> ends the output of the clock signal <NUM> and returns to a time point T6. The lens-side communication unit <NUM> repeats the processing from the time point T6 to the time point T8 constituting one hotline cycle.

The lens-side communication unit <NUM> repeatedly executes the generation processing <NUM> and the transmission of a lens signal <NUM> at predetermined time intervals (every millisecond) until a communication end instruction (may otherwise be referred to as a transmission-stop instruction) is transmitted from the camera body <NUM> through command data communication. It is to be noted that the length of time from the time point T7 through the time point T8 does not exceed a length amounting to <NUM>% of the length of time between the time point T6 and the time point T8. This means that in a single session of hotline communication, the length of time required for transmission of the lens signal <NUM> will be set to approximately <NUM>% of the entire session and accordingly, the data length of the lens signal <NUM> is set so that the transmission of the lens signal <NUM> does not take up a length of time amounting to <NUM>% or more of the entire session of hotline communication. In addition, the lens-side control unit <NUM> may execute the generation processing <NUM> independently of the HCLK signal and the HDATA signal. In such a case, the generation processing <NUM> does not need to be executed during the time period from the time point T6 through the time point T7.

Through the command data communication and the hotline communication described above, communication in one system and communication in another system can be carried out independently of each other, i.e., communication for one system and communication for the other system can be executed concurrently. In other words, the body-side control unit <NUM> and the lens-side control unit <NUM> are able to start or end hotline communication while command data communication is in progress. In addition, they are able to carry out command data communication while hotline communication is in progress, as well. Thus, the body-side control unit <NUM> is able to continuously obtain information pertaining to the interchangeable lens <NUM> through hotline communication even while command data communication is in progress. Furthermore, since the information pertaining to the interchangeable lens <NUM> can be continuously obtained through hotline communication, any adverse effect that would occur if transmission/reception of a large volume of data were executed through command data communication is averted. Moreover, hotline communication enables the body-side control unit <NUM> to transmit various instructions and requests to the interchangeable lens <NUM> with any timing and to receive information from the interchangeable lens <NUM> with any timing.

The following operational effects are achieved through the embodiment described above.

In the embodiment, the number (<NUM>) of connector terminals via which the camera body <NUM> and the interchangeable lens <NUM> are connected with each other matches the number (<NUM>) of connector terminals via which the teleconverter <NUM> and the interchangeable lens <NUM> are connected with each other, and no any extra terminals are required.

The camera body <NUM> at which the teleconverter <NUM> is mounted includes a body-side terminal group and a source unit <NUM> from which electric power is provided to the teleconverter <NUM> via a V33 (B) terminal to be connected to the power supply signal line on which the switch <NUM> is disposed at the teleconverter <NUM>. Thus, under a condition in which the switch <NUM> is in an open state, the body-side control unit <NUM> provides electric power from the camera body <NUM> to the teleconverter <NUM>, whereas under a condition in which the switch <NUM> is in a closed state, the body-side control unit <NUM> is able to provide electric power from the camera body <NUM> to both the teleconverter <NUM> and the interchangeable lens <NUM>.

(<NUM>) The camera body <NUM> further includes a body-side communication unit <NUM> engaged in communication with the accessory-side control/communication unit <NUM> via a communication terminal in the body-side terminal group. In response to a shift occurring in the RDYA signal or the RDYL signal from L level to H level and then back to L level, the body-side communication unit <NUM> starts device ID assignment command data communication. This structure makes it possible for the camera body <NUM> to assign a device ID to a camera accessory after the camera accessory provided with electric power enters a communication-enabled state.

(<NUM>) In the first utilization example, the source unit <NUM> provides electric power to the interchangeable limbs <NUM> via the V33 (B) terminal for power supply once second control processing <NUM> is completed through device ID assignment command data communication and the switch <NUM> enters a closed state. In addition, the body-side communication unit <NUM> engages in communication with the lens-side communication unit <NUM> via its communication terminal and in response to a shift (L level -> H level -> L level) in the RDYL signal indicating whether or not command data communication is enabled, provided from the interchangeable lens <NUM>, it transmits a command packet <NUM> containing a device ID to the interchangeable lens <NUM>. Thus, the camera body <NUM> is able to assign a device ID to the interchangeable lens <NUM> after the interchangeable lens <NUM>, provided with electric power, enters a communication-enabled state.

(<NUM>) A camera accessory mounted at the camera body <NUM> includes a communication unit engaged in communication with the body-side communication unit <NUM> via a communication terminal. The communication unit in the camera accessory individually switches the RDYL signal or the RDYA signal and the DATAL signal or the DATAA signal to a communication-abandoned state (high impedance state) or to a communication-enabled state. This structure makes it possible to prevent a collision of, for instance, the RDYL signal output from the interchangeable lens <NUM> and the RDYA signal output from the teleconverter <NUM> from occurring on the signal line.

(<NUM>) The communication unit of a camera accessory individually sets input portions (communication terminals DATAB and CLK), to which a DATAB signal and a CLK signal from the camera body <NUM> are input, to a communication-enabled state. As a result, the CLK signal and the DATAB signal output from the camera body <NUM> can be received at the interchangeable lens <NUM> and at the teleconverter <NUM> in an optimal manner.

(<NUM>) In response to a command packet <NUM> input thereto from the camera body <NUM>, containing the device ID assigned to a specific camera accessory, the communication unit of the particular camera accessory switches output portions (communication terminals RDY (L) and DATAL (L)) to a communication-enabled state. In other words, the communication unit switches the output portions to a communication-enabled state only after receiving a command packet <NUM> containing the device ID assigned thereto. Thus, it is possible to prevent, in an optimal manner, a collision of a signal (RDYL or DATAL) output from the interchangeable lens <NUM> and a signal (RDYA or DATAA) output from the teleconverter <NUM>, from occurring on the signal line.

(<NUM>) When a command packet <NUM> from the camera body <NUM> containing a device ID assigned to another camera accessory is input to the communication unit of a camera accessory, i.e., when a command packet <NUM> containing the device ID assigned to itself is not input to the input portion, the communication unit of the camera accessory switches the output portions (the communication terminals RDY (L) and DATAL (L)) to a communication-abandoned state (high impedance state). Thus, it is possible to prevent, in an optimal manner, a collision of a signal (RDYL or DATAL) output from, for instance, the interchangeable lens <NUM> and a signal (RDYA or DATA) output from the teleconverter <NUM> from occurring on the signal line.

(<NUM>) The teleconverter <NUM> mounted between the camera body <NUM> and the interchangeable lens <NUM> includes lens-side terminals disposed at a rear-side terminal holding unit <NUM> located on the side where the camera body <NUM> is present, body-side terminals disposed at a front-side terminal holding unit <NUM> located on the side where the interchangeable lens <NUM> is mounted, a plurality of signal lines via each of which a lens-side terminal and a body-side terminal are connected with each other, and a switch <NUM> disposed on one of the signal lines to open/close the signal line. This structure makes it possible to, for instance, cut off a signal line extending from the camera body <NUM> to the interchangeable lens <NUM> and achieve electric continuity for only a signal line extending from the camera body <NUM> to the teleconverter <NUM> when the switch <NUM> is in an open state and to achieve electric continuity, via the teleconverter <NUM>, for the signal line extending from the camera body <NUM> to the interchangeable lens <NUM> when the switch <NUM> is in a closed state.

(<NUM>) At the teleconverter <NUM>, the switch <NUM> is disposed on at least a signal line through which power is provided from the source unit <NUM> at the camera body <NUM>, among the plurality of signal lines. This structure makes it possible to supply electric power from the camera body <NUM> to the teleconverter <NUM> while the switch <NUM> is in an open state. In addition, when the switch <NUM> is in a closed state, electric power can be provided from the camera body <NUM> to both the teleconverter <NUM> and the interchangeable lens <NUM>.

(<NUM>) The switch <NUM> at the teleconverter <NUM> described above is a normally open contact point, and thus, electric power is provided to the teleconverter <NUM> alone from the camera body <NUM> in an initial state in which the switch <NUM> is open, whereas electric power can be provided from the camera body <NUM> to both the teleconverter <NUM> and the interchangeable lens <NUM> when the switch <NUM> is in a closed state.

(<NUM>) The accessory-side control/communication unit <NUM> at the teleconverter <NUM> described above closes the switch <NUM> after setting the output portions corresponding to the communication signal lines (the signal lines for the RDYA signal and the DATAA signal) to a communication-abandoned state (high impedance state). Thus, even if an RDYL signal from the interchangeable lens <NUM>, to which electric power is provided via the switch <NUM> in a closed state, is output to a communication signal line, the RDYL signal can be prevented from colliding with an RDYA signal to be output from the output portion of the teleconverter <NUM>, on the signal line.

(<NUM>) The camera body <NUM> first assigns device IDs to all the camera accessories mounted thereat in a communication-enabled state and then engages the body-side communication unit <NUM> to transmit a command packet <NUM> and a data packet <NUM> by specifying a device ID through regular command data communication. This structure enables the camera body <NUM> to specify a communication partner and engage in communication with the device assigned with a device ID matching the specified device ID.

The following variations are also within the scope of the present invention, and one of the variations or a plurality of variations may be adopted in combination with the embodiments described above.

While the camera body <NUM> in the embodiment is a mirrorless-type camera body, the present invention may be adopted in conjunction with a single lens reflex-type camera body, instead.

A storage unit in the embodiment may be either a volatile storage unit or a non-volatile storage unit. A device ID may be held for temporary storage in the control units (the body-side control unit <NUM>, the accessory-side control/communication unit <NUM>, the lens-side control unit <NUM>), or it may be temporarily stored in the storage units (the storage units <NUM>, <NUM>, <NUM>). It is to be noted that the device ID only needs to be stored while the particular accessory is mounted, and the device ID does not need to be continuously stored after the accessory is dismounted or after power is turned off.

While the lens drive unit <NUM> in the embodiment drives the focusing lens along the optical axis O, the present invention is not limited to this example and it may drive another member. The plurality of lenses <NUM> may include a zoom lens, and in such a case, a zoom drive unit may be disposed as a lens drive unit <NUM>. In addition, the plurality of lenses <NUM> may include a blur correction lens used to minimize the adverse effects of blur attributable to shaky hand movement or the like and, in such a case, a blur correction drive unit may be disposed as a lens drive unit <NUM>.

While electric power sourced from a drive system voltage is provided to the interchangeable lens <NUM> only and is not provided to the teleconverter <NUM> in the embodiment described above, drive system power may also be provided to the teleconverter <NUM>.

While a single command packet <NUM> includes both a device ID assignment instruction for a camera accessory and an instruction for the camera accessory to transmit a discriminating signal in the embodiment described above, these instructions may instead be transmitted over two separate command packets. In such a case, the camera accessory will separately prepare a data packet <NUM> containing the model name information and a data packet <NUM> containing the discriminating signal.

While device IDs are assigned to all the camera accessories mounted at the camera body <NUM> in the order they are connected to the camera body <NUM> (i.e., in the order starting with the camera accessory connected at the position closest to the camera body <NUM>) in the embodiment described above, the present invention is not limited to this example. In the embodiment, when the teleconverter <NUM> and the interchangeable lens <NUM> are mounted at the camera body <NUM> as shown in <FIG> and <FIG>, the body-side control unit <NUM> assigns a device ID to the teleconverter <NUM> first, and then assigns a device ID to the interchangeable lens <NUM>. This order remains applicable (unchanged) regardless of whether the interchangeable lens <NUM> is mounted at the teleconverter <NUM> after the teleconverter <NUM> only has been mounted at the camera body <NUM> and has thus become connected with the camera body <NUM> as one or the teleconverter <NUM> having become connected as one with the interchangeable lens <NUM> after the interchangeable lens <NUM> has been mounted at the teleconverter <NUM>, is then mounted at the camera body <NUM>.

While power-on processing is executed and device ID assignment command data communication is initiated in response to a power-on operation in the embodiment, the present invention is not limited to this example.

While the teleconverter <NUM> represents an example of a non-master lens in the embodiment described above, a non-master lens does not need to be the teleconverter <NUM>. The non-master lens may instead be a wide converter, a close-up ring or the like. Namely, the teleconverter <NUM> may adopt any mode as long as it constitutes an intermediate accessory that is mounted between the camera body <NUM> and a master lens. It is to be noted that while a lens hood, a front converter and the like can be mounted on the subject side of the master lens, they are not engaged in communication with the camera body <NUM> and thus, will not be a device mounted in a communication-enabled state. In addition, an adapter that converts communication specifications to comply with those of the camera body <NUM> is another example of a master lens. An interchangeable lens conforming to a different set of communication specifications is mounted on the subject side of such an adapter, which engages in communication with the camera body <NUM> to transmit an instruction for the interchangeable lens conforming to the different set of communication specifications by converting the communication specifications corresponding to the camera body <NUM>. Accordingly, the adapter may be regarded to function as a master lens with respect to communication.

It is to be noted that when a device is mounted in a communication-enabled state, the device is able to receive an instruction issued from the camera body <NUM> and make a correct response to the instruction. This means that members such as a lens cap and a hood that can be physically mounted on the subject side of a camera accessory are not "camera accessories that can be mounted in a communication-enabled state" in the embodiment. In addition, while an interchangeable lens conforming to a different set of communication specifications can be mounted at the camera body <NUM> via a mount adapter, the interchangeable lens conforming to the different communication specifications will not be able to make a correct response to an instruction directly received from the camera body <NUM> and the instruction from the camera body <NUM> will need to be converted at the mount adapter. For this reason, the interchangeable lens conforming to the different set of communication specifications is not regarded as a "camera accessory that can be mounted in a communication-enabled state" in the embodiment.

In the embodiment, the accessory-side control/communication unit <NUM> is not connected with the HCLK (B) terminal, the HCLK (L) terminal, the HDATA (B) terminal and the HDATA (L) terminal. This means that the sole communication partner of the camera body <NUM> in hotline communication is the interchangeable lens <NUM>, and the camera body <NUM> and the interchangeable lens <NUM> maintain a one-to-one relationship. Accordingly, the device ID of the communication partner for hotline communication is not specified, although the present invention is not limited to this example.

In the embodiment, a single teleconverter <NUM> is mounted as an intermediate accessory, however, a plurality of intermediate accessories may be mounted. In addition, an upper limit (e.g., <NUM>) may be set with respect to the number of intermediate camera accessories that can be mounted.

While an embodiment and variations thereof have been described above, the present invention is in no way limited to the particulars of these examples. Accordingly, the scope of the present invention is to be determined with reference to the appended claims.

Claim 1:
A camera accessory (<NUM>), at which light from a subject enters, detachably mountable at a camera body (<NUM>), comprising:
a communication unit (<NUM>) that communicates with the camera body (<NUM>); and
a first storage unit (<NUM>) that stores a discriminating signal indicating that another device capable of communicating with the camera body is not mountable on a subject side of the camera accessory, wherein:
the communication unit transmits the discriminating signal to the camera body.