JP2001008097A - Electronic endoscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a picture with excellent lightness even at a remote distance or the like without deteriorating the S/N. SOLUTION: The electronic endoscope is provided with a diaphragm control circuit 14 that drives a diaphragm 11 on the basis of a luminance signal obtained by a CCD 15 to regulate an emitted luminous quantity, an AGC circuit 18 that applies variable gain control to a video signal, and a detail circuit 21 that conducts contour emphasis or the like. When a microcomputer 24 detects that the diaphragm 11 is fully open in a deficient state of the lightness of a picture, the microcomputer 24 controls the AGC circuit 18 to increase the gain of the signal and the detail circuit 21 to decrease a detail quantity in proportion to the increase in the gain.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic endoscope apparatus, and more particularly to an electronic endoscope apparatus which adjusts the brightness of an image obtained by an image pickup device by controlling a light amount aperture.

[0002]

2. Description of the Related Art In an electronic endoscope apparatus, a CCD (Charge Coupled D) which is a solid-state image pickup device based on light irradiation from a light source.
evice), an image of the inside of the object to be observed is captured, and the exposure amount at the time of this capturing is adjusted by aperture control (iris control) means. For example, the luminance information of the video signal obtained by the CCD is input, and the aperture control means adjusts the aperture opening so that the luminance information becomes constant. The image (screen) brightness is kept constant by increasing the amount and decreasing the aperture amount when the image is bright and decreasing the exposure amount.

[0003]

However, in the above-mentioned conventional light amount control by the aperture control means of the electronic endoscope,
When using a light source lamp with low light output,
In some cases, such as when the lamp is deteriorated, the exposure amount is insufficient for a distant subject or the like.

On the other hand, conventionally, when the exposure amount is insufficient, the gain of the video signal is increased, and the brightness is maintained at a predetermined value by signal amplification processing. In this case, however, the S / N ratio is increased. Is reduced.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an image with good brightness even at a long distance without lowering the S / N ratio. An electronic endoscope device is provided.

[0006]

In order to achieve the above object, an electronic endoscope apparatus according to the present invention is provided with an image pickup device for picking up an image of an inside of a body to be observed based on light irradiation from a light source and inputting exposure amount information. A light amount control circuit that variably controls a light output from the light source; a gain control circuit that variably controls a gain of an image signal (video signal) output from the image sensor; and performs contour enhancement on the image signal. When it is detected that the light output by the light amount control circuit is at an upper limit value in a state where the image brightness is insufficient by the detail circuit and the exposure amount information, the gain control circuit increases the gain of the image signal, And a control circuit for controlling the detail amount of the detail circuit so as to decrease in proportion to the increase of the value.

According to the above configuration, for example, a luminance signal is used as the exposure amount information, it is determined that the exposure amount is insufficient based on the luminance signal, and it is detected that the diaphragm is at the fully open (maximum light amount) position. In this case, the gain of the video signal is increased by an automatic gain control circuit or the like. At the same time, the detail amount is reduced according to the increase in the gain. The decrease in the amount of detail (contour enhancement effect) serves to suppress the appearance of noise caused by the increase in the signal gain. Therefore,
While preventing the S / N ratio from deteriorating, it is possible to obtain an image having a brightness that cannot be formed even when the aperture of the diaphragm is maximum.

[0008]

FIG. 1 shows the configuration of an electronic endoscope apparatus according to an embodiment. In this example, light from a lamp (halogen lamp or xenon lamp) 10 passes through an aperture 11. The light source 12 is supplied to the entrance end of the light guide 12, and the light guide 12 guides the light source light to the distal end portion of the electronic scope and irradiates the body under observation. The lighting of the lamp 10 is controlled by a lamp driving circuit 13, and the aperture of the aperture 11 is controlled by an aperture control circuit 14.

For example, the aperture 11 is configured to rotate a single blade or the like so as to block a lamp light beam. By controlling the rotation position of the aperture blade based on a luminance signal or the like described later, the minimum aperture amount can be reduced. It can be variably set from a position of (aperture value) to a position of full opening (maximum opening amount).

At the tip of the electronic scope, a CCD 15 which is a solid-state image pickup device is disposed via an objective optical system, and a video signal is read from the CCD 15 by a CCD drive circuit 16. On the other hand, the CCD 15 has a fixed gain circuit 17 for giving a constant gain to the video signal, and an automatic gain control (Automatic control) which operates when a predetermined image brightness cannot be obtained even when the aperture 11 is in the fully open position as described later.
Gain Control-AGC) circuit 18 is connected.
A digital signal processor (DSP) 20 is arranged in the C circuit 18 via an A / D converter 19.

The DSP 20 includes, for example, a circuit for forming, for example, a color difference signal and a luminance signal from a video signal and performing various processes such as gamma correction and white balance, and a detail circuit 21 for enhancing the contour. As is generally known, this detail circuit 21
The contour portion of the image is emphasized by making the signal level uneven by using an H (horizontal scanning period) delay circuit, an arithmetic circuit, or the like.

A microcomputer 24 is provided to control the above circuits and control the brightness of an image. The microcomputer 24 inputs a luminance signal (level) from the DSP 20 as exposure amount information. The aperture 1 is controlled via the aperture control circuit 14 so that the luminance signal level becomes constant.
1 is controlled. That is, when the luminance signal is larger than a predetermined value, the aperture of the diaphragm 11 is reduced, and when the luminance signal is smaller than the predetermined value, the aperture of the diaphragm 11 is increased. The microcomputer 24 causes the AGC circuit 18 to function when the luminance signal is smaller than a predetermined value and the aperture 11 is at the fully opened position. That is, the gain of signal amplification is increased so that the luminance signal becomes constant.

At this time, the microcomputer 24 simultaneously controls the detail circuit 21 so as to reduce the degree of edge enhancement. That is, the ratio corresponding to the increase ratio of the gain of the AGC circuit 18 is decreased. For example, when the gain is increased by 2 dB, the detail amount is decreased by 2 dB.

The embodiment has the above configuration, and its operation will be described below with reference to FIGS. FIG.
Shows the operation of the microcomputer 24. Based on the input of the luminance signal in step 101,
In step 2, it is determined whether or not the luminance signal level is larger than a predetermined value, that is, whether or not the image brightness is sufficient. If “YES”, the process proceeds to the next step 103. In step 103, it is determined whether or not the aperture 11 is at the fully open position (maximum aperture). If "NO", the process proceeds to step 105, where the aperture is variably controlled by the aperture 11. If "YES" in step 103, it is determined in step 104 whether the gain of the AGC circuit 18 is 0 dB, and if "YES", in step 105 as in the above. The control of the aperture amount is executed.

On the other hand, if the brightness of the image is insufficient at step 102 (NO), the process also proceeds to step 108 to determine whether or not the aperture 11 is at the fully open position.
If "NO", the state is such that the aperture 11 can be variably controlled, so the process proceeds to step 105. However, if "YES" in step 108, the aperture control cannot be made brighter anymore. From Step 1
At 09, the AGC circuit 18 is activated to increase the gain and amplify the video signal. At the same time, the next step 110
Then, the contour emphasis of the detail circuit 21 is reduced in accordance with the increase in the gain.

The operation state at this time is shown in FIG. 3 (the horizontal axis is the distance to the subject). FIG. 3A shows a video output (luminance signal) when the aperture 11 is variably controlled, and FIG. B) is the aperture opening amount (light output), and as shown in these figures, a constant image output is obtained by controlling the aperture of the aperture 11 in the aperture controllable region, but the distance at which the aperture 11 is fully opened. The further away from X1 (to the right of the graph), the lower the video output and the darker the image (screen). However, in this example, as described above, when the aperture 11 is fully open and the brightness is insufficient, as shown in FIG.
For example, when the distance is X2, the gain is increased from 0 dB to 2 dB, and at the same time, as shown in FIG.
The detail amount is reduced by 2 dB from the default value F.

When the observation distance approaches and the brightness becomes sufficient from the state in which the gain and the amount of detail are controlled as described above, the gain is determined to be “NO” instead of 0 dB by the determination in step 104 in FIG. Therefore, the process proceeds to step 106 to reduce the above-mentioned gain, and at the same time,
In step 107, the detail amount is increased.
That is, assuming that the distance X2 returns to the distance X1 in FIG. 3, the gain is reduced from 2 dB to 0 dB, and the detail amount is increased from (F−2) dB to the default value F.

As described above, by controlling the gain by operating the AGC circuit 18, the video output (luminance signal) becomes constant and the brightness of the image is also maintained constant as shown in FIG. Will be done. Then, the detail circuit 21 reduces the detail amount, that is, the degree of contour emphasis in accordance with the increased gain, so that it is possible to cancel the decrease in the S / N ratio due to the signal amplification. That is, since the noise component appears remarkably in the outline, the appearance of the noise can be prevented by lowering the degree of enhancement of the outline.

In the above-described embodiment, the case where the present invention is applied to an apparatus in which the amount of emitted light is controlled by the stop 11 has been described. It can also be applied.
That is, when the exposure amount is insufficient even when the lamp 10 is driven at a predetermined maximum voltage, it is possible to control to increase the gain and decrease the detail amount at the same time as described above.

[0020]

As described above, according to the present invention,
A light amount control circuit, a gain control circuit, and a detail circuit for contour enhancement are provided. When it is detected that the light output is at the upper limit in a state where the brightness of the image is insufficient, the gain of the image signal is increased, and the gain value is increased. Is controlled in such a manner that the detail amount is reduced in proportion to the increase in the distance, so that an image with good brightness can be obtained even at a long distance without lowering the S / N ratio. There is an advantage that a bright image can be obtained even when the amount of light is small.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an electronic endoscope apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a control operation of the microcomputer according to the embodiment.

FIG. 3 is a graph showing the relationship between operations of the embodiment.

[Description of References] 10 ... lamp, 11 ... aperture, 14 ... aperture control circuit, 15 ... CCD, 18 ... automatic gain control (AGC) circuit, 20 ... digital signal processor (DSP), 21 ... detail (outline emphasis) circuit , 24 ... microcomputer.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H040 BA11 CA10 GA02 4C061 AA00 BB01 CC06 DD00 FF40 HH51 JJ17 LL02 NN01 NN05 QQ09 RR02 RR15 RR17 RR22 SS08 SS30 WW07 5C022 AA09 AB03 AB12 AB20 AC42 AC01 5CB05A03 EB07 EJ04 EJ05 HA12

Claims (1)

[Claims] An imaging device that captures an image of an inside of an object to be observed based on light irradiation from a light source; a light amount control circuit that inputs exposure amount information and variably controls a light output from the light source; A gain control circuit for variably controlling the gain of the image signal; a detail circuit for enhancing the contour of the image signal; and an upper limit value of the light output by the light amount control circuit in a state where the image brightness is insufficient due to the exposure amount information. And a control circuit for controlling the gain control circuit to increase the gain of the image signal by the gain control circuit and to decrease the detail amount of the detail circuit in proportion to the increase of the gain value. Endoscope device.