Title:
TEST PATTERN PROJECTING DEVICE
Document Type and Number:
Japanese Patent JPS62227280
Kind Code:
A
Abstract:
PURPOSE:To correct the coloring of a test pattern image due to diffracted light generated from the dot of the test pattern, and to always project a good test pattern image on a prescribed plane, by arranging an optical member having a spectral function to damp almost transparent light at a center part, and the light of short wavelength area at a peripheral part, at the optical path of a projecting lens. CONSTITUTION:Assuming that the pitch of the dot of a test pattern 3 is set as P, and the wavelength as lambda, a relation that thetaN=sin-<1> (Hlambda/P) is set up in an angle of diffraction thetaN of degree (n). In other words, the angle of diffraction depends on the wavelength lambda, and the longer the wavelength, the larger becomes the angle of diffraction. Assuming that an effective F number on the test Pattern side of a projecting lens 4 is set as F, the angle lambdao of a beam of light made incident on the projecting lens 4 is expressed as follows: lambdao<=sin-<1>1/2 F. Therefore, when the angle of diffraction exceeds lambdao,the diffacted light is not made incident on the projecting lens 4, therefore, the level of gray scale to be photographed is varied according to the wavelength, and it is lowered in a sequence of blue light, green light, and red light. For this reason, a ring-shaped optical member 5 having the spectral function to damp the beam of light at the transparent area whose spectral characteristic is almost flat at the center part, and the beam of light of the short wavelength area mainly at the peripheral part, is arranged in the neighborhood of the diaphragm position of the projecting lens 4, and in this way, the transmitting light quantity of blue light is reduced mainly, and a white balance in the beam of light passing the projecting lens 4 can be maintained in a good state.
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Inventors:
OSHIMA SHIGERU
Application Number:
JP7017586A
Publication Date:
October 06, 1987
Filing Date:
March 28, 1986
Export Citation:
Assignee:
CANON KK
International Classes:
H04N17/00; H04N5/225; (IPC1-7): H04N5/225; H04N17/00
Attorney, Agent or Firm:
Takanashi Yukio