Возникли проблемы:
C:\QtApplications\EyeSafetyApp\calibration.cpp:19: error: no matching function for call to 'QObject::connect(QTimer*&, const char*, Calibration* const, const char*)'

в коде:
_timer = new QTimer;
QObject::connect(_timer, SIGNAL(timeout()), this, SLOT(this->onCaptureTriggered()));
_timer->start(10);

Класс:
#ifndef CALIBRATION_H
#define CALIBRATION_H

#include <QTimer>
#include <QObject>
#include <QList>
#include <QString>
#include <QMessageBox>
#include <QFile>
#include <QTextStream>
#include <QSettings>
#include <QErrorMessage>

#include <opencv2/core/core.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/objdetect/objdetect.hpp>

class Calibration
{
public:
Calibration();
double calculateDistance(int HeadSize);
void DrawRectangle();
int headHeight;
~Calibration();
QTimer* _timer;
private:
QCloseEvent* myEvent;
CvCapture* _capture;
IplImage* _img;
QPixmap* _pixmap;

bool flagTocheck;
CvHaarClassifierCascade* _eye_cascade;
CvHaarClassifierCascade* _cascade;
CvMemStorage* _storage;
QList<CvScalar> _colors;

double distance;
int age;

private slots:
void releaseCamera();
void onCaptureTriggered();

};

#endif // CALIBRATION_H