Optical scanning apparatus and retinal scanning head-mounted display

1. An optical scanning apparatus comprising:

a light source configured to emit light;

a light source driving unit configured to supply a driving current to the light source;

an optical scanning unit configured to scan the light emitted from the light source in accordance with an image signal such that the light is projected onto a projection surface;

a light amount sensor configured to detect an amount of the light;

a current sensor configured to detect the driving current;

a primary stop control unit configured to stop an operation of the light source driving unit when the amount of the light is equal to or exceeds a predetermined amount of light; and

a secondary stop control unit configured to stop supply of the driving current to the light source when a value of the driving current is equal to or exceeds a predetermined threshold;

wherein the primary stop control unit is a laser control unit configured to stop the operation of the light source driving unit when an overcurrent, which is a current greater than or equal to a preset current, is detected as being supplied to the light source,

wherein the secondary stop control unit is a overcurrent detecting unit that includes a current detecting unit configured to detect the value of the driving current and a comparison unit, the comparison unit being configured to compare the value of the driving current to the predetermined threshold and to output a signal for stopping the operation of the light source driving unit when the driving current is equal to or exceeds the predetermined threshold,

wherein an output of the primary stop control unit is supplied to one input of an AND circuit, an output of the secondary stop control unit is supplied to another input of the AND circuit, and an output of the AND circuit is supplied to the light source driving unit, and

wherein the light source driving unit stops the supply of the driving current in accordance with the output of the AND circuit.

2. A retinal scanning head-mounted display comprising:

a light source configured to emit light;

a light source driving unit configured to supply a driving current to the light source;

an optical scanning unit configured to scan the light emitted from the light source in accordance with an image signal such that the light is projected onto a retina of a user;

a light amount sensor configured to detect an amount of the light;

a current sensor configured to detect the driving current;

a primary stop control unit configured to stop an operation of the light source driving unit when the amount of the light is equal to or exceeds a predetermined amount of light; and

a secondary stop control unit configured to stop supply of the driving current to the light source when a value of the driving current is equal to or exceeds a predetermined threshold;

wherein the primary stop control unit is a laser control unit configured to stop the operation of the light source driving unit when an overcurrent, which is a current greater than or equal to a preset current, is detected as being supplied to the light source,

wherein the secondary stop control unit is a overcurrent detecting unit that includes a current detecting unit configured to detect the value of the driving current and a comparison unit, the comparison unit being configured to compare the value of the driving current to the predetermined threshold and to output a signal for stopping the operation of the light source driving unit when the driving current is equal to or exceeds the predetermined threshold,

wherein an output of the primary stop control unit is supplied to one input of an AND circuit, an output of the secondary stop control unit is supplied to another input of the AND circuit, and an output of the AND circuit is supplied to the light source driving unit, and wherein the light source driving unit stops the supply of the driving current in accordance with the output of the AND circuit.

3. An optical scanning apparatus comprising:

a light source configured to emit light;

a light source driving unit configured to supply a driving current to the light source;

an optical scanning unit configured to scan the light emitted from the light source in accordance with an image signal such that the light is projected onto a projection surface;

a light amount sensor configured to detect an amount of the light;

a current sensor configured to detect the driving current;

a first stop control unit configured to stop an operation of the light source driving unit when the amount of the light is equal to or greater than a predetermined amount of light;

a second stop control unit configured to stop an operation of the light source driving unit when a value of the driving current is equal to or greater than a predetermined threshold;

a third stop control unit including a first comparison circuit configured to compare a voltage at a cathode side of the light source to a second threshold, the third stop control unit configured to stop an operation of the light source driving unit when the voltage at the cathode side of the light source falls below the second threshold; and

a fourth stop control unit including a second comparison circuit configured to compare a voltage corresponding to the amount of light detected by the light amount sensor to a first threshold, the fourth stop control unit configured to stop an operation of the light source driving unit when the voltage corresponding to the amount of light detected by the light amount sensor is equal to or greater than the first threshold;

wherein, when (i) the light amount is equal to or greater than the predetermined amount of light, (ii) the value of the driving current is equal to or greater than the predetermined threshold, (iii) the voltage at the cathode side of the light source falls below the second threshold, or (iv) the voltage corresponding to the amount of light detected by the light amount sensor is equal to or greater than the first thresholds at least one of the first stop control unit, the second stop control unit, the third stop control unit, or the fourth stop control unit causes an operation of the light source driving unit to be stopped, causing emission of light from the light source to stop.