[0776] [5-3. Accessory for Main Unit]



[0777] The information processing system may include an accessory to which the main unit 2 can be attached. An HMD accessory to be described below as an example accessory can be used as a so-called HMD (head mounted display) with the main unit 2 attached thereto.



[0778] FIG. 60 is a diagram showing an example HMD accessory to which the main unit 2 can be attached. An HMD accessory 230 shown in FIG. 60 includes a housing 231 and belts 232a and 232b. One end of the belt 232a is attached to one end of the housing 231, and one end of the belt 232b is attached to the other end of the housing 231. Although not shown in the figure, the other end of the belt 232a can be removably connected to the other end of the belt 232b. Thus, the housing 231 can be mounted on the head of the user by connecting together the two belts 232a and 232b around the head of the user. Note that there is no particular limitation on the mechanism for allowing the HMD accessory 230 to be mounted on the head of the user.



[0779] As shown in FIG. 60, the housing 231 includes two openings 231a. The openings 231a are located so as to face the eyes of the user with the housing 231 mounted on the head of the user. Although not shown in the figure, the HMD accessory 230 includes a lens provided in each of the openings 231a.



[0780] Moreover, as shown in FIG. 60, the housing 231 includes an insertion slot 231b for receiving the main unit 2 attached thereto (or inserted thereinto). That is, the main unit 2 can be attached to the HMD accessory 230 by inserting the main unit 2 into the insertion slot 231b. If the main unit 2 is attached so that the display 12 is facing the openings 231a, the display 12 can be viewed through the lenses through the openings 231a. That is, the housing 231 supports the display 12 so that the user can view the display 12 of the main unit 2.



[0781] With such a configuration, a user can view images on the display 12 when the HMD accessory 230 with the main unit 2 attached thereto is mounted on the head of the user. That is, the HMD accessory 230 with the main unit 2 attached thereto functions as a so-called HMD. Note that the HMD accessory 230 may present images of a wide viewing angle to a user by enlarging the viewing angle of the images on the display 12 through the lenses. This can enhance the sense of immersion for a user looking at the images. Note that the main unit 2 may perform a predetermined conversion process on the images displayed on the display 12 so that appropriate images are viewed through the lenses.



[0782] Note that in the present embodiment, the main unit 2 includes the acceleration sensor 89 and the angular velocity sensor 90, and can calculate the movement and/or the attitude of the main unit 2 based on the detection results of these sensors. Therefore, the main unit 2 can calculate the movement and/or the attitude of the HMD accessory 230 to which the main unit 2 is attached, and perform a predetermined process in accordance with the movement and/or the attitude. Note that the predetermined process, for example, is a process of controlling a virtual camera for producing images to be displayed on the display 12 based on the movement and/or the attitude of the HMD accessory 230, and more specifically is a process of changing the line-of-sight direction of the virtual camera depending on the attitude, for example.



[0783] In other embodiments, if the main unit 2 does not have sensors for sensing the movement and/or the attitude of the main unit 2 (e.g., an acceleration sensor and/or an angular velocity sensor), the HMD accessory 230 may include the sensors. Then, the HMD accessory 230 may transmit the detection results of the sensors (or information obtained by performing a predetermined process on the detection results) to the main unit 2. The main unit 2 may calculate the movement and/or the attitude of the HMD accessory 230 based on the information transmitted from the HMD accessory 230.



[0784] In the present embodiment, the controllers 3 and 4 may be used while they are removed from the main unit 2. Therefore, even with the main unit 2 attached to the HMD accessory 230, the controllers 3 and 4 can be used as controller devices. That is, a user can operate the controllers using the hands while the HMD accessory 230 with the main unit 2 attached thereto is mounted on the head of the user.



[0785] As described above, the information processing device 1 of the present embodiment, with the use of the HMD accessory 230 described above, can be used in a mode in which it is used as an HMD. In the present embodiment, since the controllers can be removed from the main unit 2, it is possible to reduce the weight of the device or devices to be mounted on the head of the user. A user can perform operations using removed controllers.