Abstract: A virtual image display device includes a light source unit, a polarization switching unit, an image generation unit, an optical path unit and a projection unit. The polarization switching unit switches a polarization direction of a light beam emitted from the light source unit. The optical path unit includes a first optical path through which the light beam having the first polarization direction travels and a second optical path through which the light beam having the second polarization direction travels. A first virtual image is displayed at a first distance with the light beam that has traveled through the first optical path. A second virtual image is displayed at a second distance farther than the first distance with the light beam that has traveled through the second optical path.

Abstract: The image display device (100) provides images perceivable from the area of the eye box (E), and includes a light source unit (110), a screen (140), a scanning unit (130) and an optical system (155). The screen (140) has a single micro lens array (1) on which multiple micro lenses (3) are arranged. The scanning unit (130) includes a mirror (130a) to reflect beams emitted from the light source unit (110), and swings the mirror (130a) around a pivot center (130c) to scan the beams thereover, thereby generating images. The optical system (155) brings the images formed on the screen (140) to the eye box (E). An angle (?out) formed between a zero-order diffracted beam and a first-order diffracted beam, which are among a luminous flux of beams diffracted by the screen (140) and pass through the center of the eye box (E), is smaller than a minimum visual angle (Vmin).

Abstract: The image display device (100) provides images perceivable from the area of the eye box (E), and includes a light source unit (110), a screen (140), a scanning unit (130) and an optical system (155). The screen (140) has a single micro lens array (1) on which multiple micro lenses (3) are arranged. The scanning unit (130) includes a mirror (130a) to reflect beams emitted from the light source unit (110), and swings the mirror (130a) around a pivot center (130c) to scan the beams thereover, thereby generating images. The optical system (155) brings the images formed on the screen (140) to the eye box (E). An angle (?out) formed between a zero-order diffracted beam and a first-order diffracted beam, which are among a luminous flux of beams diffracted by the screen (140) and pass through the center of the eye box (E), is smaller than a minimum visual angle (Vmin).

Abstract: A virtual image display device includes a light source unit, a polarization switching unit, an image generation unit, an optical path unit and a projection unit. The polarization switching unit switches a polarization direction of a light beam emitted from the light source unit. The optical path unit includes a first optical path through which the light beam having the first polarization direction travels and a second optical path through which the light beam having the second polarization direction travels. A first virtual image is displayed at a first distance with the light beam that has traveled through the first optical path. A second virtual image is displayed at a second distance farther than the first distance with the light beam that has traveled through the second optical path.

Abstract: The present invention provides a method for producing ditrimethylolpropane which is characterized by the following (1) and (2): (1) a distillation still residue separated from purified trimethylolpropane is subjected to re-distillation under specific conditions to obtain a ditrimethylolpropane-containing solution having given contents of bis-TMP and tri-TMP; and (2) when subjecting the ditrimethylolpropane-containing solution to crystallization with an organic solvent, the crystallization is initiated under pressure at a temperature exceeding a boiling point of the organic solvent as measured under normal pressures, and the resulting crystallization product solution is cooled at a temperature drop rate of 2° C./min or less. According to the above method, it is possible to produce a high-purity ditrimethylolpropane from a distillation still residue obtained upon production of trimethylolpropane in a simple, industrially useful manner.

Abstract: The present invention provides a method for producing ditrimethylolpropane which is characterized by the following (1) and (2): (1) a distillation still residue separated from purified trimethylolpropane is subjected to re-distillation under specific conditions to obtain a ditrimethylolpropane-containing solution having given contents of bis-TMP and tri-TMP; and (2) when subjecting the ditrimethylolpropane-containing solution to crystallization with an organic solvent, the crystallization is initiated under pressure at a temperature exceeding a boiling point of the organic solvent as measured under normal pressures, and the resulting crystallization product solution is cooled at a temperature drop rate of 2° C./min or less. According to the above method, it is possible to produce a high-purity ditrimethylolpropane from a distillation still residue obtained upon production of trimethylolpropane in a simple, industrially useful manner.