JPS5860237A - Excessive light quantity detecting-displaying device for mtf measuring apparatus - Google Patents

Abstract

PURPOSE:To obtain an excessive light quantity detecting-displaying device allowing a correct MTF value to be constantly measured, by displaying whether the output signal of a self-scanning solid-state image pickup element is below or above a saturation level. CONSTITUTION:A video signal Video from an amplifier 8 is compared with a predetermined reference voltage VRef in a comparator circuit 13. When the output signal of a charge coupled device 5 is above a saturation output level due to an excessive incident light quantity, the comparator circuit 13 detects this and sets a flip-flop 14. In response to a high-level output of the flip-flop 14, a driver circuit 15 drives an excessive light quantity display 16 constituted by a display lamp such as a light-emitting diode or the like to effect display of the excessive light quantity. Thus, the operator can read only a correct MTF value from an MTF display 12 by checking for whether the MTF value is accurately measured or not through observation on the excessive light quantity display 16.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an MTF σil using a self-setting solid-state image sensor
l constant device σ) Excess light amount detection display device.

Recently, self-traveling solid-state imagers, which do not require mechanical scanning at all and have become electronically scanned, such as charge-coupled sensors and photodimate arrays, have been developed using the MTF measuring device l-4, which increases the speed of VL. , used for the purpose of simplifying operability (I4). To explain this using a charge-coupled device as an example, in a charge-coupled device, as shown in Figure 1, photo elements each having a light-receiving area are arranged in a straight line, and each photo element has a light receiving area. A proportional charge is not stored, and this charge, that is, a potential proportional to the exposure amount is transferred, and the lock pulse φT
They are taken out sequentially.

Figure 2 shows an optical configuration example 1 of an MTF measuring device using a charge imaging element. The slit 2 is illuminated by a lamp 3, and the slit image 2 is formed on a charge imaging element 5 by an imaging lens 4. Here, the charge-coupled device 5 is arranged perpendicularly to the slit image 2', and the light intensity distribution of the slit image 2' is measured by the charge-coupled device 5. The output signal of the charge-coupled device 5 is, for example, electrically Fourier transformed, and the MTF value of the lens 4 to be tested is measured and displayed.

By the way, in a charge-coupled device, the photoelectric conversion signal from each photoelement is proportional to the irradiance and accumulation time of the light irradiated to each photoelement. are shown in Figures 3 and 4. As can be easily understood from this figure, when the output signal of a charge-coupled probe exceeds the saturation output level (not necessarily around the saturation output level), the straightness of the photovoltaic conversion characteristic changes to 69! as shown in Figure 4. When used for measurement, it becomes necessary to adjust either the irradiance or the accumulation time so that the output signal does not exceed the saturation output level.Figure 5 shows the accumulation time tφ in the charge-coupled device. This is a timing chart showing the relationship between the transfer time tT, and when there are N photo elements of a charge-coupled device, the period tφT of the transfer lock pulse φT is expressed as tT = NXtφT.
The transfer clock φ must be generated so that T<tφ. Here, the output signal level of the charge-coupled element is not related to the transfer lock pulse φr [41-] and is proportional to the period LφxVc of the transfer clock φy.

In the above MTF measurement device, if the output signal of the charge coupled device exceeds the saturation output level, the output signal (the waveform shown by the broken line in Figure 6) is 1. Correct MTF ftFL
becomes impossible to measure. In order to correct the stiffness, it is necessary to reduce the luminance of the lamp 3 to reduce the irradiance or shorten the accumulation time so that the output signal of the charge coupled device has the waveform shown by the solid line in Figure 6. Among these methods, the method of reducing the brightness of the lamp 3 is not often used in practice because the spectral radiation distribution of the light source is different and an error in the MTF value occurs.

In general, in an MTF measurement device that measures the MTF value of a camera lens, etc., the irradiance Es in the imaging direction is expressed by the following formula (1), and the lens aperture is F = 1.2 to F = 16.0.
Therefore, the irradiance will change by about two orders of magnitude.

However, t: Lens transmittance #EO: Slit irradiance (μW/Cm), θ: Half angle of view, AE
(θ): aperture efficiency 2m: magnification, F: lens aperture value. For this reason, the absolute value of Es changes by about two orders of magnitude, and when measuring the MTF of a lens with a small F, the output signal level of the charge-coupled probe must be kept below the saturation output level by shortening the accumulation time.

3'7 shows a signal processing circuit in a conventional MTF measuring device, in which the charge-coupled device 5 receives a lock pulse φ7 transferred from a clock generation circuit 6, and simultaneously receives a transfer clock signal from an accumulation time setting circuit 7. φ8 is manually operated to change the light intensity distribution of the slit image 2' and output it in time series. The output signal of the charge-coupled probe 5 is amplified by an amplifier 8, sampled and held by a sample-and-hold circuit 9, and converted into a digital signal by an analog/digital converter 10. This digital signal is Fourier transformed by the Fourier transform circuit 11 to obtain the MTF value of the lens 4 to be tested.
Displayed by F4 display device 12. At this time, the operator manually adjusts the accumulation time setting circuit 7 to match the aperture of the lens 4 to be tested and sets the accumulation time.

However, with this MTF measuring device, the operator cannot determine whether or not the accumulation time is set correctly.

In addition, the accumulation time that has been carefully set may be used, and therefore, the output signal of the charge-coupled device has a portion that reaches the saturation output level, as shown by the broken line in Figure 1.6, and the correct MTF is detected. There were cases where the value was not constant.

In view of these circumstances, the present invention provides an MTF measuring device that uses a self-scanning solid-state image sensor to always provide a correct MTF value by displaying whether the output signal of the self-scanning solid-state image sensor is below the saturation level. An object of the present invention is to provide an excessive light amount detection display device that can measure the amount of light.

The present invention will be described below by way of examples with reference to the drawings.

Figure 8 shows an embodiment of the present invention, and Figures 3 and 9 show its timing chart. In this example! p+1 In the MTF measuring device described above, the video coefficient V from the amplifier 8
i de o is a constant reference voltage "Ref" in the comparator circuit 13.
The output of the comparator circuit 13 becomes high level when the video code exceeds the reference voltage, and becomes low level when it becomes below the reference voltage.

The flip-flop 14 is set at the rising edge of the still level output of the comparison circuit 813 as the human power signal SET, and the output VF is inverted to a high level and continues in this state until the reset input signal Ri=set is input. It has the memory property of retaining. The knob flop 14 may use another storage means.

Here, the #quasi-voltage vRef is set to a voltage level near the saturation output level of the charge-coupled device 5 and at which the photoelectric conversion characteristic has linearity. Therefore, the comparison circuit 13 detects a distortion when the amount of light incident on the charge-coupled device 50 is excessive and its output signal exceeds the saturation output level, and the flip-flop 14'? To set this, the 0 drive circuit 15 drives the excessive light display device 16, which is an indicator lamp such as a light emitting diode imager, using the one level output of the flip frog 14 to produce an excessive amount of light. Therefore, the operator should check whether the MTF value is being measured accurately while looking at the excessive light display [16].
Only correct hiTF values can be read from the display [12].

If the excessive light amount display device t16 lights up and indicates that the amount of light is excessive, the operator presses the reset switch and inputs a reset pulse from the reset pulse generation circuit 17 to the flip-flop 14, thereby turning on the excessive light amount display device F1.
6 is temporarily turned off, the storage time setting circuit 7 is adjusted to reset the storage time of the charge-coupled device 5, and this operation is performed until the light-excess display device 16 turns off when the set switch is not pressed. . By adjusting this accumulation time, the output signal of the charge-coupled device 5 becomes below the saturation output level and the MT
Ffi+! The correct MTF value is displayed on the setting device 12.

Figure 1 shows another embodiment of the present invention, and Figures 1 and 11 show its timing chart. This embodiment f1' is the same as the above-mentioned embodiment by adding an automatic accumulation time adjustment means, and the output signal of the flip-flop 14 is fed back and becomes an input to the accumulation time setting circuit 7a.

The accumulation time setting circuit 7a is a circuit that frequency-divides the clock pulse φ7 from the clock generation circuit 6 to generate a transfer pulse φe.

The accumulation time is set to be short by a predetermined period during which the charge-coupled device 5 is applied, and the accumulation time is adjusted to be short when the output signal of the charge coupled device 5 reaches the saturated output level. On the other hand, the transfer pulse φ8 from the accumulation time setting circuit 7a is converted into a pulse with a predetermined pulse width by the monostable multivibrator 18, and is inputted to the 71 nap-flop 14 as a reset signal Re5et f''14). The output signal vP of 14 appears as a pulse when the output signal of the charge-coupled device 5 exceeds the saturation output level. When this blinking is repeated, the IW of the charge-coupled device 5 automatically shortens according to the above-mentioned path. When the output level becomes below the saturation output level, comparison circuit 1
From 3 onwards, the human power signal will no longer be sent, and the light intensity display device will turn off from 6 onwards. Therefore, the operator should check the excessive light intensity display) (-1' I 6 (7)
(If the MTF value is read from the MTF i display 912, the correct MTF value is determined.

11 Excessive light i′ may be indicated by a buzzer, etc.
Alternatively, this may be done by blinking the MTF value on the MTF display device 12.

As described above, in the MTF measuring device using the self-scanning solid-state image sensor according to the present invention, it is displayed whether the output signal of the self-scanning solid-state image sensor is below the saturation output level, so that the correct MTF is always obtained. It becomes possible to measure the value.

[Brief explanation of the drawing]

Figure 1 is a plan view showing an example of a charge-coupled device, Figure 2 is M
A perspective view showing the optical configuration of the TF measuring device, Figures 3 and 4 are characteristic diagrams showing example characteristics of a charge coupled device, 1.
Figures 5 and 6 are timing charts and output waveform diagrams for explaining the charge-coupled device, and Figure 7 is the conventional Fifr.
A block diagram showing an example of a signal processing circuit in an F measurement device, Figure 8 is a block diagram showing an example of an embodiment of the present invention.
The figure is a timing chart of the same embodiment, Figure 10 is a block diagram showing another embodiment of the present invention, and Figure 1'11 is a timing chart of the same embodiment. 13... Comparison circuit, 14... Flip frog, 1
5... Drive circuit, 16... Light meter excess display device. Agent Kabayama jt4-h

Claims (1)

[Claims] Expert in MTF measurement equipment using self-scanning solid-state image sensors.
and the light '+jj from the self-scanning solid-state image sensor
By comparing the f-converted signal with a predetermined reference voltage,
l11. A comparator circuit that detects excessive light intensity for the i-bi self-scanning solid-state image sensor and an output signal of this comparator circuit.
ill. A #l-excessive light detection and display device, comprising: a memory means for storing data; and a means for displaying an excessive amount of light based on an output signal of the memory means.