JPH0147945B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a light amount detection signal processing circuit in a solid-state scanning device such as a facsimile or a copying machine that reads document information using a solid-state scanning device such as a CCD or PDA.

Conventionally, in such a solid state scanning device, the output of the light amount sensor is detected by an error amplifier as a change in the amount of light to stabilize the solid state scanning element, and the output of the light amount sensor is displayed as an error when the amount of light is 0. That's what I do. As described above, since the conventional device displays an error when the amount of light becomes 0, it has the disadvantage that it is not possible to check the amount of light until an error occurs. Therefore, an object of the present invention is to provide a light amount detection signal processing circuit which eliminates such drawbacks, and which detects changes in light amount with one light amount sensor, stabilizes the output level of the solid-state scanning element, and reduces the amount of light. A warning is displayed when the output level of the solid-state scanning element is stabilized by an amount between the lower limit and the upper limit, and the function of the device is stopped when the output level reaches a level where it is impossible to stabilize the output level.

This invention will be explained below.

First, an example of a solid-state scanning device to which the present invention is applied will be described with reference to FIG. It is reflected by the mirror 4 and the lens system 5 and becomes a solid-state scanning element.
Input to CCD6 and photoelectrically converted, image signal PS
It is now output as . In this way, solid-state scanning devices use fluorescent lamps for document illumination due to their low power consumption and long lifespan, but the light intensity characteristics of fluorescent lamps with respect to environmental temperature change as shown in Figure 2. The light intensity decreases as shown in Figure 3. Therefore, if the output of the CCD 6 is directly output as the image signal PS, the image signal PS will change correspondingly due to the fluctuation in the amount of light, making it inappropriate as an image information signal.

The present invention normalizes and outputs the image signal PS, and also makes it possible to issue a warning and stop the function.As shown in FIG. An error amplifier 11 that outputs the difference between the detection signal DT from the light amount sensor 10 and the reference value V _r1 , and voltage control that normalizes the image signal PS input via the amplifier 12 using the error signal ER of the error amplifier 11. An amplifier 13, a comparator 14 which compares the error signal ER and the reference value V _r2 and outputs an alarm signal AR, and a comparator 14 which compares the error signal ER and the reference value V _r3 and outputs a function stop signal.
A comparator 15 that outputs FN is provided. Therefore, the light source is 2 as shown in Figure 5.
It is composed of two fluorescent lamps 3A and 3B,
A light amount sensor 10 is attached to the side wall of a light source box 20 that is placed so as to surround these fluorescent lamps 3A and 3B. Further, the alarm signal AR from the comparator 14 passes through the drive circuit 16 and is displayed as an alarm on the display device 17, and the reference values V _r1 to V _r3 are set to predetermined levels in advance. Furthermore, the display device 17 performs an alarm display (lighting of a lamp, etc.) when the alarm signal AR becomes, for example, "1", and stops the function of the solid-state scanning device when the function stop signal FN becomes, for example, "1". I'm starting to do that.

In such a configuration, the CCD 6 outputs an image signal PS at a level corresponding to the amount of light reflected from the document 1.
The output is as shown in FIG. 6.
In other words, the noise level is always constant, and as the amount of light decreases, the level of the output PS also decreases, so the SN ratio also decreases. However, even if the gain of the amplifier 12 is increased, the SN ratio does not change, and the required SN ratio is not reached. The one with the lower amount of light will decide. FIG. 7A shows the characteristic changes for large light amount (), medium light amount (), and small light amount (), and FIG. 7B shows the level of the image signal PS corresponding to these.

On the other hand, the light intensity of the fluorescent lamps 3A and 3B as light sources is detected by a light intensity sensor 10 provided in the vicinity thereof, and the detection signal DT thereof is input to an error amplifier 11. A preset constant reference value V _r1 is input to the error amplifier 11, and the difference therebetween is output as an error signal ER. Therefore, when the light intensity changes as shown in Figure 7A, the error signal ER
The error signal ER becomes as shown in FIG. Thus, the amplification factor of the voltage controlled amplifier 13 changes with respect to the control voltage ER as shown in FIG. 8, and as the control voltage increases, the amplification factor also increases. Therefore, the error signal ER
When the error signal ER is small, that is, when the amount of light is large, the amplification factor of the voltage-controlled amplifier 13 is small, and when the error signal ER becomes large, that is, when the amount of light is small, the amplification factor of the voltage-controlled amplifier 13 becomes large, thereby normalizing the image signal PS. and outputs it as an image information signal PSA.

Furthermore, the error signal ER is output from comparators 14 and 1.
5, but comparator 14 requires
A comparison is made with the reference value _Vr2 , which is set slightly smaller than the level corresponding to the light intensity determined by the SN ratio.
The comparator 15 performs a comparison with a reference value V _r3 set at a level corresponding to the amount of light for the required SN ratio. Therefore, comparators 14 and 15 are
When the error signal ER exceeds the respective reference values V _r2 and V _r3 , a binary signal of "1" is output. Therefore, the error signal ER and the reference value
When V _r2 and V _r3 have a relationship as shown in FIG. 7C, the output AR of the comparator 14 becomes as shown in FIG. 7D, and the output FN of the comparator 15 becomes as shown in FIG. 7E. In other words, when the light intensity is sufficient and the error signal ER is smaller than the reference values V _r2 and V _r3 (characteristics), the alarm signal AR and the function stop signal FN are "0".
and does not display alarms or stop functions. Also, when the light intensity is insufficient and the error signal ER exceeds the reference value V _r2 (characteristics), the alarm signal AR becomes "1" and an alarm is displayed, and the light intensity is small and the error signal ER exceeds the reference value. When V _r3 or higher (characteristic), the function stop signal FN is set to “1” and the function stops.

Thus, this signal processing circuit can normalize the image signal in accordance with changes in the amount of light, and also displays an alarm and stops the function when the amount of light falls below a predetermined value.

As described above, according to the light amount detection signal processing circuit of the present invention, image signals can be normalized according to changes in light amount, and when the light amount has decreased due to aging etc., it can be normalized according to the degree. , normalizes the error signal without displaying an alarm or stopping the function when it is within a small range,
In addition, when the error signal is within a medium range, an alarm is displayed and the error signal is normalized, and when the error signal is within a large range, the function is stopped. Appropriate measures can be taken to increase the reliability of fixed scanning devices.

In the above embodiment, the light amount sensor is attached to the side wall of the light source box to detect changes in the amount of light, but it can be attached arbitrarily near the light source.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a solid-state scanning device to which the present invention can be applied, FIGS. 2 and 3 are environmental temperature characteristics and aging charts of a fluorescent lamp used in the solid-state scanning device, and FIG. 4 5 is a block diagram showing an embodiment of the present invention, FIG. 5 is a diagram showing the structure of the irradiation section according to the invention, FIG. 6 is a diagram showing the characteristics of the CCD with respect to the light amount, and FIGS. 7 A to E are diagrams showing the characteristics of the light amount. (),
A diagram showing the characteristics of each part for medium () and small (),
FIG. 8 is a diagram showing the characteristics of the voltage controlled amplifier. 1... Original, 2A, 2B... Conveyance roller, 3, 3
A, 3B...Fluorescent lamp, 4...Mirror, 5...Lens system,
6...CCD, 10...light amount sensor, 11...error amplifier, 12...amplifier, 13...voltage control amplifier, 1
4, 15...Comparator, 16...Drive circuit, 17
...Display device.

Claims (1)

[Claims] 1. A device that photoelectrically converts light irradiated onto a document from a light source using a solid-state scanning element and outputs an image signal, including a light amount sensor that detects the amount of light from the light source, a detection signal from the light amount sensor, and a first reference value. a voltage control amplifier that normalizes the image signal using the error signal of the error amplifier; and a first voltage control amplifier that compares the error signal and a second reference value and outputs an alarm signal. and a second comparator that compares the error signal and a third reference value larger than the second reference value and outputs a function stop signal. signal processing circuit.