JPH01320857A - Color image scanner - Google Patents

Abstract

PURPOSE:To reduce the number of filters on the detection side and photodetectors by outputting continuous light from a luminance signal light emitting element and outputting interrupted light from plural color signal light emitting elements and detecting color signals in time division by a common color signal detecting element. CONSTITUTION:Light from a laser diode 21 and light from three LEDs 22, 23, and 24 are synthesized and are supplied to a scanning mirror 18 through a focus lens 20, and synthesized light is scanned in the peripheral direction of a drum 10. Simultaneously, the drum 10 is fed in the direction of the axial line with respect to an optical system to perform subscanning. The surface of an original 11 is irradiated with light through a transparent cylinder 10, and the reflected light is taken into a light transmitter 12 and is emitted from an exit surface 14. A luminance signal component of the emitted light is transmitted through a dichroic prism 30 and is detected by a photodetector 28, and color signal light is detected by a photodetector 29. An LED 21 for luminance signal always emits light, and LEDs 22, 23, and 24 for color signals emit light in order, and three kinds of light are detected by the photodetector 29.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a color image scanner, and more particularly to an image scanner that reads out luminance signals and color signals separately.

rSummary of the invention] A document is wrapped around the outer peripheral surface of a transparent cylinder, and a scanning mirror irradiates the document with light while scanning it in the radial direction.The reflected light is received by a light guide, and this light is detected by a photodetector. In a cylindrical color image scanner, the light emitting element for the luminance signal emits light continuously, but the three color signals are supplied in a time-division manner, and the reflected light is synchronously detected. , the optical system is simplified and power consumption is reduced.

K. Prior Art The applicant of the present application has proposed a cylindrical image scanner that scans light in the radial direction of the cylinder while rotating a mirror at the center. In order to colorize such an image scanner, as shown in FIG. 5, an LDl for luminance signals and three LEDs 2 for color signals are provided, and these are synthesized by three dichroic prisms 3. At the same time, by supplying the light to the scanning mirror 5 through the focus lens 4 and rotating the mirror 5 around its axis, it is possible to irradiate the surface of the document wrapped around the outer peripheral surface of the transparent cylinder 6 with light. Become.

The reflected light from the document wrapped around the cylinder 6 is collected by a transparent light guide 7, and the detection light emitted from the output part is separated by three dichroic prisms 8 and transmitted to four photodetectors 9. Thus, a luminance signal and three color signals are extracted.

[Problems to be Solved by the Invention K] In the cylindrical image scanner of the type in which the mirror 5 is rotated at the center of the drum 6, high resolution can be achieved by separately detecting the luminance signal and the color signal as described above. It becomes possible to realize a high-resolution color image scanner. However, according to this method, in order to detect color signals, the three-color LEDs 2 of red, green, and blue are always emitted, and the reflected light is separated into three colors by the color filter 8, and then their intensities are measured. will be detected by three photodetectors 9. Therefore, if such a system is adopted, there is a drawback that the number of parts of the optical system becomes extremely large.

The present invention has been made in view of these problems, and it is an object of the present invention to provide a color image scanner in which the number of parts of the optical system on the detection side is reduced.

Means for Solving Problem K] The present invention provides: a luminance signal detection element; a color signal detection element; a luminance signal light emitting element corresponding to the luminance signal detection element; and a plurality of luminance signal detection elements corresponding to the color signal detection element. a color signal light emitting element, the luminance signal light emitting element outputs continuous light, the plurality of color signal light emitting elements output intermittent light, and the color signals are time-divided by the common color signal detection element. This is a multiplex method for detection.

K Effect] Therefore, it becomes possible to sequentially detect light from a plurality of color signal detection elements using a common color signal detection element in a time-division multiplexing manner, and in particular, it becomes possible to reduce the number of color signal detection elements.

K Embodiment FIGS. 1 and 2 show a color image scanner according to an embodiment of the present invention, and this color image scanner has a transparent cylinder 1 made of glass or synthetic resin.
0. A document 11 is wound around the outer peripheral surface of the cylinder 10. Note that the original 11 is on the drum 10.
The effective winding in the circumferential direction of
It is designed so that it can be wound so that it is .

A light guide 12 is arranged inside the transparent cylinder 10.

The light guide 12 is made of transparent resin or glass, and has a substantially trumpet-like shape with a cut-out lower part, and an arcuate entrance portion 13 is formed on the outer circumferential side of the light guide 12 . The entrance portion 13 has a curved cross section as shown in FIG. 1, and serves as a lens for receiving reflected light from the original 11.

Furthermore, the entrance portion 13 extends in the circumferential direction of the drum 10, so that the effective winding of the original 11 has an angle corresponding to the portion. On the other hand, the center side of the light guide 12 constitutes an output section 14, from which the light traveling through total internal reflection is output. Further, the side end face of the light guide 12 is configured as a reflective surface 15, which prevents light from leaking to the outside from this side end face.

A motor 16 is disposed at the center of the light guide 12, and a scanning mirror 18 is attached to its output shaft 17. Note that the scanning mirror 18 is fixed to the output shaft 17 at an angle of 45 degrees.

A focus lens 20 is disposed in front of the scanning mirror 18, and a focus lens 20 is arranged in front of the scanning mirror 18.
Three color signal LFDs 22, 23, and 24 are arranged. Note that the LED 22 generates a green color signal, the LED 23 generates a blue color signal, and the LED
D24 generates a red color signal J: Turning 1,
In order to combine the light from these three LEDs 22 to 24 and the light from the LD 21, three dichroic prisms 25, 26, and 27 are arranged as shown in FIG. On the other hand, there are two
Two photodetectors 28.29 are arranged, and a dichroic prism 30 is provided to separate the light supplied to these photodetectors 28.29.

In the above configuration, the light from the laser diode 21 and the light from the three L F D 22, 23, 24 are combined and supplied to the scanning mirror 18 through the focus lens 20. The scanning mirror 18 is rotationally driven by the motor 16, thereby scanning the combined light in the circumferential direction of the drum 10. This scan becomes the main scan. At the same time, the drum 10 is moved in the axial direction relative to the optical system, thereby performing sub-scanning. In this manner, the surface of the original 110 can be sequentially scanned. When light is irradiated onto the surface of the original 11 through the transparent cylinder 10, the reflected light is taken into the light guide 12 by the arc-shaped entrance portion 13 of the light guide 12. The reflected light then travels through the light guide 12 while being totally reflected, and is emitted from the output surface 14 .

The luminance signal component of the emitted light passes through the dichroic prism 30 and is detected by the photodetector 28. On the other hand, the color signal light reflected by the dichroic prism 30 is detected by two photodetectors.

The LD 21 for brightness signals emits light all the time. On the other hand, the color signal LEDs 22, 23, and 24 are sequentially emitted by pulse drive, as shown in FIG. And these three L E D 22.
The light from 23 and 24 is detected by a photodetector 29 by synchronous detection d1. This allows the single photodetector 29 to be commonly used as a photodetector for three color signals. It is also possible to use red visible light as D21 for luminance signals and use it also as an LED for color signals, and the optical system of the image scanner for this purpose is similar to that shown in Figure 1. Configuration is fine.

In order to make such an optical system possible, the reflection and transmission characteristics of the three dichroic prisms 25, 26, and 27 placed on the incident side of the scanning mirror 18 are as shown in FIG. By arranging the three dichroic prisms 25, 26, 27 as shown in FIG.
It becomes possible to coaxially superimpose the light from the As described above, such light is focused by the focus lens 20 and scans the surface of the original 11 by rotating the scanning mirror 18. Further, it is arranged on the output section 14 side of the light guide 12. The dichroic prism 30 may have the same reflection and transmission characteristics as the dichroic prism 25 on the incident side, and such a prism 30 transmits the luminance signal light to the photodetector 28 and the red, green, and blue lights to the photodetector 29. It will guide you.

[Effects of the Invention] As described above, the present invention outputs continuous light from a luminance signal light emitting element, while outputting intermittent light from a plurality of color signal light emitting elements to detect a common color signal. Detection is performed using a time division multiplexing method using elements. Therefore, according to such a structure, it is possible to reduce the number of filters and detection elements on the detection side, and since it is only necessary to cause the color signal light emitting element to emit light intermittently, the power consumption for this can be reduced. It becomes possible to reduce the

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the optical system of a color image scanner according to an embodiment of the present invention, Fig. 2 is an external perspective view showing the drum and light guide, and Fig. 3 shows the timing of light emission of the LD and LED. FIG. 4 is a graph of reflection/transmission characteristics of a dichroic prism, and FIG. 5 is a cross-sectional view of a conventional cylindrical color image scanner. The names of the main parts in the drawings are as follows. 10... Transparent cylinder 11... Original 12... Light guide 13... Arc-shaped entrance section 14... Output section 18... Scanning mirror 20...Focus lens

Claims (1)

[Claims] 1. A luminance signal detection element, a color signal detection element, a luminance signal light emitting element corresponding to the luminance signal detection element, and a plurality of color signal light emitting elements corresponding to the color signal detection element. The luminance signal light emitting element outputs continuous light, the plurality of color signal light emitting elements output intermittent light, and the color signal is detected by the common color signal detection element in a time division multiplexing manner. A color image scanner characterized by: