A plurality of groups are arranged in a light emitting device. Each of the groups includes a plurality of light-emitting elements, a plurality of transistors arranged corresponding to the plurality of light-emitting elements and configured to supply current to the plurality of light-emitting elements, and a group control transistor configured to control current flowing through the plurality of transistors. The plurality of groups have a first group and a second group. The first group has a plurality of light-emitting elements. The second group has a plurality of light-emitting elements. A light-emitting element of the second group is arranged between one light-emitting element of the first group and the other light-emitting element of the first group.

A light-emitting element array includes a semiconductor substrate that is rectangular, a plurality of light-emitting elements on the semiconductor substrate in a row along a first long side of the semiconductor substrate, a plurality of electrode pads on the semiconductor substrate in a plurality of rows along a second long side of the semiconductor substrate, and a plurality of wires on the semiconductor substrate to connect the plurality of light-emitting elements to the plurality of electrode pads. The plurality of electrode pads in the plurality of rows includes a first electrode pad in a row of the plurality of rows closest to the second long side and having a larger area than a second electrode pad in another row of the plurality of rows.

An image forming apparatus includes a photosensitive member that is rotatable, a substrate, a lens array, a holder, and a conductive member provided on the holder. The substrate includes a plurality of light-emitting elements, a driver integrated circuit (IC), and a wiring pattern. The plurality of light-emitting elements is arrayed in a rotational axis direction of the photosensitive member to emit light to which a surface of the photosensitive member is exposed. The driver IC drives the plurality of light-emitting elements. The wiring pattern includes a supply line that supplies power to the driver IC and a ground wire that grounds the driver IC. The lens array collects the light emitted from the plurality of light-emitting elements on the photosensitive member. The holder holds the substrate and the lens array, is grounded, and is made of metal. The conductive member electrically connects the holder and the ground wire.

A print head includes: a mounting board; a light source portion that includes a plurality of light emitting elements provided on one surface of the mounting board; a drive member that is provided on other surface of the mounting board so as to generate a lighting signal and drive the light source portion; and a first temperature detector that is provided on the mounting board, and at least one second temperature detector that is provided at a farther position on the mounting board from the drive member than the first temperature detector; and the drive member includes: a light emitting unit that generates the lighting signal based on a temperature detected by the first temperature detector and a temperature detected by the second temperature detector; and an optical unit that forms an image of light emitted from the light emitting unit.

An image forming device includes an LED head, a main controller board and an LED controller board. The main controller board comprises a main controller, a voltage output circuit, a first voltage terminal, a second voltage terminal. The voltage output circuit outputs a first voltage via the first voltage terminal and the second voltage via the second voltage terminal. The LED controller board comprises a third voltage terminal, a fourth voltage terminal and an LED controller. The third voltage terminal is connected to the first voltage terminal, and the fourth voltage terminal is connected to the second voltage terminal. The LED controller board outputs a voltage according to the first voltage to the LED head. The LED controller is connected to the fourth voltage terminal. A voltage according to the second voltage is input to the LED controller.

In an image forming apparatus, a CPU can perform in a normal mode and a low mode in which a photoconductive drum rotates at a rate m/n times the rotational rate in the normal mode, and lower than the rotational rate in the normal mode. In the low mode, the CPU causes a synchronizing signal generation portion to generate a line synchronizing signal at a cycle 1/m times the cycle of the line synchronizing signal generated in the normal mode, and causes a chip data conversion portion to transmit, to an exposure head, the same image data signal m times and transmit, to the exposure head, an image data signal that brings a light-emitting portion into no light emission n-m times, in synchronization with n number of line synchronizing signals.

An organic light emitting element contains an anode and a cathode, and a light emitting layer arranged between the anode and the cathode, and the organic light emitting element further contains an organic compound layer which is arranged between the cathode and the light emitting layer, and touches the cathode. The organic compound layer contains an organic compound represented by the following general formula [1], where R.sub.1 to R.sub.4 represent substituents. ##STR00001##

An image forming apparatus includes a plurality of light-emitting element array chips including a light-emitting element array and a transfer element array, and a control driver applying a signal to the plurality of light-emitting element array chips. The control driver includes a check terminal that measures signals output from the plurality of light-emitting element array chips, and the control driver determines whether any of the plurality of light-emitting element array chips are defective by analyzing the signals measured at the check terminal.

According to at least one embodiment, a lens mirror array includes a plurality of optical elements. An optical element of the plurality of optical elements includes an incident surface on which light is incident, an emitting surface configured to emit the light incident through the incident surface, at least one reflecting surface reflecting the light incident through the incident surface toward the emitting surface, and a light shielding portion configured to block the light. The incident surface includes an effective surface configured to pass effective light emitted from the emitting surface and a directional surface configured to direct unnecessary light to the light shielding portion.

An optical print head comprises a first light emitting element row, a second light emitting element row, a lens array, a first drive circuit and a second drive circuit. The first light emitting element row includes the arrangement of first light emitting elements. The second light emitting element row includes second light emitting elements arranged in parallel with the first light emitting element row. The lens array concentrates light emitted by the first light emitting elements and the second light emitting elements. The first drive circuit drives each first light emitting element with an identical first current value. The second drive circuit drives each second light emitting element with an identical second current value different from the first current value.