JPH0356505B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a light intensity detection device for an illumination light source, and particularly in a device that uses a solid-state image sensor to image a subject, detects the light intensity of an illumination light source and uses it as a reference. The present invention relates to a circuit configuration that displays or issues an alarm if the amount is less than .

[Conventional technology]

A conventional light amount detection device for this type of illumination light source is provided with a photo sensor for detecting the amount of light, and the amount of light is detected based on the output of this photosensor.

[Problem that the invention seeks to solve]

Conventional light amount detection devices must be provided with a photosensor in addition to a solid-state image sensor, and therefore have had the problem of not being able to fully meet the demand for miniaturization of the device.

[Means for solving problems]

In order to solve the above problems, the light amount detection device for an illumination light source according to the present invention utilizes the output of a solid-state image sensor for light amount detection, and has the following configuration.

That is, in the present invention, there is provided a comparison circuit that compares the output from the solid-state image sensor with a predetermined reference value; a second AND gate circuit that passes the output of the other end of the field of view of the solid-state image sensor among the outputs of the comparison circuit;
The output of the AND gate circuit and the horizontal synchronizing signal of the solid-state image sensor are input, and a first pulse is selected that rises at or near the output of the first AND gate circuit and falls at or near the horizontal synchronizing signal. a flip-flop circuit; at least the output of the second AND gate circuit and the horizontal synchronizing signal of the solid-state image sensor are input, the output rises at or near the output of the second AND gate circuit, and the horizontal synchronizing signal rises at or near the output of the second AND gate circuit; a second flip-flop circuit that selects a pulse that falls at A third flip-flop circuit receives the horizontal synchronizing signal of the image pickup device as a clock signal, and outputs the output of the AND circuit in synchronization with the horizontal synchronizing signal.

[Effect]

The output of the solid-state image sensor is compared with a predetermined reference value in a comparison circuit, and a portion exceeding the reference value is sent out as a pulse output from the comparison circuit. The first AND gate circuit and the second AND gate circuit send the outputs of the comparison circuit on both sides of the field of view of the solid-state image sensor to the first flip-flop circuit and the second flip-flop circuit, respectively. 1st
When there is an output from the first AND gate circuit, the flip-flop circuit outputs a pulse that rises at or near the output and falls at or near the horizontal periodic signal of the solid-state image sensor. When there is an output from the second AND gate circuit, the second flip-flop circuit outputs a pulse that rises at or near the output and falls at or near the horizontal synchronization signal of the solid-state image sensor. The AND circuit is the first
The logical product of the output of the first flip-flop circuit and the output of the second flip-flop circuit is calculated. The third flip-flop circuit selects an output based on the output of the AND circuit.

That is, it is checked whether both sides of the field of view of the solid-state image pickup device are above a predetermined reference value, and if they are above a predetermined reference value,
An output appears on the third flip-flop circuit.
If either one or both ends are below a predetermined reference value, no output will appear in the third flip-flop circuit.

In this way, it is detected whether the amount of light from the illumination light source is greater than or equal to the reference value.

〔Example〕

Next, embodiments of the present invention will be described based on the drawings. FIG. 1 is a block diagram of a light amount detection device for an illumination light source according to the present invention, and FIG. 2 is a time chart showing its operation.

In Figure 1, 1 is the illumination light source, 2 is the whiteboard at the reading position, 3 is the lens, and 4 is the CCD.
It is. 5 is an amplifier, the output of which is sent to the binarization circuit 2
0 and comparator 6. Binarization circuit 2
At 0, the video signal is binarized using an appropriate threshold level, and the signal is processed as an image sensor. A comparator 6 compares the output of the amplifier 5 with a setting value of a setting device 7 consisting of a variable resistor. 8 and 9 are AND gate circuits, and the output of the comparator 6 and the gate pulse A are applied to the AND gate circuit 8. Gate pulse A
is a pulse whose timing corresponds to one end of the field of view of the CCD 4, and the AND gate circuit 8 sends out the output of the comparator 6 when this gate pulse A is input. AND gate circuit 9
is supplied with the output of the comparator 6 and the gate pulse B. The gate pulse B is a pulse whose timing corresponds to the other end of the field of view of the CCD 4, and the AND gate circuit 9 uses this gate pulse B.
Sends out the output of comparator 6 when input is input. 10 and 11 are flip-flop circuits, respectively. The J terminal of the flip-flop circuit 10 is supplied with the output of the AND gate circuit 8, and the K terminal is supplied with the horizontal synchronizing signal ψ _T of the CCD 4. The output of the AND gate circuit 9 is applied to the J terminal of the flip-flop circuit 11, and the horizontal synchronizing signal ψ _T is applied to the K terminal as in the above case. And which flip-flop circuits 10, 11
A clock pulse CK is also applied to the clock terminal CK of.

12 is an AND circuit, and flip-flop circuit 1
Find the logical AND of the outputs of 0 and 11. 13 is a D-type flip-flop circuit, and the AND circuit 12 is connected to the D terminal.
The horizontal synchronizing signal ψ _T is applied to the clock terminal CK.

The operation of the apparatus of this embodiment having the above configuration will be explained with reference to the time chart of FIG.

The light from the illumination light 1 is reflected by the whiteboard 2 and enters the CCD 4 via the lens 3.

The CCD 4 sequentially scans at a constant cycle using a horizontal synchronizing signal ψ _T (Fig. 2 a), and outputs an output according to the amount of light (Fig. 2 b). This output is amplified by an amplifier 5, and then compared with a setting value of a setting device 7 by a comparator 6, and an output as shown in FIG. 2c, for example, is obtained. The output of the comparator 6 is given to AND gate circuits 8 and 9, and gate pulses A,
Since B are the timings shown in FIG. 2d and e, respectively, the output of the flip-flop circuit 10 is as shown in FIG. 2f. That is, at the timing when gate pulse A is applied, the amount of light is greater than the reference value. On the other hand, the flip-flop circuit 11 receives the first gate pulse B in the figure.
At the timing when B is given, the light intensity is below the reference value, so no output appears, but at the timing when the second gate pulse B is given, the light intensity is above the reference value, so the output appears. .

In AND circuit 12, flip-flop circuit 1
Since the product of the outputs of 0 and 11 is calculated and inputted to the D terminal of the D-type flip-flop circuit 13, the output of the D-type flip-flop circuit 13 becomes as shown in FIG. 2h. That is, an output that rises at timing _t0 is obtained, thereby confirming that the illumination light source is equal to or higher than the reference value.

Although a fluorescent lamp is often used as the illumination light source 1, it is known that the brightness rise characteristic of this fluorescent lamp when it is turned on depends on the temperature of the tube wall. If the temperature is not uniform, as shown in FIGS. 3a and 3b, the temperature rises unevenly during lighting and then stabilizes. Therefore, in the above-described embodiment, since the amount of light is initially less than the reference value, the device enters, for example, a ready state, but this state is canceled at timing _t0 .

Furthermore, if no output is obtained from the D-type flip-flop 13 even after a certain period of time has elapsed, a message indicating that the illumination light source is defective may be displayed to prompt the user to replace the fluorescent lamp.

〔Effect of the invention〕

As explained above, according to the present invention, when detecting the light amount of the illumination light source, the output of the solid-state image sensor is used and only both ends of the field of view are checked, so that the light amount detection device has a simple configuration. has been realized.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a light amount detection device for an illumination light source according to an embodiment of the present invention, Fig. 2 a to h are time charts showing its operation, and Fig. 3 a and b show the rise characteristics of a fluorescent lamp. FIG. 1...Lighting light source, 2...Whiteboard, 3...
...Lens, 4...CCD, 5...Amplifier, 6...
Comparator, 7...Setter, 8, 9...AND gate circuit, 10, 11...Flip-flop circuit, 12...AND circuit, 13...D-type flip-flop circuit.

Claims (1)

[Claims] 1 a comparison circuit that compares the output from the solid-state image sensor with a predetermined reference value; a first AND gate circuit that passes the output of one end of the field of view of the solid-state image sensor among the outputs of the comparison circuit; a second AND gate circuit that passes the output of the other end of the field of view of the solid-state image sensor among the outputs of the comparison circuit; and at least the output of the first AND gate circuit and the horizontal synchronization signal of the solid-state image sensor a first flip-flop circuit which sends out a pulse into which a signal is input, which rises at or near the output of the first AND gate circuit, and falls at or near the horizontal synchronization signal;
At least the output of the second AND gate circuit and the horizontal synchronization signal of the solid-state image sensor are input, and a pulse that rises at or near the output of the second AND gate circuit and falls at or near the horizontal synchronization signal is generated. a second flip-flop circuit for sending out; an AND circuit for calculating the logical product of the output of the first flip-flop circuit and the output of the second flip-flop circuit; the output of the AND circuit is input;
A third flip-flop circuit receives a horizontal synchronization signal of a solid-state image sensor as a clock signal, and outputs an output of an AND circuit in synchronization with the horizontal synchronization signal. Device.