Patent ID: 7751728

Claim:
A developer cartridge configured to be detachably installed in an image forming apparatus in a first direction, the developer cartridge further comprising: a casing configured to accommodate developer therein, the casing including a first sidewall and a second sidewall, the first sidewall facing the second sidewall in a second direction, the second direction intersecting the first direction; a first light transmitting portion disposed in the first sidewall, the first light transmitting portion including a first light path configured to transmit light from outside of the casing to inside the casing, the first light path being formed to deflect the light; and a second light transmitting portion disposed in the second sidewall, the second light transmitting portion including a second light path configured to transmit light from inside the casing to outside the casing, the second light path being formed to deflect the light, wherein a first edge of the first light transmitting portion is closer to the outside of the casing and a second edge of the first light transmitting portion is closer to the inside of the casing; and a first edge of the second light transmitting portion is closer to the outside of the casing and a second edge of the second light transmitting portion is closer to the inside of the casing; and wherein the first edge of the first light transmitting portion is located in a position different from the second edge of the first light transmitting portion when the first edge of the first light transmitting portion is projected in the second direction; and the first edge of the second light transmitting portion is located in a position different from the second edge of the second light transmitting portion when the first edge of the second light transmitting portion is projected in the second direction.