Image display apparatus and optical device
An image display apparatus includes: a light source; a screen on which an image is formed when light from the light source is applied thereto; an optical system configured to generate a virtual image by light from the screen; an actuator configured to move the screen in an optical axis direction; a support base supporting the actuator; and a dynamic damper installed on a non-movable part on the support base.
1. An image display apparatus comprising:
a light source;
a screen on which an image is formed when light from the light source is applied thereto;
an optical system configured to generate a virtual image by light from the screen;
an actuator configured to move the screen in an optical axis direction;
a support base supporting the actuator; and
a dynamic damper installed on a non-movable part on the support base,
wherein the actuator includes a suspension configured to support the screen and to move the screen in the optical axis direction.
2. The image display apparatus according to claim 1 , wherein
the actuator includes:
a holder holding the screen;
a coil mounted on the holder; and
a magnetic circuit installed on the support base and configured to apply a magnetic field to the coil,
the magnetic circuit includes a magnetic cover placed on an upper surface of the magnetic circuit and functioning as a yoke for the magnetic circuit, and
the dynamic damper is installed on an upper surface of the magnetic cover.
3. The image display apparatus according to claim 2 , wherein a plurality of dynamic dampers including the dynamic damper are installed on the upper surface of the magnetic cover.
4. The image display apparatus according to claim 3 , wherein the dynamic dampers are installed at positions symmetrical with respect to a center of the magnetic cover, respectively.
5. The image display apparatus according to claim 1 , wherein the support base is supported by a fixed base via a damper.
6. The image display apparatus according to claim 1 , wherein a plurality of dynamic dampers, including the dynamic damper, having different resonance frequencies are installed on the non-movable part.
7. The image display apparatus according to claim 6 , wherein
the plurality of the dynamic dampers each includes a mass member and a damper connecting the mass member to the non-movable part, and
the resonance frequencies of the plurality of the dynamic dampers are made different by uniformly setting weights of the mass members of the respective dynamic dampers and making hardnesses of the respective dampers different from each other.
8. The image display apparatus according to claim 1 , wherein
the actuator drives the screen by electromagnetic force generated between a coil and a magnet,
the image display apparatus further comprises:
a voltage measurement circuit configured to measure a voltage applied to the coil; and
a controller configured to detect an abnormality of the actuator when a voltage outputted from the voltage measurement circuit during operation of the screen is smaller than a predetermined threshold.
9. The image display apparatus according claim 1 , further comprising:
a position detector configured to detect a movement position of the screen; and
a controller configured to detect an abnormality of the position detector, wherein
the position detector includes an encoder configured to detect a position of the screen and output a detection signal, and a multiplication circuit configured to multiply the detection signal outputted from the encoder, and
the controller detects the abnormality of the position detector when a multiplication signal is not outputted from the multiplication circuit.
10. The image display apparatus according to claim 1 , further comprising:
a position detector configured to detect a movement position of the screen;
a servo circuit configured to cause the movement of the screen by the actuator to follow a target waveform based on a signal from the position detector; and
a controller configured to, during servo control of the screen by the servo circuit, prohibit application of the light when a cumulative value of a difference between a drive waveform of the screen and the target waveform is larger than a predetermined threshold.
11. The image display apparatus according to claim 10 , wherein the controller prohibits application of the light based on the difference in a one-frame period for driving the screen.