JPS604964B2 - Imaging lens system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new imaging lens system in which a conventionally known viscoimage lens system and a dichroic mirror are roughly combined.

A dichroic mirror is a reflective medium that reflects only light in a given wavelength range and transmits light other than the reflected light. The reflective surface is made by depositing multiple layers of dielectric material.

FIG. 1 shows an example of the spectral transmittance characteristics, or in other words, the spectral reflectance characteristics, of such a dichroic mirror.

This dichroic mirror, which has the characteristics shown in Figure 1, reflects all light whose wavelength is less than 500 nm out of the light that is incident on its reflective surface at an incident angle of 45 degrees. If the light is larger than the size of the light, most of it will be transmitted through it. The characteristics shown in Figure 1 are for light incident at an incident angle of 45 degrees, but by changing the thickness of the deposited film, the characteristics shown in Figure 1 can also be obtained for light incident at an incident angle other than 45 degrees. A dichroic mirror with similar characteristics can be obtained.

Furthermore, by using materials with different refractive indexes as materials to be deposited, the spectral characteristics of transmitted light and reflected light can be controlled arbitrarily.

The object of the present invention is to provide such a dichroic mirror,
It is an object of the present invention to provide a novel imaging lens system that is integrated with an imaging lens system.

Hereinafter, the present invention will be described by way of examples with reference to the drawings.

FIG. 2 shows an example of an imaging lens system embodying the present invention.

In the figure, symbols 1, la, 2, 2a, 3, and 3a indicate lenses, respectively.

Lenses 1 and 1a, 2 and 2a, and 3 and 3a each form a pair, and the two lenses forming each pair are optically equivalent and have the same shape.

These lenses, la, 2, 2a, 3, and 3a, have their respective optical axes coincident with each other, and have a plane perpendicular to this shared optical axis G as a plane of symmetry, and perform imaging functions as a lens system with mirror symmetry. The grain is distributed so that it has a certain amount of grain.

Now, the feature of the present invention is that in this example, the mirror surfaces are aligned with the plane of symmetry in the arrangement of these lenses 1, la, 2, 2a, 3, 3a, and the dichroic mirror 4 is interposed. The reason lies in the fact that it is arranged in such a way that the

The dichroic mirror 4 uses a thin glass plate as a support and has multiple dielectric layers deposited on its smooth surface.
It provides a desired spectral transmittance, and therefore, strictly speaking, the refractive index of the thin glass plate serving as the support for the dichroic mirror 4 must be taken into consideration when arranging the lens system.

To avoid this problem, a glass plate equivalent to the support is further superimposed on the vapor-deposited film of the dichroic mirror, and the reflecting surface is sandwiched between the two equivalent glass plates. A possible method is to make the optical properties symmetrical in the direction of the transmitted optical path. However, in practical terms, this point does not pose much of a problem as long as the glass flat plate has a thickness of 2 to 3 mm or less. FIG. 3 shows another example of an imaging lens embodying the present invention.

In the figure, symbols 5, 6, 6a, 7, 7a, 8, and 8a indicate lenses, respectively.

The lenses 6 and 6a, 7 and 7a, and 8 and 8a each form a pair, and the two lenses forming each pair are optically equivalent to each other and have the same shape. Lens 5 is a concave lens having a plane of symmetry perpendicular to the optical axis. lenses 5, 6,
6a. 7, 7a, 8, and 8a have their optical axes coincident with each other, and are connected symmetrically as a lens system with the lens 5 as the center and the plane of symmetry of the lens 5 as the plane of symmetry, in the direction of this shared optical ball ○. Grain is distributed so that it has a visual function.

A feature of the present invention resides in that, in this example, the symmetry plane of the lens 5 is a dichroic mirror.

That is, the lens 5 is divided into two parts 51 and 52 of the same shape by the plane of symmetry, and the dichroic mirror 9 as described above is mounted on the dividing plane of one of the divided parts. The portion on which the dichroic mirror 9 is formed in this way is then bonded to another divided portion by adhesive.

Now, since the imaging lens system shown in FIGS. 2 and 3 has a dichroic mirror on its plane of symmetry,
It has the following characteristics.

That is, depending on the spectral transmission characteristics of the dichroic mirror,
For light in the wavelength range that passes through the dichroic mirror 4 or 9, these imaging lens systems function as a through lens with imaging performance, and the light is reflected by the dichroic mirror 4 or 9. It functions as a mirror lens with imaging properties for the light that is received. After all, the imaging lens system shown in FIGS. 2 and 3 has the functions of a through lens, an in-mirror lens, and a color filter. The present invention
It should be noted that the present invention can be applied to any known lens arrangement in addition to the lens arrangement shown in FIGS. 2 and 3. FIG. 4 shows one example of the use of such an imaging lens system.

That is, FIG. 4 schematically shows only the essential parts of a color electronic copying machine using an imaging lens system according to the present invention.

That is, in FIG. 4, numeral 0 is a manuscript, numeral 11 is a manuscript lectern glass, numerals 12, 13, 16, 17, 18, 19 are reflecting mirrors, numeral 14 is an imaging lens system according to the present invention, numeral 1
5 is a dichroic mirror, 20, 30, 40' photoreceptors, 21, 31, 41 are chargers, 2
2, 32, 42 are developing devices, 60 is a light source lamp, 71, 72, 73, 74 are chargers, 70 is a conveyor belt, 80 is a pair of heat fixing rollers, 90 is a pair of discharge rollers, 91 indicates a tray, and symbol S indicates a recording sheet. The photoreceptors 20, 30, 40 are
Each of the drums is formed into the same drum shape, and the grains are distributed so as to be rotatable in the direction of the arrow, and chargers 21, 31, 41, developing devices 22, 32, 42, etc. are arranged around these drums.

The reflecting mirrors 12, 13, 16, 17, 18, 19, the dichroic mirror 15, and the imaging lens system 14 are connected to the light source lamp 6.
From the illumination section of 0 to the exposure section of each photoreceptor 20, 30, 40, optical paths having the same optical path length are formed.

The imaging lens system 14 acts as a mirror lens for light that exposes the photoreceptor 20, and acts as a through lens for light that exposes the photoreceptors 30 and 40.

In addition, the imaging lens system 14 transmits light that exposes the photoreceptor 20 to
Since it separates it from the incident light, it also functions as a filter. In the imaging lens system 14, it is assumed that the spectral transmittance characteristics of the dichroic mirror provided on the plane of symmetry in the lens arrangement are as shown in FIG. 1 at the incident angle shown in FIG. 4, for example.

In this case, the imaging lens system 14 uses a dichroic mirror as described above for the light that exposes the photoreceptor 20.
Due to its characteristics, it acts as a blue mirror, and the two photoreceptors are thus exposed to the blue spectrum of the light reflected from the document 0.

The light that passes through the imaging lens system 14 has a spectrum ranging from green to red.

Therefore, the spectral transmittance characteristics of the dichroic mirror 15 are
If the incident angle as shown in the figure is selected to transmit red light and reflect light in other wavelength ranges, the dichroic mirror 15 can function as a green mirror for exposing the photoreceptor 30 and as a green mirror for exposing the photoreceptor 30. For exposures of 40, it acts as a red filter. The conveyor belt 70 has a booley 75
, 76, and is disposed from below the photoreceptors 20, 30, 40 so that the upper belt surface is very close to these photoreceptors.

In the space surrounded by the belt 70, the photoreceptors 20, 30,
40, chargers 72, 73, 7, respectively.
4 are arranged. A pair of heat fixing rollers 80 is disposed near the right side of the conveyor belt 70, and a pair of discharge rollers 90 is disposed further near the right side thereof.

Now, the copying process by the color electronic copying machine is performed as follows.

That is, when the original document 0 is placed on the original bridge glass 11 and the device is activated, the light source lamp 60 emits light, and the original document placed on top of it passes through the original podium glass 11. 0 is illuminated in the form of a long and narrow slit. At the same time, the document layer glass 11 starts moving at a predetermined speed in the direction of the arrow, and the photoreceptors 20, 30, and 40 move in the direction of the arrow, respectively.
Rotation is started at an angular velocity such that the speed of movement of the front surface is equal to the speed of movement of document 0.

It should also be noted that a known scanning method may be applied in which the document is scanned by moving the mirrors 12 and 13 at a predetermined speed ratio without moving the document table. At this time, the chargers 21, 31, and 41 cause corona discharge, and the photoreceptor 20
, 30, 40 are uniformly charged.

The reflected light from the original 0 is guided by reflecting mirrors 12 and 13 and enters the imaging lens system 14, and its blue light component is reflected by the dichroic mirror and is reflected onto the photoreceptor 20 by the reflecting mirror 16. A blue image of the document 0 in the illumination section is formed on the photoreceptor 20 by the imaging power of the imaging lens system 14 as an in-mirror lens.

Similarly, a green component image of the document portion is formed on the photoconductor 30, and a red component image of the document portion is formed on the photoconductor 40. As the document 0 moves, the photoconductors 20, 30, and An electrostatic latent image is formed corresponding to the image.

At this time, it should be noted that the efficiency of color separation can be further improved if a conventionally known color filter is delivered near the photoreceptors 20, 30, and 40 and the light is transmitted through the light. I'll keep it. The electrostatic latent image formed on the photoreceptor 20 moves as the photoreceptor 20 rotates, and yellow toner is applied by the developing device 22 to form a yellow visible image on the photoreceptor 20 .

Similarly, the static latent images formed on the photoreceptors 30 and 40 are applied with magenta toner and cyan toner by developing devices 32 and 42, respectively, and are developed into magenta and cyan visible images, respectively. Ru.

Once a visible image is formed on the photoreceptor, pulley 76
begins to rotate in the direction of the arrow, and the conveyor belt 70 rotates.

At this time, the recording sheet S is sent in the direction of the arrow and rides on the conveyor belt 7M, but a charger 7 is placed on the back side of the recording sheet S.
1 discharges and electrostatically presses the recording sheet S against the conveyor belt 70'. The photoreceptors 20, 30, and 40 rotate one after another in synchronization with the conveyance of the recording sheet S by the conveyor belt 701, and the chargers 72, 73, and 74 discharge one after another, and the color visible development on the photoreceptor is recorded. The images are electrostatically transferred onto the sheet S in a superimposed manner, and a color copy image corresponding to original 0 is synthesized on the recording sheet.

It goes without saying that the timing of the transfer must be adjusted so that no color shift occurs on the recording sheet 3. The color copy image formed on the recording sheet S in this way is thermally fixed onto the recording sheet S by a pair of heat fixing rollers, and then the recording sheet S is discharged onto a tray 91 by a pair of discharge rollers. It will be done. Needless to say, after the visible image has been transferred, the photoreceptors 20, 30, 40 are further subjected to removal of residual toner and charge removal by a cleaning device, a charge eliminator layer, etc. (not shown). By using the imaging lens system according to the present invention in the example apparatus described above, the structure of the color copying machine is simplified and the efficiency of color separation is improved.

Furthermore, since the loss of light quantity is significantly smaller than when a secondary color separation filter is used, there are advantages such as the ability to use the light source effectively. Further, since color separation is performed by one scanning exposure and the color separated images are simultaneously recorded on the photoreceptor, there is an advantage that the copying speed is increased. The imaging lens system according to the present invention can be used not only in a color electronic copying machine as described above but also in an information capture section of a color facsimile.

Further, since the imaging lens system according to the present invention has a dichroic mirror disposed at the center, the area of the mirror surface of the dichroic mirror may be small, and it is resistant to environmental changes. Very economical.

[Brief explanation of the drawing]

Figure 1 shows the spectral transmittance characteristics of a dichroic mirror.
Figure 2 shows an embodiment of the present invention in an end view in a cross section including a shared optical axis, and Figure 3 shows another embodiment of the invention in a cross section including a shared optical axis. FIG. 4, which is an end view, schematically shows only the essential parts of an example of a color electronic copying apparatus using the imaging lens system according to the present invention. 1, la, 2, 2a, 3, 3a...lens, 4...dichroic mirror. Rare Figure 2 Figure 4

Claims (1)

[Scope of Claims] 1. A lens system in which a plurality of lenses are arranged mirror-symmetrically with a plane perpendicular to a shared optical axis as a plane of symmetry and provided with an imaging function, wherein the plane of symmetry is a dichroic mirror. An imaging lens system characterized by: 2 An even number of lenses that are paired with each other are arranged mirror-symmetrically with a plane perpendicular to the shared optical axis as the plane of symmetry, and a dichroic mirror is placed at the position of the plane of symmetry of the lens system that has an imaging function. The imaging lens system according to claim 1, characterized in that the imaging lens system is provided with an intervening lens. 3 Centering on a lens with a plane of symmetry perpendicular to the optical axis,
an even number of lenses that are paired with each other and do not include the lens are arranged symmetrically with respect to the plane of symmetry in the direction of a shared optical axis;
The central lens of the lens system that has an imaging function is
2. The imaging lens system according to claim 1, wherein the imaging lens system is divided into two by a plane of symmetry, a dichroic mirror is formed on one of the divided planes by vapor deposition, and then bonded to the other.