JPS58214144A - Original density detector of variable power type copying machine - Google Patents

Abstract

PURPOSE:To detect the density of an original regardless of variable power, by providing an original density detector regardless of an optical system and prior to the exposure of original which is carried by a slit exposure optical system. CONSTITUTION:An original density detector 20 is set on a base 11, and a case 21 contains a lamp 17, a condenser lens 18, a photodetecting element 19, etc. The lamp 17 glows with a push of a copy start button. Then the density of an original is detected regardless of a slit exposure optical system and prior to the slit exposure carried by a slit exposure optical system. Therefore the result of density detection is fed back to the supply voltage, the development bias, etc. of a lamp 2 to control successively the density of copied pictures in case an optical system moves a distance dmm with a speed Smm/sec and reaches a copy start point 13 after d/S sec. Furthermore another driving system is not needed since the detetor 20 is set on a mobile stage, and an optical system lamp for variable power processing gives no effect to a detector lamp since the lamp 17 is provided independently.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a document density detection device for a variable magnification type copying machine.

In a variable magnification type copying machine, it is necessary to change the light amount of a light source for document illumination in response to a change in copying magnification.

Therefore, part of the optical image exposure light projected onto the photoreceptor moving in a predetermined direction is received by the reflected light from the original.

In a device that detects the original density based on the amount of received light, it is necessary to change the amount of light incident on the light-receiving element or change the sensitivity of the light-receiving element each time the magnification is changed, and the structure is complicated.

The present invention has been proposed in view of the above, and includes a document density detection device 6 that is capable of detecting document density regardless of magnification change. The purpose is to provide

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows an overview of the slit exposure optical system of a moving optical system variable magnification type copying machine. 1 is a platen glass as a mounting table for the original O, 2 is a light source for illuminating the original 4A O, and 6 is this light source. 4 to 9 reflect the light from the original 0 to the original 0.
' A slit exposure optical system that projects and forms an image of the incident light onto a drum-shaped photoreceptor (hereinafter referred to as photoreceptor) 10 rotating in the direction of the arrow.

4 to 7 are mirrors, 8 is a variable magnification lens, and 9 is a slit plate.

The base 11 to which the light source 29, reflection plate 6 and mirror 4 are attached is moved from the position shown in FIG. 2 in the direction of the arrow at a speed V using a drive mechanism button (not shown) along a guide rail (not shown). Therefore, the document exposure section 12 is run up just before the tψ copy opening start point 13. Also, is the mounting base 14 of the mirror 5 mentioned above and the mounting base 15 of the mirror B connected to the connecting member 16? It is moved from the position shown in FIG. 2 in the direction of the arrow at a speed of 1/2v along a guide rail (not shown) by a drive mechanism (not shown).

The present invention is provided with an original density detector for detecting the original density independently of the slit exposure optical system prior to slit exposure of the original using the slit exposure optical system.
The illustrated example has a configuration in which a document density detector 20 is provided on the base 11 as shown in FIG. This organ concentration detector 2
0 is a lamp 17 provided inside the case 21. Focusing lens 1
8. It consists of a light receiving element 19 and the like.

Since the present invention has the above configuration, the following effects can be obtained.

(1) When a copy start button (not shown) is pressed, the lamp 17 lights up and the slit exposure optical system changes the distance tl11t d xm at the speed SM/
66c and reaches the copying start point 13 after d/5sea, the detection result of the document density is fed back to the supply voltage or developing bias of the lamp 2 of the slit exposure optical system, and then -8 images are sequentially produced. The concentration can be adjusted.

(2) Lamp 17 for detecting document density. Light receiving element 19
Since the slit w is attached to the movable base of the optical system,
There is no need to provide a separate drive system for document density detection.

(3) Since the distance from the start position of the slit exposure optical system to the copying start point can be determined relatively freely, it is easy to feed back the detection result of the original density to the rung voltage or developing bias. .

(4) Since the lamp for document density detection is made separate and independent from the lamp for the slit exposure optical system, changing the lamp light intensity of the slit exposure optical system in response to magnification processing has no relation to document density detection. .

Note that in the above example, the document 43 degree detector 20 is attached to the first mirror mounting base 11 of the slit exposure optical system.
! As shown by the chain line in Figure 42, the second mirror 5. The tip of the mounting base 16 of the first mirror 4 is slit a.
The document density detector 20 is extended in the direction in which the light travels and protrudes ahead of the first mirror 4, and the document density detector 20 is attached to this protrusion so as not to be the edge of the reflected light from the sixth mirror 6. The first mirror 4 moves at a speed of V/2 and the second mirror 5 moves at a speed of V/2. It is also possible to detect the density of the original until the sixth mirror 6 overtakes the original density detector 20 on the mount 16, and feed back the detection result to the lamp supply voltage, developing bias, etc.

Document density detection uses a lens and a detector (for example, C
0D) to detect fine document densities, or detect a wide range of densities without using a lens). In FIG. 2, reference numeral 22 is a white plate for density detection reference provided on the lower side of the platen glass 1, and also serves as a white plate for whitening the leading edge of the copy.

The apparatus of the present invention includes, in addition to the optical system movable variable magnification type copying machine shown in the figure,
The present invention can be similarly applied to a multi-magnification type copying machine in which the optical system is fixed and the table on which the original is placed is moved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a slit exposure optical system of a moving optical system type variable magnification type copying machine, and FIG. 2 is a front view showing an embodiment of the original density detecting apparatus of the present invention. 0 is the original, 1 is the original table, 2 is the light source for slit exposure,
3 is a reflector plate, 4 to 7 is a variable magnification lens, 9 is a slit plate, 10 is a photoreceptor, 11 is a mirror mounting base, 12 is an original exposure section, 16 is a copying start point, 14.15 is a mirror A mounting base, 16 a connecting member, 17 a lamp for detecting document density,
18 is a condensing lens, 19 is a light receiving element, . . . 20 is an original density detector 0

Claims (1)

[Claims] (1) A document loading table on which a document is placed; a slit exposure optical system that illuminates the document 1 and forms a reflected light image on a photoreceptor that moves in a predetermined direction through a variable magnification lens; , a driving means for relatively moving the document mounting table and the slit exposure optical system in synchronization with the movement of the photoreceptor, and a light source for illuminating the document that is separate from the slit exposure optical system, and the slit exposure optical system A document density detection device for a variable magnification copying machine, comprising a document density detector that detects document density prior to slit exposure by a system.