JPH0490253A - Color separation unit - Google Patents

Abstract

PURPOSE:To realize an inexpensive color separate unit with ease of position adjustment by employing a prism respectively able to make plural image forming positions after color separation close at a distance of several tens of mum while keeping the fundamental property of a Kosters prism. CONSTITUTION:A prism 4 being a component of a color separate unit is a combined triangle prism in which two same triangle prisms are connected and when a dichroic film of red light reflection, e.g. is provided to an adhered face 4a, red information of an original is sent to a light receiving element face 5a and original cyan information is sent to a light receiving element face 5a. Since a red light R1 and a cyan light R2 are made incident in the light receiving face of a line CCD at an angle of beta, a distance delta between the prism and the line CCD is set to a desired value, then an interval gamma of an image forming position is set to a desired value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color separation unit used in a reading optical system of an image scanner or a digital color image forming apparatus.

[Conventional technology]

Generally, in a reading optical system of an image scanner or a digital color image forming apparatus, an optical image of color image information on the document surface obtained by exposure scanning of an illumination system is used.
After passing through the imaging system, the light is separated by a color separation means installed around the optical axis, and an image is formed on a solid-state imaging device such as a line CCD for each spectral light, and the document information is color-separated. and converts it into an electrical signal.

Conventionally, as the above-mentioned color separation means, a method of separating light using a prism has been adopted.
An isosceles triangular joined prism called a Kester prism is used, and this Kester prism and two or three
A color separation unit having a configuration in which line CCDs are combined is known (Japanese Patent Application Laid-open No. 1-140857,
-147955, JP-A-1-147954, JP-A-1-192258, etc.).

As shown in Figure 10, the Kester prism has the shape of a 60" equilateral triangular prism with a semi-transparent mirror in the center, and the light incident perpendicularly to the incident surface is divided into 2 The system is divided into two parallel lights and emitted.Therefore, the lights in the system are parallel and have no optical path difference, making it resistant to vibrations.

[Problem to be solved by the invention]

Next, a conventional example of a color separation unit using this Kester prism and its drawbacks will be explained with reference to FIG.

In the example shown in FIG. 11, one Kester prism 12 and two line CCDs 14C and 14R constitute a color separation unit. The cemented surface of the prism 12, indicated by reference numeral 13, is a dichroic mirror that reflects cyan light, and the cyan light reflected by the cemented surface 13 is reflected by the first line CGD1.
4C and transmits cyan information. Furthermore, the light that has passed through the joint surface 13 contains only red information, and is received by the second line CCD 14R, thereby transmitting the red information.

In this color separation unit, since the two lines CCD 14C and 14R are arranged separately with respect to the Kester prism 12, both lines CGDI4 with respect to the reading position
G, 14R must match. For example, line CCDs with a pitch of 77zm are connected to line CCDs 14C and 14R.
If this were to be used, the matching accuracy of the line CCDs 14C and 14H would need to be 7 μm or less, and mechanical adjustment would require an extremely high-precision adjustment mechanism, resulting in an expensive color separation unit. Furthermore, since a vR adjustment mechanism is required, the reading position of the line CCDs 14C and 14R tends to fluctuate due to changes over time.

Furthermore, when using a general Kester prism as shown in Fig. 11, two line CCDs as mentioned above are required in principle, but this is because the critical angle is used to spread the beam within the desired beam. This is to protect vertical incidence and vertical exit from the prism. Therefore, if an axial Kester prism is used, as shown in Fig. 11, the red and cyan image formation positions after color separation will be separated, and the positions of the two line CCDs must be individually adjusted with high precision. It will stop happening.

Recently, due to the development of line CCD manufacturing technology, a multi-line CCD in which a plurality of lines of light-receiving surfaces are provided in one package has been announced.

Using this CCD eliminates the need for adjustments, etc., as mentioned above.
An inexpensive color separation unit can be provided. However, the line spacing of a multi-line CCD is small, and in a color separation unit using a Kester prism as shown in FIG. 11, the red and cyan imaging positions are separated by nine degrees, so a multi-line CCD cannot be applied as is.

The present invention has been made in view of the above circumstances, and proposes a prism that can bring multiple image formation positions after color separation close to a distance of several tens of Itm while maintaining the basic properties of the Kester prism. This prism and multiple lines C
The purpose is to provide an inexpensive color separation unit using a CD.

[Means for Solving the Problem] In order to achieve the above object, the invention according to claim 1 of the present invention forms an image of document information on a line CCD using an illumination system and an imaging system, and converts the document information into an electrical signal. In the reading optical system for converting the image to It is a color separation 22 bit for a reading optical system that separates into color information, and the above prism has three corners of the base of a triangular prism, α and 2.
α, 180-3α, and when the critical angle is θ, the surfaces facing each corner 2α of two identical triangular prisms satisfying θ≦2α, α<30 are It is characterized by using a joined triangular prism formed by joining.

Further, the invention according to claim 2 of the present application provides a reading optical system that images document information on a line CCD using an illumination system and an imaging system and converts the document information into an electrical signal. A color separation unit for a reading optical system in which a prism is arranged so that the longitudinal direction of the line CCD and the longitudinal direction of the prism coincide with each other, and the prism and the line CCD separate document information into information of multiple colors. The prism is characterized in that it is composed of a prism for the purpose of color separation and a prism for the purpose of bending the optical path after color separation and emitting it at an arbitrary angle.

〔Example〕

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 1 shows an example of a color image scanner constructed using a color separation unit according to the first aspect of the invention.

In FIG. 1, a document placed on a document placement glass 0 is illuminated by a light source 1, and document information is guided to an imaging lens 3 by an optical path bending mirror 2.

The document information that has passed through the imaging lens 3 is guided to a color separation unit consisting of a prism 4 and a line CCD 5 according to the present invention, and after color separation, images are formed on the light receiving element surfaces 5a and 5b of the line CCD 5. .

The prism 4 constituting the color separation unit is a bonded triangular prism made by bonding two triangular prisms of the same shape. If a dichroic film that reflects red, for example, is provided on the bonding surface 4a, the light receiving element surface 5a will be exposed to the original. The red information of the document is transmitted to the light receiving element surface 5b, and the cyan information of the document is transmitted to the light receiving element surface 5b. Although this example shows an example in which document information is read by dividing it into two colors, it is also possible to separate it into three or more colors. Furthermore, as mentioned above, the reference numeral 5 indicates the line CCD, and 5a and 5b are the light-receiving element surfaces. In this example, the light-receiving element surfaces of the two lines are parallel to the longitudinal direction of the prism (perpendicular to the paper surface). The two-line CCD is arranged in a single package and constitutes a two-line CCD.

Next, FIG. 2 is a plan view showing the configuration of a prism used in a color separation unit according to the present invention, and FIG. 3 is a perspective view of the prism.

As shown in FIGS. 2 and 3, the prism of the present invention has two
Two triangular prisms Pi and P2 of the same shape are connected to a joining surface S
It is constructed by joining. In each triangular prism, the three angles on the base of the triangular prism are α and 2α.

It is a triangular prism composed of 180-3α, and satisfies θ≦2α and α<30, where θ is the critical angle.

Here, referring to FIG. 2, white incident light RO to the prism is
An example in which the light is separated into red light R1 and cyan light R2 will be described. Note that the bonding surface S is provided with a dichroic film that reflects red light, for example.

In FIG. 2, on the other hand, the white incident light RO that is perpendicularly incident on the incident surface PIS of the triangular prism P1 has its red component reflected by the junction surface S, and heads toward the PI3 surface at a certain incident angle.

At this time, if the incident angle is larger than the critical angle θ, the red light R1 is totally reflected at the PI3 surface, is directed toward the exit surface PIS', and is emitted from the exit surface PIS' perpendicularly to the exit surface PIS'. The light reaches the light receiving surface of the line CCD at an angle of β. On the other hand, the cyan light R2 from which the red component has been removed at the junction surface S enters the other triangular prism P2, and P
It is reflected by the ZS plane. At this time, if the incident angle is larger than the critical angle θ, it will be totally reflected on the PZS surface and will be directed toward the exit surface P2S'.
The emitted cyan light R2 is emitted from the exit surface P2S' perpendicularly to the exit surface P2S' and reaches the light receiving surface of the line CCD at an angle of β.

In the prism of the present invention, the distance γ between the imaging positions of the incident lights R1 and R2 on the line CCD, which have been color-separated as described above, is
The purpose is to bring the distance between the prism and the line CCD as close as several tens of μm, but as explained above, the red light R1 and the cyan light R2 are incident on the light receiving surface of the line CCD at an angle of β, so the distance between the prism and the line CCD is δ. By setting γ to a desired value, it is possible to set the interval γ between the imaging positions to a desired value.

On the other hand, in the case of the Kester prism used in the conventional color separation unit, α = 30'', as shown in Figure 4.
Therefore, the emitted lights R1 and R2 become parallel.

Therefore, even if the distance δ between the prism and the line CCD is changed, the value of the interval γ between the imaging positions remains constant.

Furthermore, in order to increase the value of γ to several tens of micrometers, for example 70 micrometers, a triangular prism with a -side length of 200 micrometers is required as shown in the figure, which exceeds the capabilities of current polishing technology. In the Koester prism, even when using a triangular prism with a side length of several mm, γ
The value of is several 100 μm.

On the other hand, in the prism of the present invention, α=2 in FIG.
As shown in the example in which the angle is set to 5°, even if a triangular prism with a long negative side length is used, the value of γ can be set to several lOμm. Note that the incident light flux corresponds to the F number of the lens of 4.5.

As described above, in the color separation unit of the present invention, as shown in FIG. By using a joined triangular prism made by joining the faces facing each corner 2α of two identical triangular prisms satisfying θ≦2α and α<30, where the angle is θ, two colors can be produced. Since the separated emitted light beams proceed so as to intersect with each other, by arbitrarily changing the distance δ between the prism and the line CCD, the interval γ between the imaging positions of the two light beams on the light receiving surface of the line CCD can be freely obtained. be able to. Further, by accurately determining α and δ as shown in FIG. 2, γ can be uniquely determined, and furthermore, α and δ can also be determined for a desired γ. Therefore, α, δ, γ
By allocating them to appropriate values, two line CCDs can be housed in one package, and the prism can also serve as a conventional protective glass.

In the explanation of the embodiment, an example was shown in which white light was separated into red and cyan, but a half mirror film was provided on the joint surface S of the prism shown in FIG.
A similar effect can be obtained by providing a dichroic film that reflects red light on S and a dichroic film that reflects cyan light on the surface P2S of the other triangular prism. As described above, there are various methods for performing color separation, but the shape of the prism to achieve the purpose of the present invention needs to satisfy the above-mentioned conditions: θ≦2α, α<30.

In the explanation so far, an example has been described in which white light is separated into two colors, but the same explanation can be made for separation of three or more colors.

Next, FIG. 6 shows an example of a color image scanner constructed using a color separation unit according to the second aspect of the invention.

In FIG. 6, a document placed on a document placement glass 0 is illuminated by a light source 1, and document information is guided to an imaging lens 3 by an optical path bending mirror 2.

The document information that has passed through the imaging lens 3 is guided to a color separation unit consisting of a prism 4' and a line CCD 5 of the present invention, and after being color separated, is imaged on the light receiving element surfaces 5a and 5b of the line CCD 5. Ru.

The prism constituting the color separation unit includes a joined triangular prism 4', which is made by joining two triangular prisms of the same shape, as a color separation prism, and a red-reflecting dichroic film, for example, is applied to the joining surface 4a of this triangular prism. If provided, the red information of the original is transmitted to the light receiving element surface 5a, and the cyan information of the original is transmitted to the light receiving element surface 5b. Although this example shows an example in which document information is read by dividing it into two colors, it is also possible to separate it into three or more colors. Also, as mentioned above,
Reference numeral 5 indicates a line CCD, and 5a and 5b are light-receiving element surfaces. In this example, two lines of light-receiving element surfaces are arranged parallel to the longitudinal direction of the prism (perpendicular to the plane of the paper) and are combined into one. It constitutes a packaged 2-line CCD.

Next, FIG. 7 is a plan view showing the configuration of a prism used in the color separation unit according to the present invention, and FIG. 8 is a perspective view of the prism.

As shown in FIGS. 7 and 8, the prism of the present invention includes a triangular prism 4' for the purpose of one-color separation, and separated light emitted from this triangular prism at narrow intervals (several tens of μm). In this case, an example will be described in which white light RO entering the prism is split into red light R1 and cyan light R2.

In FIG. 7, two triangular prisms P3. Red light R1 is on the bonding surface SO of P3'.
For example, a dichroic film is provided to reflect the light.

Of the white light RO that is perpendicularly incident from the incident surface S1 of one triangular prism P3, the red light R1 is reflected by the junction surface SO, is reflected again by the critical angle by the S1 surface, and is emitted vertically from the 82nd surface. Further, the cyan light R2 passes through the bonding surface SO, is reflected by the critical angle on the SL' plane, and is emitted perpendicularly from the S2' plane. The light separated into two colors in this way is passed through a prism 4''(P4.P4') for refraction of the optical path, as shown in the figure, to
The light is angled and focused by the 4' plane.

The purpose of the prism of the present invention is to bring the distance γ between the imaging positions of the incident lights R1 and R2 onto the light-receiving surface of the line CCD close to several tens of μm. and cyan light R2 pass through prism 4 for optical path refraction.
” (P4.P4') and enters the light receiving surface of the line CCD, so the prism and the line CCD
By setting the distance δ between D to a desired value, the interval γ between the imaging positions can be set to a desired value.

On the other hand, in the case of the Kester prism used in the conventional color separation unit, as shown in FIG.
1 and R2 are parallel, the distance γ between both optical paths is constant regardless of the distance δ between the prism and the line CCD. In order to set the value of γ to several tens of μm, for example 70 μm, as shown in the figure, - A triangular prism with a side length of 200 μm is required, which exceeds the capabilities of current polishing technology.

In addition, in FIG. 9, the prism of the present invention is used, the interval γ between the imaging positions is 70 μm, and the distance δ between the prism and the line CCD is
An example will be shown in which the angle of incidence on the CCD is 0.5 mm and the angle of incidence on the CCD is 6 degrees. Further, the incident light flux shown in the figure corresponds to a lens F number of 4.5.

As described above, the color separation unit of the invention according to claim 2 of the present application includes a prism for the purpose of color separation as shown in FIGS. By using a prism constructed of prisms that are intended to be attached and ejected, the interval γ between the imaging positions and the distance δ between the prism and the line CCD can be set arbitrarily. Therefore, according to the present invention, since the distance between two line CCDs can be set arbitrarily, the interval between line CCDs can be made very small, such as several tens of μm, and two line CCDs can be combined into one line CCD. It can be easily packed into a package. Furthermore, the prism can also serve as a conventional protective glass.

In the explanation so far, an example has been described in which white light is separated into two colors, but the same explanation can be made for separation of three or more colors.

〔Effect of the invention〕

As explained above, in the inventions recited in claims 1 and 2 of the present application, it is possible to bring a plurality of image formation positions after color separation close to a distance of several tens of μm while maintaining the basic properties of the Kester prism. By using individual prisms, these prisms and a multi-line CCD housed in one package can be combined to provide an inexpensive color separation unit that is easy to position.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a reading optical system showing an example of a color image scanner configured using the color separation unit according to claim 1, and FIG. 2 is a configuration of a prism used in the color separation unit according to claim 1. 3 is a perspective view of the same prism, FIG. 4 is a plan view showing a design example of a conventional Kester prism, and FIG. 5 is a plan view showing a design example of the prism according to claim 1. , FIG. 6 shows a color image scanner constructed using the color separation unit according to claim 2.
A schematic configuration diagram of a reading optical system showing an example, FIG. 7 is a plan view showing the configuration of a prism used in the color separation unit according to claim 2, FIG. 8 is a perspective view of the same prism, and FIG. 10 is a perspective view showing a conventional Kester prism, and FIG. 11 is an explanatory diagram of a color separation unit according to the prior art. 1... Light source, 2... Optical path bending mirror, 3...
・Imaging lens, 4... Junction triangular prism, 4'
... Prism for color separation, 4''... Prism for optical path refraction, 5... Line CCD.

Claims (1)

[Claims] 1. In a reading optical system that images document information on a line CCD using an illumination system and an imaging system and converts the document information into an electrical signal, a line is provided between the imaging system and the line CCD. A color separation unit for a reading optical system, in which a prism is arranged so that the longitudinal direction of the CCD and the longitudinal direction of the prism match, and the prism and the line CCD separate document information into information of a plurality of colors, As a prism, the three corners of the base of the triangular prism are α, 2
A triangular prism composed of α, 180-3α, where the critical angle is θ, the surfaces facing the respective corners 2α of two triangular prisms of the same shape satisfying θ≦2α, α<30. A color separation unit characterized by using a joined triangular prism formed by joining two similar prisms. 2. In a reading optical system that images document information on a line CCD using an illumination system and an imaging system and converts the document information into an electrical signal, there is a prism between the imaging system and the line CCD in the longitudinal direction of the line CCD. A color separation unit for a reading optical system, in which a prism is arranged so that the longitudinal direction of 1. A color separation unit comprising a target prism and a prism that bends an optical path after color separation and emits the light at an arbitrary angle.