JPS5898611U - Optical low pass filter for color signals - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Brief explanation of drawings]

FIG. 1 is a diagram showing how false signals are generated, FIG. 2 is a diagram showing response characteristics to spatial frequencies in the optical low-pass filter and the photoelectric conversion section of the image sensor, and FIG.
The figure shows a false signal when the attenuation pole frequency and the number of elements of an optical low-pass filter element are changed. Figure 5 shows the spatial frequency of the optical low-pass filter shown in Figure 4 and the image sensor combined with it.
- A diagram showing the response, and FIG. 6 is a diagram showing the false signal generated by the combination. In the drawings, reference numeral 11 indicates a response characteristic to a spatial frequency in the photoelectric conversion section of the image sensor, 12 and 13 indicate a false signal characteristic caused by aliasing, and 21. is the characteristic of a single optical filter element with an attenuation pole frequency of 3.58 MHz, 22 is the characteristic of the photoelectric conversion part of the image sensor, and 23 is the characteristic when two optical low-pass filter elements with an attenuation pole frequency of 3.56 MHz are used. Characteristics, 31゛ is attenuation pole 3
．． 58 MHz single optical comb filter element, 32 is a false signal with attenuation pole of 3, 58 ME (z) is a false signal using two optical filter elements, 33 is an attenuation pole of 3.5
8 False signal when using 2' element with MHz ± 0.25 MHz, 34 is one false signal when using three elements with attenuation pole 3.58 MH2 - ± 0.5 MHz and 3.58 MHz, 41
．． 43, 45, 47 are λ/4 phase plates, 42, 44 are optical comb filter elements with a basic attenuation pole of 3.58 MHZ,
46 and 48 are optical comb filter elements with a basic attenuation pole of 7.16 MHz, 51 is the characteristic of the optical low-pass filter having the structure shown in FIG. 4, 52 is the characteristic of the image pickup device to be combined with the optical low-pass filter, and 61 is the color signal. A false signal characteristic due to a component near the spatial sampling frequency, 62 indicates a false signal due to a component near twice the color signal spatial sampling frequency, and 63 indicates a false signal due to a component near three times the color signal spatial sampling frequency.

Claims (1)

[Scope of utility model registration request] Using striped or dot-shaped color separation filters, at least two signals, blue and red, are extracted from one color signal imaging element, and a broadband green signal or luminance signal is extracted from one or more other imaging elements. An optical low-pass filter for color signals inserted into the incident optical path of an image sensor for transmitting signals in a color camera is made of a transparent material with an optical-axial birefringence property, and is made of a transparent material with optical and axial birefringence characteristics, and is capable of separating ordinary light and ordinary light due to its birefringence. An optical system in which the separation direction of the extraordinary light is the horizontal scanning direction, and further, the basic attenuation pole of the spatial frequency caused by separation interference between the ordinary light and the extraordinary light is within ±0.5 MHz of the color signal spatial sampling frequency of the color signal image sensor. A plurality of comb-shaped filter elements are provided via a lambda phase plate made of a transparent material with optical-axial birefringence characteristics, and a plurality of comb-shaped filter elements are provided with a The separation direction of the ordinary light and extraordinary light due to refraction is the horizontal scanning direction, and furthermore, the basic attenuation pole of the spatial frequency caused by the separation interference of the ordinary light and the extraordinary light is at a frequency twice the color signal spatial sampling frequency of the color signal image sensor. Optical for color signals within ±0.5 MHz (characterized in that one or more diamond-shaped filter elements are provided through a λ/4 phase plate made of a transparent material with optical-axial birefringence); low pass filter.