Accessory and image pickup apparatus

1. An accessory attachable to and detachable from an image pickup apparatus, the accessory comprising:

a first connector connectable to the image pickup apparatus;

a second connector connectable to the image pickup apparatus; and

an accessory controller configured to communicate with the image pickup apparatus,

wherein the accessory controller, in an initial setting after the accessory is attached to the image pickup apparatus, sends a first detection signal to the image pickup apparatus via the first connector and receives, in response to a second detection signal for detecting that the second connector is attached to the image pickup apparatus, a third detection signal from the image pickup apparatus via the second connector.

2. The accessory according to claim 1 , wherein the accessory controller determines that the accessory is normally attached to the image pickup apparatus when receiving the third detection signal, and that the accessory is not normally attached to the image pickup apparatus when not receiving the third detection signal.

3. The accessory according to claim 2 , wherein the accessory controller issues a notice of an abnormal state when the accessory controller does not receive the third detection signal and when a battery power inserted in the accessory is consumed by a predetermined value or more.

4. The accessory according to claim 1 , wherein the accessory controller determines that the accessory controller receives the third detection signal when the third detection signal has a low level, and that the accessory controller does not receive the third detection signal when the third detection signal has a high level.

5. The accessory according to claim 1 , wherein the first connector includes a terminal configured to communicate a first communication signal between a battery inserted in the accessory and the image pickup apparatus, and

wherein the accessory controller sends the first detection signal to the image pickup apparatus via the terminal in the initial setting.

6. The accessory according to claim 5 , wherein the accessory controller sends the first detection signal corresponding to the first communication signal having a predetermined level when the battery is inserted into the accessory and a battery lid of the accessory is closed.

7. The accessory according to claim 6 , wherein the accessory controller sets a first ON signal to a high level, turns on a first switch, and sets the first communication signal to a low level, when the battery is inserted into the accessory and the battery lid is closed.

8. The accessory according to claim 7 , wherein the accessory controller communicates a second communication signal with the battery by switching a second switch after setting the first communication signal to the low level.

9. The accessory according to claim 8 , wherein the accessory controller controls the second switch so as to enable a communication between the image pickup apparatus and the battery when the accessory controller receives the third detection signal and a communication of the second communication signal is completed.

10. The accessory according to claim 1 , wherein when the accessory is attached to the image pickup apparatus, the first connector is attached to the image pickup apparatus and then the second connector is attached to the image pickup apparatus.

11. The accessory according to claim 1 , wherein the accessory is a battery grip that includes a body portion into which a battery is inserted, and a protrusion portion attachable to a battery compartment in the image pickup apparatus, and

wherein the first connector is provided to the protrusion portion, and the second connector is provided to the body.

12. An image pickup apparatus to which an accessory is detachably attachable, the image pickup apparatus comprising:

a first connector connectable to the accessory;

a second connector connectable to the accessory; and

a camera controller communicating with the accessory,

wherein the camera controller, in an initial setting after the accessory is attached to the image pickup apparatus, receives a first detection signal from the accessory via the first connector, receives a second detection signal when the second connector is attached to the accessory, and sends a third detection signal through the second connector after receiving the first detection signal and the second detection signal.

13. An accessory attachable to and detachable from an electronic apparatus, the accessory comprising:

a first connector connectable to the electronic apparatus;

a second connector connectable to the electronic apparatus; and

an accessory controller configured to communicate with the electronic apparatus,

wherein the accessory controller, in an initial setting after the accessory is attached to the electronic apparatus, sends a first detection signal to the electronic apparatus via the first connector and receives, in response to a second detection signal for detecting that the second connector is attached to the electronic apparatus, a third detection signal from the electronic apparatus via the second connector.

14. The accessory according to claim 13 , wherein the accessory controller determines that the accessory controller receives the third detection signal when the third detection signal has a low level, and that the accessory controller does not receive the third detection signal when the third detection signal has a high level.

15. The accessory according to claim 13 , wherein the first connector includes a terminal configured to communicate a first communication signal between a battery inserted in the accessory and the electronic apparatus, and

wherein the accessory controller sends the first detection signal to the electronic apparatus via the terminal in the initial setting.

16. The accessory according to claim 15 , wherein the accessory controller sends the first detection signal corresponding to the first communication signal having a predetermined level when the battery is inserted into the accessory and a battery lid of the accessory is closed.

17. The accessory according to claim 16 , wherein the accessory controller sets a first ON signal to a high level, turns on a first switch, and sets the first communication signal to a low level, when the battery is inserted into the accessory and the battery lid is closed.

18. The accessory according to claim 17 , wherein the accessory controller communicates a second communication signal with the battery by switching a second switch after setting the first communication signal to the low level.

19. The accessory according to claim 18 , wherein the accessory controller controls the second switch so as to enable a communication between the electronic apparatus and the battery when the accessory controller receives the third detection signal and a communication of the second communication signal is completed.