JPS599045B2 - Magnification synchronized light source in transilluminators, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention configures a plurality of light source units in a projector or the like so that the light source optical axis or light field is always located at the center of the document table, and is capable of performing powerful transmission, precision transmission, and copying. This also aims to speed up copying time.

A conventional projector has several fluorescent lights fixed around a lens parallel to the plane of the document.

Therefore, from the maximum reduction to the maximum enlargement, the light source utilization rate and heavy illumination rate are significantly reduced, and especially during reduction, the optical path is long from the light source to the document surface and then reflected to the projection surface, and the projected image is distorted due to the law of illuminance attenuation. becomes significantly worse. Furthermore, during magnification, the field of view encompassed by the angle of view of the lens is pinched, further reducing the light source utilization rate. This also causes the light rays projected onto surfaces other than the original surface to be diffusely reflected, resulting in ghosts and halation. Furthermore, problems of light intensity attenuation during enlarged projection (same as the increase in exposure multiple in the case of close-up photography) and shallow depth of focus further deteriorate the projected image. For the above reasons, with conventional devices, it is only possible to perform transparent copying on tracing paper and on a clear original, and it is impossible to perform transparent copying using get paper or tracing from a document with low contrast. .

Therefore, it is impossible to improve clarity or depth of focus by narrowing down the lens for manuscripts such as precision design drawings or maps that require clarity over the entire area of the projection surface, and therefore cannot be projected. Moreover, the sharpness and color reproducibility were also insufficient, which limited the performance and applications. Therefore, in the conventional lighting system, even if the number of fluorescent lights or the wattage is increased, it is not possible to increase the light source utilization rate and the heavy illumination rate for a given field area, but it also increases the weight and bulk. Another drawback arises.

Therefore, the present invention aims to increase the light source utilization rate and the heavy illumination rate by changing the angle of the light source so that the light source optical axis is always directed toward the center of the document surface even if the document moves up and down.

Transmission machines are devices that continuously and steplessly move both the lens and document surface up and down with respect to a fixed transmission plate from maximum reduction to maximum enlargement, varying the magnification. The relationship is 111S' From the imaging formula - + - - M, so SS'FS
S... Distance S' between the document surface and the principal point of the projection lens
...Transmission surface and F... Lens focal length M... This is the magnification of the projection, and to illustrate this relationship, as shown in Figure 1, the lens in the projection machine 1 and document a, and the distance between the two trajectories is the interval between them, which is represented by the dotted line locus b.

If we further convert this relationship into an operation relationship with the lens fixed, we get the lens 1 as shown in FIG. and minimum spacing 1. The position where the original is at -0m is the original position at maximum enlargement, and the maximum interval is 1. -01 is the document position 01 at maximum reduction. 01 is the original position at the same magnification.

If a plurality of light source units C are arranged at a distance of P from the lens principal point 10 on the same plane, the emission aperture angle of the light source unit C shown in FIG. The highest light source utilization rate and heavy illumination rate are obtained when the light source utilization rate and heavy illumination rate are varied as Cl, C2, and C3 in relation to the vertical movement of the document table relative to the lens table in response to the change in magnification at time 01. The deflection of this opening angle is the optical axis CmO of the light source unit.
, C, O, and CiO. Now let this deflection angle be θ, and the light source optical axes CiO and CmO, the light source P, and the lens 1. θ is the angle formed by the straight line connecting the . and θ1, and the imaging formula SVClO-01 and 1.

-0m is applicable, so the above equation (3) is further transformed into the above (1)
By having the ceremony performed on your behalf, it becomes.

By presetting the light source optical axis at maximum expansion or maximum reduction, Mi or M is determined, so if we preset it to 0m at maximum expansion, the above equation (4) becomes, and the light source changes according to the magnification M. The rotation angle θ is determined.

In this way, since the magnification M is determined by the amount of vertical change of the original with respect to the lens, the rotation angle θ is synchronized with the vertical movement of the original surface, and the light source optical axis is always directed to the center of the original. Also, by adding the angle α to θ, the light field can be made to match the original. In order to match the light fields, it is sufficient to set the optical axis slightly lower than the center of the document surface when presetting the light source. The above principle can be implemented by the following mechanism. That is, two points are variable, in other words, one of the document table a and the lens table 1, and in the case of the mechanism of the present invention (FIG. 3), one end of a flexible belt or string is fixed to the document table a. The other end is attached to one other point, in the case of the mechanism of the present invention, the winding drum 3 which is rotatably supported on the lens table and fixed to the shaft 2 which is given rotational force by a torsion spring 4. The shaft 2 is further provided with a bevel gear 5, which meshes with a bevel gear 7 provided at the tip of a shaft 6 associated with the light source unit C. The spring 4 has one end 8 connected to the shaft 2 and the other end 9
is fixed to the drum holder. Therefore, the variation b in the distance between the document table a and the lens 1 due to the variable magnification is detected by the expansion and contraction of the belt 1, that is, the amount of winding or unwinding on the drum 3, and at the same time the shaft 2 is rotated together with the drum 3.

The rotation of the shaft 2 is transmitted to and drives the light source unit by gear ration. Since the amount of variation b is proportional to the rotation angle θ, re-gearing may be performed using an appropriate drive ratio. Since the mechanism of this invention is a mechanism that automatically detects the interval between two variable points and makes one drive, the field of application is not limited to projectors, but can be applied to a wide variety of fields. As described above, according to the present invention, the light source optical axis is automatically deflected at each magnification, and is always positioned at the center of the document surface, making it possible to obtain the highest light source utilization rate and double illumination rate, and making it possible to perform transparent copying using Ghent paper. Also, the depth of focus can be increased by making it possible to narrow down the aperture.

Furthermore, the sharpness is improved, allowing precision copying and copying, and it is also possible to increase the distance between the light source and the document surface, making it possible to handle large documents and speeding up the copying time.

[Brief explanation of drawings]

FIG. 1 shows the locus of the positional relationship of the transmissive plate, lens, and document at each magnification.

Claims (1)

[Scope of Claims] 1. In a projector or the like having a document table and a lens table whose interval distance is variable with respect to the projection plane of the document image, a light source unit rotatably fixed to the lens table is provided with
an(1+1/M)F/P-tan(1+1/Mm)F
/P formula, θ=rotation angle M of light source unit=transmission magnification Mm=maximum magnification F=focal length of lens P=rotates with a rotation angle defined by the formula of distance between lens and light source center An optical device such as a transilluminator having a magnification synchronized light source.