JPH02108361A - Picture reader - Google Patents

Abstract

PURPOSE:To control the light source lighting-up timing and to shorten a picture reading time by irradiating an original by the intermittent illumination, and when picture information is read from an image sensor with the different picture element light accumulating timing, irradiating the original from the light accumulating starting time of a final picture element up to the light accumulating completion time of a peak picture element. CONSTITUTION:A shift pulse and a transfer pulse generated by a pulse generating circuit 6 of a picture reader are transferred to a contact type image sensor 1, and a picture element signal detecting circuit 7 detects the picture element output signal from the sensor 1, and the peak picture element signal and the final picture element signal from the shift pulse and the transfer pulse from the circuit 6 and communicates to a CPU 8. A light source driving circuit 9 lights up a light source 3 by the final picture element signal from the CPU 8 and the light source 3 is switched off by a peak picture element signal. The original is irradiated from the light accumulating starting time of the final picture element in the image sensor up to the light accumulating completion time of the peak picture element.

Description

[Detailed description of the invention] Ru.

FIG. 1 is a timing chart showing light source lighting timing according to an embodiment of the present invention. As shown in this figure, whereas conventionally the light source was turned on from the start time of the first pixel light accumulation timing to the end time of the last pixel light accumulation timing, in this embodiment, the illuminance required by the image sensor is
The light is applied between the light accumulation start time of the last pixel and the light accumulation end time of the first pixel (the lighting time of the light source of the present invention shown in FIG. 1), which overlaps with every pixel light accumulation time. As a result, the same amount of light is irradiated at every pixel light accumulation time, eliminating variations in light accumulation in each pixel.
Pixel signals can be extracted by shortening the light source lighting time. Therefore, the reading time for one line of pixel data in Kinomu h & Example Rainbow is the pixel output time during the light source lighting time.

FIG. 2 shows the overall configuration for realizing an image reading device according to the present invention. Here, 1 is a contact sensor, 2 is a gradient index rod lens, and 3 is a light source. The light source 3 illuminates the document surface, and the reflected light from the document surface is reflected by the rod lens 2.
passes through and forms an image on the contact sensor 1.

FIG. 3 shows a block configuration for realizing the timing shown in FIG. 1. In this figure, the pulse generation circuit 6
The shift pulse and transfer pulse generated by are transferred to the contact image sensor l. The pixel signal detection circuit 7 detects a first pixel signal and a last pixel signal from the pixel output signal from the contact image sensor 1 and the shift pulse and transfer pulse from the pulse generation circuit 6, and
tell. Further, the light source drive circuit 9 turns on the light source 3 according to the last pixel signal sent from the CPUA, and turns off the light source 3 according to the first pixel signal.

In this way, the light source lighting timing shown in FIG. 1 is realized. In other words, as long as the illuminance required for the image sensor to output accurate image data is obtained by the light source lighting time according to the present invention, the same effect can be obtained even if the light source lighting time is shortened or the light source is turned on only for a part of the light source lighting time. effect can be obtained. In this way, the light source lighting time can be shortened by
This shortens the time for reading one line image.

Further, the pixel signal output time shown in FIG. 1 is roughly divided into a dummy signal and an effective pixel signal, as shown in FIG. Utilizing this, a similar time reduction can be achieved even if the light source is turned on and optical data is accumulated within the dummy signal output time.

In addition, although the present embodiment described so far uses one light source, similar advantages can be obtained even when two or more light sources are switched and used.

[Effects of the Invention] As described above, in the present invention, the document is irradiated between the light accumulation start time of the last pixel and the light accumulation end time of the first pixel in the image sensor, so that the image reading time is shortened. be able to.

[Brief explanation of drawings]

FIG. 1 is a timing diagram showing the light source lighting timing according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a human-powered image device according to this embodiment, and FIG. 3 is a block diagram showing the electric circuit configuration of this embodiment. , Fig. 4 is a timing diagram showing effective pixel signal output, Fig. 5 is a schematic configuration diagram of a conventionally known image reading device, and Fig. 6 shows the operation of a CCO sensor using a conventional reduction optical system. FIG. DESCRIPTION OF SYMBOLS 1... Close-contact image sensor, 2... Gradient index rod lens, 3... Light source, 4... Green LED, 5... Red LED. 6...Pulse generation circuit, 7...Pixel signal detection circuit, 8...62 ports, 9...Light source drive circuit. Gen Oke side Figure 2 Figure 5

Claims (1)

[Claims] 1) In an image reading device that illuminates a document with intermittent illumination and obtains image information from image sensors with different pixel light accumulation timings, the document is scanned between the light accumulation start time of the last pixel and the light accumulation end time of the first pixel. An image reading device characterized by comprising means for irradiating.