JPH04119070A - Picture input device - Google Patents

Abstract

PURPOSE:To shorten optical path length by providing a photoelectric converting means to convert light transmitted through an optical system into a picture signal, a compensation signal generating means to generate a compensation signal to compensate the characteristic of the optical system, and a correcting means to correct the picture signal according to the compensation signal. CONSTITUTION:An optical system compensation signal generator 16 generates the compensation signal (e) to compensate the attenuation of peripheral light quantity caused by the edge effect of an imaging lens 10. Namely, since the light quantity of a peripheral part is less than the light quantity of a central part, the level of an analog picture signal from a CCD 11 in the case of full- white input falls at the peripheral part as shown by a full line. In order to compensate this fall of the level of the peripheral part, the signal (e) in which the peripheral part is set larger than '1' assuming that the central part is '1' is used. This signal (e) is supplied to a multiplier 13, and raises the level of the peripheral signal level of the analog picture signal (b) from the CCD 11. Thus, the analog picture signal (f) flat extending over the full width of the CCD 11 for the full-white input can be obtained from the multiplier 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image input device that inputs multivalued grayscale images.

[Prior Art] In a conventional image input device such as an image scanner, an imaging lens system is disposed in front of the image sensor in order to form an image of an object on the imaging surface of the one-dimensional image sensor. When the imaging area of such an image input device becomes wider, the amount of peripheral light of the imaging optical lens system is attenuated. In order to compensate for this attenuation, the optical distance of the imaging system is made long so that the angle of view is sufficiently smaller than that of the imaging lens.

Decreasing the angle of view reduces the amount of light. In order to compensate for this decrease in the amount of light, extremely bright lighting had to be provided.

[Problem to be solved by the invention] In this way, the image input device has a wide imaging area.

Because the optical distance is long, the device becomes very large.

Furthermore, very bright illumination is required to compensate for the attenuation of the amount of light due to the reduction in the angle of view, and power consumption also increases.

Therefore, two objects of the present invention are to provide an image input device that can be made smaller in size as a whole.

Another object of the invention is to provide an image input device that can be used with small lighting installations.

[Means for Solving the Problems] An image input device of the present invention includes an optical system for forming an image of an object to be imaged, a photoelectric conversion means for converting light passing through the optical system into an image signal, and a photoelectric conversion unit for converting light passing through the optical system into an image signal. The image forming apparatus includes a compensation signal generating means for generating a compensation signal for compensating the characteristic, and a correction means for correcting the image signal according to the compensation signal.

[Embodiment] Next, an embodiment of the present invention will be described with reference to the drawings.

Referring to FIG. 1, in one embodiment of the present invention, light from an object to be imaged passes through an imaging lens system 10 and enters a -dimensional charge transfer device (hereinafter referred to as CCD) 11.

Analog image signal a from CCD 1.1 is sent to amplifier 1
2 and is amplified.

The analog image signal from the amplifier 12 is supplied to an analog-to-digital converter (hereinafter referred to as an A/D converter) 4 via a multiplier 13 and converted into a digital image signal C. A synchronizing signal d is supplied from a synchronizing signal generator 15 to the CCDI 1 and the A/D converter 14, and the CCD 11 and the A/D converter 14 operate in synchronization with this synchronizing signal d.

Additionally, one embodiment includes one optical system compensation signal generator roller. The optical system compensation signal generator 16 generates a compensation signal e that compensates for the attenuation of the amount of peripheral light caused by the peripheral effect of the imaging lens 10. In other words, the amount of light at the periphery is smaller than the amount at the center, so the analog image signal level from the CCD II is lower at the periphery compared to the all-white input, as shown by the solid line in Figure 2. becomes. In order to compensate for this decrease in the peripheral region Luher, the central region is set to 1 and the peripheral region is set to be larger than 1 (ie.

A compensation signal e (having a characteristic shown by a broken line in FIG. 2 and opposite to the solid line in FIG. 2) is used. This compensation signal e is 1 multiplier 1
3 to raise the level of the peripheral signal portion of the analog image signal from the CCD II. This results in 2
From the multiplier 13, a flat analog image signal f is obtained for the full width of CCDI 1 for a completely white input.

The analog image signal f thus obtained is:

The A/D converter 14 converts it into a digital image signal C and outputs it.

As shown in FIG. 3, the optical system compensation signal generator 16 is synchronized with a read-only memory (hereinafter referred to as ROM) 17 in which a digital compensation signal having the characteristics shown by the broken line in FIG. 2 is stored, and a synchronization signal d. and a digital-to-analog converter 18 for converting the digital compensation signal read out into an analog compensation signal e. The analog compensation signal e is supplied to a 1 multiplier 13.

In the embodiment described above, the optical system compensation signal is stored in the ROM as a digital signal 12, but an analog signal having characteristics as shown by the broken line in FIG. 2 may be generated in response to the synchronization signal. .

Although a -dimensional CCD is used, it can also be applied to a case where a two-dimensional CCD is used, such as in a television camera.

[Effects of the Invention] As explained above, the present invention electrically compensates for the influence of the peripheral light attenuation of the lens system on the image signal, so that the lens system can have a wide angle of view. The distance can be shortened and the device can be made smaller.

Additionally, since the lens system can have a wide angle of view, there is no need to make the lighting any brighter than necessary, and power consumption can be reduced.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a characteristic diagram showing the characteristics of the optical system and a compensation signal for compensating for the characteristics,
FIG. 3 is a detailed block diagram of the optical system compensation signal generator 16 in the embodiment shown in FIG. 10... Optical system, 11... CCD, 12... Amplifier 13... Multiplier, 14... A/D converter 215...
・Synchronization signal generator, 16... optical system compensation signal generator,
17...ROM, 18...D/A converter. Diagram 2 Diagram y Specific force Diagram 3

Claims (1)

[Claims] 1. An optical system that forms an image of an object to be imaged, a photoelectric conversion means that converts light passing through the optical system into an image signal, and a compensation signal that compensates for the characteristics of the optical system. An image input device comprising: a compensation signal generating means; and a correction means for correcting the image signal according to the compensation signal. 2. The compensation signal generating means includes a memory storing a digital compensation signal for compensating the characteristics of the optical system, and means for converting the digital compensation signal from the memory into an analog compensation signal. Image input device. 3. The image input device according to claim 1, wherein the characteristic of the optical system is such that the amount of light at the peripheral portion is lower than the amount of light at the center.