JPH0221838A - Image pickup device - Google Patents

Abstract

PURPOSE:To adjust a portion showing high brightness such as a polyp or ther like to the illumination intensity suitable for image pickup by holding a peak value detected by peak hold means by sample hold means and generating a light control signal. CONSTITUTION:An image of an object portion within an observation visual field including a polyp 65 is formed on CCD 17 and input to a process circuit 23. When a luminance signal Y generated in the circuit 23 is input to a light control signal generating circuit 26, it becomes a signal having a waveform peak V at the polyp portion. The video signal is detected through a buffer 54 by a diode 55, and the detection signal causes a capacitor 57 to be charged with electricity to hold the peak value. In this case, a peak hold pulse Ps is applied from one shot multivibrator 64 to an analog switch 56, so that the analog switch 59 is turned on to charge a capacitor 61 with electricity to reach a peak value. After that, the analog switch 59 is turned off so that the capacitor 61 holds the above peak value. Accordingly, a signal output through a buffer 62 is a light control signal holding the peak value V of an input signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention: 1. Field of the Invention The present invention relates to an imaging device equipped with automatic light control signal generation means.

[Prior Art] In recent years, electronic endoscopes with a built-in solid-state imaging element in the distal end of the endoscope or optical endoscopes with an image guide can be attached to the endoscope, and the observation image of the image guide can be converted into 1iIj image. It is an external video converter system with a built-in video converter that has a built-in solid-state image that converts it into a signal.
(This also falls under the category of electronic endoscopes.) has become widely used.

When the above-mentioned solid-state image sensor is used as an imaging means, it is easy to electrically record the imaged signal or to perform signal processing to make the characteristic of interest more noticeable.

By the way, since the dynamic range of the solid-state image sensing device is about 50 dB, if the observed region deviates from an appropriate illumination level, it tends to become too bright or too dark. For this reason, some devices are equipped with means for controlling the illumination intensity to an appropriate level using automatic light control means. For example, the present applicant
In the publication No. 1-41114, an automatic light control device was proposed.

In this prior example, the automatic dimming signal is calculated by integrating the video signal over one frame period and calculating the average value over one frame period.
A light adjustment signal based on this average value is used to adjust the amount of illumination light to an appropriate level by, for example, controlling the aperture amount of the aperture device.

[Problems to be Solved by the Invention] However, when trying to observe a protruding part such as a polyp using an endoscope, the surroundings are in the distance and the polyp is in the foreground. The amount of light is too high for the polyp you want to see, making it impossible to see it in detail. Therefore, in such a case, there is a drawback in that the light source device must perform dimming correction to adjust the amount of illumination at the tip of the polyp to an appropriate amount.

In addition, in JP-A No. 61-128684, when the illumination intensity during AC lighting changes periodically, a light receiving element detects the time when the illumination intensity in the periodic change reaches a peak,
A conventional example has been disclosed in which image transfer is performed at the time of this peak value. This conventional example is intended to perform imaging without uneven illumination by performing imaging at the peak value, and is useful for setting polyps and the like to an appropriate illumination intensity.

The present invention has been made in view of the above-mentioned points, and therefore provides an imaging device that can illuminate with appropriate brightness even a region such as a protruding region of a polyp, which is observed at a higher brightness than surrounding regions, and can be observed accurately. The purpose is to cover.

Means and Effects for Solving Problems 1 The present invention includes a peak hold means for detecting a peak value within a predetermined period of time such as one field for an input signal, and a sample hold means for detecting the peak value detected by the peak hold means. The sample and hold means that outputs the peak hold and sample and hold pulses to both of these means form the dimming signal generation means.

However, since the peak value detected by the peak hold means is held by the sample hold means to generate the dimming signal, it is possible to image a region such as a polyp that exhibits higher brightness than the surrounding area. The illumination intensity can be adjusted to an appropriate level, allowing detailed observation of areas such as polyps.

[Example] Hereinafter, the present invention will be specifically explained with reference to the drawings.

FIGS. 1 to 5 relate to the first embodiment of the present invention.
The figure is a block diagram of a dimming signal generation circuit in the first embodiment, FIG. 2 is an overall block diagram of the first embodiment, FIG. 3 is a schematic block diagram of an electronic scope, and FIG. 4 is a signal processing device and A configuration diagram of the light source device, and FIG. 5 is a waveform diagram for explaining the operation of the first embodiment.

As shown in FIG. 2, the image carrier 1 of the first embodiment includes an electronic endoscope (hereinafter also referred to as an electronic scope) equipped with an imaging means.
) 2, a light source device 3 that supplies illumination light to the electronic scope 2, a signal processing bag @4 that performs signal processing for the electronic scope 2, and displays the video signal output from the signal processing device 4 in color. It is composed of a monitor 5.

The electronic scope 2 has an elongated insertion section 6 that can be inserted into a body cavity, etc., and a large operation section 7 is formed at the rear end of the insertion section 6, and an angle knob provided on this operation section 7. By rotating the insertion portion 8, the curved portion 9 formed near the tip of the insertion portion 6 can be bent vertically or horizontally.

A light guide 11 is inserted into the insertion section 6 as shown in FIG. 3, and this light guide 11 is further inserted into a light guide cable 12 extending from the operation section 7. A light source connector 13 is attached to the end of the light source 12 so that it can be connected to a connector receiver 14 of the light source device 3. By connecting this light source connector 13 to the light source connector receiver 14,
Illumination light is supplied to the incident end face of the light guide 11, and this illumination light is transmitted from the output end face to the light distribution lens 1.
5, it is expanded and irradiated onto the subject side.

An object illuminated by the illumination light that has passed through the light distribution lens 15 is imaged by an objective lens 16 attached to the distal end of the insertion section 6 on a CCD 17 serving as an SID disposed at its focal plane. A color separation mosaic filter 18 is attached to the imaging surface of this CCD 17, and colors are separated for each pixel.

By connecting the signal connector 19 in the electronic scope 2 to the signal connector receiver 21 of the signal processing device 4, as shown in FIG.
A drive signal from the drive circuit 22 is applied to the CCD 17, and the photoelectrically converted signal is read out and input to the process circuit 23.

The process circuit 23 generates a luminance signal Y and color difference signals R-Y and B-Y, which are input to the encoder 24. The brightness signal Y is also input to the dimming signal generation circuit 25, which detects the peak value of the brightness signal Y in one field period to generate a dimming signal, and the light source device 3
is input.

The light source device 3 includes a lamp 27 that emits white light using electric power supplied from a light source power source 26, and a lamp 27 that emits white light using electric power supplied from a light source power source 26.
A concave mirror 28 that outputs the white light of No. 7 as a parallel light beam, an aperture device 29 interposed in the middle of the parallel light beam, and a condenser lens 31 that condenses the illumination light focused by the aperture device 29.
and an aperture control circuit 32 for the aperture device 29.

The aperture device 29 includes aperture blades 33 provided with notches,
The aperture motor 34 rotates the aperture blades 33. Depending on the amount of rotation of the aperture blades 33, the amount of illumination light blocked can be changed to control the amount of illumination light to the light guide 11. The diaphragm motor 34 is configured to have its rotation angle changed in accordance with the level of the dimming signal by an aperture control circuit (motor drive circuit) 32 to which the dimming signal is input, thereby enabling dimming.

By the way, the process circuit 23 has a configuration shown in FIG. 4. The input signal passes through a brightness signal processing circuit 41 to generate a brightness signal Y. The color difference signal R-Y is also input to the color signal reproduction circuit 42.

B-Y is generated chronologically for each horizontal line, and the white balance circuit 43 performs white balance compensation.
One is input directly to the analog switch 44, and the other is inputted to the analog switch 46 after being delayed by one horizontal line by the one-day delay line 45, and the synchronized color difference signals R-Y, B-
Y is obtained.

Note that the timing generator 47 is connected to the drive circuit 22.
Then, a timing signal is sent to the synchronization signal generation circuit 48 to generate a drive signal and a synchronization signal at a predetermined timing. Further, the synchronization signal generation circuit 48 outputs a synchronization signal to the encoder 24 and also outputs a synchronization signal to the dimming signal generation circuit 2.
The vertical direction 1[1] signal VD is also output to the signal line 6.

A specific configuration of the dimming signal generation circuit 26 is shown in FIG.

This dimming signal generation circuit 26 receives an input video signal (
In this case, a peak hold unit 51 detects the peak value of a luminance signal), a sample hold unit 52 samples and holds the detected peak value, and pulses are provided to these peak hold unit 51 and sample hold unit 52 for peak hold and sample hold. and a control pulse generation section 53 that outputs.

The video signal is inputted to a peak detection diode 55 and a first analog switch 56 via a buffer 54. This diode 55 is connected in parallel with the input and output terminals of an analog switch 56. The cathode of this diode 55 is grounded via a peak hold capacitor 57 and is also input via a buffer 58 to a second analog switch 59 forming the sample hold section 52 . Note that the buffer 58 is provided to increase the input impedance so as not to lower the voltage of the capacitor 57.

The output end of this analog switch 59 is grounded via a sample and hold capacitor 61, and is outputted as a dimming signal via a buffer 762.

At the control end of the second analog switch 59, there is a first one-shot multivibrator (hereinafter abbreviated as one-shot multi) 6 that forms the control pulse generation section 53.
The sample hold pulse Ps from the second one-shot multi 64 is applied to the control end of the first analog switch 56, and the peak hold pulse Pp from the second one-shot multi 64 is applied to the control end of the first analog switch 56. Note that the first one-shot multi 63 generates a sample-and-hold pulse PS based on the input vertical synchronizing signal VD, and the second one-shot multi 64 uses this sample-and-hold pulse Ps to generate a sample and hold pulse PS following this pulse ps. [Generate peak hold pulse pp].

When the peak hold pulse Pa is applied from the one-shot multi 64, the first analog switch 56
The input and output terminals become conductive, and the peak value held in the capacitor 57 is discharged and lowered. This pulse P
The analog switch 56 is turned off until the next pulse Pp is applied after p is no longer applied, and the signal peak-detected by the diode 55 is held in the capacitor 57. In addition, the second analog switch 5
9 is also turned on between its input and output terminals by the sample bold pulse ps from the one-shot multi 63, and the capacitor 61 is charged to the peak level held by the capacitor 57 via the buffer 58, and after this pulse p3 is applied, maintains its peak value until the next pulse ps.

The operation of the first embodiment configured as described above will be explained below.

The insertion section 6 of the electronic scope 2 is inserted into the living body, and, for example, a polyp 65 (see FIG. 2) generated on the inner wall of the tube is observed.

The object region within the observation field including the illuminated polyp 65 is imaged on the CCD 17, read out by application of a drive signal, and input to the process circuit 23. The luminance signal Y generated by this process circuit 23 is
The signal is input to the dimming signal generation circuit 26 shown in the figure. Video signal (luminance signal) input to this dimming signal generation circuit 26
For example, as shown in FIG. 5(a), Y has a waveform with a peak V at the polyp portion. This video signal Y] passes through a buffer 54 and is detected by a diode 55.
The detected signal charges the capacitor 57 and holds the peak value. In this case, the peak hold pulse ps is applied to the first analog switch 56 from the second one-shot multi 64 as shown in FIG. 5(b), and the next pulse ps is applied after this pulse s. The peak value of the input signal is held in the capacitor 57 until it is applied. Therefore, the voltage waveform of the capacitor 57 or the voltage waveform of the voltage of the capacitor 57 passed through the buffer 58 is as shown in FIG. 5(C).

In other words, if there is a peak value, the waveform will hold the peak value of is turned on,
The capacitor 61 is charged via this analog switch 59 and reaches this peak value, after which the analog switch 59
9 is turned off and capacitor 61 holds this peak value.

Therefore, the signal outputted through the buffer 62 becomes a dimming signal that maintains the peak value ■ of the input signal, as shown in FIG. 5(e).

This dimming signal is input to the aperture control circuit 32 in the light source device 4 as shown in FIG. The amount of illumination light is adjusted by blocking the light. With this adjustment, the illumination for the brightest part of J3 within the observation field, in this case the polyp 65, is automatically dimmed to the overcharge level.

Therefore, according to the first embodiment, it is possible to automatically set an appropriate illumination intensity for a region such as Poly-165, which is observed at a brightness significantly different from the surrounding area, without manual adjustment. For this reason, a ml image of a site such as the polyp 65 can be obtained under desirable illumination conditions, and this transferred image allows for detailed observation, making it easier to make an accurate diagnosis.

1, another feature of this embodiment is that the peak hold section 51 has a configuration different from that of a normal peak hold circuit in which an analog switch 56 and a capacitor 57 are connected in parallel.

In a normal peak hold circuit configuration, when the analog switch connected in parallel with the capacitor is turned on, the peak value held in the capacitor becomes completely O [V], so the response until reaching the peak value is long. There is a drawback.

In other words, by adopting the configuration of the first embodiment shown in FIG. 1, the responsiveness of peak hold is improved.

Note that the vertical synchronization signal VD is used as the peak hold pulse Pp.
You may also use

FIG. 6 shows a dimming signal generation circuit 71 according to a second embodiment of the present invention. Generation unit 53
In this example, a control pulse generating section 73 is provided with a frequency divider 72 that divides the frequency of the vertical synchronizing signal VD into 1/2. The rest of the structure is the same as that shown in FIG.

By providing the frequency divider 72, when one frame has a two-field configuration, for example, when the two fields have different peak values as shown in FIG. 7(a), the first embodiment can be used. Then, the dimming signal has steps as shown in Fig. Ia1 (b). This signal may cause hunting if the response of the aperture control system is fast. On the other hand, in this second embodiment, the frequency is divided by 1/2 by the frequency divider 72, so that the dimming signal is generated only in one of the two fields, so that As shown, a dimming signal without steps can be generated.

FIG. 8 shows the main parts of a third embodiment of the present invention.

In the first embodiment, the dimming signal was generated using the r@ degree signal Y, but in this embodiment, the dimming signal is generated from the composite video signal C⊛ passed through the encoder 24 through the dimming signal generation circuit 81. A signal processing device 82 is used which generates the signal and outputs it to the aperture control circuit 32 of the light source device 3.

Further, the dimming signal generation circuit 81 of this embodiment has means for switching between detection based on peak value and detection based on APL (average image level), as shown in FIG. Subcarriers are removed from the composite video signal C2 by a low-pass filter 83, and the signal is input to the peak hold circuit 51, and is applied to the C capacitor 86 via an analog switch 85 which is turned on and off by a switch 84.

The low-pass filter 83 is composed of, for example, a resistor R1 and a capacitor C1, and is set to a cutoff frequency lower than that of the subcarrier. Also, the capacitance fi (assumed to be C) of the capacitor 86 is the same as that of the peak hold capacitor 57.
If the resistance R1 is larger than the time constant, for example, 1
It is set to output the average value in the V (vertical) period. (In addition, each time C of this capacitor 86 is a capacitor C
C>>01) The analog switch 85 is normally in an OFF state because the switching signal is "L" due to the pull-down resistor 87.

In this off state, subcarriers are removed from the composite video signal C2 by the low-pass filter 83, and the signal is input to the peak hold section 51. Therefore, in this case, the signal input to the peak hold section 51 becomes the video signal a as shown in FIG. The peak detection operation is performed in the same manner as (see FIG. 10(b) to (f>)).

On the other hand, the switch 84 is turned on, and the analog switch 85
When turned on, the averaging capacitor 86 produces a signal that is averaged over a period of 1V as shown on the right side of FIG.
is input.

For this averaged signal, the peak hold section 51 holds the peak value, the sample hold section 52 samples and holds the peak value, and from this sample hold section 52, the averaged signal is The peak value of the measured values is output as a dimming signal. The rest of the structure is the same as that of the first embodiment.

According to the third embodiment, dimming can be performed either by a peak value or by an averaged peak value (that is, APL).

Therefore, when observing a protruding part such as a polyp, you can observe the part with the appropriate brightness by adjusting the light at the peak value, and it is possible to observe the part with the appropriate brightness, rather than a protruding part such as a polyp. When attempting to observe a site with almost unchanged initial symptoms, the area can be observed with appropriate brightness by adjusting the light using APL.

FIG. 11 shows a modification of the third embodiment of the invention.

In the third embodiment, the switch 84 serving as a switching means for peak value detection and APL detection is provided in the signal processing bag M82, but in this modification, this switch 84 is provided in, for example, the operating section 7 of the electronic scope 2. It is. The rest of the structure is the same as that of the third embodiment. This modification improves operability.

FIG. 12 shows a fourth embodiment of the invention.

In this embodiment, a dimming signal is generated by a dimming signal generating circuit 91 from a composite video signal CV outputted from a signal processing device 4' having no dimming signal generating means, and a dimming signal is generated by a light source device 3.
It is used to output light to perform dimming.

For this reason, this dimming signal generation circuit 91 is provided with a vertical synchronization separation circuit 92 for extracting the vertical synchronization signal VD from the composite video signal C2 to form a control pulse main generating section 93.

Further, a foot switch 94 is pulled out as a switch for turning on/off the analog switch 85.

Note that the composite video signal CV output from the encoder 24
One side is connected to the color monitor via the branch connector 95,
The other side is manually input to this dimming signal generation circuit 91.

The rest of the structure is the same as that of the third embodiment.

This embodiment has the advantage that the existing signal processing device 4' can be used to perform dimming at either the peak value or the average value.

In each of the above embodiments, an electronic scope is used, but as shown in FIG. 13, an external television camera in which a television camera 102 is attached to a fiber scope 101 can also be used as a scope 103.

The fiberscope 101 has an image guide 1, not a CCD 17, on the focal plane of the objective lens 16 shown in FIG.
04 is arranged, and this image guide 104
The optical image is transmitted to the eyepiece section 105 side where the output end surface is disposed. Opposite this exit end surface, an eyepiece lens 10
A television camera 102 is provided in the eyepiece section 105 so that observation can be made with the naked eye through this eyepiece lens 106.
By attaching the
The image is formed on the imaging surface of D108. Note that a color separation mosaic filter 109 is provided in front of this imaging surface. This C0D 108 is connected to the signal processing device 4 shown in FIG. 4 via a signal cable, and the signal is processed in the same way as when the electronic scope 2 is connected.

Although each of the above-mentioned embodiments has been described in the case of an image carrier such as an electronic scope or a television camera 102 having a built-in color filter, the present invention can also be applied to a frame-sequential type device shown in FIG. .

The CCD 17 built into the electronic scope 111 is connected to the frame sequential signal processing device 113 via a cable, and
The entrance end face of the light guide 11 of this electronic scope 111 is connected to a field-sequential light source device 115.

In the light source device 115, a rotating color filter 117 rotated by a motor 116 is disposed between the aperture blades 41 and the condenser lens 31 in the light source device 3 shown in FIG.

Therefore, the white light from the lamp 27 is transmitted through fan-shaped color filters 118R and 118G attached to the rotating color filter 117.
.

The electronic scope 111 has the same configuration as the electronic scope 2 shown in FIG. 3 without the mosaic filter 18 in front of the CCD 17.

A drive signal is applied to the CCD 17 from a drive circuit 121. The signal read from the CC017 is amplified by the amplifier 122r, converted to digital data by the A/D converter 123, and sent to the R, G, and B frame memories 1 via the multiplexer 124.
The data is sequentially written to 25R, 125G, and 125B. When the signal data for one frame is stored in each of the frame memories 125R, 125G, and 125B, they are simultaneously read out and converted into analog color signals by the D/A converter 126, respectively. Thereafter, the matrix circuit 127 converts the signals into a luminance signal Y and color difference signals R-Y and B-Y, which are then input to an NTSG encoder 128, converted into a composite video signal @CV, and outputted to the color monitor side.

The luminance signal Y is inputted to, for example, the dimming signal generation circuit 26 shown in FIG. 1, and this dimming signal is inputted to the aperture control circuit 32 in the light source device 115.

Furthermore, a rotating color filter 117 is provided in the light source device 115.
For example, the rotational position of each color filter 118R.

A sensor 131 is provided to detect the end period of the illumination light passing through 118G and 118B, and a detection signal from this sensor 131 is input to a timing generator 132.

Therefore, this timing generator 132 outputs a control signal to start reading to the drive circuit 121 in synchronization with the timing of the end of illumination. Also, for the synchronization signal generation circuit 133, this timing generator 13
The timing generator 132 generates horizontal and vertical synchronization signals HD and VD that are synchronized with the signals No. 2 and 132, and further outputs a control signal to the motor servo circuit 134 so that the motor 116 has a constant rotational speed.

This embodiment has almost the same effects as the first embodiment.

This embodiment can also be applied to an apparatus using a frame-sequential television camera instead of the frame-sequential electronic scope 111.

FIG. 15 shows a modification of the fifth embodiment.

That is, an AGC circuit 122' is used in place of the amplifier 122 in FIG.
2- Signal processing device 1 capable of controlling the gain of
I set it to 13'.

The AGC circuit 122- is set to a gain corresponding to the voltage applied via the variable resistor VR when the switch 141 is turned on at contact a. Yes, when the contact is turned on, its gain is automatically controlled by the dimming signal. In general, the AGC circuit 122' has a faster response than the aperture device 29, so when controlling the illumination light amount using the peak value,
First, the AGC circuit 122' operates to reduce its gain, and if it is still too bright, the aperture side further reduces the amount of illumination light. Therefore, according to this modification, S
/N good images may be obtained in some cases.

Note that different embodiments may be constructed by partially combining the above embodiments.

In addition, when using the field sequential formula, for example, apply J as follows.
You can also

For example, when generating a dimming signal based on R, G, and B signals conveyed under RoG and B illumination using an R, G, and B rotation filter, for example, in FIG. R, G instead of synchronizing signal VD.

The timing signal (or switching signal) for switching each frame of the B signal and writing it into the memory is not a 1/2 frequency divider 72,
For example, the peak of the G signal or the peak of the R signal may be detected to generate the dimming signal through a frequency divider that divides the frequency by 1/3.

In addition, the peak values of the R, G, and B signals are calculated using three peak hold sections, and after adding them together in addition 03, they are held in the sample hold section and adjusted based on the other peak values for the luminance signal or white signal. An optical signal may also be generated.

In the embodiment shown in FIG. 9, a capacitor 86 for APL is provided before the peak hold section 51 via an analog switch 85, but an average value detection circuit is provided in parallel with the peak hold section 51, and the switch It may be possible to make it switchable.

[Effects of the Invention] As described above, according to the present invention, since the automatic dimming signal is generated by providing the peak value waveform means, it is possible to observe even parts showing high brightness such as polyps. Lighting intensity can be set easily.

[Brief explanation of the drawing]

FIGS. 1 to 5 relate to the first embodiment of the present invention.
The figure is a block diagram of a dimming signal generation circuit in the first embodiment, FIG. 2 is an overall block diagram of the first embodiment, FIG. 3 is a schematic block diagram of an electronic scope, and FIG. 4 is a signal processing device and A configuration diagram of the light source device, FIG. 5 is a waveform diagram for explaining the operation of the first embodiment, FIG. 6 is a configuration diagram of the dimming signal generation circuit in the second embodiment of the present invention, and FIG. 7 is a diagram of the second embodiment. Waveform diagrams for explaining the operation of the embodiment/FIGS. 8 to 10 relate to the third embodiment of the present invention, and FIG. 8 is a block diagram showing the main part of the third embodiment,
FIG. 9 is a circuit diagram showing the configuration of the dimming signal generation circuit in the third embodiment, FIG. 10 is a waveform diagram for explaining the operation of the third embodiment, and FIG. 11 is a modification of the third embodiment. 12 is a block diagram showing the configuration of a dimming signal generation circuit in the fourth embodiment of the present invention; FIG. 13 is a block diagram showing the configuration of a television camera according to a modification of the first embodiment; FIG. FIG. 14 is a configuration diagram of a signal processing device and a light source device in a fifth embodiment of the present invention, and FIG. 15 is a configuration diagram of a signal processing device and a light source device in a modification of the fifth embodiment. 23...Process circuit 26...''Dimming signal generation circuit 27...Lamp 51...Peak hold section 52...Sample hold section 53...Two control pulse generation sections...Aperture device 1... Imaging device 2... Electronic scope 3.
...Light source device 4...Signal, processing device 5...
・Monitor 17...CGD Figure 1 Figure 5 Figure 3 Figure 6 Figure (bl 0---1----------(C) So-called nine wounds

Claims (1)

[Claims] In an imaging device that has a means for illuminating a subject and outputs a video signal by output from an image sensor, a sample-and-hold pulse is generated based on a synchronization signal that generates a video signal, and a sample-and-hold pulse is generated following this sample-and-hold pulse. a peak hold pulse, a first holding means for holding the peak value of the video signal due to the peak hold pulse, and a first holding means for holding the output of the first holding means due to the peak hold pulse. An imaging device comprising: second holding means; and means for controlling the amount of illumination light from the illumination means in accordance with the output of the second holding means.