Display device
View Patent ↗When a polarization axis of a first polarizing plate is parallel to that of a second polarizing plate, a light emitted from a backlight is transmitted, on the other hand, when a polarization axis of the first polarizing plate is orthogonal with that of the second polarizing plate, a light emitted from the backlight is mostly blocked off. A character and scale are constructed by a ½λ phase difference plate, so that the emitted light from the backlight, which enters to the character and scale, has a deflection direction reverse to that of the first polarizing plate. When the light emitted from the backlight is blocked, differently from a conventional artificial (pseudo) black color, a color extremely close to black color is seen. The contrast ratio and visibility are improved.
1. A display device comprising:
a backlight constructed by a light source shining with a predetermined color;
a first polarizing plate arranged in front of the backlight, a ½λ phase difference plate for constructing a character and scale being affixed to the first polarizing plate;
a second polarizing plate arranged between the backlight and the first polarizing plate or in front of the first polarizing plate; and
polarizing plate controlling means for changing a relation between a polarization axis of the first polarizing plate and that of the second polarizing plate to a parallel relation or orthogonal relation.
2. The display device according to claim 1 , wherein the first polarizing plate is fixed and the second polarizing plate is changed by the polarizing plate controlling means.
3. The display device according to claim 2 , wherein the backlight shines with a white color.
4. The display device according to claim 1 further comprising:
a ring-shaped holder for holding the second polarizing plate; and
a worm wheel formed on an outer periphery of the holder, wherein the polarizing plate controlling means transmits driving force from a motor as a driving source to a worm gear mating with the worm wheel so as to rotate the holder.
5. The display device according to claim 1 further comprising:
a ring-shaped holder for holding the second polarizing plate; and
a holder gear formed on an outer periphery of the holder, wherein the polarizing plate controlling means transmits driving force from a motor as a driving source to an output gear mating with the holder gear so as to rotate the holder.
6. The display device according to claim 1 further comprising a third polarizing plate that is smaller than the first polarizing plate, wherein the third polarizing plate is arranged in such a manner that a polarization axis of the third polarizing plate is shifted by 90° with respect to that of the first polarizing plate.
7. The display device according to claim 6 , wherein the display device is applied to a multi-meter and a plurality of sets of the first, second and third polarizing plates are provided correspondingly to respective meters included in the multi-meter.