Image projection device, image protection method, distance measuring device and distance measuring method
First Claim
Patent Images
1. A projection device comprising:
- a variable-focus lens in which focal length can be changed;
a distance-measuring unit that measures the distance from said variable-focus lens to a projection surface to which a light beam that is condensed by said variable-focus lens is irradiated; and
a control unit that controls said variable-focus lens such that the focal length of said variable-focus lens is greater than the distance measured by said distance-measuring unit.
1 Assignment
0 Petitions
Accused Products
Abstract
An image projection device includes: a variable-focus lens (2) in which focal length can be changed; scanning means (3) that scans a projection surface (12) by means of a light beam that is condensed by the variable-focus lens (2); distance-measuring means (9) that measures the distance from the variable-focus lens (2) to the projection surface (12); and control means (4) that controls the variable-focus lens (2) such that the focal length of the variable-focus lens (2) is greater than the distance measured by means of the distance-measuring means (9).
10 Citations
16 Claims
-
1. A projection device comprising:
-
a variable-focus lens in which focal length can be changed; a distance-measuring unit that measures the distance from said variable-focus lens to a projection surface to which a light beam that is condensed by said variable-focus lens is irradiated; and a control unit that controls said variable-focus lens such that the focal length of said variable-focus lens is greater than the distance measured by said distance-measuring unit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
-
-
13. An image projection method for displaying an image by scanning a projection surface by a light beam, that is condensed by a variable-focus lens in which the focal length can be changed, comprising:
measuring the distance from said variable-focus lens to said projection surface and setting in the variable-focus lens a focal length that is greater than the distance that was measured.
-
14. A distance-measuring device comprising:
-
a variable-focus lens in which the focal length can be changed; a scanning unit that scans a detection object surface by means of a light beam that is condensed by said variable-focus lens; a image-pickup unit that picks up a detection object surface that was scanned by said light beam; a speckle contrast calculation unit that, based on image data from said image-pickup unit, calculates speckle contrast that indicates the degree of speckle produced at said detection object surface; and a look-up table unit that, for each of a plurality of different focal lengths to which said variable-focus lens is set, saves characteristic data that indicate changes of said speckle contrast with respect to changes of the distance to said detection object surface from the position of the beam waist of the light beam that is condensed by said variable-focus lens, that refers to the saved characteristic data, and that, based on the focal length of said variable-focus lens that was set at the time of image pickup by said image-pickup unit and the value of the speckle contrast that was calculated in said speckle contrast calculation unit, acquires the distance from said variable-focus lens to said detection object surface. - View Dependent Claims (15)
-
-
16. A distance measuring method comprising:
-
scanning a detection surface by a light beam that is condensed by a variable focus lens in which focal length can be changed to capture an image of the detection surface that is scanned by the light beam; based on image data obtained by capturing said image, calculating speckle contrast that indicates the degree of speckle produced at said detection surface; and referring to a table in which are saved characteristic data that indicate, for each of a plurality of different focal lengths to which said variable-focus lens is set, changes of said speckle contrast with respect to changes of the distance to said detection surface from the position of the beam waist of the light beam that is condensed by said variable-focus lens and calculating the distance from said variable-focus lens to said detection surface based on the focal length of said variable-focus lens that was set at the time of said image pickup and the value of said speckle contrast that was calculated.
-
Specification