Projection optical system and projection type image display device
AssigneeSeiko Epson Corporation
InventorKoji SHIOKAWA
Life of this patent
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Abstract
A projection optical system includes a first lens unit and a second lens unit interposing an intermediate image therebetween. The first lens unit includes two aspherical lenses (a first lens unit first lens and a first lens unit ninth lens), and a first lens unit cemented lens. The projection optical system satisfies the following Conditional Expressions (1) and (2) when the number of lens elements of the first lens unit and the number of lens elements of the second lens unit are set to be Num1 and Num2, respectively. In addition, refractive indexes and Abbe numbers of three lenses constituting the first lens unit cemented lens satisfy a predetermined conditional expression. Num2≤7 (1) 1.5≤Num1/Num2≤2.5 (2)
Claims16
A projection optical system comprising:
- a first lens unit that conjugates an enlargement-side image forming surface positioned on an enlargement side and an intermediate image;
- and
- a second lens unit that conjugates the intermediate image and a reduction-side image forming surface positioned on a reduction side,
- wherein the first lens unit includes at least two aspherical lenses and a cemented lens formed by bonding three lenses to each other,
- the cemented lens includes a first positive lens, a negative lens, and a second positive lens toward a side of the intermediate image from a side of the enlargement-side image forming surface, and
- all of the following Conditional Expression (1) to Conditional Expression (6) are satisfied when the number of lens elements of the first lens unit is set to be Num1, the number of lens elements of the second lens unit is set to be Num2, a refractive index of the first positive lens is set to be n1, an Abbe number of the first positive lens is set to be νd1, a refractive index of the negative lens is set to be n2, an Abbe number of the negative lens is set to be νd2, a refractive index of the second positive lens is set to be n3, and an Abbe number of the second positive lens is set to be νd3:
- Num2≤7 (1)
- 1.5≤Num1/Num2≤2.5 (2)
- n2−n1>0.15 (3)
- n2−n3>0.2 (4)
- νd1−νd2>30 (5)
- νd3−νd2>30 (6).
Dependencies are inferred from the claim text.