Color separating device and color image reading device incorporating same

• US 5,715,095 A
• Filed: 02/21/1995
• Issued: 02/03/1998
• Est. Priority Date: 02/22/1994
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Shimada, Masaya, Hiratsuka, Seiichiro
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): MACK, RICKY LEVERN
• Application Number:
  US08/391,230
• Time in Patent Office: 1,078 Days
• Field of Search: 359/634, 359/583, 359/637, 359/638
• US Class Current: 359/634
• CPC Class Codes: G02B 27/1013 for colour or multispectral image sensors, e.g. splitting an image into monochromatic image components on respective sensors spectral imaging systems G01J
• CPC Class Codes: G02B 27/145 having sequential partially reflecting surfaces

Abstract

In a color separating device, three reflection elements each formed by laminating a dichroic mirror and a total reflection mirror via a transparent layer interposed therebetween are used. The three reflection elements have mutually different spectral characteristics and are arranged to separate incident light reflected from a color original into three color lights without causing a difference in optical paths of the respective color lights. Two of the reflection elements may be used in combination with a condenser lens having principal points whose positions differ depending on wavelengths of light, so as to perform the three-color separation in a similar manner.

Claims

1. A color image reading device comprising:

three reflection elements having mutually different spectral characteristics, each of said three reflection elements having a transmitting/reflecting member for transmitting light having a given wavelength and reflecting light having other than said given wavelength and a reflection mirror for reflecting light, said transmitting/reflecting member and said reflection mirror being separated by transparent layer interposed therebetween to form said reflection element;

a lens for condensing light;

an image sensor having three line sensors arranged in parallel to each other for converting the light into an electric signal; and

said three reflection elements are arranged in a light traveling path between said lens and said image sensor and wherein, assuming that an interval between the adjacent line sensors is s0 and lateral shifts of the light separated in color at said reflection elements in turn are s1, s2 and s3 in order of incidence of the light upon said reflection elements, a relationship among s0, s1, s2 and s3 is given by

space="preserve" listing-type="equation">s1+s2=2s0

space="preserve" listing-type="equation">s2+s3=s0

so as to separate the light into three color lights whose optical paths are equal to each other, and to converge the three color lights onto said sensor.

2. The color image reading device as set forth in claim 1, wherein, assuming that incident angles of the light relative to said reflection elements are θ

1, θ

2 and θ

3 in order of incidence of the light upon said reflection elements, a relationship among θ

1, θ

2 and θ

3 is given by

space="preserve" listing-type="equation">2 p1 p2+p1 p3-p2 p3=0

space="preserve" listing-type="equation">wherein

space="preserve" listing-type="equation">p1=(1/sin 2θ

1)+(1/tan 2θ

1)

space="preserve" listing-type="equation">p2=(1/sin 2θ

2)+(1/tan 2θ

2)

space="preserve" listing-type="equation">p3=(1/sin 2θ

3)+(1/tan 2θ

3)

space="preserve" listing-type="equation">θ

1+θ

2+θ

3=90°

.

3.

3. The color image reading device as set forth in claim 2, wherein, assuming that thicknesses of the transparent layers of said reflection elements are d1'"'"', d2'"'"' and d3'"'"' in order of incidence of the light upon said reflection elements and a refraction factor of each of said transparent layers is n, d1'"'"', d2'"'"' and d3'"'"' are given by

4. A color separating device comprising:

a plurality of reflection elements having mutually different spectral characteristics, each of said reflection elements having a transmitting/reflecting member for transmitting light having a given wavelength and reflecting light having other than said given wavelength and a reflection mirror for reflecting light, said transmitting/reflecting member and said reflection mirror being separated by a transparent layer interposed therebetween to form said reflection element; and

a lens having principal points whose positions differ depending on wavelengths of light, wherein said reflection elements including said transparent layer together with said lens equalizes optical paths for a plurality of given wavelengths of light.

5. The color separating device as set forth in claim 4, wherein each of said transmitting/reflecting members is a dichroic mirror.

6. The color separating device as set forth in claim 4, wherein at least one of said transparent layers is wedge-shaped.

7. The color separating device as set forth in claim 4, wherein each of said transparent layers is an air gap.

8. A color separating device comprising:

two reflection elements having mutually different spectral characteristics, each of said reflection elements having a transmitting/reflecting member for transmitting light having a given wavelength and reflecting light having other than said given wavelength and a reflection mirror for reflecting light, said transmitting/reflecting member and said reflection mirror being separated by a transparent layer interposed therebetween to form said reflection element, said two reflection elements being arranged so as to separate incident light into three color lights; and

a lens having principal points whose positions differ depending on wavelengths of light so as to correct a difference in optical paths which is caused between said respective color lights due to said reflection elements.

9. The color separating device as set forth in claim 8, wherein each of said transmitting/reflecting members is a dichroic mirror.

10. A color image reading device comprising:

two reflection elements having mutually different spectral characteristics, each of said reflection elements having a transmitting/reflecting member for transmitting light having a given wavelength and reflecting light having other than said given wavelength and a reflection mirror for reflecting light, said transmitting/reflecting member and said reflection mirror being separated by a transparent layer;

interposed therebetween to form said reflection element, said two reflection elements being arranged so as to separate incident light into three color lights;

a sensor for converting said respective color lights into corresponding electric signals; and

a lens having principal points whose positions differ depending on wavelengths of light so as to correct a difference in optical paths which is caused between said respective color lights due to said reflection elements.

11. The color image reading device as set forth in claim 10, wherein said sensor is an image sensor having three line sensors arranged in parallel to each other.

12. A color image reading device comprising:

three reflection elements having mutually different spectral characteristics, each of said three reflection elements having a transmitting/reflecting member for transmitting light having a given wavelength and reflecting light having other than said given wavelength and a reflection mirror for reflecting light, said transmitting/reflecting member and said reflection mirror being separated by transparent layer interposed therebetween to form said reflection element;

a lens for condensing light;

an image sensor having three line sensors arranged in parallel to each other for converting the light into an electric signal; and

wherein said three reflection elements are arranged in a light traveling path between said lens and said image sensor, and wherein, assuming that an interval between the adjacent line sensors is s0 and lateral shifts of the light separated in color at said reflection elements in turn are s1, s2 and s3 in order of incidence of the light upon said reflection elements, a relationship among s0, s1, s2 and s3 is given by

space="preserve" listing-type="equation">s1+s2=s0

space="preserve" listing-type="equation">s2+s3=2s0

so as to separate the light into three color lights whose optical paths are equal to each other, and to converge the three color lights onto said sensor.