JPH04934B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a projection device including an optical system that forms an image of an object illuminated by an illumination light source on a photoreceptor, the projection device including at least one lens system disposed in an optical path between the illumination light source and the photoreceptor. The present invention relates to a projection device in which one lens is a lens having spectral transmittance characteristics that compensate for the spectral sensitivity characteristics of a photoreceptor. Note that in this specification, the lens refers to a pure lens, excluding those provided with a multilayer interference thin film, and the photoreceptor refers to a photosensitive drum, a photosensitive sheet,
This includes solid-state imaging devices such as CCDs, image pickup tubes such as vidicon, and others. Projection devices with this lens are used as copying machines, facsimiles, television cameras, etc.
Hereinafter, the case where it is used as a copying machine will be explained as an example. Generally, the spectral sensitivity characteristics of photoreceptors used in copying machines are different from the relative luminous efficiency characteristics, and the spectral characteristics multiplied by the spectral wavelength characteristics of the light source that illuminates the original are also different from the relative luminous efficiency characteristics, so the spectral sensitivity characteristics are different from the original. A copy with ivy shading is obtained. For example, if a halogen lamp is used as the light source and a CdS type photoreceptor is used, the filament temperature of 3000°K, which is normally used with halogen lamps, will be reduced.
The emission energy has a maximum value in the infrared region of 800 to 900 nm, and decreases uniformly as it goes to the shorter wavelength side.On the other hand, the spectral sensitivity of the CdS photoreceptor is high in the near infrared region, so it The amount of exposure in the near-infrared range becomes excessive compared to other color ranges such as blue and green.
This causes a phenomenon in which red characters and figures written on the original become faint or disappear completely in the copied image. On the other hand, when a selenium (Se) based photoreceptor and a light source with high emission energy in a short wavelength range are used, it becomes difficult to see blue letters and figures, contrary to when a CdS based photoreceptor and a halogen lamp are used. However, the current situation is that the above problems cannot be solved even when using a CdS-based photoreceptor and a light source with high emission energy in a short wavelength range, or when using a selenium-based photoreceptor and a halogen lamp. It is desirable to compensate for such spectral characteristics (hereinafter referred to as color sensitivity) that differ from the relative luminous sensitivity characteristics to obtain a copy with the same shading as the original. Conventional means for solving this problem include those that use a flat color filter and those that use a multilayer interference thin film known from Japanese Patent Application Laid-open No. 52-60142 and Japanese Utility Model Application No. 52-99331. These are intended to attenuate light in a predetermined wavelength range, for example, in the near-infrared region in the case of the above-described combination of a CdS photoreceptor and a halogen lamp, thereby preventing overexposure in this region. However, when using a flat color filter, there are drawbacks such as parallel plane aberration, high cost due to the addition of one filter component, and large loss of light amount due to surface reflection. On the other hand, when using a multilayer interference thin film, the number of films is generally large, which increases the cost of the vapor deposition process, the spectral characteristics vary depending on the specifications of each optical system, especially the angle of incidence, and the performance changes due to heat, humidity, etc. However, it has the disadvantage of being lacking in durability. By the way, it has been known that a heat absorption filter that attenuates light in the near-infrared region is used as a condenser lens for a slide projector, but this is simply to prevent temperature rise and is described in detail in the following book. What is the point of wavelength selection in a wide wavelength range that matches the spectral sensitivity characteristics of the photoreceptor as in the invention?
Not suggested. Furthermore, it is not used as an imaging lens with predetermined optical performance. A first object of the present invention is to provide a projection device having a lens that compensates for the spectral sensitivity characteristics of a photoreceptor. A second object of the present invention is to provide a wavelength-selective lens system that has high refraction, high dispersion or low dispersion, and has predetermined spectral transmittance characteristics, which are convenient for optical design such as correction of chromatic aberration. It is in. Furthermore, the third object of the present invention is to have excellent devitrification resistance,
The object of the present invention is to provide a novel optical glass that has high refraction, high to low dispersion, and has predetermined spectral transmittance characteristics. By using the present invention, color sensitivity can be compensated more cheaply and stably than in the past. The above-mentioned objects of the present invention can be achieved by the projection apparatus of the present invention described below. In a projection device including an optical system that forms an image of an object illuminated by an illumination light source on a photoreceptor, at least one lens of the lens system is arranged in an optical path between the illumination light source and the photoreceptor. is a lens having spectral transmittance characteristics that compensate for the spectral sensitivity characteristics of the photoreceptor, and the lens has B ₂ O ₃ 25 to 25% by weight.
40%, _SiO2 0~12%, ZrO2 ₀ ~10%, _{La2O3 25} ~
50%, _{Gd2O3 0} ~5%, CaO0~12%, BaO0~10
%, ZnO 0-7%, Ta ₂ O ₅ 0-5%, and
For 100 parts by weight of glass containing 0-3% _WO3 ,
A projection device which is an optical glass to which 0.1 to 1% by weight of CeO ₂ is added and which has optical constants in the range of a refractive index (nd) of 1.65 to 1.85 and an Abbe number (νd) of 57 to 45. In weight%, _B2O3 25-40% _{, SiO2} 0-12%,
ZrO ₂ 0-10%, La ₂ O ₃ 25-50%, Gd ₂ O ₃ 0-5%,
CaO0~12%, BaO0~10%, ZnO0~7%,
CeO ₂ was added in weight% to 100 parts by weight of glass containing 0 to 5% Ta ₂ O 5 and 0 to ₃ % WO ₃ .
0.1~1% added, and refractive index (nd) 1.65~
1.85, an optical glass with an optical constant in the range of Atsube number (νd) 57-45. Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic diagram of a copying machine using the present invention.
The document surface 1 is illuminated by a light source 2 for illumination, and the light from the slit area forms an image fixed by scanning mirrors 3 and 4 that move parallel to the document surface 1 at a speed ratio of 2:1. The light enters a lens 5, and is projected by the imaging lens 5 into a slit shape onto a photoreceptor 8 moving in the direction of the arrow via fixed mirrors 6 and 7. In this example, the wavelength selective optical glass is
It is used for the imaging lens 5. FIG. 2 shows the spectral wavelength characteristics of the light source, the spectral sensitivity characteristics of the photoreceptor, and the spectral transmittance characteristics of the imaging lens. Here, a halogen lamp is used as a light source, and a photoreceptor is used as a
A system using Se is shown. As a so-called synergistic effect obtained by multiplying these three characteristics, a spectral characteristic close to the relative luminous efficiency characteristic can be obtained, as shown by the broken line in the figure. In other words, the spectral transmittance characteristic of the lens system is determined so as to have a characteristic close to this specific luminous efficiency characteristic. When a Se-based photoreceptor is used and a halogen lamp is used as an illumination light source, the lens is required to have spectral transmittance characteristics as shown in FIG.
As a result, a comprehensive spectral sensitivity characteristic close to a specific luminous efficiency characteristic can be obtained. Therefore, for the lens for the above purpose, it has a relatively high refractive index and low dispersion.
There is an absorption edge near 400 nm, and the light absorption property decreases rapidly in the wavelength range of 400 to 500 nm, and
There is a need for a glass that exhibits excellent light transmittance in the 700 nm wavelength range and has excellent devitrification resistance. In the present invention, we propose a novel optical glass that is extremely suitable for meeting the above requirements. That is, this glass is melted in an oxidizing atmosphere to form _stable Ce4 ⁺ ions, and contains 25-40% _B2O3 , 0-12% _SiO2 , _0-10% ZrO2 by weight.
%, La ₂ O ₃ 25-50%, Gd ₂ O ₃ 0-5%, CaO 0-12
%, BaO0~10%, ZnO0~7%, Ta ₂ O ₅ 0~5%,
and 0.1 to 1% by weight of CeO ₂ is added to 100 parts by weight of glass containing 0 to 3% of WO ₃ , and has a refractive index (nd) of 1.65 to 1.85 and an Atsube number (νd) of 57. It has optical constants in the range of ~45. The optical constants (nd,
νd) are listed in Table-1. In addition, optical glass samples of these practical composition examples (each with a thickness of 10
The spectral transmittance curve of (m/m) is shown in FIG.

【table】

[Table] The embodiments of the present invention that compensate for the spectral sensitivity characteristics of Se-based photoreceptors have been described above, but it is also possible to similarly compensate for photoreceptors made of organic semiconductors (OPC). In other words, the spectral sensitivity characteristics of OPCs vary widely depending on the type, but depending on the spectral sensitivity characteristics, the spectral transmission decreases sharply at least in the long wavelength region or short wavelength region, and in some cases, in both wavelength regions. It is sufficient to use a lens made of optical glass that has optical properties. Next, an embodiment of a lens system according to the present invention using the wavelength-selective optical glass described above will be described. In the present invention, the lens system may be placed anywhere in the optical path between the light source and the photoreceptor, but as shown in FIG. 1, the lens system may be placed in the optical path between the original and the photoreceptor. Taking as an example, the case where the lens system is configured as an imaging lens will be explained. Here, from FIG. 4 onwards, the single lens using the above-mentioned wavelength-selective optical glass is shown with diagonal lines. Note that this lens system can be applied to the above-mentioned Se-based, OPC, and other photoreceptors. FIG. 4 shows a first embodiment of the imaging lens according to the present invention. This is a transmission type lens, which is a biconvex lens.
', a biconcave negative lens, and ' are provided symmetrically with respect to the aperture A. The dispersion of the optical glass used for the positive lens, ′, is small, while the negative lens,
The optical glass used in ' has a large dispersion and is combined to form an imaging lens in which chromatic aberration is suppressed and other aberrations are corrected. For the positive lens, for example, normal crown-type optical glass is used, for the negative lens ', normal flint-type optical glass is used, and for the negative lens, wavelength-selective optical glass according to the present invention is used. . Here, the lens data of this example is as follows. The units of the radius of curvature r and the interval d are mm.

[Table] FIG. 5 shows a second embodiment of the imaging lens according to the present invention. Here, wavelength-selective optical glass is used for a single lens. In the wavelength selective lens, it is desirable that the on-axis optical path length and the off-axis optical path length of the effective light beam passing through the lens be approximately equal in terms of the balance of optical path loss due to light absorption, and the meniscus lens as in this embodiment is suitable for this. Note that not only meniscus lenses but also lenses with a small difference in curvature are suitable. By the way, in a system in which the optical path length cannot be balanced using only a single lens, it is possible to use wavelength selective glass for a plurality of single lenses and to balance the total optical path length. The lens data of this example is as follows.

[Table] FIG. 6 is a diagram of a third embodiment of the imaging lens according to the present invention, in which a wavelength-selective optical glass is used as a reflective lens. The second surface of the mirror lens is a mirror surface, and the effective light flux passes through the mirror lens twice. FIG. 7 is a diagram of a fourth embodiment of the imaging lens according to the present invention. This uses wavelength-selective optical glass in a zoom lens that can change the magnification without changing the distance between objects and images. Here, wavelength-selective optical glass is used for the single lens L5. When changing the magnification, the zoom lens moves the entire lens and moves internally to set the optical position and focal length to maintain the imaging relationship, so there is no need for optical path length correction using a mirror. Here, the single lens L5 belongs to the moving group and is internally moved during zooming. The configuration of this embodiment consists of 10 single lenses _L1 to _L10 , which are arranged symmetrically with respect to the aperture A. Here, the lens data of this example is as follows.

【table】

[Table] As described above, according to the present invention, color sensitivity in a copying machine can be compensated for inexpensively and stably. As mentioned at the beginning, the present invention is applicable not only to copying machines but also to facsimile machines,
It is applicable to a wide range of fields such as television cameras, and is extremely useful.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of a copying machine using the present invention, Figure 2 is a schematic diagram of a copying machine using the present invention;
The figure shows the spectral wavelength characteristics of the light source, the spectral sensitivity characteristics of the Se-based photoreceptor, and the spectral transmittance characteristics of the lens system. Figure 3 shows the spectral spectrum of the wavelength-selective optical glass according to the present invention, which is suitable for the Se-based photoreceptor. Diagram of transmittance characteristics, 4th
7 to 7 are diagrams of embodiments of the lens system of the present invention. 1... Original document, 2... Illumination light source, 3, 4... Scanning mirror, 5... Image forming lens, 6, 7... Fixed mirror, 8... Photoreceptor, A... Aperture.

Claims (1)

[Claims] 1. A projection device including an optical system that forms an image of an object illuminated by an illumination light source on a photoreceptor,
At least one lens of the lens system disposed in the optical path between the illumination light source and the photoreceptor is a lens having spectral transmittance characteristics that compensate for the spectral sensitivity characteristics of the photoreceptor, and the lens is , B ₂ O ₃ 25
~40%, SiO2 ₀ ~12%, _Zr02O ~10%, _{La2O3 25}
~50%, _{Gd2O30 ~} 5%, CaO0~12%, BaO0~
10%, ZnO 0-7%, Ta ₂ O ₅ 0-5%, and
For 100 parts by weight of glass containing 0-3% _WO3 ,
It is characterized by being an optical glass containing 0.1 to 1% of CeO ₂ by weight, and having optical constants in the range of a refractive index (nd) of 1.65 to 1.85 and an Atsube number (νd) of 57 to 45. Projection device. 2% by weight, B ₂ O ₃ 25-40%, SiO ₂ 0-12%,
ZrO ₂ 0-10%, La ₂ O ₃ 25-50%, Gd ₂ O ₃ 0-5%,
CaO0~12%, BaO0~10%, ZnO0~7%,
CeO ₂ was added in weight% to 100 parts by weight of glass containing 0 to 5% Ta ₂ O 5 and 0 to ₃ % WO ₃ .
0.1~1% added, and refractive index (nd) 1.65~
1.85, an optical constant having an Atsbe number (νd) in the range of 57 to 45.